The Amp Garage

Hi All, Trying to help out a friend in the UK get a panel made for an amp. Nothing fancy, probably just black and white like a Hiwatt. Here in the states I use a service where I send them an Illustrator file and they etch and mail it to me. Anyone have a recommendation of something like that in the ...

The 10K pot that Fender used is capable of providing proper bias range for Deluxe Reverb up to Twin Reverb simply by slightly changing the ACV input and the tail resistor on the pot. And the Fender pot can be adjusted internally or externally. Sounds like you already have the ultimate pot. The Dyna...

You do not want to use a pot in the first place you want to take advantage of using a 20 turn Ciramic trimmer in the resistance value that you need. There far more accurate and they do not drift. Right I know about this option bu what i'm really looking for is something that is panel mount so it co...

What are people here using for bias pots? I've been using the CTS screwdriver-adjustable ones but they only come in 10K and I find that range a bit limiting. Does anyone have a favorite bias pot option they're using? I like to have things externally adjustable so panel-mount is key. The range is us...

What are people here using for bias pots? I've been using the CTS screwdriver-adjustable ones but they only come in 10K and I find that range a bit limiting. Does anyone have a favorite bias pot option they're using? I like to have things externally adjustable so panel-mount is key.

ViperDoc wrote: ↑Tue Oct 10, 2023 5:12 pmYes.

Thanks!

When working with a transformer like the one listed below, do you have to parallel the two 120V pairs for 120V operation? I think the answer is yes, but just making sure. https://www.hammfg.com/files/parts/pdf/290EEX.pdf So it would be... 120V - black/brown together (neut) - white/orange together (h...

Get a little heat sink compound under that MOSFET and it will be even happier. That's what i'm doing right now. I can leave the amp for an hour or so and the temperature of the MOSFET is plateauing at ~125°F (~52°C), which I think should be satisfactory (its not in an area in danger of being touche...

bepone wrote: ↑Fri Jun 09, 2023 5:02 pm nice..but whats about 95.8% bias??

not sure the question. For a cathode biased amp I usually shoot for 95% dissipation. Do you or others disagree?

Also for anyone curious here's my implementation:

Update on this following a part order... First, I did put a 1ohm resistor between the center tap and the start of the Zener string and measure 160mV across it, so to answer the question we're drawing 160mA of current. So initial attack was to try redoing the Zener string with new diodes. I know ther...

The diode string is between the PT center tap and ground, so that should be AC, no? No, that's dc. Current may be pulsing but it's only flowing in one direction, ie, direct current. Well in that case i'm measuring 160mA, which explains things even LESS. That's measuring between the CT and the top o...

Cutting to the chase on this... There is still something really wrong with the basic zener string you have. The basic zener string should be working. Thanks, that's what it seems to me as well. The method seems popular and trusted and i'm just not sure why its not working in this case. ESPECIALLY wi...

Alright, it appears that i'm limited in the performance on the two multimeters I have. Only one measures AC current, and in ranges of up to 200mA and up to 10A. So i'm losing significant digits on the 10A setting but it's coming up with .24A (240mA). This is more than I was calculating (~220mA) but ...

Are the ones at room temp shorted? I had thought of that, but figured a shorted diode wouldnt drop any voltage. And since i was seeing ~48V drop from four 12V diodes that would indicate all are working. I tested them just now, though, and all read at .638V forward bias voltage drop. All the others ...