C2 – 63 AM/FM Radio Volume Control Switch

[Gerald L.]

My radio works fine after sending it off but the dial light does not turn on with the radio. The radio man wanted an exorbitant amount of money to get the dial light working, more than a radio core. The easy solution was to short the red and white wires behind the switch; and the dial light operates with the dash lights whether the radio is on or off.

When I saw Gordon Peterson’s post in Dec 2004 in the archives regarding a replacement on/off/volume/tone switch for our Delco AF/FM radios (p/n 7290296) I thought I had another issue solved. I picked up one off eBay a while back.

With the radio on the bench I now realize that replacement switch, thought essentially physically identical, is not the same as the one currently in my 63 radio; even thou the same p/n is stamped on my original switch. The replacement switch volume control pot’s resistance range is 21K ohms where my original is 10.6K ohms. If I install this replacement switch I believe it will make volume control extremely sensitive at the least; or at the most damage the circuitry or the speaker. Googling for Delco Model Numbers shows they are different 63 AM/FM 985686, 64 985921, 65/66/67 986281. Are there circuit differences, I don’t know.

I am inclined to leave “well enough alone” at the point unless I can receive some encouraging input off the forum. Or I might consider an external 12V micro-relay switch.

Can anyone shed more light on this subject?

[Jack H.]

Light, yes, confusion, no....

From my Chevrolet Radio books, here's the scoop.

The '64 Corvette version of the AM/FM radio calls out 7287620 for the vol/tone/switch assy which is the same as what you report for 1963. Additionally, a similar AM/FM radio was offered for full size Chevy's that year but its vol/tone/switch is listed with a different PN, 7287414. Now things get interesting!

In '65, there were four versions of AM/FM radios (Corvette, Chevy II, Chevelle and full size Chevy). ALL of these are listed with multiple PN's for the vol/tone/switch meaning it was a pick 'n choose situation on the assy line -- all are considered equal substitutes! The list consists of:

7290296
7290633
7290641
7290744
7291126

Exactly what the differences are between these parts, I can't say. The radio service & shop manuals do NOT define their specifics (pot resistance range, taper, power dissipation characteristics or mechanical dimensions).

Nor do the tech books describe any circuit 'tweaks' in the '65 version of the radio for rationale as to why there's such a wide range of component interchange or speak to why a single/different Delco PN is called out for the earlier version of the AM/FM radio....

My take would be: go install the replacement component you've got (it's not that big of a swap job) and play with the chassis on your bench. Do you find anything noticeable or objectionable with the substitute part?

[Gerard F.]

Re: C2 – 63 AM/FM Radio Volume Control Switch

Gerry,

I reviewed that post from the archives. Here it is for reference:

https://www.ncrs.org/forum/archive19.cgi?review=150571

Gordon Peterson's was a a 63 radio like yours and he replaced the tone-volume switch with a 7290296. You might ask him how he finally made out with the difference in the volume range ohms.

I replaced mine with the same switch but on a 67 radio (same as 65 to 67). I do have the 65 manual and wiring diagram for radio 986281 in a pdf format. It is about a 2.2 meg file, and if you want it, email me.

On the back of the 7290296 switch are 4 lugs, two with an R between them and two with an L between. I assume is R is radio and L is the light, it is a matter to determine which is the feed and which is the load (which should not be too hard).

Hope this helps, I'll be glad to email the manual and wiring diagragm.

Jerry Fuccillo
#42179

[Alan Drake]

Re: C2 Radio Volume Control Switch Resistance

Gerry,
If you have it out and on the bench then why not try a 10K resistor across the 21K if the Vol control seems objectionable? This should bring the 21K back down to approx. 10K

[Gerald L.]

Re: C2 Radio Volume Control Switch Resistance

Alan, great suggestion for a tweek, thou I believe a 10K resistor is too low and yields a 6.7K pot. When I play with this I will likely try a 20K resistor ... yields a 10K pot.

Thanks everybody. Gerry Lehmann