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Greetings - two M-1.5t

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johnfalc

Newbie

Posts: 4

Joined: Thu Aug 08, 2013 11:41 am

Post Thu Aug 08, 2013 12:01 pm

Greetings - two M-1.5t

I just bought two of the M-1.5t amps, one working, one not ... Looking forward to working to bring them up to snuff. Interested in others' experiences and any service bulletins beyond those in the Service Manual. John in NorCal.
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angelod307

SILVER-7 TUBE AMP

Posts: 2681

Joined: Sat Jun 06, 2009 10:56 pm

Location: manning, sc

Post Thu Aug 08, 2013 1:07 pm

Re: Greetings - two M-1.5t

Welcome. Talk to rolland at hitech , tom at vintage hifi or rita if she can be found as she was a head tech at carver then sunfire.
CarverFest: I just go for the arts and crafts
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kingman

User avatar

(pair of) SILVER-7 TUBE AMPs

Posts: 5596

Joined: Sun Nov 30, 2008 2:10 pm

Location: Upstate South Carolina

Post Thu Aug 08, 2013 3:48 pm

Re: Greetings - two M-1.5t

Welcome to the forum!!! =D> =D> =D>
In reality, it only matters what it sounds like to YOU!!!
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johnfalc

Newbie

Posts: 4

Joined: Thu Aug 08, 2013 11:41 am

Post Fri Aug 09, 2013 7:14 pm

Re: Greetings - two M-1.5t

Well I got the good one today and it is a dandy. I adjusted the supply voltage (it was a bit low) and the idling currents (they were both low too). I'm awaiting the arrival of a per-amp I'm matching to it before putting it into service, but at least now I know I've got a properly working unit to compare the dead one to.

Oh, BTW, someone already replaced the troublesome PS caps with a daughter-board arrangement and did a very neat job of it too. Ripple on all supplies is down in millivolts.

I do look forward to seeing how this works with my AR -90s.
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johnfalc

Newbie

Posts: 4

Joined: Thu Aug 08, 2013 11:41 am

Post Fri Aug 16, 2013 10:07 am

Re: Greetings - two M-1.5t

The first amp is all adjusted and now beautifully driving my AR-90s. Very enjoyable with plenty of clean power.

The second amp has arrived. Unlike the first one, this lived in a dirty environment in addition to not working! Anyway, I've (mostly) cleaned it up and done the diagnostics for repair. TRIAC and DIAC are good but the TO-92 NPN device that regulates current to OC-1 was shorted, the resistor between the regulator's NPN-PNP pair was burned, and OC-1 is out. I curve-traced a replacement pair of regulator transistors for a match and am awaiting an OC-1 which I've ordered. In the meantime I replaced the low/mid voltage electrolytics and checked all TO-3 devices ... all good so just awaiting the OC-1 for next steps in getting this one going.

So far I'm quite pleased with my foray into the Carver amp world.
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johnfalc

Newbie

Posts: 4

Joined: Thu Aug 08, 2013 11:41 am

Post Tue Aug 20, 2013 8:59 pm

Re: Greetings - two M-1.5t

I got the optoisolator today, and installed it. I also reviewed the various schematics for the M-1.5t and the PM-1.5 to track the revisions the factory made over time to the the LED drive of the optoisolator. Based on what I found I used the newest revision of 22 ohm in series and 750 ohm in shunt.

Brought it up on the Variac, checked voltages and current - all good. Brought it up to full line voltage, set the high rail to 122 Volts, let it stabilize for thirty minutes then set the bias. All is good. Checked voltage swing, indicator circuit, power delivery and distortion - looking great!

Now listening to the freshly repaired M-1.5t on my AR-90s ... Copeland, Strauss, Mozart, Knopfler, Krause, Clapton, etc ... all sound great.
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jjptkd

User avatar

SILVER-7 TUBE AMP

Posts: 2876

Joined: Wed Sep 22, 2010 4:50 pm

Location: Snohomish, WA

Post Tue Aug 20, 2013 9:17 pm

Re: Greetings - two M-1.5t

Congrats on the repair and welcome to the forum! =D> =D> The M-1.5 is one of my personal favorites in the Carver line up.
Sunfire TGP-III
Sunfire 225x5
PS Audio DL-III DAC
Klipsch KP 250 II (2 Pairs)
Klipsch RSW 15
(2) 18" Klipsch KP 480 Subs
Samson SX3200 (750x2 Sub Amp)
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BrianT

User avatar

Pair of Silver Sevens

Posts: 1361

Joined: Sat Oct 11, 2008 4:51 pm

Location: Ottawa, Canada

Post Wed Aug 21, 2013 6:45 pm

Re: Greetings - two M-1.5t

johnfalc wrote:I got the optoisolator today, and installed it. I also reviewed the various schematics for the M-1.5t and the PM-1.5 to track the revisions the factory made over time to the the LED drive of the optoisolator. Based on what I found I used the newest revision of 22 ohm in series and 750 ohm in shunt.

Brought it up on the Variac, checked voltages and current - all good. Brought it up to full line voltage, set the high rail to 122 Volts, let it stabilize for thirty minutes then set the bias. All is good. Checked voltage swing, indicator circuit, power delivery and distortion - looking great!

Now listening to the freshly repaired M-1.5t on my AR-90s ... Copeland, Strauss, Mozart, Knopfler, Krause, Clapton, etc ... all sound great.


Well done, I wish I could do that.

Welcome to the forum

Brian
VPI Classic Turntable (blk)
Transfiguration Phoenix Cartridge
Sunfire Vacuum Tube Control Centre. C/W Mod'ed Phono Stage
Carver Silver 7's Tube Amps
Raysonic CD-168 CDP (silver)
Carver TX11.
B&W 802D's Rosenut
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Chauss

User avatar

(pair of) SILVER-7t's

Posts: 2296

Joined: Tue Mar 22, 2011 4:35 pm

Location: In my own little world.....

Post Wed Aug 21, 2013 7:17 pm

Re: Greetings - two M-1.5t

Welcome! With your skills....you may make lot's of friends around here. 8)
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Good sound—like good music, good wine and good fellowship—is meant to be shared.
"The difference between genius and stupidity is that genius has its limits" Albert Einstein

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