The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Argg !!! The original problem with this was NO TX NO RX. I replaced the PLL chip.
Now I still have no tx ( relay clicks over etc ) and very very faint RX.
The PLL is working as i can select channels.
If I turn the volume up and inject a signal ( local signal ) the RX will come up ever so slightly.
Any ideas ? Im stumped
Oh and the audio chip is working as the squelch control , is it the mixer ?

Sorry guys , any suggestions ?

Cheers.

I have not seen one of there radios for a long time, but I seam to think there was a problem with 2 transistors which was configured as Darlington and an R which formed part of the bias for the Darlington, which is in turn the main a voltage regulator, the R used go HR and stops the Darlington dead in its tracks.

I have tried looking for my diagram but with no look, so I cannot tell you the circuit ref no.

Rick.

Thank you Rick , I'll go through the diagram.
Warm regards.
Ray.

this may or may not be of any help but i had a 352 and then i went to the newer 4740 and both those radios were loaded with cold solder joints..I had to just about resolder the whole boared on both those radios but that solved my problems..just a thought

Hi Mate.
Thanks for taking the time to reply.
I do realize these radios have plenty of dry joints , but this radio was working till I shorted something out. Yes I know
As I wrote earlier , replaced the chip ( pll ) and the radio now selects frequencys but audio is non existant ( almost )...pwr supply ???
Cheers.
Hey Rick I sent you an email via my work hope you got it.

Hi, did you manage to sort out the problem? I"ve got the same thing here - the radio is near spotless and I'd like to get it going. RX is fine after a tune up and realignment of PLL to lock it up. TX works, OK on AM full carier, but low mod almost non existant. SSB is working, but again very low modulation and drive - on tone or a 'whistle' power comes up on but I'd not want to be yelling all the time.
Any ideas?

There are a few thinks that can cause bad TX audio on this radio.

You need to test the PA is working ok before do any more.
If the PA is ok, then check the following caps C306, C314, C316, C318, and C322.

Now ever if the PA is low then check the following caps C204, C205, C207, C209, C210, C211, C212, C213, C214, C216, C217, C218, and C219, I know this is long list of caps but as the radio is now very old any number of them could have failed.


Before you pull any caps check for cold solder around CR203, CR204, Q201, Q202, Q203, and Q204.

i know the radio i had as 352d and a 4740 and a 4730 the pll is a 40013 the pll is obsolete to buy here in australia .but it sounds like its out of tune or maybe 1 of the coils for rx is shot or needs a good tune up .the 4740 i have one down in the 26300 orso region but they only went as high as 27705 plus they have a 5khz step pin on the pll that saves wiring up a clarifier,i hope this helps dave nsw australia

Radioham01 wrote:Hi, did you manage to sort out the problem? I"ve got the same thing here - the radio is near spotless and I'd like to get it going. RX is fine after a tune up and realignment of PLL to lock it up. TX works, OK on AM full carier, but low mod almost non existant. SSB is working, but again very low modulation and drive - on tone or a 'whistle' power comes up on but I'd not want to be yelling all the time.
Any ideas?

Hi mate , change the xtal element OR try another insert. Be wary though you must check the impedance of the change over.