Acquired from the owner who did a partial repair (not bad either) but then said "screw it" and sold it to me. let's find out why and fix it if possible
Those 2SC1124's & compliment transistor 2SA706 were notorious for going noisy due to diseased legs, they were used in power supplies, audio amps & as video o/p transistors in Sony's 70's 80's &90's stuff & I changed hundreds of them when I was a Sony agent.
Back in 80s my brother and I worked on this beast. After we fixed a couple blown transistors, you are getting constant humming on one channel. My suggestion was those big black caps had gone bad. After a few years one day it was fixed.
I worked at a Sony dealer (and after that actually worked for Sony) when this receiver was introduced. It was the receiver that caused our dealership to drop the Sony audio line. The previous model 6065 was a thing of beauty. Built with care, the innards had neatly bundled wires and easily accessible components. We sold hundreds of them and they were bulletproof. Then they replaced it with the 7065, with its rat's nest of wires and sloppily placed components. What a disappointment. I'm sure it performed well when working properly, but it certainly didn't evoke any sense of quality. When I worked at Sony, we saw many of these in the shop, with blown outputs and power supply regulator issues.
@Kent Teffeteller From a build quality perspective, the 6120 and 6065 totally trounce this receiver. The 6120 was really a gem. But with the development of better semiconductors, they were still able to improve the electronic performance compared with the older models. E.g., the earlier units all used quasi-complementary output stages with single rail power supplies and capacitive coupled speaker lines. The later units were all full complementary with matched pnp-npn pairs and direct coupled outputs. Distortion was lowered and power was somewhat increased. The FM performance improved too, with the introduction of IC multiplex chips, , IF amp IC's, etc. Not to say the 6120 was a slouch...it had a 5 gang FM front end! But, why Sony dropped their build quality so drastically is still beyond me. I guess it was just a matter of meeting the competition's price point. I think that strategy failed, as it took years for Sony to regain traction in the audio products division. I was hired by them as part of that effort, and had a lot to say about where I thought they had gone astray.
Those rotary switches are a pita...especially on Yamaha CA units. I use several a pipe cleaners mounted in a small drill to get the pipe cleaners into them. Very delicately. Sometimes I use a small amount of metal polish, then iso and f5.
What's scarier about alot of the ones that are PCB mount (like in the yamaha C-4) is the rivets that hold the switch contacts to the foil traces that go down to the boards are loosening and causing intermittents. I literally have to solder wires to the rivets then down to the nearest foil trace. Requires the switch be pulled and disassembled. Happening alot more now.
@@t1d100 take a pipe cleaner put it in the drill and cut to length, apply metal polish, deoxit, or iso directly to the pipe cleaner. Put the drill on low and the clutch on the lightest setting. Insert the pipe cleaner into the rotary switch and engage the drill slowly to clean the switch and traces. I go metal polish, flush with iso, clean with pipe cleaner soaked in iso and finally flush with deoxit. This method is effective but risks a catastrophie if you are dumb and overdo it or get the pipecleaner jammed under a contact pad. I only do this as a last resort before unsoldering the 60 solder points required to remove the switch. It works well, but not really a move for noobs. But the amount of tarnish that is removed in the first pass will blow your mind.
This is interesting indeed. Unlike many of the receivers you get, it looks like this one needs repairs in just about every stage to make it right again. But I have no doubt that you will
Most of my DC flickery probs have come from input differential pairs especially (JVC JA-S & Pioneer SA/SX)...again as you pointed out - when the legs show signs of corrosive activity ...40 to 50 years of humidity and life have allowed air through the leg pockets on old tranny packages ...great video Jordan
I use a squeeze bottle with a needle applicator filled with isopropyl or a syringe with iso. That way I can get it into tiny holes and flood the switch nicely.
Dear sir your servicing inspiring me a lot and helpful to know more about the electronics. I have a bush brand radio receiver with MW and SW1&2 AM bands. The complaint was it stops receiving any stations from all 3 bands. I have tested the IF coils, band selector switch and all the passive and active components. Transistors biasing found ok. When I touch the AM MW ferrite coil it picks a local station with poor amplification. However the amplifier works well with cassette. I am not sure about the gang capacitor and polystyrene caps. Please drop your suggestion what to do next to make it function.
Sounds like the voltage to the oscillator may be low or the oscillator transistor itself may have failed. This typically is when the transistor changes internally to require more forward voltage to bias that the circuit can't provide, or the gains of the transistors go down. The fact you can influence it suggests the circuit will work. I would look at the oscillator
Weird that you say the 2SC945 is a problematic transistor. I’ve never run into a faulty one, seem far more reliable than the hundreds of faulty 2SC1345s or 2SC458s or 2SC1313s (or 2SA726, 2SA725, or etc, etc) I’ve replaced and I’d say that they are used nearly as much as the 945 depending on what gear you’re working on. Maybe I’ve gotten lucky. If I’m doing a restoration I’ll usually do a clean sweep if it’s in the budget. I just finished a Kenwood KA-8006 and oddly enough every single transistor in the unit was replaced with the exception of four C945s on each amplifier board lol. Either Kenwood made some poor choices or good transistors weren’t easy to make back then. Who knows, 40 years from now techs will be saying to rip out every KSC1845 and KSA992 you see as they’re all garbage and will fail in time.
Would have been nice if the Stereo Decoder was a DSP based Decoder then you would have had a SPDIF out that could drive a DAC which could connect back into the Tuner.
I was looking at possibly purchasing one of these as I’ve heard good things about the sound quality. But to me, of secondary importance is the serviceability. After viewing your video, it’s become a hard “no” for me. The sloppy execution by Sony just eliminates it as a candidate for my shelf.
Jordan, I acquired this very model receiver from a friend of mine, however there is no sound at all. Could it be over oxidation on the controls? It just has a VERY slight scratching noise when turning volume up or down. Sometimes no sound at all. Hope to hear from you for a little advice.
Sounds like loss if s power supply to the preamp. Might be oxidized tape monitor or input selector switch. You can try cleaning them with a contact cleaner, but if that doesnt fix it its more likely a power supply failure
Hi Jordan, at about 21:10 you lost the left channel due to a dirty switch. Since the noise in the left channel did not appear after you cleaned the switch, why would you not consider attributing the noise to that dirty switch instead of the suspected transistor?
I was more concerned about the DC fluctuations that I saw, which wouldn't be caused by a dirty switch, since they occured in the separate position - disconnecting the amplifier section completely from the preamp.
Jordan; I wish I had just a little bit or your electronics knowledge/skill. I have a Sony STR 7035 that is about the same vintage as the one you are working on. My problem is with the FM tuner. It has a habit of just shutting off.. Sometimes it works for hours or days. Sometimes not at all. I use the contact cleaner on the fins and shafts of the tuner. Spraying them down thouroly while rotating the tuning knob back and forth. It will work fine for a while and then quit. GRRR. Do you think I just need to clean it more, or maybe there is something else wrong with it?
Spraying stuff into the tuner unless it dries with no residue is a BIG no-no. If both am and fm quit at the same time, most likely culprit is the 12v power supply that feeds it. Transistor controlling it might be failing or a bad connection that fails when it heats up
@@JordanPier only the FM is having the problem. I am using CRC contact cleaner and using a small air jet to dry off the excess cleaner. The cleaner seems to evaporate quickly tho.
@@randallfawc7501 if you go to silence on FM and not static, see if turning off fm muting helps. If so the muting circuit or associated circuitry may be bad. If it goes to static, the oscillator transistor or trimmer capacitor may be defective. You can try tapping on the trimmer screws on the tuner to see if any changes occur. If that's no good then definitely oscillator transistor and associated circuit may be at fault
It's a tossup. Personally I think the late 60s-early 70s sansui and pioneer sets were some of the best engineering. There are one or two sony models of that era which are equally good but use proprietary parts that are near impossible to find.
Intermittent faults have to be the most annoying type. I would rather the device go pop so there is evidence . Hairline fractures in the tracks has sent me mad a few times.
@@JordanPier A bat lol , a plastic handled screw driver worked o.k. Freeze spray was handy but expensive. i hope you get that sony stable, nice bit of kit.
