You had one job ….
This is the Auxiliary board used in a Harris HT 5 FM transmitter. It contains the screen and bias supply components and Plate current metering.
There are two versions of this board, the original designed to work with a Capacitor-input filter screen supply. This version is meant to work with the redesigned Choke-input filter.
Which is the sort of thing you find out at 2:30am. Fortunately two resistors are the only real difference and could be harvested from the old board and installed.
When they redesigned the board they did not fix the spelling.
At one time you couldn’t step foot in a radio station without finding something “Marti”.
In this instance it’s a STL-10 95oMhz Studio-Transmitter link transmitter.
These units are getting up there in age, with the beige colored units like this one the oldest of the series.
Two common failures are the linear power supply (runs hot) and the nylon Berg connectors used to interconnect the modules. (they really don’t like heat). This one had both issues.
Fortunately a 13V 2.5A switching supply bolts right in. $20 fix, the unit drops ten pounds, no longer needs the nylon berg connector and runs a lot cooler.
Directional AM’s. I love directional AM’s. Doesn’t everybody?
What’s more fun than getting a call at power change, informing you that the AM directional Antenna is out of limits and transmitter has also shut down?
Nothing. Nothing at all is more fun.
At this site the Burk ARC-16 Remote took a lightning hit and began pulsing the phasor and ATU contactors randomly every few seconds. This continued until all 8 coils melted down. That is a unique smell that immediately informs you what’s wrong.
There. That’s better. Kintronics still has parts.
Same storm caused the phase adjust coil in the phasor to fail. These are old coils, installed in the late 1960’s. Parts are available, but not on hand. A few coil clips, a bit of strap and a lot of fussing got the phase back in limits and the array back in operation until parts arrive.
Directional antennas need some form of monitoring and this unit was a best-seller for years. It was a huge improvement over the RCA and Andrew units that preceded it. Stable and reliable.
This one had a few odd problems. A quick look inside uncovered mouse damage. Mice love transmitter buildings and will eat wiring, as they did here. Several control wires needed to be replaced, others insulated.
The FP capacitors used are no longer available, but they make fine binding posts for replacements. Ebay turned up a new switch cap and it’s back in service. The mercury wetted relays used in these units are no longer available. The SCR’s are also becoming scarce.
At one time these consoles were almost everywhere, along with the “spotmaster” brand units that preceded them.
Two basic versions, the less expensive 100 series that used conductive plastic faders and cheaper wafer switches, and this one. The upgraded 200 series.
These used real step attenuators , wood side panels and halfway decent switches. Both versions used the same electronics inside. They do have some issues, particularly noise and crosstalk, but they are otherwise rugged and reliable.
I installed this console in the mid 80’s. It’s back for replacement capacitors and a few miscellaneous upgrades in 2015. Not a bad lifespan. It’ll run another 25 years.
Sometimes you don’t have to look too far to find the problem.
This is one way to deal with it….
Replacing the failed input amp is the other.
I generally like the Harris Gates series AM transmitters. When they no longer recycle after a power failure or remember their power settings…check the battery.
They last about a year. It’s the only part that needs regular replacement!
These are about the simplest, no-nonsense distribution amplifers on the market. Made exclusively for BSW I believe.
A simple +/- 15V supply with two-three tab regulators and 34- NE5534’s. Yes, 34 of them.
This one needed a -15V regulator. That’s it. Simple troubleshooting- the light was out! Sometimes a $1.50 fix is nice.