ICOM R7100 receiver

[Wendymott]

Hi peeps. I had a R7100 given to me yesterday......Duff, No output on any band except the Highest, where there is nothing to hear anyway
While I was surveying it.. "Tinkering" I noticed a 10.7 Mhz I.F output on the back panel. Using my scope I could monitor input signals.. so the fault was past that stage. Using my FRG7 as a tunable I.F I connected, as you do, to the R7100, and smoke started to eminate from the R7100. Power off smartish
Looking at the circuit... ICOM in their wisdom have 9V DC fed via a rf choke to the output jack. Obviously a DC block cap was fitted and the FRG7 was indeed very useful, showing the receiver worked to that point. After a nights rest, I delved deeper and found the 3rd Mixer L/O oscillator had no output. The 10.245 Mhz xtal was duff. With a 11.155 fitted the receiver is back working .. I have put a request in the Wanted column for a xtal.
Why that DC output is configured like that ?? Anyone any idea ??

[majoconz]

Wendymott wrote:

Why that DC output is configured like that ?? Anyone any idea ??

Yes - On my R7000 the IF out was there to feed a TV converter which used the receiver to power it via the voltage fed down the 10.7MHz wiring. I snipped the inductor (L59 1mH at the J5 socket on the RF board) to remove the volts but made it reversible.

Great receiver, you'll love it BUT the power supply runs very hot on the 7000 - your 7100 may be different. I run mine on an external 12volt linear power supply.

[Wendymott]

Hi Martin. Thanks for the info... so really it is dual purpose In / Out...I have cut the track and inserted a 10 nF in series...Job done
Its not intended as a receiver as such... just an.. as and when radio.. much as the FRG7... been in the cupboard till last night.

[majoconz]

Hi Wendy - you didn't really need to add another cap if you snip the inductor - there's lots of small caps in the way.....
Cheers - Martin