unknown Mod

[sideswipe]

Hello all;

I apologize if I posted this in the wrong spot I am new to the forum. I bought a tote of CB equipment really cheap and it had this grant XL in it. the radio is modded with variable power and xtra channels and it also has this mod on it and I can't quite figure out what it is or does. anyone clue me in on exactly what this is? I think I got the picture attached.

 

[W5LZ]

It automatically lowers the bathroom shades to maintain privacy...
- 'Doc

 

[fnkycoldmedina]

looks like an attempt at a swing modification .but unlike anything i have seen .personally i think i would remove it .especially if the radio is getting bad reports .

 

[sideswipe]

Thanks for getting back to me, the radio has excellent swing I can set it to DK anywhere from 0-4 watts and it will swing up to 18 on my new meter I just got. the meter is a dosy TFC 3001-s . I haven't had any complaints, I was just curious to what exactly it was.

 

[sonoma]

that is a audio mod. will not hurt any thing. I have this on all my uniden xl lt and cobra 148. should be about a 10uf cap there.

 

[9C1Driver]

If it's working and sounding good I suppose you can leave it. A Grant xl is usually good for 12-14 watts peak on AM and 14-18 on SSB.

 

[Robb]

Hmmm . . . Looks like two 1n914(?) diodes with one end tied to ground and the other tied to ?.

The electrolytic cap goes between the power feed of the audio amp to a ? point near the AM Regulator.

Can you take some closer pictures - if possible?

Maybe Xit13 has seen this before.

 

[sideswipe]

thanks for the reply, here are a few more pics. the diode looks to be connected to the big resistor. the grey 3 wire just goes to the variable power. I was just curious because I've never seen it.

 

[Tallman]

Good job on the photos

Well done. Up close on circuit boards is hard to do.

 

[ExitThirteen]

It's a modified version of the original 10uf cap compression mod I was experimenting with recently.

By the way the diodes are setup, it appears as though it's using .7V as a reference voltage. Perhaps it's a way of taking the negative loading off the audio IC, or a simple form of a voltage divider.

The other diode in question (since we can see that one diode goes to ground) goes to the junction of D63/R228 near VR10, which controls the AM deadkey.

Sideswipe, see this thread for further details on what that mod does to your modulation on AM. I do a couple variations of this mod in this thread.

http://www.worldwidedx.com/general-cb-services-discussion/163831-over-130-modulation-7.html


~Cheers~

 

[sideswipe]

Thanks for the info, and that thread is very impressive, makes me want a scope now. Are the diodes something that you might possibly test to see what kind of impact it has on the modulations and compression? In the future, I'd like to have someone look at the radio who has the right equipment and see if anything thing else needs / should be done to it. I live about 2 miles off exit 121 on I-65 here in Louisville and talked to several truckers passing by, I've been told on this particular radio that I was loud and really clear by everyone I talked to. I put a D104 on it and had to dial the mic gain back to about 10 -11 O'clock. other than that, I've not touched anything. just talking on it.