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Energy-Onix/Bext/RVR 30 Watt exciters.

T

TomT

Basically the same exciter made by RVR, but re-branded and sold with a new front panel by the other folks.

Just rebuilt an older Energy-Onix that fried when the fan died (see SST-30 thread), also have a BEXT 30 watt in service that is very similar.

Here's a tip for folks with these exciters. Look into reversing the fan so it blows INTO the exciter. I did it on
both of these exciters and it seems to help with the cooling. On the Energy-Onix you will need to be careful on routing the AC leads from the fan since they will now come off the back of the fan. On my Bext 30 watt I replaced the original 12 volt fan with a 110 volt Papst fan, like the Energy-Onix uses.
 
TOmt - or whomever was ooking -
I made a .pdf of the Nicom book. Give me a valid email which will accept attachemtns and I'll send it.
 
Either TPT at LiteRock93R.Com or TPT at Eurekanet.com

Both should take attachments-- "at" of course is @
 
[email protected]
I have a ENERGY-ONIX SST-30 looking to fix the 30 watt amp, gets a good watt without one, and the meter lied saying at first REV PWR was pegged, then later after wiggling all the cabling and setting the ribbons. I get a little less going from the Mother board thru the PA, trouble is I need 25 watts to drive my 100 watt amp. Right now a cheap $50.00 transmitter will get some amplification but only about 20 watts out as it is linear. I get signal from mb to amp but not enough to start the 100 watt amp. Any schematics would help
 
systemdump said:
[email protected]
I have a ENERGY-ONIX SST-30 looking to fix the 30 watt amp, gets a good watt without one, and the meter lied saying at first REV PWR was pegged, then later after wiggling all the cabling and setting the ribbons. I get a little less going from the Mother board thru the PA, trouble is I need 25 watts to drive my 100 watt amp. Right now a cheap $50.00 transmitter will get some amplification but only about 20 watts out as it is linear. I get signal from mb to amp but not enough to start the 100 watt amp. Any schematics would help
Click to expand...


Wow. Big pause from 2009 to 2011. Since the VWSR meter is pegged, have a look at the VSWR circuit. It's probably a bad opamp causing the amp to think there's real VSWR when there isn't. The power is thus folded back to near zero.
 
Try that, also look at the Darlington that controls the power amp. (Mj3001?? going by memory) My Bext version of this exciter seems to show high VSWR all the time, but still puts out full power (as in what VSWR foldback?? :) ).

I'll try to find my SST-30 book..send me an e-mail address (mine is above) and I'll get you a PDF in a day or two. Be aware that everyone one of these exciters are slightly different & the schematics are not very good.

BTW--local college has an SST-30 they would probably like to sell. Has been recapped, but the crystal on the main board drifts--hence doesn't like a cold environment. Suspect there is an easy fix (like one of those Dale resistors or a small light bulb--the crystal heater is just some sort of resistor). If your interested make an offer & I'll pass it on. Their station GM works for me on weekends.
 
There is a big transistor next to the big PA brick, on the right with a loose green wire. Old school huge transistor, next to another mounted upside down so leads are facing straight up. I reboot the machine holding the green lead taught, it shows 30 watts swr, not forward power, maybe it's a protection circuit gone bad. Thanks to all for your help on this gremlin.
 
systemdump said:
There is a big transistor next to the big PA brick, on the right with a loose green wire. Old school huge transistor, next to another mounted upside down so leads are facing straight up. I reboot the machine holding the green lead taught, it shows 30 watts swr, not forward power, maybe it's a protection circuit gone bad. Thanks to all for your help on this gremlin.
Click to expand...


SWR detection is usually done by a very small diode driving a low power circuit. No big parts are involved the actual detection. You should check the path from the final transistor to the antenna connector to make sure it is good. There could be real SWR inside of the box. Also, remember to always keep the exciter connected to a known good 50 Ohm resistive load during testing.
 
One of the big "transistors" is the Darlington, the other (on some models) is a 3 pin regulator. Both mounted on a heat sink attached to the power supply, to the right of the PA amplifier, looking at it from the front.

You may need to get an external wattmeter (e.g.--a Bird, or even a ham-style one like an MFJ wattmeter) to see if this thing is putting out any power. And, of course, a good dummy load.
Since the metering on these things can be flaky, you won't have any idea otherwise what is actually going on.

BTW--my Bext version will show high vswr with 25 watts out.... measured on a wattmeter, there's next to no reflected. This was in an installation where the antenna was about 15 feet away from the transmitter (translator with the antenna mounted on the side of a barn).
 
I have a 150 watt E-O for my backup stick at the old site on campus. I've heard several people say that if the fan quits, all heck breaks loose on these units. Does anyone have some mods theyve done to the unit to add protection from overheating due to fan failure?
 
Most of the earlier RVR units had pretty good fans--good Pabst ball bearing units. Of course, like anything mechanical, eventually they die.

Some of the newer units--Armstrong's version of the exciters and STL transmitters, use little $10 DC fans. Need to be watched--I've replaced one already with a Pabst (same size--but you need to find a place to pull the AC from.

Most of these units have an interlock circuit on the power supply (sometimes a BNC connector on the back). Shorting it kills DC. Could be used for an over-temp circuit if the unit is going into a challenging environment.
 
Unless it is shorted to ground wouldn't be the problem. Going by memory it goes to one of the inputs on the 723 IC, shorting to ground kills (ramps down) the DC to the power amp.
 
Re:I have the older Nicom FM-30

my exciter has full power all the time as the pass trans shorts and a 10 amp trans seems to fix that I would like a dig of all this if you pass it along thanks Allen
 
That's the Darlington gone bye-bye. Circuit works by using the Darlington like a resistor power divider, with the 723 IC setting the "divide" point. Normal operation, if the exciter is set for half power, the Darlington sinks part of the PA B+ to ground to get the output down. When the Darlington fails, the output goes full.

Most used the MJE3001, there is an NTE replacement, although some distributors still carry the original.
 
systemdump said:
I need 25 watts to drive my 100 watt amp.
Click to expand...

25 watts to get 100 watts out? The PA isn't very efficient! Most PAs only need 5 - 10 input watts for full power.
Something wrong with the PA?

TomT said:
That's the Darlington gone bye-bye. Circuit works by using the Darlington like a resistor power divider, with the 723 IC setting the "divide" point. Normal operation, if the exciter is set for half power, the Darlington sinks part of the PA B+ to ground to get the output down. When the Darlington fails, the output goes full.
Click to expand...

Hmmm... not the most ideal way to produce a LV rail. Inefficient (a lot of power wasted as heat) and not a good situation if it fails and the rail goes to full voltage.
There are plenty of variable linear regulator circuits around, including those using mosfets and/or PWM. Why couldn't they have used one of those?


It reminds me of a TV power supply I saw once. The circuit was pretty basic. The chinese obviously wanted to reduce the component count.
The main HT rail was switched to the rest of the set using a relay. When you hit the ON button on the remote, the relay pulled in and powered up the set.
When you hit it again, the relay opened and the set shut down, but not completely. The power supply was still running!

Problem was, when the relay opened, the now effectively unregulated supply went high, to about 180 volts.
It was only when the relay closed, and a load applied, that the supply actually came down to sit at 130 volts which is what the nominal output was supposed to be.

As you can imagine, every time the set was turned on, 180 volts was applied to everything until the load could pull it back down to 130 volts. This stressed every component in the HT stage and it was no wonder the sets didn't last.
 
Depends on the design considerations. Same system was used in the Continental 802A/802B exciters, as well as the BE FX-50. All three were designed to run at 25 watts or more to drive the next stage in high power transmitters.

For example, the 802A was designed to work with early 816R transmitters, which had 3 db of attenuation between the exciter and the IPA input in order to provide a stable load to the exciter.
 
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