Before and After

[70sSoundQuality]

Hey all, still pretty unused to the idea of tubes, but still lurking around this forum and reading constantly. I have amassed a small collection of tube amp chassis's, preferebly from the 40s to the 70s. I never, EVER realized how cheap tube amps could be. I have a Super Reverb which was cost an arm and a leg, and little did I know I could buy a tube amp for $50 that actually sounds BETTER than any fender I've heard in person. This post focuses on a no-name tube amp, I guess the brand would be wurlitzer? I dont know the brand, and I dont even know the wattage.

I just want these tube chassis's to use as a sort of pre amp. I plug my bass into the RCA input of the amp, then line out of the tube amp into the mixer. The sound is phenomenal for recording and getting vinage bass tone. Especially on bass guitar. I remember Matt saying the amp I used has a tube that helps bass a lot, a tube called the 7027A. I don't really know what the difference is, but it wins my heart over the fender for any instrument really.

The speaker on the organ had a terrible voice coil, so all this time I thought that the amp sounded like crap, but once I went direct out of it I was amazed!

There is a trim pot called "hum balance". For some reason or another, and perhaps because the amp is dated 1959, the pot is stuck. The screw that fastens it on is stuck. I would KILL to be able to dial in that pot because there is slight hum depending on where I am standing. Does anyone know of a good evaporating cleaner/lubricant solution that will losen this pot? I was thinking about using DW-40 but I changed my mind


I spent a long while cleaning the amp and trying my hardest to get rust off of the chassis. The amp is finally clean and seems to sound better as a result of it

I really wonder who I can take this amp to for work? Two of the pre amp tubes dont light as brightly as the rest, and I guess I dont really know how stable this amp is. The tubes heat up rather quickly. Anyway, I just felt like posting, not necesarrily to harass anyone with newbie questions. Also wanted to post the photographs of the amp before I cleaned it up.


Best,
John

[70sSoundQuality]

closer photograph

[mojo]

Nice cleaning job. Working on tube amps is not rocket science but does require a little knowledge and caution. If you're interested in learning yourself I'm sure some folks here can steer you to resources (books, etc.). If you just want someone to help fix this amp I'd look around your area for an older TV or radio repair guy or check with the guys at your local music store. Good luck!

[charliewired]

Nice little score your working on there - I have an old Hammond M2 Im in the process of converting into a TV front Bassman right now - but its slow going as its my first conversion build, there are all kinds of cleaner type lubricants at your local electronics store - but stay away from the ones with silicone in em - thats what Dan Erlewine says in his vids about guitar electronics anyhow - when I bought mine I got silicone free and it seem to work fine. you made a good call on the WD> Never Never use WD40!!!! appearantly thats a big no no from what Ive heard from ppl who know what thier doing. Kevin OConner writes some excellent volumes about tube amps, after you grasp them you would be sailing through any build, repair, mod, or conversion. www.londonpower.com
Gerald Weber has some great amp books - that focus mainly on repair and modification - Tom Mitchells books for beginners - Tino Vottola's books - "The How and Why of Tube Amps as Gar see it" by Gar Gilles is a great old school look at tube amps - The Tube Amp Book by Apen Pittman is a great overview. All these are for if you wanna learn yourself. If you do these are great books - Im getting the Gar Gilles book in the post tommorow and Im pretty excited about it -
Usually there are techs in any area - I would take it to one of them if I could before any radio or TV repair guy - Phone your local hip music store and ask who does thier repair work - usually the cool music stores will know the "cool guys" who tech around town - you never know the guy might teach you while he does the repair, I found a nice local guy who techs and now he is talking about apprenticing me now.
Cheers and good luck with it - sounds like its off to a good start already. But you'll need to loosen that balance pot before you'll get rid of that hum, its part of a 2 resistor voltage divider {one resistor and the pot as a variable resistor} that acts as a center tap - that what they used to do in the old days. You could replace that system with a pair of 5% tolerance resitors in a setup that wont drift with vibration, so ask the guy who fixes it about that and whether he thinks its a good idea.
Cheers