Carver M1.0t Loud "tong tong" noise - diyAudio
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Old 2nd January 2006, 08:30 PM   #1
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Default Carver M1.0t Loud "tong tong" noise

Hi .
Hope somebody can help with this weird one.

One of my Carvers M1.0T emits very loud "tong tong tong" sounds, intermittent after playing for a few hours at normal listening level. Powering the unit down shuts the noise and powering it back up brings it back, for that occasion only. If I let it sit powered down for a few hours, the unit runs fine.
It is connected to 4 ohms speakers and is fed by a Crown Preamp.
The "tong" sounds are physical as well as audible and can be felt at the front plate. When opened, the unit refused to cooperate: cannot locate the source of the bang.
When the loud "tongs" are heard, there is no music coming from either speakers (as far I as can tell). This happened twice in the last month.
The Crown Preamp is very stable and works perfectly well with a replacement Power Amp.
The diodes on the 2 small bridges have been replaced by heftier ones and the unit has been serviced once for "bias problem".
I noticed there is a large transfo, closed to the front plate but not touching it. Could this be the culprit.
The repair techie will have a fit when told of this one. Bangs of this sort happen on rotating equipment, not on amplifiers!

I must add: the AC voltage in my house is always around 125-126 Volts, which stresses everything, including light bulbs, Power Amps and the like...
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Old 2nd January 2006, 09:18 PM   #2
anatech is offline anatech  Canada
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Hi Visigoth,
This sounds like the triac is firing unevenly. It could be your AC supply that is at fault too. Try your amp at a friends house in another area of town to make sure.

The Carver does not have a transformer, it's a mag coil. The amp preregulates the incoming energy and could very well make this noise. Your higher AC voltage will actually lower the current draw to the amplifier.

Now this is not a normal amp at all. The tech to service this amp needs to have experience with these. If not, chances at repair are slim. The chance to have extra damage caused by service is great. Most tech's are very proud and do not like to admit they don't know how to fix something. So if it needs service, take it to someone who knows for sure how to service it.

-Chris
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Old 3rd January 2006, 04:30 AM   #3
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Hi Chris

Thanks for the information. I will pass it on to my repairman.
Together with some other info I gathered on this site, like replacing the caps with higher working voltage ones, whould do the trick (18 year old caps should be just about dried up by now)
Will keep this site posted.

Regards.
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Old 3rd January 2006, 08:48 AM   #4
clem_o is offline clem_o  Philippines
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Had a Carver sitting in the house once - did the same thing. If you run it at a lower line voltage, the pinging sound stops...

Cheers!
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Old 3rd January 2006, 11:57 AM   #5
anatech is offline anatech  Canada
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Hi Visigoth,
We must thank Clem! Try your unit somewhere else with lower line voltage. When the phase angle gets too low, it will not fire evenly. Troubleshooting a non-fault is expensive (or can be).

-Chris
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Old 3rd January 2006, 11:35 PM   #6
clem_o is offline clem_o  Philippines
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Hi Chris, Visigoth -

I'm not sure if the particular unit I had really did have a problem or not, one other fact that bothered me was the cooling fan, which is supposed to be power-demand modulated also seemed to be racing and hunting (despite the fact the amplifier wasn't really being pushed). The line voltage was about 115V, hardly what you'd call "out of spec", but yes, the pinging did stop when the line voltage was dropped further...

Cheers!

Clem
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Old 3rd January 2006, 11:50 PM   #7
anatech is offline anatech  Canada
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Hi Clem,
Your amp probably had intermittent supply sensing resistor connections. The supply should run evenly at 115V, triac firing should be very consistant. Your fan racing shows there was a serious problem with the supply. Serious in that this can cause fireworks if the voltage is allowed to rise very high.

Bad main filter caps can cause the exact same thing. For the same reason (supply sensing).

-Chris
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Old 3rd January 2006, 11:59 PM   #8
clem_o is offline clem_o  Philippines
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Hi Chris,

Many thanks for the info! I'll have to tell the neighbor about that; in the meantime he's very happy with the thing (why? - don't know! - its a PM600, a truly PA type amplifier, and he's using it with his domestic speakers...)


Cheers!

Clem
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Old 4th January 2006, 12:11 AM   #9
anatech is offline anatech  Canada
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Hey Clem,
If you dive into it, let me know what you find.

-Chris
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Old 4th January 2006, 12:17 AM   #10
clem_o is offline clem_o  Philippines
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Hi Chris.

Will do!

Cheers!

Clem
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