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GM300 TX thermal failure
Posted: Fri Mar 25, 2011 8:32 am
by PY5FT
Hi!
Anyone know if have component correction/change in TX VCO to prevent fail with "hi" temperature? (Maintenance bulletin)
I have a lot of M130 (VHF, same GM300 board) with fail when temperature rises, all are used in mobile conditions, panel mounted (TAXI fleet).
The voltages in VCO all OK in room temperature, 20-30ºC.
Best regards, Antonio.
Re: GM300 TX thermal failure
Posted: Fri Mar 25, 2011 3:16 pm
by Will
If the GM300, and many other Maxtrac/Radius mobiles are not aligned correctly the master reference oscillator will not stay on frequency over temperature extremes.
Re: GM300 TX thermal failure
Posted: Sat Mar 26, 2011 8:29 am
by jackhackett
These radios had a problem with the feedthru connector that could cause VCO problems.
See the following topic:
http://batboard.batlabs.com/viewtopic.p ... ru#p392502
Re: GM300 TX thermal failure
Posted: Wed Mar 30, 2011 2:50 pm
by PY5FT
Hi!
Thanks for replays.
Reference oscillator runs normal and no problem with 14 pins contact bar, I know this problem. My case is only in 10 radios same problem (total fleet is 250).
With a HOT air gun near to TX VCO componets this problem occur (VCO tension go to 8Vcc indicating no HI freq osc.) , not sure if is coil, FET osc or varicaps or any other caps around.
My hope is a bulletin to correct this fail.
Some time I got a SM50 VHF with a TRIPLE (The strip line and associate parts tuned in 3x) frequency input in prescaler.... VCO osclillating but PLL output voltage low, evident.
Best regards, Antonio.