Eden WT-550B

[lowell]

I've searched on here and elsewhere for the 550B power supply, layout, schematic etc... Got one in with distorted output, even going into the return jack.

There is a disconnected wire in the power supply, both ends, with clips, disconnected, and zip tied with a bundle of other connected wires. It may be that way from the factory, not sure. There are two pcb clips that are empty near it, one is mains earth, and the other has a blue wire from the PT primary connected to it. Is possible this wire is there for 220v conversion I guess, but wanna know.

I emailed Eden, but they do say on their site they only deal with warranty shops.

Any help appreciated. I'll check the supplies meanwhile and see if anything jumps out as obvious, but would really like to know about the wire.

[lowell]

Main rails are +/- ~78/79v. There is no Vbe voltage, so seems maybe they're biased too cold. Unless I'm missing something, maybe it's class B? They're 2SA1294/2SC3263.

[Enzo]

By clips do you mean connectors? To me a clip is the spring loaded thing on the end of a test lead. Alligator clip.

The Eden documentation I have seen tends to be minimal anyway, no mains wiring.

[lowell]

Yes connectors, correct. Ok thanks. I'll investigate this bias issue.

[J M Fahey]

Excellent amplifiers, created by a very gifted designer with his own strong ideas very much as if it were a 1 man boutique shop; that includes hand drawn schematics in a somewhat unusual format.
AFAIK he was a business partner of SWR´s Stewart Rabe, he dealing more with the speakers, while SWR was more into the Electronics side; when they split SWR had to use other speakers, most notably PAS, in any case both brands have a very similar design philosophy an originally catered for the same type of Bass player, specially advanced Fusion type ones.
Both brands aim for very wide range, clean and loud sound, not your average Ampeg.
Doubt they make speaker cabinets without horns or tweeters.
I have a couple schematics, maybe the 550 or some close version, will search and post it here.
The power supply is "hidden in plain sight" , not drawn separate but as if those were tiny decoupling caps ... until I noticed that at, 6800uFx80V or some such large value they were way more than that.
Not Class B so if you measure no drop across the emitter ballast resistor, they are either underbiased or broken.
Do NOT mess with mains wiring, an unused wire and 2 empty clips is exactly what´s needed to put 2 x 120V windings in series to turn transformer into a 240V one.
Besides, I know of no failure mode which implies wires self disconnecting and self tying , maybe they got into some kinky S&M???

[J M Fahey]

I found a couple, except 550B ; no big deal because designers tend to repeat their pet ideas, so some other might be very close.

Only doubt: I found MosFet and Bipolar versions, please post type and quantity of power devices.

Those I found range from WT400 to WT800.

[Jazz P Bass]

Here is what documentation I have: WT550 - Schematic (May 2004).zip

[lowell]

JM yeah everytime I get inside one of these I can feel the integrity of the designer. It's very well built, clean, and sturdy. (That's what HE said?)

Thanks guys. I posted in my second post that the outputs are 2SA1294/2SC3263 bipolar types. 3 of each.

I wasn't aware that drivers could be bad, and not have caused a larger failure. Is this a rather common failure mode? Or could this be on "odd" one.

Thanks I'll check this zip file out!

[lowell]

There are 2 LEDs in the PA. They have a trim pot (trim3) for adjusting thermal compensation. The trim is across both LEDs and seems to adjust the input transistors' Vbe. My guess is this is adjusted so that the input transistor bases sit at 0v. Am I right?

[lowell]

Ok I've replaced the drivers. I don't think that was necessary as they were fine out of circuit. Anyway it's done. Still same issue. Here's what I've confirmed is good:

voltage rails
driver transistors Vbe are +/- 1v (referenced to ground)
output transistors checkout good with meter
output emitters to output show continuity
emitter resistors are good

I cannot get 4mv across emitter resistors
I connected a 4ohm load, and was able to get 4mv across NPN outputs but 0mv across PNP outputs
output Vbe (npn) +470mv (pnp) -248mv

I'm at a loss as to what is happening here.

[lowell]

I realized that even though I have -248mv Vbe on the PNP driver, that the collector voltage could be off. Indeed it was 200mv. Not the 4.7v dictated by the zener. I checked the cap and zener and the zener was shot. FIXED!

[Jazz P Bass]

Woo Hoo!