My 500B Restoration/Modification Pictures

1rebmem

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With the help of so many contributors on this thread making it possible, I thought I'd show some photos of the restoration and modifications so far. I bought this 500B off Craigslist. My first Fisher. I heard it operate at the sellers house. Then home to the garage it went, hasn't been inside the house yet.
It is just about up to standards for the living room! Face plate needs to be reinstalled still.
The pictures will be in somewhat random order, as I take them.
Jef



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All can caps were restuffed.



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It's got some EH 7591's I bought 10 years ago and never used. NOS tubes ?
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My power tube adjustment panel. IBAM has been installed. Some nice quality trimmer pots.DSC01124.JPG



EFB board minus the EFB power supply. The power supply is mounted separately on a solder terminal to keep the board small. The 4 resistors in a row are the 15K's for IBAM. This board is mounted "upsidedown" in the chassis for mounting convenience.
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Unity buffer op-amp board. Also, the power supply for it is separate to facilitate a small board that can be tucked in along side the volume control, which keeps the wiring short as desired. I also implemented the Preamp Out/Amp In mod where the SpaceExpander jacks were. I also bypassed and de-terminated the remote control jack on the rear of the unit. I saw no use for it and thought it could become a problem if the plug/socket got loose etc. That supplied the shielded cable for the Preamp Out/Amp In mod.
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Here we see the EFB board mounted and all the standard other stuff. 1/4w 10 ohm Dale cathode resistors.
100ohm screen resistors. The famous Russian PIO's .068uF 400v to go with the new 220K's. I moved the 1.2K 7w resistor from the power tube area to the power supply section, just seemed where it belonged. The 4 small blue caps are part of IBAM, but mounted off board, again to keep the board small. The two light blue 390K 2 watt resistors were installed as part of the Phase Inverter Noose Removal mod. They feed the lower B+ to the AF stage required by noose removal. I don't care for flying resistor leads so that's why they're added. 2 watt cause I had some. DSC01156.JPG

All electrolytic caps replaced.
All brown turd caps replaced
AC power safety cap replaced and PT secondary cap replaced
Selenium bridge replaced.
The 2 main rectifier diodes replaced
B+ voltages are close to schematic, slightly high
Filament voltages within 5%
LED lamps installed for dial glass
IBAM, EFB and Unity Buffer installed
Phase Inverter Noose removed

Next: Phono PEC replacement and ???
If anyone has suggestions please let me hear.

Thanks... jef
 
Super work Jef! The trimmer pots you used and the plate you mounted them on looks absolutely first class! I'm sure you're enjoying your 500B immensely --

Congrats on a job very well done!

Dave
 
Nice work! Any chance you could share what you did for the EFB and Unity gain/op amp for the 500B? (schematics, wiring, components lists?)

I've seen the schematics and read the dgillespie writeups for the 500C several times and was able to add on an IBBA, but am struggling to adapt the EFB/Unity to the 500B.
 
Thank you Sam and all the others for the comments.

Sam,
I built everything to the modified 500C schematic, exactly.
The IBAM, EFB and the Unity Buffer.

I installed IBAM and EFB at the same time. Then installed the Unity Buffer without implementation of the Preamp Out/Amp In jacks.
Then later rewired the Space Expander jacks into the Preamp In/Amp Out.
The only decisions other than board layout was the grounding locations of the circuits.

http://akdatabase.com/AKview/albums/userpics/10007/Fisher 500c EFB & IBAM mod11.pdf

I made a BOM from the schematic, on scrap paper, which is already in the trash somewhere.

Feel free to ask any additional or detailed questions, I'd be happy to help.

Jef
 
Thanks Jef!

That you followed the 500C schematic exactly is a great start for me. I'll gladly take up the offer for questions as I proceed!
 
Jef,

Share the part number for the iBAM trimmers you used? I think on my up coming builds I'll follow your lead and move everything but the trimmers and test points into the circuit.

Re: Pre-in/out mod with the reverb loop. Would it be possible to have the capability of powering down the phase inverter / power output section of the receiver when used as a preamp? Any reasons to or not to take this approach? I'm sure those in hot climates would appreciate turning the heater off when not in use.
 
Where is the schematic for rewiring the reverb jacks into preamp-in/amp-out jacks? Thorne
Thorne, The 500C modified schematic that you have is the best drawing for the jack rewiring.
As with all schematics, it won't show the actual wire by wire connections. So you have to study the schematic and study your chassis wiring to make a mental (or on paper) wiring diagram.
As I mentioned, I installed the unity buffer without the jack rewiring, initially, and did the jack rewire after the unity buffer was working perfect.
Because if I did both together and had a problem, now I have to figure out if I built the unity board wrong or rewired something wrong. Less stuff to look at if there is a problem.

My suggestion is for you to do the same. That way the forum can help troubleshoot easier if you needed help.
Once you have unity buffer working, we can help with the jack rewiring because how you ground the shielded cabling is important.

Jef
 
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Share the part number for the iBAM trimmers you used?
Matt, from ebay I bought "Trim Pots Military Panel Mount 10K Ohm BOURNS#260L-1-103".
I just searched for a quality panel mounted 10K trimmer pot. I prefered a greater than one turn pot. I'm sure you could buy 25K pots and tweak the circuit resistors to work.
I have made IBAM's on guitar amps and used 25K and 50K pots.

Going into, it I wanted the bias pots and test jacks accessible from the rear with the wood case installed.
I also prefered the smallest perf board I could manage, due to space and looks (even though I'm the only one seeing under chassis).
Because EFB controls power tube bias voltages also, I put IBAM and EFB components on the one board. Some other components are mounted separately in the chassis like the 4.7uF cap's (the blue ones by the new 220K resistors). I mounted the power supply components for EFB on a 5 lug solder terminal strip and mounted it separately.

As Dave would say....I hope this helps!

Jef
 
Very nice work, Jef. I particularly like your top-of-chassis bias set up. I went through similar with my 400 mods, but haven't taken the plunge to rewire the reverb jacks for "pre-out/amp-in" yet. Probably will when it goes in for a check up. I was very impressed with what the mods did for the sound and (cool) operation of my prized 400.

Just finished some work on a 500B for a fellow and that reminded me of how nice a receiver they are. His had the Russian PIO's installed when I got it and after a few hours of listening, I'm thinking they sound very nice (and I'm not a guy who claims to hear much/any difference among coupling caps).

Enjoy!
 
Wow - that is some excellent work - congrats!

Hopefully, one day my 500B will receive this treatment!
 
Jef -- Be sure to check out the recent thread for revisiting the Fisher noose as it relates to the 400 and 500/800B receivers. It explains how the old procedure simply came to be all on its own accord without really being vetted, while the modification offered in that thread is the real deal that will ensure maximum performance from any driver tube you decide to use.

Super work!!

Dave
 
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