Hello - I've been reading through some of the threads here but haven't quite found a solution for this Carver PM1.5 I'm working on.
The amp has a low "ticking" sound that's audible in the speakers and from I believe the power transformer. Fans barely move at this point either. Signal passes fine other than that in both channels. No protection light on.
Here's what I've tried:
1. If I set RP1 power supply to minimum, everything is OK. Fans full speed, no ticking. As I ramp it up, the fans slow down and ticking starts.
2. I've replaced the triac, diac, diodes, and caps on the regulator board just in case, no change.
3. I replaced OC1, no change
4. I've checked all the power transistors and they all seem OK, but I'm not 100% sure because I had a suspect ohm meter.
5. I have a variac to check things and I have a scope. I can get readings, but I'm not sure where to start.
I'm using the Carver Service Manual PM1-5, which they kindly emailed to me.
Thanks for your help
-kdawg
The amp has a low "ticking" sound that's audible in the speakers and from I believe the power transformer. Fans barely move at this point either. Signal passes fine other than that in both channels. No protection light on.
Here's what I've tried:
1. If I set RP1 power supply to minimum, everything is OK. Fans full speed, no ticking. As I ramp it up, the fans slow down and ticking starts.
2. I've replaced the triac, diac, diodes, and caps on the regulator board just in case, no change.
3. I replaced OC1, no change
4. I've checked all the power transistors and they all seem OK, but I'm not 100% sure because I had a suspect ohm meter.
5. I have a variac to check things and I have a scope. I can get readings, but I'm not sure where to start.
I'm using the Carver Service Manual PM1-5, which they kindly emailed to me.
Thanks for your help
-kdawg
Hi kdawg,
You can not begin to repair this amplifier until you understand how it works. The ticking sounds like the triac is firing unevenly. Replacing the triac, diodes and optocoupler would not have helped in this case.
The dual capacitors can do this. I assume that you've replaced those from your comments. Did you check the resistors in the voltage regulator section?
If you can not trust your equipment, replace it. A Fluke is the best handheld meter. Most others are worthless in comparison.
-Chris
Man, you almost made that amp into a nightmare repair!!! Read your manual, then read it again until you understand it.
You can not begin to repair this amplifier until you understand how it works. The ticking sounds like the triac is firing unevenly. Replacing the triac, diodes and optocoupler would not have helped in this case.
The dual capacitors can do this. I assume that you've replaced those from your comments. Did you check the resistors in the voltage regulator section?
If you can not trust your equipment, replace it. A Fluke is the best handheld meter. Most others are worthless in comparison.
-Chris
PM 1.5
Anatech is absoulutly correct, these amps are class H and switch between three power rails to decrease dissipation and increase overall efficiency. You dont want to take your carver amp into your local TV repair shop, you will probanly end up with a $300 repair that started at as a.5 cent resistor.
As anatech stated re- read your manual and check the power regulation section, the up-right board on the left in the middle with the up-right variable resistor. There are two resistors in the feed back network the set the center point if one goes open the amp with cycle the protection circuit. I believe this was a very common repair and was later rectified by replaceing the 1/4 watt resistors with 1/2 watts and moveing them away from the large 3w heat producer.
.
Anatech is absoulutly correct, these amps are class H and switch between three power rails to decrease dissipation and increase overall efficiency. You dont want to take your carver amp into your local TV repair shop, you will probanly end up with a $300 repair that started at as a.5 cent resistor.
As anatech stated re- read your manual and check the power regulation section, the up-right board on the left in the middle with the up-right variable resistor. There are two resistors in the feed back network the set the center point if one goes open the amp with cycle the protection circuit. I believe this was a very common repair and was later rectified by replaceing the 1/4 watt resistors with 1/2 watts and moveing them away from the large 3w heat producer.
.
The amp was given to me in this condition, they had been running it for quite some time with the misfiring triac. I've never raised RP1 above the point that it was set when I got it, I know that could fry it. Since I didn't see a fault light, there shouldn't be any active shutdown protection occuring correct?
I haven't replaced C13/14 because of the dual can issue NLA. Would I be able to see on the scope across the caps if they are not keeping the DC steady?
I found these caps at mouser, would they work? (2200 uF / 63v and 2200 uF 100v)
http://www.mouser.com/search/ProductDetail.aspx?R=KMH63VN222M22X35T2virtualkey66100000
http://www.mouser.com/search/ProductDetail.aspx?R=KMH100VN222M30X40T2virtualkey66100000
Would I still have to fashion a PCB to integrate these to the power supply board?
Thanks!
-kdawg
I haven't replaced C13/14 because of the dual can issue NLA. Would I be able to see on the scope across the caps if they are not keeping the DC steady?
I found these caps at mouser, would they work? (2200 uF / 63v and 2200 uF 100v)
http://www.mouser.com/search/ProductDetail.aspx?R=KMH63VN222M22X35T2virtualkey66100000
http://www.mouser.com/search/ProductDetail.aspx?R=KMH100VN222M30X40T2virtualkey66100000
Would I still have to fashion a PCB to integrate these to the power supply board?
Thanks!
-kdawg
If its ticking its a BOMB!!!!
QUICK SEND IT TOO ME!!
Sorry, couldn't let it pass.
Not to be offensive but you cannot just throw parts at something.
As mentioned earlier go thru the manual and pay attention to the power supply and regulation section. Check the board for any disscoloration of the board or the resistors. Check the current draw on the resistors and calculate to see if the resistors are indeed of high enough wattage.
Lastly, as with ANY repair work it is best done leaving the beer or mixed drink to the last therwise some spillage could occur which could lead to other that happy results. In other words you could fry your ***.
QUICK SEND IT TOO ME!!
Sorry, couldn't let it pass.
Not to be offensive but you cannot just throw parts at something.
As mentioned earlier go thru the manual and pay attention to the power supply and regulation section. Check the board for any disscoloration of the board or the resistors. Check the current draw on the resistors and calculate to see if the resistors are indeed of high enough wattage.
Lastly, as with ANY repair work it is best done leaving the beer or mixed drink to the last therwise some spillage could occur which could lead to other that happy results. In other words you could fry your ***.
Hi kdawg,,
Carver used to have a replacement PCB assy. I have heard of one member installing capacitors with standard long wire leads. The snap mounts require a PCB to be made. The originals will cause all kinds of problems.
Hi Joe,
Hi halo0925,
You sound like you've worked on these as well. You only made on error. A TV shop would write it off completely!
-Chris
Carver used to have a replacement PCB assy. I have heard of one member installing capacitors with standard long wire leads. The snap mounts require a PCB to be made. The originals will cause all kinds of problems.
That was maximum voltage. You almost blew the hell out of it.
Hi Joe,
You are more than half right!
So true. Thanks for saying that.
Hi halo0925,
You sound like you've worked on these as well. You only made on error. A TV shop would write it off completely!
-Chris
I've finally got around to getting back into this amp. Here's some things I've found (I did replace the dual output caps BTW):
1. The Protection LED was burnt out. I've replaced it and yes, it flashes immediately with the ticking now upon turing up the variac slightly.
2. Going through the troubleshooting guide in Section II, I've disabled the shutdown drive and jumpered the triac and I'm running it around 30% line power:
Q4 is turned on, and the base of Q2 (is 0V) does exceed Q3's base.
I have stable +/- 12 V
No DC offset signal on pin 3 of IC1
No over voltage shutdown on pin 12 of IC1
Q1 on the power supply board seems to be turned on. I am not seeing any voltage across R26 on either amp board, nor any oscilliation on outputs. R26 on pin 4 side sits at around 36VDC.
The guide says possibly defective Q1 (MPS A93), but of course I don't have one of those and have to order one unless anyone knows an equivalent that would work. Should I just order one and give it a shot? (a $0.15 part + $6 shipping geeze).
Halo - I'm not sure which resistors in the feedback section you are referring to. There are 200k resistors going to +/- 124V and 330K resistors going to +/- 36V. I'll check both anyways next time I get to the bench.
I learned also that this amp was used to drive the high frequencies in a biamped system before I got it which I've learned is BAD for this amp.
Thanks for helping me out, I'm just trying to save a good amp from the trash can.
-kdawg
1. The Protection LED was burnt out. I've replaced it and yes, it flashes immediately with the ticking now upon turing up the variac slightly.
2. Going through the troubleshooting guide in Section II, I've disabled the shutdown drive and jumpered the triac and I'm running it around 30% line power:
Q4 is turned on, and the base of Q2 (is 0V) does exceed Q3's base.
I have stable +/- 12 V
No DC offset signal on pin 3 of IC1
No over voltage shutdown on pin 12 of IC1
Q1 on the power supply board seems to be turned on. I am not seeing any voltage across R26 on either amp board, nor any oscilliation on outputs. R26 on pin 4 side sits at around 36VDC.
The guide says possibly defective Q1 (MPS A93), but of course I don't have one of those and have to order one unless anyone knows an equivalent that would work. Should I just order one and give it a shot? (a $0.15 part + $6 shipping geeze).
Halo - I'm not sure which resistors in the feedback section you are referring to. There are 200k resistors going to +/- 124V and 330K resistors going to +/- 36V. I'll check both anyways next time I get to the bench.
I learned also that this amp was used to drive the high frequencies in a biamped system before I got it which I've learned is BAD for this amp.
Thanks for helping me out, I'm just trying to save a good amp from the trash can.
-kdawg
Hi Joe,
Nice thought, thanks.
A donation to the forum would help us all.
Hi kdawg,
1. That's normal behavior for the protection LED.
2. Running at low supply might give you some whacky results, see above.
3. The MPSA93 can be replaced by MPSA92. These are high voltage parts. You can always test this transistor before making that decision.
Running at partial power, measure the DC voltages on all the TO-3 case transistors on the case. Draw it out, both channels. Measure all the voltages on the supply caps. Check the large diodes, all of them, with the power off and the supply discharged.
Go to the previous owner and slap them. They didn't read the darn manual.
-Chris
Nice thought, thanks.
A donation to the forum would help us all.
Hi kdawg,
1. That's normal behavior for the protection LED.
2. Running at low supply might give you some whacky results, see above.
3. The MPSA93 can be replaced by MPSA92. These are high voltage parts. You can always test this transistor before making that decision.
Those often go off value. Install higher wattage metal oxide parts. Just order them if you need any other parts.
You have no idea how bad this is for the amp.
Running at partial power, measure the DC voltages on all the TO-3 case transistors on the case. Draw it out, both channels. Measure all the voltages on the supply caps. Check the large diodes, all of them, with the power off and the supply discharged.
Go to the previous owner and slap them. They didn't read the darn manual.
-Chris
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