Newbie here,
I've learned a lot reading past threads, as title says, I have acquired a Peavey CS-800, 2nd version i believe, (4 ohm min, 400 watts per channel, Wind tunnel)
had a open main fuse, replaced, blew pretty quick (with sparks from under the main (output ?) board; upon inspection I found the large resistor on the power supply board loose and overheated - re soldered; and the triac (SAC-187) on the "A" channel shorted, and the trace on one of the legs blown open.
Questions:
1. Where do I check rail voltage? (like I said newbie). i have reinstalled the power supply and hooked up the fan, it powers up and fan comes on.
2. I should be able to hook up the "B" channel to test, Correct? or should I just wait for the replacement Triac and test both?
any and all advise welcome.
Andy
(I have about 15 years as an industrial electrician, so know how to be safe around electricity)
I've learned a lot reading past threads, as title says, I have acquired a Peavey CS-800, 2nd version i believe, (4 ohm min, 400 watts per channel, Wind tunnel)
had a open main fuse, replaced, blew pretty quick (with sparks from under the main (output ?) board; upon inspection I found the large resistor on the power supply board loose and overheated - re soldered; and the triac (SAC-187) on the "A" channel shorted, and the trace on one of the legs blown open.
Questions:
1. Where do I check rail voltage? (like I said newbie). i have reinstalled the power supply and hooked up the fan, it powers up and fan comes on.
2. I should be able to hook up the "B" channel to test, Correct? or should I just wait for the replacement Triac and test both?
any and all advise welcome.
Andy
(I have about 15 years as an industrial electrician, so know how to be safe around electricity)
There are various versions of these. On the version B schematic I have, the triac on the channel is the DC protection triac, that detects DC on the output and blows the main fuse to protect your speaker from burning the coil insulation or tearing the suspension. So the triac is the last thing you want to replace, after everything else is perfect. That means no DC on the output and passes sound okay into a trash speaker through a 50 uf plastic cap. (to protect the speaker from dC).
If your this new, lesson one is don't ever measure voltage with two hands. Current across your heart over 24 v can stop it. Use a clip lead on the negative probe to speaker ground. (On the back). The speaker ground of the channel you are working on. Many Peaveys have different returns for the two channels : version B probably is not since it is quasi comp.
Next safety tip, use safety glasses desoldering, solder can splash. Also powering up, metal can transistors can blow the tops off at these voltages. Also E-caps can blow their tops and squirt hot borax water.
Likely somebody has pulled a 1/4 phone plug part way out, and blown the output transistors. With the triac out of the circuit, put on a light bulb box, replace fuse and measure for DC on the output. A light bulb box has a 100 W bulb in series with the power plug, to limit the current. If everything is okay, the bulb stays out and all the transistors power up and draw no current.
It is also possible, at this age, a DC power supply cap has shorted or a bridge rectifier has shorted. No +-50 on the mains caps (81 without the light bulb box) something is wrong around there.
The schematic I think I got from this website, so search around & see if you can find it. The CS800s and CS800x are pretty different, don't download those if you don't have one.
See also this repair thread: vintage amplifier repair/upgrade manual - diyAudio
In Idaho, your nearest full line distributor w/o counterfeits is digikey in Minnesota. I use Newark in SC but digikey has seemed to be okay the one time they had something unique.
These aren't worth a lot, but do have decent sound and can play 400 W/ch all day and night if the output plug is not shorted and the fan doesn't quit. You'll learn a lot by repairing it. I did my PV-1.3k. More fun than crossword puzzles and warmer in December than restoring cars or tractors.
Have fun.
If your this new, lesson one is don't ever measure voltage with two hands. Current across your heart over 24 v can stop it. Use a clip lead on the negative probe to speaker ground. (On the back). The speaker ground of the channel you are working on. Many Peaveys have different returns for the two channels : version B probably is not since it is quasi comp.
Next safety tip, use safety glasses desoldering, solder can splash. Also powering up, metal can transistors can blow the tops off at these voltages. Also E-caps can blow their tops and squirt hot borax water.
Likely somebody has pulled a 1/4 phone plug part way out, and blown the output transistors. With the triac out of the circuit, put on a light bulb box, replace fuse and measure for DC on the output. A light bulb box has a 100 W bulb in series with the power plug, to limit the current. If everything is okay, the bulb stays out and all the transistors power up and draw no current.
It is also possible, at this age, a DC power supply cap has shorted or a bridge rectifier has shorted. No +-50 on the mains caps (81 without the light bulb box) something is wrong around there.
The schematic I think I got from this website, so search around & see if you can find it. The CS800s and CS800x are pretty different, don't download those if you don't have one.
See also this repair thread: vintage amplifier repair/upgrade manual - diyAudio
In Idaho, your nearest full line distributor w/o counterfeits is digikey in Minnesota. I use Newark in SC but digikey has seemed to be okay the one time they had something unique.
These aren't worth a lot, but do have decent sound and can play 400 W/ch all day and night if the output plug is not shorted and the fan doesn't quit. You'll learn a lot by repairing it. I did my PV-1.3k. More fun than crossword puzzles and warmer in December than restoring cars or tractors.
Have fun.
Last edited:
Thanks for the reply.
I have downloaded schematics for the CS800;CS800s & CS800x, trying to figure out which matches mine. I already sent a request to Peavey support (day before yesterday) for correct schematics.
thanks for safety tips, will probably start tomorrow afternoon or so.
how I remove the triacs from the circuit? other than physically removing them?
thanks, Andy
I have downloaded schematics for the CS800;CS800s & CS800x, trying to figure out which matches mine. I already sent a request to Peavey support (day before yesterday) for correct schematics.
thanks for safety tips, will probably start tomorrow afternoon or so.
how I remove the triacs from the circuit? other than physically removing them?
thanks, Andy
An S or X model will say it on the front cover. At least my S does and there is an X for sale on e-bay now, with picture. S & X have op amps on the input, and full complimentary output transistors. If yours has quasicomp output transistors, all the output transistors have the same part number. Full complementary, one is one digit off from the other in pairs. In the early days Peavey didn't highlight model changes, like changing from quasi-comp (early ) to full complementary (late).
You disable the triac by removing the gate lead which is the right lead with the lettering up and the leads towards you. Alternately you can remove the diac next to it which triggers it, shown as sac187 on the schematic. Probably it should come out anyway, as if the triac shorts they blow up too, often. The diac breaks over at 7 to 8 volts, so you put a 12 v power supply in series with it, a 1k to 470 dropping resistor, and see what you measure, 7 to 8 if good. Of course if it is shorted it's bad without digging out the battery charger.
Sorry about any redundant safety tips, but this is the USA and people giving advice can be sued.
I found a replacement for the diac as Powerex bs08d, at Newark. Various people get huffy about names for the sac187, expect some argument.
Alternately you can buy them, plus all parts from Peavey. You have to call them though, they don't respond to email for parts. Or didn't 2 years ago. Peavey fans are probably better than any you can buy elsewhere. Also if you buy complete sets of output transistors, they've matched them at the factory already. If the OT's are blown, usualy some drivers predrivers & other stuff is blown one. The musicians won't quit plugging the amp in and turning it on just because it blew the fuse once.
You disable the triac by removing the gate lead which is the right lead with the lettering up and the leads towards you. Alternately you can remove the diac next to it which triggers it, shown as sac187 on the schematic. Probably it should come out anyway, as if the triac shorts they blow up too, often. The diac breaks over at 7 to 8 volts, so you put a 12 v power supply in series with it, a 1k to 470 dropping resistor, and see what you measure, 7 to 8 if good. Of course if it is shorted it's bad without digging out the battery charger.
Sorry about any redundant safety tips, but this is the USA and people giving advice can be sued.
I found a replacement for the diac as Powerex bs08d, at Newark. Various people get huffy about names for the sac187, expect some argument.
Alternately you can buy them, plus all parts from Peavey. You have to call them though, they don't respond to email for parts. Or didn't 2 years ago. Peavey fans are probably better than any you can buy elsewhere. Also if you buy complete sets of output transistors, they've matched them at the factory already. If the OT's are blown, usualy some drivers predrivers & other stuff is blown one. The musicians won't quit plugging the amp in and turning it on just because it blew the fuse once.
looks like it is later than i thought; 4 opamps on each board 2-5532; 1-TL072CP; 1-70487478;
output transistors - 8 pairs 70483180 & 2 pair 70481180.
according to this thread Peavey op-amp sub
i can use schematic for CS800x -correct?
output transistors - 8 pairs 70483180 & 2 pair 70481180.
according to this thread Peavey op-amp sub
i can use schematic for CS800x -correct?
Yes, wind tunnel is CS800X.
CS800S has a switching power supply and is totally different. The old CS800 series is one rack unit taller than the wind tunnel guy, and is also totally different.
If the triac is shorted, remove it. For testing, you don't need the triac. Work with NO LOAD until the amp is working.
Look at the schematic, the main rails are on the collectors of the power transistors, the cases.
CS800S has a switching power supply and is totally different. The old CS800 series is one rack unit taller than the wind tunnel guy, and is also totally different.
If the triac is shorted, remove it. For testing, you don't need the triac. Work with NO LOAD until the amp is working.
Look at the schematic, the main rails are on the collectors of the power transistors, the cases.
I don't think it is a CS800x. I just downloaded that schematic, and it is fully complementary, that is 4 70483180 and 4 70473180 per channel (Mj15024 & 25). If your output transistor board is all 70483180 it is quasi-comp. The 1180s are drivers, should be on a driver baord.
5532 and tl072 op amps are pin compatible with rc4580 & rc4560, and somebody might have substituted over the years.
One implication of emitters tied together to the speaker return, it is "flying ground" which means you work on one channel at a time with the negative probe if dvm clipped to speaker ground. The two channels do not have the same ground and speaker ground is not the same thing as case ground. The transformer has two windings to make the channel speaker grounds independent. This is done to make bridging easier. The op amp supplies derive from the rails, unlike other amps.
Does your unit have a DDT switch & light on the front? If not, definitely not an X. The DDT op amp has a weird pinout and drives a J174 jfet. It is hard to buy, hope yours is not blown.
The ebay cs800x does say that on the front. In big bold letters.
Next thing after defeating triac protection, is build a light bulb box or use a element from a dead room heater to put in series with the AC power, so you can test for DC on the output without blowing the fuse.
5532 and tl072 op amps are pin compatible with rc4580 & rc4560, and somebody might have substituted over the years.
One implication of emitters tied together to the speaker return, it is "flying ground" which means you work on one channel at a time with the negative probe if dvm clipped to speaker ground. The two channels do not have the same ground and speaker ground is not the same thing as case ground. The transformer has two windings to make the channel speaker grounds independent. This is done to make bridging easier. The op amp supplies derive from the rails, unlike other amps.
Does your unit have a DDT switch & light on the front? If not, definitely not an X. The DDT op amp has a weird pinout and drives a J174 jfet. It is hard to buy, hope yours is not blown.
The ebay cs800x does say that on the front. In big bold letters.
Next thing after defeating triac protection, is build a light bulb box or use a element from a dead room heater to put in series with the AC power, so you can test for DC on the output without blowing the fuse.
Last edited:
Thanks. to clarify, front panel "CS 800" (no "X"); 3 rack space "wind tunnel" design cooling; it has the DDT speaker protection.
The plan for today is to repair the blown out trace on the power board and remove the bad SAC187. I will build the light box also. Should I test the output transistors since i have it apart? The only thing in the case ATM is the power supply.
The plan for today is to repair the blown out trace on the power board and remove the bad SAC187. I will build the light box also. Should I test the output transistors since i have it apart? The only thing in the case ATM is the power supply.
The light bulb box DC on output test is the first test of the power transistors. If they are not messed up, don't pull them. I make enough solder mistakes to leave things alone that work. My CS800s only had a blown input and power supply problems, so I haven't monkeyed with the output transistors yet. Yours are likely blown, but blowing fuses means you seriously need the light bulb box. Problem could be power supply caps or rectifier, instead. (change rsil electrolytic caps anyway for reliability at 30 years, but not until you identify what is wrong and fix that first. Later when working right you can change all the other electrolytic caps two at a time between tests).
Warning, the light bulb box would not provide enough power for my PV-1.3k to pass +-16v to the op amps, so I had to use a dead room heater element instead. Other problem with light bulb boxes, 100W tungsten filament bulbs are rare beasts these days in the USA. The halogen ones have a diode or something in them and don't work.
With DDT, the CS800x schematic on eserviceinfo.com should be good enough to work on it unless there traces melted off the driver board or vaporized parts you can't identify by color code. There was a 18 month period when Motorola/ON Semi made the MJ15024 and not the MJ15025, so Peavey may have stayed quasi comp while that was going on. MJ15024 would have been seriously more reliable at 81 v rails than MJ15003 or whatever previous version was. But fully complementary output could sound slightly better at low volumes than quasi-comp. These have HD rated at full power and as PA amps should mostly be used at 100 W/ch or above, but I listen to my CS800s at 1.5 W/ch today, and sound is superb.
Remove one leg of both sac187, you want the triacs disabled during testing. Or remove the triac gates. TO92 legs are easier to desolder.
Warning, the light bulb box would not provide enough power for my PV-1.3k to pass +-16v to the op amps, so I had to use a dead room heater element instead. Other problem with light bulb boxes, 100W tungsten filament bulbs are rare beasts these days in the USA. The halogen ones have a diode or something in them and don't work.
With DDT, the CS800x schematic on eserviceinfo.com should be good enough to work on it unless there traces melted off the driver board or vaporized parts you can't identify by color code. There was a 18 month period when Motorola/ON Semi made the MJ15024 and not the MJ15025, so Peavey may have stayed quasi comp while that was going on. MJ15024 would have been seriously more reliable at 81 v rails than MJ15003 or whatever previous version was. But fully complementary output could sound slightly better at low volumes than quasi-comp. These have HD rated at full power and as PA amps should mostly be used at 100 W/ch or above, but I listen to my CS800s at 1.5 W/ch today, and sound is superb.
Remove one leg of both sac187, you want the triacs disabled during testing. Or remove the triac gates. TO92 legs are easier to desolder.
Last edited:
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.
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.
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.
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.
Last edited:
pics
DSC02548_zpseo2w2it0.jpg Photo by bassfiveman | Photobucket
An externally hosted image should be here but it was not working when we last tested it.
DSC02548_zpseo2w2it0.jpg Photo by bassfiveman | Photobucket
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
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
Last edited:
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.
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.
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.
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
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
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.
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.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.