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Fisher CA-800 Rebuild Thread!

Bassblaster said:
So i would poke across pin 8 and 3 right?
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Hey man, been reading this thread, as well as watching your Youtube vids on this build. Got a question I'm sure you can answer, I have the 880, and the schematic and P to P wiring diagram both show an STK 0080, but the parts breakdown shows an STK 0080A, which is a bit different pack. Will either one work? I don't think they are interchangeable, but I'm not 100% sure.
 
im not 100% sure, i researched the 880 version alot awhile back. i think the A version adds a couple diodes and resistors to the bases of the final outputs, and resistor across the drivers inside the chip. the input side of the pack (where it solders to the PCB) should be very close if not the same
 
Bassblaster said:
im not 100% sure, i researched the 880 version alot awhile back. i think the A version adds a couple diodes and resistors to the bases of the final outputs, and resistor across the drivers inside the chip. the input side of the pack (where it solders to the PCB) should be very close if not the same
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I think the thermal tracking is on board.
 
rcs16 said:
I think so, but I'd would use the replacement we re-designed and not an unknown knock off.
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I completely agree, and if I was planning on using this unit for its intended purpose, I'd buy the re-designed packs, but all I really need is for the VU meters to work. I plan to use the preamp in it to drive my rack mounted amps with.
 
The A version is a 3EF design so it will have a lower THD with a <4 ohm load as it does not load down the VAS a much.
Sure if all that is wrong is the VU meters, then no need to use new modules.
VU problem is electronics or mechanical in nature?
 
rcs16 said:
The A version is a 3EF design so it will have a lower THD with a <4 ohm load as it does not load down the VAS a much.
Sure if all that is wrong is the VU meters, then no need to use new modules.
VU problem is electronics or mechanical in nature?
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Electronic issue, when I got the unit, the internal fuse on the power switch was jumpered with a piece of wire, YAY!! The left channel doesn't play, both, speaker out and headphone, and the left VU meter didn't work either. right channel played, VU meter worked, but sounded bad, as if the power pack was going out. Pin 2 of the 0080 goes to a jumper on the PCB, the actual trace on the PCB was burnt in 2. So I soldered in a jumper to fix it, replace the main power fuse, and instantly began blowing that main fuse, which tells me the power pack is shorted. I then removed the jumper I added to the PCB, and the fuse stopped blowing, but no response from the right channel now, output, or VU meter, and the test speaker i had on the right channel was done. I assume I finished off the power pack, but it was previously replaced at one time along with the emitter resistors.
 
Guest153 said:
Electronic issue, when I got the unit, the internal fuse on the power switch was jumpered with a piece of wire, YAY!! The left channel doesn't play, both, speaker out and headphone, and the left VU meter didn't work either. right channel played, VU meter worked, but sounded bad, as if the power pack was going out. Pin 2 of the 0080 goes to a jumper on the PCB, the actual trace on the PCB was burnt in 2. So I soldered in a jumper to fix it, replace the main power fuse, and instantly began blowing that main fuse, which tells me the power pack is shorted. I then removed the jumper I added to the PCB, and the fuse stopped blowing, but no response from the right channel now, output, or VU meter, and the test speaker i had on the right channel was done. I assume I finished off the power pack, but it was previously replaced at one time along with the emitter resistors.
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Since it had a shorted power pack and a shorted fuse I bet the rectifier was running nice and hot. I don't remember but at least with the 800 I don't think the metersn are driven from the output I think it rides of the preamp board. But don't quote me on that
 
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Bassblaster said:
Since it had a shorted power pack and a shorted fuse I bet the rectifier was running nice and hot. I don't remember but at least with the 800 I don't think the metersn are driven from the output I think it rides of the preamp board. But don't quote me on that
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I read somewhere in one of these threads that the meters are driven by the power pack. Im not gonna use the unit to drive speakers with anyways, gonna use it as a preamp driver for my rack mount amps.
 
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