The Amp Garage

What kind of wire are you using there, please?

Raoul Duke wrote: ↑Wed Jan 10, 2024 10:06 pm …or the meter just runs away(?!). That seems odd.

I’d wager that’s just the effect of using the multimeter for measuring resistance, when there is a capacitor involved.

Looks fabulous. Congratulations.
Going for suede on the cabs?

I looked and couldn’t spot anything from any of the places I’ve used. Do you know the original capacitor brand?

One hack might be to drill and mount a 4 tab plate on some short (5mm?) standoffs.

Thanks Dorrisant. It was your AO conversion that inspired me. The Tube Town 18W extended PT has dual heater taps so I split the pre/power amp runs, elevating the preamp heater. I powered the 12V relay using the 8V winding with the voltage doubler arrangement, like the Dumble 124. The faceplate is th...

Thanks Martin

I had tried splitting out the rectifier lead and then moved all those around with a chopstick, but never tried moving the CT. I think you’re right that it was somehow getting onto b+ for V2 on that run, or under the diodes. I also wondered if changing the diodes may have been a factor.

Not quite finished tidying up, but the rectifier ended up mounted on the side like this. If it helps anyone stumbling on this thread - there seems to be no issue with these B+ leads bundled but note the wire running from the diodes is no longer in the bundle. Thanks all - I'm going to finish tidying...

SOLVED! - relocate main rectifier diodes to the far right position- for the test to not destroy the board, can be built in the air, p2p with several new diodes, and mount directly to the capacitor for main Ub+ node Thanks a million Bepone - your intuition was correct and I would not have got there w...

dont measure directly Ub+ line with 1:1 then.. so grounding before input capacitor to the PI, gives humm.. to be sure that we are in line, this point - IMG_5344 (1).jpeg humm must dissapear. if doesnt, it is created in PI Yes, Grounding at that point and there remains a little hum (more than you’d ...

Thanks for confirming. So I have v1 and v2 pulled, and somewhere between the output of v2, and input of v3 (PI) I get this 100Hz - so basically the tonestack. If I ground before the coupling cap to the PI hum remains, but if I ground after the coupling cap (i.e. pin 3) it's silent. I've wondered if ...

Thank you @bepone then checking the layout.. rectifier diodes are not in the good position, they are too close to output tubes, they can spread noise around them to all the sensitive wires remove all the rectifier diodes (biggest source of hum) to the far right position, close to the first electroly...

Thank you both From those comments: - Scoping the elevated heater shows no ripple, but I've now referenced it to ground instead - no effect on hum. - I've taken the master out of the circuit - no effect on hum other than volume - separating out the b+ #1 and chopsticked around moving the b+ wires an...

Hi folks I've recently finished wiring up a 6v6 Silver Jubilee and am having trouble diagnosing the source of a 100Hz hum - I'm tired and feel I am overlooking something obvious. Any suggestions for where to look next, please? With V1 and V2 pulled, the hum is present with the master at 0 and increa...

Looks good - and I hope you have a good break too.

I'm curious if it would be helpful to move the heater balance resistor to ground (right most resistor on that last photo), rather than to pin 8?

Colossal wrote: ↑Fri Dec 22, 2023 12:17 pm I would probably go with the 8k taps.

Thank you for deciding for me - I've been stuck in the procrastinatrix