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Signal Tracer Troubleshooting Repair and Modification





More electronic troubleshooting adventures! Join Paul in the Lab as he explains “in great detail” the circuitry inside a Heathkit T-3 signal tracer. Then Paul will discover and fix some design flaws. See how the Watt meter (eye tube) and noise tracer functions work.

28 thoughts on “Signal Tracer Troubleshooting Repair and Modification”

  1. Mr. Paul, what can I say except you produce the BEST videos I have ever encountered. Camera work A+, knowledge A+, explanations A+. You make other people's productions look like a pre-school finger painting.
    I have been doing what you do as a hobby for 20+ years and the first video I watched made me feel like I knew nothing. Please never stop, it has become Saturday ritual to watch 2-3 videos. I have learned SO MUCH,, keep up the awesome work.
    FYI I have been a chip head since age 10. Thank you so much cause I can imagine the gobs of time it takes to make just 1 production.

    Way to go, thanks again,
    Doug USA Philadelphia

  2. Kennynva says:

    One other thing I just found out…when using the watt-meter setting..you cannot plug in a plug with a wide blade.

  3. Kennynva says:

    Does the 'eye' move or indicate when you have it switched to "tracer", and have the high gain setting to off?

  4. Kennynva says:

    Hi…I have a question about the 12A6 tube…mine gets extremely hot…I have worked on tube equipment before, and this tube seems way to hot…all the voltages are right, any ideas?

  5. Reid Dixon says:

    I'm listening while driving . How would i go about choosing capresister values for grid leak bias if I'm not familiar with tube impedances? I own an amature handbook . Guess I'm asking for rule of thumb magic .

  6. Kennynva says:

    I really like that very FAST Agilent multi-meter..if you have one laying around you dont use..I would like it…thanks for the nice video…I have one of these signal tracer's on the way..and will go thru it, just like you did……..

  7. Kennynva says:

    The high voltage at the audio input plug wont hurt your signal generator when hooked to it..at 1:00:33?

  8. Kennynva says:

    Do you suggest to cover that grid cap on the high gain tube(12C8), to keep it from inducing hum? If so, what would you use to cover it with?

  9. John Nikoden says:

    Mr. Carlson I love your videos I have the same signal Tracer but the power or should I say the output Transformer is no good do you have a suggestion for a replacement output Transformer?

  10. Kennynva says:

    This might be a strange question..but can you install a 'magic eye' into a Heathkit T-2, the signal tracer prior to the heathkit in the video..????

  11. Jean AArouet says:

    Perhaps you could design a current sensitive relay which would only allow B+ to any external terminal post ONLY if more-than-typical body-resistance current is being drawn…for example by an external speaker being connected. By the way I found the amplification drop high gain "off " is very significant as said elsewhere. My EICO sig tracer has oscillation when gain is high…I'll check the wiring proximity and try a grid stop.

  12. Jean AArouet says:

    By the way these are crocodile clops…the boxier, wider clips with the shorter jaws are alligator clips. Just thought I'd provide some tradition…pretty much lost today /

  13. Jean AArouet says:

    Paul and others…have a look at the output transformer connections. There is no B+ to the anode of the 12A6 unless you bridge B+ and a "P" the better one is the LHS 'P' which is shown going to the bottom of the primary. If yours is working then somewhere they have bridged the connections. I actually like the idea as it is safer for any user or 'fidget' if done with insulated banana plug wiring…even with my changes to the colour scheme. Comment?

    I'm presently tracking the circuit as I have good amp and signal on high gain, of course…..whith the bridge in place, much greater amplification but nothing from the audio (high gain off)…The 12A6 could be low in gain of course but ok when driven harder by the 12C8. Direct tough to the caps (I have 2 x.01 in series) at 12A6 grid is very low level amplification. I have found errors in some of this 'working' gear from US…including a p/s electro back to front, unsoldered joints, broken wires, totally dud components…As I go I make things more accessible and easier to do again.

  14. Jean AArouet says:

    I made a comment about the EICO 145, so also had a K9 a couple of years ago The date order of these emails varies….a few minutes ago I was down amongst the 2 year old ones…now having logged-in I am back up to where I was last night but still below Murphy of 2 years ago….This might see Paul not reading emails which are right out of kilter. That said…I have found at least 3 versions of the EICO 145 schematic. The 145A I think have found 2. Mine has the 6SQ7 6SJ7 line-up in the 5 tubes. I've recapped etc my Heathkit and my EICO capacitor Tester each awaiting one component. I've also written about safety improvement on the Heathkit.

    The original 145 had 2 tubes….this is confusing so be aware. Mine also used .01 caps as original but the circuit showed.25's….can't be right. Don't be told by components stores that polarised electrolytics can be replaced by non polarised…I was!!

    In rewiring here and there and changing caps you can free up space…my suggestion is you use tag strips as intermediate support for the smaller components and also for the mains leads after safely (with NO knot) securing the mains…better to change to doubly insulated as well. Paul showed one of the replacement cotton covered leads. Use grommets or preferably securing glands made for mains cables.. They have a "U" shaped section which binds the cable. Then run colour coded cable safely to the mains points.

    I think I installed 4 tag strips altogether..it's a better job than having components floating. Always, in my view, do these refurbs as though you'll have to do it again…Place components so their data can be read easily and don't bind the leads around tags as they did…if factory someone placed all the components and then someone else soldered them. Homebrew…who knows. Now I have worked out why Paul's polarity tests were not working, I may have to redo a lot of the work.Voila

  15. Jean AArouet says:

    To Paul Carlson
    As you know Paul, one or two others are reproducing your videos in their own presentations….why??…why not refer people to your site instead of the lazy way….That said I made a couple of errors emailing to one of them, thinking it was your presentation…instead it was aW2 . I thought great he's sent me to QRZ for his email…which was not on your site (or his). Pity…or am I just plagued by poltergeists…..

    I've redone almost all of my Heathkit T3 including your mod. I've managed to find (at 1mV) why I get nowhere testing for polarity…..With no B+ aboTut I had no shoes on and a cement floor. That clicked and I put my feet on a box….got some results BUT only to below 1.UFd…..Unless the scope (BWD 821) is down on sensitivity that's its limit. I had no success originally with my Tektronix but will give that another try tomorrow …with feet not making me a giant bypass cap.

    There's another exercise…Mine has Ch 1 voltage vertical broken…I believe the ears break-off…so I only have channel 2. I bought it with the fault but in 3 years have not found a replacement part. Perhaps you could use your ingenuity……? I'm not the The best way of getting to the Vertical shafts is another issue….and it would be simple excepting that one screen screw is inaccessible. Instead one has to pull both boards I guess….but is there a fix ……'yes grasshopper'….?'

    The EILCO cap tester you introduced would be an interesting exercise….a couple of massive caps….very basic ….Mine (from USA "working" had a filter cap in back to front….may have made little difference if stuffed. Getting rid of the huge caps gives space for a less crowded replacement of the can 4 x20's. I can buy a can 3 x20 1x4uFd here but 40 is a big jump from 20, I could I suppose put a 20 uFd in series with that leg..It's a patience job getting to paxolin switch connections …so the big caps are an early shift..The rather flimsy…a broken one (as was on the poor quality log-pot on my EILCO sig tracer) sends one looking for spares….or trying to make a replacement.

    I've ordered the 1meg Log. Having replaced the caps without checking polarity I have to recheck it all. The 4 uFd 'dry electrolytic' (reading 7uFd…which is better than 164 on one of the 10uFd's) reminds me…I was sold some ( or I bought) unpolarised electrolytics at Jaycar…..very doubtful they replaced polarised bypass caps electro….I had them ring their specialist…yes they are ok….well I doubted it and tpretty much out of our hair.ook only one. Those caps are not a replacement but are ok for interconnection…perhaps you could do a more deep discussion on caps than anything you have done so far.

    Again I have to now check all caps for polarity…after doing my Heathkit and EILCO sig gens and my EILCO cap tester.. Each one has one thing to go anyway bit…many hours already spent. Getting rid of the tank-sized caps above chassis on the Cap tester enables better wiring techniques and a couple of single tag tag strips helps a lot. I can't buy those ceramic stand-off's here. Again the use of single core cable is a curse…as electron-motion fatigued wires break easily or are not the actual CSA they seem to be when internally fractured. I found one terminal had a defective nut….matched the others but factory-defective. Two banana posts were loose at the terminals.

    I suggest that in the revamping your followers fet the mains right away from the location they are….get rid of the knot…..use a proper gland or a good grommet and terminate the mains at a tag strip, suitably spaced wire from wire….and mains only on it. Secure the mains cable to the chassis using only insulating fixings. Get rid of the mains bypass cap….use external line filtering not that rubbish idea…which can end up putting mains voltage on an unearthed chassis. …use doubly insulated mains flex and use correct polarity. Then run wires safely neatly and coloured red active/ black neutral to the switching.

    Now properly secured the mains horror is pretty much out of our hair. I've spoken elsewhere about colour coding banana terminal-posts…

    After these three comes my Leader Transistor Tester…but I'd really like to fix that Tektronix CRO…If any reader has some spares…………hint hint!

    I'm presently very unhappy with AEA….finally after nearly 2 years forced a reply. My antenna analyser was used once only …well stored for about 20 years. Now the screen is kaput and they are no help at all….in fact they don't seem to be bothered getting a technician to me. I paid nearly $1000 for mine way back….now they are over $3k and it is a dead-ringer for the new ones. They say the screen is different…well maybe but that doesn't mean it cannot be adapted as it will be same physical size and perform the same functions if properly engineered into my circuit.

    Is it useless Paul?….or can a new screen of some type be fitted?

    My Regards and do tell me how to email you….via QRZ is ok.

  16. Jean AArouet says:

    By the way I am commonly finding a knot used in US mains cables to reduce the risk of the mains cable/wire being pulled out through the (usually un-grommeted!) mains access hole. Get rid of the know…it encourages shorts and is poor electrical technology. Find a better way…and if such a thing as doubly-insulated mains wire exists in USA, replace the singly insulated cable by it…do NOT knot…..do things professionally and with mindful safety awareness. Use grommets at all 'pass-through chassis holes.

  17. Range Man says:

    I have a question about "signal generators"…. years ago you needed to buy an expensive signal generator, a "Z" meter, and other giant clunky gadgets to do repairs…my question  is, can you just pull signals and waves off the audio of your computer on a frequency wave page now??

  18. yes, well its clear to me you are one smart cookie, the best part is you can explain what you find and why you are doing what you do to make it better. Sharing your gifts is the best part of the videos. Thank You again and again, Great effort and result. D

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  20. P R says:

    The 6X5 rectifier tube I noticed has the heater tied to ground, and if there is any heater to cathode leakage this will be a problem. Also it can introduce hum into the rest of the circuit through the heaters. As even with the best tubes there is heater cathode capacitance. I have been wondering why not two filament windings on the power transformer.

  21. Removal of the 12C8 would also deactivate the wattmeter.

  22. Your videos are amazing ../

  23. Have to admit, I would not "desolder" those capacitors, I'd cut them out.

  24. Thanx a lot Mr Carlson!
    I learned a lot!
    I am building a single ended tube amp,so this video came in handy!

  25. Jeff Page says:

    I built one of those (the kit) in the 60's… Used it for 30+ years until it was stolen along with all sorts of other stuff…

  26. roy escabusa says:

    Awesome piece of equipment and has more functions. I really enjoyed this video. I hope this device is one of your list to build and share with us in patreon in the near future. Thanks a lot mr Paul.

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