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Do Darlington Power Packs Age?

yosl

yosl

Active Member
The full question is, "do Darlington Power Packs Age like dedicated output sections"?

I have a JVC JR-S201 with dual darlington power packs in the output stage (one per channel). I've owned the S-201 since new (1978) and it was doing yeoman duty with one of my sons in his stereo set-up. Went over recently, powered up the system and things sounded pretty uninspiring ..... flat listless. Far from what I know it's capable of when this receiver punched well above it's weight in it's output class.

Recognized the old girl needed a major refurb and switched it out. The question is what to do in this refurb? The output board is normally one of the first targets for a recap but being darlington power packs, that's really a plug and play situation. Replacement new power packs are still available.

Thoughts as to the power pack replacement. Fully aware that the remainder of the receiver may well need a complete recap as well once it's been gone through.
 
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I have no experience with Darlington power packs ageing but from what I've seen in restoration/repair videos and threads, the heat generated by them creates expansion/contraction cycles and may deteriorate or even crack the solder joints on the PCB. So my first idea would be to re-flow the solder joints at all the output devices and also make sure the screws to the heat-sinks are tight and snug.
I would also check out rail voltages. From then on, I would expect to hear from experienced service men about the ageing possibility.
 
If it is acting up in both channels, it is not the power paks. Could be the power supply or even something as simple as the pots and switches that need cleaning.

I have a Fisher amp which uses the STK Darlington power paks and it is still going strong today. Besides, I hear that any of those that might be available today might be fakes.
 
Just to clarify, there is nothing wrong with the receiver in terms of one or other channel cutting out or that it has noisy pots. It just sounds flat, lacking in oomph when at one time it could rock the house. Good suggestion on the speakers but they were wired in phase. Also thanks for the heads-up on the fakes. Will also check the efficiency specs for the speakers being driven, a set of 85 dB speakers could suck the life out of a relatively low powered receiver. All that said, can darlington power packs be refreshed or do they even deteriorate with age?
 
But of course ....duh..... I must have been having a senior moment! Will focus my efforts elsewhere including the power supply.
 
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