[NLRS] Help with 222 TE Amp Please - KM0T

[Mike - KM0T]

Need some advice on my TE Systems 222 MHz amp.  Model # 2252G - Supposed to be good for 200W or so.

 

Lets drive power thru to the wattmeter when the amp is turned "off"

 

When the amp is "on" No power output is evident with drive applied, as if its sucking up the drive power and not letting it thru.

 

PTT is working, the Remote LED and RF LED lights up, just like my other TE amps.

 

Took off the cover to see anything obvious, PTT relay clacks away like it should.

 

There or 4 MRF648s being driven by one MRF648.

 

Each transistor has the following:



Shack Power Supply:  13.59VDC

 

RX - VCollector - 13.59VDC

RX - VBase - 0 VDC except the driver transistor show 0.009 VDC.

RX - VEmitter - 0 VDC

RX - VBase to Emitter - 0VDC except the driver transistor - which is 0.009VDC

 

TX - VCollector - 13.57VDC

TX - VBase - .656 except the driver transistor - which is 0.690VDC

TX - VBase to Emitter - 0.656V except the driver transistor - which is 0.690VDC

TX- VCollector to Base - 12.92VDC except the driver transistor - which is 12.88VDC

 

All tests done with dummy load attached.

 

None of the transistors appear to get warm at all when PTT.  I wonder if the VBE is enough to turn them on?

 

Any Gurus out there that may know whats up or have any suggestions?  My guess is that nothing is broke, but perhaps the bias "turn-on" is low somehow?

 

Used it last year during the UHF contest, just dug it out again and have this problem.  Now Im short on time, its looking bad for next weekend.

 

Any help appreciated.

 

73 - Mike - KM0T - EN13vc

 

PS - interesting that there is 13.59 VDC on the collectors of the transistors when the amp is off, I guess they did not want to put in a 50A DC on/off switch.