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Vintage threads from the first ten years

Marshall 1987

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1/12/1998 9:55 AM
Brian Stone	Marshall 1987 Does anyone have the following info? The voltage on the power supplies secondary? Voltage on output primary & secondary? Voltage on the caps? Voltage on the choke? Thanks, Brian

1/13/1998 11:48 AM
J Fletcher	I'm not certain what a 1987 is,but if it's a 50 watter then the high voltage will be around 450volts DC.This will appear on the center tap of the output transformer,the choke,the first cap after the rectifier.No dc voltage should be on the secondary of the output transformer.Hope this helps...

1/13/1998 11:55 AM
Brian	Marshall made a 50 watter and a 100 watter. Any idea what the 100 would be?

1/13/1998 1:22 PM
J Fletcher	I think the high voltage for the 100 watter would be around the same,450 volts.I'm not that familiar with voltages inside Marshalls though.Other people on this board have more experience than myself.

1/20/1998 6:40 PM
dave	100 watt marshall with el34 power tubes - should have B+ voltage of up to 530v. 100 watt marshall with 6550s should have B+ of around 450v.

1/13/1998 12:45 PM
Doc	The Marshall with circuit number 1987 is probably the best liked 50w Plexi panel amp. It has dual channel inputs, with separate cathode resistors/bypass caps. One channel is normal, one is bright (0.68uf bypass cap). There's a nice schematic on Joe Piazza's page, at www.servtech.com/public/piazza/joepage/, but it has no voltages listed (I wish it did).

1/20/1998 6:36 PM
Dave	According to voltage charts in the "History of Marshall" by Doyle, the power transformer of the 50 watt marshall maps PT secondary produces a voltage of about 400 volts (380 plate voltage, 390 screen voltage). The voltage on the choke, filter caps and output primary should all be close to or just under 400 volts, based on this chart, and assuming the PT is original.

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