Fixing Zenith CCII Avante 25JC49

[Alex KL-1]

Originally Posted by drwatson32

Like a nutjob, I snagged what I believe to be the correct paperweight to go with my giant paperweight. Joking aside, I remain committed to finding the tripler and getting this set working again. Here are some pics for the curious. I thought it was kind of funny how the PCB interfaces with the buttons with the same push-on connectors as the modules in the set. I can hear the power button, channel hi, zoom, and volume buttons. My phone registers the tones as being upper 8khz to mid 9khz. The other buttons seem to do something as my mic gets overwhelmed and shows 100db of all frequencies when I hold the remote right up to the mic with buttons pressed. Might be outside the response of the mic. I won't be able to test beyond this till I can power the set up again.

It's half tempting to fire this up again to see if I can witness what exactly went. I hate to break more things. Maybe worth disconnecting the flyback from the tripler to isolate that as being problematic? I have feelers out for a tripler but so far no luck.

Side note, I get 10ohms across the oil capacitor, but with it still in circuit.










Here, I noticed the ground strap from the aquadag cover (is that what we'd call it?) to the power supply board was baked by an adjacent wire wound resistor. The insulation is crispy now, but I pushed these apart from one another. Guessing this isn't of much consequence, but thought I'd throw that in here.

Intriging, this remote control is sonic (audible) or ultrasonic system? In case of ultrasonic, the ultra small MEMS mic from cellphone can be confused with high amplitude ultrasonic signal.

[zeno]

Zeniths ran somewhere between 30k & 40K. Ultras went away
apx 1980. they got them to the point of having full key boards with
near 20 buttons & made them very reliable. I dont remember any being
triggered by random noise like shaking you keys or the dog scratching his neck !
Zeno

[Alex KL-1]

Interesting!

[drwatson32]

Alex,

I'm guessing that the tones that I'm hearing and that my phone can pick up are a harmonic from the actual tone. The screen over the transducer is pushed in a little bit, maybe that's doing something.

At any rate, I assumed that the plastic clip that I broke is just for mechanical stability of the connections, went ahead and covered those in silicone as it'll lend to that somewhat.

I powered the set up at 60v and got snow on the screen, brought it up to 80v. All the functions of the remote work as they should. Then I thought I'd go ahead and shut it down for a while and savor the potential success for a while before pushing my luck further : P I didn't hear any arcing so far.

[Alex KL-1]

A little though of this curious subject...
Maybe, depending on the model, it are outputting audible tones with ultrasonic hardware, when it emits 2 ultrasonic tones (2-tone mode, but I dunno about models using this scheme), and it intermodulate. 8kHz audible can for eg. significate a 30kHz and 38kHz making a IMD difference tone.