Tube Amps / Music Electronics
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|previous: Andy I have a small Gorilla solid state ... -- 8/31/2004 3:02 PM||View Thread|
|9/1/2004 12:33 AM|
|Enzo||Re: Gorilla GG20|
All the little practice amps are essentially the same. There is a 5 leg chip on a heatsink - probably a TDA 2030 or 2040. That is the power amp. And there is usually one op amp of the 4558 variety.
Look at the speaker cone. When the amp turns on, does the cone move one direction and try to stay there? That means DC on the speaker. Or measure across the speaker to see if DC is there. If DC, then the TDA2030 is blown. That is the most common failure. Loud hum and no signal.
If the thing is not blown, and the volume turns down the hum, try this. If you touch pin 1 of the TDA with a screwdriver or maybe your meter probe, some hum should come out the speaker. If it does, the TDA os probably working.
SOmetimes the op amp fails. Pins 1 and 7 are the output pins. DC on either is a bad sign for them.
Most other repairs involve the front panel. Check the solder under the jacks and controls. When amps fall on their face, they often break the controls. Pull it apart and look at the controls. Inspect to see if any control has a cracked or broken wafer. Remove the control from the pc board and check it with a meter if in doubt.
|Lee I just fixed a pair of Drive bass a... -- 9/1/2004 1:50 AM|