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Topics - markorock37

Amplifier Discussion / Marshall VS100R transistors
March 01, 2024, 12:34:07 AM
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.
Amplifier Discussion / Hartke HA5000 biasing
June 06, 2023, 02:29:18 PM
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?
Amplifier Discussion / Hartke HA5000 tripping relay
December 05, 2021, 05:20:23 PM
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?
Tubes and Hybrids / Plush PRB 1000S dead
July 04, 2015, 01:48:40 AM
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?
I have a Peavey XXL (solid state) amp on the bench. Sounds great until you flip it to the Ultra channel then its squeal mania. It happens across all volume, gain, and eq levels and with different guitars, cables , etc. The issue is in the amp, in the Ultra channel only. The squeal goes away when your actually playing but as soon as you stop its there piercing your ears. Where should I start? I plan on getting it hooked up to my oscope today to see if I can see it.
Amplifier Discussion / Bassman 400 power issue
May 06, 2013, 01:04:08 PM
I am working on a Fender Bassman 400 ss bass head, its is blowing voltage regulators to bits. I replaced the 7815 and 7915 regulators and it blew 'em again. I have now replaced them once more along with all the diodes nearby. Instead of lifting one leg to test each I just went ahead and replaced all D100-111. Q102 was also blown and replaced. Ready to start it up on the limiter, anything else I should check beforehand?
Amplifier Discussion / Upping caps Peavy M2600
March 02, 2013, 12:05:37 AM
I have a Peavey M2600 power amp on the bench right now with low output. Guessing the main caps are shot. They are 5000uf 55v. Having trouble finding these but I do have some 6800uf 80v will those be okay? Thanks.
Amplifier Discussion / Reducing transformer voltage
June 04, 2012, 08:23:11 PM
Building a solid state guitar amp, everything is ready to go except my rail power is too high. I'm running 52 volts and would like to get around 25-30 volts. I'm using a 36 volt power supply w center tap into a full wave rectifier and two 2200uf 50v caps. What's my best solution? Thanks
Building a chipamp based on a LM1875. I'm using 2200uF caps in the amp circuit and a 34.5vac transformer. Really the only question I have is what size filter caps to use after the rectifier.
Amplifier Discussion / Supplier for IRF230's?
March 09, 2012, 02:38:52 PM
The only place I found any IRF230's in stock they are $13.49 a piece, any better sources out there? I need 4 for a Megabass head.
Amplifier Discussion / Line 6 Spider II not lighting up
February 09, 2012, 07:30:31 AM
I am trying to repair a DOA Line 6 Spider II 210, amp powers up, I can hear the speakers have power, so the power amp section is working. However, none of the lights are coming on and when I tested the cable connector goint to the preamp board no power was present. Transformer checks out fine, and all resistors on the power supply board are good. Bridge rectifier is conducting one way only like its suppossed too. The only thing I question is the little ST 2N 5401 transistor being good on that board. Anyone have this issue with these amps and what should I be looking for?
Schematics and Layouts / SUNN Stage Lead power issue
December 20, 2011, 11:19:34 AM
Picked up a Sunn stage lead for next to nothing. Has power but no sound. Found an open 680K resistor which I replaced. When I powered it up it fried one of the power resistors on the board. I couldn't find a schematic for it anywhere so anyone had any luck with these?