Anyone familiar with SS amp repair?

M

mikeyen

Inspired
I'm wondering if anyone familiar with SS amps can help me out here: accidentally dropped the SLA2 while moving it around a few weeks ago. The ART is built like a tank - the rack ear is bent slightly, and otherwise looks and works just the same. I have, however, since noticed a very slight hum even when nothing's plugged in. Does this sound like something a tech can easily fix, given that SS amps seems to be mostly PCB boards? Pay the tech $50 to take a look, then being told "no can fix" is not my idea of a fun afternoon. :lol:

Thanks.

Mike

UPDATE: Problem solved - one of the wire was touching the transformer. See post below.
 
Before going to a tech I would suggest opening it up yourself and making sure all of your screws are tight, sometimes PC boards are grounded to the chassis through the metal standoff's they are screwed onto. The amp should of course be unplugged while doing this!

Also check to make sure all connectors are seated properly and take a good look to make sure you don't see any cracked components. Also the SLA-2 uses Phenolic PC boards which can crack easier that FR-4 (fiberglass) boards so it's worth checking for board cracks too.

Good luck and let us know what you find.
 
HAMERMAN409 said:
Before going to a tech I would suggest opening it up yourself and making sure all of your screws are tight, sometimes PC boards are grounded to the chassis through the metal standoff's they are screwed onto. The amp should of course be unplugged while doing this!

Also check to make sure all connectors are seated properly and take a good look to make sure you don't see any cracked components. Also the SLA-2 uses Phenolic PC boards which can crack easier that FR-4 (fiberglass) boards so it's worth checking for board cracks too.

Good luck and let us know what you find.
Click to expand...

Thanks a bunch for the tips. Unfortunately, I wasn't able to find anything out of the ordinary - checked all the connections, make sure the screws are tight, and there were no visible cracks. I did notice that the hum is slightly louder on channel 1 vs. channel 2, and the hum actually decreases slightly as the output volume is turned down (still with nothing plugged in). :/

Mike
 
Is the hum present with only the amp connected to speakers, with no other devices connected, or just when another device (ie. Axe Fx) is connected also?
 
axel said:
Is the hum present with only the amp connected to speakers, with no other devices connected, or just when another device (ie. Axe Fx) is connected also?
Click to expand...

The hum is present even when nothing's connected to the amp's inputs, and like I mentioned, it fluctuates if I move the output volume knob around.

Mike
 
Could be a number of things...

Cracked PCB
Cracked solder joint
Loose ground

Here's something that's easy to try...

Plug a short instrument cable (sheilded) into the inputs, one at a time.
Short the center of the cable phone plug to the outer part of the plug (ground).
See if the hum goes away.

This will tell you if there is a problem with one of the input grounds. Shorting the inputs will not cause any damage, in fact, when your cables are disconnected, the input jack center conductor will normally be grounded internally (to prevent hum).
 
axel said:
Here's something that's easy to try...

Plug a short instrument cable (sheilded) into the inputs, one at a time.
Short the center of the cable phone plug to the outer part of the plug (ground).
See if the hum goes away.

This will tell you if there is a problem with one of the input grounds. Shorting the inputs will not cause any damage, in fact, when your cables are disconnected, the input jack center conductor will normally be grounded internally (to prevent hum).
Click to expand...

Thanks - I just tried it, but shorting the inputs doesn't make the hum go away.

Mike
 
mikeyen said:
axel said:
Is the hum present with only the amp connected to speakers, with no other devices connected, or just when another device (ie. Axe Fx) is connected also?
Click to expand...

The hum is present even when nothing's connected to the amp's inputs, and like I mentioned, it fluctuates if I move the output volume knob around.

Mike
Click to expand...

The fact that the level of the hum goes up and down with the volume control indicates the source of the hum is before the volume control, and not in the output section. It is most likely a bad ground connection, but finding it would be a challenge if you're not trained in electronics troubleshooting. About the only thing you can do without the proper equipment is open it up, turn it on, and using a non-conductive stick (ie chopstick), flex the wires and circuit board to see if the hum is affected. This is one method of checking for broken connections...

DO NOT touch anything with your fingers or any conductive tool.
 
axel said:
The fact that the level of the hum goes up and down with the volume control indicates the source of the hum is before the volume control, and not in the output section. It is most likely a bad ground connection, but finding it would be a challenge if you're not trained in electronics troubleshooting. About the only thing you can do without the proper equipment is open it up, turn it on, and using a non-conductive stick (ie chopstick), flex the wires and circuit board to see if the hum is affected. This is one method of checking for broken connections...

DO NOT touch anything with your fingers or any conductive tool.
Click to expand...

Thanks - since I have only basic knowledge in electronics, I think I'll just leave it alone for the time being, and bring it to a tech at some point. Now that we've narrowed down the source of the issue, I feel better about bringing it in. Appreciate everyone's help!

Mike
 
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