DNT M40FM squelch stuck open

[LondonCbRadio]

A while ago i bought a joblot of radios that wasn't working and DNT M40FM was one of them. The fault on it is the squelch stays open even when turned all the way up. I can't find a clear diagram on this radio does anyone have any idea ?

[14CS06]

Hello

Schematic DNT M40FM









@+
Claude

[LondonCbRadio]

Thanks alot. r47 was missing so i replaced that but still not working.I'll have another look when i get the time.

[cubwolf]

Notorious for dry joints especially on the through hole pcb links. It will more than likely be the MC3357 if chip at fault.
My lovely boss back in the day bought a thousand of them all returns that i had to look at when no other repairs came in the door

[LondonCbRadio]

Notorious for dry joints especially on the through hole pcb links. It will more than likely be the MC3357 if chip at fault.
My lovely boss back in the day bought a thousand of them all returns that i had to look at when no other repairs came in the door

This one has missing parts and wires cut. Any change you have a photo of one open the top side ?

[14CS06]

Hello

Photos

@+
Claude

[LondonCbRadio]

Hello

Photos

@+
Claude

Thanks alot but i need photos of the other side of the board.

[14CS06]

Hello

Only this one

@+
Claude

[LondonCbRadio]

Thanks for that it looks like i'm missing a few parts.

[LondonCbRadio]

All the arrows are the part i'm missing along with a few missing wires. Do you know the value of these parts ?

[LondonCbRadio]

Anyone ?

[bitbang]

Not all of the M40's have this modification, I have seen ones with no components on the solder side, a couple of parts and the full modification as per what Claude has posted. There are also component changes on the other side too. Just in case you have one with a different modification.

The values on a M40 I have here (which is identical to Claude's) are:

M40_an.jpg

Hope this helps.

[LondonCbRadio]

Not all of the M40's have this modification, I have seen ones with no components on the solder side, a couple of parts and the full modification as per what Claude has posted. There are also component changes on the other side too. Just in case you have one with a different modification.

The values on a M40 I have here (which is identical to Claude's) are:

M40_an.jpg

Hope this helps.

Thanks mate i'll put them parts in and see if there is any difference.