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Old 12th June 2005, 06:23 AM   #1
draget is offline draget  Australia
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Default fisher x100a

I have a fisher x100a amp which i got from an old repair shop, i would like to restore it (i am not going to be buying audiophool crap), apparently there is a problem with the plate transformer, i cant seem to find a schematic, and im a newbie to this sort of stuff.

pix etc.

That sorta outlines my problem.


Any ideas would be great!

Thanks,

draget
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Old 12th June 2005, 12:07 PM   #2
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Default Re: fisher x100a

Quote:
Originally posted by draget
I have a fisher x100a amp which i got from an old repair shop, i would like to restore it (i am not going to be buying audiophool ****), apparently there is a problem with the plate transformer, i cant seem to find a schematic, and im a newbie to this sort of stuff.
Do you mean power transformer?.
I have a schenatic, but it's too big to post. PM me with your email addy and I'll send it out tomorrow.

If your power trans is bung, then you'll need to get it rewound, replace it with something similar (and in this case you can get rid of the poxy doubler circuit) or remove the output transformers and ship them to me.

PS: I can't get your link to load.
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Old 12th June 2005, 12:17 PM   #3
draget is offline draget  Australia
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thanks for your reply!

thats weird,

http://draget.net/fisheramp

e-mail addy is:

da@draget.net

i think i'll have a go at rewinding the transformer myself, there is a tutorial by gregg (from geekzone) about doing it.


LOL, "remove the output transformers and ship them to me" you are the third to ask, no, i want them :P
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Old 12th June 2005, 12:20 PM   #4
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Default Re: Re: fisher x100a

Quote:
Originally posted by Brett
PS: I can't get your link to load.
It was broken before, but seems to be working now. Odd.
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Jason
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Old 12th June 2005, 12:50 PM   #5
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Quote:
Originally posted by draget
LOL, "remove the output transformers and ship them to me" you are the third to ask, no, i want them :P
They work well in guitar amps, and I have aproject brewing....

Emails sent.
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Old 12th June 2005, 03:18 PM   #6
anatech is offline anatech  Canada
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Hi draget,
Have a look at the filter caps and rectifiers before installing your rebuilt power xformer. If you have a selenium rectifier, it should be replaced by silicon diode(s) and a resistor to give the correct voltages again. Grid coupling caps on the outputs could cause excessive current too.
-Chris
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Old 12th June 2005, 04:54 PM   #7
draget is offline draget  Australia
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hum, the schems show different output valves to what i have got, and several other differences.

im thinking i might just pull everything out of it and start from scratch using something like this http://www.bonavolta.ch/hobby/en/audio/el84_5.htm

thinking of using 6gh8a as input/phase splitter (else i also have 5x 12ax7 and 1x 6cg7) and either 7189 or 6v6 for power stage.


any comments or ideas would be great!

thanks,

draget
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Old 12th June 2005, 05:51 PM   #8
anatech is offline anatech  Canada
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Hi draget,
Well, if it's in good shape and you want a Fisher, rebuild it as it is. If not or the unit is in bad shape, reuse some parts and build on a new chassis.

The units I have rebuilt to original spec have not disappointed me.

-Chris
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Old 12th June 2005, 07:13 PM   #9
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I can see one of the previous owners did replace the power transformer. Replace all caps, by now they are all dried up and wont do their jobs as they should, also change the resistors, they are very old and could have drifted in value enough to cause the amp to malfuction such as blowing fuses, making the output tubes run glowing red or even fry the transformers.
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Old 13th June 2005, 01:22 PM   #10
draget is offline draget  Australia
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going to have power transfo rewound, and start from scratch to keep things simple.

should I use:

6gh8a or 12ax7 for drivers
and
6v6 or 7189 for power valves (PP)



thanks,

draget
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