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Technics SU-V6 Re-capping Question

M

mdares

New Member
Thank you in advance for reading - I have a Technics SU-V6 that I am recapping (some distortion in the right channel, no bass in the left channel, I have confirmed it is the unit causing the issue. It was purchased in 1981 by my parents, and so I expect the caps are bad (none have failed obviously).

I have some questions:

1. 8 (3 pairs and two single) capacitors I removed from the board differed from the values referenced in the service manual. Two of these substantially - which value would you use to replace them?

2. Any thoughts on the goop on the ceramic capacitor in the attached photo?

3. Would you have any concerns replacing the 8200uF/56V caps with 8200uF/63V caps? I think and it seems like google agrees that this should not create any problems; but I would like to back that up...

4. Disassembly has been a pain in the butt and my only testing equipment is a multimeter. What components would you consider replacing proactively?

5. Several of the switches and selection inputs have some problems (Deoxit fixed the pot-based inputs). Specifically the phono selector will sometimes cut the left channel entirely (these are the rotary switches with the metal bands attached). I am not sure how to even look these up. Any recommendations on cleaning these (tooth brush and deoxit?).

Thank you for any help - I browse the forum all the time, excited to actually participate.

20221018_102530

20221018_102530

  • Media owner mdares
  • Date added
 
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Items 1, 2 and 3: It's always wise to replace with the same values as originally fitted, unless a service bulletin suggested changing the values. It's never a problem to increase the voltage rating for replacements, as long as the physical size does not create issues. The goop is likely glue used to keep things from moving (primarily a shipping concern).

Item 4-replace any small transistors that are known faulty over time, or as suggested in service bulletins. There are several threads concerning known offenders in these forums. Here's one: https://audiokarma.org/forums/index...ilure-prone-whatever-and-replacements.731653/ Also, replace any transistors or resistors that have corroded legs. Discoloration over time is not an issue, but fuzzy green stuff means trouble.

Item 5-use some spray on contact cleaner, that is plastic safe and non conductive. It will evaporate quickly, and the idea is to spray somewhat liberally into the switch to flush out crud, then treat with Deoxit 5. You can use a pipe cleaner or similar, to remove crud also, but be very careful, as it's very easy to bend a wiper arm. If you are not successful with these techniques, remove the rotary switch and very carefully disassemble, clean and reassemble.
 
mdares said:
2. Any thoughts on the goop on the ceramic capacitor in the attached photo?
Click to expand...
You should remove the glue from the board and from any components. As above replace components that have green fuzz on them, and those slathered with the stuff can often be cleaned up successfully - but every trace of glue should be removed.
 
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Also I would clean the boards themselves thoroughly before starting. I use a paint brush and denatured alcohol. I buy it by the gallon at HD . Use it liberally with he brush and then flush it away after.
Working on a clean board and components makes it much easier and more pleasant .
It also helps in identifying parts etc.

Good luck !

Athanasios
 
Thank you everyone - it looks like none of the problem transistors are on this board, so I am going to just go ahead and re-cap it and clean it. Out of curiosity - if anyone knows someone that has one of these units I would love a pic of C552 and C554.

Here is the issue I have with the worst capicitors:
  • C552
    • Spec: 33uf/50V
    • Installed: 3.3uF/50V
  • C554
    • Spec: 3.3uf/16V
    • Installed: 33uF/6.3V
 
1) go with whats in the unit if it was working properly. Schematics sometimes are wrong. Value off by 10 sounds like a decimal stuck where it doesn't go. The voltage might be a concern, so maybe swap that 6.3v cap for at least a 16 (I honestly don't even buy anything under 50 volts) and call it good.
2) looks like glue
3) no problem at all
 
Not in my driveway, but definitely at some point in its journey... Most of them look okay, but I would not trust a single one.
 
All back together with two extra screws, turned it on and no sound.... opened it up and the missing screws made the grounding connection from the board to the frame :confused:.. Two more screws and it sounds amazing! Thank you all for the help.
 
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