Repair Bass Mark 3 300CHS

This forum is for discussions on all kinds of Peavey bass amplifiers.
Post Reply
Hellhoff
New Member
Posts: 1
Joined: Tue Jul 18, 2017 12:48 pm

Repair Bass Mark 3 300CHS

Post by Hellhoff » Tue Jul 18, 2017 1:09 pm

So. I am definitely a novice on electronics and schematics. But a poor musicians gotta do anyway, eh?

The Peavey Bass Mark 3(300CHS) stopped producing sound and instead produced a burning smell. Let it sit for a few days and this is what I found:

Image

By visual inspection and with the help of the schematic found here: https://peavey.com/forum/download/file.php?id=17120

...I've determined that at least CR15, R23, R15 and R39 are fried. I plan on replacing these as I know my way around a soldering iron.

However, I do not know enough to confidently measure the voltage in order to troubleshoot the circuit. Is anyone familiar with the design of this circuit? Are there any obvious things that I could look for with my multimeter/DVOM? Please forgive my lack of knowledge on the subject.

Any help is greatly appreciated. Thanks in advance!

User avatar
Enzo
Member
Posts: 9535
Joined: Fri Sep 12, 2008 10:24 pm
Location: Lansing, Michigan

Re: Repair Bass Mark 3 300CHS

Post by Enzo » Tue Jul 18, 2017 5:50 pm

First, clean off the soot. I usually grab a Qtip - well a bunch of them - and isopropyl alcohol. Swab the area, and most of the soot comes off.

Any of the circuit board that is actually charred must be removed. I grind such away with my Dremel.

Of course check, but considering what is burnt, I'd say it is a good bet your output transistors and drivers are shot. SInce CR15 is parallel the outputs, if they short, it makes CR15 appear shorted. THey do fail once in a while, but very rare for that diode to fail. The drivers are the smaller transistors on the little finned heat sinks.

Post Reply