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Old 3rd July 2009, 01:53 PM   #1
trb4 is offline trb4  Italy
diyAudio Member
Join Date: Aug 2004
Location: Palermo
Question Power Supply Classic30

Hi everyone, i need to replace power supply transformer of a Peavey Classic 30 tube amplifier.
On the schematic (internet source) plate voltage is 332VDC, so the high voltage output of the transformer should be about 240Vac (secondary output 30Vac is connected to series heaters).
Unexpectedly, I measured the output voltage of the transformer actually mounted on amplifier and i read 290Vac.
What is the correct voltage? I have a wrong schematic? Can you help me?
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Old 7th July 2009, 06:24 AM   #2
Enzo is offline Enzo  United States
diyAudio Member
Join Date: Sep 2004
Location: Lansing, Michigan
What does that voltage drop to when fully loaded? The transformer will always read high when not loaded.

Can your Peavey distributor supply the factory part?

COnsider that the heaters of the four power tubes are wired in series - with a pair of 3 ohm resistors also in series - across about 25VAC of the transformer. And the preamp tube heaters are also wired in series across the 36VDC that resulkts when teh AC is rectified and filtered.

God luck finding a transformer with 240v and 25v windings.
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