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

hello,
i have here a RCI 2950 (older model with.. the jumpers..EPT291250Z)
it is a great radio. though I have a little problem with it..
sometimes, when I put the radio on the sound is very...very still (i have to put my ears on it and volume completely open to hear something)...and at this same time I can not transmit...

Sometimes when the radio works fine...it sudden drops the volume ...with the same results...
the rig appears to receive when it does that..but I can not send..and almost hear nothing..
it does that a lot lately..and no timing for it.. it is not regular..
any idea what might be wrong?
tanks

Check the solder connections at the audio chip. When looking at the radio with top cover off and controls facing you, the audio chip will be bolted to the right side near the rear of the radio.

I allready had a quick look...seems ok...will resolder them in a few minutes...
question:
when audio chip is failing..does this influence on transmission? is the same chip used here for mike amp? if so logic conclusion.
thanks for reply "timrim", it is appreciated. 73's

resoldered it...still the same...just noticed when the problems appear, no squelsh...

Check, IC6 and IC15 there are both 8-volt regulators, you should have about 13 volts on Pin1 and 8 volts on Pin 3 looking at them from the front. You may find cold solder joints around them. It may also be worth have a poke around the copper side of the PCB with a plastic needle, to see if you can find a cold solder joints.
Let us know how you get on.

Hello Rick,
first of all, thank you! for your precious time!
I think you mean IC6 and IC15, (not 16)
both give 13V on pin 1 and 7,95 on pin 3...maybe good to know, usually once the rig is working..it will keep on doing so....it is very rare that the problem occures when the rig has been working for say 5 to 10 minutes...unless I remove the powerchord for a while..
capacitor problem??
I will now go for a night of sleep. it's getting late here and.....(my eyes are tired..) tomorow morning I will follow up your advice and search for cold soldier joints in this area.
and surely will keep you informed...
thanks again
michel

ok, i checked the solders.. the ones on IC15(powering the audio chip) looked misserable...
so removed the old solder cleaned it up and resoldered it...
the rig is working fine now allready for 3 hours ..I will keep you informed about further evolutions...but at first.. it seems ok..
Thanks for that Rick!! much appreciated!!!

new update....well it seems like I shouted victory to fast...the rig worked fine untill yesterday....and now it 's doing it again..sudden volume drop, no modulation, and no tx, all the display functions are working..
also IC6 and IC15 apparently working ok when the problem occures..voltage is ok...any other Idea where I can look..maybe the audio chip??
any help would be apreciated..
thanks
michel

The problem with early 2950 is that they suffer with cold solder joints and they can be hard to find.
The best method is to have the radio switched on and have a poke around the copper side of the PCB with a plastic needle, to see if you can find a cold solder joints.

I am not saying that you do not have a component failing but its most like to be a cold solder problem.

ok, thanks again Rick...will do this saterday..with a little more time

you were completely right!!
hard to find indeed but not impossible..
<img src="http://www.dezangers.be/RCI.jpg">
thanks again Rick! I own you one!

Mine has the same problem. Or lots of. It's an old rig and the former owners take no good care of it. It seems it was working on a car or truck since there are lots of dust and tiny wooden carves. Well after a carefull cleaning, I found at least 10 cold solder joints, one of them on two legs of the Q53, which is holded in place just by the solded joints, but it is a little heavy to be solded just by the three legs and the hole heavy part oscillating any time the truck (I'm guessing) passed a hole on the pavement. Also C208, C322 and C207 needed to be replaced. I think now the board is OK. Next step: the plugs and cables that connect the board to the CPU and controls (pots).
thanks for the tips.
Carlos Saraiva
Santo Amaro Island
SouthEast Brazil