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So Happy I Found The Carver Site For My HR-742

Bill Cook
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Bill Cook

Bill Cook 9

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Greetings,

 

I am thrilled to have found out about this site. I am the original owner of a Carver HR 742 and absolutely love it. Carver products have always had an aesthetically pleasing design with great sound. The unit I have is in physical mint condition. There is not a scratch or finger print anywhere. The inside is also very clean.

 

I purchased the HR-742 in the early 90's, and now, some 25 - 30 years later, it requires some servicing. The amplifier sounds distorted, especially when bass notes are played. I have scoped the main filter caps, C812 and C813. There is 100 mV 120 Hz sawtooth ripple, and the capacitance measures under 7000 uF. The original rating is 8200uF. I do not have a tester to determine if the caps are leaky, but they seem to be indicating that they are leaky.

 

My questions:

Are there specific replacement caps, or can I order some audio grade caps from Digi key?

Are there any other known issues to deal with that can contribute to the distortion?

 

Thank you.

 

Bill Cook

Vancouver Canada

 

 

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Sk1Bum

Sk1Bum 9,865

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Hello Bill, and welcome to thecarversite.com. We're glad you're hear. ;) There is a lot of information here, much technical know how, and a pretty good bunch of folks that are happy to help.

 

I wish I could answer your questions regarding your HR 742, but I am no tech. I'm sure one of our techs will chime in here soon.


Once you get to Novice status, please consider uploading some pics of your gear in the Members Systems area. We all like pics of all kinds of audio gear.


In the meantime, kick your shoes off, turn up the music, and welcome aboard.

 

giphy.gif

 

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Bill Cook

Bill Cook 9

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Thanks for the welcome 

l will be happy to post pics once I receive my novice level

A little more background about myself. Back in the 90’s I was a factory inspector with Canadian Standards. I used to do factory inspections on the Carver products  at their facility in Lynwood WA. Always loved doing that call. Great bunch of people. Unfortunately I do not remember any names of the people I dealt with.

if there are any Carver employees that were at the Lynwood facility in the 90,s I will love to hear from you.

 

Cheers

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Balok

Balok 1,399

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Are the main PS caps 71V 8200uF?   If so, I have used ;

 

https://www.mouser.ca/ProductDetail/Nichicon/LKSH2822MESB?qs=Ysb%2FBSeDKl2fVpBbD5gyQw%3D%3D

 

for HR752 and CM1090 and HR895

 

I am no expert.  If your receiver is distorted all of the time now, I would put your scope at the output and see what it looks like.   Maybe put 1000 hz signal in.  I recently repaired a distorted NAD 3020.  The output sine wave was only distorted when I had an 8 ohm dummy load connected.  Turned out to be a bad output transistor.  I always do all of my testing through a dim bulb tester.

I am sure others can offer better advice.

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Bill Cook

Bill Cook 9

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Thanks for the response Balok, ATK.

 

Feeding a 1kHz signal is a great idea. Unfortunately I do not have a function generator, but am planning on buying one this month. As I am nearing retirement I am slowly building up my electronics lab for post retirement electronic fun activities.

 

I definitely will apply a 1kHz signal and trace the signal through the circuit. One concern I have is if the pre driver chip AN7062, Q717, is bad. It is an obsolete IC and I have not been able to find a known replacement for it. 

 

Yes the caps are 8200uF 56 volt. I just ordered two audio grade from Digi-Key. I am planning on going through the whole amp to upgrade as needed.

 

Cheers!

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Balok

Balok 1,399

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I use this online program for a tone generator and just run a 3.5 mm to RCA cable from computer to testing device.

 

https://www.szynalski.com/tone-generator/

 

 

I also found this article good for ideas of troubleshooting distortion;

 

https://sound-au.com/troubleshooting.htm#most3

 

Edited by Balok
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Daddyjt

Daddyjt 8,606

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I am not familiar with that receiver model #, but if it has relays, they are very likely a potential distortion cause. Relay failures usually manifest at lower volumes, and sometimes completely resolve when volume is increased, only to resurface next time the unit is powered on. 
 

oh, and welcome aboard!  Glad you found us!

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Dadvw

Dadvw 2,802

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Welcome aboard the Carver OCCD train, Bill!

You have a nice piece of original gear that needs some refurbishment to sound it’s best and last another 30 years. We have some good techs here, and some DIYers too! Keep us posted about your repairs and we like nudies too.......grin

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Rob

Rob 4,294

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Welcome to the site. It is a great place to be. Plenty of resources and rabbit holes to jump into.

Maybe just a little Tomfoolery. :D/

 

Enjoy! 

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