Icom IC-211 PLL and Other Repairs...

 I've owned this Icom 211 for many years. I bought it from a friend back around 2008, and it's had a few issues over the last 13 years. To be fair, this is a mid-70's vintage rig, so some repairs are to be expected to a 45 year old radio :-)  

I leave this rig on 24/7, just so it's nice and stable when I get on 2m SSB. I came in the shack and realized it wouldn't transmit, and upon further inspection, I discovered it wouldn't receive, either. Oh well, off the table, and into the workshop it went. 

Once I got it on the bench, I realized the PLL wasn't locking up, so I began checking various voltages. I discovered the -9vdc supply was only about -7 volts, and by the time the -9vdc source made it to the PLL, it was only about -5.5vdc. I sub'd in a -9vdc source, and the rig fired up and ran. After a bit of poking around, I discovered a small choke that supplied 5vdc to the dc-to-dc converter that generates the -9vdc had failed and was only supplying about 3 volts to the converter. Once that was repaired, 5 vdc was supplied to the converter and it worked correctly. The 9vdc source was once again, as it should be. 

 The radio had been drifting more and more over the last year, and a quick thermal test with coolant and a heat gun revealed a small styrene capacitor in the PLL was failing, and once replace, it was solid and stable. Also, there was problems with the dial lights, and some noisy controls. 

On the bench, getting a good check-up.

I sampled the VCO to the freq counter via a .001 cap. Loading to the VCO wasn't too bad. 

This is where the 820pF styrene cap was located that caused all the drift...

This is the -9vdc dc-to-dc converter that caused the problem...

This is where I sampled the -9vdc that returned to the PLL...

While the radio was on the bench, I wanted to replace the meter lamps. I had some "warm white" LEDs to experiment with, from a string of LED Christmas lights. I discovered that 1000 ohms, 1/2 watt was about the right resistor value to bring the lamp to normal brilliance @ 20 mA or current, when powered from the 12vdc source. 

There's the Christmas lights I used. I'd break the clear part off, and the LED would slide right out. Easy to do, and you can buy a sting of these for $3-4 bucks. They're bright. You can see them in the meters of the radio, below. While the radio was on the workbench, it got a full alignment and is performing very well. 

 

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 look...it 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!

Dave WB4IUY
http://www.WB4IUY.net

Repairing the Icom IC-211

This was another late sleepless night project... Back during this past winter, I accidentally blew the receiver sensitivity out of my old Icom IC-211 2 meter SSB rig while operating on 160 meters at full power. I never turn the IC-211 "off"...maybe a mistake. The 160m antenna is up on the tower at about 100', the 2m SSB antenna is about 15' above that. I've left the 211 on 144.200 for years, no matter what other band or power I was running...but that roll of the dice finally caught up with me. 

I broke the rig open and started poking around. It had slowly developed a short list of problems, but nothing that stopped it in it's tracks like this blown front end. Using my signal generator, I capacitively coupled a signal on 144.200 mhz into the 1st RF amp stage. I found I had plenty of system gain when the signal was injected at the drain, but almost no gain when injected at the gate. A quick voltage check proved there was almost no current flowing in the device when signal was applied. It seems that the  old 3SK40 dual gate N-channel FET in the 1st RF amp stage that was toasted.

Junk box time!! I dug around in my workshop a bit, to try and locate something suitable from 35+ years ago.. That's an old part from the 70's, but I had 1 piece of ELM222 (similar device) in my parts bin (much to my surprise!).  I removed the old dual gate n-channel FET and soldered it in. I set up the signal generator, opened the service manual PDF, and gave it a full alignment. Wow!! Sensitivity was a little better than before, and I was very surprised as how hot the receiver in this 40 year-old radio is. I have a bunch of service manuals and such online for my own use, to minimize paper, and in case someone else needs them. You can find them at http://207.126.49.184/wb4iuy/radio/wb4iuy6e.htm .

While it was open I replaced the dial lamps, cleaned the optical chopper in the VFO (the VFO operation was a little erratic), and sprayed out the controls.

She's back in the shack and VHF contacts like nothing ever happened. It's definitely receiving better than before, and working pretty darn good for a 40 year old radio!

Dave WB4IUY
http://www.WB4IUY.net