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M-500 Refurb.

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RichP714

SILVER-7t

Posts: 1814

Joined: Fri Oct 12, 2007 2:12 pm

Post Mon May 12, 2008 10:11 am

Re: M-500 Refurb.

bob p wrote:Marshmallows? Please do tell.

If you've got the marshmallows, I could use a PM-1.5 and an under-sized power resistor to boil some water for hot chocolate...
I can't vouch for it; I've only read about it, but always wanted to try it.

The oven works by creating a standing wave inside the oven. I believe the frequency is about optimum to excite water molecules, and the friction as they move causes the heating (another story, but the hershey bar in the pocket of a guy on a flightline standing in front of a jet fighter's radome is pretty cool, but probably fabricated ((at some flightline's they have to drink a qt of water every 20 min to stay hydrated; I doubt his hershey bar would have survuved, but anyway)))

So you take the tray out, so it doesn't rotate, and put a plate of marshmallows in. 'Nuke' it until they just start to melt, and measure the distance between the melted pits. On average (or more likely rms?) they should equal the half wavelength of the mocrowave frequency printed on the back.

Every time I remember this, I don't have any marshmallows around to actually try it.

[edit: I just looked this up, and evidently you're calculating the speed of light (3.0 X 10^8 m/sec, so if velocity=wavelength X frequency, you take the frequency printed on the back (it says usually 2450MHz) and multiply by twice the distance measured (the half wavelength) in meters and you should get close to the speed of light.]
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BillD

User avatar

(pair of) SILVER-7 TUBE AMPs

Posts: 7295

Joined: Wed Jun 06, 2007 8:29 pm

Location: The west's most mid-western town, Scottsdale, Arizona

Post Thu Jun 12, 2008 10:11 pm

Re: M-500 Refurb.

The saga continues. I had taken my problem off-line and worked with RichP with advice from bob p and jvandyke_tx on how to proceed. My amp would run beautifully until it blew a fuse. The transformer would get way hot and blowing a fuse meant that it was pulling more than a sustained 10 amps. On voltage checking, the high rail would climb from its normal 74v to over a 100v. I really don't know how high it got when it blew the fuse (and I don't want to). I'd just shut it down when it hit 100v and wait to do more testing until it cooled down. So, we knew it was heat related and the feedback to limit triac firing wasn't working. After much noodling about exactly how the amp worked, the problem had to be between the optocoupler and the triac. Fortunately, it was the first - the optocoupler, as verified by a good shot of freeze spray.
Opto.JPG
Opto.JPG (151.06 KiB) Viewed 1103 times
PC713 is the offending part. It's an 84¢ part available HERE

I'm waiting for delivery. I'm going to put a socket on the board to make soldering easier. I'll let y'all know how this turns out.

Next up - new binding posts.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
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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Mr. M-500t

(pair of) SILVER-7 TUBE AMPs

Posts: 6211

Joined: Fri Mar 17, 2006 10:00 pm

Post Thu Jun 12, 2008 11:40 pm

Re: M-500 Refurb.

Man am I loving all of the M-500 techs we're gaining around here ! =D>
Good deal BillD. Hope you get that baby back in service. :D
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bob p

User avatar

SILVER-7t

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Joined: Wed Jul 18, 2007 10:40 pm

Location: Chicago

Post Tue Jun 17, 2008 1:11 am

Re: M-500 Refurb.

OMG -- this has to be the first time that a Carver guy has tried to fix his amp with a spray can ... and it worked!!!

Congrats, Bill!
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.
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engtaz

User avatar

"TAZ"

Posts: 5193

Joined: Sat Jun 30, 2007 1:43 pm

Location: Tampa, FL

Post Tue Jun 17, 2008 4:33 am

Re: M-500 Refurb.

The optocoupler's are known to be a week link in electronic. That and crystal oscillators. Congrats on the troubleshooting.

engtaz
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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BillD

User avatar

(pair of) SILVER-7 TUBE AMPs

Posts: 7295

Joined: Wed Jun 06, 2007 8:29 pm

Location: The west's most mid-western town, Scottsdale, Arizona

Post Thu Jun 26, 2008 1:49 pm

Re: M-500 Refurb.

The saga continues, but may be complete. Only time will tell. I replaced the opto by installing a chip carrier socket.
New M-500 Opto.JPG
New M-500 Opto.JPG (192.2 KiB) Viewed 985 times
As jvandyke_texas told me, he didn't think the opto was at fault, and he was right. After testing the opto was no longer thermosensitive, but the rail voltage was continuing to go up. I figured it had to be a nearby part in the triac firing circuit, so I started trying adjacent parts. If you see the part that is below and just to the left the opto (directly left of the trimmer - not the resistor, stupid), that's the offending part - a bridge rectifier. It was a DBA-10C (1A, 200v), which I couldn't find, so I had to substitute a NTE167 (2A, 200v). I've run the amp for about 5 hours continuously at a shot with no apparent rail voltage drift.

While I was in there, I took RichP714's advice and replaced the binding posts with THESE. Unfortunately, they were too long and ran into the transformer housing. So I had to cut two of them off and attach th wires with these.
M-500 Solder Lug Washer.JPG
M-500 Solder Lug Washer.JPG (315.61 KiB) Viewed 985 times
The resulting installation looks like this (it doesn't touch - honest).
M-500 Binding Posts.JPG
M-500 Binding Posts.JPG (144.02 KiB) Viewed 983 times
Anyway, it's all done. Here's what those posts look like from the back.
M-500 Posts.JPG
M-500 Posts.JPG (161.67 KiB) Viewed 982 times
That's all for now!
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
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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engtaz

User avatar

"TAZ"

Posts: 5193

Joined: Sat Jun 30, 2007 1:43 pm

Location: Tampa, FL

Post Thu Jun 26, 2008 7:05 pm

Re: M-500 Refurb.

Very nice binding post. You da Man. =D> =D> =D> =D>
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
<<

BillD

User avatar

(pair of) SILVER-7 TUBE AMPs

Posts: 7295

Joined: Wed Jun 06, 2007 8:29 pm

Location: The west's most mid-western town, Scottsdale, Arizona

Post Tue Jun 02, 2009 4:46 pm

Re: M-500 Refurb.

Months later, I got around to doing something I should have done while I was in there — Blue LED lamps. The current lamps in there are incandescent and run off a little transformer that can barely put out 700ma (the bulbs are 800 ma). The transformer has two taps, 6v and 8v. For LEDs, you need DC, so after some discussion with RichP and Ruskall, I came up with the following circuit.
M-500 LED 2.jpg
M-500 LED 2.jpg (32.64 KiB) Viewed 827 times

It works by rectifying the 8v tap from the transformer and delivering it through the 3R6 resistors to the lamps. When you want it bright, it drops in a set of 3R6 resistors in parallel to halve the resistance (and therefore double the current — supposedly, more later).

So I built a little board with the components on it (except the transformer and the lights). They didn't have 3R6 resistors at Fry's electronics, so I got a pair of 3R3s and a pair of 3R9s. The 3R3s are in-circuit all the time, and the 3R9s are dropped in for brightness.
M-500 Lamp Board.JPG
M-500 Lamp Board.JPG (96.31 KiB) Viewed 826 times


Underneath it's wired like so.
M-500 LED Circuit.jpg
M-500 LED Circuit.jpg (23.97 KiB) Viewed 824 times


There is really only one spot in the M-500 where this can fit, and it's over the power supply next to the barrier between it and the amplifier board.
M-500 LED lamp board.JPG
M-500 LED lamp board.JPG (330.18 KiB) Viewed 825 times

And that's all there is to it. Some rewiring of the switch and the lamp board was all that was necessary.

Of course, things don't always go perfectly. I found that dim is bright enough, and bright makes hardly any difference. It seems that wimpy transformer is maxed out, current wise, with the 3R3 resistors in line, and lowering the resistance just makes the voltage sag so you don't get anymore current to the LEDs.

Anyway, here's what it looks like now.
Family Room System.JPG
Family Room System.JPG (46.12 KiB) Viewed 825 times


I'm building another little board with 6R6 resistors on it to replace the one in there now, so the dimming will work better. When I'm in there, I'll adjust the lights as one is a little low and has some "shine through".
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
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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bob p

User avatar

SILVER-7t

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Joined: Wed Jul 18, 2007 10:40 pm

Location: Chicago

Post Wed Jun 03, 2009 12:39 pm

Re: M-500 Refurb.

bill, did you use the 1W or the 2W luxeons?
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.
<<

engtaz

User avatar

"TAZ"

Posts: 5193

Joined: Sat Jun 30, 2007 1:43 pm

Location: Tampa, FL

Post Wed Jun 03, 2009 2:45 pm

Re: M-500 Refurb.

Those blue bulbs are gorgeous.
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
<<

BillD

User avatar

(pair of) SILVER-7 TUBE AMPs

Posts: 7295

Joined: Wed Jun 06, 2007 8:29 pm

Location: The west's most mid-western town, Scottsdale, Arizona

Post Wed Jun 03, 2009 8:20 pm

Re: M-500 Refurb.

I used a pair of THESE in series for each bulb. So, the bulbs are approximately 2½ Watts apiece.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
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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madmike46

Newbie 50+

Posts: 78

Joined: Sat Jul 04, 2009 8:31 pm

Location: Saskatchewan, Canada

Post Fri Aug 28, 2009 6:55 pm

Re: M-500 Refurb.

I have been reading the post with great interest. I have an M500t that I bought new in 1986 and I have never had a problem with it yet. I was wondering if it would be wise to replace the Caps in this unit before it gives me any problems. Also are there any other parts that one should replace while I'm in there. Thanks in advance for any info you guys can give me.
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BillD

User avatar

(pair of) SILVER-7 TUBE AMPs

Posts: 7295

Joined: Wed Jun 06, 2007 8:29 pm

Location: The west's most mid-western town, Scottsdale, Arizona

Post Fri Aug 28, 2009 7:25 pm

Re: M-500 Refurb.

The only true consumables in amplifiers are electrolytic caps. Heat takes its toll on lots of things, but 'lytics wear out (dry up) whether or not they are in use. If you keep an amp within its operating parameters, the other components should last a lifetime, and maybe a few generations. The things I've seen fail (diodes and diode devices, like rectifiers) were probably overheating do to failing caps. Of course, any component could be badly made and fail. But as far as wholesale replacement, I can't think of anything other than electrolytics.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
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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madmike46

Newbie 50+

Posts: 78

Joined: Sat Jul 04, 2009 8:31 pm

Location: Saskatchewan, Canada

Post Fri Aug 28, 2009 9:27 pm

Re: M-500 Refurb.

Thanks for the reply BillD. Would recomend I either do this myself or get it done before I start having problems?
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BillD

User avatar

(pair of) SILVER-7 TUBE AMPs

Posts: 7295

Joined: Wed Jun 06, 2007 8:29 pm

Location: The west's most mid-western town, Scottsdale, Arizona

Post Sat Aug 29, 2009 8:39 am

Re: M-500 Refurb.

If nothing has ever been done to it before, it's time. Your skill will dictate how.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
_________________
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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