This is a 50MHz GE Mastr II station waiting for a 6 meter conversion. This will include retuning the unit into the ham band, 5X MHz and duplexing the station for repeater use. The 4EX3A-11 standard test set and a Simpson 260 are here. LBI's are being accumulated and read. Miscellaneous parts are being gathered.
The unit is / was a DC74KAN33A
D = 30 inch Desk Mate
C = Continuous :)
7 = 66-128 Watts
4 = 20 KHz
K = Local DC Remote
A = 1/1 TX-RX Frequency number
N = Noise Blanker
33 = 42-50 MHz
A = +0.0005% (5PPM)
The left audio card in the shelf was an extra, removed it.
Why aren't there test set selectors in the holes? They were used on IDA units.
Radio Front Panel Door: 19D417262G1
LBI-30775F, various numbers
Two center pictures - Intercom: 19C320671G2
LBI-30700G, Pg. 3 of the manual, 4 of the PDF, how do I read the dashed lines for the Intercom - 10V Reg - Channel Guard?
System Interconnect Board: 19C417213G1
Receiver: 19D416478G4 Rev B and Audio / Squelch / Tx
LBI-4989C(no noise blanker), LBI-4991G (w/noise blanker) -
This is the Noise Blanker version, the Mixer/IF in the 4991 matches, the 4989 is shorter.
Exciter: 19D416659G4 Rev G
Control Shelf Mother Board: 19D417214G1 Rev C, extra wire soldered on - what for?
The pass through in the left picture is for a DC positive connection.
Far right picture shows some burning around a resistor that is turning white.
Power Amplifier: 19D417955G8
With a component board of 19D417927G4 Rev B
New pictures of the PA, failing resistors, burnt board, leaking resistors and one turning white. This board produced about 75 watts wide open. I didn't run it very long for fear of wrecking something.
The vertical resistor that turned white, there are four like it, R274 - R275 - R276 - R277 value: 100 ohms 1 watt 10% . The horizontal resistors that are excreting something from the sides, there are three, R244 - R245 - R246 value: 100 ohms 2 watt 5%
So the question is: is this normal when a part fails, is it ok to replace the parts and use the unit or is it better to move to a totally different unit? The suggestion was to replace the component board so it was changed out for an identically numbered unit out of a mobile. The mobile PA board has TO22 case transistor, Q217, that was changed to the station/repeater TO3 unit. The antenna relay was bypassed with a short piece of coax and the traces were cut per repeater-builders site instructions. Worked great.
The center picture shows the disconnected relay. Did you know that the default has the TX and RX ports connected, didn't even think about it before. More importantly, the resistors and components on this replacement board are in really nice shape. The last picture shows the Q217 transistor in the bottom left corner. This board produces over 130 watts, no idea how much as the service monitor swung past 130 and I turned it right back down again, no sense damaging either unit. The spectrum analyzer shows a very clean signal from 50 to 100 watts, very nice.
Power Regulator Card, bad voltage, used another one instead. Cleanliness or looks doesn't mean a thing. This one doesn't work right and is very clean. The other unit is a little rougher looking but is right on the money and works great.
Remote, Remote Audio Cards
Any thoughts about the station, especially conversion ideas/practices,
please email aa9nv at arrl dot net, thank you very much.
Tentatively going to use one of my 6 meter duplexers that will need some conversion work.