ATTENTION: We recommend you DO NOT DISASSEMBLE or ATTEMPT TO REPAIR OR
REPLACE ANY PARTS ON ANY ELECTRONIC / ELECTRICAL DEVICE without proper,
technical training and repairs / modifications should always be left to
qualified technicians.
"WARNING: PLEASE
USE CAUTION WITH ANY ELECTRICAL DEVICE. ANY REPAIR AND / OR RESTORATION
SHOULD BE UNDERTAKEN ONLY BY A QUALIFIED TECHNICIAN. DO NOT OPEN OR ATTEMPT
TO REPAIR ANY ELECTRONIC DEVICE WITHOUT PROPER INSTRUCTION, EXPERIENCE,
BACKGROUND, TRAINING OR KNOWLEDGE, OR TAKING PROPER SAFETY PRECAUTIONS.
THERE ARE NO 'USER SERVICEABLE' PARTS, SYSTEMS OR CIRCUITS INSIDE.
POTENTIALLY HARMFUL, INJURIOUS AND / OR LETHAL ELECTRIC VOLTAGE AND CURRENT
INSIDE.
IT CAN KILL YOU AND WILL HURT THE ENTIRE TIME YOU ARE DYING."
The following information is for
'entertainment value' ONLY and not intended as 'how to' / DIY instructions,
and by NO MEANS is it instruction on how to repair, nor intended as
incentive nor encouragement to tackle any electronic repairs yourself!
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We will be adding MANY notes / info as we go
thru old 'work sheets', as time allows
and repairs are completed...
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a/d/s L910 Speakers. LED "Level / Power Meters' intermittent / dim. We discovered compromised /
fatigued 'legs' on the first and second LED's. The first LED appeared to
have been 're-flowed' with solder at some time. The 'second up' LED had one
leg 'severed' by fatigue, but was intermittently making connection, which
then allowed the remainder of the LED's to fire at full brightness. We added
a short section of wire as a 'scab' (soldered on the full length) to
'bridge' the fatigued section. We re-flowed a few others proactively, and
inspected the meters in the other as well.
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a/d/s L910 Speakers. Extraneous 'rattles' from crossover assembly. While there had been a bit of
'hot glue' applied at the factory, it was insufficient to squelch all the
'rattles' that showed up on our AF generator sweep. Adding hot glue to the
components to secure / 'pad' them to each other and /or the circuit board
eliminated the rattles (don't forget the 'wire' clip that holds the LED
meter circuit card perpendicular to the main circuit board. Simply 'coat' it
with hot glue and put glue between it and the LED circuit board junction).
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Akai GX-60R Cassette Deck.
Transport switches 'randomly' from forward to reverse. The transport
buttons must be completely 'free' in their openings of the front bezel,
with no 'side' pressure. There is a mounting plate behind the face
plate, and it as well as the face plate, must be aligned 'perfectly'
with no 'side pressure' on the switches. Once aligned, fasteners should
hold everything in position. If the face plate shifts, relative to the
chassis (such as in shipping / transit), the transport can 'mis-behave'
again.
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Akai X-1800SD (THREE TYPES:
A-Type, B-Type & C-Type).
There were three different versions (internally) of the Akai X-1800SD
Reel to reel / 8-track cartridge tape deck. Some of the circuit boards
are interchangeable from A-Type to B-Type or B-Type to C-Type, but never
from A-Type to C-Type. Other parts such as some of the cosmetic parts,
tape counters & output transistors will vary as well. The "Type-C" has a
PB/REC amp (lower section) that is MUCH easier to work on from an aspect
of cleaning the controls, and adjusting the internal levels. Also, some
of the parts are interchangeable with the Akai X-1810 (very similar deck
both externally and internally. The Type-C and the X-1810 both utilize
the same amplifier output transistors; 2SC1060 X 4)
Other various differences in the Types A, B & C;
Type-A has a 'large' bezel on the tape counter that is 'convex' to the
front panel, and requires a larger opening in the face panel.
Type-C features the addition of a selector for 'Auto-Stop' or
'Continuous Play' for the 8-Track cartridge. Switch is located near the
'cartridge insert' opening on the side.
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Akai X-1800SD.
We had one that had one of the VU level meters exhibiting a reduced
level by about 12 dB. There's not separate 'meter level' adjustment
built into the deck so nothing to do there. We substituted 2 other of
the same / OEM meters in it's place with the same results. The actual
Input and Output level was showing the same on our mV meter and our dual
track O-scope so we knew it was isolated to the meter. We isolated the
section on the schematic and found the circuit was a capacitor, 2x
diodes and 2x resistors. The Diodes checked fine as did the resistors.
We had another 'non-polar', 25V / 3.3mF cap of the same value in stock
and once it was replaced, the meter worked perfectly in unison with the
other.
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Akai X-1810.
We had one very intermittent auto-reverse on at least one (actually most
all of them will exhibit some sort of intermittency with their
Auto-Reverse at this point, 45+ years on). The 'manual reverse /
direction change' switches will certainly need to be disassembled and
cleaned (silver plated), but there are other possible causes. One needed
the associated relay dismantled and it's contacts burnished (we actually
do that on all of them now). There's also a Hitachi transistor,
"2SC458", that is know for developing 'black legs' that compromise
internal integrity that usually needs to be changed. The last one we had
the issue with we couldn't solve the issue till after changing all the
transistors on the board (which didn't improve it so we changed them
back to the originals). We finally deduced that the issue was an
intermittent, reed / micro-switch in the 8-Track cartridge slot that is
there to prevent someone manually changing directions with an 8-Track
tape inserted or a reel tape being left in play (while the 8-track
cartridge is playing) and it 'auto-reversing' due to sensing tape being
installed. We couldn't really disassemble the switch for repair, and
didn't have any direct replacements immediately in stock, nor other
'parts' X-1810's' at the time, but we did figure out that the same
switch is used for a slightly different purpose in the Akai X-1800 (at
least the C-Type) and we had one or two of those for parts. Changing the
switch solved the problem, but we still changed out the 'black legged'
Hitachi 2SC458 transistor.
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GAF
8MM Film Projectors, such as; 2588, Wards 811, etc.
These projectors are quite 'Rube Goldbery' inside. There's a lot of
wheels, pulleys, Figure-8 twisted belts, and combinations of 'turning /
spinning' things, moving in all kinds of directions, many of which
depend on minute adjustments one direction or another to run correctly.
One such mechanism that is particularly critical to running correctly,
is immediately off the motor. Most of this series have a fairly small,
but thick "O-Ring" that goes from the motor pulley, to the first
'Aluminum' pulley that also drives the Tilton 'Rubberized Cloth' belt
and another, larger o-ring. One issue is that the projector can start
off running slow, then speed up, then slow down again. Or, the motor can
'jam' up completely and stop running (or all of those things). When
replacing the first 'drive' belt, it's overall length is critically
important. Also, the aluminum, 'combination' pulley (about 1" in
diameter), will need to be removed, have it's bushing cleaned and
re-lubed (30wt oil works great instead of 'fine machine' oil on that
one). There's an 1/4 head screw to adjust the 'transmission' (you'll
likely need a service manual to identify the "transmission") and there's
like a VERY SMALL 'sweet spot' along it's adjusting slot where all of
the functions will work reliably (will likely be trial and error to get
it working correctly each and every time and over time). Even once all
of that is done, there may be the occasional time that a belt 'jumps'
off a pulley, and functions such as Fast Forward and Re-Wind may still
be sluggish (use your finger to 'help' them along), especially with the
film still threaded thru the film track (although the 'Fast Wind' issues
are not related to any of the mechanism mentioned above, they're just
common).
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KENWOOD BASIC C2 PRE-AMP
While the Basic C2 is a good
sounding pre-amp, chocked full of features, it does have a couple of
issues. Both are due to the utilization of very 'fragile / anemic'
potentiometers to control balance and headphone level.
1)
Balance Control Issue. This usually manifests itself by having one
channel being dropped out. I suppose you could have both channels out.
Generally one or two channels 'down' would not be indicative of an issue
with the "balance control", except with the Kenwood C2.
Unfortunately, there does not seem to be, at least of this writing, a
direct replacement for this potentiometer. There are a couple of 'photo
essay' / writings out there on the web about re-building the pot, but
this is 'micro-surgery' and the potentiometer is not meant to be taken
apart. As most folks will never move the balance control from 'dead
center' you can simply use two small 'jumpers' to bridge across the pot
(obviously you'll need to deduce which solder joints to jumper, and we
haven't taken photos yet of our process to post). There is one page that
writes extensively about substituting 180k resistors, but not sure why
that's being instructed as the pot is in a "zero Ohms" position when
each channel is on at full volume (control centered), and only at the
180k on the side that is 'balanced away from'. For us, the jumpers work
perfectly.
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2) Headphone Control Issue.
Again, 'crappy' potentiometer. Again, jumpers took care of this issue.
The volume still follows the 'main volume' control anyway. What the
separate level control would allow you to do is attenuate it down from
the main volume level. Not sure that this would ever be used in a 'real
world' situation, so seems like an 'excusable' workaround as well....We
did have one unit that not only had a bad level pot, but also had 2-3
extra 'cloned' signals riding on the main signal on one channel. We
traced it to the headphone level board. As the 'headphone' amp is a
fairly 'fringe' feature, we didn't pursue it far enough to rectify.
Sorry.
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KENWOOD KA-6000. Unit exhibited
a slow (about 2 per second) 'pulsing' of woofers from both sides once
'warmed up' (we had to get if fairly hot before it would have the issue.
In fact, with it's sheet metal cover off it wouldn't get hot enough, so
we had to utilize a heat gun to warm up the transistors alternating with
'freeze spray' to determine which transistor was causing
the issue). We discovered that it was one of the Hitachi "2SC458" transistors on
the driver board that was causing the pulsing (and it was exhibiting a
symptom called 'black legs' which is pretty well known to be an issue
with most Hitachi 2SC458 transistors out there). Even though it was an
issue on one channel, it did the same pulsing from both sides into any
speakers' woofer that was connected (probably pulling on the power
supply hard enough to effect the other side, but we didn't investigate
that). Just replaced ALL the 2SC458's as well as all the 2SC871
transistors (which also had black legs) with new, KSC1815 transistors
and NTE85's,
and the problem was fixed (pretty much all the TO-92 cased / epoxy
transistors were exhibiting a symptom called 'black legs' . We then warmed it back up with the heat gun,
and it would not 'pulse' anymore. Yea!
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KENWOOD
KR-4200 receiver. Unit exhibited 60Hz hum in R channel and excessive
'hiss' on the L channel. While the hiss remained constant, hum would
increase slightly after a few minutes of warm-up. We narrowed it down to one
of the 2SC1345 transistors by using 'freeze spray' alternating with a heat
gun as the culprit. The transistor that would allow the 'hum' would improve
with freeze spray, until it got too cold, then would start to hiss as well,
then when chilled further would cease to function until it warmed. The L
channel would simply 'improve' when chilled. We verified these transistors
as the culprits by 'swapping' them. The symptoms then switched channels.
(prior to those tests, we had checked EVERY electrolytic in the power supply
and driver boards to no avail). Replaced both 2SC1345 transistors and
noise problem solved. Next issue was then that the DC was creeping up and
triggering the DC Protection Relay to as high as 3 Volts! Changing the other
pair of 2SC1345 transistors in the signal chain rectified that.
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KENWOOD KR-9940
/ 9340 quad receiver and Other Kenwoods.
1) Speaker 'B' will not function unless you already have
'Speaker-A' loaded.
2) Power switch on the Kenwood KR-9940 is interesting.
It's a 'push' button, with a neon lamp inside that act's as a kind of 'night
light' / 'locate it in the dark' light. The neon light is 'ON' when the unit
is OFF and visa-versa. It's identified as an 'R13-21' and while there are
references out there on the web, it does not appear as 'obtainable' for
replacement. We managed to 'rebuild' one (not generally what you're supposed
to do). There's a 'tapered plunger on a spring internally. The switch was
intermittent. We found that the 'base / flange' on the plastic plunger was
worn 'crooked', so we used a file to even it out (thus making it thinner)
and added a small shim to make up the difference (assuming it needed the
extra thickness). Once re-assembled, the switch was no longer intermittent
and functioned ON and OFF as it should.
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KENWOOD KR-NINE-G, 9000, 10000,
ELEVEN-G etc.
This series of Kenwood receivers offered a 'Timer'
function / feature to function as a 'sleep timer'. It is essentially a
standard clock works / 'kitchen' timer mechanism. It operated from a knob on
the front panel on the left end of the unit. The knob extended to an
aluminum shaft. The 'timer' body also had an aluminum shaft protruding. The
two aluminum shafts met at a 'center point' and were coupled with a plastic
or nylon sleeve with 2 to 4 set screws. The knob takes a fair amount of
effort to turn the clock works, as you're at a mechanical 'dis-advantage'
due to the clock gearing. Typically the 35+ year old plastic sleeve cannot
withstand that type of force anymore and cracks, rendering not only the
timer useless, but if the unit did not end up in the 'Reset' position,
useless as well. The 'work-around' is to put the unit in it's 'Reset'
position and then disengage the locking sleeve so it can't be put back into
'timer' mode. If the sleeve is already cracked or broken (and it likely will
be) use a pair of pliers to rotate the rear most aluminum shaft, put the
unit into it's 'Reset' position and loosen the set screws. We do this to all
of this series, whether the timer still functions or not, as it's not a
matter of 'if' it will break, but 'when'.
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Marantz 5220 Cassette Deck
(likely also applicable to Marantz 5020, 5120, 5200, 5400, 5420
and possibly others.
Excessive WOW / Flutter. We've found that the 'belt
kits' sold by some ebay sellers are 'wrong' for this deck. While it is
perfectly permissible to utilize 'round' belts in many tape decks, it is
NOT permissible in the Marantz 5220. You MUST use 'SQUARE' belts. The
only reason we can deduce is that the round belt cyclically 'rode' up on
the edges of the 'idler' pulley, causing the anomaly.
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Marshall JCM-800 Guitar amp head
Marshall JCM800 was blowing the 'HT' fuse (it's been a
while, but I believe it was the 'heater' fuse. Could have been the main)
when level was raised much above about '9 o'clock' on the 'Master' volume
unless output tubes #1 and #2 were removed. There was evidence of 'arching'
between pins #1 & #2 on the first output tube. It had the issue when we
acquired it, and from the 'carbon track' burned into the 'bakelite' tube
socket, it looked like it had been going on for quite some time. We tried
removing the carbon track with a wire brush, but while it did allow the
volume to be increased some, it still arc'd and would blow the fuse. We
ordered some ceramic tube sockets, and replaced the bad one (need to do them
all some day, but it's a 'bit of a job'). No more issues, and we can now
'crank it to Eleven'! Just FYI, the AC current draw at idle on our Marshall
JCM-800 without the tubes was .05A and with the tube installed = .43A in
'Standby' mode and 1.1A with 'Standby' off.
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MCS / TECHNICS / HITACHI Belt Drive Turntable Motor restoration
Page Link
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Nakamichi BX-1 & BX-125
cassette tape deck making (and probably others)
Rhythmic clicking / ticking / static noise.
We have both of these decks. We first noticed the issue of a fairly
faint, 'ticking noise' that was cyclical / rhythmic via the audio
outputs. It did vary with the rpm's of the motor. We swapped the
transports from the Nakamichi BX-125 to the BX-1 (their identical except
for the labeling on one of the motors). Swapping them made no
difference. We did notice that if we took a piece of wire (first used a
small screwdriver) and grounded the capstan drive motor shaft to ground,
the ticking resolved. They only make the sound with a tape loaded and in
'PLAY'. The decks will go into "PLAY" without a tape loaded and will not
exhibit the clicking noise then. They also will not make it if we load
and engage "PLAY" with an tape with an 'empty' shell. It seems to be
related to 'static build-up / discharge', but so far we haven't found a
solution. We could 'add' a piece of 'spring' from ground to the motor
shaft (has multiple, potential, future issues). We tried grounding
different points on the transport (it's actually already grounded) and
from the PB/REC head case to ground (although that should be a
completely isolated shell and SHOULDN'T affect it...which it didn't) to
no avail. I don't know if I mentioned it, but both have their original "Nakamichi"
#BFA2L36 motors installed.
Any advice / further info welcome.
NEW INFO 5/5/20;
In messing around with different 'ground points' (even grounding the
brass, motor pulley to ground) we were able to hear 'differences' in the
amount of clicking / ticking, but not able to practically address it
(temporarily touching a screwdriver to the spinning, brass motor pulley
to ground seemed to eliminate it, but not practical for the long
term obviously). We swapped the transports from a Nakamich BX-1 to a
BX-125 (they're almost identical decks internally) would change things 'willy
nilly', but nothing address it satisfactorily UNTIL...
the tech burnished / roughed up / scraped the zinc coated chassis parts
where the 'ground wire' connects the transport assembly to the chassis,
and 'torque'd' the screws down well and
voilà, CLICKING / TICKING
NOISE PROBLEM SOLVED.
We read a few other 'theories' out there on the web and were even
thinking some sort of 'filter capacitors' as well, but it was simply
'compromised grounds' (which is often the culprit in electronics).
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Nakamichi CR-3A (and likely
others)
cassette tape deck plastic can react with "CRC Contact Cleaner 2000".
We just experienced all of the plastic push buttons melting / welding to
the face panel. First issue we've had with "CRC Contact Cleaner 2000".
'After the fact' we sprayed a bit on an out of the way area of the face
panel, and sure enough, the plastic softened and you could leave a
finger print in it.
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Pioneer CT-M6R, CT-WM77R, (and
probably other 'Multi-Play / Changer' cassette decks, such as the
Pioneer CT-M5R, CT-M6R, CT-M50R, CT-M55R, CT-WM60R, CT-WM62R, CT-M66R,
CT-WM62R & CT-WM70R, CT-WM77R)
There are 3-4 belts in these Pioneer "Multi-Play" cassette tape decks (4
in the 'dual / dubbing' versions). There is a belt located under the
'changer' transport to control the front to rear transport of the tape.
There is a small, square belt from a motor to a pulley that transports
the 'tape carriage' from it's 1-6 position to the stationary tape PB/REC
transport, and there is a 'flat belt' for the dual capstans on the
actual tape transport(s). The 'front to rear' transport belt is easy to
change and the 'flat' belt for the actual tape transport capstans is
relatively easy to change. The 'small, square' belt on the 'worm gear'
that controls the "tape carriage" is a BEAR to change. Fortunately, the
tape transports in these are 'gear drive' so there are no idler tires to
worry about every going bad or needing to be changed.
Additional notes;
CT-M6R, CT-M66R & CT-M55R appear to be the same
deck with different model / badge numbers, with the exception of no
'headphone' jack on the "55".
CT-WM62R & CT-WM70R appear to be very similar decks with
the "62" featuring some 'tape search / relay play' options and the "62"
does NOT have a headphone jack. Also they each have slightly different
graphics / silk-screening.
CT-M6R, CT-M55R, CT-M66R and CT-WM77R
appear to have the same 'changer / multi-play' mechanism. The
CT-WM60R is slightly different in that the lateral carriage has
it's 'rack gear' on the rear of the mechanism, instead of the top.
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Pioneer PL-40, PL-41, PL-50,
PL-50A, PL-51, PL-550X (and probably others) 'TONE ARM RETURN' ISSUE!!!
Like many turntables with 'auto arm' features, the
early Pioneer line had a fairly 'Rube Goldberg' way of working. It's 'bane'
is a rotating disc, w/ cutouts, that rotates in a bath of 500,000 silicone
damping gel (many folks erroneously think that it is an aluminum 'paddle'
that 'kicks' the tone-arm back to return, but that is only part of the
sensing mechanism. The 'real' return mechanism is WAY more complicated than
that!!!). The silicone damping gel may still be 'OK', or may have partially
leaked out, or became too viscous over the past 40 years. Also, the
mechanism rotates within and on a bushing that will need to be cleaned of
old lube, re-lubed and re-assembled. The entire operation is VERY difficult
and time consuming. So much so, that those tables are almost on our ''Red
Flag'
list from a restoration / refurb point...We're thinking about adding them.
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Pioneer PL-L1000 / Phase Linear 8000
Series II turntable 'Lead-In' adjustment
While the 'sanctioned'
adjustment for this table in the Service Manual for the Phase Linear 8000
Series II / Pioneer PL-L1000 turntable Lead in ‘set down’ is much
more involved than the following, for a minor, 'down and dirty' way to
accomplish the Phase Linear 8000 Series II /
Pioneer PL-L1000 tone-arm Lead in ‘set down’ points are determined for 7”,
10” and 12” by the triple tabbed, black, vertical metal part. It’s position
is adjusted by turning the ‘brass’ hex bolt at the left side / end of the
mechanism. It’s marked with a ‘Sharpie’, and 1-1.5 turns goes a long way.
Also, it is IMPERATIVE
that the Pioneer PL-L1000 or Phase Linear 8000 Series II
table be perfectly 'level' for the tone-arm 'set down' to land correctly.
Both tables have vertically adjustable feet to facilitate this, but you will
need a 'bubble / spirit' level to accomplish this.
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Pioneer SX-3800, SX-3900,
SX-D5000, SX-D7000 (but applicable to most amplifiers)
Originally after biasing a
SX-D7000 the way you typically would, we realized that it's bias MUST be
referenced to VERY specific test points, and be done in two stages.
After doing an initial bias & offset, we found the unit ran very hot
(measured about 185 degrees F over the heat-sinks). We discovered that
the biasing procedure was somewhat different and must be followed
exactly on this particular unit (and likely the above listed units as
well). Once that was done, the temp was lowered to around 125 (still
pretty damn hot). A number of techs (including a couple of component
designers) opinioned that if it's biased correctly, it probably "just
runs hot by design". I still wasn't convinced. After speaking to one
more tech (who happened to call for a part for a Pioneer SX-3900 he was
working on), per his suggestion, we decided to remove all the outputs
and re-fresh the heat sink compound (we always check it for viscosity,
and this seemed ok originally, but upon further inspection, decided that
is wasn't as 'soft' as it is when fresh). After changing the heat-sink
compound, the temperature measured around 95°F,
a further reduction of about 30 degrees, for a total reduction of almost
a hundred degrees F.
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Sansui 880 / 880DB, 8080 / 8080DB, 990 / 990DB, 9090 /
9090DB Stereo Receiver repair notes;
There are a few 'red flag' issues with this series of
Sansui receiver models that we can almost always count on. 1) the dial /
meter lights / lamps will be intermittent., 2) The 'input', 'Dolby' and
'Tape Monitor' selector 'Wafer' switches are almost always intermittent, 3)
They will likely have 'driver board' issues.
Selector switches and driver boards are for Sansui 880 / 880DB, 8080 /
8080DB, 990 / 990DB, 9090 / 9090DB are some of our most commonly requested
parts.
The dial / meter lamps on these models collectively draw over an Amp of
current. The input selector, also selects which lamps to turn on. They used
an
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'audio signal' grade wafer switch to route the 1-Amp+ of current. Bad
design from the start. About the best approach we've found is to address the
switch for 'audio use' ((no easy task as the wafers need to be removed from
the switch chassis and circuit board (LOT's of de-solder points and bending
metal that's not meant to be bent), not letting the center turn 180 degrees
while doing this and not bending any of the contact fingers), the burnishing
of
the inside of the fingers and the outside of the rotating part. We use a
fiberglass pen and contact burnishing files for this)). Then once that's
done, figure out the correct points to shunt / short cut the lighting
circuit so it will be on all the time, regardless of the source selected.
Due to the time involved in restoring / modifying those two switches, as
popular as these units are perceived to be, they are now on our 'NO FLY'
list from a restoration / refurb point.
As far as the driver boards, if they are not 'too far gone', typically
changing the electrolytic caps will take care of most of their issues
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Sansui 880 / 880DB, 8080 / 8080DB, 990 / 990DB, 9090 /
9090DB, 2000, 2000A, 2000X, 4000, 5000, 5000A, 5000X and maybe others Stereo Receiver repair notes;
How do you remove the switch cap (plastic
or aluminum) from the 'push switches'?
With GREAT difficulty and risk of breaking the switch shaft, locking
mechanism, injury to yourself and just general mayhem. They are glued on
the nylon switch shaft originally at Sansui. It is possible to remove
the switch cap (black plastic or silver / aluminum (which has a plastic
insert)), but it's risky. We remove the switch or entire circuit board,
put the switch in the 'out' position (to reduce risk of damage to
'locking mechanism'), lay the switch shaft down onto the edge of a table
/ work surface, and insert a small 'brad puller' (looks like a
screwdriver, but with a 'forked and curved' end) between the shaft
flange and the cap base. We then apply an 'inordinate' amount of
pressure, rocking the tool back and forth. 'Usually' the switch cap
finally 'gives way' and will come off. Sometimes the nylon switch shaft
breaks, leaving the remains inside the cap. Sometimes the tool slips and
goes into our hands or anything else nearby. Unless you have a VERY
compelling reason to remove one of those caps, I would leave it.
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Sansui 7070 Stereo Receiver repair notes;
On
a recent Sansui 7070 repair / restoration we experienced. The symptoms were
a loud, volume dependant 'pop' noise when most any switch was manipulated,
especially the 'Loudness', the pots, made a 'swishing' sound when turned,
and the tuner was very intermittent (mostly not working). All other inputs
seemed to work. After a bit of investigation, we determined that it seemed
to be associated with the F-2625 circuit board. When we tapped on the board
with a dowel, the tuner would at times start to work. It was appearing to be
most near the Relay, and we have seen corroded relay contacts cause similar
symptoms. Luckily after about 15 minutes of this we discovered it was one of
the screws that secured the board to the chassis, and was supposed to be
soldered in place.
The solder joint had given way and the screw was slightly loose, causing
all the issues. Once tightened (and re-soldered of course), the problem
was solved.
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Sansui 5000A Stereo Receiver repair notes;
These receivers are 'cap coupled' outputs. Common
issues are 'aged' electrolytic caps that not always, but sometimes 'have' to
be changed. We recently sank an inordinate amount of time into one of these
(14+ hours) tracking down issues on the 'F-1040' 'driver' circuit board. The
unit was exhibiting a 'slight, intermittent, irregular static' out of one
channel that was independent of any 'source' or 'pre-amp' change /
manipulation after it's basic restore. We did the normal test for loose
components / bad solder joints which at times did seem to affect it, but we
couldn't narrow anything down. We replaced all the electrolytics, not only
on that board, but the filter caps as well as the coupling caps and the
power supply caps during different stages of it's restoration prior to
concentrating on the 'static' issue. All components on that board were
tested to varying degrees. We finally narrowed it down to a bad, worn-out /
corroded 500k Ohm, pc mounted / micro-pot. However in changing the pot,
something else went south and by that point we were about to 'pull the plug'
on the patient. We did have another Sansui 5000A that had serious FM tuner
issues, but the rest of the unit had been restored. We decided to take a
driver board from it, and move to this unit. Viola, all was well and the
unit 'dialed in' (14 hours later!). Normally we would hope to be into a unit
of that caliber no more than 6 hours. Oh well, you win some, you loose
some...
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Sansui TR-707AStereo Receiver repair notes;
We've had a customer call to order the 'dial glass' as he said the
'silk-screening' on the reverse side is actually 'water soluble decals'
so be careful when cleaning. We've actually seen this on a vintage Sony
Receiver as well.
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SONY TC-105 (probably
TC-105A as well) Excessive head wear causing diminished 'high frequency'
playback / recording;
Issue: Sony TC-105 had diminished high frequency response, especially
when the 'track switch' was set to "1-4". As this is a 'mono' ONLY deck
(4-Track / 1-Channel) we deduced that there were no separate electronics
for the two different positions of the 'Track Select' switch, so there
wasn't much else to cause the issue in the end, other than excessive
head wear (which was fairly visible as well).
A:
We had 3 Sony TC-200 units (which are stereo) that we thought could have
the same head (and all had other {practically terminal} issues to cause
them to be 'donor units'). Sure enough, they had the same part number,
Sony PP30-4202 LN (however that number is stamped on the 'head housing /
mounting' assembly. You must bend the tabs in the rear and actually
remove the 'head element' which has not identifying marks). We chose the
head that had the least wear of the three, and 'viola', the TC-105 now
played back and recorded high frequency MUCH better and within 6db pole
piece to pole piece. This RPH (Record / Playback Head) head appears to
have been used in at least the Sony models; TC-105, TC-200, TC-250 /
TC-250A, TC-252, TC-255, TC-350, TC-355, TC-530 and likely others. The
coils measure 25 Ohms each.
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SONY TC-200 Reel to Reel Speed Slow and then runs slower
Issue: Sony TC-250 reel to reel runs ‘slow’
(excessively at about 10% slow, then slows down from there to about 20% and
doesn't stabilize till about 30 seconds each time.) It will do this every
time you stop, then re-start the deck. We've
overhauled EVERYTHING and replaced the start / run capacitors and tried
different motors. This is the 4th or 5th Sony TC-200 that we've experienced
this issue with....
A: We're still working with them, trying to solve the
problem....
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SONY TC-350 Reel to Reel Speed Slow issue
(This info would apply to most Sony Reel to Reel tape recorders from mid
1960's thru early 1970's)
Issue: Sony TC-XXX reel to reel runs ‘slow’. I’ve
overhauled EVERYTHING and replaced the start / run capacitors.
A: The motor is a ‘Hysteresis’ type motor and its speed
is controlled by the 60Hz cycle of AC power. Originally Sony had optional
and incremental motor drive pulleys available numbered approx -5% thru 0 to
+5% that could be substituted to correct the speed up or down, usually
faster. That could increase the overall speed of the machine. Those are no
longer available and decks usually are going to have the ‘0’ version
installed by default, with no changes having been made throughout their
lifetime. We had a deck that was playing back our 1000Hz test tape at 970Hz.
+/- 3 to about 12 cycles is not too bad / noticeable unless you’re a
musician needing to ‘sync’ tuning with your instrument / voice. 970Hz (30Hz
low in pitch) was VERY noticeable, even with ‘speech’ only tapes and
rendered the deck not usable for playing ‘previously recorded’ tapes.
We ultimately had to take the 100mm flywheel to a
machine shop and have it machined down to 97 mm for our case (we only did
this extreme procedure because we had already invested over 18 hours into
it) and that alone added 3 hours of time running it there and explaining
what was needed and $45 more dollars to the restoration (we tried to DIY it
on our drill press with a vertical file, but it started oscillating /
ringing, which caused the file to ‘chatter’, leaving an uneven surface, not
to mention that the ‘ringing’ sound it made was unbearable in the shop (the
machine shop said the 'ringing' noise was hard on them as well).
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SONY TC-377 / TC-366 Reel to Reel Speed Slow issue
(additional information to the TC-350 issue mentioned above)
Issue: Sony TC-377 (same transport as TC-366) reel to
reel was running slow, so we had to have the flywheel (2 surface / stepped)
machined down a bit. Once we did that, the clearance from the flywheel to
the 'idler wheel' was too great at the 1 7/8ips setting.
A: There's not really any official adjustment, so we
had to bend the idler tire connector wire / bar. Not really a fine science,
but 'kinking' it slightly either side of it's spring did the trick.
(photos coming)
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SONY TC-560 / TC-560D Reel to Reel
intermittent playback / recording of channels (ie; sound cuts out)
Issue: Intermittent sound on playback / record. Sound cut's out
sometimes.
A:
Yeah, this deck has some VERY long, multi-pin switches (I can't remember
exactly, but there's at least 3 that need attention) related to playback
and recording that, while never meant to be serviced, need to be
disassembled completely and cleaned / burnished. They are very 'buried'
between the chassis layers. I may go into a bit of 'how to' at some
point, but suffice to say, it's a VERY difficult and VERY time consuming
process to address this issue on the TC-560 series. Maybe try 'slamming'
the 'play / transport' selector from 'Stop' to 'Play' or aggressively
'jiggle' it to see if that fixes the issue temporarily.
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Teac A-4010 and it's
variations (Teac A-1000, A-1200, A-1230, A-1250, A-1500, A-1600, A-2000,
A-2300, A-2340, A-3300...Ok, pretty much most or all of the early "A" series
decks...:
The Teac A-4010 / 4010S
etc, was probably 'the most sold' reel to reel deck ever made by anyone.
Seems like pretty much everyone that went to Viet Nam during the war came back with one of
these. They are fairly typical of most reel to reel restorations (plan on
12-18 hours to do a thorough job), but they have one unique mechanism that
will certainly need to be addressed. It's the pinch roller arm assembly
(#14142 {aka; 50141420} on the A-1200, A-1200U, A-4010, A-4010S). It
is a 'cast / pot metal' affair that pivots on a pin / axel. The pin
may be detachable from the main chassis or can be riveted / 'press-fit'
/ braded in-place.
Either way, the arm will be in some state of 'sluggishness' to
completely 'frozen' due to old,
varnished lubes. It will need to be removed, cleaned and re-lubed. It
may need to be heated (best with a heat gun or blow dryer) to facilitate removal. Do not force it, or you may
loosen the press fit pin yes, I've done that by not waiting long enough
for the heat to take effect). Wait for the 'heat' to take effect, then with a
suitable tool (pliers) wriggle / twist it back and forth as you pull up on the
pinch roller arm. You may need to re-apply heat during the process until it's
completely free of the pin. Once done, the bushing / pin surfaces can be cleaned
with solvent and properly re-lubed (along with pretty much every other moving,
mechanical part in the deck).
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Teac A-6010GSL and it's
variations: Issue: The tape tends to 'track off' or skew out from
the pinch roller / capstan on my reel to reel tape deck...
Likely applicable
to most TEAC's around this model / generation.
A: While many tend to blame the 'pinch roller' or bent or skewed tape
guides, I have usually found this to be the fault of improper 'back
tension' on the supply reel and on a couple of occasions, too little
pinch roller pressure. You can test that theory by applying a bit
of 'caliper braking' action to the outside edge of the supply reel with
your fingers while the deck is playing. Not much, just a bit, and the
tape will usually come back into alignment. Unfortunately, this is not
usually an easy thing to correct. On earlier decks, such as Sony's, it's
done with a clutch made of felt, on others, with brake pads. On later
decks, it's typically done with a small amount of 'reverse' voltage
applied to the 'supply reel motor'.
If the back tension is 'maxed', you can still affect it
with adding pressure with your fingers, then it's likely lack of 'pinch
roller' pressure. You can test this theory, by adding pressure to the
pinch roller, towards the capstan. If you're able to do it quickly
enough when you see the tape 'start' to skew, and the added pressure
pulls the tape back to the correct path, then you've probably determined
the problem. Some decks may let you adjust pinch roller pressure, some
may not.
Regardless, any of the measures to
address the 'tape skewing' symptom, any repair is not particularly 'end
user friendly' is beyond the scope of this page.
Seek professional assistance for that one.
(revised 2019)
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Teac 3440 Auto-Stop doesn't
work, but 'Stop' button works fine;
While this could be an issue with the 'transport / Logic'
circuit, it's likely an issue with the 'micro-switch' that the tension arms
control. The switch could be bad / broken, or may need to be adjusted
slightly in it's mounting. We have seen the mounting bracket need to be
're-built'. This problem / solution would be applicable to many brands /
models of reel to reel tape decks.
Teac 3440 Channel playback doesn't work on all channels or is
intermittent;
While there are a
number of possible suspects, one of the main failure points on a TEAC
3440 are the circuit board / card 'edge connectors'. The contacts likely
need to be cleaned / burnished, and / or the contact 'fingers' need to
be 're-sprung'.
Teac 3440 Meter lamp is out and I can't figure out how to access them to
replace;
Oooohh Boyieee! Have fun
with this one.For what would seem like what should be a
'simple thing' to rectify, you'll find out that it's not. While most of them
are accessible via normal means / efforts, the bulbs / lamps on meter #
4 will require a substantial disassembly of the deck to address. Accessing them is
half the battle, and it's going to be a fairly long battle. Pretty much most
of the deck will need to be disassembled (not very forward thinking on TEAC
/ Tascam's part from a 'serviceability' standpoint) to access the meters
(TEAC / Tascam fixed this and most of the other 'serviceability' issues on
the later TEAC 40-4 (waayyy better deck) ). Once there, you'll need to make
sure that what ever lamps / bulbs / LED's you choose have a very low current
draw collectively (like less than 100mA). If you exceed the current draw
limits, an 'Output Muting' circuit will cause the output from the playback
amp to cease. I don't remember at this point what the current 'threshold'
is, but it's pretty low. We replace with LED's so the cumulative current
draw is VERY low relative to incandescent counterparts (and 'incandescent'
lamps / bulbs that work on 7.5 Volts, and draw 20-30 mA are very elusive to
obtain in any 'physical package' we've found )
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Teac X-1000R Meter lamp current draw;
Do not substitute higher than intended current draw light
bulbs in the meter. We installed 250mA lamps and the logic circuit failed.
We removed them, and it worked again. We then modified some 35mA lamps to
fit and they worked well with the unit. The same may be applicable to the
Teac X-2000R as well, but that's only an assumption.
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Technics SA-600, SA-700, SA-700A receiver models and likely others, DIAL /
METER LAMPS;
The original / OEM lamp / bulb utilized in this
receiver was a Stanley 6.3V / 250mA, #XAMR62S. While this bulb did
originally tend to have a typical and sufficient lifespan, we have found
that the new 250mA bulbs available (as the original Stanley XAMR62S does not
appear to be available anymore) are not of the quality of the ones that were
originally available, and will not last very long (likely less than 30 days
of normal use). The 250's are burning extremely 'white hot', which will look
good for a while, but again, what's available today are not as robust as the
originals. Trying a #1302, 6.3V / 40mA is a bit too dim, but 6.3V / 150mA,
#1847, is a good compromise. Still not as bright / hot as the original 250mA
lamps, but work well, and illuminate the front panel sufficiently.
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Technics SB-7000 / SB-7070 Speaker Foam Surrounds;
There seems to be a general opinion out there
that the foam woofer surrounds on Technics SB-7000's and SB-7070's are
'special' and do not rot or require replacement. B-o-o-o-o-o-o-gus!
While the do often appear to be in better shape / condition than the foam
surrounds on most drivers, and do not seem 'as rotted' or deteriorated, they
do deteriorate and will crack. A seemingly perfect appearing pair, will
start releasing after a few 'loud' selections from a 'stout' amplifier. The
same is all applicable to Radio Shack, 'Mach Ones' woofer foam surrounds.
Both the Technics SB-7000's and SB-7070's and the Radio Shack, 'Mach Ones'
did come with some very 'durable' foam surrounds, that will appear at first
to "still be serviceable" and / or "don't need surrounds", but they are not
immune to foam rot. Unfortunately, there aren't any 'exact fitting' foam
surrounds available for the Technics SB-7000's and SB-7070's so you need to
get a kit that is close and 'sever and splice' it (not a big deal, nor
detrimental) to resurrect them. Try www.speakerrepair.com ,
www.partsexpress.com or
www.simplyspeakers.com to name a few.
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Yamaha CR-820 receiver intermittent sound:
We had a Yamaha CR-820,
that had an issue with intermittent sound (don't remember the particulars of
which channel) that was taking an inordinate amount of time to
trouble-shoot. Acted like a bad / cold solder joint, broken trace etc,
however we couldn't track it down to any particular area of the unit or
circuit board. Seemed like anywhere we 'taped' or banged on it, we could
affect it. After about 2 hours, we discovered that one of the circuit board
mounting screws was designed to ground that board to a part of the chassis
that ran down the middle of the unit. A quarter turn of the screw and the
problem went away. We have since had a similar issue with a Sansui 9090DB
and a JVC JR-S501 receiver.
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Yamaha CR-2020 receiver...power
supply circuit board issues:
We had a Yamaha CR-2020,
that had an issue with intermittent issues. We traced it down to multiple
issues with the power supply board. We also discovered in originally
doing the refurb / service on it that there were at least 2 or 3
'service bulletins' that had been released on this unit regarding
upgrading some of the parts on the power supply circuit board. Even
still, it had run hot in the past, which had caused 'browning' of the
board and some traces to lift. Also, part of the work dictated by the
service bulletins involved installing 'heavier' (higher mass) resistors,
which now put extra stress on the solder joints. We also found that the
heat sinks on the voltage regulators were secured to the board only by
the soldered leads of the regulators. We're in the process of utilizing
'high temp' epoxy to secure the parts and patch up the solder joints /
traces.
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Yamaha 'M-40 / M-60 / M-65 / M-80 / M-85 / MX-1000 / MX-1000U' Speaker
output posts prone to breakage, especially in shipping / transit:
We have learned the
'hard way' not to ship a Yamaha 'M-Series' amplifier without removing the
'Red' and 'Black' speaker connectors from their binding posts. In fact, it's
probably best, if possible, to remove the 6 philips screws and push the
entire barrier strip back into the back panel (add a bit of 'easily
removable' packing to reduce 'rattle' in transit).. On the Yamaha M-60 power
amp, it's at least possible. The Yamaha 'M-80' may not be as conducive to
this procedure, but AT LEAST, remove the Red and Black posts. To further
reduce the chance of future 'handling' damage, we also 'shot' the underside
of the plastic housing (the part that breaks) full of 'hot glue'. That adds
A LOT of structural integrity to the assembly. We are VERY good at packing,
with only ONE (1) minor ship damage issue in over 18 years / 19,000+ packs.
That's an INCREDIBLY UNBELIEVABLE record!!! Ironically, this amp was damaged
utilizing the ORIGINAL YAMAHA M-60 FACTORY BOX AND PACKING, that was in turn
'floated' in an oversize box with more packing. I used to sell this amp new,
as a dealer, and I don't remember the speaker post inserts being removed for
shipment, but could be mistaken. Regardless, we will from now on.
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Yamaha R-1000 receiver - add to 'No Fly' list:
We have just tried to
restore our last Yamaha R-1000. These seem to always have issues with a
Darlington pack STK3106 'Driver power pack'. Hard to find, difficult to
troubleshoot and short of replacing it, nothing to repair. Also, unit use a
proprietary battery for the FM tuner preset memory. Not a 'big' issue, as we
can 'special order' them, but coupled with the STK3106 issue, it's just not
one of the better unit to sink much time into.
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MISC NOTES:
A bad ground, corroded / fatigued wire or cold solder
joint can chew-up 'HOURS' of tech time trying to find and can be very
exacerbating, both for the tech and the person paying the bill. Generally
other than 'hunting and pecking' or reflowing EVERY solder joint, it / they
can be difficult to locate.
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Units / topics we will be addressing
in the future:
Kenwood 'Eleven-III' & KR-9600 'push-button' keeper issue, and don't
remove from front.
Pioneer SX-3700, SX-3800 & SX-3900 dial light change difficulty.
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NO OTHER INFORMATION, NOR ASSISTANCE AVAILABLE
PLEASE DO NOT CONTACT US WITH QUESTIONS SUCH AS, "HOW DO I.....? OR "HOW DO
YOU REPAIR A.....?"
We do not have the resources to address any repair / DIY questions.
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-
ATTENTION: We recommend you DO NOT DISASSEMBLE or ATTEMPT TO REPAIR OR
REPLACE ANY PARTS ON ANY ELECTRONIC / ELECTRICAL DEVICE without proper,
technical training and repairs / modifications should always be left to
qualified technicians.
"WARNING: PLEASE
USE CAUTION WITH ANY ELECTRICAL DEVICE. ANY REPAIR AND / OR RESTORATION
SHOULD BE UNDERTAKEN ONLY BY A QUALIFIED TECHNICIAN. DO NOT OPEN OR ATTEMPT
TO REPAIR ANY ELECTRONIC DEVICE WITHOUT PROPER INSTRUCTION, EXPERIENCE,
BACKGROUND, TRAINING OR KNOWLEDGE, OR TAKING PROPER SAFETY PRECAUTIONS.
THERE ARE NO 'USER SERVICEABLE' PARTS, SYSTEMS OR CIRCUITS INSIDE.
POTENTIALLY HARMFUL, INJURIOUS AND / OR LETHAL ELECTRIC VOLTAGE AND CURRENT
INSIDE.
IT CAN KILL YOU AND WILL HURT THE ENTIRE TIME YOU ARE DYING"
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