My Amp is Broken - Not Sure What to Do - Any Recommendations?

It depends upon how tight you want them matched I suppose, and if you want to set up a test bed for them, etc. I just have better things to do. I have a pile of gear to troubleshoot and repair as it is...

3 matched devices per phase per channel on the SD135.
Usually you can get a matched triplet every 10 devices AT LEAST.
Now if the SD135 had say 10 devices per phase per channel that’s a completely different story.
Getting 3 devices to match is much much easier than say 5 or 6.
So figure even if BOTH channels are shot,
Buy 12-15 of each type and you can get 2 sets of each from mouser.com.
Unlike tubes, esp. those snake oil KT88 and WE300B replicas,these "sand" devices only cost a few bucks each. 2 hours of the tech’s bench time cost more than the components.
When done, sell the surplus on eBay for 1/2 the acquisition cost. heck you might even get 1 or 2 extra matched triplets good for the next hobbyist!
I am not advocating a DIY approach, just find a competent tech who knows how to match devices and bring up an  amplifier using a variac instead of a crow bar.

"Do you guys think it would alter the sound to replace the 3281D and 1302D Thermal Trak transistors with NJL3281DG (NPN) NJL1302DG (PNP) Thermal Trak transistors, and do you think the work to match the output devices would be difficult or highly involved?"

Matching devices properly is expensive and a pain. You have to buy a ton of them to get the matched sets you need. Jon Soderberg repairs old Threshold amps, he buys transistors in lots, then sorts them according to which matches which. If you do that you’ll end up with a very large number of devices that you’ll have no use for. Unless you are going to do a lot of amps, once you get a matched set, all the rest are pretty much useless to you. Someone who does it all the time will just keep putting together matched sets. The few oddballs left will be matched up when he buys another lot.

If you have no need to replace the output devices, leave them alone. I have been fortunate enough to have always found someone who matches them, so I don’t have to. They cost a lot more, but far less than it would cost to buy enough to get a matched set!

Be sure you don't kill yourself when you short a filter cap to the chassis (seriously).

I used to be a do-it-yourselfer, but as I got older and wiser, I realized the experience, knowledge, and training involved was not worth the expense.

Those of you who enjoy such things, by all means keep on soldering.  Most of us just want to push a button and have the stereo come on.  Asking me to match output devices is about the same as asking me to carve an amplifier out of a billet of aluminum.

I would look at the spec sheets of the new and old parts. The things to look for are maximum current, breakdown voltage, hfe. If those three things are right, then its likely no worries.

Obviously there's a little bit of engineering to do all this, but its not rocket science. Any tech (not engineer even) that actually went to school should be able to do it. Matching shouldn't be a huge deal.

If you get it right, the sound won't change. This is mostly a reliability issue. BTW $50/hour sounds cheap!

Regarding reliability of the replacement parts, ARC may have the same concerns as you; if this were my amp I would share that concern!

Do you guys think it would alter the sound to replace the 3281D and 1302D Thermal Trak transistors with NJL3281DG (NPN) NJL1302DG (PNP) Thermal Trak transistors, and do you think the work to match the output devices would be difficult or highly involved? I know of a good audio technician in my area who makes certified repairs for McIntosh and Arcam equipment, but he gets $50/hour.

I am also concerned that even if the repair is successful, the new Thermal Trak transistors will fail at some point and I might be in the same boat I am now. Do you think that could be why Audio Research stopped using them in their new equipment and won't service older devices with them?

Thanks again.

Not hard for a guru like you Ralph!  But I have had the pleasure of dealing with botched jobs of those $25/h audio repair experts who couldnt figure the difference between emitter and collector that I think dealing with a 5 pin output device would be a hair-pulling experiment.  I think I know why Audio Research doesnt want to service these things.... Figure the parts cost and the need to keep inventory of matched triplets for SD135 and matched Sextets for HD220 can be a cost they may not be able to recover.  After engaging in this thread curiosity got me to open up my HD220 and BOY AM I LUCKY.... my HD220 actually has 1302DGs and 3281DGs!   I know from the seller that the unit went back to Audio Research once in 2012/13.  Maybe those were the days when Audio Research still cared.   And yes each device has markers that indicated they were hand matched.

Hm, The output section is right out of OnSemi's application notes.

Devices like this give me the willies, since so much relies on them. If it were me, I would be tempted to test the transistor portions to see if they are still good, and if so, perhaps see if a diode applied the transistor could sub for the diode portion of the device. If the amp heats up or has crossover/notch distortion issues, then a bias scheme would have to be employed.
But of course outfitting it with new devices seems the preferred method. This just doesn't seem like it would be that hard to sort out.

Even the manual found online says the original devices are 3281D and 1302D
Replace the defective channel's output devices with MATCHED
DG versions and you are good to go.

OP lucky you the schematic is HERE:

https://elektrotanya.com/PREVIEWS/63463243/23432455/audio-research/audio-research_sd135_amplifier_sc...

I bet not everything is toast likely 1 phase of 1 channel.

Get a tech WHO KNOWS HOW TO MATCH OUTPUT DEVICES.
Buy a dozen of 
NJL3281DG (NPN) NJL1302DG (PNP)
and match them and repair the blown channel!

It was my experience, that William Z Johnson cared very much, about his customers and his corporation. On the other hand; I’ve no doubt Macintosh wishes the corporation(and the competition) never existed, though they now own it.

https://www.mouser.com/ProductDetail/ON-Semiconductor/NJL3281DG?qs=sGAEpiMZZMvFp%252byPHbnZYyVkaBWrH...

3281D was INDEED obsolete.
Original collateral dated June 2006
http://www.onsemi.com/pub/Collateral/NJL3281D-D.PDF

replaced by 3281DG  Same application notes per Mouser.com and ONSemi.  Available and NOT discontinued.

My HD220 has not blown (yet) so I have not attempted a repair myself.
I suspect it means you need to change out ALL the devices for matching sake.  That's likely why Audio Research doesnt want to deal with it.
Boy if they could just respond to my email and get me the schematic!

Hey all,

Thank you for the replies and helpful advice. The fellow I spoke with at Audio Research told me the Thermal Trak transistors currently offered by OnSemi are a new version of the ones used in my SD135. He said that unfortunately they are not the same as what was used in the SD135 and (according to him) will not work in my unit. 

The guy I spoke with at ARC told me that the company considered trying to come up with a work around for the original Thermal Trak transistors no longer being available, but nothing ever materialized.

I suspect a lot of people are going to be having difficulty with their amps over the next decade or so when the Thermal Trak transistors fail on them. These particular parts are known to have a somewhat significant rate of failure. Besides Audio Research, McIntosh used them, as well as Arcam, Mark Levinson and Ayre.

https://www.diyaudio.com/forums/solid-state/237929-thermaltrak-transistors-discontinued.html

I believe some manufacturers are still using the latest versions of Thermal Trak transistors in their current product lines. Although it looks like Ayre just stopped using them this year: https://www.audioasylum.com/cgi/vt.mpl?f=amp&m=184484

Anyway, this really stinks. I never would have thought this would have happened when I purchased my SD135. I may be wrong, but I think if Bill Johnson were still alive, ARC would come up with the work around to service the discontinued gear of his loyal customers.

johnsonwu, cool!

The parts did not go obsolete.  Check OnSemi, aka ON Semiconductor who manufactures the parts.  Audio Research EOLed the SD135 and HD220.  

Ouch! The government regulates support for equipment, but sometimes even that ends up being ignored. A manufacturer is supposed to stock enough spares to last X years depending upon the product. Stereos are likely about 3 years. Near the end of tube screen TVs a salesman told me that one TV had a faulty horizontal flyback transformer issue, and they had run out of spares, but were still selling the TVs, so the spares are judged based upon estimates/projections not actual parts lives.

I am a fan of ARC equipment and I have owned various amps and preamps of theirs, both tube and solid state through the years. The planned obsolescence on some of their solid state equipment is an issue for me also, however. In the 1980's they had the Analog Modules which are no longer available. They were proprietary modules sealed with potting material. I have spoken with people who tried to dissect them with acetone and figure out the circuit and recreate it, but they had limited success. The early solid state amps (D52, D100, D110, D350 etc.) and preamps (SP4, SP5) all used these modules, and now this equipment has been scrapped or parts out due to lack of availability. I have had to junk a D52B and a D350 because these modules are no longer available.

Look, I have B&W 801M’s with all caps in series with the speakers bypassed with Audyn True Copper Max caps. Thiel CS-7 speakers, Paradigm Studio Reference 100 V2’s Ellis Audio 1801’s, KEF Reference 105s I have had Quad ELS57s, Acoustat 3300’s Acoustat Mdl 3s, Vandersteen 1Bs, 2CE Signatures, etc. All the Vandersteen speakers that I have heard, including 3A Signatures as I recall, sound like pretty good speakers with blankets over the tweeters. As a test, I bypassed the T-H-R-E-E capacitors IN SERIES on the 2CE Signatures tweeters with a .1uf V-Cap, it made ears bleed. They knocked down they highs so the tweeters were not crazy hot. As a test, I installed a pair of Hiquphon tweeters, they didn’t have the range of the Vandersteen tweeters, and the crossover was tuned to the Vandersteen tweeters, but the details were now there without the harsh highs as they should have been all along. A friend was over and immediately fell in love with them. I explained that with those tweeters there would be issues, but he loves them anyway, and he wanted nothing to do with them without and especially with the V-Caps until I decided to try out the Hiquphons. So, I know bright from dark, and frankly I now have a full range driver and with no crossover whatever, that is THE most detailed speaker I have EVER heard. In fact I pretty much had to revamp my entire stereo because of the ability of these drivers to revel details. Anyway, Vandersteens excel at masking upstream issues. They sound very musical, very enjoyable unless you are about really drilling down on detail. Detail can ruin an otherwise beautiful song. Poor recordings, less than awesome equipment, etc., etc., are all good reasons to love Vandersteen speakers. Relentless details are not for everyone! If you love Vandersteens, that’s great, enjoy them. Everyone has different goals where their listening is concerned. Find yours, and enjoy before you end up with a ridiculous list of gear that you have bought and sold!

+1 @Bigboltz,
-1 @ glowworm
If anyone finds Vandy's 'warm' or 'not articulate' aren't using the right equipment, or haven't set them up correctly.
Bob

Lous is correct, the 3s are warm and hide a lot of warts on the top end. Likely why they’re often used with rock music as a source, esp. CDs

“Vandersteen’s aren’t the most articulate...”

wait, what?  3A sigs will reveal the differences between whatever you put in front of them. 

Oh, there is one other option I could suggest. Vandersteens are not the most articulate speakers out there, so you can probably procrastinate doing a bridge rectifier mod to it, but there is a PS Audio 200C amplifier on eBay right now. I think he has come down at least 100, and it may be 100 and free shipping, I don't recall if he was throwing in shipping or not initially. $700 is still a little high for that amp, but it will drive the Vandys with no problems. I have a friend who is borrowing one of my 2 PS amps for his Vandy 2CE Signatures and he loves it. Obviously owning 2 of them, you know that for a transistor amplifier I really like them for the money. BTW, I would try offering him $550, and even that may be high for a stock amp, but no way would I pay more than 600 shipped, and make sure it's insured, clumsy delivery people can destroy an amp with the monster coil it has if they drop it the wrong way.

I think the slew rate is a crazy 400V per millisecond, my tube amp is 60? It owns speakers, back in the day it was one of only a few that could really drive the big Appoge speakers, which went down to 2 ohms. You will fry the amp if you plug or unplug your preamp or speakers while it's turned on though,  and the relay buzzes. A lot of folks think it's the coil, but the relay chatters, if you go that way, there is a company that makes a direct replacement for about 60 dollars. It's one of those, if it bothers you things. It's worth it because you would have to spend a ton to get another transistor amp that sounds as good, much less that can drive a load like the 200C or 200CX.

The other thing is, like most amps of its age, the bridge rectifiers suck! So at some point you really should replace them with Fred's, Hexfreds, or Stealth diodes, I prefer to use IXYS Freds from Partsconnexion, or Michael Percy Audio.  Anyone who can solder should be able to easily replace them for you. It wouldn't hurt to add some nice bypass caps to the power supply. One of mine has a TX2575 resistor on the input, and I am probably going to go through and replace all the resistors in it. I am a detail freak, it is just a shade dark, but like the old Forte F44 preamp, it's actually a pretty awesome viscerally pleasing sound, which is why I have never gone that far with one. I have replaced the caps on the boards with Black Gates, but the bridge rectifiers are what it really needs to fully come into its own. I have been told that some Levenson amps can really control speakers, I can't speak to that, but the PS amp owns what ever I have thrown at them.
 

Parts go obsolete, I've had to run down a lot of obsolete parts, some companies have made products using discontinued parts, knowing before their production run that the parts had been discontinued!

If you really liked that amp, I'd contact Roy Mottram at tubes4hifi.com, he has designed many tube amps, preamps, and phono preamps. You could also contact Don Sachs, but it's unlikely that he'll do repairs, last I knew he was way behind in making his own amps and preamps. Anyway, those guys are big on tube circuit design and may have already worked on your problem for someone else.

I agree, this is lousy customer service. If I did buy a new amp it wouldn’t be an ARC. Their power amps are prone to failure. They do sound good when working though

I have a Thermaltrak equipped HD220 myself and Audio Research would ABSOLUTELY refuse to return my repeated calls AND repeated emails.  The good old days of Leonard and Kalvin are gone.

A $25/hr tech... GOOD LUCK finding one who knows what the 5 pins of the thermaltrak devices are about.   

Take ARC to task on the repair if no satisfaction  give Tom a call @ Northridge Electronics in Simi Valley Ca.   This is an old school tech who really knows his stuff and is a repairman pure and simple with no funny stuff about boutique cures or similar ilk.   

Distortions:  I recommend that that you formally enter a repair/service request on the ARC website.  Notwithstanding the fact that your warranty has expired, reputable equipment manufacturers will want to exhaust options available to satisfy the customer.  Since the ARC technician has already indicated there is a failure history (if not a latent defect), putting your request in text places the onus on the company to provide a formal response.  Based on my personal experience with amplifiers being blown out by lightning (electrical) and thunder (concussion) storms, I can tell you that company corporate and subordinate units really do listen and find ways to make the original purchaser happy and preserve the image of their brand.  I know it can be frustrating and time-consuming but, if necessary, you can keep going up the corporate ladder until somebody pays attention and commits to resolving the problem.  Do not simply accept the word of a first-level service technician or customer service representative, but ask to speak to their supervisor.  Best wishes for a successful outcome. 

Look in the Yellow Pages and you will find dozens of competent amp techs down the street from you willing to work for $25.00/hr.  Or buy a new amp.

Whatever you decide, I recommend you look into a Vandy sub(or two).  Besides sounding awesome with musical bass, they will allow your speakers to be hi- passed which offloads the bass responsibility from your amp. Believe it or not, your Vandies will sound better top to bottom, not just in the bass.   The 2w’s can be found for pretty cheap

Here’s the problem with ThermalTrak devices that supposedly was solve by Ayre but not AR https://www.stereophile.com/solidpoweramps/407ayre/index.html
ON Semi only made 1 set of thermaltraks, and yes I just confirmed that Mouser has them in stock.
By the way the SD135s are only 10 years old.

Contact Jeff Jackson at lktrnx@gmail.com. He's a great guy and will give you the straight scoop on realistic options. 

Good luck! 

grannyring4,348 posts10-14-2018 1:28pmA good tech/modifier could fix this amp. You simply need a new way of handling the protection circuit in your amp. No way your amp is now trash. Are you near any good tube amp builders or techs?

+1
This is AR b***s**t, of course this can be repaired by a competent tech in an alternative way. AR just want you to buy a new one. As grannyring said find a competent tech and get it fixed.

Cheers George 

Ralph the OP was referring to thermaltrak output chips made by OnSemi.  Can’t be bypassed.  They were discontinued for a while. Now back in
the market.  

You can still get thermaltrak chips on mouser or digikey last I checked.  

It blows away many more expensive high end amps. Really.  Help me out here and just name a few for me please.

 It sounds like some sort of protection switch. If the amp is over driven or over heats, then it turns the amp off. You may not be able to over ride it safely. Though I do agree that ARC service is not what it once was. 

OMG, elizabeth agreed with Atmasphere!

So- the chip can't be bypassed?
If its a fire concern, couldn't a thermal fuse be installed?
*IF* that's all that's wrong, sounds like a simple matter to sort out, if all that is needed is to just get it running again.

ARC now is owned by Big Mac, so- I can understand why they want everything you own, to be obsolete. Gotta buy more of that high-Dollar real estate! ie: https://worldofmcintosh.com/  and: http://www.audiophilia.com/reviews/2018/1/25/world-of-mcintosh-loudspeaker-unveiling

@stereo5 - The oldest that amp can be is 11 years(unless the ARC database is mistaken). It was discontinued in 2010, so- it could be less than 10 years old. NO EXCUSE! http://www.arcdb.ws/SD135/SD135.html 

McCormack is reputed to match well with Vandy speakers.  Here's an upgraded DNA-1 at a good price that should have plenty of power for your 3As.  Best of luck in whatever you decide. 

https://www.usaudiomart.com/details/649468342-mccormack-dna1-w-smc-silver-mods/

Get a Pass amp great sounding bury the ARC at sea say goodbye.

Certainly AR knows how to do it, but won’t. They prefer to sell another amp over helping a customer enjoy their current AR amp for many more years. I think this is a reflection of the company’s culture and attitude.

I have read so many stories about Audio Research amps not being repairable or frequent repairs I would never buy one.  

A good tech/modifier could fix this amp. You simply need a new way of handling the protection circuit in your amp. No way your amp is now trash. Are you near any good tube amp builders or techs?

I think AR should fix this this amp by utalizing the type of creativity and effort mentioned above. Poor answer IMHO. Shows no real effort to think this through for their customers.