Tube Amp Archive

Thanks for the link Cliff, great stuff

I've ordered some diodes so will give them a try in the heater supply - I like the idea of a variac but don't want to carry it around everywhere! Many thanks
J

It doesn't do much to the hum, at extremes it just ads a bit extra buzzing hum - I have read that it's for AC balance. If anyone knows more I'd like to know.. I've just measured the value either side and set PR1 in the middle. I checked the voltages today and realised the heater is running at 7.09va...

I got a new PT from Tube Amp Doctor and it's now nice and quiet - TAD were very helpful and shipped it fast. Looks like a well made trans with hum band, interstatic shield and end bell. There's now only a tiny bit of normal background hum, barely audible, I've tried raising the heaters etc but it al...

The bias voltage comes off the wiper of PR2, if the pot fails or gets "scratchy" there will be no bias voltage going to the power tubes! The tubes will then draw maximum current and overheat, and worse, overheat the output transformer. I've run a 220k resistor from the junction of R22 and PR2 to the...

Yup, I've given in and ordered a new PT and end bell from Tube Amp Doctor, hope that stops the hum... I was surprised to not even see a cover on on the old PT. I agree, Marshall (and all the other big manufacturers) save every penny they can for max profit, so always use the cheapest methods they ca...

Cheers Phil & Tom, I've got some rubber washers so I'll try that this eve, as well as reversing the the wires to the primary. I'll let you know how I get on. It's a factory made amp - made by Marshall in 1990, model 9005. I've read that these amps have a reputation for running hot and the PT giving ...

Hi all, I'm looking for some advice about my Marshall 9005 50w+50w power amp. The power transformer hums loudly and seems to be mechanically coupling the hum to the OTs and my preamp. I'm used to Marshalls & transformers humming but this doesn't drop to a usable level off standby. So far I've replac...

Check out http://www.musicmanamps.com/ there's most of the schematics and lots of info in the forum.

All the best

J

Have a look at http://www.musicmanamps.com/ - lots of info in the forum and schematics. I think there's 2 versions of the 2100-65 the later one is all solid state with a tube power amp, and the earlier is a solid state preamp with tube PI (a 7025) and tube power amp. You cant mod it like the RD amps...

Ooo you lucky lucky.... An amazing player, one of my heroes, ever since the Telecasting album. I never did get the hang of those behind the nut bends though...where's me tele.... Have fun!! J

I've found a copy - it's for mac os9... If that's ok I'll email it over, the files are 8.8mb for the program and 6.7mb for the docs.

Cheers

J

Heistl,

Oo nice sounding clips! I'll put up some clips of my amp soon now I'm back from my summer hols... I'd hesitate to compare it to your all-tube-and-gorgous sounding amp, but it will be interesting to do a comparison between my cowardly mod and yours!

Cheers

Justin

Final schematics now posted with first message, cheers, J

And a couple of pics of the od pcb squeezed into the chassis.... J