American Viking

A guy brought me a GH100L today and wanted me to take a look at it and fix it up so he could maybe sell it. He said he purchased it for $100 USD because it was kind of busted.

The first thing I did was run through all of the simple steps like checking fuses and tubes, re-biasing the tubes and everything. After biasing (the tubes were running WAY too hot at first) the amp seem to have some new life and I saw a lot of potential in it but it seemed to sound very trebley and not have any low end at all even with the bass cranked. I've heard some Laney's before and was sure that this shouldn't sound so harsh. Some of the pots (presence, bass, treble) had a wierd feeling when you turned the knobs like at a certain point they felt harder to turn. These may be damaged because turning the bass knob from one to ten doesn't make much of a difference.

After that I put the older tubes he had in (the tubes that were in it when it was apparently damaged) per his request, and the fuse inside the chassis blew, I replaced the fuse, replaced the output tubes and when I turned it on again the resistor (1K5 5%) that jumps across pins 4 and 6 on the V6 output tube started to smoke and now looks pretty burned up. I can replace it without a problem but I really need to know what's going on in this amp. Those faulty tubes won't go back in the amp but I really need to figure out what's going on with the frying and the lack of tone. I really hate to see a good amp go to waste so I would appreciate any help in getting this thing in working order, because if he sells it, I want to be the one to buy it!

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-I'd rather be a good liver than have one...

HAMPAMP TUBE AMP SERVICES

One thing you can look for, especially if its been damaged is the pots themselves might have taken a hit. It is possible to separate the housing of the pot if it was hit hard enough. You can tell by looking at the tabs on the housing to see if they are snug and wrapped around the base of the pot, if there is any "day light" between the base and the housing then the pot(s) will not work properly. Sometimes you can get lucky and push the housing back into place and bend the tabs back around and the pot will work again.
Also, if the amp has PC mounted pots, the solder joints may have been damaged and may need to be resoldered
Also, check that the base of the pots have not been cracked, sometimes you can't tell until you desolder the pot and take it out. The base has a carbon strip that runs from one outer lug to the other outer lug, the center lug is connected to the wiper. If the base is cracked, the pot is trash and will need replaced. You can measure from across the two outer lugs to see if the resistance is within %10-%20 of the value marked on the pot.
If it is not a pot, I would check the coupling and bypass caps or possibly the filter caps, they will screw with your frequency response.

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American Viking

Finally got her working. Closure in this project is in my last post here Loss of input signal, amp functions quiet, NEED HELP .

Thanks for all the help.

__________________
-I'd rather be a good liver than have one...