Heathkit IT-12 Signal Tracer Video #2 of 2 - Troubleshooting the Troubleshooting Device
Vložit
- čas přidán 16. 03. 2021
- After doing nothing more than installing a cloth speaker grill cover, the tracer has unexpectedly stopped working. I troubleshoot my way to a surprising cause and now I have a great little tracer with a special capability of locating noisy components.
- Věda a technologie
Troubleshooting is both art and science, with science being dominant. Jim’s troubleshooting technique can be summed up thusly: Ooh! Shiny!
It's Voodoo... I know for a fact he uses all sorts of witchcraft...
52:10 so lets recap; the tracer is clearly going into wild oscillations once the volume is set past 60%. Yet it is called good enough and ignored. I would not put such a thing into shop service. But seeing the state of the rest of the equipment that signal tracer is probably a perfect addition to that shop.
Those exposed terminals on the bottom right corner of the front panel have HT on them. I’m waiting for JIM to “discover” that. He should screw the covers back on.
If you get a little cat bed for your cat on the workbench someplace, I will give every video a thumbs up.
One of these days I’m betting the cat will get lit up. Nobody would let a cat wander on a bench with live line voltages at 120AC and tube voltages up to 450vdc. Cats are curious and could paw something it finds interesting in the blink of an eye! Bye bye kitty. That would be a horrible thing to happen. He needs to keep the cats off the bench period! Just to break them of the habit. I’ve tried to give him good advice, sent books to him, schematics...... always appreciated but never seems to use any of it. Nice guy that needs a different hobby. After all these years mistakes made doesn’t teach you not to do it again, time to change hobby. Anybody with a bit of common sense and respect and a decent knowledge of electricity should be able to fix these basic tube circuits.
@@SIXSTRING63 Couldn't agree more. Not to mention other risks for the cat like hot soldering iron and toxic chemicals. Plain irresponsible.
@@SIXSTRING63 any thumb I can muster up for your comment.
On the cat; I am less concerned about the cat than him. Every time one of the cats just as much as maunzes he gets distracted and loses track of what he is doing.
And regarding his mistakes: I completely agree. Mistakes are natural to be made, but meant to improve and learn from. But neither does he try to improve nor learn. Always the same groove. How often has he been on pink elephant chases caused by his wonky clip leads or meters. One would think he would take a day or even week to fix up the equipent. But instead more and more equipment breaks down and stays unfixed.
@ 40:51 Hey Jim, you have a highly conductive atmosphere in your shop - The probes are 10" apart and the DMM reads 51 Ohms... You're the man, Jim !!!
The switch to the speaker is to isolate the speaker itself when used as a ‘shop speaker.’ If the switch was not there, the internal output transformer secondary would be placed in parallel with the transformer of the device which you were using to drive the signal tracer’s speaker.
I think you need to replace the tube socket on that Weston tester Jim.
I have had to do a similar job, a bit of a pain but the only way to trust the tester again.
Cheers,
Well seeing his habit of mixing up wiring in previous radios (and blaming it on the manufacturer as being broken from the factory) I would not suggest to replace the socket in a wire mess like a tube tester. How about using proper deoxydizing contact cleaner first? And proper contact cleaner does not refer to that blue household can of WD40 snakeoil or throttle body cleaner or 70% IPA.
But even if he did replace the socket, how long you think it will take for the flimsy contacts in the modern sockets to crack under mechanical stress from excessive wiggling of tubes. Or do you really think that he will go the extra mile and source rugged surplus sockets?
34:03 Nothing is conclusive there. The speaker switch does not only connect to ground it connects to the second wire of the speaker too. So even with the switch open you would read sort of continuity across it and to ground because you measure through the secondary of the output transformer and the voice coil to ground. Right there anyone who looks at the schematic must conclude that an open with the speaker switch open is sign of a missing connection in the loop formed by the speaker voice coil and secondary of output transformer.
Hi Jim. I have a question. I ran across one of your videos about "stuff" behind the knobs on a peace of test equipment. Is this the one and what was the results ? It is killing me LOL ?
Jim,can you please scribe "J.L. Was Here" onto the back of any equipment you've happened to repair.Thanks
The sparking around the output valve is because you have high volume signals across the output transformer and the transformer secondary is un terminated resulting in VERY high voltages on the plate of the output valve.
That switch is for internal and external speaker
Another usable piece of equipment for the shop. Jim's shop, not mine!
The transformer! You got it Jim. Check the voice coil connections. If the transformer was fried you wouldn’t have got signal on that output transformer terminal.
Loosen those 2 screws and get the Eye tube out of the way! Also, he didn't add the speaker spacers back in, (although that won't kill the speaker from working!) Another Ho-Hum job! Still NOT right!!
So he puts his finger on the terminals with HT on them.
Terminals of which he is aware that there is HT on them because he measured it minutes before and went "oh my gosh there is voltage there I need to screw the plastic caps back on..."
You've insulated the speaker with the new grill cloth !!!, the original grill was a metal grill and rusty.
This is a regular love fest in here.
I suspect the speaker is not connected.
40:04 anybody notice how his DMM set to ohms and the probes connected nowhere displays a negative resistance instead of OL? And at 40:41 with the leads open again the DMM now displays a positive value instead of OL? So how reliable you think are any measurements with that DMM ?
For crying out loud service the equipment! It is a joke that despite having a huge signal generator you need to resort to using a sweep generator with that annoying howl as audio source. Every clip lead you use is broken and sends you on a half hour wild goose chase.
That tube is noisy
Why is it so difficult to find the fault,I don't understand the logic at all!
43:54 That is no overlaying voltage reading! You clearly have one test lead in your hand so it is floating. How can this be a voltage interfering your resistance reading then? That DMM belongs in the trash. Get the basics down! One wrong conclusion and assumption after another.