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Old 22nd Aug 2019, 9:47 pm   #1
Nickthedentist
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Join Date: Jan 2005
Location: Oxford, UK.
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Default Pye 1004 (Transistor Black Box) amp faults, help wanted please

Hello,

I bought this late-variant (c. 1964, BSR UA15 deck) Black Box cheaply, as a non-worker with the mains lead chopped off.

The manufacturer's data is on Paul's discs. It uses 7 Newmarket transistors, all DC-coupled except for the first one.

The amp is complete and never seems to have had any attention. However, F1 (1A) in the -25V DC supply is open circuit.

Quiescent consumption is stated as 15-30 mA. But powering it from my bench supply set to 25V and limited to about 60mA results in the bench supply's overcurrent protection operating and its ouput voltage dropping down to about 8V. Nothing looks burnt and there are no obvious shorts.

What tests should I do next, please? Transistor amps aren't my forte!

Many thanks in advance,

Nick.
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