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Misc Equipment

Harris

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Every so often ….

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 (the only real difference) could be harvested from the old board and installed. 

When they redesigned the board they did not fix the spelling.  *sigh*. This is why we can’t have nice things. 


Marti Electronics

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.   A dead one. 

These units are getting long in the tooth with the beige colored units like this one the oldest of the lot. 

Two common failures are the linear power supply (runs hot) and the nylon Berg connectors used to interconnect the modules. (don’t like heat). 

Fortunately a 13V 2.5A switching supply bolts right in.  $20 fix, the unit drops ten pounds and runs a lot cooler. 

   


Directional AM’s.   I love directional AM’s.  

What’s more fun than getting a call at power change, informing you that your AM directional Antenna is out of limits  and transmitter has shut down? 

Nothing. Nothing at all is more fun. 

Except for finding a smoke filled room and a loud buzzing noise. That is definitely more fun. 

The Burk ARC-16 Remote took a lightning hit and began pulsing the pattern change contactors every few seconds.

BOTH coils in some odd alternating pattern, causing the contactors to eventually  hang midway, leaving both microswitches open.  This continued until all the smoke had been released from the contactor coils.    All 8 of them. 

 

There. That’s better. 

 

Same storm caused the phase adjust coil in the phasor to arc and fail.  These are old coils, installed in the late 1960’s. Parts are available..but not on hand.  So  a couple coil clips, a bit of strap and a lot of  fussing got the phase back in limits and the Array back in operation. 


 Potomac Instruments

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..until it’s not. 

 

This one had an odd problem..no matter which tower you select, all 4 lights would illuminate. A quick look underneath uncovered mouse damage.   Mice love transmitter buildings and especially love to eat wiring.  As they did here. 

 

Repair and re-lace the harness, add a couple new capacitors across the FP Cans for good measure, found a replacement switch cap on Ebay…. and it’s back in operation. 

 


It’s always the capacitors. 

   

Often they look like this.  Bulged, either failed or about to.  This is the motherboard from a playback automation system which had developed odd behaviors.  While you can re-cap most motherboards, this one was better off replaced.  And so we did. 

 


Broadcast Electronics 

At one time these consoles were everywhere, along with the “spotmaster” branded units that preceded them. 

Two basic versions, the 100 series that used conductive plastic faders and cheap wafer switches..and this one.

The 200 series like this used real step attenuators and halfway decent ITT switches.   Both used the same electronics inside.  They did 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.