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blowing fuse - Peavey CS-800
blowing fuse - Peavey CS-800
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Old 10th December 2017, 04:05 PM   #11
Enzo is offline Enzo  United States
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Peavey didn't change from complementary to quasi and back, as that would have required completely different boards.

It may not say X on it, but if it has the wind tunnel in the front panel, and one large board for all the power transistors that is almost the size of the chassis. Then use the X drawings. The older four space units had two power modules inside, each with a driver card underneath. The X model has the single large board with the two driver cards. And the wind tunnel.

it is easy not to spot that some of the 83140 are really 73140.

The old style had only two ICs on the driver card, not four, and no 87478. The X has the four, including an 87478.
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Old 10th December 2017, 04:51 PM   #12
indianajo is offline indianajo  United States
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Thanks Enzo.
If there is a picture of Andy's unit, my browser is hiding the link. Oh, well.
I'm a volunteer church musician too, piano/organ. I had to take off this month; hit the street off my bicycle and shoulder muscle hasn't healed up yet. I was looking forward to playing all the Christmas music I know today while the families ate their holiday dinner after the service.
If you can't find a 100 W light bulb tungsten, or 300 W in mogul base even better, some other 250 W 6-10 ohm resistor might work. Some people use coffee cup immersion heaters. Some use tea kettle boilers. Or you can buy a couple of 8-10 ohm 225 W logs (wirewound resistors) (useful for power testing afterwards) or build one out of 5 W to 50 W resistors on a board, depending on what wattage is cheap that day. I've got a sack of 10 ohm 3 w that were $.03 each, but I bought the logs back when they were only $10. The room heater, the tipover switch failed, and I threw it in the garage, turned out to be just the thing for the PV-1.3k. Had spade lug terminals on the heater element already.
If you've got time and no parts until Wednesday, build a Iceo tester for the output transistors to see if they are stressed. You'll need alligator clip leads, the one thing that radio shack used to have that was any good. Mcmelectronics had them but they just moved all the warehouse contents to newark website and I don't know how to find them anymore. The Fluke ones are about $25 each, which is rediculous. But they are rated for 600 VAC.
Iceo tester, you get a 12 to 32 v power supply, best a surplus wall transformer from the charity resale shop. Don't have one of those, use a 24 V doorbell transformer and a bridge rectifier (& fuse) and an old electrolytic capacitor. Or a pre-microprocessor car battery charger plus a capacitor. Use the DC ammeter of your DVM series a 4700-20000 ohm resistor. Connect + to case - to emitter for npn and opposite for pnp. Emitter is the pin on the right looking from the long end on TO3 cases like MJ15024.
More than a few microamps, that transistor is leaky and needs to be pitched. Of course you first did the double diode test at 2 v, with the dvm, to screen out shorted and totally open parts already. base to C & E should be 450-600 mv one way on good TO3 transistors, ----- the other way. Small transistors & diodes can go 750 mv (ohms the meter shows) But 2 v test doesn't screen stressed transistors that might blow up under 81 v.
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Last edited by indianajo; 10th December 2017 at 05:06 PM.
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Old 12th December 2017, 08:03 PM   #13
Andyman001 is offline Andyman001  United States
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update:
removed triacs and reassembled amp. tested with bulb limiter in series (twin fixture with 2 100w bulbs) smoked a resistor and tantalum cap on Ch1 side of main board, will try to post a pic.
edit:
looks like "1R120" & "1C106", according to the CS800X prints

Last edited by Andyman001; 12th December 2017 at 08:23 PM.
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Old 12th December 2017, 08:13 PM   #14
Andyman001 is offline Andyman001  United States
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pics

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DSC02548_zpseo2w2it0.jpg Photo by bassfiveman | Photobucket
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Old 29th December 2017, 01:47 PM   #15
indianajo is offline indianajo  United States
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I can't spot them on the schematic after 15 minutes.
Your picture shows the blown part near the zobel coil, so it is in the output somewhere apparently. You might not have total meltdown yet. Maybe just the cap shorted, it looks pretty old. Peavey buys better e-caps than many, but 20 years is a long time for any e-cap. I shotgun them all, after I figure out what is wrong with the amp and can I fix it.
Since there is a speaker disconnect relay, what is the DC voltage on the input of the relay (pin 1) or the output of the zobel coil with the amp on the limiter? If more than about 200 mv you have an output transistor problem and could profitably start pulling them off and testing them.
One key question about this unit if the OT's are gone, is the transformer okay? Loading it with a 225 W 8 ohm resistor can give you an answer and save a lot of grief if you find out at the end it has a shorted turn. If so, blown amps are cheap on e-bay.
Usually output transistors are replaced in sets, because they have to match Vbe at all temperatures to share the current load equally. If you buy them from Peavey, sometimes you can just replace a few blown ones. They have their own matching procedures.
Commercially, they OT's are MJ15024/25 which are about $4.50 ea. I used MJ21193/94 since they were $1 cheaper and 19 of my 20 were blown or stressed (leaky under 12 v Vceo).
Usually blown OT's take out many of the emitter resistors, too. Measure them with the OT's out, they don't stress like transistors do.
On my unit the blow up took out the VI limiter sense resistors like R105 & R107, plus the VI limiter transistor and associated parts. (Q105 & q1060 I used MPS8099/8 as replacement transistor since I could get those cheaply. MPSA06/56 might work too. 2n5551/5401 are another even tougher possibility, since your only buying one each and freight is 1000% what the transistor price is.
If output transistors are completely blown, usually the 75 v leaks out the base line and blows the drivers and maybe the input section. If your unit has 350 v rated MJE15032/33 drivers per the service bulletin, maybe not. Mine had the 2SA/2SC drivers and they were blown. The drivers are TO220 package parts on a heat sink.
Most of my predriver transistors were blown and a couple of the op amps. Not expensive but tedious to replace. also the 50 v rated ceramic caps around the op amps.
When buying parts try to get $50 or more in a box. If you buy onesies major dirtributors tend to hit your with a stocking charge. Ebay transistors have a high percentage of fakes, don't bother. Majors in the USA are newark digikey mouser alliedelec, avnetdirect arrow
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Last edited by indianajo; 29th December 2017 at 02:02 PM.
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Old 29th December 2017, 03:49 PM   #16
Enzo is offline Enzo  United States
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Of course it can happen, but in my 30 years as an authorized Peavey repair station I can count the number of power transformers I had to replace in their power amps on one finger. Yes, just one.

Quote:
looks like "1R120" & "1C106", according to the CS800X prints
The schematic just calls them R120 and C106. Note there is only one power output stage schematic for the two identical circuits. The 1 is added before the part number on the layout drawing, because there is a R120 on each channel, hence 1R120 and 2R120. R120 goes base to base across the opposing driver transistors. Look left side of the power stage drawing. Right next to the double diode.
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Old 4th January 2018, 03:13 PM   #17
Andyman001 is offline Andyman001  United States
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Thanks for the replies, I will probably have some time to work on this next week.

would I be able to put power to just the power supply section if the Xfmr, or the power supply caps are bad?
I was able to power it up (before the latest mishap) and run just the fan, with no issues.
(again nothing hooked up to the output board)

Thanks, Andy
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Old 4th January 2018, 09:37 PM   #18
indianajo is offline indianajo  United States
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Peavey used .250" flag terminals in those days for heavy current to/from capacitor-rectifier board. So you should be able to mark the terminals, pull them off and wrap with tape if necessary, then test each component individually. I connected my 8 ohm 225 W resistors directly to the transformer, for example. I have 12 ga wires soldered to the resistors, then flag or bullet terminals crimped to the other end to plug into the power source. The resistors don't care if they receive DC music from the output transistors, or AC fed from the transformer.
The burnt inter-base resistor tend to indicate your drivers probably are blown. DCV going into the speaker relay from output transistors is the smoking gun.
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