If R101 burns then a sure sign you have Hi Freq instability somewhere. You noted that the hum increases when you turn up the reverb. Well I'd suggest you start by disconnecting the Reverb circuit, done by lifting one end of R75-22k. (U4A mixes the Reverb back with the Dry signal, I'm not sure of the...

Better minds here will know more but if CR25 went open circuit due to cold solder joint then the output would probably be frying and likely the reason R101 got fried. A word of advice; Don't replace parts willyNilly until you establish what is wrong. CR25 is part of the bias string with C23,C24 for ...

The reverb does not go through the headphone jack, it is connected directly to the output transformer. The headphone jack does not go through the reverb in any way at all. The output ALSO connects to one of the SPST switches on the headphone jack, then gets diverted to the speaker or to R50 which i...

By the looks of it Rev drive from + speaker through R48 to Rev pan input. Rev output returns to Q1 Fet then through R41 & R42 pots. Rev signal sent to Grid on V2B then it's output is sent through C15 & R29 which is then mixed with Dry Signal on the grid of the power Valve. giving the mix of ...

It's a passive top cut filter across the signal path, look at the top cut tone in a Vox AC 30 same trick just done on the output side.
Phil.

Some tecks will likely frown on me for this but I have used WD40 or RP7 many times to un-scratch pots with no issues. My 40 Yr old Tandy Receiver had a dying volume pot with bad intermittent static on rotation,, and was going to be a nightmare open heart surgery to replace it. so 1 squirt of WD40 an...

issues that I've missed. You've missed the fact that the biasing resistor has nothing to do with setting the gain of a noninverting op amp, and that impedance in parallel with the input doesn't add to Johnson noise, so your entire premise is false. [smilie=a_whyme.gif] Seems there is a understandin...

NOISE is your Enemy when designing high gain dirt circuits, Not just ROG but many others suffer the same fate. It's not the fault of the active components in these circuits It's the combination of having many hi Z sections all joined up. Go look at the first stage of a TS9 or similar schematic. They...

FiveeveN has linked to the answer, wise to read it.... But I assume your having trouble working out how to run this on a single supply? I'm adding a quick edit of Rods circuit which should help. Everything in between the input Caps and output cap runs at Virtual Common or Half supply. Caps are likel...

Does turning the speed knob effect the speed of the ticking?
Phil.

Thanks Mr 57, Brilliant explanation, Wish I knew this years ago.
Phil.

Maybe check that Transformer, I can't see enough but it looks like the Tx has 6 leads and the back of the PCB shows all 6 soldered.
The center lead on the primary should be left open, (as per schematic) if it's grounded them you would loose a lot of volume.
Phil.

Have you tried this yet?

Common (neg of your 9V pedal PSU) goes to the MAINS EARTH terminal.
Do not rely on alloy case for ground return.
Phil

Oh dear :shock: Well if there is that much damage then for sure you have carbon particles all around that area which could well be creating a pathway for the hi voltage to trace through. Sounds like you will be forced to rebuild the Board if you want it to be reliable. :( This is why you see flame p...

Remember electrons flow to the Highest voltage potential. :hmmm: Any power Valve would burn through the screen rapidly if the Plate voltage ever falls lower than Screen voltage. As the amp is old the plate pin might be arcing across the socket somewhere which will pull plate voltage down. And I woul...

Oh dear, As the Amp has already had Screen grid issues then the sockets may have hair line carbon traces (which you can't see) and once that happens it's likely the new tubes will arc again along the same path, in which case it's a Socket replacement. Also worth note is that EL34's are notorious for...

If you are going to run mains to a metal case (your module one I presume) Then For safety reasons alone you definitely need to tie the mains earth to that metal case otherwise it could be deadly if something goes wrong. :twisted: As *mauman* already noted, post a layout or picture of the setup as th...

Hi Kiltro, An LM7809 would have no trouble dropping 9volts, They are rated up to 1Amp. FWIW, I use a Laptop power supply which delivers 19VDC at 4Amp and then use an LM7809 for the lower voltage pedals. IIRC I just added a series 220R resistor before the Reg chip and a small heat sink to be on the s...

Thanks phatt, excellent info. I think the pulldown resistor in the input is just to stop the switch from clicking from capacitive buildup of voltage since the LED is also going through it, or maybe backwards charge potential on the input cap, I remember popping being some issue with it. Yes R1 is j...

Glad to hear it helps you Manfred, The sensitivity of the input is the issue. Remove R1 as it's likely irrelevant,, R2 is the dominant load. Try looking at it this way. As *mictester* noted the input Z is way too low to be useful for guitar. OK you change R2 to 1Meg and you raise the input sensitivi...