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Valveking MK II 100 Watt Guitar Amplifier Repair, No Sound, Can it be repaired???

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For entertainment only! Please watch warning in video and text warning below.
‪@SpencersMountain‬ A quick departure from my normal videos. I have messed around with electronics since my younger days. Can't play guitar for crap, but consider broken tube amplifiers like a puzzle that needs to be figured out.
This Peavey ValveKing MK II was found broken and likely headed for the landfill. It just costs too much to have these things repaired...unless you can fix it yourself!!! Knowing how things work is the essence of DIY.
The required warning: Guitar amplifiers should only be repaired by knowledgeable persons with proper equipment. Guitar amplifiers normally contain stored voltages that could KILL you. Do not attempt to duplicate anything you see in this video. Seek professional help for things you do not understand.
Amplifier troubleshooting, disassembly, troubleshooting, testing, variac and dim bulb testing, circuit board removal, desoldering, use of solder sucker, switch and resistor removal and replacement, soldering, assembly and play testing.

Опубликовано:

19 янв 2024

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Комментарии : 3

@Bassguitarist1985 5 месяцев назад

Great job repairing. Glad to see others using this head. For the XLR MSDI out, did you see an isolation transformer or two coupling caps? Just discovered a flaw in the grounding plane circuitry with the help of my engineer friend at Peavey. I'll be making a video on it soon.

@SpencersMountain 5 месяцев назад

Thank you. I do not see any isolation transformer in the XLR circuit. Signal is via C52 a 2.2U 100v cap and series dropped though resistors and a couple inductors. C201 a 2.2U 50v cap couples to pin 1 of the jack and C202 a 2.2U 50v cap on pin 3 to ground. C201 is essentially the output coupling at the jack. Not sure what you are looking for? This is a somewhat complex amplifier and the schematic is a challenge to follow....even with many, many years of schematic reading. Finding a part on the schematic and locating the physical parts can be an adventure. Power transformer and output transformers are only represented by pin connections no parts in the drawings. If you experience a hum issue, check out this XLR patch video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-DRn-g-eYyN8.htmlsi=J8EQADdoINxuubwN

@Bassguitarist1985 5 месяцев назад

@@SpencersMountain haha thats my video! I'm about to release an addendum to that video as I have learned new information. C201 couples to pin 2, and C202 couples to pin 3. Pin 1 ties to Chassis/Earth. The isolation transformer that was in my amp was the wrong type, that was the first problem. The 2nd problem was in the Grounding plane design between the main PCB and the patch board. Yes this amp is complex. The XLR circuit has all the inductors/resistors to match the response curve of an SM57 microphone placed 1 inch next to the cone of a speaker. I have a friend named John who works down at Peavey. He's one of the top engineers there. Helped me solve the issue. He didn't design the MK II head but he found a flaw in the ground plane bonding the other engineer/designer missed plus the wrong isolation transformer. Guess they threw in whatever they had on hand. Be on the lookout. Here I thought I was the only one making repair videos on this amp!