Carver Reciever 900 left channel very low.

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homerjsimpson
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Carver Reciever 900 left channel very low.

Post by homerjsimpson » Tue Oct 21, 2008 11:10 pm

I have a Receiver 900 that when in stereo mode, the let channel is very weak. When in mono, it is fine. Checked the amp, and it is fine, the problem is in the preamp section.

Has anyone had this problem before?

Does anyone have a schematic?

TIA.

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homerjsimpson
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Re: Carver Reciever 900 left channel very low.

Post by homerjsimpson » Wed Oct 22, 2008 12:50 pm

OK, I think I may have found something. It appears thr R414 and R413 have been removed from the tone control board. Thing is I have no idea what value it is supposed to be.

Any 900 owners care to take a pic and post it?

TIA

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Robert R
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Re: Carver Reciever 900 left channel very low.

Post by Robert R » Wed Oct 22, 2008 1:21 pm

The question of why the hell someone would remove parts is still to be answered. Sometimes engineering changes are made, after production begins, and parts that are still designated on the board are omitted from the new circuitry. You problem may well lie elsewhere. A look at the soldering points on the bottom side should tell you if there ever were parts in those holes.

I've never seen a 900, but if parts are missing from one channel, there are equivalent parts on the other channel that you can learn from. Look for an R 314 and 313, or maybe 514 and 513. That's how they generally number the other channel. If they are shown there but are missing too, forget about that as a problem. If they are there, they will tell you the original values.

If at all in doubt, best to wait and see if someone comes up with the schematic, or can study another unit for you.

Robert R
"You know what folks? I'm happy."

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homerjsimpson
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Re: Carver Reciever 900 left channel very low.

Post by homerjsimpson » Wed Oct 22, 2008 6:45 pm

Robert R wrote:The question of why the hell someone would remove parts is still to be answered. Sometimes engineering changes are made, after production begins, and parts that are still designated on the board are omitted from the new circuitry. You problem may well lie elsewhere. A look at the soldering points on the bottom side should tell you if there ever were parts in those holes.

I've never seen a 900, but if parts are missing from one channel, there are equivalent parts on the other channel that you can learn from. Look for an R 314 and 313, or maybe 514 and 513. That's how they generally number the other channel. If they are shown there but are missing too, forget about that as a problem. If they are there, they will tell you the original values.

If at all in doubt, best to wait and see if someone comes up with the schematic, or can study another unit for you.

Robert R
I thought the same thing. I looked at the bottom of the circuit board, and indeed there are the leads to the missing resistors.

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Robert R
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Re: Carver Reciever 900 left channel very low.

Post by Robert R » Wed Oct 22, 2008 7:29 pm

I take it this unit is new to you, and has never had the one channel working since you got it. The tone controls are bypassable on the 900, I believe. If you can find the button that says "direct" or whatever, try that. It then doesn't matter what goes on in the tone control section.

While you're at, try all the buttons and switches (except power on/off) in and out several times, and the balance control especially, to check for oxidation or dirt. Have you tried more than one input? Or just the tuner section?

RobertR
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homerjsimpson
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Re: Carver Reciever 900 left channel very low.

Post by homerjsimpson » Fri Oct 24, 2008 8:47 am

I have cleaned all the switches. It is on all inputs and tape out and pre out...

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Robert R
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Re: Carver Reciever 900 left channel very low.

Post by Robert R » Fri Oct 24, 2008 8:59 am

Then I think were gonna need a schematic - HELP, somebody!

Receiver 900 service manual needed.
Robert R
"You know what folks? I'm happy."

RichP714
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Re: Carver Reciever 900 left channel very low.

Post by RichP714 » Fri Oct 24, 2008 11:57 am

Don't have one Robert, sorry ;(

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Robert R
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Re: Carver Reciever 900 left channel very low.

Post by Robert R » Fri Oct 24, 2008 8:16 pm

homerjsimpson,

I'm still hoping that somewhere in this forum somebody has a service manual for a Receiver 900 and will respond. Your best bet is probably to start a separate new post with a title like Member Needs RCVR 900 Svc Manual, or the like, with a simple plea for assistance. Try it under the Carver Discussion Forum, the first line: "Carver Home (Audio)". Then give it a few days and hope for something back besides sympathy.

If no book, I can still try and help you figure it out, but it's a lot slower way and more risk that we'll maybe make it worse. I'd need for you to get a digital camera and take some good shots to post here, close ups, where the parts can be seen and the board read.

RobertR
"You know what folks? I'm happy."

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homerjsimpson
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Re: Carver Reciever 900 left channel very low.

Post by homerjsimpson » Fri Oct 24, 2008 11:07 pm

As soon, as I get some batteries, I will post some pictures of the tone control board, with the two missing (robbed) resistors.

Thank you for the assistance.

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Robert R
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Re: Carver Reciever 900 left channel very low.

Post by Robert R » Sat Oct 25, 2008 5:26 am

homerjsimpson,

I've sent a message to a member who has an original 1985 Receiver 900 that he bought new, requesting manual if he has it, or would he look inside and assist us. Hope to hear back today.

Robert R
"You know what folks? I'm happy."

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engtaz
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Re: Carver Reciever 900 left channel very low.

Post by engtaz » Sat Oct 25, 2008 7:48 am

Take a pic to show the area. I can look in mine.
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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Robert R
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Re: Carver Reciever 900 left channel very low.

Post by Robert R » Sat Oct 25, 2008 9:02 am

homerjsimpson,

All possibilities known to me for obtaining service data on your unit are in the works. Best chance is from California, and it's too early AM there to expect much yet.

The important question that you need to answer is, Have you ever seen this unit working properly since you've had it? If yes, then the missing parts, while interesting, cannot be the main problem, unless you cut them out yourself while sleepwalking.

RobertR
"You know what folks? I'm happy."

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homerjsimpson
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Re: Carver Reciever 900 left channel very low.

Post by homerjsimpson » Sat Oct 25, 2008 10:50 pm

This unit came to me in the state it is now.

I have a 100, but the tone control board is totally different.

Thanx for all the help guys.

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Robert R
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Re: Carver Reciever 900 left channel very low.

Post by Robert R » Sun Oct 26, 2008 7:15 am

homerj,

Thanks for the clarification regarding your patient's history. Hopefully you have just one problem. But we may still find that the resistors were removed just to reshape the tone control circuitry in some way, and don't have anything to do with one channel's being knocked out.

I'm looking forward to solving this problem. I have trouble dealing with the idea that anybody would cannibalize any Carver unit. Did the guy have horns, a tail, and no shadow?

My problem is a complication of OCCD that hasn't been named yet. It's most consistent symptom is a compulsion to preserve every unit that Carver ever made, happily ever after. There's no cure, of course.

RobetR
"You know what folks? I'm happy."

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