Sony TC-377 Capacitor replacement?

[samth3mancgp]

I have an old (isn't almost everything in this forum? ) Sony TC-377. Since I got it out of my grandpa's basement where it sat for 15+ years I have had problems with it. It will move the tape fine, the motor and all of the belts work enough to move the tape at the right speed, But the sound coming out is troublesome.. I had a thread on AudioKarma about the Sony. To make a long story short; when the recorder was at my school there were seceral days where it worked by a stroke of luck for about 2 days. We were able to record and playback magnificently! But all the time before that and since There has been the same problem with almost nonexsistant record levels and thin playback.

Right now It sits taken apart about as much as it possibly can be where all the boards are still soldered in and it is possible to test. I have already tried switching out several caps but I put most of the originals back in. I even after searching on google and reading alot about testing capacitors I still don't know what I am supposed to do. My multimeter has a setting to test micro farads but it dosen't read any differently when touching a capacitor. I want to start with just replacing caps on 1 channel of playback and 1 channel of record. I see how the circuits are symmetrical and have the cables running to the heads on opposite sides of the board. I will probably replace every cap on the rec/playback boards using parts from radio shack, but I still would like to know how to properly test them. I'll just bring the parts list from the schematic in and get the parts I need.

 

[Tim Gillett]

If the machine was sent to a good technician he would trace the signal to the point where the signal stops or starts distorting.

The first thing is to narrow down whether the problem is in the playback or the record sections or whether in both.

Replacing all the caps is fine if you have the time and money and dont have the ability to actually trace the fault to its source, but it still may not work after all that work if that's not the problem.
The fault could be caused by a number of different things not just the caps. Most or all of the caps might be fine.

With this model the cap that often fails is actually the motor run capacitor, the big tin can near the motor. It results in poor motor torque.

Cheers Tim

 

[samth3mancgp]

The motors work just fine. It's playing on the left channel at the same pitch as the song sent to it (on the right channel which seems to work fine. However the left channel is giving me absolutely nothing except the input monitor. It wont record or playback anything. This has happened recently since I took it apart and started messing with it. It also used to start playing and recording fine if I warmed the PC boards with a heat gun a little. but this was before the current situation.

I got a solder sucker today at radio shack and I think I cleaned up some excess solder from the caps I was messing with. Some of the caps in this thing look like they have oozed a white or light brown liquid waxy substace from them and some are bulging a lot. I have replaced all but 1 cap (it was a higher uF that I couldnt find) on the power supply board with an assorted pack of caps from radio shack.

From what I have read, capacitors can be replaced with another one of greater than or equal to voltage and capacitance as the original. And the only thing that should be similar is the size (at least for cramped boards where replacing with larger ones isnt an option unless soldering to the bottom)

 

[ttw]

tc377 repairs

I have bought a tc377 recently and have it almost ready but I need a couple more parts - not capacitors - to complete the restoration. If you find you can't fix the capacitor problem on your boards - heaven forbid - , please contact me if you are in or around Ontario as I could use the system for parts to restore my 377.

ttw

Hamilton

I'm new to this site - if my email is not in the members list, I can send it to you

 

[Brian Oshman]

Sounds like the play/record switching is the problem. Try contact cleaner in the play/record switches.

 

[samth3mancgp]

I am pretty sure It is not one of the switches. That was the first thing I was told on the audiokarma forum and After cleaning every single pot and switch in the machine It was still acting up. however, the pots and switches are a lot less noisy.

What I really need to know how to do is test the capacitors properly to see which ones are bad. some are oviously not in good shape as they are leaking and causing a mess all over the board, and others are bulging. My multimeter has a setting for "uF" that looks exactly like the micro farad unit on the capacitors but I dont get a reading when I test them.

And to ttw:

I live In maryland so I dont know If I would be the best place to get a spare unit. Even if it is for parts. Have you looked at craigslist? I think there is also several sites that have classifieds specifically for audio gear. Though I don't know them off the top of my head.

 

[sweetbeats]

If the caps are leaking or bulging consider them bad...no sense in testing them.

As far as testing, how long are you keeping the leads on the cap tails? You have to hold the meter test leads on the cap tails for a bit while it charges the cap. Make sure you have the polarity of the leads correct on the cap for polar caps...+ to + and - to -. You are right to question testing methodology. Testing the capacity of the cap generally just tells you if it has driften in capacity. The more definitive test is to get an ESR meter. Google that. But, again, if it is leaking/bulging its done.

Are there relays? You might have a dead relay.

Consider getting your caps from someplace like Mouser. Probably cheaper and better quality, though local is handy.

Substituting values...caps do different things. Sometimes the capacitance value is critical like in timing circuits. Donzt just assume you can go bigger. Unless you understand what you are doing it is best to keep the stock capacitance value, but you can go bigger on voltage as long as the can fits.

Hope that helps.

 

[samth3mancgp]

Hmm.. My multimeter does not seem to be testing them even after I keep the ends on the leads for ahwile. I tried it with one from the unit and with a brand new one. I'm not sure how long it's supposed to be there. My multimeter is an EXTECH instruments 380771 "Autoranging DMM". Maybe this isn't what I need in order to test it properly.

Thanks for the info. It's good to know about the capacitance and voltage "rules" for this equipment. I don't know how to tell whether the timing is important in these circuits so i'll just stick to original specs.

I don't think that this has relays. I'm not sure how to check that either. I was told on another forum that it could be a fuse, but I have not been able to find a fuse anywhere on this model either. the Australia model had one right next to the power jack but this one has none.