Swr sm900 schematic

[Boneless]

But in fact, it makes more sense to use genuine current-production parts and make the necessary modifications to make it work. To test your luck and buy "genuine" parts off eBay makes little sense.

 

[agedhorse]

But in fact, it makes more sense to use genuine current-production parts and make the necessary modifications to make it work. To test your luck and buy "genuine" parts off eBay makes little sense.

Part of the problem is that the unique output transistor package had as about as much thermal dissipation capabilities as a TO-3 metal package... that's what made it a good choice for this type of application, plus it had really nice gain-bandwidth performance.

 

[Boneless]

Part of the problem is that the unique output transistor package had as about as much thermal dissipation capabilities as a TO-3 metal package... that's what made it a good choice for this type of application, plus it had really nice gain-bandwidth performance.

But if the alternative is to scrap an amp that is otherwise worth saving (for instance, here we're talking about a bi-amp head, right? Which is somewhat rare), that's when you might consider either modifying the PCB and/or heatsink to accommodate a transistor in some other package (yes, a big problem is that not many devices are available today that can do the job) or just use another power amp. Like, I wonder what techs do in places where repair, redesign and re-use still makes sense. I don't think there is much distribution for audio amplifiers of any kind in rural Ghana. Or, in a more developed part of the world, New Zealand. (AFAIK they have a hard time getting any sort of equipment, and whatever is there costs an arm and a leg).

 

[agedhorse]

But if the alternative is to scrap an amp that is otherwise worth saving (for instance, here we're talking about a bi-amp head, right? Which is somewhat rare), that's when you might consider either modifying the PCB and/or heatsink to accommodate a transistor in some other package (yes, a big problem is that not many devices are available today that can do the job) or just use another power amp. Like, I wonder what techs do in places where repair, redesign and re-use still makes sense. I don't think there is much distribution for audio amplifiers of any kind in rural Ghana. Or, in a more developed part of the world, New Zealand. (AFAIK they have a hard time getting any sort of equipment, and whatever is there costs an arm and a leg).

If the repair is going to be unreliable, the real question is how to support the cost of repairing again and again. I learned a long time ago that once you repair something, you kind of become married to it for the warranty period. If you don't offer a warranty, and don't stand behind your work, customers can take unreasonable actions. Maybe your experiences are different than mine.

Repairs in rural parts of the world are generally really unreliable, but that's accepted as "ok" because there is no alternative.

 

[keyboards0822]

I have some parts for the SM900's in stock. I also have the schematics for it. For some oddball reason although I have an account here on TB, it won't let me log in and because I've used the email address before it won't let me re-register

 

[keyboards0822]

Good day
Well, my swr sm 900 had a major failure, I'm in need of the schematics for the amplifier.

Not exactly shure what happened but it took out 6 ic's. Tech replaced them but still no go. I can't explain what the tech told me exactly, but he's dumbfounded as to what's going on.
Anyone have the schematic for this amplifier? This is going to be a expensive repair, but the guy is super cool and not charging me for lots of time spent trouble shooting it.

Deenah, do you have the blue board or tan board version of the amp? I've got both schematics. Matter of fact I just redid a blue board not long ago.

 

[keyboards0822]

If the repair is going to be unreliable, the real question is how to support the cost of repairing again and again. I learned a long time ago that once you repair something, you kind of become married to it for the warranty period. If you don't offer a warranty, and don't stand behind your work, customers can take unreasonable actions. Maybe your experiences are different than mine.

Repairs in rural parts of the world are generally really unreliable, but that's accepted as "ok" because there is no alternative.

One thing I've always done is put the amp through hell before it leaves my bench. Depending on the specs and design I'll run 1KHz sine @ 50-80% of full power for 30-45 minutes into a load cell. If it doesn't fail then, it probably won't at the gig. It's worked for me for the past 35 years.

 

[agedhorse]

One thing I've always done is put the amp through hell before it leaves my bench. Depending on the specs and design I'll run 1KHz sine @ 50-80% of full power for 30-45 minutes into a load cell. If it doesn't fail then, it probably won't at the gig. It's worked for me for the past 35 years.

Are you using factory correct Sanken parts or the currently available counterfeits and knockoffs?

 

[baxter_x]

Depending on the specs and design I'll run 1KHz sine @ 50-80% of full power for 30-45 minutes into a load cell.

Why is this putting the amp "through hell"?
Why specifically this frequency?

 

[Juan M]

Jumping in here as I own a very well kept sm400s and bass 350 and curious about what you think regarding the mentioned knockoffs. Do they work well enough (in your opinion) to make them worth the time - even if they do not offer the same degree of longevity, durability, quality etc. I love the idea of keeping my amps going for as long as possible, even if that means replacing them with slightly inferior parts if need be. My question is - just how inferior are they, and would they be so poor in quality that it would lead you to shelf the project entirely? Thanks for your input (or anyone else who cares to share from direct experience).

 

[agedhorse]

Often they are bad enough that they self-destruct. This is after putting a bunch of labor into them.

There are some TO264 style parts that will work, but they all need to be changed and new mounting holes drilled (carefully). This is not always possible though.

 

[keyboards0822]

Why is this putting the amp "through hell"?
Why specifically this frequency?

Full sine wave is more abusive than just playing music through it. Running it continuously for 20-30 minutes on a sine is more abuse than almost any player could give it on stage. The frequency is just a standard frequency for audio testing. I also do a swept frequency test to make sure nothing went south in the preamp or EQ circuitry.
I guess I would call it "stress testing". Have things gone south doing this? YUP! Was my client happy it blew up on my test bench instead of his gig? Oh HELL yes!
Oh yeah and ALL my repairs come with a 180 day warranty on the repair performed. It's doing business the way it used to be.

 

[agedhorse]

Full sine wave is more abusive than just playing music through it. Running it continuously for 20-30 minutes on a sine is more abuse than almost any player could give it on stage. The frequency is just a standard frequency for audio testing. I also do a swept frequency test to make sure nothing went south in the preamp or EQ circuitry.
I guess I would call it "stress testing". Have things gone south doing this? YUP! Was my client happy it blew up on my test bench instead of his gig? Oh HELL yes!
Oh yeah and ALL my repairs come with a 180 day warranty on the repair performed. It's doing business the way it used to be.

Some of us still warranty our work.