Carver M1.5T Amp issue

[john65b]

Hey all,

I picked up a Carver M1.5T locally last night (somewhat cheap). I remembered the "Carver Challenge" and how this particular amp was design to emulate a Mark Levinson ML-2. I'll never get my hands on an original ML-2 (had an ML-3, and it was OK), so I picked it up. I took it home and opened her up and it smelled like a hamper. Cobwebs, dust, all sorts of crap. Blew it out with compressed air and cleaned it up a bit. The Power Caps looks like they had been replaced, and the monster resistors on outputs were different, so an upgrade or repair was done at some time.

I plugged it in to my system with a 6SN7 / 6SN7 Aikdo pre, and my Magnepan Tympani IVa and I have to say I was impressed. It had a bit of a "Hot Midrange" that I often hear on Pro Audio Equipment, probably designed in to properly convey dialog.

Anyway, it also had a bit of a dead space, null, between the speakers that was a bit odd. I switch the speaker polarity (or Phase) on one speaker and all was good. I know that my pre, DAC, and speaker wires are wired and connected correctly, and the one speaker I switched is correctly labeled on back of the amp (wrt pos and grnd). I don't know know how this could be, unless the previous repair tripped something up...

Anyway, anyone know of this issue?

[AMV8]

Hi
I have two Carver 500 power amps. I guess yours must work in the same way On both of the 500's, according to the Carver operation manual, one of the speaker outputs has to be wired not as expected. Then the amp works fine.
I have never looked at detail as to why this should be. However my guess is that as these as what Carver calls "magnetic field amps" ( really just class D or some other higher class of amplifier ) one of the channels is being operated out of phase with the other channel so that the channels use the transformer and make demands on the power supply at different times so that the power supply is being used more efficiently which allows a small power supply to drive a larger than expected amp. The problems are probably a lack of ability to drive transients and the switching noise from the power supply.
I think you need to look at a copy of the Carver operation manual for your amplifier. They can be found on the internet.
I hope this helps.
Don

[john65b]

Hmm, I wonder if this is something about the sonic holography crap, which was nothing more than a phase cancellation void to create a surround effect...

[kevinahcc20]

Originally Posted by john65b

Hmm, I wonder if this is something about the sonic holography crap, which was nothing more than a phase cancellation void to create a surround effect...

Doubtful...sonic holography was a feature in many Carver preamps but not to my knowledge ever in a power amp.

[john65b]

Well, that didn't take very long. Had my Listening session yesterday. As I wrote, sounded nice. I turned the amp off and a heard a nasty whine and thump...had me a little worried...I turned on the amp just now and it took to whole house circuit out - The fuse on the amp is still good - 15amp, jut like the house circuit. I also put in a Arc Fault breaker on the house circuit, and it tripped. Tried it again and it took the house circuit out again.

I opened the amp and found the transformer secondary is grounded. The big power caps look OK, not shorted. But the smaller caps could be the culprit?

EDIT:

I have taken out the big rectifier, and appears to not have any shorts. The eight other rectifiers are next to be checked. If OK, then those crazy caps are most likely the culprit...not looking forward to this...

[john65b]

I have to recheck the transformer secondary short to ground, as the meter I used is a piece of crap.

The dual caps appear to have no shorts, main caps have no shorts, and the 8 diodes and main rectifier has no shorts.

I know these amps have a monster inrush (could a CL60 thermistor on mains after fuse be of any help here?) and could just be the house's 15A circuit? The 15A on ampo was OK (slo Blo). There were a few other electronics on that same circuit when it blew (computer, preamp, desk lights, etc)

When I finished the basement, I put in Arc Fault breakers on all circuits into my work area, as the electrical code is / was heading in that direction (and made the wife happy). From what I understand, like a ground fault on the Neutral leg. Could it be that its a bit sensitive to the amp?

[Tajzmaj]

Hi.
I have a lot o Carver amps which I use in ,,pro,, applications. M1.5 is basically the same amp as PM1.5. An PM 1.5 also produces nasty thump noise when turned off. Of course so long till you replace all small electrolytic capacitors. It is nothing special in there but a lot of work. It is also worth to replace trimmers and readjust the amp......
t is good amp but it is old and it need some attention...
Regards, Taj

[john65b]

Thanks for teh info Tajzmaj...

Is the CL60 Thermistor on the mains a good idea as a soft start?

[Tajzmaj]

About that I don't know but I don't have problems with too high inrush current.
Regards, Taj

[Tajzmaj]

p.s.
But be careful. You need stiff line if you want that Carver's psu works properly.
So maybe thermistor is not good idea.
Regards, Taj