Hello Guys,
I have a George with a faulty TX.I have plenty of RF (4v RF on 10Mhz scope) output from the driver but negligible input to the finals.I have changed the finals but with no difference.I believe the protection circuit has kicked in.
My question - How can I defeat this protection circuit so I can carry on fault finding?
Most grateful for any advise or information.Thanks and regards to all.
Bob
President George
Re: President George TX
Do you have any bias volts on the base of the outputs? if not check R206 and 207. let us know how you get on.
Rick.
Rick.
Hi Rick.
Sorry to reply so late - but been away for a few days.
So - here goes.
As I said 4V RFout of the driver.
Q501 base volt = .14v with approx 2v RF
Q503 base volt = .76v with approx 1v RF
Only about 150mV going into the aerial.
Hope this gives a clue.
I couldn`t find the R206 so the base voltage is taken off the base leg.
Regards
Bob
Sorry to reply so late - but been away for a few days.
So - here goes.
As I said 4V RFout of the driver.
Q501 base volt = .14v with approx 2v RF
Q503 base volt = .76v with approx 1v RF
Only about 150mV going into the aerial.
Hope this gives a clue.
I couldn`t find the R206 so the base voltage is taken off the base leg.
Regards
Bob
Re: President George no TX power
Hi Bob,
You will possible find that R572 is open, it some of the later George?s L208 or L209 and L207 or L211 maybe 1 ohms resistor. It sounds like you have no bias to the finals. Hope this helps. Let us know how you get on.
Rick.
You will possible find that R572 is open, it some of the later George?s L208 or L209 and L207 or L211 maybe 1 ohms resistor. It sounds like you have no bias to the finals. Hope this helps. Let us know how you get on.
Rick.