HI all.
I have had my old Hartke 3500 which was purchased around 1991. Its been gigged hard and has NEVER Failed me up until now. Literally only needed new valve for the preamp occasionally.
Occasionally the level drops And has a fuzz/hiss noise then Jumps back up to full glory again. I've isolated this to the power stage by passing the pre-amp via effects loop.
Anyone know of any known issues as these amps age which can cause this? or any pointers to troubleshooting this? I was going to start with replacing the caps.
Second question. This amp rocks. Seriously awesome amp that after nearly 25 years use still gets comments on how good my sound is. If the worst would happen are the newer HA 3500 the same tone?
Cheers all.
Keep in mind that when you plug into the effects return, you are NOT completely bypassing the preamp. There are still several preamp stages to go before hitting the power amp: effects return buffer > lo & hi contour controls > graphic eq (if engaged) > master volume. It sounds to me like you have a loose/broken solder joint that is making intermittent contact. This happened in the preamp of my 3500 and I found where it was and was able to re-solder it. That said, yes, the problem
could also be in the power amp. A friend bought a used 3500 (we have the older MOSFET version) where the same thing happened on one of the power mosfets on the power amp module (the black "brick"). I re-soldered it and it's been great ever since, about 10 years after buying it used. Don't give up on this older model - it's highly repairable and despite the symptoms you're experienceing, it sounds like it's a simple, easy to fix problem. But even if the power amp module is bad, you might be able to get a replacement module, as I have done that for another friend as well. Another thing to check is the small connector that connects the preamp to the power amp, as it may be dirty and need to be re-seated. It's located on the power amp module towards the front of it. In fact, it's a good idea to re-seat any of the other removable connecters in the amp to make sure they are clean and connecting well. There is even one connecting the input jack to the preamp board. But be particularly careful if you do this with the large connector on the power amp module because that connector is NOT made fool-proof against staggering it to one side or the other when you re-connect it, and if you do stagger it, you'll blow out the module completely! (It's been done!)
If you love the old mosfet version, you may not like the newer bipolar ones! The Tube channel has been re-voiced, as have the frequencies of the lo and hi contour controls. The compressor is completely different too (the old ones are virtually a dbx 163x). And the bipolar power amp will not sound identical to the mosfet version (though this is only a slight difference). The new ones may have slightly lower noise levels, but it's never been an issue for me and I prefer the tone of the older amps.
