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Yamaha C-4 starts playing after a few minutes

R

rhgbg

New Member
Dear All,

First of all I want to wish to everyone Happy New Year fulfilled with health and happiness!

For the holidays finally I managed to get one set of dreamed: Yamaha C-4 and M-4.
The condition of both units is not mint but it is also not bad at all.

My whole setup now is: PC -> USB DAC -> C-4 -> GE-7030 -> M-4

Several days ago most probably a problem with the preamp started:

When I turn on the units and start playing music, the sound is coming out of the preamp after few minutes.
I am suspicious that the problem is in the preamp because there is no signal coming to the equalizer during this period.
The problem is only present in cold start (switched off during the night).
After a few minutes the signal is back and all units are working without any other issues. After that if I switch all of them off and then on again - everything is working instantly.

I tried to change the audio source - phone, mp3 player but same results. Next step is to remove the EQ from the setup to check if the problem is coming from it.

Thank you in advance for all ideas and assistance.
Best wishes!
 
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Welcome aboard..
rhgbg said:
the sound is coming out of the preamp after few minutes.
Click to expand...
Trouble shoot the muting circuit of the C- 4. There are 3 small capacitors, one of which is a 33µf/16v. ( C313 ) It is violet colored with red text printed on it. .. These are almost always dried up..It is responsible for the RC time constant delay time to energize the muting reed relay.RY301.

upload_2023-1-7_13-40-58.png
 
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avionic thank you for the fast response.

As follow up this morning I removed the EQ before start the units and the result was the same -> sound was present after 4 and a half minutes.

Now I will order a new condenser. I know that maybe is best to choose Nichicon, Elna or Rubycon electrolytic.
I am also thinking of full recap set but just don't know from which site is best to choose.

Just one more question because when I checked in the part list and 33µf/16v was pointed as number C313 and C316 is 2.2µf/25v

C313

C313

  • Media owner rhgbg
  • Date added
 
General advice is to fix the immediate problem before starting on a reconditioning/rebuild. If you want to rebuild it, by all means get the whole kit, but fix the immediate problem, then do the recap.
 
Thanks @avionic , i just submitted the order for the capacitor you suggested.
I was curious to understand from the OP if that replace solved his issue.
 
Hello, everyone.
First apologies for late reply. I didn't forget about feedback.
It was extremely busy year for me and I didn't have time for any of my hobbies.

Today I found few hours to open and change C313. Unfortunately still no sound. Even waiting for half an hour it is not starting to play.
 
Just to be sure that I changed the correct one, below is a picture and in red circle is the capacitor I have changed.

EDIT 1: The three signal lamps are working including the mute one. When I press the switch the lamp is going ON and OFF. For additional information the lamps are changed with Leds.
EDIT 2: Just looked the solder joints on the PCBs, my personal opinion that are not in bad condition. Found just two suspicious (re-soldered), but same situation.
EDIT 3: No signs of cracked pcb traces but will double check again.
 
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Look at the solder connections for TR621.. The TO-220 on the little heatsink in your photo. next to the circled cap. This is the relay driver transistor. It runs hot normally. It has a tendency to unsolder itself over the decades. :biggrin: I remove this transistor and reapply new heatsink compound. Using a little Permatex to fasten the heatsink to the circuit board.

Wouldn't hurt to reflow some new solder on the transistor at least.

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avionic, thank you again for help, understanding and patience with this case. Later this week, or latest during the weekend I will manage to check these points and write back the result.
 
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