The Energy Onix Pulsar transmitter

Engineering Radio: The Oh Dear God Edition.

I have been tasked with fixing one of these glorious contraptions. Aside from the usual Energy Onix quirks; design changes not reflected in the schematic diagram and a company that no longer exists, it seems to fairly simply machine. Unfortunately, it has spent its life in less than ideal operating conditions.

Energy Onix Pulsar 1000 in the wild. Excuse the potato quality photo
Energy Onix Pulsar 1000 in the wild. Excuse the potato quality photo

Upon arrival, it was dead in the water.  Found copious mouse droppings, dirt and other detritus within and without of the transmitter.  Repaired the broken start/stop switches, fixed the RF drive detector, replaced the power supply capacitors and now at least the unit runs.  The problem now is the power control is unstable.  The unit comes up at full power when it first switched on, then it drops back to 40 watts, then after it warms up more goes to about 400 watts and the audio sounds distorted.  This all points towards some type of thermal issue with one of the power control op amps or other composite device.

After studying the not always accurate schematic diagrams, the source of the problem seems to be carrier level control circuit.  This is based around a Fairchild RC4200AN (U10 on the Audio/PDM driver board) which is an analog multiplier chip.   That chip sets the level of the PDM audio output which is fed into the PDM integrator circuit.  Of course, that chip is no longer manufactured.  I can order one from China on eBay and perhaps that will work out okay.  This all brings to mind the life cycle of solid state components.  One problem with the new technology; most solid state components have a short production life, especially things like multiplier chips.  Transmitters are generally expected to last 15-20 years in primary service.  Thus, transmitter manufactures need to use chips that will not become obsolete (good luck with that), or purchase and maintain a large stock of spare parts.

In the mean time, the chip is on its way from China.  Truth be told, this fellow would be better off with a new transmitter.

8 thoughts on “The Energy Onix Pulsar transmitter”

  1. I had a similar situation about three years ago. You tell the owner that the company is no longer in business, there are no parts readily available and the transmitter needs to be replaced. The guy I was working with understood and a brand new Nautel was ordered post haste. That and some quick antenna matching had that owner thinking I hung the moon, he paid me in full before I left after installing the new Nautel! The down side to this situation with the EO is you will get it back up and running THIS time and the owner/GM will expect you to be able to pull a rabbit out of your hat EVERY time it goes down from here on out.

  2. AM in Boise has been off the air since June 24th. They have a Pulsar 5. Meanwhile, their translator plays merrily on.
    This guy’s a mini- Brian Dodge.

  3. “I have been tasked with fixing one of these glorious contraptions.”

    Having BTDT, all I can say is I’m sorry. 😛

    I’m fighting the same issues with a different brand- Omnitronix.
    those “world standard” “easily obtainable” parts have a production lifespan much shorter than the transmitter itself.
    It should probably be standard practice to purchase a 100% semiconductor spares kit when any solid state transmitter is installed and put it away somewhere. Often can be done for not much money. Of course needing time machines and all at this point.

  4. Paul… I

    I thought I had one to give you…

    But I think it has the same problems yours has. Like you I just got it dropped in my shop (again) to be repaired.

    I can get this one to 250 W with the power control full on. I haven’t got into it enough to see if the power supplies are down or PA transistors are bad but, it passes distorted audio… Contact me as I could use a little help. This is the first one I’ve seen. I have a couple of places to start but, like you I’d like to finish it ASAP.

  5. We can fix all of Bernie’s boxes, and source parts and can provide some tech support on the phone. Contact me if we can help.

    Mike Patton
    Michael Patton & Assoc
    225-266-9745 cell

  6. I’ve been keeping one of these Pulsar 1000s on the air since 2013. So far it’s been power mosfets going out. Good think they are cheap! I’ve put in lots of them. Currently have a problem with power module No. 2. New mosfets don’t seem to fix the problem!

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