I think I'll stick with the Triac (Inidanajo's sub) for turn on, however, I'll put an NTC Thermistor, CL30, in series to reduce the surge. A small amount of series R in the AC line is a good thing since any voltage divided by zero ohms is an infinitely large current.
I decided to power up the amp sections independently using my dual bench power supply so I can dial in a current limit. Both came up fine drawing ~ 100ma, which sounds about right . The outputs are zero volts.
It turns out the other units' turn-on Triac is intact. I put that good one in the unit I'm working on for now. Once I have one good unit I'll add up what's required for parts to repair the other and decide whether it's worth the $ to fix it.
I decided to power up the amp sections independently using my dual bench power supply so I can dial in a current limit. Both came up fine drawing ~ 100ma, which sounds about right . The outputs are zero volts.
It turns out the other units' turn-on Triac is intact. I put that good one in the unit I'm working on for now. Once I have one good unit I'll add up what's required for parts to repair the other and decide whether it's worth the $ to fix it.
I am one who used to be a staunch believer in switching power supplies for their light weight and their impressive current handling at low voltages. However, after several decades, and after some experience using switching power supplies, I NO longer suggest swapping a linear transformer based power supply with a switching one.
The advantage of old-style linear power supplies, is they are extremely durable, which contrasts with the typical life span of switching power supplies.
The advantage of old-style linear power supplies, is they are extremely durable, which contrasts with the typical life span of switching power supplies.
Well I'm getting close. I have one working unit and a list of things to buy for the second. I've had my share of mishaps. I was scoping the circuit with the which hat clip removed from the probe and neglected to put on the GND insulator ring in its place. I sparked a couple components. I recovered easily but then -I dropped an alligator clip/wire on the circuit. The other end was attached to GND. In addition to a resistor this took out my beloved Wavetek 166 signal generator that was attached to the front end. Ouch. I've had to fix it before. I affectionately call it "Analog Nightmare". I have a handle on what's wrong. The few IC's it uses are getting hard to find though. I think I damaged a dual differential amp, (predecessor to the op-amp), CA3069. It also destroyed the power switch. I got lucky and had a replacement on hand for that by chance. I spent a good part of the day recovering. That unit is superbly packaged - very high build quality and a study in discrete analog - it uses a capacitance multiplier, ie gyrator circuit, to affect the frequency of the main oscillator.
I'm getting old, eyes not so good, my hands a little shaky and I'm loosing sensitivity in some finger tips hence I'm dropping things. I was initially creating more problems than I had originally. Ah well, what else am I gonna do during a pandemic.
I'm getting old, eyes not so good, my hands a little shaky and I'm loosing sensitivity in some finger tips hence I'm dropping things. I was initially creating more problems than I had originally. Ah well, what else am I gonna do during a pandemic.
Last edited:
Sorry about the dropped clip damage. My hands are still pretty steady age 70 but the vision is getting dodgy. 3 pairs of reading glasses at different magnification, and I'm wearing a LED light on my forehead now instead of trying to juggle a trouble-light with one hand while I work with the other and one foot.
I worry about hand foot neuropathy since I'm diabetic. Reason I ride a bike 20-70 miles a week: exercise controls sugar better than pills. Rode 10 miles yesterday & today at ~25 deg F, lots of layers on.
Not much good news on CA30xx IC's. I scored some CA3080 transconductance amps 10 years ago for my Peavey products, but the burglar carried them & everything else off to the copper scrapper 9/14. Be redesign time if I burn another CA30xx. Bad news, nothing is pin compatible. Good news, the CA3080 and CA3094 were the fastest amp IC's alive in 1992. LM4562 will leave them eating dust these days. Take a redesign though now to use LM4562 for DDT.
I have waveform generator envy, I'm still using a FM radio earphone jack. But don't have the shelf space for a scope & generator over the workbench, unless I move out of the comfy living room to the cold damp basement.
Next challenge, a CS800s from ebay due tomorrow USPS. Supposed to be working. Auction ran the price up from $170 initially to $194, but that is still not too bad for a 15 lb 800 W amp. Especially with $44 USPS from GA. I fixed the input board and switcher supply on the CS800s that Mr Coffman carried off in September. (He was in house when I got home, police carried him & his SUV off). Should be easier to repair CS800s this time if the switcher is not blown up yet. Just geriatric mains caps. The other one had a channel imbalance I hadn't fixed yet; maybe this one will be better. Until I get the cs800s and some decent SP2's, I'm listening to music on a monaural MMA-875t I got for $30 +40 freight. Works. Using a *****y organ speaker that was too home-built looking for Mr Coffman to carry off. *****y sounding speaker, too. Miss the SP2-XT's.
I worry about hand foot neuropathy since I'm diabetic. Reason I ride a bike 20-70 miles a week: exercise controls sugar better than pills. Rode 10 miles yesterday & today at ~25 deg F, lots of layers on.
Not much good news on CA30xx IC's. I scored some CA3080 transconductance amps 10 years ago for my Peavey products, but the burglar carried them & everything else off to the copper scrapper 9/14. Be redesign time if I burn another CA30xx. Bad news, nothing is pin compatible. Good news, the CA3080 and CA3094 were the fastest amp IC's alive in 1992. LM4562 will leave them eating dust these days. Take a redesign though now to use LM4562 for DDT.
I have waveform generator envy, I'm still using a FM radio earphone jack. But don't have the shelf space for a scope & generator over the workbench, unless I move out of the comfy living room to the cold damp basement.
Next challenge, a CS800s from ebay due tomorrow USPS. Supposed to be working. Auction ran the price up from $170 initially to $194, but that is still not too bad for a 15 lb 800 W amp. Especially with $44 USPS from GA. I fixed the input board and switcher supply on the CS800s that Mr Coffman carried off in September. (He was in house when I got home, police carried him & his SUV off). Should be easier to repair CS800s this time if the switcher is not blown up yet. Just geriatric mains caps. The other one had a channel imbalance I hadn't fixed yet; maybe this one will be better. Until I get the cs800s and some decent SP2's, I'm listening to music on a monaural MMA-875t I got for $30 +40 freight. Works. Using a *****y organ speaker that was too home-built looking for Mr Coffman to carry off. *****y sounding speaker, too. Miss the SP2-XT's.
Last edited:
50 a day here. More addictive than building amplifiers and speakers. They used to just call it “your metabolism slowing down as you get older”. The truth no one wants to hear is that the body was simply designed to whomp out 200 watts of average power for several hours a day. Kind of like the old 70 pound CS800 with the entire top cover made out of heat sink were.
The light ones are nice - to drive 2” compression drivers in a tri-amp.
“Waveform generator envy”? You do have a laptop or computer somewhere near the bench don’t you? Hell, for years I used a little home made PCB with an ICL 8038 chip on it. Powered off one of the home made bench top power supplies.
Got the Wavetek fixed...phew!
It's kinda weird what happened because I can't correlate the accident event, ie, dropping a lead on the board under test which destroyed a resistor feeding a 16V regulator on same board, with what happened with the signal generator that was attached to the input.
The generator's 0.5amp fuse blew. I put another fuse in and it blew too. I alternately actuated and de-actuated the power switch a few times. It's a latching type. Thereafter a fuse would survive but the power would not come on. I found the plastic switch plunger had broken. Perhaps it broke as a result of cycling it a few times but the switch actually worked if you could press the mechanism without the plunger. I replaced the switch and voila no more blown fuses and the power comes on. That's weird. The switch has no connections to GND nor is any of its leads even close to GND. I really don't know how it could short out the power and blow a fuse. Nonetheless I had power now and all supply rails were good.
But, the strangeness continues. There was still a problem. The square wave function no longer worked. Sign, triangle, and sawtooth were all fine.
This I eventually traced to a connector that passes the square wave signal from the main board to the trigger board. Simply unplugging it and plugging it back in corrected the problem.
Aha, tarnished contact!
I cleaned it up and it's been working fine ever since.....but....but...but what does that have to do with the accident?
Such is the tail of fixing electronic things. This is why I no longer say "it can't be that because...etc". I hear this often from so many repair techs who get stuck.
It's kinda weird what happened because I can't correlate the accident event, ie, dropping a lead on the board under test which destroyed a resistor feeding a 16V regulator on same board, with what happened with the signal generator that was attached to the input.
The generator's 0.5amp fuse blew. I put another fuse in and it blew too. I alternately actuated and de-actuated the power switch a few times. It's a latching type. Thereafter a fuse would survive but the power would not come on. I found the plastic switch plunger had broken. Perhaps it broke as a result of cycling it a few times but the switch actually worked if you could press the mechanism without the plunger. I replaced the switch and voila no more blown fuses and the power comes on. That's weird. The switch has no connections to GND nor is any of its leads even close to GND. I really don't know how it could short out the power and blow a fuse. Nonetheless I had power now and all supply rails were good.
But, the strangeness continues. There was still a problem. The square wave function no longer worked. Sign, triangle, and sawtooth were all fine.
This I eventually traced to a connector that passes the square wave signal from the main board to the trigger board. Simply unplugging it and plugging it back in corrected the problem.
Aha, tarnished contact!
I cleaned it up and it's been working fine ever since.....but....but...but what does that have to do with the accident?
Such is the tail of fixing electronic things. This is why I no longer say "it can't be that because...etc". I hear this often from so many repair techs who get stuck.
Definitely a black cat day on January 13. Friday the 13th on Wednesday, as Pogo the cartoon would say. No reason ground on output of generator should blow the power switch.
On the bright side, my ebay CS800s arrived at 10 amp. It worked! at 1 watt, but that is fine. Sound on both sides. Now to decide what to do about speakers. Some 1st generation SP2 showed up 40 miles from here. Trying to decide if the round edged horn might sound as good as the rectangular horns in SP2-xt. Is it worth $400 the pair + $80 to rent a car? Probably post something on multi-way speakers thread. These SP2 are only 150 W rated, so not even the crossover is up to the SP2-XT.
@ 1730 UPS delivered a M-2600 amp I bought 12/24. $105 + $43 freight. Took the vendor 15 days to ship. 90 W/ch. No fan! Good for house use. Can't check yet, no 1/4 phone plugs and none for sale in county I've found so far. Plenty 5 days away Newark in NC or Digikey in MN. Not paying $22 a guitar cable @ some music shop.
On the bright side, my ebay CS800s arrived at 10 amp. It worked! at 1 watt, but that is fine. Sound on both sides. Now to decide what to do about speakers. Some 1st generation SP2 showed up 40 miles from here. Trying to decide if the round edged horn might sound as good as the rectangular horns in SP2-xt. Is it worth $400 the pair + $80 to rent a car? Probably post something on multi-way speakers thread. These SP2 are only 150 W rated, so not even the crossover is up to the SP2-XT.
@ 1730 UPS delivered a M-2600 amp I bought 12/24. $105 + $43 freight. Took the vendor 15 days to ship. 90 W/ch. No fan! Good for house use. Can't check yet, no 1/4 phone plugs and none for sale in county I've found so far. Plenty 5 days away Newark in NC or Digikey in MN. Not paying $22 a guitar cable @ some music shop.
Last edited:
IndianaJo, your input power triac sub worked perfectly both electrically and mechanically. I finally get why this would be used. I had forgot that triacs turn on at the zero crossing therefore it's not random in the cycle when the AC line is connected to the transformer. At the zero crossing the potential is zero - howboutdat! I've noticed I no longer get a quick dimming of my lab lights now that it is in the circuit. I'm almost there with the second unit from which I robbed parts. I just need the speaker protector triac and four output transistors. I was able to make successful transistor subs for the drivers that were blown. I really don't think an NTC inrush limiter is needed now, perhaps a little risky anyway.
Last edited:
Congratulations! I didn't think a CL30 was going to be big enough to sustain stage performance wattage, anyway. I installed a CL101.
These dinosaurs live on 50 years if the transistor sockets & ecaps, possibly pots & fan, are replaced. Plus clean all the dirt off the heat sink. I tie-wrap coated filter material over the fan grills when I repair them.
I'm waiting for 1/4 phone plugs + ecaps from S. Carolina. Found a 1/4 phone plug 6' guitar cable Friday at Ben's Bargain Center, $27, 40% off from $37. No thanks. Dropped the newark order at 1330. Ben's did have a pocket radio to replace the 1988 one with bad ecaps and a bent stereo phone plug for $7. Nice thing about pocket radios, they don't hum.
I like MJE15028/29 for low voltage (+-40) drivers and MJE15031/32 for high voltage (+-85) predrivers. Peavey recommended the MJE15031/32 to replace the ****ese 2sc 2sa drivers they originally installed in the PV-1.3k. On parts are made in the same country, but somehow On QA guys don't take bribes to look the other way.
These dinosaurs live on 50 years if the transistor sockets & ecaps, possibly pots & fan, are replaced. Plus clean all the dirt off the heat sink. I tie-wrap coated filter material over the fan grills when I repair them.
I'm waiting for 1/4 phone plugs + ecaps from S. Carolina. Found a 1/4 phone plug 6' guitar cable Friday at Ben's Bargain Center, $27, 40% off from $37. No thanks. Dropped the newark order at 1330. Ben's did have a pocket radio to replace the 1988 one with bad ecaps and a bent stereo phone plug for $7. Nice thing about pocket radios, they don't hum.
I like MJE15028/29 for low voltage (+-40) drivers and MJE15031/32 for high voltage (+-85) predrivers. Peavey recommended the MJE15031/32 to replace the ****ese 2sc 2sa drivers they originally installed in the PV-1.3k. On parts are made in the same country, but somehow On QA guys don't take bribes to look the other way.
Last edited:
The Keystone transistor socket worked great for me. I stole just the plastic insulator part by knocking off two plastic nubs and used it on the existing fiberglass socket laminate that include the pins - easy.
I'm thinking the following triac is a decent sub for the speaker protector - BTA16-600BWRG.
So this second unit is interesting in that it is equipped with the crossover modules. I believe these two units were used in a stage bi-amp system.
I may try to equip speakons.
I'm thinking the following triac is a decent sub for the speaker protector - BTA16-600BWRG.
So this second unit is interesting in that it is equipped with the crossover modules. I believe these two units were used in a stage bi-amp system.
I may try to equip speakons.
I used BTB16-600 from ST, because it was in stock the day I bought. 16 A triac 600 v in TO220 package. Reason for high voltage, refrigrator shut off transients can go to 1300 v. I used to specify test for new refrigerators.
You want to sell the crossovers? My SP2-XT were stolen and a 4 mh 15 ga jansen coil is about $40 + freight. I have the RX22 horn tops, $136 for 2 from ebay including freight. They work. I'm thinking of buying two eminence delta 15a drivers for $150 ea and some plywood delivered by Lowes since I don't have a car to go driving around when SP2g show up on ebay. There are round edge horn SP2 only 40 miles away, but they cross over @ 800 hz instead of 1200 & only have a 150 W rating, so not up to SP2-XT specs (300 W). Not worth $100 car rental to drag them home with that much wrong with them. Besides, it is snowing every day now.
Even millihenry and microfarad specs on the crossovers you have would be useful, if you have a meter that measures those. I should have measured the SP2-XT when I had them, but didn't like taking apart working units. Of course, electrolytic crossover caps aren't worth much @ 30 years. Plastic film ones are!
Last edited:
Hey Indianajo, Me thinks I shouldn't split up that system because it might be attractive to some indoor (stationary) venues that want to bi-amp a couple of speakers (SP2 etc) for example without working too hard.
BTW the crossovers are available on Ebay for anywhere form $10 to $25.00.
The parts for the second unit should arrive Friday. I've spent a total of about $40.00 to revive two CS800 Peavey amps - not too bad. Hope somebody wants them and is ok with the shipping. If not I know a couple of VT music venues who might be interested if I deliver.
I have to say the CS800 is a great amp - the modularity makes it easy to trouble shoot and the performance rivals modern class D amps if not outperforms.
BTW the crossovers are available on Ebay for anywhere form $10 to $25.00.
The parts for the second unit should arrive Friday. I've spent a total of about $40.00 to revive two CS800 Peavey amps - not too bad. Hope somebody wants them and is ok with the shipping. If not I know a couple of VT music venues who might be interested if I deliver.
I have to say the CS800 is a great amp - the modularity makes it easy to trouble shoot and the performance rivals modern class D amps if not outperforms.
Congratulations!
Now that I have 1/4" phone plugs, my ebay M-2600 amp works! paid $105 for it, plus $42 freight. I don't need 400 w/ch in the living room, just 90, and there is no fan to make noise, just two 6"x7" heat sinks.
Repairing a MMA-81502 that started humming, and it is not the main caps. Last repairman in didn't solder in the 7915 & LM317 regulators. Just pushed them in. Worked most of the time. Will add fins to the flat heat flange since regulator required replacement before.This is monaural for my shober organ, to mix voice mike in the speaker as it has phantom power.
Now that I have 1/4" phone plugs, my ebay M-2600 amp works! paid $105 for it, plus $42 freight. I don't need 400 w/ch in the living room, just 90, and there is no fan to make noise, just two 6"x7" heat sinks.
Repairing a MMA-81502 that started humming, and it is not the main caps. Last repairman in didn't solder in the 7915 & LM317 regulators. Just pushed them in. Worked most of the time. Will add fins to the flat heat flange since regulator required replacement before.This is monaural for my shober organ, to mix voice mike in the speaker as it has phantom power.
Last edited:
Congrats on that M-2600. BTW the crossovers in the CS800 are active. I had just assumed they weren't and spent a half hour scratching my head until I realized they need power, duh. Both work well too.
Speaking of fans, I have a small fan in my Tektronix 2232 oscilloscope that's making noise. I've opened it up a couple times with the intention of replacing it and both times I have chickened out. That thing is a packaging miracle/(nightmare?). There's at least an hour of disassembly to get to it and 50 different size screws.
Speaking of fans, I have a small fan in my Tektronix 2232 oscilloscope that's making noise. I've opened it up a couple times with the intention of replacing it and both times I have chickened out. That thing is a packaging miracle/(nightmare?). There's at least an hour of disassembly to get to it and 50 different size screws.
I bought a B&K 2120 scope used in 2014 for $40, and it worked for half an hour. Then the sweep froze. Taking the cover off, all the controls & pcbs had been glued in place to keep the students of previous owner, a TV repair school, out of it.
5 years later I took a wood chisel to the glue in January, a month with no yardwork or house maintenance. Coupla afternoons of scraping, the PCB came out, and a dozen or 20 capacitors later, the sweep worked. At least I could listen to the radio on SP2 speakers while I was doing that dog work. I hate buying new stuff, it is all made in a country that got me drafted to serve in a war that we lost. Lost the battle on DVM last week, the burglar stole all the working ones. $15 to the perpetrator. The scope was missing the back cover, burglar didn't steal it.
5 years later I took a wood chisel to the glue in January, a month with no yardwork or house maintenance. Coupla afternoons of scraping, the PCB came out, and a dozen or 20 capacitors later, the sweep worked. At least I could listen to the radio on SP2 speakers while I was doing that dog work. I hate buying new stuff, it is all made in a country that got me drafted to serve in a war that we lost. Lost the battle on DVM last week, the burglar stole all the working ones. $15 to the perpetrator. The scope was missing the back cover, burglar didn't steal it.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.