VintageKustom.com: Repairing Kustom Amps

Tue, 09 February 2010 22:04

cassent5150
Messages: 341
Registered: August 2009

Senior Member

I have severalK-100s and K-200s and cannot understand how these schematic voltages work. Seems every one of these 4 boards have the same problem and I can't figure it out. I'm hitting the collector Q 915 on this pc900 board at 40.5 volts and am supposed to be getting +8.74 at the base and +3 at the emmiter. The transistor (Q 915) is good so why in the blank am i only getting B= +2 volts and E= 1.5 Volts. Values with all controls full on, no signal and no load. Are we not checking values from chassis ground? If not where are we getting these values from? The PC900 I'm working on should be about new I've replaced every trasistor with nos I picked up from a surplus electronic store. I used nte replacements in a couple of places but for the most part I used exact part # replacements. There is no burnt resistors and all the caps seem to be good. All 5 diodes seem to be fine I did replace the cr 902 (the one mounted in the chassis clip) with the NTE 5801. Correct me if I'm wrong, but isn't the low voltage supply of these 2 boards PC 900 and PC 703 the same? Anyhow if anyone can help me understand that area of the board please help.

Steve C

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