2. amps-preamps
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ARC SD135 will not turn on -- fearing the worst

Yesterday my Audio Research SD135 power amp failed. I turned it on, and the amber protect light quickly turned to green---and then winked out. Then, nothing. Replacing the fuse changes nothing. I have an old ARC D130 that I was able to swap in; it and the rest of my system are working fine.

I sent an email to Audio Research service.  Actually, I replied to a previous note from them about the service they were performing on this same amplifier.  A few years ago, they replaced a bunch of parts and sent it back, and the amp has seen only light use since then.  In his note, Kalvin mentioned problems with the ThermalTrak transistors.  I noticed a recent thread that claims these parts are no longer being made.  And Kalvin has retired.  I hope ARC can do something for me.  Any suggestions?

By the way, my power amp is fed by an ARC LS 27, and the speakers are Vandersteen Treo.

rach_fan
rach_fan OP
25 posts
 
Here's a thread from two years ago, about another broken SD135. In this poster's case, ARC gave him a credit toward a new amp. The thread discusses the ThermalTrak transistors, which had been discontinued. There's a new version of those parts, but it's not compatible with ARC's design. Apparently, ARC never found a workaround using the new versions of the parts.

https://forum.audiogon.com/discussions/my-amp-is-broken-not-sure-what-to-do-any-recommendations/post?highlight=sd135&postid=1637744#1637744

ARC service suggested that used ARC models D240, DS225, DS450 might be of interest. Perhaps a used Ayre power amp might also be a candidate. My preamp is an ARC LS 27, and the speakers are Vandersteen Treo.

Thanks!
rach_fan OP
25 posts
 
I would like to hear from anyone who has replaced the ThermalTrak transistors recently.  My tech tells me that replacement parts are entirely compatible with the original amp design:

The type # changed slightly, from NJL3281D & NJL1302D to NJL3281DG & NJL1302DG, to signify lead free.  This simply means the solder used to "pre-tin" the device pins is no longer lead/tin blend.  There was NO other change to device.

But I heard a second-hand account from a Mcintosh tech that they had several amps fail because there was indeed a difference between the leaded and non-leaded devices.

So is there more to this story than just the part numbers?  It would help to have validation from someone who had repaired an SD135 recently.

Thanks...

rach_fan OP
25 posts
 
Regarding ARC's product suggestions to me, has anyone compared the SD135 with its class-D successor, the DS225?  

I'm not sure about the class-D.  But the DS225 has a lot more power supply energy storage going for it, and no overall negative feedback, according to https://www.arcdb.ws/model/DS225

I'm also interested in Nakamichi Stasis amps, although I haven't seen any comments about their use with Vandersteen speakers.

rach_fan OP
25 posts
 
Hmmm.

But the DS225 has a lot more power supply energy storage going for it
But notice that the manual for the DS225 lists "OUTPUT CURRENT: 15 amps peak at protective shutdown."

The manual for the SD135: "OUTPUT CURRENT: 60 Amps peak (1 millisecond)"

Not what I expected, give the power supply in the DS225.
tomic601's avatar
tomic601
12,911 posts
 
The DS. is class D
Ayre used the On semiconductor ThermalTrac devices, giive themm a call they may have an opinion on new part number...BTW the thermal trac in my Ayre failed also....
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