Hi all,
Just had a success with this beast.
I normally do not work on exclusive 'ham bone' equipment.
The reason is, most guys think they can 'teach' the real radio engineers who make these things something new and get some kind of amazing specs out of the equipment.
In the real world this almost never happens.
I don't like having to 'un do' someones mod, then fix the real problem.
That is the reason for the poor attitude.
Anyhow...
It came in with weak 2M receive.
The client included a service manual and some small (smt) parts.
The parts sales slip was dated July 2004.
This thing had been off line for a very long time.
Anyhow...
The bag of little parts had a pair of FET's for the RF amplifier and some small switching style transistors.
Since the client issued me the parts, I started by changing out the FET.
Exactly no difference in receiver performance.
RX in FM mode was about 1uV for 12dB sinad before and after the change.
Used a coax adapter to jack into the RX board directly from the service monitor. The receiver measured good that way.
Something in the T/R system was bollixed up.
The 2M transmit board is buried deep in the radio.
Had to take that out, found a cooked 'PIN' diode. ( D2 if you have a drawing.)
Nice solid short A to K. That also bridged the RF path to ground. So much for the deafness.
Stole a heavy PIN diode, from a dead 40 watt VHF radio.
Soldered it in and now the radio works just fine.
This Icom now has useful sensitivity below .2uV.
The guy who takes care of my shipping has a UPS store in Reston Virginia.
Need to see Hal and get the service manual converted to a high quality PDF.
If word gets around that I fix multi mode radios, this won't be the last one I see.
Guys, look into this as a useful side work for your selves.
Keep it safe
Jack Crow
Just had a success with this beast.
I normally do not work on exclusive 'ham bone' equipment.
The reason is, most guys think they can 'teach' the real radio engineers who make these things something new and get some kind of amazing specs out of the equipment.
In the real world this almost never happens.
I don't like having to 'un do' someones mod, then fix the real problem.
That is the reason for the poor attitude.
Anyhow...
It came in with weak 2M receive.
The client included a service manual and some small (smt) parts.
The parts sales slip was dated July 2004.
This thing had been off line for a very long time.
Anyhow...
The bag of little parts had a pair of FET's for the RF amplifier and some small switching style transistors.
Since the client issued me the parts, I started by changing out the FET.
Exactly no difference in receiver performance.
RX in FM mode was about 1uV for 12dB sinad before and after the change.
Used a coax adapter to jack into the RX board directly from the service monitor. The receiver measured good that way.
Something in the T/R system was bollixed up.
The 2M transmit board is buried deep in the radio.
Had to take that out, found a cooked 'PIN' diode. ( D2 if you have a drawing.)
Nice solid short A to K. That also bridged the RF path to ground. So much for the deafness.
Stole a heavy PIN diode, from a dead 40 watt VHF radio.
Soldered it in and now the radio works just fine.
This Icom now has useful sensitivity below .2uV.
The guy who takes care of my shipping has a UPS store in Reston Virginia.
Need to see Hal and get the service manual converted to a high quality PDF.
If word gets around that I fix multi mode radios, this won't be the last one I see.
Guys, look into this as a useful side work for your selves.
Keep it safe
Jack Crow
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