dear people.
first of all I ask sorry for my English...
I hope someone help me, I read along this trehad, but I not found what solve ( or try to do ...) my problem.
I buyed for some buck the 1.5t.
Is really damaged, but whit a lot of patient and much more time, time after time I soved the problem the are front to me.
Started whit the ampli board now I'm stocked whit the regulator board.
I',m not have the original transformer but a couple of toroidal (from the beginning are inside and seems installed from a qualified person).
BDW...
I discoverd the Triac and the oc1 fused.
the diac are ok, the diode are ok, the resistor ok.
Changed triac and oc1,
but I have this problem : i read that the diac have to fire at 40 volts, and so the triac have to open from that voltage, but this not happen.
Infact , using a variac, at 25 volts the diac fires, and the same do the triac, and the trnasformer start to work.
And, also, more volts give to the ampli, more volts going to the trnasofrmer, seems the regulator no regulator nothing 😉
Do you have idea what is the firing voltage at the triac ?
and (in the manual are not present) what is the exact model of the oc1 ?
tks and regards from Italy!-
Hi guys, sorry for coughing up such an old thread. I am also an amptech from the Netherlands and wonder if speakertech has been successful in repairing the PM1.2. If not, it is probably sold and now in my workshop. Complaint: broken fuse and loud fan. The fan isn't an issue, but powering this thing is definitely a pain. The solution is simple if you take a closer look at the matter. The transformer is simply nothing more than a transformer with a lower primary voltage than usual, depending on the feedback. The triac ensures that the 230V~ is reduced to an acceptable current. There was an interruption in the feedback, so that the transformer had to deal with the full load. I tackled this by using a series lamp which leaves the fuse intact. Then it's a matter of measuring. It turned out that the wiring was inserted through a hole in the board, folded over and soldered into the PCB. This gives good strain relief but puts a lot of stress on the weld. This weld was therefore cracked. The optocoupler had also reached its maximum flight hours, so also replaced it just to be sure. Problem solved.
Hi cluseau,
These are special power supplies. I'm glad you got it working. There is a proceedure for soft starting these amps on the bench, and using a series lamp is not it. I guess it worked for you though.
It isn't simply a transformer with too few a turns ratio for full ine voltage, it is designed to deal with the chopped waveform from the triac. The filter capacotors also have to deal with this waveform. The PM series do use a fan, don't replace it with a kit that uses a sensor, just put the same type of fan in. Often if you lubricate the bearings the fan will be okay unless it has run for a long time dry.
The internal communtating power supply is set for bas or full range music. If you hit them with sine waves at higher frequencies, or high power mid or high frequency use these commutators will "lock up" which will overheat the amplifier until the signal is removed or lowered in level.
Yes, like any switch mode power supply, if the AC line voltage falls they will draw higher current to maintain the internal supply voltages. They are designed to be used with solid AC supplies. Any other high power amplifier will drop internal supplies and deliver less power and possilbly performance. Anyway, a high tech amplifier designed to perform well under reasonable conditions. The power supply itself incorporates both feedback and also great fault protection.
I was Canadian factory warranty for Carver and understand them very, very well.
-Chris
These are special power supplies. I'm glad you got it working. There is a proceedure for soft starting these amps on the bench, and using a series lamp is not it. I guess it worked for you though.
It isn't simply a transformer with too few a turns ratio for full ine voltage, it is designed to deal with the chopped waveform from the triac. The filter capacotors also have to deal with this waveform. The PM series do use a fan, don't replace it with a kit that uses a sensor, just put the same type of fan in. Often if you lubricate the bearings the fan will be okay unless it has run for a long time dry.
The internal communtating power supply is set for bas or full range music. If you hit them with sine waves at higher frequencies, or high power mid or high frequency use these commutators will "lock up" which will overheat the amplifier until the signal is removed or lowered in level.
Yes, like any switch mode power supply, if the AC line voltage falls they will draw higher current to maintain the internal supply voltages. They are designed to be used with solid AC supplies. Any other high power amplifier will drop internal supplies and deliver less power and possilbly performance. Anyway, a high tech amplifier designed to perform well under reasonable conditions. The power supply itself incorporates both feedback and also great fault protection.
I was Canadian factory warranty for Carver and understand them very, very well.
-Chris
Thanks for your feedback Chris. I am aware that a lamp is not the right way but my variac has died in action 🙄. The lamp then gave me some protection to make short-term measurements. In my case, only the feedback was intermittent. The reason I want to post this here is that several amps can have this problem. The wire is in a very tight bend intended for strain relief but over time the wire wants to stretch which puts force on the weld. Kind of common error.
I assume that the transformer (inductive load) in cooperation with the capacitors form a resonator to handle the triac circuit. Someone had been messing around there too. C4 was made of two piggybacked 100nF caps. The original value should be 470nF.
The fan was almost stuck. Lubricating the bearings helped a bit but was unreliable. An 80x80 fan fits exactly and is much quieter. Running on 15V= it blows frienly but when the thermoswitch switches on, it's a hurricane.
Nice design but definitely important to read the description, fortunately I have the manual.
regards
Frans
I assume that the transformer (inductive load) in cooperation with the capacitors form a resonator to handle the triac circuit. Someone had been messing around there too. C4 was made of two piggybacked 100nF caps. The original value should be 470nF.
The fan was almost stuck. Lubricating the bearings helped a bit but was unreliable. An 80x80 fan fits exactly and is much quieter. Running on 15V= it blows frienly but when the thermoswitch switches on, it's a hurricane.
Nice design but definitely important to read the description, fortunately I have the manual.
regards
Frans
Hi Frans,
Sorry to hear you lost your variac. It is one of the most essential pieces of equipment for working on amplifiers (and other things).
I haven't had any problems with the connections you are seeing. C4 just goes across the line to reduce spikes, the voltage rating would be higher for your market of course.
For various Carver amplifiers I use the variac, and different DC power supplies depending on the model and problem area. The biggest problem with forums and that darned "light bulb" is that people use them without understanding the possible effects on the circuit they are powering up. If you have a lot of experience it can be an expedient, but I have tried and no longer use a light bulb. I need to have a defined input voltage and read the current. Otherwise it is easy to misdiagnose a problem. Certainly I can't have the input voltage varying as I troubleshoot an issue!
Your fan solution sounds good. That's something I would do, I found some fan motors and always prefer to restore equipment to original configuration unless there is a good reason to change things up. Sounds like that fan was run way past the time it needed service. Why don't people fix things when they need it? Equipment is always run until it no longer can be used, then they are upset it costs more.
The manual is actually pretty good at explaining how it works. We still had to close warranty stations because they either can't read or refused to understand what they were fixing. That was the biggest issue, most techs did not understand how these worked, but dove right in anyway. These days the situation is worse as you can see. There was a very good reason Carver restricted service on these and did not release service information. Normally I have a problem with that, but sometimes with truly advanced ideas and design they are forced to do this. I can't tell you how many mag coils we sold (no returns) after warning the buyer that this part was not the problem. Then getting complaints that the new part was defective!
These days I am so tired of what hacks do to equipment! I thought it was as bad as it could get years ago, but the situation continues to deteriorate! I'm so glad I'll retire in a couple years I think.
-Chris
Sorry to hear you lost your variac. It is one of the most essential pieces of equipment for working on amplifiers (and other things).
I haven't had any problems with the connections you are seeing. C4 just goes across the line to reduce spikes, the voltage rating would be higher for your market of course.
For various Carver amplifiers I use the variac, and different DC power supplies depending on the model and problem area. The biggest problem with forums and that darned "light bulb" is that people use them without understanding the possible effects on the circuit they are powering up. If you have a lot of experience it can be an expedient, but I have tried and no longer use a light bulb. I need to have a defined input voltage and read the current. Otherwise it is easy to misdiagnose a problem. Certainly I can't have the input voltage varying as I troubleshoot an issue!
Your fan solution sounds good. That's something I would do, I found some fan motors and always prefer to restore equipment to original configuration unless there is a good reason to change things up. Sounds like that fan was run way past the time it needed service. Why don't people fix things when they need it? Equipment is always run until it no longer can be used, then they are upset it costs more.
The manual is actually pretty good at explaining how it works. We still had to close warranty stations because they either can't read or refused to understand what they were fixing. That was the biggest issue, most techs did not understand how these worked, but dove right in anyway. These days the situation is worse as you can see. There was a very good reason Carver restricted service on these and did not release service information. Normally I have a problem with that, but sometimes with truly advanced ideas and design they are forced to do this. I can't tell you how many mag coils we sold (no returns) after warning the buyer that this part was not the problem. Then getting complaints that the new part was defective!
These days I am so tired of what hacks do to equipment! I thought it was as bad as it could get years ago, but the situation continues to deteriorate! I'm so glad I'll retire in a couple years I think.
-Chris
Hi all, mind if I hyjack this thread?
I have a Carver M1.5t that I suspect the transformer primary is toast.
I have had this for a while, many many years and I dont recall, but I think I tried to repair it a while back many years ago. I have the repair manual and one of the steps was to remove one of the leads to the fault led. I believe I was attempting to go through the steps many years ago, because when I pulled it back out and blew off the dust many years later to try and fix it, the led was still disconnected.
Being many years later, I thought nothing of a disconnected led....its just an led after all, and I plugged in the amp to see what was wrong again.
Reading the manual again today I see that this disconnected led leaves the amp un protected!! Oh boy (Face palm).
What its doing:
When plugged in it hums very bad, and the right channel led strip lights up. I have never plugged it in for more than a few seconds because well, it just sounds like its drawing some serious current....it has not popped the fuse though.
I connected it to a variac and slowly bright the voltage up until the triac fires (I dont have a means to see the wave form....yet), and as soon as it fires, the hum is back. It does fire right around 60V like its supposed to.
I placed my meter in line of the power cord and its measuring 2.5A when the triac begins to fire at 60V. I also have zero volts dc on the output caps....all of them....nothing.
Another carver repair manual suggests shorting the triac to send line voltage to the transformer, so I did this just to see, and when I "just every so barely, just the slightest spin" on the variac....Im talking probably less than 5-10v, I am pulling 3A.
Am I hosed? Is this Mag coil toast?
Thanks.
I have a Carver M1.5t that I suspect the transformer primary is toast.
I have had this for a while, many many years and I dont recall, but I think I tried to repair it a while back many years ago. I have the repair manual and one of the steps was to remove one of the leads to the fault led. I believe I was attempting to go through the steps many years ago, because when I pulled it back out and blew off the dust many years later to try and fix it, the led was still disconnected.
Being many years later, I thought nothing of a disconnected led....its just an led after all, and I plugged in the amp to see what was wrong again.
Reading the manual again today I see that this disconnected led leaves the amp un protected!! Oh boy (Face palm).
What its doing:
When plugged in it hums very bad, and the right channel led strip lights up. I have never plugged it in for more than a few seconds because well, it just sounds like its drawing some serious current....it has not popped the fuse though.
I connected it to a variac and slowly bright the voltage up until the triac fires (I dont have a means to see the wave form....yet), and as soon as it fires, the hum is back. It does fire right around 60V like its supposed to.
I placed my meter in line of the power cord and its measuring 2.5A when the triac begins to fire at 60V. I also have zero volts dc on the output caps....all of them....nothing.
Another carver repair manual suggests shorting the triac to send line voltage to the transformer, so I did this just to see, and when I "just every so barely, just the slightest spin" on the variac....Im talking probably less than 5-10v, I am pulling 3A.
Am I hosed? Is this Mag coil toast?
Thanks.
Mag coils seldom go bad. I was factory warranty for Carver in Canada.
Training is required to properly service these amplifiers, and they are pretty darned reliable if serviced properly.
Training is required to properly service these amplifiers, and they are pretty darned reliable if serviced properly.
No jean-paul, they are not unreliable. Technicians who don't understand how they work are the problem.
I have only seen one dead transformer (mag coil). It was a unit plugged into 550VAC in a unit made for 120 VAC. Plasma cut through the case from inside transistors (melting the top case of the TO-3 transistors). Extreme. I have seen completely destroyed electronics because someone messed with the regulator and the voltage went through the roof, mag coil fine. More than once.
We sold many mag coils after warning the "tech" they were not the problem. Most tried to return them after we told them there was no return and that wasn't the problem. Understand the mag coil is not a normal transformer.
I received training on how to troubleshoot and bring up them up after service. Service manuals assume you understand the basics of how to do the work. A service manual only usually points out specifics for that device. In the case of Carver, that means you are trained on how they work before hand. The same was true of Marantz and every other brand I worked on. The Marantz 500 was special, the manual gave you specifics but did not include the basics training on them.
Just because equipment requires training on how to service it does not mean it is unreliable. These amplifiers were abused by scores of DJs and club system installers and survived. The worst thing you could do is run them off a cheap generator, or through a long extension cord. The second is high level high frequencies since the commutators were timed for bass frequencies and that would lock them up. All in the owners manuals.
A 1.5 model actually does deliver 375 watts per channel into 8 ohms. Power has to be low impedance and good. Just like with any other high power amplifier. When servicing a high power amplifier, you must know what you are doing and get it right. Rails are +/- 125 VDC in these.
I have only seen one dead transformer (mag coil). It was a unit plugged into 550VAC in a unit made for 120 VAC. Plasma cut through the case from inside transistors (melting the top case of the TO-3 transistors). Extreme. I have seen completely destroyed electronics because someone messed with the regulator and the voltage went through the roof, mag coil fine. More than once.
We sold many mag coils after warning the "tech" they were not the problem. Most tried to return them after we told them there was no return and that wasn't the problem. Understand the mag coil is not a normal transformer.
I received training on how to troubleshoot and bring up them up after service. Service manuals assume you understand the basics of how to do the work. A service manual only usually points out specifics for that device. In the case of Carver, that means you are trained on how they work before hand. The same was true of Marantz and every other brand I worked on. The Marantz 500 was special, the manual gave you specifics but did not include the basics training on them.
Just because equipment requires training on how to service it does not mean it is unreliable. These amplifiers were abused by scores of DJs and club system installers and survived. The worst thing you could do is run them off a cheap generator, or through a long extension cord. The second is high level high frequencies since the commutators were timed for bass frequencies and that would lock them up. All in the owners manuals.
A 1.5 model actually does deliver 375 watts per channel into 8 ohms. Power has to be low impedance and good. Just like with any other high power amplifier. When servicing a high power amplifier, you must know what you are doing and get it right. Rails are +/- 125 VDC in these.
I think in this case “unreliable” meant “won’t tolerate DJ torture” or “won’t run properly off a generator or long extension cord”. Such use simply needs a different type of amplifier. One can make amplifiers that can - even H-class - but they need regular transformers.
Well, they will survive DJs. Most high power amplifiers have issues with smaller generators with poor regulation. Long extension cords cause high voltage drops.
The problem is that Carver uses a regulation circuit that draws more AC current to maintain internal voltages, just like a switching power supply. This allows full power unless operating conditions are not reasonable.
Cheap AC generators under and overshoot badly with the variations in current draw. With a Carver, this is more severe. This is not the amplifier's fault at all. It is the person using it. We saw this with Parade floats (one in particular).
Use proper equipment, no trouble. Go cheap and stupid = trouble.
We had the most trouble with folks who decided they knew how to fix something they weren't trained on. Good techs could figure them out. We also saw the same poor work on Cyrus and other good brands. Just poor, lazy workmanship with a lack of understanding on how they worked. You've seen it too.
The problem is that Carver uses a regulation circuit that draws more AC current to maintain internal voltages, just like a switching power supply. This allows full power unless operating conditions are not reasonable.
Cheap AC generators under and overshoot badly with the variations in current draw. With a Carver, this is more severe. This is not the amplifier's fault at all. It is the person using it. We saw this with Parade floats (one in particular).
Use proper equipment, no trouble. Go cheap and stupid = trouble.
We had the most trouble with folks who decided they knew how to fix something they weren't trained on. Good techs could figure them out. We also saw the same poor work on Cyrus and other good brands. Just poor, lazy workmanship with a lack of understanding on how they worked. You've seen it too.
Mag coil was indeed fine. Did some more digging in and found a short on the secondary side. Removed the short and the primary hardly pulled any current. Amp still has a fault, but at least its not the mag coil.
You shouldn't hit the mag coil with full voltage, just in case. They don't like sine wave inputs either. Remember, it is a special transformer, not like the type you are familiar with.
Not hitting the mag with any full voltage. Barely got 5v on the 50v output with triac shorted and using variac.
Testing so far led me to a shorted MPSU60 transistor (Q13).
These are not manufactured anymore,
Can anyone suggest a drop in replacment?
Thanks.
Testing so far led me to a shorted MPSU60 transistor (Q13).
These are not manufactured anymore,
Can anyone suggest a drop in replacment?
Thanks.
Use a TO-126 device and move the package so the leads line up. On Semi used to have MPSW (MPSW42/MPSW92) devices that would work perfectly, long discontinued. There were some Japanese numbers as well, long gone. Same package as the MPSU. Those were called "uniwatt" and they had a "duowatt" package as well.
Given the TO-126 is not a direct replacement, I am sure it would be wise to replace both channels with the same part.
Do you know what sort of effect this will have on the amps function?
Also, should I be concerned with it being connected to the 125v rails but only have 80v Vceo and Vcbo?
Do you know what sort of effect this will have on the amps function?
Also, should I be concerned with it being connected to the 125v rails but only have 80v Vceo and Vcbo?
Hi, Carver guy here. I'm running and servicing many racks of those. Though there is not much of fixing, I find those to be really reliable. All you have to do it use amp for what it was designed and use some common sense. Example do not use PM1.5 to drive double 18'' subwoofer. If you have such needs use PT2400 and all is going to be fine.
Your question about mpsu replacement. Those are long gone. You might get lucky on ebay and get some. If you prefer to use new part I can tell you what Carver did at later amps. They've used MJE340 and MJE350. I'm not sure which one is npn and which one pnp. If you feel to use better transistors TTA004b and TTC004b are great ones though lower on voltage. TTA006b and TTC011b are higher voltage ones. Probably even better for the job would be KSC3503 and KSA1381, those are low Cob and Cre, voltage is high just fT is way higher than original MPSU ones which might lead to some sort of problems/instability/oscillation so be careful and check it with scope. Compare datasheets and make own conclusions.
Best regards and good health, Taj
Your question about mpsu replacement. Those are long gone. You might get lucky on ebay and get some. If you prefer to use new part I can tell you what Carver did at later amps. They've used MJE340 and MJE350. I'm not sure which one is npn and which one pnp. If you feel to use better transistors TTA004b and TTC004b are great ones though lower on voltage. TTA006b and TTC011b are higher voltage ones. Probably even better for the job would be KSC3503 and KSA1381, those are low Cob and Cre, voltage is high just fT is way higher than original MPSU ones which might lead to some sort of problems/instability/oscillation so be careful and check it with scope. Compare datasheets and make own conclusions.
Best regards and good health, Taj
Oh darn, i pulled yhe trigger to soon.
I just purchased some MJE15035G i found someone else said was a replacement.
Oh well. Now i got options. Lol.
Thank you for the post, ill check out thr ones you suggested as well.
I just purchased some MJE15035G i found someone else said was a replacement.
Oh well. Now i got options. Lol.
Thank you for the post, ill check out thr ones you suggested as well.
No, just deal with the bad channel. Replace it and the complimentary device, so MPSU10 and MPSU60. MPSU10 is the NPN device.
Use a device rated for the voltage it will see plus safety margin. Your biggest problem is the original uses EBC pinout, modern packages went to ECB. The dissipation with MPSU devices is 1 watt. You could make an adapter PCB I guess.
Do not buy from Ebay unless you know for sure the part is real, don't buy new manufacture either, unless it is a licenced company (read expensive as sin). You are way further ahead with current production devices, new numbers.
Hi Taj,
MJE340 is the NPN, MJE350 is the PNP. Using some parts that differ greatly in characteristics is a good way to get into stability trouble. The holes need to be carefully enlarged.
Nothing wrong with a PM 1.5 to drive a pair of 18" woofers at all. The PT-2400 / TFM75 is a heavier amplifier and different in design. The biggest issues with the PM 1.5 are the dual capacitors. I remade the original factory replacement part exactly (and I have an original). Then there are those fans. If you don't keep the shaft lubricated they tend to seize. Sometimes the rectifier on that supply shorts, indicating bad fan(s). In no way do these amplifiers have a problem with driving a 4 ohm load, the size of the driver doesn't factor in at all.
I think the TFM-75 was the nicest amplifier Carver ever made. Very pretty too.
Use a device rated for the voltage it will see plus safety margin. Your biggest problem is the original uses EBC pinout, modern packages went to ECB. The dissipation with MPSU devices is 1 watt. You could make an adapter PCB I guess.
Do not buy from Ebay unless you know for sure the part is real, don't buy new manufacture either, unless it is a licenced company (read expensive as sin). You are way further ahead with current production devices, new numbers.
Hi Taj,
MJE340 is the NPN, MJE350 is the PNP. Using some parts that differ greatly in characteristics is a good way to get into stability trouble. The holes need to be carefully enlarged.
Nothing wrong with a PM 1.5 to drive a pair of 18" woofers at all. The PT-2400 / TFM75 is a heavier amplifier and different in design. The biggest issues with the PM 1.5 are the dual capacitors. I remade the original factory replacement part exactly (and I have an original). Then there are those fans. If you don't keep the shaft lubricated they tend to seize. Sometimes the rectifier on that supply shorts, indicating bad fan(s). In no way do these amplifiers have a problem with driving a 4 ohm load, the size of the driver doesn't factor in at all.
I think the TFM-75 was the nicest amplifier Carver ever made. Very pretty too.