How to repair Collins kwm-2 tube Ham Transceiver Neutralization issue

Recent arrival at D-Lab electronics. My friend N7MSR has offered to donate classic Collins gear in need of repair, to enhance D-Lab's capabilities, plus open me to new repair opportunities. I have worked on a few Collins pieces in the past, but never a KMW or S-line. So this is great. Mark is a very cool/+ funny guy. We are 2 peas in the pod. Please stick with me as I grow to understand the high quality Collins/Rockwell equipment.

[@tomdonahoe3539]

I very much appreciate you sharing your know-how & skill with us! 😊 Great information.

[@TheRadioShop]

One of my favorite rigs to work on. Had a lot of these in the shop from basket cases to pristine. Good job on the neut cap replacement Terry. Super cool my friend.

[@daveogarf]

Oh, from your lips! The Internet is a total GODSEND to those of us seeking or sharing information! You may have been poking around, searching for the problem for months without that incredible step-by-step 'hint' that took you right to the solution! (Not demeaning your technical prowess, BTW).

[@ElPasoTubeAmps]

Nice video and repair. I recently acquired a KWM-2A by Rockwell Collins (built in 1978) that looks and performs like it was never used. I did carefully go thru the cleaning process of tube sockets and switches and couldn't be happier with its performance. I have had Collins S-Line equipment since 1983 with minimal issues. I remember one issue several years ago with the 32S-1 which turned out to be a shorted capacitor on the screen of one of the 6U8's - I don't remember which one, and recently when the 2.1 KHz mechanical filter in the 32S-1 failed, but fortunately, I found a new one on Ebay and fixed it. Very nice to see that there are a few gentlemen like you that appreciate this equipment and have taken the time to post videos on it. Keep up the good work. You just may save a few of these magnificent old radios because of your efforts and videos. 73 WA4QGA

[@MichaelLloyd]

I have a couple of S-line transmitter / receiver pairs. One set works and one has been stored in less than clean conditions so I haven't powered it up. Great to see you repairing one!

[@Bleats_Sinodai]

Terry, I recommend you add sites like that to the Wayback Machine backlog. You can "snap" websites and they are added to their database, as a security backup in case the original website goes down, gets partially erased, or is deactivated. It's like getting a Xerox copy of a library book.

[@rciancia]

Terry, very cool. I never saw a cap like that before. When you turned the gain up it reminded me of the first note to the Beatles song Day Tripper - or in this case possible circuit breaker tripper. :) Well done Terry

[@umajunkcollector]

I concur on the web and YT being so very helpful.

[@cheycasters]

Thats a crazy looking circuitry!!!

[@robertcalkjr.8325]

Thanks Terry.

[@DeadKoby]

I'm trying to assist the information community too! As are you! We're in this together trying to make the world a little smarter.

[@superhet7281]

Excellent, as always! After this Collins series I’d like to see you work on some of the Heathkit SB/HW SSB gear.

[@d-labelectronics]

I have a SB-401 in the Q

[@captlarry-3525]

THIS IS WHY YOU NEED TO KEEP YOUR TRANSMITTER CLEAN ! DIRT COLLECTS MOISTURE AND MAKES AND ARC PATH.

[@RobertKohut]

Nice!!

[@domfilap8477]

Great video. Unfortunately you have used the wrong trimmer cap. The one you have used is only rated at 600v, and will tend to arc on 28mhz - I know because I had the exact same one in my junk box. The correct one needs to be rated at 1200v.

[@dhpbear2]

Just from that beginning video of the circuitry, this looks like *Tektronix* quality!

[@d-labelectronics]

Yes Sir, military quality

[@domfilap8477]

Hi Terry, Brilliant video - very informative! Just wondering, does the .001 have to be rated at 2Kv or would 1Kv be enough? Cheers.

[@robertjonasson2527]

My Heathkit SB-401 uses an air variable neut cap..never had a problem.I don't know why Collins used those tiny variables in a high voltage RF circuit.

[@jandejong6498]

Sir, if you drink wine, you never connect two or more high voltage wires in the wrong position?? [lol] from the Netherlands, Merry Christmas and a Happy New Year!

[@umajunkcollector]

So ehat ya think of a Collins after all, was it that good a rig?

[@msaradio7455]

I cant believe so many comments about the damn wine, lol!

[@d-labelectronics]

Yep, veered off the main subject matter

[@kd5ozy]

the first thing i do on these is redo the tube shield grounds. they cause a number of different problems

[@d-labelectronics]

Thanks, I will take a look. Are you referring to the mechanical connections (screws/nuts) mounting the socket to chassis ?

[@kd5ozy]

@@d-labelectronics Yes sir. I have had a few with af oscillations that just had poor grounding on the tube shields. It may not be, but that's the first place I look

[@evascroll]

its there a way to neutralize with out oscilloscope?

[@domfilap8477]

Yes - just adjust till the plate dip and max power out coincide

[@ashave9100]

IT IS NOT CLEVER TO WORK ON HIGH VOLTAGE ELECTRONIC EQUIPMENT WHEN DRINKING- YOU MIGHT SPILL IT !

[@SuperBuzzbomb]

Thats why he has it when he's done!

[@amyluke4598]

Leave off the wine. It doesn't add anything to your videos Harvey, KM4JA

[@SuperBuzzbomb]

I actually enjoy seeing him with the wine. It tells me he enjoys what he's doing.

[@d-labelectronics]

Thanks man, I appreciate your backing/support

[@robertcalkjr.8325]

Wine is ok, but I prefer a cold German beer.