Randall RG1003 Problems

[The Dude]

Got one of these things in the shop.
RG1003.pdf
RG1003 pwr.pdf

R28 on the power amp board is not there and does not appear to have been.

There is a blue wire going from the anode of ZD3 on the power amp board (soldered to the diode lead- not a through hole) going to R143 on the preamp board. The schematic shows -15 on one side of R143 and the other side has some Chinese bullshit. It looks like an "add-on". not sure if it's factory or not.

There is a black wire soldered into one of the R28 through holes that is stripped on one end and hanging in space. Not sure what it's purpose is, or if it's factory, or the start of somebody's mod, or where the other end is supposed to go.

After several emails to Mr. Donald Carnell at American Music and Sound (supposedly a Randall tech), I've gleaned nothing. The "best" information he could offer was, "It looks like it has been modified. I don't think that came from the factory that way." For whatever reason, he will not include any useful information in his replies. Is the resistor supposed to be there? Are the wires supposed to be there? Is the blue wire correct? Where does the other end of the black wire go if it is a factory mod, etc., etc.? Frankly, I could give a shi+ if it's been modified by someone or not. I just want to know how it's supposed to be wired.

Everything appears factory judging by the solder or lack of solder in some cases. Yet, nothing makes sense.

Just wondering if anybody here has been inside one of these things and whether anyone has noticed any factory modifications.
It's been a hell of a day and Don's 3rd "reply" just sent me even further into pissed off.

[Enzo]

I don't know Don, but let us be fair to him. I suspect he is a technician, just like us. A quick google and it appears he works for a distributor. So he is an authorized repair guy for the brand? I am an authorized guy for a bunch of brands, and believe me I have no secret insights. If I have not been in one before, I have no insights into what it ought to look like. Now Don gets some phone calls or emails trying to describe something unusual. All he can do is offer his best thoughts. Every now and then I get a phone call from someone, and they start off asking about why Fender changed some resistor to something etc etc. How would I know? If a specific model has not walked across my bench, then I haven't seen the innards. They don;t send out weekly secret film reports with all the latest innards shots.

Factory? Maybe. Then again, how many times have we seen on this board someone finds a factory kludge on a board then starts to undo the mod. perhaps the mod stopped some noise, we'll never know. Maybe this is a factory mod that someone started to "make stock." Maybe this was someone trying to "cure" a turn on/off thump.

Look at the circuit, ZD3 is part of the turn on timer. The input stage of the power amp doesn;t come on until ZD3 comes up. The "stock" circuit draws ZD3 off the V- rail. So now R28 is missing, and a wire trails off from ZD3 over to a resistor connected to -15. So ZD3 now connects to -15 instead of V-

Google translate says the "chinese bullshit" means "after the class." I can also make it translate "after grade". ANother translation gave me "level" as part of it. Means nothing to me. But I might interpret that to mean once the voltage comes up.

This basic circuit is an enable, and I see it in SWR and other power amps. So it appears to me that the schematic R28 circuit probably works, though it ignores the preamp. I suspect the remove R28 and use R143 instead circuit probably also would work, and would not wake up the power amp until the preamp saw -15v. SO maybe it was factory, the original power amp design worked well enough, but the preamp also made noises... or something.

[The Dude]

Ok, after being a bit "short" with Don, I got some answers.

1) The removal of R28 is a factory mod.
2) The blue wire is supposed to be there.
3) The black wire is apparently not supposed to be there. At least he has not seen it before.

I get that he is a tech just like us and I did apologize to him for being slightly rude. That said, why could he not have given me these answers 3 or 4 emails ago when I first asked? By the way, I did also send him a picture early on which I did not post here because I had already deleted it.

[Enzo]

Who knows? Maybe there was some other pressure at his work those days.

I know I can find it annoying to receive an email from someone out of the blue, then two hours later another email wondering why I have not responded. Sometimes I find a schematic request in my in box from three weeks ago. I go ahead and send it, but the inattention was not directed at the individual.

[The Dude]

I whined and complained when I got "less than satisfactory" service.

Now, I will praise when the situation being resolved.

Don has not only helped me to figure out the mess inside the amp, but also volunteered some tips to repair it. He tipped me off to some intermittently leaky transistors that would have been difficult to find.

You never know who reads these boards and I believe in giving credit where credit is due, so in the end Mr. Donald Carnell did me a solid. I, of course, thanked him personally, but want to do so here for the record......, so,......Thank You Don!