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Purveyors of Electronic, Musical and Vintage goods from then, now and in between. 
Since 1982.

RANDOM ELECTRONICS REPAIR / RESTORATION NOTES / HINTS

 

These are notes of interest, and observations we have made, while doing specific repairs / restorations on vintage Hi-Fi stereo gear, 8mm & 16mm film projectors, Beta & VHS VCR's, vintage home audio speakers, guitar amplifiers, keyboards, tube radios and amplifiers, etc. This is a work in progress and will be growing as time allows.
UPDATED 4/26/2021

 

              

 


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!
 

 


We will be adding MANY notes / info as we go thru old 'work sheets', as time allows and repairs are completed...
 
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.
 
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).
 

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.

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.

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.

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.

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).

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.

     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.
 
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!
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.
 
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.
 
 
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'.
 
 

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.
 
 

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.
 
 

MCS / TECHNICS / HITACHI Belt Drive Turntable Motor restoration Page Link
 
 

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).


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.
 
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.
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.
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.
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.
 

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

'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
 

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.


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.

 
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...
 

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.

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.
 

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....
 

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).

 
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)
 
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.
 
 

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).

 



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)


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 )
 

 

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.

 

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.

 

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.
 

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.
 

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.
 

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.

 

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.
 
 

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.


 

 

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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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.


 
-
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 information contained here is simply my personal findings and is not intended for anyone / or any entity to use to make any decisions to repair, disassemble, modify, or do anything. It is strictly for entertainment value. Please do not email any responses or call with any information related to it. It is also likely to change as new / additional information comes to light, or I change my mind or opinion. So There!


 

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