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RCI-2950 no voice, only a rushing sound

kb8ufp

Member
Mar 15, 2011
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Howdy all - working on an RCI-2950. Receive working great. Transmit in all modes, occasionaly you can hear faint voice but over everything - on AM, SSB, and FM, there is only this loud rushing almost staticky white noise.

Virtually nil on output power. The weird thing is that the roger beep comes through loud and clear (and slightly dims the display when it does. I also inserted a 50mv 1khz tone at pin 1 of IC16 which also came through loud and clear on a nearby receiver. I pulled the finals just to see and they and the driver seem to not be shorted. So far the PLL side of aligning is going well with no oddities encountered.

Any thoughts?
 

I'd almost have to guess that there's a "leaky" or bad capacitor in the mike circuit. I would check all caps in that section, especially anything tantalum, those are notorious for going bad. Let us know how you get on with it.

Good luck!
 
Still working on this. Did what I could on the PLL alignment last night and started some of the tx align, I was listening ot myself on a couple diff radios and trying to tune for best sound. I think the PLL align took care of a lot of it, now I just am gonna get hold of an SWR/Wattmeter to do some more of it.

As it is now its still fairly unstable and I don't know why it seems the slightest touch sets something to oscillating wrong. Like mid-test it was fine txing all I wanted, but then randomly just went to a ticking sound. Had to redo the PLL align a bit more to get it back to that point. Its really weird.

I do have access to a scope but I have to bring it in to work for that after hours to do the sinad part.
 
I have been working on quite a few of this series of RCI products (galaxy turbo, 2950, 2970, 2917, etc) and the symptoms you described are exactly as i have encountered. The problem is in the main cpu. There is a fatal flaw in this design that results in the cpu going out. The cpu controls the main refrence freqs and if you check with your scope the signal will probably be severely distorted. I hade one that tx and rx over 5 channels wide...clearly. Again back to the cpu..bandwith is controlled here also..some will randomly jump freqs...the display remains the same but output freq is off..ive encountered strange symptoms from these. As of yet i have not been able to find replacement "modules" (repair is not an option either) for these. I have a post here looking for info. Some say heat does it like the HR2510..same chips..diffrent setup..i think the system is too voltage sensitive and the mods take it out..im not sure. f you find replacements please let me know..hope it helps...hope im wrong..but thats a classic death toll for an RCI.
 
Bah. If thats the case - $50 down the crapper. Found him at the hamfest tailgate section so I knew what I was getting myself into. Receive works very well so maybe he becomes a base station to rx 10m?

Having just about finished things up on the align tonight your description is exactly what this rig is doing. I suspected CPU trouble based on how unstable it was. Nothing analog is that freaky right?

I've emailed a local CB and radio repair shop (believe it or not there is one still around, Bell's CB fairly close too!) listed on rangers site as a warranty repair shop- I'm also gonna stick my neck out and look for a wrecked rig or SK estate or something and hope I can get my $50 back out of this guy.

I don't have the greatest feeling that the tech there is willing to outright sell me a cpu board but he only wants another $50 to "tune and repair" + parts. Its still less than any decent used rig so if he won't sell to me and I can't find at least there is an 'option'.

Thanks for the info, I'll be looking out.
 
You can also reset the CPU and see if that helps. My Galaxy Saturn Turbo (same CPU as what you have in your 2950) had an issue with just "shutting down" at random, I disconnected ALL connections to the CPU, removed the battery, reinstalled the battery (in my case, a battery "pack", I use (2) AAA batteries), reinstalled the jumpers, and reset the CPU, which I believe is touching 2 pads on the back of the board, and now I haven't had a bit of trouble since. Give this a try, and let us know how you get on.

~Cheers~

P.S. If you find that the radio DOES have a failed CPU, I'll buy it from you for what you have in it.
 
Local guy doesn't have any stock and would have turned me away based on symptoms. Says he also hasn't seen a working CPU board in a while. He also recommended reset + RPL CR2032 (thus I have the original RCI-2950 with battery on CPU board). He referred me to radioshopsupply.com - guy is cool, but also didn't have the CPU board. You guys aren't kidding - this thing is rare.

This AM I scrubbed the board with alc + visually inspected. It looks factory with a few touch up spots where someone had at it. Tonight I'll try a new CR2032 that I have here now and a reset, might hit a few spots that looked a little crusty, but basicaly - nothing was wrong with this radio besides that CPU. Had a nice 9+ watts out into my meter before it starts to go whacky.

I'm going to ask on sparkys and qrz.com and here and watch ebay for a bit maybe but I might take you up on it.
 
This all gets me thinking... I hope that my voltage to the CPU isn't too low on my Galaxy Saturn Turbo... I replaced the power supply with an ATX computer power supply I converted, and the voltage now to the radio is 12.3V vs. 13.9V with the old supply. Makes me wonder if regulating the voltage to the CPU would help in reducing any chances of CPU failure... hmm...

I have far better voltage regulation with the current ATX supply than with the old supply, but I suppose using a LM7812 regulator IC would be worth the time to install on the CPU? I may have to look into that.

~Cheers~
 

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