help with a cb circuit and SGS thompson74LS86N

[dss56]

So i have been using this little circuit for over 10 +years and i even have it submitted in a Secret cb volume.

Its for the mb8719/mb8734 pll where you cut trace on pin 16 so you can get the A channels 3a 7a 11a 15a and 19a. Also on any channel mods it will fill in the missed channels.
The little circuit eliminates using a 3 way toggle foe the channels like up for some /middle off and down for some.

The circuit is set for the single toggle on/off to control the channels no 3 way jut on or off.

So i ran low on the SGS T 74ls86n and also the second one pictured. Might be Fairchild with the F
I ordered some of the bottom ones that are suppose to be Quad 2-Input XOR LS-TTL- 14-Pin Dip.

well the bottom one ics do not work they are not switching to either hi or low when switching the channels so its acting like a 3 way switch.

Of course the SGS thompson and the second one pictured are hard to find, they are on ebay but $3.00 each plus shipping. Looking to buy 25 of them.

So I bought some of the bottom ones from ebay and Ali-express and did not work.

Is that possible as they are all labeled Quad 2-Input XOR LS-TTL- 14-Pin Dip and the pin outs look the same.

Kinda baffled. Any suggestions

 

[nomadradio]

On three of the five RCs you have to go down from the channel above, and up from the channel below on the other two. This is because the RC frequencies occur every five binary steps, but only every four clicks of the channel selector.

Had an idea a while back to put a LED above and one below the center-off switch. The state of the channel selector output would light one or the other LED, showing you whether to flip it up or down.

Never worked out how to do it, or show the operator whether to go to the channel above or the channel below, just a hare-brained scheme that never went anywhere.

An EXOR gate like the '86 parts is an idea I never had, but don't you still have to go to the channel above for three of them and to the channel below for the other two?

Bought a cheap logic-chip tester on fleabay years ago. Paid for itself identifying bad 4008 chips in Galaxy radios.

Did you pull up the output from the pin 16 wire coming from the channel selector?

73

 

[dss56]

If I use the SGS thompson and the Fairchild chip works great yes on some you go to the channel up or down but this circuit does that for you eliminates doing the toggle up down or middle up. its either on or off and when you go to the A channels if the toggle is on it will auto get the A channels.

Cant figure out why the bottom IC does not work I bought 50 of them and all the same, put in the SGS or Fairchild and good to go.

 

[nomadradio]

The bottom chip has the Texas Instruments logo. That's just weird. TI originated that component. The other brands are just licensed copies of it. Doesn't make sense to me.

73

 

[dss56]

Forgot I never had to use the pullup resistor for the circuit i have used for the past 10 years maybe it will need it with the bottom IC i will try that tomorrow.

 

[dss56]

yes got me baffled its a very simple circuit with a 5v zener diode a 1k and 220ohm resistor.
When I do channel mods I use this because on most radios in the front the slide switches are not 3 way just on off so this works perfect just use a slide sw on/off on the front.