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Yamaha A1 restoration 2021

Think it was these red fusistors that smoked.
Likely to be anything else affected?
What steps next?
May have to call it a night but please feel free to send any instructions, thoughts on best way forward.
Thanks again for help so far.

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Looks like R119 and 120 10Ω/2W Severe oscillation.?

See if they are still 10Ω ..If they are , reinstall the two 330 Ω resistors.

Next power up with a dim bulb.. Just in case..
 
Thanks Avionic.
Hopefully will attend to this tomorrow, thanks for the guidance. Fine to leave the 10 ohm resistors in place if they test ‘ok’ ?
 
Checking over the Drive Board left channel.. discovered a disconnected Grey wirewound cable..
Do the audio symptoms (static-like loud noise through the left speaker) tie in with the grey cable detaching?
 
In situ and with power off, the two red metal oxide fusistors (10ohm 2P) read 10 ohms. Despite the severe oscillation, fine to leave them in?
 
Can’t believe it.
Put it all back together. Switched it on, it played source music very nicely for maybe half a minute. It was at low volume, I turned up the bass and a couple of seconds later heard the same static-ish burst come through the left speaker. Immediately turned it off.
 
Recall another poster with A-1 FET issues, voltages were all over the place. The OP reflowed solder on the FETs and all good. Voltages on my A-1 were a mess also then one day all good (nice amp). I've reflowed those solder joints.
 
mbz said:
Recall another poster with A-1 FET issues, voltages were all over the place. The OP reflowed solder on the FETs and all good. Voltages on my A-1 were a mess also then one day all good (nice amp). I've reflowed those solder joints.
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Yeah I cleaned the leads of the Sk's as they had black corrosion on them and all was good after.

But The Adaptor board using the JFE2140 worked out well from my short term testing.

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I wanted to test them with out the vertical Yamaha daughter board , but haven't gotten around to it.



Athanasios
 
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Hifibythekg said:
Well done @Nashou66
So good that if you ever needed to replace the discontinued 2sk100’s again in another A-1, would you happily go down JFE2140 route?
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So far I would say yes. I can tell no difference in listening switching the balance from the original channel to the new 2140 channel.

Nashou
 
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