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Years ago, I heard a story about a repair tech who died, but did not make it to heaven. While being shown around his eternal place of punishment, he was told that he would spend eternity in a state-of-the-art repair shop with every tool ever made, every part ever made, every piece of test gear available, and every service manual ever printed. He would also enjoy the assistance of beautiful women who would bring him units to fix and take away the repaired units. The tech was puzzled by this, and said, "I thought hell would be way worse than this!" It was then that he was told that every unit he would work on for the rest of eternity would be intermittent.

I am 74 year old EE and have been involved in electronics since I was very young. In spite of my vast experience with both tube and solid state electronics, I still learn something new every time I watch one of Mr. Carlson's videos. His knowledge is truly amazing and I'm really thankful that he shares it so well.

I don't care how easy he makes it look. Only vast knowledge, experience and intuition can make this look easy, and in an age of disposable electronics this is becoming a lost art. Mr. Carlson is the last practitioner of a lost art and future generations will refer to him as a wizard.

Hi Paul those micas look like the ones that are paper and foil inside

It's astounding how fast you narrowed down the intermittent crackle to those bad caps. Even though I learn a lot with each new video, I still wish I had .1% of your troubleshooting skill!

In my 47 years as a dad, husband, and family repair guy. we all know the problem mysteriously goes away as soon as we show up or touch the thing.

My first thought when hearing the pops was silver mica disease. Now to finish the video.

Looking forward to seeing the insides of the capacitors - more likely to be "mold" than mica! With the abundance of AR88s on this side of the Atlantic, it has become accepted practice to replace the Micamold C118, 119 and 122 on sight. Often C119 is discarded altogether (as has been done with yours, I think) to save the output transformer from being burnt out when that cap fails, though it can be placed across the primary instead - if a mildly muffled tone is desired.

Enjoyed your video. I am an electronic tech (not EE) and I gained most of my experience while in the USAF. My job was an analog flight simulator specialist. Tech school was 8 months long. Most large capacitors in the computer racks had a "bleeder resistor" across them. I made the mistake of assuming all capacitors had a bleeder resistor. While doing some work in one of the servo racks (power off), my hand brushed the back side of a capacitor...and WHAM. I got hit with about 400 VDC. It really rung my bell. I never made that mistake again.

Never ceases to amaze me with the extent of your knowledge. Like I said, you should be 100 years old.

Let's Find The Issue Together! In the 60's, we (RCA Service Co technician's) had VERY few testers in those days to use. Yes, we had a VTVM, Multi-Meter and an Oscilloscope. A Generator and a Sweep Generator. And that was about all. Thus, I had never seen a capacitor tester etc, at all. So the only thing we could do; is to use the Ohm's part of out Volt-meters for testing capacitors. And when I saw this Video; I remembered having a hell of a time with a problem on a TV. And I had never had a bad "flat" capacitor. But I tested it with my Multi-meter any way. And it seemed OK. So I kept trying other parts. With NO help. After several days, I said, "I'm going to change that flat capacitor"; with NO feeling it was going to fix it. But it did! And I was as happy as a little boy; in an ice-cream shop. So I saved that dadgum "flat" capacitor for yrs. And thinking about it many times. So, I sad all this Paul; because you caused me to have "tears nostalgia". And thank you so much; for this old man that's 91 yrs old that STILL loves Ice-cream! Whoopee.

It's always one of the biggest treats when you post a new video, thank you for all that you've brought to me during all kinds of different times.

I'm born in1967 and star fix electronic a 8 year old , now I have 55 and love see you when repair the old school electronic.

Yay day time new Mr Carlsons Lab!!!! Looks like I'll have to put up a Do not Disturb sign on my office door for the next hour ;)

This video was great! It was almost as if you perfectly anticipated every question or comment I had while I was watching it. For example, Me: Hmm, I can't remember ever seeing a mica cap go bad. You: These micas are leaking, which is uncommon for micas, but it does happen. Also, Me: I so rarely handle micas, that I would need a refresher as to how to read the values. You: I've talked about reading these domino style capacitors in the past. I'll just quickly go over that. Also, Me: Yes, but is the grid still glowing? You: Let's take a look at the 6K6 and see if we can see any glowing grids any more. The only one that left me hanging, Me: I wonder if he replaced the missing snubber cap on the transformer? Excellent video, Paul!

waving your hand past the antenna terminals brings back memories. dad had lost most of his hearing as a demolitions man in the army. he had taken a tv and electronics class via mail. since i had the best ears of us boys i would listen as he would tap on things. he also has a shielded trimmer screwdriver he would put electric tape over the end and explained capacitance and inductance to me as he would wander the circuitry to get an effect. we made a pretty good team but the days of tubes was waining and i had bigger apples to peel.

THANKS TO YOU I GUESSED WAS EATHER A RESISTER OR THAT MICA.

Troubleshooting periodic faults can be time consuming.. Mica caps can have "silver migration" due to moisture ingress, and the DC potential difference across them then cause this. In addition to the other differences between 6K6 and 6V6 you very correctly mentioned, the heater current is different. Would not be good in a series circuit

Excellent tube knowledge! I completely agree that there is a visible and significant structural difference between beam tetrodes and power pentodes, but I was unaware there had been illicit swaps and intentional mislabeling passing one off as the other! I know a thing or two about tube circuits, and use refurbished ones from the 1950s every day, but your knowledge of the tribal world out there and your snooping technique has impressed me immensly! Thanks for sharing that great acquired knowledge!

Every place has that superstar that can fix anything. Mr. Carlson is who that guy goes to when stumped.

Great Job Paul on the diagnostics. I am fascinated with the vacuum tube labeling issue. I want to share about a Russian 12AX7 that is maybe a 12AX6.5 at best. I have a Martel/Roland FAX-200C receiver from the mid 60's. It had a red plating issue NOT caused by the grid coupling caps. The filaments of 2 12AX7's in the preamp are used as the cathode resistor for the 6BM8 outputs. I had ordered 10 12AX7's from ~12AX7 ~ ECC83 SILVER GRID TUBE VOSKHOD NOS TESTED OTK USSR. It turns out that The normal pin-out for the filaments is pin 4 to 5 with pin 9 a centertap. Well this Russian tube omits the center tap and the filaments seem to be for 8.5V or so not 12 volts. Using this "almost 12AX7" still caused red plating in the outputs. Moral of the story.. Be very, very careful when you purchase tubes. These tubes worked ok for "Normal" circuit configurations. The devil is in the details.

Another pearl of wisdom from Paul, am I alone in thinking this guy is an electronics deity?

Thanks for the wonderful tips on finding bad caps in old radios your a good teacher 👍

I know almost nothing about electronics- or about electricity for that matter. I know enough to know I shouldnt be messing with it... But Mr. Carlson's videos are just so interesting and well put together. I honestly want to get into short wave radio now. I need a new hobby. Thx Mr. Carlson. Thanks for making such great content that is actually useful.

pretty cool! yea the mica chicklet caps are an issue. heat and time gets them. i was trained back in the 1960's and in the 1980's we replaced them with upgraded caps. and smart to just fire the parts cannon at the radio!

Awesome to see the previously restored Heathkit make a cameo appearance alongside the Superprobe. Seeing stars of episodes past reappear really underscores the continuity of their utility in the lab.

That 0D3 tube looks awesome with the purple glow!

Wow - you are one clever bloke to find that so quickly. When I was an apprentice (Mechanical engineering), when intermittent faults were reported, our foreman in the maintenance workshop had the mantra "let it develop", I guess his theory was to speed up diagnosis when the fault finally was no longer intermittent. Caught him out a couple of times with catastrophic failures and extended production machinery downtime as a result..

Heard that intermittent crackling and immediately thought of leaking audio coupling caps. This was kind of a long way of going about confirming that hypothesis, but I'm glad you did it and I think I will start looking for one of those HK units you used. And I'll have to build me one of those Super Probes and cap testers too.

It would be interesting to see the eye tube on your Heathkit IT-11 capacitor checker in leakage mode for these crackling capacitors at various leakage test voltages.

Thanks for taking us along Paul!

I'm loving following this project!

It was fun again. Your knowledge of tubes is amazing. Greetings from pe1krx.

Fantastic video ! Thank you !

Another very thorough fault tracing exercise. It’s good to see that you make the effort to prove the cause of the problem and not just ‘get rid of it’.

Wow! Fascinating! Great video. I had a similar bias problem on a Drake R4C receiver that was moving a 6BA6 control grid to positive 4V (!) ONLY after the unit was on for about 10 minutes. Normal voltage was around negative 2 or 3V. This problem only happened when the tube got good and warm. When I pulled the tube, proper negative bias instantly returned. I had a tube with a contaminated grid, where some cathode material had migrated onto the control grid wires. When the wires get hot enough, they give off electrons (DC Current flow from the grid) pulling the grid positive. One of my newer tube testers checks for this, calling it "grid leakage". This 6BA6 in question failed grid leakage after it heated up a while, when tested. This problem caused AGC drift on my R-4C, the S-meter would not stay "zeroed".

Mr. Carlson troubleshooting an intermittent problem? WHAT A BONUS!

Thanks for sharing another troubleshooting adventure!

Very well pointed out. Super thanks

Great video as always Paul!

Mr. Carlson is pure genius.

Your knowledge is amazing.

Really appreciate your time and effort. Having a blast w/this restoration.

The new shop is looking great and it's nice to see everything flowing smoothly as you make further videos. I really enjoy this series a lot and REALLY enjoy your teaching style! Thanks for sharing and best regards.

Another success of a video! Thanks, Paul! I can't wait for the next one.

Lots of good information here, Mr Carlson...thanks for sharing.

Your experience in electronics is nothing less than MIT proffesorism. I picture you as a child growing up at home, driving your parents crazy tearing apart radios and appliances giving them more power. "LOL". Excellent trouble shoot Paul. Thank you for taking the time to show troubleshooting tips!

Great episode.

Thank you for all the knowledge you share.

Absolutely fantastic video and a real eye opener. Many thanks!!

Mr. Carlson your a bad ass on vintage electronics, Fantastic job.

Excellent presentation

Mr. C. Thanks !

I really enjoy how you go about fault finding. I'm 78 Years and I learn from you all the time. Thank you Mr Carlson.

Great Stuff! Thanks for what you do....

Thanks for another great video.

I learned something today about how tubes can be "re-labeled", never knew that, started working on tube gear in 1976, thanks

Always so informative

Thanks, Paul. Another wonderful lesson!

Nothing but black plate 6K6's here at Mr. Carlson's Lab!

Sir, you are truly brilliant. Thank you for the detailed descriptions and explanations.

Enjoyed this and was always learned a lot. Thanks for your time.

BTW, Thanks so much for sharing your expertise, especially on the older tube equipment!

Just another very helpful video from Mr. Carlson. Yes, we want more of this kind of troubleshooting videos. Definitively.

I really do appreciate your videos on this project, Paul. They are so enlightening and interesting.

good job explaining... I'm new to all this and could actually follow.

And all these years I had thought mica caps would be quiet and stable. Wow. Thanks.

I think it’s This Old Tony doing time travel using his lathe again…

Impressive troubleshooting 👍👍👍

I learn at least one thing every time I watch one of your videos. I love how you go the extra mile and a half when doing these wonderful and very thorough restoration series. Museum quality. Awaiting the next video with much anticipation.

Love the video keep them coming great work

Very Good episode

Oh my gosh, this solved my problem! I have been tinkering with a GE-C600 for longer than I care to admit, and I had assumed this whole time that I wouldn't have a bad mica cap in my first attempt at a radio restoration. Well it turns out that C21 was functioning more like a resistor than a capacitor. Thank you so much!!

Neat to see the older test gear in use.

THANK YOU YOUNG MAN IM REALLY INJOYING .

Thanks for the information about vacuum tubes and the hints for troubleshooting. The more I read and hear about vacuum tubes, the more curious I am about them. Again, your experiences with the components and what you share is truly remarkable and appreciated. I also enjoy seeing the testing devices that you've created and your words about wanting to fix things the right way. The tools you've created help you do just that. Perfect.

Excellent tutorial, Paul! In 1965 I purchased a realistic reel to reel tape recorder. It developed an intermittent crackling noise, which was bearable on playback, but on record it would land up in the recording! I brought it to a local tv shop and an old technician tied it up for a week and found a bad cap and resistor. The charge? Around 10 dollars. I wish I could find one of these recorders for nostalgia reasons. One of the first recordings I made with it was "My Girl" by the Temptations.........

Thanks, for a very interesting video.

Fantastic Mr C. Interesting and informative. Surprised by how much I am learning :)

Thank you

Learnt a lot!

Fantastic troubleshooting and analysis Professor Carlson. I can't get over how clean the inside looks for the age of the receiver. Thank you for sharing.....

Excellent. Learned about 6K6's and my Heath signal tracer. Tnx!

Great class. I'm taking notes and looking at building the super probe.

Great analyse Mr Carlson sir you are awesome Thanks for the sharing this video sir.

Your depth of knowledge is amazing. A true master of the craft.

Thanks again Dr. Carlson!! Outstanding information sir.

As always very educational, thanks Mr Carlson !

The cap from the anode of the 6K6 to deck have known to short out and take out the very hard to find output transformer. it was the first thing I did was to change the cap, 3000pf.

Excellent video. There are so many ways to troubleshoot intermittent problems.

I've been doing electronics for almost 50 years and yet I learnt something here today.

Hey Paul. Fascinating detective work in this one! You really know this stuff. Many thanks again for all your work. Cheers

Thanks Paul, very interesting. Actually I had just finished watching all of KZfaq and was waiting for a new video to be uploaded. Good timing!

Thanks I am glad I picked up the same heathkit signal tracer you used....thanks for the lesson!

I remember that Heathkit T-3 signal tracer. The gain control was a weak design using a 12SH7 tube. Your modification was simple and replacing a noisy resistor made the gain control of the tracer far less noisy. Here you found leaky old domino mica type capacitors with it. I always learn something new (to me) from your videos . Another excellent video on the CR-88 receiver project Paul.

This was a good one. I used to be a repair tech for a medical equipment company. Thanks for your continued content!

A "Tip of the Hat" to Mr Carlson for isolating the failing capacitors. Very well done!

Your skills are amazing. Chapeau!

More excellent guidance and information. Thank you Mr C!