Zenith ultrasonic remote control tuning

[RetroHacker]

I've got a Zenith System 3 console here, model SM2535X7. I've managed to get it to work fairly well, but, it would be nice to have the remote too. I have a remote here that I thought should be compatible, but, it appears that it's not. The buttons do different things, and I can adjust the pot inside to shift the functions slightly, but they currently do:

Off-On is channel number 4
Channel Lo is Volume up
Channel Hi is number 9
Channel Time Recall does inconsistent things
Volume Lo is channel number 3
Volume Hi is channel down
Mute does inconsistent things

So, either, this remote is totally incompatible with this set, or perhaps it needs to be tuned for it. I have not attempted to adjust the inductor, but, I figured I'd check here before blindly fiddling more. I don't have a service manual for the TV, so I'm not sure what frequencies it's supposed to use for things. I'm really hoping to get power and volume to work, at the very least.

[Electronic M]

Look for a Zenith ultrasonic remote with a RAT keypad like the NOS 124-14-01-R I've got squirreled away.

[RetroHacker]

Does anyone have a schematic for the remote control that I have? Or know what the model number is, or what set it's for?

[Jon A.]

I know it's for a System 3 with on-screen display. The remote you need has the same shell but six or seven small buttons, depending on whether or not that set has the zoom feature.

[zeno]

ACHTUNG !

This information if for an SM2535X NOT a 35X-7 !
The last number means there is some minor change to the set.

Remote called for is a 124-17-01
The 19" chassis ONLY calls for a 124-17
IIRC the only difference is cosmetic.
This is what it looks like.

http://www.ebay.com/itm/ZENITH-TV-RE...--mA0c-CRS-d_A

ALL battery operated ultra Zenith remotes use the same freqs.
Odds are the hand unit is bad. Never seen a set with that problem
or a remote that needed adjustment.

BTW the set is from the mid line. Mostly the same as top of
line but does not have auto on/off & space phone. Also the top
sets had IR remotes.

73 Zeno

[Jeffhs]

I don't know when Zenith changed from ultrasonic remotes to IRs. However, if your TV was just a bit newer, you could use a universal IR remote. Since yours is ultrasonic, however, the only solution would be to replace it with another, similar one.

Since, as was mentioned, every Zenith ultrasonic remote ever made used the same control signals, any such remote, even the fancy Computer Space Command hand unit, could replace yours. You would get a nice bonus if you replaced yours with one having a full 0-9 keypad, in that you would then have random access channel tuning and up/down scanning, not to mention the ability to set up a favorite channels list, if your TV supports that feature.

BTW, I have never seen or heard of an ultrasonic TV remote control unit as badly out of whack as yours seems to be. Seems to me that, as was mentioned, either the controller is defective or something is amiss with the remote receiver itself. I am tempted to think that whomever had this TV before you may have been tweaking the detector coils in the remote receiver, and wound up messing it up so badly as to hopelessly jumble the remote functions, not to mention disabling a few of them. Since your remote's mute button is unpredictable as to which function it will control at any given time (for example), not to mention other functions being just as unpredictable, this seems very likely.

I would definitely look into the eBay listing which was mentioned and linked to in the last post. The remote pictured seems to be in good shape, except for the numbers being worn off of a couple of the random-access channel selector keys. The seller seems reputable, owing to his consistent 100-percent positive feedback record, so it seems to me you can't go wrong buying a compatible remote from him.

[zeno]

Changeover was this time. I had an SM1971P with
auto on/off & space phone, it was IR. Remote he has now is from the
lower line sets. Although it has no keypad a remote with a keypad will
random access channels on these sets.

Remote receiver in set has amps then goes into the micro.
Just has sensitivity & trip point. Much better than tuning forks,
gives off a nice constant wave not damped off like the oldies.
So your keys, the dog or a train going by wont trigger it.

BTW All Zenith BATTERY ultras use same freqs. Tuning fork ones
are all over the place. For starters there was the on/off that was
white, silver, orange or blue all different IIRC.
MOST IR's also the same EXCEPT some non Zenith sourced sets
in the latter years.

Lets keep em running men!

73 Zeno

[Jon A.]

Originally Posted by zeno

BTW All Zenith BATTERY ultras use same freqs. Tuning fork ones
are all over the place. For starters there was the on/off that was
white, silver, orange or blue all different IIRC.

73 Zeno

Making tuning fork remotes that way must have been a cost-cutting measure. I noticed in one of my 600 remotes that the plastic housing that holds the hammers is stepped to accommodate the different rod lengths. Channel down on a 600 remote operates power/volume on my 500 console, but that button is in the same place as power/volume on a 500 remote.

BTW my Sylvania console responds to the 600 remote as well as an old Motorola clicker, just not very well. Of course that tuner drive is slipping.

[RetroHacker]

Hmm, so, what you guys are saying is that the remote I have now ought to work with this? I'll have to investigate further. Does anyone have a list of the frequencies the set is looking for? I should be able to hook a frequency counter up to the remote and figure out what it's actually producing.

Also, does anyone have schematics for this set? My local library used to have the Sam's Photofacts on file, but, I just went there today, and they don't have any of them any more, and they checked the other libraries in the area, and none of them have them either.

[RetroHacker]

So, I spent some time fiddling with this, and traced out part of the circuit in the remote control (no luck finding schematics for it). The vertical 10 pin resistor pack appears to control which button does what, as well as contain some critical resistors for the circuit which generates the frequencies. I have removed it, and figured out it's internal construction, mostly, and done a lot of experimenting with other resistor values. I eventually found the magic combination that gives me power on/off (also found mute, channel up, and channel number 1), but have been unsuccessful at finding channel down or any of the volume commands.

Currently, I have it back together with a few resistors replacing that resistor pack, giving me a remote that can only turn the set on and off. But at least there's some progress.