Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Solid State => Topic started by: bruno on October 23, 2012, 06:58:01 pm

Title: Relay switching loud pop (dumble type hrm amp)
Post by: bruno on October 23, 2012, 06:58:01 pm

I have here an amp, that has 4 gain stages (relay switchable) with a dumble HRM topology. When I add the two extra gain stage and their tonestack I get a loud pop, if I remove V1 (the two clean gain stages) the pop is still there at the same level, if I also remove V2 (third and fourth gain stages) the pop is also still there at the same volume.

If I remove the PI, no pop passes into the power stage. I've tried several things, such as measuring DC after coupling caps, addind 4,7M resistor to the grids of the gain stages. The relay is still popping even with no tubes at V1 and V2, only the phase inverter, which makes no sense, since the gain stages after the relay, should be amplifying the pop.

Any tips?

Thanks

Title: Re: Relay switching loud pop (dumble type hrm amp)
Post by: tubenit on October 23, 2012, 08:10:48 pm

I would guess you either have a bad solder joint somewhere from the LTPI to power tubes ................ OR look at the filter caps to the LTPI, power tube plates and screens and make sure the solder joints there are good.

I'm guessing that you have an intermittent connection in there somewhere?

with respect, Tubenit

Title: Re: Relay switching loud pop (dumble type hrm amp)
Post by: phsyconoodler on October 23, 2012, 11:36:45 pm

A look at your layout and wiring would help us to nail it down.