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Fisher CA-800 Rebuild Thread!

Bassblaster

Bassblaster

Super Member
Not to be confused with the CA-880

I have wanted the 880 or 800 for the better part of 8 years, and now that i got one i plan on fully rebuilding it.

To start the unit i have has been worked on before. one of the STK-0080's have been replaced, some caps in the pre amp board have been shorted and the main board is even BROKE!
my current plans are to fully recap it, fix the preamp bodges, replace the burnt out lights, attempt to fix the broke board, replace a half burnt headphone dropping resistor and the best part...Replacing both the STK-0080's with all discrete parts designed by user rcs16

If anyone wants to follow along the manual is here. https://www.hifiengine.com/manual_library/fisher/ca-800.shtml

Pics Below!
Replaced STK Pack (Right one)
IMAG0324[1].jpg
Broke Main PCB
IMAG0402[1].jpg
IMAG0399[1].jpg
Burnt headphone dropping resistor.
IMAG0398[1].jpg
Shorted caps in pre amp.
IMAG0396[1].jpg
IMAG0397[1].jpg

Let the fun begin!
 
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I own the 880 and I personally also replaced one of my STK's a few years back. It still works strong both channels, and I even have a couple of (what looks like) scorched resistors but it still works fine.

Your broken circuit board is an easy fix. Just scrape off the green coating with a knife or Xacto blade at all of the cracked junctions and then just run solder across all of the scrapes. I had one like that in a different amplifier except mine was way worse than the one you have showing.
 
cademan said:
I own the 880 and I personally also replaced one of my STK's a few years back. It still works strong both channels, and I even have a couple of (what looks like) scorched resistors but it still works fine.

Your broken circuit board is an easy fix. Just scrape off the green coating with a knife or Xacto blade at all of the cracked junctions and then just run solder across all of the scrapes. I had one like that in a different amplifier except mine was way worse than the one you have showing.
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Yeah the break will be pretty simple because it only has 1 trace on it.
 
Well first things first, ive been the past day building up the Mouser parts list. i got all the caps down except the main filters, will come back to those. now in an attempt to help the god awful noise floor this unit has, would swapping out the JRC 4558DX op amps help that any? if so what would be a good choice? at first i looked at the NE5532 but that chip has been around for some time and there may be better ones out there that i dont know about.
 
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The 'high leakage' C11 / C12 caps above are on both channel outputs from the Tone Control IC-01 - so the IC must be a ? now.

I've not had any problems with NE5332's, but in terms of changing IC's, I'd just note that the supply voltages are quite high for some of them (up to +/- 20 - 21V), so might need adjusting if you change any.
 
Yes the factory op-amps appear to run on quite high voltage. ill test those here in a bit, but first how am i supposed to go about getting these burnt out light bulbs out? the plastic housing is cracked on both of them.
IMAG0616[1].jpg
What is on this bulb?
IMAG0618[1].jpg
Mmmmm...Tasty! Notice C08 is bulging
IMAG0619[1].jpg
 
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Mmmm... That glue they used in the 80's - 90's that turns black and conductive over time. Causes all kinds of havoc. I'd guess that stuff on the lamp maybe some form of dried up human slime, or glue... as for the bulbs looks like you just pull the black holder out and then unscrew or pull the bulbs out.
 
If you're lucky - maybe the yellow (glue ?) will soften if you heat it..... hopefully enough to remove the bulb & holder together. The bulbs & holders can be replaced fairly easily I would have thought, the plastic housings are much more difficult to replace if they're damaged....

If you're unlucky, and they won't move, it may be safer to unsolder the pcb end of the lamp wires, and remove the bulbs + holders + plastic housings to repair separately on the bench....In either case - I'd be very wary of trying solvents on that white plastic - ethanol or IPA are probably OK, and may soften the glue if that's what it is, but I'd avoid acetone or any of the ketones, as well as any paint thinners, and I'd certainly check any solvent first (I'm a chemist).
 
I got the meter lights out, only broke off a little piece, buts its not enough to worry about mounting. what i want to do here is since all the lights run from the same transformer tap, why dont i just put a bridge rectifier on it and replace all the lights with LED's. put some big 10mm cool white's for the meters and 5mm for the rest. Good idea?
 

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LED's would certainly run cooler on the meters - did you check dgwojo.com yet ? I think he's usually the forum 'go to' guy for all things lamp & LED related, and there's examples on his site.
 
Goldie99 said:
LED's would certainly run cooler on the meters - did you check dgwojo.com yet ? I think he's usually the forum 'go to' guy for all things lamp & LED related, and there's examples on his site.
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Oh yes, i think im going buy from him whenever i finally finish my Pioneer SX-636. but for this it may be cheaper to buy the LEDs from Mouser. only about 30 cents a piece.
 
Don't forget to put a smoothing capacitor across the outputs for the lamps. Don't want any flicker!
 
Ummmm...this doesnt look like the other bulb
IMAG0621[1].jpg
Eastham said:
Don't forget to put a smoothing capacitor across the outputs for the lamps. Don't want any flicker!
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Yep! ill build a full wave bridge with a filter cap on it. need to pick my LED's before i can figure out what dropping resistor ill need.
Maybe i could put a 3.3V regulator?
 
holy jesus the rail voltage is +/-63V!! thats 8V higher than the manual shows
EDIT: both op amps (IC01 IC03) run on different voltages. ones at +/- 18V the other is at +/-21V
Wonder if i could modify the power supply to drop that to say +/-15V
 
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