Add stereo to old consoles?

[frenchy]

Has anybody ever done a 'stereo' mod to one of these old tvs that have two speakers? I.e. add a stereo modulator to the circuitry so you get stereo from the speakers? Seems like it would be cool on one of these sets with the speakers separated so far apart in these big cabinets and would get great separation effect. (As opposed to modern plastic tvs with the speakers 6 inches apart!). Plenty of empty space in there to add a dinky little amp and modulator. Wondering what the simplest way to do this would be where you could have stereo, and still have the volume comtrolled by the tv's volume control? Any ideas?

[andy]

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[Big Dave]

On my big-ass Zenith, there is a switch on the power/volume assembly that puts the speakers in mono. That would be easily modified and reversable. Myself, i would use the phono/tape section of the radio for the sound. This would give more fidelity, IMO. Before I relocated (and had only 5 old sets), I had the VCR tied into the Scott and kept the TV sound off completely. Since I am a cheap bastard, if I can use the original equipment (with a little help), that's the way I go.

[wa2ise]

Originally Posted by frenchy

Has anybody ever done a 'stereo' mod to one of these old tvs that have two speakers? I.e. add a stereo modulator to the circuitry so you get stereo from the speakers? Seems like it would be cool on one of these sets with the speakers separated so far apart in these big cabinets and would get great separation effect.

TV stereo sound is very similar to FM stereo sound. The subcarrier frequency is lower on TV (same as the horizontal deflection frequency) vs 19KHz for FM stereo. Another small difference is that the L-R channel (which is double sideband supressed carrier, like FM) has some noise reduction applied to it, but you can safely ignore that. You could take an FM stereo detector box (the sort sold as add on for FM tuners), modify the tuning of the LC circuits to reduce the resonant frequencies down to match the TV frequencies (add caps across the LC circuits to shift them down within range of the adjustment slugs). You'll need to tap the TV sound detector before the FM deemphasis circuit, usually an RC circuit, to feed to the stereo demod box.

Another approach is to use an FM stereo demod chip. You could use an old walkman set, or an old ghetto blaster circuit board pretty much intact. Disable the FM tuner and FM IF circuits. There should be a small trimpot and series resistor associated with the stereo decode chip. Also a cap going to the same pin. Add another cap in parallel to that cap, the additional cap about 20% the capacitence of that cap. This should make it possible to adjust the trimpot to lock onto the TV stereo signal.

[frenchy]

I plan on doing the same thing I have with my other sets - run it thru a dirt-cheap VCR and tv set on channel 3, that way I can get remote control, plus the vcr boosts the signal up and gives a clearer picture, and more consistency in the color saturation between channels and never have to mess with fine tuning.
So if I'm starting at that point...the VCR already does the stereo decoding and would be outputing that to it's L and R audio outputs. Hmmmmmm so I could just run that to a small amp placed inside the set and route the internal speakers to that. And run it thru a selector switch to go back to tv sound it I want. But would have to put a secondary volume control on the back or somewhere to control the amp volume. Not the ideal way to do it but it would work, would cost about 25 bucks I'd think, a very little cheap Radio Shack amp would do fine for such small tv speakers. I'll think about it.....Frenchy

[blue_lateral]

a very little cheap Radio Shack amp would do fine for such small tv speakers. I'll think about it....

How about one of these ?

In the mid 80's I had bought a new Zenith color console....just after that stereo became available on the same set as mine. Went to the Zenith parts distribution center here in San Fran (now gone although the building remains) to purchase whatever board(s) or module(s) needed to convert to stereo.

Crabby lady kept telling me that it wasn't worth it, I kept asking her for a price so that *I* could decide if it was worth it to *ME*

This lovely person (IE BITCH) refused to quote me a price! It was one of the stranger encounters of my life! Shortly after this I rediscovered Heathkit and found that they offered a kit version of the next model up from my set, and with stereo....ARGH! At this point I couldn't afford to buy another entire TV even though I really wanted to. Heath closed up not too long after this. Foo

Anthony

[Chad Hauris]

I remember a Mitsubishi console TV which had true stereo speakers, before TV stereo broadcasting, but seemed to have an FM radio built in so that you could receive TV simulcasts in stereo that were brodcast on radio stations...seems like in the late 70's early 80's some radio stations used to do this for special events. This Mitsubishi also let you use a line input from a stereo videodisc or VCR to get real stereo on the TV sound system.

Saw one at a church garage sale but CRT was very well worn so I passed on it.

[andy]

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[wa2ise]

Back in the 80's, RCA came out with their first stereo TV set, the CTC131. The stereo sound decode was on a separate set of boards, and all you needed to feed it was some of the TV set IF tapped off the tuner output. A CATV splitter would work fine for that. One feeds the stereo decoder, the other the normal TV IF strip.

Another possibility is to raid an otherwise dead stereo VCR for its stereo decoder circuit. Again, split off the TV sets tuner to feed the VCR IF. Usually an RCA jack inside. Or just remove the tuner module and feed the IF trace from the TV tuner.

[frenchy]

[QUOTE=andy]You could hide one of these inside the cabinet. It will add remote control too.

thanks, tried to ask the guy if it came with the remote but ebay site is rejecting it. What does the remote do, volume control too?

[oldtvman]

sure frenchy you just get a soundesign unt and plop in right on the top and you have stereo

[andy]

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[ha1156w]

Look for a little box called the Recoton F.R.E.D. No idea where that name came from, but it has a probe that you stick on the back of the TV, which picks up the local oscillator. It derives the stereo output from that. Either that or it uses it to tune its internal tuner. I have one of those boxes, but haven't messed with it in ages. Has SAP and everything. Makes any mono set play stereo and keeps the remote (except for volume).

[frenchy]

Since I'm already running a cheap-ass korean stereo VCR thru it, I remembered I already HAVE one of those little tiny Radio Shack amps I had hooked up to a record player. Has volume and tone controls. I'll just route the vcr outputs to it, unplug the tv's speakers and connect them to the amp with the same type quick-disconnect pins so none of this is permanent, and put the little amp on top of the vcr, whah-lah! Can always unplug it in 20 seconds whenever I want. Hey then I can unplug all the tubes in the sound section and save electricity! Just kidding...Frenchy