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HELP trouble shooting my AR Integrated amp


Guest hifi13

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Guest hifi13
This may be a little far-fetched but it won't cost anything. Coincidentally, MY AR amp lost the right channel. Since it had been profesionally serviced within the past year I took it back and had it checked out. Turned out the slide switch on the left side of the front panel, marked "Normal/Monitor" was cruddy. The tech sprayed it, but when I first tried it at home again--same thing. No right channel. Try moving that slide switch back & forth several times to scrape any oxidation off.

Like I said--far fetched, but worth a try.

Good luck

Kent

Well that sort of thing I can give a try before seeking out a professional. Can't hurt right? Thanks again to everyone for the help and suggestions. I will keep you all posted as to how it goes.

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I suggest spraying all switches and controls with De-oxit, and working them,

as Kent and others pointed out here.

I also strongly suggest that you replace all electrolytic caps.

If still not working:

Don't recall can you isolate the pre and power amp sections? Are there jacks

on the back? You'd want to determine if the problem is the pre or power amp.

Measure voltages at B-E-C on all transistors in the faulty sections, report them

here. Measure the DC voltage at the speaker terminals, should be mV range.

These should all be with respect to ground.

Measure the voltage across (not with respect to ground) all of the output device

5W emitter resistors.

Measure Right and Left channels so that the good channel can provide a reference

for the correct voltages.

These should all be done without a speaker load.

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1 My AR AMP has the standard 3 A fast-blow fuses in the outputs.

2 Re the tape monitor switch - the AR Service manual states the switch needs to be cleaned any time the amp is serviced so obviously it was/is a frequent contributor to missing or poor sound due to dirt/corrosion on the contacts. With luck, it might be the source of your channel difficulty!

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1 My AR AMP has the standard 3 A fast-blow fuses in the outputs.

2 Re the tape monitor switch - the AR Service manual states the switch needs to be cleaned any time the amp is serviced so obviously it was/is a frequent contributor to missing or poor sound due to dirt/corrosion on the contacts. With luck, it might be the source of your channel difficulty!

Hi there;

Heathkit/AR used a 3 amp fast blow fuse for their Heath AS-103/AS-103A speaker kits.

These were the equivalent of the AR-3A speaker system.

This is also the only FAST blow fuse rating I have come across for any AR speaker system.

As you may know, AR recommended and supplied, at cost, only Bussmann FNM slow blow fuses, in this case, FNM 1 1/4 amp rating fuses.

Littlefuse makes or at least made the equivalent FLM series.

The AR amplifier was shipped from the factory with 3 amp fast blow fuses to protect the amplifier output, not to protect any particular speaker system.

Each time you have blown a 3 amp fuse, you are up to the top, if not over the top, of this speakers power handling capacity.

Considering the age of our drivers and their scarcety, I would suggest perhaps reducing to 2 1/2 amp or lower fast blow fuses.

Another option is to stay with the amplifiers 3 amp fast blow and add 1 1/4, or better yet, 1 amp FNM/FLM fuse inline as well.

Reading the switch comment above, it would appear that a slight shot of DeOxit, or equal, may be the answer, thank you, Kent.

Only on this switch for now and only slightly.

Many years ago a friend loaned me his Dynaco 400 basic amplifier.

When I connected it up, one channel was dead.

I did the usual fiddle and diddle but to no ends.

I hauled it back, 50 pounds plus, and he took it to his shop.

A little troubleshooting and he found that with lack of use the one volume control was not clean.

A little shot of DeOxit and a few more turns and viola, it worked again.

I remember a older auto mechanic telling me once about a vehicle that was towed into his shop with a lot of miscellaneous parts in the trunk.

The do-it-yourselfer tried to fix the problem, now the mechanic had to figure out what to fix, as he now had only a partially assembled dead vehicle.

In my own heating business I saw more than once a pile of used parts beside a boiler, nothing to do with what I knew was the problem.

Another time, a helpful neighbour changed out several hundred dollars in boiler parts and after paying him, she finally called me to repair it.

Good luck.

Vern

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Dan,

If you are anywhere near NYC/northern NJ I can highly recommend Bristol Electronics in Ho-Ho-Kus NJ. That amp is heavy, so shipping could be expensive. But even if you have to ship it, Tim does a great job and he is conservative--he won't replace a bunch of parts unneccessarily. He fixed one of my AR amps, and told me the other was beyond repair. He has also repaired MANY components for me, including KLH 8, 13, 16, 18 & 27; Scott 350C, Sherwood S3300, probably some other stuff too.

Good luck

Kent

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Guest hifi13

Once again thanks for all the tips guys. My wife and I are going out of town for the night and I am going to borrow a multi-tester from my uncle and grab some de oxit while we are out. Once I give everything a good cleaning tomorrow I will report back and let you know my results. Cheers and have a good weekend guys!

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Guest hifi13

Hi all. Just thought I would post an update as to the status of the amp. Went out bought some de-oxit and a multi-meter. I sprayed all the pots and the switch, rotated each one about 20 times, I checked the dc at the speaker terminals and the readings are as follows: left channel - .355 mV, right channel - .025mV. So there is and obvious difference between the two channels. After I sprayed the post I hooked up the amp to see if it made any difference and I noted a bit more in the right channel than I had previously heard, still distorted but seemed to be a bit more volume there. Hmmmm, so perhaps the pot cleaning did a bit of good, not enough to remedy the problem.

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The resistors that replaced the original bias pots control the offset (dc voltage at the terminals). Though your readings are not very good, they are much better than mine were with the original pots before I cleaned them with copious amounts of cleaner. As I recall, before cleaning I had one channel at around 100mv and the other in the 700mv range. After cleaning I got them fairly close but they would still drift a lot in operation. With the new pots, I got the channels adjusted so that they both hold about 10mv when the amp is warmed up.

However, the huge difference I had in offset did not affect the volume in the two channels - in other words, the volume level was more or less equal in both channels. But the sound quality was different. So I don't think the offset itself is causing your volume problem. BUT, I am not a circuit expert so I am just basing it on what my amplifier did.

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  • 11 months later...
Guest VINTAGE-AR
So I guess my next question is where do I go from here? Should I start with a multi-tester and see what is possibly not working within the circuit? Where would be the best place to start? Perhaps the driver board like Larry suggested? Sorry for my inexperience in these matters. Once again I really appreciate everyones help.

While searching the site for another item, I see you are still working on this issue. I'm afraid that a multi-tester is not going to be of much use to you. You really need an oscilloscope to chase this one down. There are likely three areas to look into, the Tone Control Board, The Amplifier Driver Board and the large dual capacitor coupling to the output transformer.

Without more data, it's impossible to tell where the problem lies. I would have technician step through the circuits, comparing one channel to the other with a fixed signwave input.

Good luck and if you get stuck, send it to us.

Larry (VINTAGE-AR)

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In any case, if you can get all the volume you need with peaks handled by, say, an amp that puts out only 50 WPC over the audible spectrum, then there is nothing to be gained at all by obtaining an amp that puts out 100, 200, or even 500 WPC. While some might think that more power than what the AR amp could put out would be a good idea, it seems inconceivable that AR, a company that in its old days form many of us still consider the height of audio rationality, would design and build an amplifier that was not powerful enough to do their speaker models justice. Incidentally, I believe that the AR amp was designed by Robert Grodinsky, who was hired by Roy Allison to do the job. Robert went on later to found RG, a company that came up with some interesting products of its own.

Incidentally, the AR Receiver that I owned years ago powered my own AR-3a systems plenty loud in a room of about 2000 cubic feet. At about that same time Consumer Reports magazine did a review of audio receivers and they rated the AR Receiver at 97 WPC into four ohms. That ought to be enough for just about anybody.

Howard Ferstler

I completely agree with Howard on the AR Amplifier: it has more than enough power for powering any AR speaker -- or most other speakers for that matter. It is particularly good into 4 ohms, but the amp should be provided with plenty of ventilation. I took my AR amp to a McIntosh amplifier clinic some years back, and the amp exceeded the McIntosh specs by an easy margin (with the maximum 4-ohm power tested at 100 watts/ch), but the clinic would only run an actual curve at the rated 8-ohm output because it was the "rated" power.

The dc-offset voltage on any AR amp should be checked regularly to make sure that the bias is kept in check. This was a chronic problem with the old units, but there was a fix somewhere along the line that prevented trouble. In any event, always keep the 3-amp output fuses in their fuse-holders to protect speakers from the catastropic damage that can occur with full rail dc voltage across the output. Those speaker fuses are not to protect the speaker against amp clipping; they are there to prevent large dc offset voltage from damaging a speaker. This full rail voltage will fry any woofer voice coil.

--Tom Tyson

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I just posted two PDF copies of different articles on loudspeaker power needs and requirements that Roy Allison (who was instrumental in the design work of the AR-3a and designed the AR-LST and several other AR models) published in Sterero Review magazine, first in 1973 and later in 1980. They are in the "Library Additions and Corrections" section on this site.

Roy certainly would be aware of how much power is required to make a pair of AR speakers come to life.

In Villchur's and Allison's time, AR advised fusing their speakers if they were used "in a discotechque application in which the demands for overall volume levels far exceed normal home listening." For many of today's users, "discotheque application demands" ARE their normal home listening. A visit to the home of most anyone under the age of 50 or so who has invested a substantial amount in an audio system will illustrate this.

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....anyone under the age of 50 or so who has invested a substantial amount in an audio system....

I want to meet that person. A rare bird, indeed. Everything these days is "home theater" or "whole house audio." Certainly it is quite difficult to find anyone under 40 who ever sits down and listens, uninterrupted, to 2-channel music in a critical, all-consuming, leave-me-alone-for-two-hours manner anymore.

Virtually the entire realm of 2-channel audio and quality components are old guys like us, reliving and restoring the equipment and glory days of yesteryear. I love it, and I love discussing it and even arguing over it. But it's not a viable, current commercial market anymore, that's for sure. The magazines are all gone. Stereophile is down from 320 pages per issue as late as the '90's to under 100 pages now. The specialty retailers are virtually all gone. The main discussion between iPod owners is 'How many songs do you have,' not the quality of the reproduction. Sad.

Steve F.

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I want to meet that person. A rare bird, indeed. Everything these days is "home theater" or "whole house audio." Certainly it is quite difficult to find anyone under 40 who ever sits down and listens, uninterrupted, to 2-channel music in a critical, all-consuming, leave-me-alone-for-two-hours manner anymore.

If you read the forums over at Audio Karma, there seem to be quite a few people from the CD generation who are discovering vintage 2-channel. And from the number of them who post questions about amplifier clipping and blown tweeters in multiple brands of vintage speakers (not just AR), most of them seem to want to play their systems way louder than we ever did.

BTW, I was including "home theater" users in my previous posts, as they more than any others often don't seem to realize that their systems have volume settings below "ear splitting."

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..... quite a few people from the CD generation......

"Quite a few" is a relative term. It still doesn't amount to a substantial market that influences the production and employment of the various companies to any truly significant extent. The dearth of audio-only magazines and specialty hi-fi stores speaks for itself. The fact that the major electronics manufacturers (Pioneer, Yamaha, Onkyo, etc.) have virtually no 2-channel equipment in their product line-ups indicates that they don't see any meaningful commercial viability to the U.S. 2-channel market. Europe and Asia are somewhat different, but there is no significant 2-channel business in the U.S.

Is there a fringe 2-channel market in the U.S.? Yes, I guess there is, but that's all it is.

BTW, the current music-listening generation is not the CD generation. That went away for good 5 years ago. The current music-listening generation is the download generation.

Steve F.

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"Quite a few" is a relative term. It still doesn't amount to a substantial market that influences the production and employment of the various companies to any truly significant extent. The dearth of audio-only magazines and specialty hi-fi stores speaks for itself. The fact that the major electronics manufacturers (Pioneer, Yamaha, Onkyo, etc.) have virtually no 2-channel equipment in their product line-ups indicates that they don't see any meaningful commercial viability to the U.S. 2-channel market. Europe and Asia are somewhat different, but there is no significant 2-channel business in the U.S.

Is there a fringe 2-channel market in the U.S.? Yes, I guess there is, but that's all it is.

BTW, the current music-listening generation is not the CD generation. That went away for good 5 years ago. The current music-listening generation is the download generation.

Where did I say that any of these people represented any significant market share, or that they were the current generation? All I said was that the are the folks who blow out speakers because they have no idea how to properly use vintage audio gear.

The download generation is mostly listening through earpods, tabletop boxes with docking slots or computer speakers. Compared to the CD generation that burns out vintage gear by trying to play it at home theater volumes, the download generation probably won't even be able to operate vintage systems that don't use multipin connectors. We'll never hear from any of them here, except maybe for posts asking what the + and - symbols on their grandparents' old speakers mean.

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Where did I say that any of these people represented any significant market share, or that they were the current generation? All I said was that the are the folks who blow out speakers because they have no idea how to properly use vintage audio gear.

The download generation is mostly listening through earpods, tabletop boxes with docking slots or computer speakers. Compared to the CD generation that burns out vintage gear by trying to play it at home theater volumes, the download generation probably won't even be able to operate vintage systems that don't use multipin connectors. We'll never hear from any of them here, except maybe for posts asking what the + and - symbols on their grandparents' old speakers mean.

I must have misunderstood the intent of your comments, for which I apologize. When I said, tongue-in-cheek, that no one under 50 or 40 has an expensive audio system anymore, I took your counter comment about "quite a few" posters at Audio Karma "discovering vintage 2-channel" to be a disagreement by you with my contention that there is no commercially-significant 2-ch market in the U.S. any longer.

I agree with you about the '+' and '-' symbols being like ancient Latin to the download generation. Sadly, these symbols and things like the "5-way" binding post are testimony to the needless, self-inflicted complication with which the hi-fi industry shot itself in the foot, thus preventing its wider acceptance by the greater mass market.

5-ways to connect a speaker to an amp--sheer idiocy! Can you imagine if there were five ways to connect a VCR to a TV? If there were five ways to plug a TV into the wall? Can you imagine if a customer had to choose their own wire to plug a lamp into the wall and then fabricate the wire/connector itself and attach it to the lamp?

Single-point, color-coded, standardized connectors between all components would have been the way to go. Too late now.

Steve F.

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I must have misunderstood the intent of your comments, for which I apologize. When I said, tongue-in-cheek, that no one under 50 or 40 has an expensive audio system anymore, I took your counter comment about "quite a few" posters at Audio Karma "discovering vintage 2-channel" to be a disagreement by you with my contention that there is no commercially-significant 2-ch market in the U.S. any longer.

No problem. Just trying to prevent another kitchen-style debacle.

Modern home theater systems easily meet my definition of "expensive audio system," though precious few I have seen and heard meet my definition of a good audio system (I am currently trying to buck that trend by reorganizing some vintage AR speakers and a pre and pwr amp that should be able to handle both 2-ch and surround into a system).

I suppose that "commerically viable" is a relative term, though. There's certainly no mass market for 2-channel, and some might argue there isn't one for high-quality surround, either. But there does still seem to be enough of a niche market to keep a few diehards in business. At least for now.

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