Carver M500 power amp start up problems. - diyAudio
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Old 14th April 2008, 11:43 AM   #1
AMV8 is offline AMV8  United Kingdom
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Default Carver M500 power amp start up problems.

Hi

I could use some help from Carver experts.

I own a Carver M500 power amp and a Carver M500T power amp. The M500 is working and I have just repaired the M500T. Both are 120volt models. The working one I use with a 1000VA step down transformer that weighs 10kg.

I tried starting up the M500T that I had repaired on a variac for safety. It is a Claude Lyons high quality variac that weight 8kg and is 1200va.

The M500T emitted squealing noises as I increased the variac voltage over 60 volts. I tried a few times; always with the same result. I then tried the working M500 power amp. To my surprise I got squealing noises form that also. ( However this power amp is definalely working OK when used with a a step down transformer ).

Does this mean that I can not use a variac to test start a carver power amp.

NOTE; Yes these are magnetic field carver power amps. Possibly the triac does not like the varying voltage of the variac - any comments anyone?

Thanks in advance for any help or advise

Don
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Old 16th April 2008, 12:48 PM   #2
djk is offline djk
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Many amplifiers don't like a Variac, Carver being one.
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Old 16th April 2008, 01:30 PM   #3
e-mos is offline e-mos  Norway
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my carver pm1500 had no problem on a standard variac.
but it may be caused by a short-circuit in the amp or just that it draws a alot of current to charge the capacitors...

on my carver it has an extra switch just for charging the capacitors..
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Old 16th April 2008, 01:57 PM   #4
AMV8 is offline AMV8  United Kingdom
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Hi
Thanks for the reply.
The "good" amp is ok straight from the mains or on a 240/120 volt step down transformer (1250va).
I think I will try the repaired amp straight from the mains.
Don
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Old 16th April 2008, 02:41 PM   #5
john65b is offline john65b  United States
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Is this a 50hz/60hz issue?
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Old 16th April 2008, 02:59 PM   #6
AMV8 is offline AMV8  United Kingdom
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Hi

I do not believe that it is an issue of 50/60hz ( but what do I really know ). In the owners manual Bob Carver indicates that this should not affect the amps. Also I have converted two other carver power amps to 240v 60hz and they run ok.

Interesting idea though.

Don
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Old 16th April 2008, 06:36 PM   #7
e-mos is offline e-mos  Norway
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correct Don this is not 50/60hz issue

it is more likly a load isssue..



Don if you want some way to control the current/voltage to the amp you can use just a regular light bulb in series with the amp.

this way if the amp uses to much current the light bulb will lite up brightly if the amp works fine the light bulb will just lite up.

remmeber this is just for testing and adjusting the amp.

I would not recomend to test run with audio and load..
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Old 13th May 2008, 12:59 PM   #8
AMV8 is offline AMV8  United Kingdom
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To all those who posted - Thanks for your help.

Since the original post I have obtained copies of the M500, M500T and C500 service manuals. So here is some additional info that may helpothers in the future.

The C500 is a 250 watt per channel power amp and has a conventional power supply -- non magnetic field. The manual recomends using a variac when ssrting up during testing.

The M500 and M500T are 250 watt per channel power amps with "magnetic field" power supplies. The manuals say that the power amps need a "stiff" power supply. These manuals do not mention using a variac and the implication seems to be that the "magnetic field" power amps need the full supply voltage from switch on.

If anyone can add any more please let me know.

PS I now have my M500 and M500T power amps working

Don
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