Need Some Amp Help...

[Jack Hammer]

Last month I found a SoundCraftsmen MA5002 amp of unknown condition in the basement of a building my buddy owns, original thread here. Today I finally went over and picked it up. I got it home and plugged it in unconnected to see what would happen. The "overload" light came on and the VU meter for channel A showed the needle at a steady 20 while the channel B meter didn't move any. Also it started making a steady medium pitched clicking about every two seconds, the sound is similar to flicking your finger against a thick glass bottle. Each time it clicked my lights dimmed so I turned it off and uplugged it. If we can get it working the plan is for my buddy to use at his place.

I'm looking for any advice on how to properly go about testing it, without worrying about damage to any of my other equipment and to find out what is causing the clicking and overload light to come on.

 

[selden]

The first thing to do is to unplug it and let it sit for a while so its capacitors lose their charge. Then open it up and make a visual inspection of its interior. Drawing that much current probably has resulted in some of its circuits cooking -- you are likely to see a region on one of its circuit boards which is much darker than the rest.

You also should try to get a service manual for it.

Note that these are just a generic suggestions. I have no experience with this equipment. Hopefully someone familiar with it will be able to provide more specific advice.

 

[chris357]

audiokarma is a good site for help on fixing older vintage equipment.

 

[Jack Hammer]

I'll pull the cover off tomorrow and see how it looks. I'll also take a look at Audidokarma and see what I can find.

I noticed that since unplugging it the channel A VU meter has stayed at 20. It was definately at 0 before I plugged it in. Does that mean anything bad?

 

[highfigh]

If the power meter moves with no input, it may mean the amp is oscillating. This means something is out of spec and as I have heard, "the difference between an amplifier and an oscillator is one or two part values".

If the needle stayed in one place, it usually means the paper scale has warped.

 

[TLS Guy]

Last month I found a SoundCraftsmen MA5002 amp of unknown condition in the basement of a building my buddy owns, original thread here. Today I finally went over and picked it up. I got it home and plugged it in unconnected to see what would happen. The "overload" light came on and the VU meter for channel A showed the needle at a steady 20 while the channel B meter didn't move any. Also it started making a steady medium pitched clicking about every two seconds, the sound is similar to flicking your finger against a thick glass bottle. Each time it clicked my lights dimmed so I turned it off and uplugged it. If we can get it working the plan is for my buddy to use at his place.

I'm looking for any advice on how to properly go about testing it, without worrying about damage to any of my other equipment and to find out what is causing the clicking and overload light to come on.

You won't fix that without a service manual, extensive test equipment and experience.

I can be certain the unit has deep serious problems.

It is only worth fixing as a vintage restoration project. If it is just an amp you need, it will likely be cheaper to buy a new one.

 

[Jack Hammer]

You won't fix that without a service manual, extensive test equipment and experience.

I can be certain the unit has deep serious problems.

It is only worth fixing as a vintage restoration project. If it is just an amp you need, it will likely be cheaper to buy a new one.

Not quite what I was hoping to hear, but not the end of the world either. At this time, I don't really have a need for this amp. I thought it might be nice to use it to power some other areas at my buddies house, but I do have a cheap amp laying around I can use for that. Another guy I know has some vintage gear, but knows little about fixing things. I'll see if he's interested in having it fixed and using it. If he is then maybe we can trade for something or I just might flat out give it to him.

Thanks for the advice to all.

 

[TLS Guy]

Not quite what I was hoping to hear, but not the end of the world either. At this time, I don't really have a need for this amp. I thought it might be nice to use it to power some other areas at my buddies house, but I do have a cheap amp laying around I can use for that. Another guy I know has some vintage gear, but knows little about fixing things. I'll see if he's interested in having it fixed and using it. If he is then maybe we can trade for something or I just might flat out give it to him.

Thanks for the advice to all.

You can download a service manual for your amp here. Cost is $25. Whoever works on this will need it. So that is the start of the cost of restoration.