Wednesday, May 30, 2018

Repairing the IC-211 Receiver, again...

This isn't my first rodeo with this 40+ year old rig from the mid-70's. It uses a dual gate N-Channel FET for the 1st RF amp... It's very sensitive (single tone detectable down below .01uV!), but it is also easily blown. I think this was knocked out when lightning struck a tree about 100' away. I repaired it last back in 2015, when I fried it while operating full tap on the 160 m band, when the 160m antenna was only about 10' away from the 2m SSB yagi :-)

I snatched the case off of it to have a was only hearing about 3uV minimum, but when I injected a signal on the output of Q47, it came alive. Yep, bad FET.

This is Q47 after I removed it. I dug around in the junk box a bit, but didn't have any more of those. This was a ELM222, but the original was a 3SK40. 


Well, I scratched around in my spare parts and found a RCA 148085, similar to a NTE222, and decided to give it a try. Sure enough, the receiver sprang to life and has a really sensitive front end, now.

Q47 as seen on the schematic...

This is the bag of the one FET I found in the workshop with a suitable operating frequency range.

Here's the IC-211, back in it's operating position and ready to go. I was able to work Alex KC4PHJ over in Apex and was hearing him fine, so combined with the rebuilt 2M SSB antenna I put up last weekend, my 2M SSB station is back on the air!