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.

I have a box of wood scraps, theres always a block in there to support whatever I'm working on. Nice to know I'm not the only one!

It's actually a nice fat trace pcb, two boards, one for the preamp and one for the poweramp. I can fix the burnt trace. Whoever was in this thing also raided all the electrolytics so I'd bet this thing has been doa for quite some time. The rectifier looks fried as well. It's all rebuildable, just not sure my customer is going to like the price! Classictone has a tranny for $72, probably not as good as what was in there but should work. Looks like an old Kustom tuck and roll amp, but it's all tube. There was 2 of the 4 power tubes still in it, different brands too, I bet they just stuck whatever in there and fried it. I also heard they stole from Fender and Peavey, went out of business in '74.

I have a Plush PRB 1000S come in to the shop, no OT, no tubes, a burnt choke, no fuse holder, and a burnt trace on the power tube board. Off the bat I'm guessing a Showman OT may work? Also wondering what the preamp
tubes were? A schematic would go a long ways, I read it may be a Showman or Twin copy?

Did it to multiple guitars. It IS the amp. That's why its on its way out of my shop. Peavey should have never put this much gain on tap.

Well for starters, its not my amp, nor do I play with gain on "10". It IS unrealistic to play this amp cranked like that. I went through and cleaned any pots contributing to any noise. I did get the amp back to a controllable state. Again it only feedsback with that squeal if the switch on the Ultra channel  is set to Ultra or the Lead channel is set to High Gain. Both functions put it into high gain territory which normally is associated with feedback. After cleaning the pots I was able to play with the gain around 3-4 oclock, channel volume around noon and using the master for overall volume before I got the nasty squeal.  I did have to stand at least 5-6 feet away to be controllable. Cleaning the pots was a major improvement. Perfectly quiet on any other setting. No results from the chopstick test. I put it back together and sending this one on its way.

With a shorted plug inserted it the same high frequency squeal. Only does it with the voicing switch set to high gain. I went through and cleaned all the jacks, and all connections inside are solid. No obvious component failure. I cleaned all the ultra channel pots. Testing afterward the ultra channel is no longer squeling. But when I turn the LEAD channel gain to 10 - while on the ultra channel there it is squeel. I'm going to clean that pot and see if it makes a difference. Also no difference with effects loop jumpered.