Carver PM-1.5 output noise and screech

pjaneiro · 10th August 2006, 07:04 AM

I finnally fixed my carver brick, i love this amp, ever since i sold my old 1200 i was sad all the time, i finnaly got my hands on a 1.5 wich is actually the same thing....well i think, i remember my 1200 having 1.5a boards in it, Anyways my problem is quite simple, on my 1200 i had gotten rid of the power down sound it made with an "upgraded" board i had gotten from a service center, and also they had sent me a service bulletin with pics on how to upgrade my inoput board for the output noise in the left channel, well the 1.5 is now fonctionnal but i have no idea where to get that upgraded board for the power down noise, and my input board has no marks identify the jumpers numbers so i can upgrade my input board...anyone has an idea, i know there a few carver gurus around here...

P.S. is there a way to change the motor driven fan to a dc fan ?

pjaneiro · 10th August 2006, 03:07 PM

No one heres knows what i'm talking about ? I'm sure Anatech has some input....Where are you oh great one

Netlist · 10th August 2006, 03:16 PM

He's still drinking his morning coffee.

/Hugo

pjaneiro · 11th August 2006, 03:59 AM

Come on guys, i'm going nuts over this one, for sure someone here knows what i'm talking about...

anatech · 11th August 2006, 08:07 PM

Hi pjaneiro, Hugo,
Sorry. Really slow out of the gate today. I'm not firing on all eight yet either.

Upgraded boards for a 1.5? Never seen one, but their was a circuit change (mod) available for excessive pops I think. It's entirely possible that a shop was doing the mods themselves. I believe there may have been "flying" parts involved (not mounted on PCB). I'll have a look in the archives.

Your fan is on it's own circuit. It is designed to vary the speed with the music. If you want to change it, you must use a slow run speed at the minimum, and vary the fan speed with heatsink temperature closely. Therefore you will need to sense the heatsink (chassis) temperature and your fan will be continuously variable. Your maximum CFM must be at least equalt to what you are taking out. The sensor needs to be shielded from the airflow.

-Chris

pjaneiro · 12th August 2006, 08:54 AM

Thanks for the reply, i was feeling all alone here...

Hmmm for the fan speed, well this model does NOT follow the music, neither did my pm-1200 both are the disco models, both models have a switch for full or half speed, i'd be glad to send the service manual for your viewing,

well i dunno what shop was doing those boards but i do know i delt directly with a guy from carver pro, his email addy no longer works, the screetch sound at power down i could live with, but that also is "feature" that i'd love to get rid of but it's the output noise in the left channel that's bugging me, i have the service bulletin to correct this, but my input board has NO markings whatsoever, and in my service manual the markings are just unreadable (poor scan i guess)

Tarzan · 12th August 2006, 01:00 PM

Hold on, I have to look in my docs.
There is something written about upgrades.
I'll be back later today or tomorrow.
Cheers,

anatech · 12th August 2006, 04:11 PM

Hi pjaneiro,
Ah, Carver Pro. They were not connected with the Carver service network at all. I did a repair for them and they didn't pay me, so I wrote them off. They may have figured something out. I am still looking through the mods.

In the back of the manual, they would list all factory changes to date. Still, I have some more info somewhere.

What this sounds like is the LV power supply is dying before the main supplies. There was one mod were they added resistors to drain the main supplies faster. I didn't like doing it because it generated more heat and would cause other problems down the road.

If you could, could you send the manual to bhomester at gmail dot com? I'll have a good look. They may have adapted an earlier mod to this later amplifier.

-Chris

pjaneiro · 13th August 2006, 07:12 AM

Thanks i just sent it, also i've read in one of your posts that an easy way to transform a regular line out to a balanced line out is to use a ssm2142, i've looked around but can't seem to find a schematic for the use, anyone can point me to the right direction ?

pjaneiro · 13th August 2006, 07:12 AM

Hi tarzan, did you have any luck on those upgrades notes ?

Thanks...

10th August 2006, 07:04 AM	#1
pjaneiro diyAudio Member Join Date: Jun 2006	Carver PM-1.5 output noise and screech I finnally fixed my carver brick, i love this amp, ever since i sold my old 1200 i was sad all the time, i finnaly got my hands on a 1.5 wich is actually the same thing....well i think, i remember my 1200 having 1.5a boards in it, Anyways my problem is quite simple, on my 1200 i had gotten rid of the power down sound it made with an "upgraded" board i had gotten from a service center, and also they had sent me a service bulletin with pics on how to upgrade my inoput board for the output noise in the left channel, well the 1.5 is now fonctionnal but i have no idea where to get that upgraded board for the power down noise, and my input board has no marks identify the jumpers numbers so i can upgrade my input board...anyone has an idea, i know there a few carver gurus around here... P.S. is there a way to change the motor driven fan to a dc fan ?

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10th August 2006, 03:07 PM	#2
pjaneiro diyAudio Member Join Date: Jun 2006	No one heres knows what i'm talking about ? I'm sure Anatech has some input....Where are you oh great one

10th August 2006, 03:16 PM	#3
Netlist diyAudio Moderator Join Date: Jan 2003	He's still drinking his morning coffee. /Hugo

11th August 2006, 03:59 AM	#4
pjaneiro diyAudio Member Join Date: Jun 2006	Come on guys, i'm going nuts over this one, for sure someone here knows what i'm talking about...

11th August 2006, 08:07 PM	#5
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi pjaneiro, Hugo, Sorry. Really slow out of the gate today. I'm not firing on all eight yet either. Upgraded boards for a 1.5? Never seen one, but their was a circuit change (mod) available for excessive pops I think. It's entirely possible that a shop was doing the mods themselves. I believe there may have been "flying" parts involved (not mounted on PCB). I'll have a look in the archives. Your fan is on it's own circuit. It is designed to vary the speed with the music. If you want to change it, you must use a slow run speed at the minimum, and vary the fan speed with heatsink temperature closely. Therefore you will need to sense the heatsink (chassis) temperature and your fan will be continuously variable. Your maximum CFM must be at least equalt to what you are taking out. The sensor needs to be shielded from the airflow. -Chris

12th August 2006, 08:54 AM	#6
pjaneiro diyAudio Member Join Date: Jun 2006	Thanks for the reply, i was feeling all alone here... Hmmm for the fan speed, well this model does NOT follow the music, neither did my pm-1200 both are the disco models, both models have a switch for full or half speed, i'd be glad to send the service manual for your viewing, well i dunno what shop was doing those boards but i do know i delt directly with a guy from carver pro, his email addy no longer works, the screetch sound at power down i could live with, but that also is "feature" that i'd love to get rid of but it's the output noise in the left channel that's bugging me, i have the service bulletin to correct this, but my input board has NO markings whatsoever, and in my service manual the markings are just unreadable (poor scan i guess)

12th August 2006, 01:00 PM	#7
Tarzan diyAudio Member Join Date: May 2004 Location: Genk	Hold on, I have to look in my docs. There is something written about upgrades. I'll be back later today or tomorrow. Cheers,

12th August 2006, 04:11 PM	#8
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi pjaneiro, Ah, Carver Pro. They were not connected with the Carver service network at all. I did a repair for them and they didn't pay me, so I wrote them off. They may have figured something out. I am still looking through the mods. In the back of the manual, they would list all factory changes to date. Still, I have some more info somewhere. What this sounds like is the LV power supply is dying before the main supplies. There was one mod were they added resistors to drain the main supplies faster. I didn't like doing it because it generated more heat and would cause other problems down the road. If you could, could you send the manual to bhomester at gmail dot com? I'll have a good look. They may have adapted an earlier mod to this later amplifier. -Chris

13th August 2006, 07:12 AM	#9
pjaneiro diyAudio Member Join Date: Jun 2006	Thanks i just sent it, also i've read in one of your posts that an easy way to transform a regular line out to a balanced line out is to use a ssm2142, i've looked around but can't seem to find a schematic for the use, anyone can point me to the right direction ?

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