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Post subject: 1970 Fender Twin Reverb Near Mint but Not Working
Posted: Sun Jul 29, 2012 1:01 pm
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I just bought this at an auction today. Prior to bidding, we were told it wasn't working but the cosmetic condition, matching serial numbers, original cover - just couldn't pass it up.

I plugged it in. While in standby mode, it was fine. Taken out of stand by, no volume except for the staticy sound of the knobs while I turned them. Then I smelled something burning.

There's a cap on the underside of the head chasis. I think a filter cap and accompanying resistor blew out.

I want this fixed. So, the questions are:

1. was it these two parts which need replaced?
2. was there something else going on leading to this?
3. how much should I anticipate spending to repair it?

For reference, just to see the time capsule that this is, here is a photo:

http://www.facebook.com/photo.php?fbid= ... t=1&ref=nf


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Post subject: Re: 1970 Fender Twin Reverb Near Mint but Not Working
Posted: Sun Jul 29, 2012 1:02 pm
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and the story that came with it was that the original owner bought it, plugged it in, it didn't work and he was going to take it in at some point to have it worked on.

42 years later, I own it. I love how this stuff happens.


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Post subject: Re: 1970 Fender Twin Reverb Near Mint but Not Working
Posted: Sun Jul 29, 2012 1:48 pm
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1.) Is the fuse ok?

2.) Sounds like one of the two 70mfd/350VDC electrolytic filter caps, in the first pi-section of the main power supply circuit may have blown. This can happen when an amp is fired up, after being stored away for a long time. The sudden AC power is too much for the discharged & un-formed 'lytic caps.

Why it's a good idea to ramp up any amp that's been in storage for awhile. Either with a Variac or the "Old Inline Light Bulb trick" (TV man's favorite tool). Also, this tests for shorts before catastrophe. I know, too late now. But, keep it in mind for the future.

3.) A good tech prolly should inspect the amp. Replace what is out-of-spec or dried up caps.

HTH. Good luck!

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: 1970 Fender Twin Reverb Near Mint but Not Working
Posted: Sun Jul 29, 2012 2:21 pm
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gideon wrote:
and the story that came with it was that the original owner bought it, plugged it in, it didn't work and he was going to take it in at some point to have it worked on.


Let's see if I have this straight: The original owner paid $535.50 (full MSRP price in 1970 -- a lot of money back then), the amp crashed and burned immediately, then he warehoused it for over four decades waiting for the "right moment" to have it repaired?

:shock:

I remain unconvinced.

:roll:

That said, get the amp to a competent technician familiar with vintage Fender amp architecture and ask him to perform a complete bench check. Plan on two or three hundred dollars to repair/recondition all issues and tune it back to full factory specs. With a new set of quality glass, you should expect ten to twelve years of trouble-free service assuming you do not abuse the amp.

HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 1970 Fender Twin Reverb Near Mint but Not Working
Posted: Sun Jul 29, 2012 2:27 pm
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thanks guys.

arjay, i have reason to believe it in this particular case. need to see it all to believe it. this doesn't have a scratch on it from use or otherwise. the grill cloth too is tight as a drum. i was a bit skeptical but the chasis code dates it to 1970.


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Post subject: Re: 1970 Fender Twin Reverb Near Mint but Not Working
Posted: Sun Jul 29, 2012 2:32 pm
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gideon wrote:
this doesn't have a scratch on it from use or otherwise. the grill cloth too is tight as a drum.


That's neither here nor there -- I have amps older than that that are just as clean and in some cases, cleaner.

The background story may be true but my advice for servicing and maintenance stands.

Best of luck.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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