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Post subject: Re: To repair or not repair
Posted: Fri Jan 14, 2011 2:39 pm
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elprice wrote:
The tube chart states that this is a AA763 circuit design but in fact has all the changes of the AB763 incorporated.


Not surprising......this happened often during the transition years between "AA" and "AB" revisions. The only truly trustworthy data on a tube chart is often the tube layout itself.

Arjay

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Post subject: Re: To repair or not repair
Posted: Sat Jan 22, 2011 11:39 am
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No sense asking a community forum like this a question and not listen, so I listened. I took it to a family owned radio and TV repair shop that been in business since 1944. I said no repairs, call me if you find something. They called and I went down to see what they found. It was a 100 ohm resister on the board that appeared to have never been soldered to the terminal but was sitting hard against it. We soldered it and I took it home. I did a dim bulb test to soft start the electronics, starting with a 40 W light bulb and moving up very slowly to 100 W. I let the amp soak with each bulb in this setup for about 14 hours to make sure of no problems and to reform the caps. Results: amp works great with awesome volume and power. Thank you fine folks for your advice and bringing me to the table. Next part, how to sell it and not using the popular online auction thing?

elprice


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Post subject: Re: To repair or not repair
Posted: Sat Jan 22, 2011 12:06 pm
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Well done!

You could post it on classified bulletin boards in forums such as this one. You could also post on craigslist and say that you're willing to ship. I've bought and sold things that way more and more in order to avoid eBay.

Still, eBay gives you the whole world as your market. One strategy is to allow buyers from any country, but slap a heavy shipping charge on them. A fanatic in Europe might buy it or at least bid on it and push it up higher than you'd get otherwise, which could cover your paypal and eBay fees.

You should look into what a reasonable valuation is so that you don't poison the market by starting out way too high (or low). One guy on eBay this week had to reduce his brown Super Amp from $14000 to $5000, and he'll be lucky to get $1500 for it in its current condition.


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Post subject: Re: To repair or not repair
Posted: Sat Jan 22, 2011 11:35 pm
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Just a little trivia I learn from a tech long ago:

60Hz hum is very low frequency. Like lower than open low-E string. And is usually caused by wiring of the AC-heater line. Sometimes, someone replaced the sockets on the power tubes and flip-flopped the heater lines from one tube to the other, in the daisy chain (not keeping same lines connected to pins 2 & 7 on a 6L6GC or 6V6GT). All lines should be go to same pins of power and gain stage /PI tube's heater pins, in order to have the twisted wiring effectively cancel out AC-hum.

120Hz hum is an octave higher and is usually caused by bad filter caps in main power supply. In an amp that's just starting to hum or has old caps, you can hit the G-string on 15th fret, hold sustain, and you may hear a "beat" or pulsing tone---when amp is at volume. This indicates that the main filter caps are starting to dry out and need replacing.


Last edited by BMW2002Ti on Sun Jan 23, 2011 12:31 pm, edited 3 times in total.

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Post subject: Re: To repair or not repair
Posted: Sun Jan 23, 2011 7:57 am
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60Hz hum is present in all the ac wiring of your house,go outside sometime and put your ear up to the electric meter and you will see what I mean,I work for an electric utility and that's one trick we use to see if a meter is energized without getting out the volt meter and opening the meter base...just a quick check.


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Post subject: Re: To repair or not repair
Posted: Sun Jan 23, 2011 4:32 pm
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Good tip, BMW. You too, Rick.

Arjay

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Post subject: Re: To repair or not repair
Posted: Sun May 08, 2011 6:49 pm
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Thanks everyone for your help and support. I just posted the amp and a Guild DE500 guitar on Craigslist for the New York city area. Check it out and see the pictures that are hyper-linked to a picture hosting site. Please Spread the word, even if only to look at the pictures.

elprice

Just type in "Rare Vintage Combination"


Last edited by elprice on Mon May 09, 2011 8:55 am, edited 2 times in total.

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Post subject: Re: To repair or not repair
Posted: Mon May 09, 2011 7:29 am
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Both are beautiful. Still has the original RCA tubes with few hours? The amp looks factory fresh. Personally, I would have a hard time selling that pair. But if you aren't using them, I understand.

Art


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Post subject: Re: To repair or not repair
Posted: Mon May 09, 2011 8:30 am
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I am not sure why others are recommend you keep the amp when you don't play guitar... :? :? :?

Anyway... how much for the guild ?? What part of the world/usa do you live in ?

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Post subject: Re: To repair or not repair
Posted: Mon May 09, 2011 8:51 am
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Thanks Art,

Seems most, especially dealers misuse the word "Mint", then go on to say the power cord was changed or whatever. My opinion is mint means exactly as out if the box new from fender, period. Mine does however still have the two prong power cord. Anyway I wanted all of you to at least see what you and the others helped me with. Money is not the issue so maybe I'll still have it in a year or so.

To address the next post, I am not interested in breaking up this marriage.

I am also not advertising or bartering on this site. Discussion and show and tell only

Thanks,
elprice


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Post subject: Re: To repair or not repair
Posted: Wed May 25, 2011 1:03 pm
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elprice wrote:
The amp does come on but it sounds what may be 60Hz signal coming from the speakers. This occurred even with the volume control knob at the lowest setting. Of course when this happened I turned it off within seconds. The tube chart states that this is a AA763 circuit design but in fact has all the changes of the AB763 incorporated. I also have the original envelope that contained the owners manual which is not very informative and the schematic diagram. The owners manual is written to cover most of the amps of that period and is showing pictures of a twin reverb and a showman. The schematic is for a bandmaster AB763.
Thank everyone for all your replies.
Elprice


That definitely sounds like a bad filter cap. It's an easy fix. Even an average tech should be able to handle it with no problems.

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Post subject: Re: To repair or not repair
Posted: Thu May 26, 2011 4:20 am
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personally, when looking for the tech, i would not tell the story you told here nor would i mention anything about possible selling of the amp.
it leaves you open to be taken advantage of in so many ways.
personally, in a down market, i wouldnt sell unless you really really needed the money.
better times and better prices are up ahead. (somewhere)

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