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Fisher X-101-B

47.17.241.128
Posted on June 4, 2024 at 18:30:56
reuben
Audiophile

Posts: 1649
Joined: September 28, 2004



I was never sure I have an X-101-B until I came across this ad. Part of the 'B' lettering on my unit is missing. Every other X-101-B I have ever seen looks the same as the cover pic on the service manual for s/n 70001 to 79999. Note that the knobs on my unit are different (no end caps to fall off), and I have 2 gizmos in the canter of the face instead of 3.
Is there something special about my unit? Maybe an early production revision? I can dig the unit out and check the s/n at some later date. The power supply transformer was shorted and about 15? years ago I found a company that had already done the engineering and had them make me a new one. I figured many or all of the transformers had failed.
Can anyone shed some light on what was going on?
Thanks,
Tom

Dark energy? Ridiculous!
We live in an electric universe.

 

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Why the power transformer failed?, posted on June 5, 2024 at 08:12:28
Chip647
Audiophile

Posts: 2693
Location: The South
Joined: December 24, 2012
 Excessive heat causes the winding insulation to melt and short out.

Why excessive heat? Could be a lot of factors. Higher wall voltage (125v vs 110-115 specked) The transformer may have been run close to its maximum capabilities which causes excessive heat damage over time. Capacitor failure/higher current draw. Tube failure, etc.

 

RE: Why the power transformer failed?, posted on June 5, 2024 at 10:04:07
6bq5
Audiophile

Posts: 4564
Location: SF Bay
Joined: August 16, 2001
 I had an old HH Scott 299B where one of the large ceramic resistors failed and took the whole unit down-
Happy Listening

 

RE: Why the power transformer failed?, posted on June 5, 2024 at 14:53:25
reuben
Audiophile

Posts: 1649
Joined: September 28, 2004



I suspect there was a manufacturing defect in the transformer itself. It was like that when I got it second hand. If/when I find the sales receipt, I'll ask the manufacturer, assuming they're still in business, how many of those trannies they built.
BTW, It was about 40 years ago I took the defective part to the TV repair shop, and the old timers there were very helpful. They told me what voltages I needed, and that it was 'standard stuff' and I should be able to find something that would work. I got the X-101-B going with a bigger transformer from a Zenith color TV that had everything I needed and then some, but no center tap on the high voltage secondary. A bridge rectifier and safety ground wire took care of that. The mod required no 'hacking'- the transformer fit perfectly with only two fasteners kitty cornered, and the bridge was fitted with the right size pins to plug into the tube socket. The worst of it all was when turning it on, the tubes got hit with high voltage before the heaters warmed up.
I listened to it for a few weeks and found it very nice and sweet. I will be putting it back to its original configuration.
I started this thread to see if I may have something rare and possibly $ valuable.
Dark energy? Ridiculous!
We live in an electric universe.

 

RE: Why the power transformer failed?, posted on June 5, 2024 at 15:06:47
reuben
Audiophile

Posts: 1649
Joined: September 28, 2004



After re-reading your post, I do remember that I also needed to stuff one of the big cans with fresh caps. I don't remember if anything was shorted.
This photo is from 'the usual' or 'common' X-101-B in an epay listing.
Tom

Dark energy? Ridiculous!
We live in an electric universe.

 

Power transformers fail due to bad filter capacitors in the power supply!!, posted on June 21, 2024 at 09:12:33
Ralph
Manufacturer

Posts: 4839
Location: Minnesota
Joined: April 24, 2002
 Do not try to run this with a new power transformer before replacing all the filter caps in the power supply or else you'll see a new transformer burn up!

This is a common problem with all vintage electronics. Filter capacitors go bad over time (over 20-25 years=suspect) and when they fail they absorb current which increases the load on the power transformer to the point it overheats.

This amp was on borrowed time 30 years ago.

Do not pay attention to the other remarks on this thread (so far) - Fisher made good transformers and there was nothing wrong with its design or execution. Someone simply didn't know what I'm telling you here and ran the amp with bad capacitors.

 

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