HELP trouble shooting my AR Integrated amp

[Guest hifi13]

Hi everyone,

This is my first post so please bear with me. Also this is a great forum for all the vintage gear. Recently on another forum I have been hearing a lot of good things about AR gear, in particular the AR speakers so of course I decided to dig a little deeper to see what I could find and I stumbled upon this forum. Anyway this past Saturday my wife and I were out for a walk and came upon a local church having a rumage sale. I immediately scanned the tables for any gear, saw a couple CD players (which I picked up an older sony 505 for a whole 5 bux) some records. We were just about to leave and under a table I saw an old amp mounted to a piece of plywood. I told my wife to hang on a minute while I went and checked out what it was, turned out to be a mint AR Amplifier with the original manual. I asked the guy how much and he said $5 and I said sold. The first thing I noted was the weight, man that little amp is heavy. Don't make them like that anymore. Anyway I get it home and hook it up. Pots are a little scratchy, no big deal, and then I notice how nice it really sounds but it is only coming out of one channel. So I turn the balance over to the right and the sound coming out is very distorted and probably half the volume of the signal in the left channel. Hmmm. I check all the connections, try again, same thing. I switched the speaker wires around, same thing again. I tried everything but it seems to be the right channel of the amp. Anyone have any idea what might be causing this distortion? What could be blown or damaged? I am curious what it might be and what it might cost to fix as I quite enjoyed the sound of the one channel, very meaty and big. One other thing I should mention that might help deduce the problem, the guy I bought it from handed me a copy of a letter he had written to AR back in the early 90's requesting a schematic "as a power transistor requires replacing". I asked him if the power transistor had been replaced and he couldn't recall or didn't know as he wasn't the person who wrote the original letter. If anyone of you have any ideas what might be the problem I would greatly appreciate any help in this matter.

Thanks,

Dan

[Guest hifi13]

Another thing I should mention is I tried taking the cover off to have a look inside and I removed all the cover screws but there looks to be two rivets holding the cover to the heat sink? Is this normal, am I missing something, is it easy to remove these?

thanks in advance.

[Mexicomike]

Another thing I should mention is I tried taking the cover off to have a look inside and I removed all the cover screws but there looks to be two rivets holding the cover to the heat sink? Is this normal, am I missing something, is it easy to remove these?

thanks in advance.

Look on the bottom of the amp at the rear - directly in line with those rivets on the cover. There will be nut that holds a long threaded rod. The rod is threaded into the fitting that is riveted to the cover. The rivets holding that fitting is what you are seeing. Removing the nut at the bottom will allow you to remove the cover. The threaded rod may stay with the cover or may unscrew with the nut - doesn't matter.

When you remove the cover, do you see 4 potentiometers riveted to the chassis - two on each side of the amp? If so, this is an early and unmodified AR amp. They were known for problems due to the pots not maintaing their bias setting and causing thermal runaway. AR modified later amps with fixed resistors, removing the pots. This was described in an AR service letter. Thermal runaway could cause transistor failure and even cause the amp to catch fire. I speak from personal experience re the catching fire part!

I had three of these amps back when they were new, the first once caught fire, the second one failed from overheating. AR replaced them both but I sold the last one before it could self destruct!

Last year I found an unmodified original (with the pots). I bypassed the oem pots and installed some modern pots, adjusted the bias using a LOT of input from folks on this site, and the amp has been happily driving my restored AR3A's ever since.

First you should determine whether your amp is a potted amp or a fixed resistor amp. If it's potted, that needs to be addressed because one channel could be totally screwed up bias-wise which would affect the output of that channel. Of course, the bias error could also have fried a transistor which might explain that note.

There is a fairly long thread about this which includes what I did with my amp pot-wise...http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2172&hl=Mexicomike&st=0

[Robert_S]

Hello,

The AR Electronics Service Manual (Amplifier, Tuner, Receiver) is available in the Library, but the image resolution is fairly low:

http://www.classicspeakerpages.net/library...s_service_manu/

Enclosed is the AR Amplifier Schematic, at a higher resolution:

AR_Amplifier_Schematic_01.pdf

I am sure that others here will be able to offer you further advice regarding troubleshooting and repair options.

Robert_S

[Guest hifi13]

Look on the bottom of the amp at the rear - directly in line with those rivets on the cover. There will be nut that holds a long threaded rod. The rod is threaded into the fitting that is riveted to the cover. The rivets holding that fitting is what you are seeing. Removing the nut at the bottom will allow you to remove the cover. The threaded rod may stay with the cover or may unscrew with the nut - doesn't matter.

When you remove the cover, do you see 4 potentiometers riveted to the chassis - two on each side of the amp? If so, this is an early and unmodified AR amp. They were known for problems due to the pots not maintaing their bias setting and causing thermal runaway. AR modified later amps with fixed resistors, removing the pots. This was described in an AR service letter. Thermal runaway could cause transistor failure and even cause the amp to catch fire. I speak from personal experience re the catching fire part!

I had three of these amps back when they were new, the first once caught fire, the second one failed from overheating. AR replaced them both but I sold the last one before it could self destruct!

Last year I found an unmodified original (with the pots). I bypassed the oem pots and installed some modern pots, adjusted the bias using a LOT of input from folks on this site, and the amp has been happily driving my restored AR3A's ever since.

First you should determine whether your amp is a potted amp or a fixed resistor amp. If it's potted, that needs to be addressed because one channel could be totally screwed up bias-wise which would affect the output of that channel. Of course, the bias error could also have fried a transistor which might explain that note.

There is a fairly long thread about this which includes what I did with my amp pot-wise...http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2172&hl=Mexicomike&st=0

Thanks for the help Mexicomike. I did get the cover off and it looks like there are oem pots. I have attached a photo I took. So is replacing the oem pots a large task? How much did it cost you? I am not much of an electronics wizard, I am handy with a soddering iron but not too savvy when it comes to identifying what needs to be replaced or fixed. Should I leave this sort of thing to a professional or can it be done by a novice?

[JKent]

Welcome! You'l find lots of help here. GREAT find!! Five bucks. Wow!

The service manual is available as a free download here:

http://www.hifiengine.com/manuals/acoustic...amplifier.shtml

Kent

[Robert_S]

it looks like there are oem pots. I have attached a photo I took

Though your picture does show the pots, it looks like they are disconnected, and that the fixed resistor modification is already in place. I would also guess that the two pale-tan coloured resistors are even more recent replacements, indicating perhaps a previous problem in this area.

Robert_S

[Guest hifi13]

Though your picture does show the pots, it looks like they are disconnected, and that the fixed resistor modification is already in place. I would also guess that the two pale-tan coloured resistors are even more recent, indicating perhaps a previous problem in this area.

Robert_S

Perhaps a good cleaning of the pots would help? What other sorts of things can I look for?

[Mexicomike]

I agree with Roger - it appears that the pots are no longer connected so the mod has apparently been accomplished. Those two tan resistors are definitely something that has been added to the circuit as well, though not being an electronic expert, I have no idea what their purpose might be but it appears they only affect once channel which automatically seems to me like NOT a good thing. Here's a pic of my original AR AMP as I received it and before I removed the oem pots from the circuit and substituted new pots. I did not remove the pots, I just attached the new pots on top of the old ones. That way it can be returned to oem condition with no permanent damage should someone in the future prefer that.

As far as how to proceed from this point - It would be best to wait for some real circuit experts to suggest something; I'm not one of those! A good repair shop could sort it out I'm sure; I have no idea of what it would cost. Whether it's worth it or not depends on how much it would cost and the use you would make of it. It's a fairly powerful amp for it's size but although AR made it as part of their complete stereo system - AR turntable, AR amp, AR speakers, it's not really powerful enough to bring out the best in the 10" and 12" woofered AR speakers for serious listening. That being said, I really like mine and use it every day. In my small office, it doesn't have to work too hard to get the 3As up to "loud enough" levels

[Guest hifi13]

I agree with Roger - it appears that the pots are no longer connected so the mod has apparently been accomplished. Those two tan resistors are definitely something that has been added to the circuit as well, though not being an electronic expert, I have no idea what their purpose might be but it appears they only affect once channel which automatically seems to me like NOT a good thing. Here's a pic of my original AR AMP as I received it and before I removed the oem pots from the circuit and substituted new pots. I did not remove the pots, I just attached the new pots on top of the old ones. That way it can be returned to oem condition with no permanent damage should someone in the future prefer that.

As far as how to proceed from this point - It would be best to wait for some real circuit experts to suggest something; I'm not one of those! A good repair shop could sort it out I'm sure; I have no idea of what it would cost. Whether it's worth it or not depends on how much it would cost and the use you would make of it. It's a fairly powerful amp for it's size but although AR made it as part of their complete stereo system - AR turntable, AR amp, AR speakers, it's not really powerful enough to bring out the best in the 10" and 12" woofered AR speakers for serious listening. That being said, I really like mine and use it every day. In my small office, it doesn't have to work too hard to get the 3As up to "loud enough" levels

Could the tan resistors be the culprit? Power transistors perhaps?

[Mexicomike]

In looking more carefully at you pic, I see that the new tan resistors in the right channel duplicate the positioning of a pair of dark brown resistors in the left channel. I can't tell if the stripe colors are the same or not but I would ASSUME that they are and that both resistor pairs are the same value. They are probably part of the pot bypass arrangement. It is certain that AR or an AR service provider did not make the mod because when they did it, they removed the old pots completely and put in a terminal strip for the resistors, as called for in the AR service info on this upgrade.

[ar_pro]

I bought one of these amplifers new, in 1972, and also rebuilt a $10.00 flea-market amplifier with NOS parts from AR, back around 1989 - I seem to recall problems with getting the correct small-signal & power transistors at that time. It also looks like the big electrolytic capacitors on your amp are original, so they're probably due for replacement, as well.

To be honest, although I really wanted to like the amplifier, it always seemed a bit of a kludge, and that separate "soft-start" power supply made me reluctant to leave it plugged in while out of the house.

For sure, it's a nice-looking component from that conservative school of industrial design that AR so clearly represents, but it was never a world-beater, and that was 40 years ago!

[Robert_S]

Perhaps a good cleaning of the pots would help? What other sorts of things can I look for?

The pots we are referring to here are for bias adjustment, and though present in your amplifier, they do not appear to be part of the active circuitry (they are simply serving as substitutes for terminal points), cleaning them would make no difference. Cleaning the rest of the entire unit could be a worthwhile exercise though! The tape monitor switch especially "since all the inputs pass through this switch". The two tan resistors are nothing to worry about (assuming that they are the correct in value and operation), they are just later replacements.

Personally, unless you wish to clamber on a potentially steep learning curve, I would employ professional help. With the manual and the proper parts, any good electronics technician should be able to repair your Amplifier. Perhaps someone here can recommend a suitable candidate practicing in your part of the world?

It is certain that AR or an AR service provider did not make the mod because when they did it, they removed the old pots completely and put in a terminal strip for the resistors, as called for in the AR service info on this upgrade.

Not necessarily! For units modified in the field, the Service Bulletin illustrated the fixed resistor modification implemented with the bias pots left in place, though removed from the active circuit:

http://www.classicspeakerpages.net/IP.Boar...?showtopic=4554

Robert_S

[Mexicomike]

That's interesting, the AR service manual that describes the change explains removing the pots. Good info!

[Pete B]

I have to wonder when this was designed, probably before Silicon PNP devices were available.

It is a flawed design, there is no DC feedback to stabilize the DC offset.

This design requires matched 2N3055s and 2N3054s so that each half has identical Ic vs. Vbe.

Still, it is wishful thinking that it should hold a stable DC offset without matched parts.

There is one thing that probably makes this amp work. Devices that come from the same wafer,

are indeed nearly clones of each other. When you buy a lot of parts there is a good chance

that they'll all come from the same wafer, or if you hit a transition in production from two wafers.

The 2N3055 is probably the most popular Silicon NPN power transistor and it is still

in production today. However, I don't believe that it is exactly the same part, rather

it is an improved part. It is also a preferred part from OnSemi which means that it is

fine to use it in a new design as they plan to keep on producing it for many years:

http://www.onsemi.com/PowerSolutions/product.do?id=2N3055

Note that the part is rated for 60V which is below the total voltage seen in circuit, 39 +39 V.

The parts were probably selected for higher Vce. I would use the 2N3773 which is a higher

voltage/power device with similar/better characteristics, if I were rebuilding one of these.

The better solution is to rebuild it into a more modern design, either the quasi-complementary

RCA reference design, or even better a modern variation on it.

The 2N3054 has been out of production for many years.

[Guest VINTAGE-AR]

Hi everyone,

This is my first post so please bear with me. Also this is a great forum for all the vintage gear. Recently on another forum I have been hearing a lot of good things about AR gear, in particular the AR speakers so of course I decided to dig a little deeper to see what I could find and I stumbled upon this forum. Anyway this past Saturday my wife and I were out for a walk and came upon a local church having a rumage sale. I immediately scanned the tables for any gear, saw a couple CD players (which I picked up an older sony 505 for a whole 5 bux) some records. We were just about to leave and under a table I saw an old amp mounted to a piece of plywood. I told my wife to hang on a minute while I went and checked out what it was, turned out to be a mint AR Amplifier with the original manual. I asked the guy how much and he said $5 and I said sold. The first thing I noted was the weight, man that little amp is heavy. Don't make them like that anymore. Anyway I get it home and hook it up. Pots are a little scratchy, no big deal, and then I notice how nice it really sounds but it is only coming out of one channel. So I turn the balance over to the right and the sound coming out is very distorted and probably half the volume of the signal in the left channel. Hmmm. I check all the connections, try again, same thing. I switched the speaker wires around, same thing again. I tried everything but it seems to be the right channel of the amp. Anyone have any idea what might be causing this distortion? What could be blown or damaged? I am curious what it might be and what it might cost to fix as I quite enjoyed the sound of the one channel, very meaty and big. One other thing I should mention that might help deduce the problem, the guy I bought it from handed me a copy of a letter he had written to AR back in the early 90's requesting a schematic "as a power transistor requires replacing". I asked him if the power transistor had been replaced and he couldn't recall or didn't know as he wasn't the person who wrote the original letter. If anyone of you have any ideas what might be the problem I would greatly appreciate any help in this matter.

Thanks,

Dan

Dan:

Although it's nearly impossible to perform quality troubleshooting by email, let me see if I can give you some information.

First, the internal pots. I see these frequently. This was most likely modified by AR at the factory. Either they caught it prior to final production or it was returned for service. These most likely have nothing to do with your problem.

If you have output from both channels but only one is lower in amplitude and distorted, the problem is most likely not with the power transistors in the final output stage. Failures here frequently result in a dead channel and or burned components and or A blown fuse.

Your problem is most likely associated with the Driver Amplifier Board mounted to the side panel. This is a common failure.

You should continue with your repair. This is an excellent amp and highly sought after on eBay.

If you get stuck you may send it to me for service. See my link on the opening page.

Larry (VINTAGE-AR; SPECIALIZING IN THE SERVICE AND REPAIR PARTS FOR EARLY AR SPEAKERS AND ELECTRONICS).

[trask]

I've a couple of thoughts to add, and a query. First, the AR Amplifier is an excellent amp. I have several different amps on hand to drive my AR-5's and somehow the AR amp seems to have just that extra bit of pizzazz or sonic excitement that makes the music more interesting. Not as clean as my VFET amp, perhaps, just more invigorating. Does it have to do with the interstage transformers (which I've learned are what early SS guitar amps used back when SS circuits were still being developed)? Or is the overall design? I don't know, but I do know I like it. FYI, I got my amp from Larry at Vintage AR, and I'd endorse him as a good source of information on the amp.

I have also picked up an old japanese integrated from the early 70's that uses interstage trannies just like the AR, so it'll be interesting to see how they compare sonically.

Now for the query -- I keep reading about how AR speakers (and in particular the AR-3's because they're 4 ohms) really sing with high-output amps. Somehow the logic of this has always escaped me. As long as the amp you're using drives the speakers to the volume you wish without transient clipping, I don't see what having the extra watts on tap does for you. Sure, we all know that driving an amp into clipping distorts the sound and may blow our tweeters, but assuming you're not driving the speaker to clipping, if 40 watts gives you good clean sound, what supposedly do the other 160 watts in a 200 watt amp do for you? OK, higher current may be desirable, but just counting watts? Someone please give me a view on that issue.

[Guest hifi13]

Dan:

Although it's nearly impossible to perform quality troubleshooting by email, let me see if I can give you some information.

First, the internal pots. I see these frequently. This was most likely modified by AR at the factory. Either they caught it prior to final production or it was returned for service. These most likely have nothing to do with your problem.

If you have output from both channels but only one is lower in amplitude and distorted, the problem is most likely not with the power transistors in the final output stage. Failures here frequently result in a dead channel and or burned components and or A blown fuse.

Your problem is most likely associated with the Driver Amplifier Board mounted to the side panel. This is a common failure.

You should continue with your repair. This is an excellent amp and highly sought after on eBay.

If you get stuck you may send it to me for service. See my link on the opening page.

Larry (VINTAGE-AR; SPECIALIZING IN THE SERVICE AND REPAIR PARTS FOR EARLY AR SPEAKERS AND ELECTRONICS).

Thanks to everyone for all the information and suggestions it helps quite a bit although I am still at square one with the amp as I am only slightly versed in electronics, just enough to be dangerous, but I am learning and trying. Anyway I just wanted to add or update what I had said in my first post. As far as the right channel being distorted it only comes through when the mono switch is engaged, I don't get any, or very very faint signal from the right channel. I am sorry I should have mentioned it in my first post as I am sure it might help trouble shoot the problem. I was just caught up in scoring what I feel is a nice piece of audio gear from the past. I agree that the am has something to it as far as sound quality goes, even when listening to only the one channel I was impressed with how robust and almost musical the amp sounded. Albeit the design may not be the most stable after 30+ years and some parts are worn or need replacing I do feel for the money and the potential to learn something about electronics in the process it is a steal indeed. When I mentioned what I had scored to a fellow audiophile friend of mine, who by the way is a pretty strict vinyl/tube guy he was intrigued as to the sound as he remembers the speakers as well as the amps from back in the day. So I am hopeful to say the least. Plus with the help and encouragement you guys are giving me it makes it that much harder to not get this amp up and running.

[Mexicomike]

I don't know if this will help much but I have often been surprised at how much power is actually required to produce loud, but not REALLY LOUD volume levels. I have a McIntosh 270wpc SS amp with meters that have a switch you can set for peak readings. That is, the needles move to the highest wattage and stay at whatever peak they registered.

With the 3As (my 3As are not normally connected to this amp, usually they are connected to my AR amp), at a moderate volume level, the meters are peaking in the 30 watt range. But if you increase to what I'd call loud but comfortable (serious music listening) levels, they hit the 250+ watt range frequently. They even hit their peak limiter circuitry (red light pops on) occasionally with the 3As or the Maggies, which are normally connected to this amp. This means to me that if you have the volume set to produce this sound level on an amp with less power, you are well into clipping with the attendant potential for tweeter/mid damage.

I use my AR Amp/3A's in my small office. The AR amp, with a line level input, will blow you out of the room with the volume control at the 12-oclock positiion. I don't have any idea of what that really means watt-wise. I could bring the Mc up stairs to check but since it weighs 60-70 pounds, it's not something I'm THAT interested in checking.

However, we sometimes sit upstairs in our "sunroom" which is not far from my office and have a few drinks and listen to music on the AR amp/3A system. We have blown the Amp output fuses with the volume at comfortable levels in the sun room...

[Guest hifi13]

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.

[Guest hifi13]

I don't know if this will help much but I have often been surprised at how much power is actually required to produce loud, but not REALLY LOUD volume levels. I have a McIntosh 270wpc SS amp with meters that have a switch you can set for peak readings. That is, the needles move to the highest wattage and stay at whatever peak they registered.

With the 3As (my 3As are not normally connected to this amp, usually they are connected to my AR amp), at a moderate volume level, the meters are peaking in the 30 watt range. But if you increase to what I'd call loud but comfortable (serious music listening) levels, they hit the 250+ watt range frequently. They even hit their peak limiter circuitry (red light pops on) occasionally with the 3As or the Maggies, which are normally connected to this amp. This means to me that if you have the volume set to produce this sound level on an amp with less power, you are well into clipping with the attendant potential for tweeter/mid damage.

I use my AR Amp/3A's in my small office. The AR amp, with a line level input, will blow you out of the room with the volume control at the 12-oclock positiion. I don't have any idea of what that really means watt-wise. I could bring the Mc up stairs to check but since it weighs 60-70 pounds, it's not something I'm THAT interested in checking.

However, we sometimes sit upstairs in our "sunroom" which is not far from my office and have a few drinks and listen to music on the AR amp/3A system. We have blown the Amp output fuses with the volume at comfortable levels in the sun room...

Living in an apartment kind of limits the volume I can get away with, although I do say 'kind of' as some days I can get away with much louder than usual listening sessions. With me it's more quality over quantity when it comes to sound and volume. Although some of the bass peaks really suck the wattage much like you say when your amp meters peak at 250+ range, that's where muscle in an amp counts. Blown fuses are much cheaper than blown tweeters or mids. Gotta love McIntosh amps.

[dynaco_dan]

I don't know if this will help much but I have often been surprised at how much power is actually required to produce loud, but not REALLY LOUD volume levels. I have a McIntosh 270wpc SS amp with meters that have a switch you can set for peak readings. That is, the needles move to the highest wattage and stay at whatever peak they registered.

With the 3As (my 3As are not normally connected to this amp, usually they are connected to my AR amp), at a moderate volume level, the meters are peaking in the 30 watt range. But if you increase to what I'd call loud but comfortable (serious music listening) levels, they hit the 250+ watt range frequently. They even hit their peak limiter circuitry (red light pops on) occasionally with the 3As or the Maggies, which are normally connected to this amp. This means to me that if you have the volume set to produce this sound level on an amp with less power, you are well into clipping with the attendant potential for tweeter/mid damage.

I use my AR Amp/3A's in my small office. The AR amp, with a line level input, will blow you out of the room with the volume control at the 12-oclock positiion. I don't have any idea of what that really means watt-wise. I could bring the Mc up stairs to check but since it weighs 60-70 pounds, it's not something I'm THAT interested in checking.

However, we sometimes sit upstairs in our "sunroom" which is not far from my office and have a few drinks and listen to music on the AR amp/3A system. We have blown the Amp output fuses with the volume at comfortable levels in the sun room...

""We have blown the Amp output fuses with the volume at comfortable levels in the sun room...""

Hi there;

If you are using the 3 amp fast blow fuses as provided by AR as default amplifier protection fuses you are walking on very dangerous ground.

Please confirm the fuse type and size please and I will continue to add to this topic.

Vern

[dynaco_dan]

Another thing I should mention is I tried taking the cover off to have a look inside and I removed all the cover screws but there looks to be two rivets holding the cover to the heat sink? Is this normal, am I missing something, is it easy to remove these?

thanks in advance.

Hi there;

Sorry, but after reading the above I feel that you are not capable of repairing this AR amplifier and should leave it to a more electronicly oriented service individual.

Do not even go inside to clean up anything, especially the switches and controls.

I don't expect this site to ever be able to do all that is needed to help service electronic equipment.

It would be like trying to make a homeowner into a car mechanic.

Even some of the better service people cannot service the AR amplifier, receivers or tuners.

With a copy of the bios service sheets and a service manual copy, a service person has a much better chance than a do-it-yourselfer, with little or no skills or service or test equipment.

I have posted those bios sheets twice on CSP, when I first came on board and again last year, and even I found it difficult to find them again.

We, on this site, have the best chance of upgrading an already working unit, not a partially working one, with these sheets.

I do not feel that this site, at this time, can provide the technical support to service most all electronic equipment correctly.

We do not have all the spec's.

Most members do not have even some of the test equipment.

Speakers, mostly, yes indeedy.

AR turntables, a fair amount of help, I feel.

Perhaps in the future there may be more service technicians that can try to troubleshoot and diagnose on-line.

I have assembled lot's of Dynaco and Heathkit projects and there is always a small chance of error and none available parts now.

You cannot just plug and play parts until it works.

I consider the AR amplifier a very good amplifier and it was pretty outstanding when it first came out.

It included that special muting circuit, excellent tone controls, simplicity and clean 100+ watts at 4 ohms usually.

In mint condition externally, mostly the faceplate, up to $150.00 is not too much to invest, based on your cost.

Most, if not all, electrolytic caps, should be replaced on principle as well.

I feel that one hour and perhaps $50.00 in parts, if the amp is carried into a service facility, should eliminate the present problem.

I believe everyone charges for estimates now, so, be prepared.

Vern

[JKent]

where do I go from here?

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

[Guest hifi13]

Hi there;

Sorry, but after reading the above I feel that you are not capable of repairing this AR amplifier and should leave it to a more electronicly oriented service individual.

Do not even go inside to clean up anything, especially the switches and controls.

I don't expect this site to ever be able to do all that is needed to help service electronic equipment.

It would be like trying to make a homeowner into a car mechanic.

Even some of the better service people cannot service the AR amplifier, receivers or tuners.

With a copy of the bios service sheets and a service manual copy, a service person has a much better chance than a do-it-yourselfer, with little or no skills or service or test equipment.

I have posted those bios sheets twice on CSP, when I first came on board and again last year, and even I found it difficult to find them again.

We, on this site, have the best chance of upgrading an already working unit, not a partially working one, with these sheets.

I do not feel that this site, at this time, can provide the technical support to service most all electronic equipment correctly.

We do not have all the spec's.

Most members do not have even some of the test equipment.

Speakers, mostly, yes indeedy.

AR turntables, a fair amount of help, I feel.

Perhaps in the future there may be more service technicians that can try to troubleshoot and diagnose on-line.

I have assembled lot's of Dynaco and Heathkit projects and there is always a small chance of error and none available parts now.

You cannot just plug and play parts until it works.

I consider the AR amplifier a very good amplifier and it was pretty outstanding when it first came out.

It included that special muting circuit, excellent tone controls, simplicity and clean 100+ watts at 4 ohms usually.

In mint condition externally, mostly the faceplate, up to $150.00 is not too much to invest, based on your cost.

Most, if not all, electrolytic caps, should be replaced on principle as well.

I feel that one hour and perhaps $50.00 in parts, if the amp is carried into a service facility, should eliminate the present problem.

I believe everyone charges for estimates now, so, be prepared.

Vern

I think I would have to agree with you Vern, I am having serious doubts about my ability coupled with my inexperience in electronics to do this sort of thing on my own. I will have to seek out a professional for this job. I think my time building a new case would be better spent. Thanks for the wake up call. I was all to caught up in the excitement of perhaps fixing this myself.