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Discussion Starter · #1 ·
I just finished puting together a "Ratrod Deluxe":Dfrom a bunch of parts I got off $ebay-I am a novice technician and do it to learn and have fun. I have very little gear just a iron and a multimeter. I am playing the amp and it sounds like it should for the most part.

There seems to be a problem with the more-drive mode causing occilations when it is engaged, it does this also in drive mode. When the drive pot is backed off, but its okay when on full. The clean mode is unaffected.

The strange thing(or perhaps not) is that if I reduce the gain using alternate tubes like 12au7's then the thing becomes 75% controllable, I can adjust the preamp pots to make it go away or just turn the drive pot full.
I really dont need a voltage controlled occilator :eek:for a back up although I find the sound interesting.
This is affected by all 3 Bass,Mid, and Treb which are acting as frequency controllers.
The sound will go into the pwramp and get louder if I turn it up. When using the lower gain tubes it all but disappears from the drive mode and only stays in about the first 50% of the moredrive mode.

I suspect the drive circuit is causing something in the bias of the preamp tubes but since the darned drive circuit is so oddly complex I really dont know where to start. Ive searched the net and found to check my coupling caps but they appear to be okay.

I was wondering if anyone has had a similar problem or has come across this phenome before.
Any assistance would be greatly appreciated.
Thanks in advance.
 

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Discussion Starter · #3 ·
Thanks- The Amp is an actual FENDER, tubes on the PCB type HR Deluxe.
I will try your suggestions, first thing is to flip the spkr, and if it doesnt work Ill clip feedback return wire and see what happens.
Ill try switching the OPT leads.
I did modify the input tube to a point to point chassis mounted socket and with the giant soldering gun I have there could be some trouble there too, Those PCB things require a bit of practise, Ill try all of your suggestions
-much obliged-Ill let you know what happens-:smilie_flagge17:
 

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Discussion Starter · #5 ·
..well I swapped the OPT leads where they hit the board and it was just about the same.
The feedback wire just had the usual effect so It appears that all is in order in that dept.
Proding with a chopstick did turn up a loose connection ot one point which I repaired...but it wasnt it-I did manage to creat lots of new types occilation however, never thought there could be so many ways to :eek:occilate an amp-

I think the problem is in the overdrive circuit itself...opamp/ cap/resistor...or some other contraption not grounded.

...well thanks for the help - Im putting it back together.
I think Ill just leave it the way it is for now and play the thing, works pretty well.
cheers:food-smiley-004:
 
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