Carver PM1.5 startup issue - diyAudio
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Old 19th November 2005, 08:04 AM   #1
jimkarl is offline jimkarl  United States
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Default Carver PM1.5 startup issue


I have one of the older PM1.5 amplifiers. It's had a problem for a few years that I want to get rectified. When I turn the unit on, it goes into protection mode every couple of seconds. It does this 10-15 times on 2-4 second intervals. Eventually, that stopsand the unit works fine from that point on. It's as if it needs to "heat up".. Seems particularly worse when it's been in the cold for some time. It doesn't do this if I power it off and right back on again, just after it's been sitting.

Are there any known issues with this model in this regard? Any components that may have seen the end of their life and need to be replaced and if sodoes anyone have any ideas on what to check?
Does anyone have service manual they can email me?


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Old 19th November 2005, 05:32 PM   #2
anatech is offline anatech  Canada
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Hi Jim,
Found your thread.

The main filter caps tend to go open (there are 6 I think), there are some voltage sense resistors that like to change value on the voltage regulator PCB.

This is not a normal amplifer. The big Triac preregulates the AC, the transformer is a Mag coil (totally different). Do not short the triac and connect to the AC supply, incredible damage will result.

There are also bad solder connections on the input coupling cap. That's in another thread. It causes intermittent sound.

The dual section capacitors had a PCB made up for replacement with two individual caps to replace the dual caps. I'm out, so contact Carver service for those. (Sunfire?) You need two of them.

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Old 22nd November 2005, 12:36 AM   #3
Enzo is offline Enzo  United States
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And if it warms up and runs, then get a can of freeze spray, that is what it is for. Spray chiller on various parts to see if something reacts to being cold again.

I just hate working on those, inevitably ther is a burnt up resistor down where yu can't easily get at it.
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Old 22nd November 2005, 01:15 PM   #4
anatech is offline anatech  Canada
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Hi Enzo,
Yup, those are the voltage sensing resistors that overheat. Replace with higher wattage metal oxide types. The solder also tends to crystallize and the traces may be lifted. Work with solder flux, more fresh solder and patence before attempting to desolder the old parts. Don't apply too much pressure when using your probes either.

I strongly suspect the dual cap units. Look at the ripple with a 'scope.

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