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sick m400

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doctorpipe

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Joined: Fri Mar 06, 2009 1:27 am

Post Fri Mar 06, 2009 11:48 pm

sick m400

I have a early power supply m400 that has had new caps and triac installed. It has been working fine, and it got bridged for the first time and is now upset. It runs bridged or unbridged fine at low power. If it gets pushed to 25% or so it does the commutator buzz in the output. quit powerfully I might add. It flickers the power lights and buzzes until it settles down. lower the output level and it is fine. Any suggestions? Do I maybe have a rail that has a bad rectifier? It has been bullet proof for a couple of years now. It is easier to fix if it is plain broke. I can see the pattern on my lab scope when it goes nuts. Thanks for any help!
John
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OBI56

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SILVER-7 TUBE AMP

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Post Sat Mar 07, 2009 12:17 am

Re: sick m400

There are a few possibilities doctorpipe. When you say new caps, I'm assuming that you replaced ALL of the electrolytics, not just the ones in the power supply section. I also assume that you have checked both the 50V and 75V rails for proper operation and correct bias as per the service manual instructions. Otherwise you are probably looking for a bad diode or transistor in the commutation section. I think that BillD would have more info adn ideas for you to check out as he has serviced his M-400s before.

Keep us posted.
Why let facts or common sense get in the way of your opinions.
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TNRabbit

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(pair of) SILVER-7 TUBE AMPs

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Post Sat Mar 07, 2009 6:16 am

Re: sick m400

What load were you running it into bridged?
TNRabbit
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From FrankieD's lips to your ears: Sunfire - a quiet box of endless power.

Sunfire TG-IV/400~7 Amp
Carver SD/A-360 CDP
Benchmark DAC-1
Sony SACD/DVD-A
Active bi-amp: Ashly XR-1001 & 2 Rane PEQ-15s
Main: HotRodded AL-IIIs
Sub: Klipsch RT-12d
Center: Sunfire CRS-3c
Surround: Sunfire CRS-3 (x 2)

OconeeOrange wrote:"Gary likes to play it 'loud' as do I. His system begs you turn it up until you die"

RIP WIlliam B. Dibble, 1948-2012. I'll miss you my friend.
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BillD

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(pair of) SILVER-7 TUBE AMPs

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Post Sat Mar 07, 2009 10:53 am

Re: sick m400

Man, when you were in there, you should have replaced those rectifiers. IIRC, one of them you have to shift it forward to not hit one of the output devices. Here's what I replaced in mine.
  Code:
Part Type    Parameters  Vendor    Part #        Cost Qty Total    M-400      Assy   Manufacturer
Electrolytic 4700µF 100V Newark   95F4473      $11.05  2  $22.1   C30-C31      P/S   United Chemi-Con
Electrolytic  700µF  35V Digi-Key 493-1881-ND   $1.51  6  $9.06   C20-C25      P/S   Nichicon
Electrolytic   10µF  35V Digi-Key 493-1850-ND   $0.23  3  $0.69  C1,C5,C16     P/S   Nichicon
Electrolytic  1µF    50V Digi-Key 493-1886-ND   $0.23  4  $0.92 C6,C8,C10,C3   P/S   Nichicon
Electrolytic  22µF   16V Digi-Key 493-1769-ND   $0.15 10  $1.51   C7,C9,C14    P/S   Nichicon
Electrolytic  22µF   16V Digi-Key 493-1769-ND   $0.15            C10-C11 L/R L/R Amp Nichicon
Electrolytic 4.7µF   25V Digi-Key 493-1808-ND   $0.23  2  $0.46    C6 L/R    L/R Amp Nichicon
Electrolytic 470µF  6.3V Digi-Key 493-3014-ND   $1.15  2  $2.30    C3 L/R    L/R Amp Nichicon
Rectifiers      8A  400V Digi-Key GBU8G-BPMS-ND $1.60  3  $4.80  BR2,BR3,BR4   P/S   Micro Commercial
Fuse Holder              Digi-Key 283-2347-ND   $3.45  1  $3.45              Chassis Cooper/Bussmann
Vactrol                  Allied   980-0710      $2.94  1  $2.94  OC1-VTL5C3    P/S   PerkinElmer
                                               $48.23
BR2, BR3 and BR4 are the rectifiers. Because I used caps that were a little larger, it required me to replace the fuse holder with a more slender one. The Vactrol is the type of optocoupler that the original M-400 used (Light Dependent Resistor).
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
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Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer
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doctorpipe

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Joined: Fri Mar 06, 2009 1:27 am

Post Fri Mar 13, 2009 11:47 pm

Re: sick m400

Here is what happened to make the little cube sick. I have a system designed for three amps. So getting the tfm-35 caused a problem, (now there are four amps). You can't have a perfectly good amp and not use it! So I decided to bridge two cubes and let them run the subs. Sounds like a good idea. The subs are 8 ohms and there are two of them, left and right. It did some weird thumps and pops when I was checking the operation. Then the l.e.d.'s started freaking out, like I was melting the voice coils or something. It was not even pushing five watts at the time of this fault. I moved the cable and it hummed really loud! And tripped out again. I hooked it up to the pair of subs (one left and one right) as before and it worked but made commutator noise,but no pops or thumps, if you pushed it even a little. I found out the cable (even though it is a gold one) had a bad ground. When it was hooked to the left and right channels, the other cable took care of the ground. So by bridging the unit, it lost the ground and the input voltage went sky high. I found it killed the triac, so I put another in and replaced the opto-coupler, because I keep them on hand. With a minor adjustment, it is alive and well again. Both of the bridged amps have a separate ground wires now, for safety's sake. So if you decide to bridge an amp, consider a ground wire to save on future repairs. I am amazed that the amp is fine. Tough little bugger! So that is the scoop. Thanks for the parts list. I will be stocking up.
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TNRabbit

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(pair of) SILVER-7 TUBE AMPs

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Location: TN Native Languishing in VA

Post Sat Mar 14, 2009 5:49 am

Re: sick m400

Congratulations on resurrecting your amp, doc! =D> =D> =D> =D>
TNRabbit
Image

From FrankieD's lips to your ears: Sunfire - a quiet box of endless power.

Sunfire TG-IV/400~7 Amp
Carver SD/A-360 CDP
Benchmark DAC-1
Sony SACD/DVD-A
Active bi-amp: Ashly XR-1001 & 2 Rane PEQ-15s
Main: HotRodded AL-IIIs
Sub: Klipsch RT-12d
Center: Sunfire CRS-3c
Surround: Sunfire CRS-3 (x 2)

OconeeOrange wrote:"Gary likes to play it 'loud' as do I. His system begs you turn it up until you die"

RIP WIlliam B. Dibble, 1948-2012. I'll miss you my friend.
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puchalsk

Newbie 50+

Posts: 56

Joined: Sat Feb 21, 2009 10:37 am

Location: Ontario, Canada

Post Sat Mar 14, 2009 6:11 am

Re: sick m400

Great information! Will keep this in mind as I acquire another M400 for similar applicaiont.
M1.5T (2), M400, TFM-15, C-1,C4000, CT-6
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engtaz

User avatar

"TAZ"

Posts: 5229

Joined: Sat Jun 30, 2007 1:43 pm

Location: Tampa, FL

Post Sat Mar 14, 2009 7:35 am

Re: sick m400

Congrats on the fix.
engtaz


Carver M4.0T in front channels to Caver AL VI's in SACD & 2 Channel setup
C 16, PT 2400, Slim Device, Carver TX-8, 490T and Rega TT w Grado Gold cart in the 2 channel setup
Bogen SRB20 is computer amp
Carver PM-350 donated for youth church use
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OBI56

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SILVER-7 TUBE AMP

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Post Sat Mar 14, 2009 10:36 am

Re: sick m400

Stupid question doctorpipe; what kind of pipe does your handle refer to?
Why let facts or common sense get in the way of your opinions.
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doctorpipe

Newbie

Posts: 7

Joined: Fri Mar 06, 2009 1:27 am

Post Sat Mar 14, 2009 10:06 pm

Re: sick m400

The kind of pipes are exhaust pipes. I have lots of fun with that question. It is interesting what some people guess. It is because of a coanda cone (dynamic exhaust check valve) I built for a SCCA ITB car years ago. The name stuck. I am a Engine builder/developer, and sales and tech support for Audie Technology (Cam profiling equipment, Flow bench data aquisition, and engine simulation). So when I apply all of this, the engine gets developed on the computer, and optimized from there. That also means figuring the correct exhaust sizes and lengths. I also repair and modify German cars, and Jaguar v-12's. Nobody local understands them, so I do that too. So my hobby is the stereo and electronics. I repair a few amps/receivers a year for other people as a hobby. You can see my mug online at www.audietech.com. Sorry for being so long.
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OBI56

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SILVER-7 TUBE AMP

Posts: 4964

Joined: Sat Oct 20, 2007 12:52 am

Location: You ... OFF MY PLANET!

Post Sat Mar 14, 2009 10:51 pm

Re: sick m400

You are right about the weird questions the word pipe brings up doc! Reason I was asking is because I am a pipe smoker and a fellow pipe smoker who uses the nickname pipedoc is a Urologist!!! Pipes are also used in plumbing so there are several possibilities!
Why let facts or common sense get in the way of your opinions.
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doctorpipe

Newbie

Posts: 7

Joined: Fri Mar 06, 2009 1:27 am

Post Sat Mar 14, 2009 11:09 pm

Re: sick m400

Most people think it refers to smoking a Cheech and Chong pipe. My favorite, a woman wondered if I was in the porn industry and that was my stage name! Definitely not either of those!
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treitz3

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"Julian"
"Julian"

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Location: The tube lair in Charlotte, NC

Post Sat Mar 14, 2009 11:48 pm

Re: sick m400

Hehe, I hear ya'. Glad to see that you are back up and running and welcome to the forum.

TREX
In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence.

The best way to enjoy digital music reproduction is to never listen to a good analogue reproduction.

Robert R. - "Did you see my North Korea analogy? I should have named it Carversite.kim"

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