I cannot turn this amp on for more than a few seconds as the main DC voltages rise to more than 110volts and the amp hums/buzzes very loudly.I have checked all semiconductors and passives on the regulator PCB with a multimeter (in-circuit). I also checked the 35A TRIAC (and the TO-92 triac) ,and replaced the op-amp. I looked at the drive signal to the TO-92 triac gate on a scope (for the few seconds I can power it) and there was no signal at all noticeable on the scope.
Is the any way to power this long enough to trouble shoot the regulator ckt without doing severe damage ?
Is the any way to power this long enough to trouble shoot the regulator ckt without doing severe damage ?
Hi.
I have some 30 carver amps for live touring system. I also service many of them and have all service manuals for models which I have.....
There was only a few different psu basic circuits so I will glad if I can help you....
There is possible to connect amp on variac and gradually increase voltage. At some 30 volts ac the amp should work and you will be maybe able to locate problem. If you already checked triac than can be tricky to repair it......I can share some experience.
At PM 1.5 I have found once bad trimmer pot which is used to adjust psu voltage.
Because you mentioned small to92 triac I think that this is the same psu which was developed for PT1800/2400 amps.....At PT2400 once I discovered this scenario...
Because one of the big smoothing caps die amp try to charge it but it never reached wanted voltage. So all other voltages were way too high but amp try to charge that cap. The result was several destroyed caps and burnt resistors. My advice. If you can't get some variac connect amp to mains via 100W bulb and measure voltages on the smoothing caps. If you find lower voltage on some of smoothing caps that one is bad. Because there you have triple psu you must check all 3 voltages. For such amp is something like+-35,+-70, +-120,+-12 volts normal. That last +-12v is used to power small signal circuits..... If you want I can check values in service manual, of course if we can determine which is the closest to your amp....
There is also good idea to chech all bridge rectifiers and diodes.....
Ah and now I remember that at that PT2400 was also a burnt 1N4148 diode.....I can also try to remember which.....because there is a lot of them....
So try confirm that tfm psu is similar to that one from PT2400 amps and we will try to figure out something.
Best regards
I have some 30 carver amps for live touring system. I also service many of them and have all service manuals for models which I have.....
There was only a few different psu basic circuits so I will glad if I can help you....
There is possible to connect amp on variac and gradually increase voltage. At some 30 volts ac the amp should work and you will be maybe able to locate problem. If you already checked triac than can be tricky to repair it......I can share some experience.
At PM 1.5 I have found once bad trimmer pot which is used to adjust psu voltage.
Because you mentioned small to92 triac I think that this is the same psu which was developed for PT1800/2400 amps.....At PT2400 once I discovered this scenario...
Because one of the big smoothing caps die amp try to charge it but it never reached wanted voltage. So all other voltages were way too high but amp try to charge that cap. The result was several destroyed caps and burnt resistors. My advice. If you can't get some variac connect amp to mains via 100W bulb and measure voltages on the smoothing caps. If you find lower voltage on some of smoothing caps that one is bad. Because there you have triple psu you must check all 3 voltages. For such amp is something like+-35,+-70, +-120,+-12 volts normal. That last +-12v is used to power small signal circuits..... If you want I can check values in service manual, of course if we can determine which is the closest to your amp....
There is also good idea to chech all bridge rectifiers and diodes.....
Ah and now I remember that at that PT2400 was also a burnt 1N4148 diode.....I can also try to remember which.....because there is a lot of them....
So try confirm that tfm psu is similar to that one from PT2400 amps and we will try to figure out something.
Best regards
I checked. It is little different but similar.....
http://thecarversite.com/manuals/files-manuals/Carver TFM-55 service manual.pdf
http://thecarversite.com/manuals/files-manuals/Carver TFM-55 service manual.pdf
Hello Tajzmaj
Thanks for the help.I haven't yet had time to try the variac supply,do you know how much current it should draw when running on the variac at ~ 30vac ? I have checked the bridge rectifiers for all three supplies with no problems. The 96v supply is not being restricted as it immediatly goes to > +/- 110v in 2-3 seconds but I haven't yet checked the other two - thanks for that suggestion.Is the 96v supply the one used to monitor the transformer (mag coil's) output to regulate the triacs "on time" thru the op-amp & optocoupler? Also shouldn't I be seeing some evidence of the triac's control signal at the opamp's or optocoupler's output - even though it's only powered on for a couple seconds?.
I'll let you know if I get it powered up on the variac.
Thanks again,
Best Regards
Thanks for the help.I haven't yet had time to try the variac supply,do you know how much current it should draw when running on the variac at ~ 30vac ? I have checked the bridge rectifiers for all three supplies with no problems. The 96v supply is not being restricted as it immediatly goes to > +/- 110v in 2-3 seconds but I haven't yet checked the other two - thanks for that suggestion.Is the 96v supply the one used to monitor the transformer (mag coil's) output to regulate the triacs "on time" thru the op-amp & optocoupler? Also shouldn't I be seeing some evidence of the triac's control signal at the opamp's or optocoupler's output - even though it's only powered on for a couple seconds?.
I'll let you know if I get it powered up on the variac.
Thanks again,
Best Regards
Hi
When you connect such amp to variac you must short triac first. Otherwise the amp will fire up but at voltage high enough and you won't be able to measure anything.......Short A1 and A2 of the triac and than slowly open variac. And measure voltage on big smoothing caps. I'm Not sure but at some 50vac will the transformer goes to saturation and will draw high current. You will hear buzing....and you won't get full voltage on psu at that moment because this transformer can't be in full conductive cycle at voltages high enough to get 96V at psu......
When you connect such amp to variac you must short triac first. Otherwise the amp will fire up but at voltage high enough and you won't be able to measure anything.......Short A1 and A2 of the triac and than slowly open variac. And measure voltage on big smoothing caps. I'm Not sure but at some 50vac will the transformer goes to saturation and will draw high current. You will hear buzing....and you won't get full voltage on psu at that moment because this transformer can't be in full conductive cycle at voltages high enough to get 96V at psu......
You can also connect amp on variac but put some bulb (40-60W) in series, and try to reach 96V......or at least some higher voltage. But it looks like that it is still something wrong with regulation of primary...There can be defective opto coupler or some of transistors at steering circuit...don't be afraid of this amp....There is nothing very strange and special inside 
Which oc is used? If I'm correct CYN17-2
Which oc is used? If I'm correct CYN17-2You are correct the oc is CYN17-2,I've checked the diode and transistor in the oc pkg w/multimeter (in-circuit) and they seem ok. I've also checked the 4 steering ckt transistors and they test ok. Is it important to achieve normal operating voltages on DC supplies to troubleshoot the primary regulator ckt? I guess I am a bit afraid of driving the transformer primary too hard and damaging it.
If there is a primary defect than it is not important. But if there is something wrong with secondary circuit of psu than maybe it is.....for an example. If there you have bad smoothing cap it will show up when you put some load on it....and current consumption will increase with voltage....Hey btw does amp work now. I mean with this lower voltage....
I still suggest that you put a light bulb in series with amp and than try to open variac slowly. you will see when the amp starts to draw some higher current. The bulb will glow up and protect transformer.....
I still suggest that you put a light bulb in series with amp and than try to open variac slowly. you will see when the amp starts to draw some higher current. The bulb will glow up and protect transformer.....
I checked service manual for your amp....It only use +-30 and +-12 voltages for reference.....so it will be great if you manage to confirm at least those voltages. It can be defective +-12V regulator.......
There are some diodes around U2. Those 1N4148 are possible and 3 zeners also....and 1N4001 around oc1 are worth to check too. If there is nothing mechanically wrong ( bad solders....). What about the trimpot for adjusting voltage. At PM1200 I replace it once with brand new piher unit and it was defective too......
It is hard to say.......and it will take some time to find what is wrong. Work systematic.
And first of all try to confirm that all voltages are present and more or less symmetric.
Best regards
Taj
There are some diodes around U2. Those 1N4148 are possible and 3 zeners also....and 1N4001 around oc1 are worth to check too. If there is nothing mechanically wrong ( bad solders....). What about the trimpot for adjusting voltage. At PM1200 I replace it once with brand new piher unit and it was defective too......
It is hard to say.......and it will take some time to find what is wrong. Work systematic.
And first of all try to confirm that all voltages are present and more or less symmetric.
Best regards
Taj
Hi Taj
Yes, the amp starts to work (speaker protect relays click on) at +/- 55vdc (96v ps) and it plays good sine waves on both sides - open ckt, I haven't put a load on the outputs. At 55v the +/- 12v ps = +/- 10v & the +/- 30v ps = +/- 15v ....so I see what you mean the 30v is determining U2's output to the oc so it needs to get up to +/- 30v before the op-amp's output is functional. I'll put the 60w bulb in series to try to achieve 30v. I checked all the diodes/zeners when I first started - all ok. The pot's resistance and variability seems fine and the solder joints look good as well.
Thanks again and Best Regards
Nites
Yes, the amp starts to work (speaker protect relays click on) at +/- 55vdc (96v ps) and it plays good sine waves on both sides - open ckt, I haven't put a load on the outputs. At 55v the +/- 12v ps = +/- 10v & the +/- 30v ps = +/- 15v ....so I see what you mean the 30v is determining U2's output to the oc so it needs to get up to +/- 30v before the op-amp's output is functional. I'll put the 60w bulb in series to try to achieve 30v. I checked all the diodes/zeners when I first started - all ok. The pot's resistance and variability seems fine and the solder joints look good as well.
Thanks again and Best Regards
Nites
I'm not sure for tfm amp but for an example PM1200 has idle power consumption 120W which is around 1A at 110vac mains voltage.......but you should check at service manual......
Anyway it seems high to me too but it is maybe different with proper primary regulation.
So it seems that is something wrong with this ,,dimmer,, circuit. Maybe is worth to replace op amp......I think there is something like 4558 .....which is cheap. Hey btw what happened ? Why amp stopped to work?
Anyway it seems high to me too but it is maybe different with proper primary regulation.
So it seems that is something wrong with this ,,dimmer,, circuit. Maybe is worth to replace op amp......I think there is something like 4558 .....which is cheap. Hey btw what happened ? Why amp stopped to work?
I have already replaced the op-amp and I've checked every component on the regulator pcb with a multimeter - actives and passives. With my Fluke meter on "diode test" I measure ~ 50 ohms gate-T1 fwd & reverse on 35A triac and open ckt on G-T2,T1-T2. Since I can't achieve +/-30v on the monitored supply (except for 2-3 seconds before 96v supply goes > 110vdc) I can't see away to do any testing at normal (valid) operating psu voltages. I think next I'll replace the oc and the T0-92 triac - all other parts can be fairly reliably tested w/fluke.
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