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Since 1982.



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.


























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.


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).
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'.

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
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 'NO FLY' list from a restoration / refurb point...We're thinking about adding them.
Pioneer PL-L1000 / Phase Linear 8000 Series II turntable 'Lead-In' adjusment
     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.

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 7070 Stereo Receiver repair notes;

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...

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)

Teac A-4010 and it's variations:
     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 came back with one of these. They are fairly typical of most reel to reel restorations (plan on 12-16 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. It is a 'cast metal' affair that pivots on a


pin / axel. The pin may be detachable from the main chassis or can be riveted in-place. Either way, the arm will be in some state of 'frozen' due to old, varnished lubes. It will need to be removed, cleaned and re-lubed. It may need to be heated to facilitate removal. Do not force it, or you may loosen the press fit pin.


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 , or 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 '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.

     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.



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.



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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