Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: erokit on March 26, 2012, 10:02:33 PM

Title: Fried my power amp
Post by: erokit on March 26, 2012, 10:02:33 PM
When putting back together my gk 200rb after speaker repair, the connector for the power source fit the speaker out and fried the power amp. Read,and should have thought, that this kind of failure cascades. Tested out the power circuit trans and ordered the the parts.

I replaced the 4 power trans, and it tested out fine. Thought about replacing the two phase splitters, but (unwisely?) didn't. I also didn't replace the trans that feeds the PNP side of he power section (is that what is called the driver trans?)

After putting the heat sink back on and reassembling the combo, I had a short. The bridge rectifier was heating up, so I ordered the replacement for that. I already ordered the other trans I didn't replace previously. I also ordered extra in case I had problems.

If I was a pro I would check everything. Am I on the right track looking at bridge rectifier?
Title: Re: Help - bad move fried my power amp section
Post by: polo16mi on March 26, 2012, 10:30:43 PM
Hi there:

I´m not really know how to help you fix your amp, but at first step, im pretty sure that you´ll find usefull this Light Bulb Limiter, to save several component$$$.

http://www.ssguitar.com/index.php?topic=2093.msg17092#msg17092 (http://www.ssguitar.com/index.php?topic=2093.msg17092#msg17092)

I sure too, that you wait for a while here, and you get some more usefull help.


Title: Fried my power amp
Post by: erokit on March 28, 2012, 09:10:36 PM
 :o
When putting back together my gk 200rb after speaker repair, the connector for the power source fit the speaker out and fried the power amp. Read that this kind of failure cascades. Tested out the power circuit trans and ordered the the parts.

I replaced the 4 power trans, and it tested out fine. Thought about replacing the two phase splitters, but (unwisely?) didn't. I also didn't replace the trans that feeds the PNP side of the power amp (is that what is called the driver trans?)

After putting the heat sink back on and reassembling the combo, I had a short. The bridge rectifier was heating up, so I ordered a replacement. I already ordered the other trans I didn't replace previously. Ordered extra in case I had problems.

If I was a pro I would check everything. Am I on the right track looking at bridge rectifier?
Title: Re: Fried my power amp
Post by: J M Fahey on March 29, 2012, 03:57:06 AM
Hi erokit.
Problem is, you must replace all bad parts at once.
If you had, say, 7 bad ones, and replaced only 6; after turning it on, you won't need only the one you missed but many of the "new" ones too, because now you re-fried them.
1) google its schematic so we all can refer to the same parts,.
Or ask it from GK and post it here.
2) build a lamp bulb limiter (search this Forum) to avoid repeating catastrophic failures.
Good luck.
Title: Re: Fried my power amp
Post by: erokit on March 30, 2012, 12:55:17 AM
Working on my light bulb limiter. Saw that in my research.

Here's the power amp schematic.

Many thanks!
Title: Re: Fried my power amp
Post by: joecool85 on March 30, 2012, 08:51:01 AM
erokit, no need to post in two sections.  I combined the threads to keep things clean.

Good luck!
Title: Re: Fried my power amp
Post by: J M Fahey on March 30, 2012, 09:43:08 AM
Thanks God you found a clean readable schematic, with suggested voltage readings on it.
You'll have to check for shorts all transistor in the power amp and *maybe* replace the IC.
Don't worry, working slow and steady you'll solve it.