AM transmitter – Engineering Radio

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 simple 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 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 is 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 another composite device.

After studying the not-always-accurate schematic diagrams, the source of the problem seems to be the 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 manufacturers 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 meantime, the chip is on its way from China. Truth be told, this fellow would be better off with a new transmitter.

Decommissioning transmitters

I was at a transmitter site a few days ago scrapping a Continental 814-R1 transmitter and started thinking (always a dangerous thing) about how many of these units I have decommissioned over the years. It turns out, quite a few:

Make/Model	Year new*	Year removed	Station	Disposition
GE BT25A	1948	1994	WPTR	Donated/scrapped
Gates BC5P	1960	2004	WWLO	Donated
Harris MW5A	1982	2000	WLNA	Scrapped
Gates BC1T	1961	2001	WLNA	Donated
Harris FM20H3	1972	2001	WYJB	Scrapped
RCA BT1AR	1960	2001	WROW	Donated
Harris BC1G	1972	2001	WDFL	Abandoned
Harris FM20H3	1971	2005	WHUD	Scrapped
BE FM30A	1988	2005	WHUD	Cannibalized
Harris FM5G	1972	2008	WSPK	Scrapped
Mc Martin BF3.5K	1976	2011	WCTW	Scrapped
RCA BTF-10ES	1978	2011	WRKI	Scrapped
Gates BC1T	1964	2011	WINE	Scrapped
Continental 315F-R1	1985	2013	WVMT	Donated
Collins 813F	1975	2014	WKXZ	Scrapped
RCA BTA1AR	1965	2014	WCHN	Scrapped
Collins 813F2	1978	2015	WKXZ	Scrapped
Collins 830D-1A	1968	2014	WKXZ	Scrapped
Harris FM20H3	1972	2013	WYJB	Scrapped
Harris BC5HA	1973	2013	WROW	Scrapped
Harris FM10H	1971	2013	WMHT-FM	Scrapped
Harris FM2.5H3	1973	2015	WEXT	Scrapped
Mc Martin BF3.5K	1972	2014	WSRK	Scrapped
CCA FM5000G	1980	2015	WTBD	Scrapped
RCA BTF1E	1972	2016	WZOZ	Scrapped
QEI 695T3.5	1996	2015	WBPM	Scrapped
QEI 695T5	1996	2015	WBPM	Scrapped
Harris HT3.5	1997	2015	WUPE-FM	Scrapped
Harris Z5CD	1997	2015	WXPK	Cannibalized
Energy Onix SSA1000	2000	2015	WDHI	Cannibalized
Harris MW1	1982	2016	WPUT	Abandoned
Mc Martin BF1K	1982	2016	WSUL	Scrapped
Mc Martin BF3.5K	1982	2016	WSUL	Scrapped
Continental 814R1	1980	2016	WDBY	Scrapped
Broadcast Electronics FM35A	1986	2017	WEBE	Cannibalized
CCA FM-1000D8	1973	2018	WDLA	Scrapped
Collins 828E	1978	2018	WSYB	Scrapped
Gates BC-1H	1971	2018	WHUC	Scrapped
Gates BC-1J	1954	2019	WBEC	Scrapped
Gates BC250GY	1969	2019	WSBS	Scrapped

*In some cases the “Year New” is a guess based on when the station went on the air. Before you write me and say “But model XYZ transmitter wasn’t made until 19XX, I did not look at every nameplate and write all the information down as I did this.

Like everything else, there is a process to this.

First of all, if the transmitter was made before 1978, the possibility of PCB capacitors and transformers exists. In the case of the GE BT25A, massive amounts of PCBs needed to be disposed of properly. According to current federal laws, ownership of PCBs and PCB-contaminated items cannot be transferred. Thus, the transformer casings were cleaned out and taken to Buffalo to be buried in a PCB-certified landfill. Otherwise, most other transmitters, such as the RCA BTA-10, may have a few PCB capacitors in them and perhaps the modulation transformer. Those items can be disposed of by calling an authorized environmental disposal company like Clean Harbors.

The rest of the transmitter is stripped of any useful parts. Things like vacuum variable capacitors, rectifier stacks, blower motors (if they are in good condition), HV power supply contactors, unique tuning parts, whole control and metering boards, tube sockets, etc.

The remaining carcass is then disassembled and hauled off. I got a guy that will do this for relatively little money. He takes the transmitter back to his warehouse and cuts it up, sorts all of the various metals out, then takes it to the scrap yard. This includes things like cutting all of the windings off of transformers and power supply chokes, sorting out the brass and copper tuning parts, etc.

Village seeks repayment from Energy Onix

This saddens me a little bit. Apparently, the Village of Valatie, NY is seeking repayment of a $500K loan from Transmitter Manufacturer Energy Onix. Since the passing of Bernie Wise, the company has basically folded.

The village may foreclose on the building if necessary, said Mayor Diane Argyle.

Located at 1306 River St., Energy-Onix was founded in 1987 by broadcast pioneer Bernard Wise, who is known for bringing the “grounded grid” to radio broadcasting. The company designed, manufactured and sold radio transmitters and tubes.

More from the Columbia-Greene Register Star.

Sadly, there goes support for many Energy Onix and CCA transmitters still in the field. I know of several of those old CCA transmitters that are still cranking away, 40 or more years after they rolled out of the factory in Gloucester, NJ. I have tried, several times, to call Energy Onix since Bernie passed last year and the phone goes unanswered. I wonder if we could pick up the field support and service for these units. I wonder if there are any spare parts left at the old factory building?

Transmitter repair

Sometimes it is obvious and relatively easy, other times not so much. This summer we have had wave after wave of afternoon thunderstorms. It is almost like living in Florida; almost, but not quite. Anyway, with the storms occasionally comes some lightning damage. At most of the transmitter sites we service, every step has been taken to ensure good grounding and adequate surge suppression. This is especially true of sites that have been under our care for a few years. Even so, occasionally, something gets through. After all, those five-hundred-foot steel towers do attract lightning.

Broadcast Electronics AM5E output tuning section

This is the output section of the BE AM5E transmitter at WROW. The transmitter got pretty trashed; a bad PA module and power supply and this capacitor in the output section. This particular transmitter is 14 years old and this is the first major repair work we’ve had to do it.

Broadcast Electronics AM5E output tuning capacitor

The capacitor was fairly easy to change out. As a general precaution, both capacitors were changed. There was a spare PA module and power supply on the shelf, thus the transmitter was returned to full power relatively quickly.

Broadcast Electronics AM5E output forward and reflected power meters

The rest of the antenna system and phasor were inspected for damage, a set of common point impedance measurements taken, which showed that no other damage was sustained.

Next, the 30 year old Harris SX2.5 A transmitter at WSBS. This failure was slightly more exotic; the transmitter started randomly turning itself off. The culprit, in that case, was this:

Harris SX2.5 remote control interface bypass capacitor

Literally, a two cent part. The transmitter remote control uses optoisolators. The inputs to these opto-isolators are RF bypassed to ground on the back of the “customer interface board.” After determining that the remote control was not malfunctioning, it was down to either a bad opto-isolator or something really silly like a bypass capacitor. This capacitor was on the ground side of the remote off terminal. It shows short on the capacitance meter and 4.1 K on the ohm meter, just enough to randomly turn the opto-isolator on and shut down the transmitter. Being a Harris transmitter, removing and replacing the “customer interface board” was no easy matter. Overall, it took about three hours to find and repair this problem.