7A Matchbox...popping

Allen · From: Littleton, CO USA

When I first turn on my Goodrich 7A (about 1 yr. old) there is a lot of low level popping, followed by some very LOUD pops, heard through my Nashville 1000 amp. The guitar sound is intermittant or not at all. I sometimes have to "tap" the side of the 7A to get it to settle down, turning the 7A off and on sometimes will work. Unplugging and replugging the cables will sometimes work. What I am afraid of is doing damage to my amp if I forget to turn the gain down.
Talked to the Goodrich folks...They said it sounded like a bad battery........Changed the battery to a known good one....No help.
After a few tries of the things mentioned it seems to settle down and stay stable.
Anyone else had a similar problem? Or have any ideas before I send it back.

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Allen Harry
Mullen D-10, 8 & 6
Nashville 1000

[This message was edited by Allen on 21 April 2002 at 09:30 AM.]

Jim Smith · From: Midlothian, TX, USA

A while back I found a couple of broken solder joints in an old Goodrich box that were causing the same intermittant noises you're talking about. A quick resolder job got everything calmed down.

Cartwright Thompson · Posted 21 Apr 2002 5:42 pm

I had asimilar problem with a Matchbox. I found that "re-tensioning" the battery connections fixed it. Just bend the tabs on the battery connectors so they hold the battery tighter.

Terry Downs · From: Wylie, TX US

Yes, I have had loose battery contacts in my Match Bro. 9V battery manufacturers don't hold their (+) male posts to a tight tolerance. Some batteries posts tend to spread the female contact on the battery clip outward. When other batteries are subsequently used, the damaged female contact does not have adequate retention. You can usually spring them back. They are made of chrome plated berillium copper, so they usually resize reliably.

The 7A batteries are in series to make an 18V source. Since the op-amp runs on a single supply, the output runs at about the center of the supply with no signal (which is 9V). That output is DC blocked with a series capacitor. When the power is applied, the transient from 0 to 9V is coupled thru the capacitor resulting in the loud pop.

It still could be a broken solder joint too, but the battery clip would be a likely first start.

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Terry Downs
http://nightshift.net
terry@nightshift.net

Jim Bob Sedgwick · From: Clinton, Missouri USA

I hate to jump in here as I am electronically challenged. Just a thought: I have one of these units. Make sure the nuts on the input jacks are tight as I think these act as part of the ground. Mine came loose and I started having the problem you are describing. I tightened them back with a pair of pliers - problem solved. This might help

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