Mexicomike Posted August 21, 2007 Report Share Posted August 21, 2007 I had one of these in the late 60's (model AU). Actually I had three of them - AR replaced it twice (at no charge and they paid the shipping). The thing would get so hot you could almost light cigarettes off it. The first one actually DID catch fire. I sold it (the third one) about a year after I bought it. Hey, catching fire isn't just for "bargain" amps - 1In 1992 my Conrad Johnson CJ-5 preamp did the same thing. But CJ DIDN"T fix it for free OR pay the shipping. Since they (CJ) fixed it, it's been fine so far. But I digress...Anyway, I swore that my enthusiasm for old AR products would NEVER include their amp. I even specifically said that in an email to Roy just a few days ago.Well, to illustrate how some people never learn, yesterday I reversed my position and bought an old AR amp off ebay. I'll be picking that up in San Antonio next week as well as the 3a midrange Roy's sending there.I was looking on this site and although I found a few references to the amp, I didn't find very much. I realize this is a speaker forum but was wondering if anyone could point me specifically to the service manual for the amp or any site that might discuss it and how to keep it alive. Link to comment Share on other sites More sharing options...
RoyC Posted August 21, 2007 Report Share Posted August 21, 2007 Hi Mike,Up to about two months ago, Larry L. (aka "Vintage AR"), had a couple of them available. I know that he seeks them out for refurbishing and resale...probably worth contacting him.Roy Link to comment Share on other sites More sharing options...
Guest speedracer Posted August 21, 2007 Report Share Posted August 21, 2007 Hey Mike, Have you tried the guys @ "Audiokarma.org" or "stereomanuals.com" ? Good luck ! Martin Link to comment Share on other sites More sharing options...
JKent Posted August 21, 2007 Report Share Posted August 21, 2007 Manuals for lots of stuff, free, on this site. Original AR amp, tuner & receiver service manuals there. Also--you can upload to add to their database. Good resourcehttp://www.hifiengine.com/manuals.shtml Link to comment Share on other sites More sharing options...
Mexicomike Posted August 21, 2007 Author Report Share Posted August 21, 2007 I found/ordered the service manual from Vintage AR...Oh yeah...THEN I went to the sites mentioned and... downloaded it for free!I'm sure Larry can use the money!"Buy High, Sell Low" has always been my motto! Thanks Guys! Link to comment Share on other sites More sharing options...
onplane Posted August 22, 2007 Report Share Posted August 22, 2007 Mike, had you been a little more patient, you would have found the manual you seek is available on this site:http://www.classicspeakerpages.net/ar/elec...vice_Manual.zipSorry,JerryPS: always, always check this site first for AR literature. Link to comment Share on other sites More sharing options...
dynaco_dan Posted August 22, 2007 Report Share Posted August 22, 2007 Hi there;Not to knock the copy on our site library.I found a much better, as in cleaner and clearer copy, on the net, for free.Better the copy we have, than none, as I always say.The multi-part sheets I posted several years ago regarding the very detailed AR amp/receiver transistor bias servicing/replacement, is a very valuable item for the technical owner. Link to comment Share on other sites More sharing options...
Mexicomike Posted September 1, 2007 Author Report Share Posted September 1, 2007 OK,I have the AR amp - which looks nearly new. I also have a printed copy (from Larry) and an electronic copy of the service manual. HOWEVER, they are the same version - which is the later version stating that the bias pots are to be replaced with resistors. I don't want that version. My amp has bias pots and I DON"T want to change it. I want the original manual version which, I hope, explains adjusting the pots to come up with the required offset, etc.THere are 4 pots in the original amp but I don't know how/which to adjust to arrive at the proper offset voltage.I have a Moscode 600 which also has 4 pots - 2 bias and 2 offset - I assume the AR was the same setup. But without any info, I don't know which pot is which and what the appropriate settings are. The Moscode has the same problems - the pots can get dirty and the bias/offset goes to Hell. But I don't mind cleaning/adjusting the AR occasionally, as I do with the Moscode. Any Ideas where I can get the service manual for the original version of the AR amp, before they made the improvements? Or can anyone explain what to do?I have been on the audioKarma but can't find anything there. The amp works fine but I want to check set the bias/offset... Link to comment Share on other sites More sharing options...
Mexicomike Posted September 9, 2007 Author Report Share Posted September 9, 2007 Well, I've been all over the internet, from sites all over the world and I still cannot find any information on adjusting the Bias/offset of an AR Amp that has potentiometers. Plenty of copies of the service manual explaining how to perform the mod from pots to fixed resistors. BUT NOWHERE that I can find, is there any explanation of how to adjust the pots/where to check/what the figures should be. I realize that AR modified the amps to fixed resistors but before they did that, SOMEBODY at the factory and at service points had to be able to adjust these parameters and there had to be a service manual for that.I posted on Audio karma, including the circuit diagram but they weren't able to help. Anybody have any "last resort" ideas?ThanksNote - the amp is working OK - though it gets quite hot just like my old ones did. Unlike them, it doesn't shut down or catch fire! But I want to get it to spec and I DON'T want to perform the mod. Link to comment Share on other sites More sharing options...
dynaco_dan Posted September 9, 2007 Report Share Posted September 9, 2007 Hi there;They replaced the pots with fixed value resistors for a good reason.They drifted from specs with heat.Replacing or just bypassing the pots with resistors is a more stable and repeatable operating condition.Their only permanent solution in later production, both with the amps and receivers.Assume that most, if not all, AR factory blueprints and docuements were lost or destroyed many years ago.Look at the date of the service docs, they were printed many years after these changes.Why would they publish retroactive bad advice for customers? Link to comment Share on other sites More sharing options...
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