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RCI-2950

K

kb8ufp

Member
Mar 15, 2011
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0
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Howdy all,

Have an RCI-2950 (working on it for a local) that is currently stuck on Scan+. When I turn on it goes straight to scan+, it scans upwards and no response from any of the keys on the keyboard. Only "Split" makes a noise and changes the direction from + to -.

This is not the original problem but this is a new issue. The original problem was low output (3-4W on AM and 8W on SSB max.)

I replaced several components around the finals including the 1 ohm resistor which was open, and a 220ohm which had gone hi to 400 ohms. I also RPL the driver temporarily with a 2sc1018, which brought the radio to LIFE. I was getting over 10W on AM and 35W on SSB (which is normal), so I was actually finishing up doing the transmitter alignment when I noticed the rig was just going scan+. (I have a 2sc2166 coming for a proper replacement btw).

SO CLOSE, but I think this scan+ issue is something wrong with the CPU board now and nothing I did, jsut a coincedence or I zapped with static.

Has anyone been able to fix a 2950 that only goes to SCAN+?
 

It could be a few things.

1. Take the button board off and clean it thourghly. maybe even check to see if there is constant continuity across that button making it seem as though someone is pressing it. theres a chance some solder/metal flake have contaminated it.

2. The back up battery might be dead or dying. This is known to cause all sorts of issues in these radios. you cant just remove it either. What I do is go get a 2x AA battery holder and modify tit for AA's. Much easier to source, last longer and easier to change when needed. PS newer model 2950's dont have this battery, but a cap instead. Check cap as well!!

3. The CPU could be the problem, BUT and this is a BIG but. It is most likely the Regulator next to the proc. 9 out of 10 times this is what it is. Problem is, I dont think you can find them anymore. The reg is U2 I think??? Been awhile!
 
Im with Rich on the idea of something on the board or in the button also seecond on the CPU going bad but this sounds more like a stuck or sticky / dirty button. Is this a model with a memory backup battery?? If so unhook power open radio and disconnect the backup battery for awhile and rehook it up to try and reset the CPU.
 
1st Im with Rich on this being most likely a dirty or sticky button or something on the board.

2nd yes the CPU could be going bad but Im leaning tward option 1

If thats a model with a backup battery unhook power open radio and disconnect battery for a few minutes then rehook up backup battery and power it backup to see iff CPU wipe or reset fixes it.
 
SORRY FOR THE DOUBLE POST. I posted a reply sent it and I got an error well ofcourse you backup a page and all is gone and it never even posted so I do another and now look and both replies appeared!!! Gotta love the net!! :LOL:
 
This is the new style CPU board with no battery or reset button. This morning I only had a chance to check the cap (1 1000uf) and noted that while on, the voltage was up around 5V. Within seconds of turning the set off it had dropped to 1.5V and quickly dropped to 0 in a couple minutes.

I completely removed the button board, same issue. The mic is unplugged. As its a fine-pitch part and I really doubt it would EVER work again if I started to unsolder that thing (And if I recall a programmable part, more akin to a microcontroller) - I really doubt the scan+ button is depressed (electrically or physically). Like I said the unit was working perfectly, and I noticed while transmitter alignment - that the beeping had stopped and I had no output.

Also the regulator has 12V in and 4.99V out. I think its good.

Anyone else have any thoughts, or interest in a nearly perfect RCI-2950?
 
I've analyzed the Microcontroller datasheet and cpu pcb schematic and found a number of really interesting things.

1. Ranger built this design without any esd protection whatsoever.
2. The up/down buttons going out to the mic are directly connected to lo-current CMOS I/O pins, the pullup is done internally. The inputs are sensed by a NAND gate, one pin is held to ground, the other pulled up and signalled by grounding the pin.
3. Total power dissipation in the CPU for all pins is fairly low, something around 100ma if I read the sheet right.

Now lets say you are an aspiring tech with some gear, but not everything under the sun and you are working on a radio with exactly 1 mic and no spares to plug in for the audio signal generated portion of the tuneup.

You do what many hams have done before, and thats take apart the mic and wrap your siggen wires around the DPQT PTT button inside the mic. Thats a yellow wire inside the mic housing. The ground is just underneath the PTT switc, and not wanting to further take apart the mic sort of jam the grounds into each other (that is from the siggen)

Notice that I made no mention of the mic buttons because I didn't consider (or realize) that they went directly to the delicate CMOS structure of the input pins on the microcontroller.

Everything was going well, I was getting full output finally, just checking further back and trying to figure out why even though everything looked good on the output, that I had a lot more bias on the driver stage than I should (about 120ma).

So basically this procedure took a couple days, during which time I had paid no attention whatsoever to ESD. Rubber soled shoes, linoleum floor, carpet in the other parts of the house, working on the kitchen table, etc. All the while holding the falling apart mic with the siggen attached and trying to probe all at the same time. Every time I sat down and picked up the mic I was basically molesting the crap out of the delicate input pins with who knows how much static.

I'm nearly positive of this diagnosis, shorting directly the pin has no effect, neither does any other pin. It has different impedance than the rest of the pins too.

I did the reset procedure (hold reset pin on ucontroller high to Vcc for about a second on power on) - I'm certain it worked.

So a new lesson about older electronics - they are just as subject to ESD as anything else.

Anyone interested in an RCI-2950 chassis with a bad CPU?
 

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