Sony TA-3200F Crackling Noises

[khileman]

I recently got a Sony TA-3200F Power Amplifier. It is in great cosmetic condition but seems very original in terms of internals. I am having a few issues with it, and I have some experience with electronics and soldering, but not much, so I'd really appreciate some pointers. I have done testing of the amp using a Schiit Asgard 3 and a Schiit Saga S as preamps, with a random pair of old Bose speakers that work fine on my other amplifiers. I have used Deoxit spray on the pots and checked my connections to make sure they are solid, as well as doing a visual inspection of the internals. No resistors look burnt, there is nothing leaking anywhere, no odd marks on the PCBs. The bias adjustments are all untouched and have paint marks from the adjustment at the factory.

The problems: There is crackling on both channels, mostly around mid and high frequencies. When the left channel is turned up, and the right channel is turned all the way down, there is a lot of crackling in the right channel, and vice versa. This cross talk seems kind of weird to me. When both channels are even, there is crackling across both of them. Also, the power limiter switch on the front doesn't seem to change anything about the audio output.

Potential solutions so far: I have looked at many threads online and it looks like capacitors are problematic in many cases. This thread explained the recapping process for most capacitors except the main 8000uf caps. I purchased those caps he used in his unit, but I don't want to go down that route of lots of soldering yet until I get more of an idea of what might be wrong. I also can't seem to figure out if it is safe to test the caps while they are installed in the circuit board.

There are several different iterations of this amp, mine being serial number 811472, one of the later US models. I have the service manual from hifiengine. I have attached many photos of the amplifier for reference.

I would really appreciate any help on this project! I am relatively new to audio and electronics, but I am willing to learn and gain some new skills. I love the features of this particular amp like dual inputs and dual outputs and the individual volume controls, almost makes it like an integrated amp but while letting me use my modern Schiit Saga preamp to remote control it all!

Thanks

 

[Lavane]

There are a couple small diodes, probably those little black beads near the top of the amp board. One on each side. They need to be replaced with two 1N4148's per side. They go noisy. I had the same crackling noises along with some drop outs due to these going bad. I thought the gain controls or the selector needed cleaning, but that didn't solve it until I replaced those dual diodes.
I would use some contact cleaner on the gain controls first though.
The amp could do with a recap also. It looks like the two black electrolytic caps on the power supply board are starting to bulge.

 

[khileman]

I see the bulging capacitors now that you mention it

 

[khileman]

There are a couple small diodes, probably those little black beads near the top of the amp board. One on each side. They need to be replaced with two 1N4148's per side. They go noisy. I had the same crackling noises along with some drop outs due to these going bad. I thought the gain controls or the selector needed cleaning, but that didn't solve it until I replaced those dual diodes.
I would use some contact cleaner on the gain controls first though.
The amp could do with a recap also. It looks like the two black electrolytic caps on the power supply board are starting to bulge.

Thanks! This is a great starting point. I see the diodes you are talking about. If there is currently one on each side, how do i replace with two per side? I'm just confused about that since I am new to this. Thanks

 

[EC1]

You put them in series. Don’t just take my word. Search 1N4148 you should be able to find answer.

 

[Lavane]

Tie them together like the picture below.
You will have to look at the orientation on the schematic when installing them so that they are going in the same direction as the original dual diodes. Look at the power supply board. My version had one if those VD1221 diodes on it also.
A couple other things that should be replaced are the two little orange Tantalum caps on either side of the two center trim pots. Use either an audio grade electrolytic like a Nichicon brand, or Wima stack film polypropylene caps. There may be one on the power supply board too. Although I don't see one on your power supply. There were various changes made to these amps over the 6 year run of production.

 

[milo63]

I just finished stage one (new caps) on my 3200F and noticed a bunch of Uniwatt transistors that need to be replaced on stage two.
It's a very nice sounding unit, as most Sony gear of the era is.

 

[khileman]

Tie them together like the picture below.
You will have to look at the orientation on the schematic when installing them so that they are going in the same direction as the original dual diodes. Look at the power supply board. My version had one if those VD1221 diodes on it also.
A couple other things that should be replaced are the two little orange Tantalum caps on either side of the two center trim pots. Use either an audio grade electrolytic like a Nichicon brand, or Wima stack film polypropylene caps. There may be one on the power supply board too. Although I don't see one on your power supply. There were various changes made to these amps over the 6 year run of production.

I just replaced all the capacitors, except the big 80v 8000uF caps and the little orange caps you mentioned. Also replaced the diodes as suggested. I am not hearing any improvement in the crackling issue. Will order some replacements for the big caps and the little orange ones as you suggested. Hopefully that does something

 

[khileman]

Here are the after photos from the recap:

 

[khileman]

Looking at this as a potential replacement for the big caps:

https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B41580A9109M000/3546028

 

[khileman]

Are these capacitors 3.3uF or 33uf or 330uf? Not sure of the units here.

 

[Lavane]

Those would be 3.3uf, 16v. Some use polypropylene film caps to replace them. Like Wima stack film caps.
Sorry to hear the noise is still there though. You may have some transistors going noisy on the amplifier board then. The one I had someone had replaced several with random transistors. I would bold off on replacing the big filter caps until the noise gets sorted out.