Film-Tech Forum ARCHIVE: Kelmar amp repair anyone?

This is topic Kelmar amp repair anyone? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=008551

Posted by Eric Robinson (Member # 2966) on 03-06-2007, 01:23 AM:

I have the following amps which I would like to have repaired. Does anyone know who or where I could send them to?

And...hopefully I'm not posting in the wrong forum. Tell me if I am and I'll move this somewhere else.

Quantity 1 - Kelmar - Model AA-7700 Serial 521 - 50 watt amplifier
Quantity 1 - Kelmar - Model AA-7700 Serial 522 - 50 watt amplifier
Quantity 1 - Kelmar - Model AA-7700 Serial 523 - 50 watt amplifier
Quantity 1 - Kelmar - Model AA-1200 Serial 922 - 120 plus

Thanks...ERIC

Posted by Mark Gulbrandsen (Member # 72) on 03-06-2007, 07:24 AM:

To Kelmar... or we can also do it. I carry a rebuild kit in the van. I will also say that replacing all the electrolytics will restore 90% of them to good working order.

Mark

Posted by Louis Bornwasser (Member # 3063) on 03-06-2007, 08:09 AM:

We also do this work. Kelmar apparently will no longer repair the 26 watt module...but we will. Louis at Hadden.

Posted by Marin Zorica (Member # 1716) on 03-06-2007, 11:42 AM:

This repair stuff gives me think about....where to use 25W or 50W amp?

Posted by Steve Guttag (Member # 268) on 03-06-2007, 02:46 PM:

We have been known to repair them too (even with the Christie badge). The reason replacing the electrolytics often fixes the problem is that I've found them incorrectly installed and reverse biased. That is, when they use them as blocking caps, they have the polarity wrong for the circuit...which kills the cap. Of course, they could have chosen a better type of cap for this purpose than electrolytics.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 03-06-2007, 03:01 PM:

Steve,
These amps are not really good enough quality to justify good mylar or film coupling caps... class B output stages and some used darlington O.P. devices, very old stuff but reliable. I normally use non polorized caps for the input stage positions though. in these amps it is usually justnthe input caps that fail fomr what Steve mentions.... but replace them all! Also use good quality electrolytics rated at 105 deg C. and they will last the rest of the time you will be using these amps.

Mark

Posted by Steve Guttag (Member # 268) on 03-06-2007, 04:45 PM:

I was mainly referring to using the better caps for the input stages to have avoided the failures rather than any dramatic sonic improvement.

Then again...why is anyone running mono nowadays.

Posted by Mark Gulbrandsen (Member # 72) on 03-06-2007, 04:51 PM:

quote: Steve Guttag
Then again...why is anyone running mono nowadays.

They are all Woody Allen fans......

Posted by Steve Guttag (Member # 268) on 03-06-2007, 05:55 PM:

Yeah, but even Woody uses Dolby Digital Mono!

Posted by Eric Robinson (Member # 2966) on 03-07-2007, 05:18 PM:

Hi Mark,

If I did send these amps to your company, might you be able to give me an average repair cost? I will need this to provide to the higher ups. These are typical units, no visible signs or olfactory suggestions of burning components.

Posted by Gordon McLeod (Member # 33) on 03-07-2007, 05:33 PM:

i question if with shipping cost and labour if it is not more prudent to replace these with better more modern amplifiers

Posted by Mark Gulbrandsen (Member # 72) on 03-08-2007, 07:20 AM:

Eric, If the semiconductors are not blown in them then 1.5 hours plus parts. I sonewhat agree with Gord though... a more modern replacement is in order for them. Take a look at the least expensive QSC line available through music stores. They are VERY inexpensive and very reliable.

Mark

Posted by Steve Guttag (Member # 268) on 03-08-2007, 09:04 AM:

However, you will probably find that repairing them is the least expensive route and if you get a straight amplifier, you will still need a preamp and configure the other channel for a monitor amp.

Posted by Louis Bornwasser (Member # 3063) on 03-08-2007, 02:49 PM:

We "take 'em home" and ups them back. This allows a 24 hour burn in with pink noise on the bench. Really not a bad amplifier for what it needs to do and for its times. Louis