Most Common Parts Needed For Fishers!

[Mark Davis]

I put mine on each leg of the PT primaries and used CL80s - others may do it differently but it seems to work well - X marks the spots - in series.

 

[MARCO VARI]

HI to all, someone hss a rebuilt list for fisher x100 and x101b ? thanks

 

[geedaddy45]

Courtesy of DREWBOLCE (It's his drawing!);



IBAM (Individual BIAS ADJUSTMENT MODIFICATION) PARTS LIST AND SCHEMATIC. Mainly for the 400-500C-800C. I don't see any reason it won't work with slight modifications for other 7591/7868 based FIXED BIAS units. Matter of fact i modified this for my Sansui 1000A (changed resistor value) and it works just fine. R117-R120 are the Grid resistors that are changed( were originally 330K) for use with primarily the EH and JJ variant's. Make sure the coupling caps are changed to .1uf (see edit at bottom) when the resistors are changed.

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ON THE 400.

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On the 800

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And now we have Dave Gillespies Balance/BIAS board. It's basically a universal variation (my words not his) of what FISHER did in in their higher ended amps/integrated. You balance the pairs with 2 of the pots (one per side), then set the BIAS. You get the BIAS improvements of Drews board, with a null when balancing out the pair (null meaning 0.00v) to equalize the loads. I've used both, and with an UNMATCHED QUAD, Dave's board works better to equalize the tubes. With new matched tubes from McShane, it's 6 of 1, 1/2 dozen the other. In any event BOTH WORK WELL, and I'll leave it up to you as to which one you use.



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EDIT on 01-09-2022. about 6 years late, but better late than never...... NEW VALUES FOR THE Grid return resistors (330K originally), and coupling caps (0.047uf originally)! 0.068uf and 220KΩ maintain R/C timing of the original parts to within 2%. This is for ALL TUBES regardless of age (old stock or new stock). HOWEVER!!! If you use and IBAM or IBBA to vary the bias and have it set to 75% to 80% of maximum dissipation of the 7591's, no changes to the grid returns and coupling cap values are needed.

Hello Larry,
I like the simplicity of DB's IBAM circuit and would like to use it on my 800C. Since this post is one of the most current, I replied to it/you. I've included my edited version of that IBAM circuit specific to 800C. Identifiers, and values of existing components in ( ). One question I have is the omission(?) of C14 and C15 highlighted in green on original schematic. Are these not needed after the mod or just left off this example? The red marker on the original is where the IBAM will be inserted. Your opinion is valued on this mod.

 

[larryderouin]

Leave C-14 and C-15 alone. They aren't germane to the installation / modification and were left off for that reason.

 

[raychwv22]

Fisher/Sears model 143-92543800. Any tidbit of info for finding a repair/schematic manual?

 

[DeRoadie73]

Fisher/Sears model 143-92543800. Any tidbit of info for finding a repair/schematic manual?

I'm in the same boat my brother! My buddy has one he wants to service and give a loving home as long as it will hold out but he is pretty new to servicing audio components and one of the things he told me he had already done was he turned the bias screws just to see what they were ..(DOH!) So if you locate any info schematic etc I would deeply appreciate either a copy or a link so can help my friend out.

 

[grindfix]

RUBBER GROMMET's for the PHONO STAGE Tube isolation. This will minimize any chassis vibration from getting into the tubes and being amplified. Also good if you have a somewhat microphonic tube and don't want it picking up chassis noise. The originals are for the most part, dried out, crusty, dusty, and generally no good.

It's a Keystone part. Rubber Grommet .187 P/N 534-730. This is @ Mouser. The fit is exact and no fussing with over or undersized grommets.

Mouser pricing as of 03AUG2014
1: $0.18 ea
10: $0.175 ea
25: $0.149 ea
100: $0.108 ea
250: $0.093 ea
500: $0.089 ea
1,000: $0.078 ea
2,500: $0.071 ea
5,000: $0.067 ea

These are out of stock at Mouser.
Very similar on Amazon here. 300 of them for just over $7

 

[madwing]

These are out of stock at Mouser.
Very similar on Amazon here. 300 of them for just over $7

link error, @grindfix

 

[grindfix]

Fixed it