Opinions or inputs on Altec 1570B amplifiers

[Original Burnedfingers]

http://www.audioasylum.com/forums/vi...ages/4477.html


This is an excellent article on the 1570's and modifications that have been reviewed by Joe Rosen in Oct of 2001

I am trying to get some ideas for re doing the bias circuit. I have some feelers out as I am trying to locate two of these amps with the 16492 output transformers in them. I had several of them about 15yrs ago and like a fool let them go.

Anyone have any ideas?

[Original Burnedfingers]

http://www.triodeel.com/al1570b.gif

copy of schematic

[Wavebourn]

Silly article (sorry Joe) describes some good ideas found in the article he criticizes.

[Mark A. Gulbrandsen]

I used to repair alot of these amps as they were used in many Movie Drive Ins. Almost all of them eventually experienced either power transformer failure or output tranny failure. Since the power supply is quite high voltage on them BE SURE YOU GROUND THE CHASSIS VERY WELL AND EXCERCISE EXTREME CAUTION and be sure you have the proper size fuse in place!!Almost all of these amps that were used in the Drive Ins ended up in the garbage dump. This Altec was a cheaper way to powering all the ramps at a Drive in... there was always a main amp and a backup amp and for good reasons. Better drsigned Drive Ins used multiple small tube amps and there was a single backup amp that could be switched into any ramp in case one went down. All in all they are a fire hazard in my opinion.

MArk

[Original Burnedfingers]

Silly article (sorry Joe) describes some good ideas found in the article he criticizes.

Silly as it may seem it is still some type of information and it seems it is all I can find on the 1570's. I would be more interested in your positive input and comments as a result of your vast experience. Anything you would care to share would be most appreciated.

I used to repair alot of these amps as they were used in many Movie Drive Ins. Almost all of them eventually experienced either power transformer failure or output tranny failure. Since the power supply is quite high voltage on them BE SURE YOU GROUND THE CHASSIS VERY WELL AND EXCERCISE EXTREME CAUTION and be sure you have the proper size fuse in place!!Almost all of these amps that were used in the Drive Ins ended up in the garbage dump. This Altec was a cheaper way to powering all the ramps at a Drive in... there was always a main amp and a backup amp and for good reasons. Better designed Drive Ins used multiple small tube amps and there was a single backup amp that could be switched into any ramp in case one went down. All in all they are a fire hazard in my opinion.

Well I guess different people in different areas of the country do things quite differently. We never used 1570 for drive in theatre amps around here.

Its amazing to note that there are still a number of 1570's in service in large facilities like football stadiums and convention centers. Within the last several years the company I work for did a large new system and replaced 20 some 1570's that had given excellent service and were still functional and had lived their life without incident. I guess there is a lot to be said about the quality of any installation and maybe that was the problem with the drive in theatres in your area.

Heck, if you have some ideas on the 1570 please do share them as I'm sure others would be as interested as I am to hear them.

[Original Burnedfingers]

Seems to be a lack of interest in this animal. Do I give up the idea?

[kevinkr]

Hi burnedfingers,
I wouldn't give up on the idea. I haven't seen too many of these used in drive ins either. It's been a number of years since I last saw or worked on one.

I always understood them to be quite reliable, and the ones I rebuilt needed very little work to get them going again. Not really sure where Wavebourn is going with this one..

I have worked on at least a dozen of them over the last 15yrs or so, and I have not seen one with a bad power transformer or output transformer.

Unfortunately in this neck of woods they now command pretty princely sums of money. I have seen functional pairs of 1570B selling for well over $2K in the last year or so.

They sound pretty nice when not overtaxed on the low end..

[Original Burnedfingers]

Kevin,

Thanks for the reply. Do you have any ideas for the bias section?

[kevinkr]

My service information is buried beyond quick rediscovery, any chance you could post a schematic or link to one?

IIRC The main issue with these amps was the input transformer and how to get around it..

[tomtt]

strangely, 12th down, under power amplifier


http://www.altecpro.com/products/vintage/index.htm



1570B Power Amplifier Manual ZIP


scema-


http://images.google.com/images?svnu...f&q=altec+1570


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