Transistor popped? Did you check any of the resistors? Are the SMD resistors large enough to handle the task? I saw another thread using all 1% 1w resistors and MJE340/350 in lieu of the transistor that may become obsolete. Still using the FET2sk370 pair in AM-1
I think the MJE340 are more robust than the original
I think the MJE340 are more robust than the original
Hi, DeafbyKhorns,
In this thread, the resistors should be 1/2W, and that's what I'm using. They measure the same after the module failed, I haven't checked all of the transistors to comment on their junctions. I'm not worried about any of the devices going end-of-life, Digi-Key and Mouser still list them as Active as opposed to Not for New Design, and Linear Systems is still in production as a FET supplier. What's weird for me is one of the AM-2 modules had a roll-off starting at 2KHz and then died. None of the resistors are discolored or have changed in value. I'm in and out with a temp controlled Weller in 2-3 seconds, and really haven't had a soldering problem in decades. Could I have fried a x-istor - of course, just puzzling. Could there be bad / fake parts - doubtful from these suppliers. So why a roll-off with parts with a BW of 5MHz? The test fixture & gear show a good AM-2 still plays out past 1 MHz, so I don't think that's flakey. Waiting for new parts and will do another build is all I can offer now.
Cheers,
Frank
In this thread, the resistors should be 1/2W, and that's what I'm using. They measure the same after the module failed, I haven't checked all of the transistors to comment on their junctions. I'm not worried about any of the devices going end-of-life, Digi-Key and Mouser still list them as Active as opposed to Not for New Design, and Linear Systems is still in production as a FET supplier. What's weird for me is one of the AM-2 modules had a roll-off starting at 2KHz and then died. None of the resistors are discolored or have changed in value. I'm in and out with a temp controlled Weller in 2-3 seconds, and really haven't had a soldering problem in decades. Could I have fried a x-istor - of course, just puzzling. Could there be bad / fake parts - doubtful from these suppliers. So why a roll-off with parts with a BW of 5MHz? The test fixture & gear show a good AM-2 still plays out past 1 MHz, so I don't think that's flakey. Waiting for new parts and will do another build is all I can offer now.
Cheers,
Frank
Used some gerber files from a user on another forum. They had several mistakes, pins were in the wrong place, transistor silk layer orientations wrong so starting from scratch...
I called it out and the thread mysteriously disappeared. 
Attached the gerber, I properly labelled the emitter
The other attachment is component layout for audio research motherboard (these work with several amps), compare it to gerber and its obvious the pinout is wrong.
At this point, I'm going to teach myself to use EasyEDA and do it myself unless someone wants to share a gerber (that works).
I called it out and the thread mysteriously disappeared. Attached the gerber, I properly labelled the emitter
The other attachment is component layout for audio research motherboard (these work with several amps), compare it to gerber and its obvious the pinout is wrong.
At this point, I'm going to teach myself to use EasyEDA and do it myself unless someone wants to share a gerber (that works).
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I have to ask you guys why you even want to.bother to fix these early ARC solid state amps? Is it just for the exercise or to improve the sound quality? They sounded awful back when they were brand new, I worked for an.ARC dealer back then! Its a nice chassis, but I'd be building some other amplifier in it...
Mark
Mark
Its more about the learning experience. I know the SP4 and the D100 pair are mediocre but they are fine for an office system. My GM70 monoblock amps are what I use in my 2channel high end system.
BTW, got the bad boards working after cutting bad traces and making jumpers so will be making some revised boards for anyone that wants to get your gear back up and running.
The MJE340/350 combo work great.
Moral of story, don't trust anyone elses gerber files unless they built and tested them....
BTW, got the bad boards working after cutting bad traces and making jumpers so will be making some revised boards for anyone that wants to get your gear back up and running.
The MJE340/350 combo work great.
Moral of story, don't trust anyone elses gerber files unless they built and tested them....
I fixed the gerbers and made it much easier to stuff the parts. I have the gerbers if interested, takes about 5 days from China and will cost less that 20 bucks (shipped) for 10 boards. I have both modules done now.
Will also share the project from Mouser, they have all the parts except for the JFets (Get them from DIY Audio Store). Used all precision 1% resistors, I had near zero offset after testing.
Will also share the project from Mouser, they have all the parts except for the JFets (Get them from DIY Audio Store). Used all precision 1% resistors, I had near zero offset after testing.
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