troubleshooting Harvard amp

fluffhead · 9th March 2009, 05:26 PM

Hi, I have an old Harvard Reverb (~1980 - one of the first solid state amps by fender, a little practice amp) and it is having some troubles. I am looking for a little troubleshooting help.

It plays great for 30-40 min (depending on volume and effects going into it) but then it gets really distorted for a little while and eventually dies. It is then out of commission for an hour or so.

The three options I can think of are:
1) transistor is overheating
2) transistor is fried and needs replaced
3) caps are too old and need to be replaced

Any suggestions on where to start or how to determine which on of these is my problem? I am handy with a soldering iron but don't want to replace parts that are ok.

Thanks for the help!

VictoriaGuy · 9th March 2009, 06:19 PM

I'm not that familiar with solid-state amps (I have a tube Harvard), but another possibility is that a so-called 'cold solder joint' has developed on the circuit board over time. As the amp heats up, things move a bit and the contact becomes intermittent.

You can get spray cans of 'Cold Spray' for troubleshooting such problems. On a simple board like the Harvard, it might be as quick to re-solder the board. It just takes a quick touch with the iron to each joint, usually.

Cheers
John

fluffhead · 9th March 2009, 06:36 PM

good idea, I'll give this a shot tonight

9th March 2009, 05:26 PM	#1
fluffhead diyAudio Member Join Date: Feb 2009	troubleshooting Harvard amp Hi, I have an old Harvard Reverb (~1980 - one of the first solid state amps by fender, a little practice amp) and it is having some troubles. I am looking for a little troubleshooting help. It plays great for 30-40 min (depending on volume and effects going into it) but then it gets really distorted for a little while and eventually dies. It is then out of commission for an hour or so. The three options I can think of are: 1) transistor is overheating 2) transistor is fried and needs replaced 3) caps are too old and need to be replaced Any suggestions on where to start or how to determine which on of these is my problem? I am handy with a soldering iron but don't want to replace parts that are ok. Thanks for the help!

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9th March 2009, 06:19 PM	#2
VictoriaGuy diyAudio Member Join Date: Dec 2008 Location: Victoria, BC	I'm not that familiar with solid-state amps (I have a tube Harvard), but another possibility is that a so-called 'cold solder joint' has developed on the circuit board over time. As the amp heats up, things move a bit and the contact becomes intermittent. You can get spray cans of 'Cold Spray' for troubleshooting such problems. On a simple board like the Harvard, it might be as quick to re-solder the board. It just takes a quick touch with the iron to each joint, usually. Cheers John

9th March 2009, 06:36 PM	#3
fluffhead diyAudio Member Join Date: Feb 2009	good idea, I'll give this a shot tonight

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