Carver PM-1.5a amp

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N_Cook 15 years ago

Serious amount of damage on one ch from someone using handfulls of white goo under the TO3 ," insulating" the pins as they were inserted through it into the TO3 sockets, causing sparking and destruction of that socket and a load of colateral.

Plenty of info out there

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eservice etc

But nowhere can I find the ,no load, quiescent draw from the mains. I have bypassed / isolated the mains triac board and powering via metered variac to the transformer direct at these preliminary stages of powerup. Running at 50 percent mains about 0.1 amp current draw and all monitored DC levels match between channels and clean signal on output and ps rails half expected values. Increase to 60 percent and draw climbs abruptly to 0.5 amp . So far quickly returned to 50 percent and nothing obviously overheating. Anyone happen to know the expected draw?

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Meat Plow 15 years ago

PM1200%20

Adaptive or commutating power supply. Adds more rail the harder it's driven.

Rails don't like continuous sine waves. May provide some explanation to what you are seeing. Also subject to back EMF. Wasn't my favorite amp, lots of engineering revisions/bulletins.

Live Fast, Die Young and Leave a Pretty Corpse

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Arfa Daily 15 years ago

May not be a genuine problem that you're seeing. Like you, I always bring suspect amps up with a variac, but on more than a few occasions, I've seen amps that just do not like reduced supply input levels, and behave exactly as you describe, but with no obvious signs of distress from the output stages. If you (dare to) keep going up, suddenly, everything evens out, and the input current returns to a more 'normal' level.

Arfa

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Phil Allison 15 years ago

"Meat Plow"

** Bollocks.

There is a triac "dimmer" circuit in the AC voltage feed to the power ranny - it acts to regulate the ( multiple )DC rails under load.

This allows a very small AC tranny to be used with limitations on duty cycle.

** More bollocks.

** Ever heard of " I mag " with iron core transformers ????

Once the saturation level is reached, it tends to go ballistic.

.... Phil

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Phil Allison 15 years ago

"Arfa Daily"

** The PM-1.5 will explode if you do this.

..... Phil

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Meat Plow 15 years ago

F*ck off Phil

Live Fast, Die Young and Leave a Pretty Corpse

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N_Cook 15 years ago

white

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I had to check whether I'd connected mains to one 120V primary by mistake as it was that sort of effect but without saturation noise from the transformer. Will return to it later today and also try engaging the triac section as I've not got my head around the on demand draw triac instead of good load/bad load or brownout triac

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N_Cook 15 years ago

Very awkward wrapped-up around itself amp to work on. With so many supply rails and 50 percent values I'd not noticed a blown up and shorted

3900uF,50V electro in the ps. Another 20 minutes getting that sub-board out, anything to avoid taking the whole amp apart with all those 24 TO3 sockets demounted , frail soldered-in interboard "headers" etc

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Meat Plow 15 years ago

They were not my favorite amp to work on.

Live Fast, Die Young and Leave a Pretty Corpse

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N_Cook 15 years ago

Correcting the ps there was still high current draw above 50 percent mains , so re-engaged the triac cct

Now powering up via the mains plug proper, via the on-demand triac, the mains current is stable at 210mA at 70 percent of 240V . No hotspots but will take various voltages on ps and both ch, with loads on outputs, before upping any more.

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Carver PM-1.5a amp

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