100W bulb. DC was present with no load.

Looks like I'll have to wait until tomorrow to start testing this entire board.

I replaced the output transistors (TIP 142, TIP 147) and installed with the micas. Also replaced TIP29C and a J111 that were bad. Im getting a low brightness (not really dim) on my bulb limiter and a buzz/hum through the speaker. No guitar signal coming through. Tested for DC at the output jack and it was at 33V! Shut it down and started testing components. All diodes test good, and all capacitors test good. Checked some resistors in areas i felt were critical and haven't found anything off. Do you think one of the TO92 transistors is at fault? Or did I blow an output again?

There is some metal exposed on the back of these newer transistors. I think it will be best to use the insulators.

It originally had transistors with the metal tab. Only held to the heat sink with a surface clamp. The replacements I have are the newer type.

According to the schematic not grounded. I'll order the spacers.

Well the original transistors were BDV65 and BDV64 and there was no spacers. However the amp was worked on by a previous tech and he deemed it non-repairable, which of course is not the case. TIP 142 and TIP 147 are suitable replacements, I'm just confused as to if that spacer was there previously or if now with the transistor sub it may be required. I'll check the schematic to see if I can tell if the collector was originally grounded.

So...I have a Marshall VS100R combo on the bench. Blown transistors, and also a bad J111 (T16) and a bad TIP29CH (T4). I already have the output transistors TIP 142 and 147s. Do these equivalent transistors need the mica spacer? I couldn't find the info from the datasheet.

That's the schem I have also.

I have a HA5000 on the bench. After checking the bias at TP1 on both modules, I have one at 36mv and the other at 91mv. Anyone know what the recommended setting is for this amp?

Finally I had a chance to change all of the electrolytics on the offending amplifier board. That was it! The amp is working great now and sounds good too. Thanks Enzo for pointing me in the right direction. Your help is always appreciated.

Mark

Sometimes it shuts off sooner. I was thinking the aged electrolytics may be causing the problem. I'll change those out and see what happens.

Nothing is getting hot. But yes I measured high dc on the low side .195v. High side is at .053V but that side works and that seems alright.

Working on a Hartke HA5000. Had 3 blown power transistors and both drivers on right amp. Replaced those with exact part numbers and also replaced the six .47 ohm resistors. The amp works fine in mono mode and in bi-amp mode through the high output jacks. When plugged into the low output jacks the relay opens after 30 seconds or so and cuts the sound. I can't find any info or setting the amp (there is 2 trim pots on the board) just a schematic. Both channels have equal B+ voltage going to them. Anything else I should check?

Upon further testing, I discovered the power transformer is shorted as well and will result in too much investment into this basket case of an amp. Looks like another bites the dust.