• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Need expert advice on a vintage tube amplifier- !!!

Hello, I am in great need of help, as a diy Newbie i just don't know enough. I have a Vintage Tube amplifier - It's a Fischer Integrated Tube Amplifier that is missing the main Input Transformer, How easy is it to find a modern replacement and will it hurt the performance of the amplifier compared to the original main input transformer? It still has the two Output transformers, can it be saved? And what company would you recommend? -- -- Thanks, Dean
 
Hi, First - thanks, Cal,
-- sorry the Model is a -- Fisher X-101 B stereo 7591 ... thanks

Definitely go to Heyboer. The odds are long that they already know what goes into a Fisher X-101 B.

Member Tom Bavis may be able to help out in providing a schematic for the unit.

This much I can say, current production 7591s are intolerant of the liberties Fisher took with grid to ground resistance limit. Fortunately, the foundation of a good solution to the problem is provided in Fisher's earlier X-100. Use the 7247/12DW7, instead of the 12AX7, in the O/P section.
 

Attachments

  • Fisher X100 part 3.jpg
    Fisher X100 part 3.jpg
    401.9 KB · Views: 209
Probably an obvious point, but if you are new to this amplifier, and the transformer was kaput or missing when you got it, then it is worth considering that the failed/missing transformer was a symtom of another problem. I.e. don't just fix the new transformer, and switch on without due diligence.
Also, if it has been many years snce the amp was last powered up, you might need to consider bring up the power slowly over an extended period to enable the electrolytics to reform.
 
Hi, thanks Kevin and Eli , I sent a message to Heyboer to see if they can help... and thank you for the info on the 7591 tube problem as well. I also appreciate all the other suggestions / help too. I don't know what else might be wrong with it - If I can find a good transformer for it , I was planning on replacing the caps just to be sure and to then after some more checking of the resistors and etc. , to power it up slowly. I will let you all know what Heyboer's reply is as soon as I hear from them.
 
My policy with old electrolytics is scorched earth, I'm tired of catastrophic failures minutes to months after putting an old piece of gear back into use. Replace them all, you'll be much happier.

Replacing the coupling caps to the output tubes generally are a good investment in that they keep old leaky caps from upsetting bias and frying your new output tubes.
 
I was originally thinking this would be a worthwhile tube amplifier - It seems to have a good reputation online...... but if I can't find a good price on a suitable replacement transformer, is there another reasonably priced amplifier that will perform as well (or Better) - that can be recommended?
Or also a schematic of an amp that sounds as good- (or Better!) that I could tackle that isn't to much more complicated and doesn't cost an arm and a leg.....
-------- (I already gave up one of my arms and legs for the preamp - and I need at least one of each to do any other builds or repairs) -- :D

Thanks, Dean
 
Last edited:
What sort of mounting method did Fisher use for the power trafo? If it's drop through, a Dynaclone PA060 might fit and definitely could be adapted to the task. I've previously mentioned this possibility for Scott 7591 units. Scan the archives here and over on AA.

Moderately extensive, but quite manageable, PSU design changes would be necessary. For instance, Fisher used "full wave" voltage doublers, but FWCT topology is used with the PA060.

If all else fails, salvage the excellent O/P "iron" Fisher used and install it in a new chassis. A suitable toroidal power trafo can be sourced from AnTek, at modest expense.
 
Hi Guys , I got sick and have been out of commission for quite a while , getting old is no fun , my body doesn't seem to want to cooperate with the program - lo

thanks for the good advice , I'll check into the other suggestions, I may have to salvage the output Iron and use it in another design.
 
Last edited by a moderator:
I had to repair an old Dynacord guitar amp with a kaput transformer, and I ended up getting Toroidy to make a custom one, which was around $130 if I recall correctly. I used a bit of the plate you get in builder's merchants to mount it (the old one was drop through) and it was fine! If you know the voltages it should not be such a big deal to find something equivalent.
 

gain wire

Member
2004-11-27 4:04 am
NCR
Hi Guys , I got sick and have been out of commission for quite a while , getting old is no fun , my body doesn't seem to want to cooperate with the program - lo

thanks for the good advice , I'll check into the other suggestions, I may have to salvage the output Iron and use it in another design.
Hallcon, wishing you to get better. May your mind bring you comfort if your body cannot.
 
Quit malingering and get back to work! Also get well. Glad we concluded that so gemutlicht.

These Golden Age amplifiers are a real challenge to decide what to do with (pardon the dangling p.). We'd like to keep it as original as possible, but it was designed for a different line voltage, and is half a century old. Sometimes you might find one that wasn't brutalized and has working power supply caps. (Many will rightly object here, but it does happen.) But mostly, the whole power supply is too old and doesn't meet modern safety guidelines.

Whatever you decide to do, you need the result to be up to modern Class 1 safety standards (you're responsible for every bullet) and this is pretty easy. A lot of us also feel (some) responsibility to keeping a vintage piece alive, if possible (within your own definition of possible, of course). That's tough sometimes, and seems extremely tough in your situation. All good fortune in health and amplifying,
Chris