Carlsbro PA60 Blues and Retrovibe RVT-40

The Carlsbro amp still isn't working. Having sorted the filter caps and the HT fuse (which it turns out needed to be slow-blow) the choke resistor (basically a great big resistor that sits between the power transformer and the rest of the circuit) is duff, smoking when the power's on and reading about twice as much as it is supposed to. Sigh.

I've also rewired my Retrovibe RV-4 to roughly approximate the wiring of a Peavey T-40 bass. Thus, Retrovibe RVT-40. I got all excited when I finished it and forgot to get a picture of the wiring, but here's the outside of the bass with classy-looking new knobs and a wee switch that does phasey stuff to the bridge pickup (in theory) and the T-40 wiring diagram.

I can't test that it works until tomorrow, on accout of it being quarter to eleven at night... but once it is tested I'll report back either in celebration or lamentation.

Peavey Roadmaster - Welp...

So, that possible solution wasn't any sort of solution.

Which leads me to the bit I'd been putting off, getting out the multimeter and painstakingly testing all the resistors.

A long time and a lot of mumbling, headscratching, and messaging Mr. Foxen on Facebook I have identified two resistors that I get no reading from, and one that is about twice the value that shows on the schematic.

This puts the potential cost of fixing the problem into the dizzying heights of about £1.50.

I really hope this is the fix I need, otherwise it's time to get experts involved.

Peavey Roadmaster - The Saga Continues

Had the lid off the Roadmaster again yesterday. Cleaned the hell out of everything I thought needed cleaning. Refreshed all the solder joints. Lugged it back upstairs, plugged it in and... still fizzy, crappy overdrive on the lead channel.

Bah.

BUT!

It appears there might be a solution.

Turns out the effects loop might be causing a problem, as even though I never use it, it's still gonna get dirty and corroded and because of the way these things are wired that might cause signal loss. So as soon as the house is awake and caffeinated I will begin diagnosis and, hopefully, I might be able to fix this problem without taking the damn thing apart again.

Effects Loops: a Problem Waiting to Happen on Diabolical Devices

Harley Benton GA5 head - Diagnosis

Took the GA5 to see Oli today, as he knows a bunch more about amps than I do and I was sorting and IDing a load of old (and I mean old) Warhammer stuff for him.

Turns out the problem is the power amp valve (EL84)... which it had occured to me it might be but without any other valves to test it with I couldn't be sure. Just glad it wasn't the power transformer really, as apparently those can be expensive.

So next thing is to get a new valve, I might replace the 12AX7 at the same time just so then it's full of all new valves. Oli tested it with Mullards, but I suspect those'll be a bit out of my price range.

Harley Benton GA5 head - Power up and begin troubleshooting

So, with the chassis back in the box (probably unneccessary, but I did it anyway) I took the amp upstairs, plugged it into my 4x12, switched it on and... nothing. Not a jot. Not even a hiss or hum.

I know it's not a problem with the speaker cable or cab, as I tested them using my Peavey Road Master head just now and they work fine. So what other possible issues could there be?

I don't think it's the EL84 (power amp valve) as that was glowing quite happily when I looked in the back of the head. No idea if the 12AX7 was glowing as it's in a metal tube thing so obviously I can't see it. Next power-on test will be chassis out, valves uncovered so I can see them both. In the mean time I'm going to have a closer look at all the connections within the amp and double double check that nothing's loose or broken. Also going to bodge some means of keeping that in-line fuse thingy closed in case that's a problem.