Help! Save my Sumo "The Power" power amp.

[Bill Fitzpatrick]

Put it up on ebay. I had 2 of those, also not working right, several years ago and sold them on ebay for $300 each. As I remember, the buyer was in Japan and he didn't mind paying the expensive shipping and professional packing from the U.S. He might see your auction and want another. You might get more because you are nearby, shipping wise, to him.

[johnkramer]

when you do pass it on, please try and get it to someone who will appreciate it for what it is. Sure it'll make a nice sub amp, but that would be like using a corvette to tow a trailer. It would be a shame to get it to someone who doesn't know its full potential.

From what I recall, James intended the amp for high power ESL's. THe rumor mill at the time suggested he designed it specifically for the Dayton Wrights (the only high power, high spl ESL that I can think of) In fact, The Power has the same panel size as the Dayton Wright PS unit. They really did look impressive together.

The manual was pretty specific that it needed its own leg off the AC power mains. Preferably as close to the entrance as possible (first circuit breaker)

I also remember a brag in the manual. "100% stable into any load angle whether inductive or capacitive, regardless of waveshape".

Another thing to consider, it is a fairly modular amp, it could be broken down and shipped in pieces, but that is just an assumption. I really don't remember too much what it looks like on the inside or how easily it could be broken down. Care to open it up and take some pictures?

I really wish I could make an offer to you (by the way, I've been to Singapore, lovely place). But I really can't shell out the funds and I am not in any position to use it well. It is my personal favorite amp of all time and there is a bit of envy

It idled class A and ran as such up to a point, but I can't remember how far.

Originally posted by destroyer X
It is class A, the wonderfull sound you told made me think in class A.

And the power consumption is around 450 to 500 watts... consumption, not output in this one.

Is made in USA and put 70 plus 70 RMS power output in 8 ohms.

I remember it being a 450watt/channel amp, never advertised as a class A design. ALthough it did run class A from idle up to a point. Full complemtary differential design from input to output. THe idea was to deliver lots of power to difficult loads.

I think it was "The Gold" that was true class A. It was the same size as the Power and something like 70watts/channel.

[Chris Dian]

Here are the pictures John....

Regards
Chris.

[computeruser]

About a year and a half ago, I, too, was given one of these because it had the same symptoms as the original post - It would pop in one channel and usually blow the woofer.

James Bongiorno does frequent the Yahoo SAE forum and he was very helpfull in my getting it re-built but he did suggest I send it to
one of his technicians to have it repaired. He will not give out the schematic for this unit. I chose to go at it on my own mostly because of the cost of shipping it to be repaired - it must weigh 90 lbs and also not knowing if the amp was worth even repairing sonically. Most high power amps of that era did not sound all that great. Well...It WAS worth repairing..and the unit has now been running in my system for almost a year with no problems at all. The amp it replaced in my system was a Sumo NINE which up to that time I thought was the best sounding amplifier I had ever heard. The Power sounds even better.

What I can do - if people are interested - is post a summary of all the work I did inside the unit. (I kept a log) It IS modular in construction and what I did was swap these modules from the working channel to the faulty channel in order to track down where the problem was. James provided information to upgrade the op-amps and caps and how to set the DC balance (very critical). The problem turned out to be a cold solder joint. The only way even found this was once I had narrowed down where the problem was, I unsoldered each component on the suspect board and measured it.

This amplifier was built in 1980 around the same time as the "Gold" but before the "Nine" and retailed for $3000USD. James estimates that if this unit were to be produced today (taking into consideration same build and parts quality) it would retail for between 15K and 20K USD.

[Zero Cool]

I put one of these MONSTERS into a large Home theater system running a modified pair of JBL L300 studio monitors i built for a client in Dallas TX. One day POP, smoked the H*ll out of one of the freshly reconed JBL 15" woofers. 90VDC on the speaker outputs!

Yes these babies are 400+ watts per side @ 8 ohms and there built Monoco style. IE, the entire thing is built around the mosterous I-E core power transfomer. each channel is a bridge in balanced operation if i remember correctly with some very complicated servo circuity. I remeber trying to trouble shoot that beast and just trying to move it around the bench to get at various parts required huge amounts of effort. and in the end. we ended up scrapping it. Just way to difficult to repair without a schematic.

all of the output devices were fine, there was some sort of problem in the servo system that was driving one side of the outputs to the rail. I spent about 2 months trying to get that dang thing running and never made any progress.

Zero

[redl123]

I don't know if you still have your Sumo if so ther is a company in California called Cullen circuits and Rick repairs and upgrades these amps.

If you would want to sell it I would be interested. Pete