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91
Q & A / Re: Unwired Rectifier Tube Socket Stock From Factory??
« Last post by Derrick on April 21, 2017, 03:47:40 pm »
...the amp was wired so that a tube wouldn't work.

The tube does work though.  Anyone have a picture of one with both tube sockets wired from the factory?


Mine has a sticker on the side that states passed inspection December 1970. Curious what date yours is?

I recall it being 1970 but would have to open her up to verify.
92
DIY / Re: Removing Paint from Tolex
« Last post by eddiemac on April 21, 2017, 03:05:25 pm »
Another method that works pretty well, at least it did on my Sorado with a name painted on top, is to apply black shoe dye (what they sell at Tandy Leather to change the color on shoes).  Let it sit for awhile and then rub with a rag.  I can only faintly see the writing now, and only because I remember it being there.  It also makes the vinyl look fresh-black, better than cleaning with soap and water.
93
Q & A / Re: 1970 1200s restoration
« Last post by Tdlunsfo on April 21, 2017, 05:10:08 am »
They are available but man they are expensive. $25 a piece. The ESR was pretty low on these at .64, almost half of my brand new can cap. I feel good leaving them in for now. Planning to dig into the trem today. Already suspecting this 22v zener and the 1 and 2uf caps. Not sure what's up with the bass. Could be tube related.
94
Q & A / Re: 1970 1200s restoration
« Last post by _peter on April 20, 2017, 10:58:43 pm »
Hi,

good to hear the amp is working again. Nevertheless, I would put in new electrolytic caps.
The  20 @ 600V might be hard to find. Here in Europe I got lucky on this weird page:
https://www.die-wuestens.de/eindex.htm
They have F&Ts with a 550/600V rating.

Cheers,
Peter
95
Classified / Re: WTB: Sunn Beta Lead Head
« Last post by vmattina on April 20, 2017, 09:02:56 pm »
I have a Sunn beta lead in excellent condition. I live in Salt Lake City so I'm not sure how I would get it to you.
96
Q & A / Re: 1970 1200s restoration
« Last post by Tdlunsfo on April 20, 2017, 06:27:39 pm »
Wired back in the old caps and then blew a fuse. Change fuse, fire it back up and notice a redplating 6550..uh oh! Quick check on the bias and I am somewhere in the -30v range instead of -55v. Re-biased the amp and the hum and slowly decreased. She sounds great. Tremolo is still a little weak but reverb sings. Amp lacks bass. Could be that the speaker is sitting out of the cab. Overall a very clean sounding amp. Threw a Big Muff Pi on it and she growled! This amp is a beast. If you can't cut through the mix with this thing then I don't know what you need. Lesson learned on the bias and swapping over from diode rectifier back to tubes.
97
Q & A / Re: 1970 1200s restoration
« Last post by Tdlunsfo on April 20, 2017, 12:53:53 pm »
You know what... your right. I have miss-counted the number of capacitors and didn't take into account that one of the 20uf on the cap can is being unused. I guess from working on these old tube radios, I was used to seeing these added after the fact and assumed the cap can took care of all the filtering. Thanks for helping me see the forest from the trees. This might even fix my tremolo issue as well. Will post back.
98
Q & A / Re: 1970 1200s restoration
« Last post by _peter on April 20, 2017, 10:49:33 am »
But those 20 @ 600V are the first two filter caps. You ripped them out and wonder why it's humming?

If I got you right, you have a huge ripple on the supply voltages now. That has less effect on the power amp,
as it works in push pull mode, but the ripple will modulate the preamp signal.

That's why the hum stops when you pull the PI.

I'll attach the schematic, so we know we are talking about the same thing. I guess you mean C29 and C30.

Cheers,
Peter
99
Q & A / Re: 1970 1200s restoration
« Last post by Tdlunsfo on April 20, 2017, 09:13:32 am »
Yes and I think so or at least one of them. The other appeared to be in the bias circuit. Can't find them on the schematic though. The filter cap was a 30,20,20,20 model but schematic shows a 40,30,20,20.
100
Q & A / Re: 1970 1200s restoration
« Last post by _peter on April 20, 2017, 09:05:31 am »
Hi,

you aren't talking about the 600V 20 filter caps, right?

Cheers,
Peter
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