The Amp Garage

OK, not so good. I turned on and off and when I turned on again, I head a hum and saw the PT HT fuse go. I was monitoring C- and had -356V, so not there the issue Standby Switch is gone again. Back with 2 power tubes and seems fine. Will test further. Probably a bad power tube (one of the two I rem...

OK, not so good. I turned on and off and when I turned on again, I head a hum and saw the PT HT fuse go. I was monitoring C- and had -356V, so not there the issue Standby Switch is gone again. Back with 2 power tubes and seems fine. Will test further. Probably a bad power tube (one of the two I rem...

I think there are 2 possibilities: either the bias resistance is off or the bias cap is leaking. My guess is the latter. Thanks for the input Erwin. I should have replacements caps by Friday latest, I will replace it and update accordingly. What could have been the root cause of my fuse, standby an...

It just occured to me that you probably installed the (to me somewhat questionable) biaspot / variable series resistor that is not original in the schematic and which could explain the slow rising negative bias voltage and low bias supply voltage on the 10uF cap. Slow rising negative bias supply vol...

Your voltages are very strange. The voltage on the 10uF should not come down slow but should read around -380 instantly. And since there is allways the load of the 220k cathode resistors in series with the 470k resistors on the bias supply voltage it should not be able to come down as high as - 510 ...

It was not clear to me the amp still didn't work at all. I don't understand your voltages. You say you measure -48V on the 10uF bias supply cap, but there should be something around -380 V or so to feed the CF cathoderesistors. If you mean -48 on the powertube grids, this should be fine. If the B+ s...

Most likely there is a component or connector with a alternative path for high voltage to cross (flashover) Either due to compromised isolation, dirt or defect. When you have a flashover for instance on a tubesocket due to a spike in voltage, the spark can create a carbon trace which in turn makes i...

If you allready use a cap over the switch and diode over the relaycoil, extra caps won't help. When the relay switches, there is a very short time where the grid of the first triode is only grounded by the 1M resistor and is not connected to the low resistance of either the trimmer of the Fet board ...

They are not discontinued, they just changed the base from black to red because of a change in the manufacturing factory. https://www.tubeampdoctor.com/en/6l6wgc-str-redbase-small-bottle-tad-premium-matched?number=RT811 The ' red base' 6L6WGC-STR tubes are most likely Tung sol 6L6GC tubes that are ...

If i had to use a terminal, i think i would use something else. But i would most likely find a way around using a terminal strip. I am very cautious when wiring mains voltages. Here is an example of how i wired one of my amps. Since dpst mains switch is mandatory in my country, it is easy to wire bo...

Does the thickness of the aluminum sheet matters? Would the aluminum tape and 0.5mm aluminum sheet behave the same in terms of protection ? Kitchen foil will work, but it needs to be electrically connected to the chassis. That's probably why your experiment didn't produce results. Yes, tape or foil...

Hey Richard1001, thanks for your feedback. I bought an aluminum sheet that I cut with a small sawblade, it was a nightmare to do, took forever, result was not super clean... I tried to put it on top of the a running amp and hear if there was any difference, but could not tell. is it only to isolate...

Quick question on cabinet building: do you insulate the top of the cab with some aluminum tape? Thin Aluminum plate? I did use some tape on this build although I am not sure it makes a big difference. What's your take ont his? PXL_20220101_170455761.jpg Fred. For this i use a 0.5 mm aluminium plate...

Happy New Year everyone. I recently converted one of my SSS amps from 240V to 120V and as surprising as it may sound, the amps actually sounds better at lower voltage. The plates dropped from 456V to 445V (about 10V), bias is set the same at around 35mA. Amps feels quieter in general and sweeter so...

Well you wrote you get 5V AC out of one side of the PI while the other side shows no signal at all. This is odd and suggests either a wiring or component problem. You should be able to measure this. Just for the PI What are the DC voltages on both the board eyelets and the tube pins? And if you trac...