Carver m1.0t Power Supply Problem

dr*audio

dr*audio

Fish fingers and custard!
I picked up a m1.0t that won't turn on. It doesn't seem to be turning on the triac in the supply. Transistors are good, beta = 200. I have 110VAC on the triac, only about 200mV on the gate and nothing on the output. I replaced the phase shift cap, no help. Transformer ohms out ok. Anyone have any experience with this circuit?
 
hrballenger said:
Go to http://thecarversite.com and down load the Carver M-1.0t Triubleshooting guide. DO NOT jumper the triac while trying to troubleshoot; it WILL blow the transformer.
Click to expand...

Re: Troubleshooting guide, will do.
Re: Jumpering triac, won't do. I already considered that and didn't do it because that's not the way the transformer is meant to be driven and it would also remove all the regulation for the supply, if it would have worked. I know the transformer is only driven for part of the phase.
I did try another (but not the same part) triac, but it didn't work either. It appears to not be driving the triac with enough voltage to trigger it.
 
Does it have a DIAC in there. I (vaguely) remember a DIAC going bad sometimes. I think, if it's there, it was a 40V DIAC.


Nevermind, I just downloaded the schematic. No DIAC on this one.
 
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It looks like that wad of transistors is a DIAC substitute. Q's 401~404

I'm sure you've checked R-408 (4.7 ohm).

I think that that wad of transistors maybe taking advantage of the transistors breakdown properties to generate the trigger for the Gate on the TRIAC.

You might check PC-401 too It's an opto-coupler that puts a DC load across bridge D-401. It uses that Revox AC motor speed control trick. Vary the impedance across the DC path of the bridge to modulate the AC.
 
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Here ya go. See page 6 for power supply tips
 

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  • Carver M-1.0t troubleshooting guide.pdf
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Last edited:
Jon_Logan said:
It looks like that wad of transistors is a DIAC substitute. Q's 401~404

I'm sure you've checked R-408 (4.7 ohm).

I think that that wad of transistors maybe taking advantage of the transistors breakdown properties to generate the trigger for the Gate on the TRIAC.

You might check PC-401 too It's an opto-coupler that puts a DC load across bridge D-401. It uses that Revox AC motor speed control trick. Vary the impedance across the DC path of the bridge to modulate the AC.
Click to expand...

"I'm sure you've checked R-408 (4.7 ohm)."
I had planned to do that next. Got tired after a long day yesterday.
The manual says something about charging and discharging C405 and turning on that clump of transistors, which drives the gate.
 
hrballenger said:
Here ya go. See page 6 for power supply tips
Click to expand...

Very cool Hrballenger. I've been to the Carver site many times and never saw this. Do they have them for the M1.5T and the TFM45? I have both of those amps and they both need help.
 
The Troubleshooting Guide was extremely helpful! Turned out the +/- 30V bridge rectifier was shorted and loading the supply down so it couldn't start up. Following the instructions for isolating the supply, it was easy to find the culprit. All fixed and sounding great. Thanks to all who contributed. I have worked on quite a few of the Carver Magnetic Field amps, but this is the first one that didn't start up. Now I am familiar with how it works.
 
And then, almost 3 years LATER!!

dr*audio said:
The Troubleshooting Guide was extremely helpful! Turned out the +/- 30V bridge rectifier was shorted and loading the supply down so it couldn't start up. Following the instructions for isolating the supply, it was easy to find the culprit. All fixed and sounding great. Thanks to all who contributed. I have worked on quite a few of the Carver Magnetic Field amps, but this is the first one that didn't start up. Now I am familiar with how it works.
Click to expand...



I'm just getting to one here on my bench. Owned by the former touring bass player for Sinatra and the Tonight Show with Johnny Carson.
Output fail on the finals. What the heck is a 11000 power transistor?

I'm new to Mag amps
 
Just join "TheCarverSite". There are a handfull of tech's there that can help you out.

BillWojo
 
Thanks for the tip. I just registered there. Working on an M1.0t here that won't power up. Blows fuses. Makes a clicking when spkrs hooked up in stereo mode and LEDs blink right before fuse blows. Owner gave it to me saying, "It's dead. Take it." I'll report my findings here. Thanks.
 
Can someone repost that troubleshooting guide for the Carver M-1.0t? The carver site doesn't have it anymore and the link in this thread are too old as well.. Thanks!!
 
Yes, there is an inverting version. I don't know much about the details.
I'm glad to have found that document as well - I have a m1.0t here that I've tried to repair and failed. My triac appears to be OK but I do not have correct voltages after the rectifier, but I've replaced all of that. And isolated it - it's just a mystery and I did try for help at the carver site and did get a little help, but I couldn't generate much interest.

So, I'll try again with this doc - someday, I have a m200t on the bench now that I haven't been able to get to (work, weather, life).
 
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