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Energy-Onix SST-30 exciter (rebranded RVR?) troubles

S

stephend2

I have this exciter here, looking for manuals for it or at least some tips.

It is producing spurs all over the band when operated at anything less than full power (30 watts) It cleans up well at 30w, sounds like crap and causes a lot of trouble at anything less, which is a problem being that I only need about 16w out of it.

This particular unit was manufactured in 1997, I figure its time for a going through.

Any ideas on the cause, or at least a pointer in the direction of manuals and schematics?
 
My guess - open bypass electrolytic in the PA. Saw the exact same symptom in a earlier, not very old at the time, PTek.
 
Many times an electrolytic is called upon to bypass both low frequency ac (audio) and high freq ac (rf).
They are "OK" at this when new, but big electrolytics simply aren't' well designed for rf bypass.
As they age, they can still be just fine at line (60 hz) frequencies but no longer pass higher ac very well.
In 5 tube "all-american" receivers, comptetion for pricing resulted over the years in elimination of "needless" parts,
to the extent that one big filter cap was bypassing rf returns for all the screen grid supplies, and as the filter cap aged, intermod birdies showed up all over the dial, and eventuially within the passband of desired, average strength signals.

Good design really does include a .1 mfd cap or so in parrallel with any large "filter" electrolytic, if there's rf anywhere
in the circuit.


Ideal design provides a short, meaningful bypass for rf currents from each point that would be desirable to isolate.
More expensive, but tends to work for decades instead of mere years.
 
There are either two or three 47 uf/50 volt radials on the B+ rails on the power amplifier board.

You need to replace these.

Also, unless it has been recently recapped, replace the filter caps and other electrolytics on the power supply. The power supplies seem to be different in every one of these exciters I've looked at. Some parallel a number of 1000 uf caps, some use snap-in higher valued caps that are difficult to replace. I have installed computer grade cans & run leads over to the power supply in those models.

Another thing I've tried is to reverse the direction of airflow. As built, they pull air in from the vented top and exhaust out the back. Reversing the fan pushes cool air across the PA and power supply.

The power supply regulator (an MJ3001 or NTE245 as I recall--a Darlington) runs hot. It is designed to reduce the B+ to the final transistors as a means to control power output. Hence it produces more heat if required to reduce the voltage for a lower output than the 30 watts nominal output. The spurs, then, may reflect leaky caps in that part of the supply.

I have schematics and manuals, the schematics, however, look like they've been faxed from RVR. Bernie at Energy-Onix can sell you a manual for about $30; I scan send you scans if your mailbox will accommodate big PDF's.
 
Tom,

I would appreciate any manuals or schematics. I spoke to Bernie today, he did not seem interested in sending me anything, insisting that I send the unit to him for repair.

you can send to stephen (at) newbreakcommunications.com that box should accept large attachments with no problem.
 
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