Show Posts
1
Test Equipment / I'm new, what better way to start with a faulty Marconi 2018 RF generator
« on: July 24, 2017, 11:23:40 PM »
Hi Guys,
So I bought a nice Marconi 2018 0.8-520mhz RF generator recently as I am extending my Audio electronics background into RF (witchcraft as my friends call it). Got it for a good price too, had been used in the Aircraft industry here in New Zealand, no doubt to align Aircraft radios...
So I was running it to align an FM tuner which was going very well.
Near the end of tuning the IF stage, I noticed the signal cutting out, it happened to time perfectly with something I was touching, I thought for a moment there was an issue with the tuner, but no, it was the RF generator signal cutting out, it became more frequent and then it finally "gave up the ghost"...
Panel is still lit, all parameters are adjustable via the digital control panel.
All voltages are present and correct from the PSU....
I have the entire service manual and schematics, I have followed their testing procedure for the unit, and I have established the RF amplifier is good, the control interface is working according to the tests I performed out of the manual.
No signal getting to the RF amplifier, in fact all the boards, modulator, VXCO, Phase detector, frequency standard XO is functioning, fault could possible be on the Frequency divider and FM drive chain, OR the RF Oscillators.
Now the road block I have run into is I can only measure up to 20mhz at the moment with the gear I have, so I cant verify the the RF oscillators (of which there are 4 all running in the hundreds of mhz.....
I have ordered a 1ghz frequency counter which should be here in a few days, so hopefully I will have some joy once this arrives.
I will take any advice going to help further narrow this issue down whilst I wait for my frequency counter to arrive.
Cheers Guys
Oh PS, the only thing I haven't done is followed the testing via the front panel using the binary control commands, I'm not sure I am game enough to give that a go!!
So I bought a nice Marconi 2018 0.8-520mhz RF generator recently as I am extending my Audio electronics background into RF (witchcraft as my friends call it). Got it for a good price too, had been used in the Aircraft industry here in New Zealand, no doubt to align Aircraft radios...
So I was running it to align an FM tuner which was going very well.
Near the end of tuning the IF stage, I noticed the signal cutting out, it happened to time perfectly with something I was touching, I thought for a moment there was an issue with the tuner, but no, it was the RF generator signal cutting out, it became more frequent and then it finally "gave up the ghost"...
Panel is still lit, all parameters are adjustable via the digital control panel.
All voltages are present and correct from the PSU....
I have the entire service manual and schematics, I have followed their testing procedure for the unit, and I have established the RF amplifier is good, the control interface is working according to the tests I performed out of the manual.
No signal getting to the RF amplifier, in fact all the boards, modulator, VXCO, Phase detector, frequency standard XO is functioning, fault could possible be on the Frequency divider and FM drive chain, OR the RF Oscillators.
Now the road block I have run into is I can only measure up to 20mhz at the moment with the gear I have, so I cant verify the the RF oscillators (of which there are 4 all running in the hundreds of mhz.....
I have ordered a 1ghz frequency counter which should be here in a few days, so hopefully I will have some joy once this arrives.
I will take any advice going to help further narrow this issue down whilst I wait for my frequency counter to arrive.
Cheers Guys
Oh PS, the only thing I haven't done is followed the testing via the front panel using the binary control commands, I'm not sure I am game enough to give that a go!!