I'm trying to repair this 1998 Peavey CS800s that started tripping the breaker after I stored it for a month or two, in 2013. I bought $1000 worth of gear off a defunct bar band, the SP2-XT speakers are stellar, amp sounded good but he was using the out jacks for the feed in, 1/8 watt resistors were blown on input card. Unity 12 mixer seems to be okay, 4 other devices with bad hum, speaker stands, snake, wedge monitor 15"+horn speaker. Rack case.
CS800s is a switcher supply so assumed main e-caps were bad, bingo. One 2200 uf 200v had been replaced with a 1981 CDE part, reading about 1900 uf .5 ohm ESR. Replaced both mains caps with 2013 Panasonic 3000 hour caps. 1000 uf Rail caps are reading 950 uf .08 ESR, good cause I didn't buy any.
Now supply won't power up, the .160 A pigtail fuse is blown in relay power supply circuit. I don't have any fuse lower than 400 ma. My computer is hacked I don't want to order anything now. I did have a new 1000 uf 50 v pre-regulator cap, the old one was losing 3 mv per meter scan, not awful but a little leaky. I don't have the fuse.
I do have some blown PC=ATX switcher supplies with rice grain surface mount resistors, maybe 1/10 or 1/8 watt. I have 22 and 10 ohms, about 2 mm long x 1.2 mm wide. These are about 1/8 or 1/10 watt maybe? they are not for sale on newark to I don't know what wattage but it can't be much.
The load on transformer is 1000 uf 35 v cap, then 7812 regulator, then 220 uf 50 v cap, then relay coil reading 220 ohm. So steady load ,054 a, round up to .06 A.
So .(06 A)^2 x 22 ohm= .079 watts won't blow steady state.
sqrt(P/R)=I sqrt(.125W/22ohm)=.075 so resistor is nearing the current limit at 75 ma.
So what do you think? Stupid? not as stupid as putting a 1981 mains capacitor on a 1998 board and initialling it, perhaps.
CS800s is a switcher supply so assumed main e-caps were bad, bingo. One 2200 uf 200v had been replaced with a 1981 CDE part, reading about 1900 uf .5 ohm ESR. Replaced both mains caps with 2013 Panasonic 3000 hour caps. 1000 uf Rail caps are reading 950 uf .08 ESR, good cause I didn't buy any.
Now supply won't power up, the .160 A pigtail fuse is blown in relay power supply circuit. I don't have any fuse lower than 400 ma. My computer is hacked I don't want to order anything now. I did have a new 1000 uf 50 v pre-regulator cap, the old one was losing 3 mv per meter scan, not awful but a little leaky. I don't have the fuse.
I do have some blown PC=ATX switcher supplies with rice grain surface mount resistors, maybe 1/10 or 1/8 watt. I have 22 and 10 ohms, about 2 mm long x 1.2 mm wide. These are about 1/8 or 1/10 watt maybe? they are not for sale on newark to I don't know what wattage but it can't be much.
The load on transformer is 1000 uf 35 v cap, then 7812 regulator, then 220 uf 50 v cap, then relay coil reading 220 ohm. So steady load ,054 a, round up to .06 A.
So .(06 A)^2 x 22 ohm= .079 watts won't blow steady state.
sqrt(P/R)=I sqrt(.125W/22ohm)=.075 so resistor is nearing the current limit at 75 ma.
So what do you think? Stupid? not as stupid as putting a 1981 mains capacitor on a 1998 board and initialling it, perhaps.
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CS800s
If you can't get the switching supply to work, you can always remove it and replace it with a conventional linear supply.
If you can't get the switching supply to work, you can always remove it and replace it with a conventional linear supply.
I don't have any 80-0-80 v 30 A transformers that would fit in this space, either. Takes two since Peavey uses flying ground.
**** fuse doesn't look blown, wire is solid in the glass, just reads ---- ohms. I suspect oxidation due to age under the stamped on pigtail wire caps.
The fet gate drive IC is also a load on the 7812, so I can't calculate the dynamic current. I guess I'll put this away until next year after I figure out now to replace this computer. SB.160 Fuses are $1.59 ea at newark +$8 freight but I need a computer to order them that doesn't transmit my debit card data to electronics-tutorials.ws the perp in this hack of ubuntu op sys.
**** fuse doesn't look blown, wire is solid in the glass, just reads ---- ohms. I suspect oxidation due to age under the stamped on pigtail wire caps.
The fet gate drive IC is also a load on the 7812, so I can't calculate the dynamic current. I guess I'll put this away until next year after I figure out now to replace this computer. SB.160 Fuses are $1.59 ea at newark +$8 freight but I need a computer to order them that doesn't transmit my debit card data to electronics-tutorials.ws the perp in this hack of ubuntu op sys.
I came across this in another forum. Apparently, Peavey recommends a 250mA replacement for the 160mA fuse.
I had a look at the cs800s schematics and as I thought, it's the same as the other models. The only difference is in the switching supply.
The supply rails are +/- 75Vdc. A 55-0-55V transformer (800VA) should do for both channels. House that in a separate box externally and run a cord to the cs800s. There is enough space within for a bridge rectifier and filter caps.
It's a bit of work but can be done.
I had a look at the cs800s schematics and as I thought, it's the same as the other models. The only difference is in the switching supply.
The supply rails are +/- 75Vdc. A 55-0-55V transformer (800VA) should do for both channels. House that in a separate box externally and run a cord to the cs800s. There is enough space within for a bridge rectifier and filter caps.
It's a bit of work but can be done.
Okay, thanks for looking this up, I thought 160 ma was a bit precious. If this circuit was just a relay coil driver I'd risk the 22 ohm 1/8 watt resistor for the open fuse, but gate of the switcher fets can blow and allow your 200 v DC to rampage through your driver transformer with 2200 uf behind it. That might blow up some transformers.
I fixed one switcher supply already, out of an Allen organ. That one the mains 200 v caps went leaky and had blown a NTC surge resistor between the main AC and the cap. Switcher supplies must be hard on mains AC capacitors. Took that one 20 years to blow up though, was a 1985 build.
I guess you're right about a 55 transformer producing 75v rails. But I don't have two of those either, then there is 24 v and I don't know what else.
The new solder in fuses for sale don't have that stupid stamped on cap that is probably is stopping current. They are not glass though so you can't see they are blown.
I've have an organist friend coming over Sat night between services to listen to records, my ST120 is making a bad solder joint noise about 1 day out of 20. Probably will happen then. I'll just try to finish my LM1875 IC amp before then, I have all the parts for that.
Interesting music-electronics forum covers a PA amp. they wouldn't let me sign up because I don't know anything about guitar amps.
I fixed one switcher supply already, out of an Allen organ. That one the mains 200 v caps went leaky and had blown a NTC surge resistor between the main AC and the cap. Switcher supplies must be hard on mains AC capacitors. Took that one 20 years to blow up though, was a 1985 build.
I guess you're right about a 55 transformer producing 75v rails. But I don't have two of those either, then there is 24 v and I don't know what else.
The new solder in fuses for sale don't have that stupid stamped on cap that is probably is stopping current. They are not glass though so you can't see they are blown.
I've have an organist friend coming over Sat night between services to listen to records, my ST120 is making a bad solder joint noise about 1 day out of 20. Probably will happen then. I'll just try to finish my LM1875 IC amp before then, I have all the parts for that.
Interesting music-electronics forum covers a PA amp. they wouldn't let me sign up because I don't know anything about guitar amps.
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If nothing else, one could pop the SMPS out and send it to Peavey for repair, they have all th stuff, and the know-how, and they charge reasonable rates.
According to the schematic. the fuse is for a simple 7812 voltage regulator. The 12v output is to switch on the mains relay.
Second function is to power the switching drivers SG3644.
My understanding of mosfets is the gate is isolated from the Darin and Source. Should it fail, the gate should not see whatever is on the drain. If so, the switching transformers should be fine.
BTW, the smallest fuses I have are 0.65A glass fuses (slo-blo type). If it helps, I can send you a couple.
Thanks, I've got a couple of 0.4 A fuses spare for a meter.
When Fet's blow all terminals can short together. I've enough examples of that in PCAT ATX supplies, blown.
The ST120 is behaving today, dead silent without source playing, maybe it will sound good Christmas Eve. Merry Christmas
When Fet's blow all terminals can short together. I've enough examples of that in PCAT ATX supplies, blown.
The ST120 is behaving today, dead silent without source playing, maybe it will sound good Christmas Eve. Merry Christmas
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