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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 18th Apr 2018, 6:00 pm   #21
dave cox
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Default Re: Sugden A48 Mk2

Does it come out attached to the heatsinks ?

dc
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Old 18th Apr 2018, 6:16 pm   #22
zeagan84
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Default Re: Sugden A48 Mk2

It seems as if they can detach, although I haven't given it a go yet to see how much the thermal goop has become an adhesive.
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Old 18th Apr 2018, 8:35 pm   #23
Mooly
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Default Re: Sugden A48 Mk2

Try freezing the caps I mentioned (post #4). I was working off the other diagram when I mentioned those but you are looking for non electrolytic types. On your diagram they look like C1, C2, C3 and C11 and C14

The carbon composition resistors that got a mention earlier are well worth checking out to. Freezer again.

The carbon comp variety are those that look like that group of four next to the headphone socket in your middle picture in post #9.

Another thought is the preset used to set the midpoint voltage. The setting of this is not that critical. You could switch the amp OFF and then whizz the pot a few times from end to end to clean it. This is well worth doing. Then reset visually back to the same point. DO NOT alter the bias current preset without following the service manual set up procedure.

Diode K3 is worth a freeze as are diodes K1 and K2. All three of those diode should be able to be removed (as a test) without affecting the basic operation of the amp.
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