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

I have a Uniden Washington with a PC-385 board and a MB8719 PLL. I was told it had a swing kit installed when I got it, other than that no other mods have been done that I know of. The radio did work fine with no problems, then one day I turned it on and couldn't hear no one on channels 1-14. With further checking I have found using another radio to key up to and people on the radio that channels 1-14 don't work and channels 15-40 are working fine. Also have noticed that channel 1 picks up people on channel 28 and I can talk to them. It seems that channel 1 is 28 channel 2 is 29 channel 3 is 30 and so on up to 14. Any help would be much appreciated Thank You.

It sounds like there could be a poor solder joint on the channel selector or PLL, either that or the PLL is failing and not switching channels properly.

Thanks for the fast reply, how would I go about checking the problems you listed.

Remove the bottom panel and carefully re-solder the wires that connect just in front of the PLL, and the associated PLL pins, and check the other end of the wires where they attach to the channel selector and re-solder those too, check for any bridged solder connections afterwards between the each of the wires and each PLL pin.

Thanks so far for the help Scott, I did everything you mentioned: 1. re-soldered the wires on the channel selector 2. re-soldered the wires in front of the PLL pins 3. re-soldered the pins of the PLL 4. checked for bridged solder connections between each wire and PLL pin. While checking for a bridged solder connection between the PLL pins I did notice on my multi meter that pins 12 and 13 are shorted but did not notice any solder connecting them. Are they supposed to be that way? Again any help would be greatly appreciated Thanks

it could be that they are both at the same signal level from the channel switch, so they are connected together at the switch.

Still have the problem as mentioned before, I noticed that I forgot to mention it on last post. Anybody have any info to share, I would appreciate it Thanks

OK, on CH1 the binary code should be 143-187 (actual), the physical code is different, due to pin 10 (64 bit) having an inverted input, along with it controlling an internal virtual 128 bit pin.

The physical code on CH1 is 15 through to 59 on CH40.

So on CH1 pins 16,15,14,13 should be high, and pins 12,11 should be low (pin 10 is permanently low as it is connected directly to the 0V track).

I suspect that you will find that pin 11 (32 bit) is high as well, which is shifting the radio up by 32 channels between CH1 and CH14.

To determine why that pin is high, you will need to disconnect the wire from the channel selector for that pin, whilst on CH1 and see if that changes anything (measure the voltage on pin 11), the selector uses a pull UP switch, with an external pull down resistor bank on the PCB near the PLL, so this SHOULD now pull the pin 11 down to 0V,, if it is not close to 0V try connecting pin 11 through a 1K resistor to the 0V track (the resistor is a precaution in case of an internal short in the PLL), when that pin is pulled to 0V through the resistor check its voltage again, it should be close to 0V, and the radio should then be on CH1 frequency.

If the pin is low as soon as you remove the wire you could be looking at a faulty channel selector switch, or a shorted track on its PCB, follow the wire between the pin 11 of the PLL al the way back to the switch, and make sure that there are no cracks or scratches across the tracks, also check for close to the same voltage at pin 11 and the output of the switch should be less than 0.7V difference), to confirm that they are connected together, switchs rarely fail like this, it is more normaly for them to cause LED display problems first.

If the pin only goes low when you pull it down to 0V through the resistor it probably means that the pull down resistor bank is faulty, and needs replacing.

If everything checks out and it is looking like the switch has failed, try spraying some switch cleaner (with lubricant) into the switch through the small flats on the shaft, be generous with it, just make sure it does not get into the display or meter etc, once you have sprayed cleaner into the switch spin it around a few dozen times to help work it through the switch and clean the contacts (make sure the radio is not powered at the time).

Let me know how you go.

Alright, first I went ahead and checked PLL pins 10-16 while on channel 1 here is what I got - 13-16 are high and 10-12 are low just as you stated it should be. So I seen no point in going any further with your steps since pin 11 is already low unless you think I should continue with the steps you listed. Thanks so far for your help, any other ideas to try as I am opened to suggestions.

Well, if the PLL pin is low, then the PLL must have failed, your only option is to get a new PLL, you will need to get a RCI8719.

Do they not make the MB8719 anymore? Is RCI8719 just as good as the MB8719? Can it be modded the same way as the MB8719 for channels etc.?
Any suggestions on where to get one and about how much they go for? In your opinion which is better the MB8719 or RCI8719 because I might be able to get a hold of a junk CB to take the PLL out of? Sorry for so many questions just never had to buy them parts before. Thanks again for the help.

The MB8719 is no longer made.

You can get the RCI8719, which is basically the same PLL, some differences have been noted under certain circumstances in the early days of the RCI8719, but it would seem that these days they are just as good as the MB8719.

If you can get a junked radio with the MB8719 then by all means put that in instead, personally I would just put in a new one, as you never know if the junked radios one is damaged.

Do not solder in the new part, install an IC socket, and just plug in the PLL, that way it is easier to replace in the future, who knows, there could be an underlying fault which caused the PLL to fail in the first place.

I have an extra RCI-8719 PLL chip that was a good pull from a Cobra 148GTL radio, if you need it, send me a PM. I'll get it to you.

Regards,
Rick (Triple 7)

Rick, could not PM kept coming up an error however the yahoo messenger does seem to work, but you are not logged into it right now. I might be interested in the PLL.

Oops, sorry about not being logged in on Yahoo, I'll leave it up later on today if you wish to contact me. I'll work something out with you. Cheers!

Regards,
Rick (Triple 7)

The initiating of Private Messaging is restricted to Admin and "technical helpers", this was done due to some abuse of the system, if myself or one of the official "technical helpers" PM's you, then you can reply and message normally.

Just wondering if one of the crystals could be bad because I was messing around with a realistic TRC-490 it has the same board as the Uniden Washington. The TRC-490 however was missing the 11.1125Mhz crystal so I put the one out of the Washington in the Navaho. The results were the same as the problem for my Washington I also should mention the Navaho does not work right as it came with the 11.3258Mhz crystal and is in need of an alignment I do believe. It only works on LSB which is actually AM but can't seem to use the clarifier to lock on to the signal but that is another topic which I might post at a later time. After rambling on you are probably wondering why I just didn't use the PLL out of the Navaho, problem is not sure what PLL is, because all the letters and numbers have been rubbed off except for 7903 E01 plus it is one of my dad's that he got off of a trade.

Does anyone have any more thoughts as to what the problem could be. As of right now I am looking to buy another PLL and try that, just seems weird when I tried the crystal in another radio had same problem. Any help would be much appreciated.

There is a possibility that the VCO is out of alignment, I'd try that first. mark where the current position of the slug is set at, and take a plastic screwdriver and ajust the VCO 1/4 turn either direction, and see if the radio locks on the lower channels. If it does not, it could be a PLL problem. If it does lock on, leave the VCO as it is, and run it. I still have that RCI-8719 PLL if you want to try it. Cheers!

-Exit

I happened to find a NOS MB8719 that I bought to try should be picking it up in about 2 days will let you know how it goes.

Oh, okay good, let us know what happens with that PLL.



-Exit

The PLL came in early just finished installing it and as of right now everything seems to be working ok. What a headache this problem has been if it wasn't for this site and the help I received, I would of had to probably take it to a CB Shop for repair and fork out a lot more money then I had to. So thank you to all that replied and especially The Defpom for being right about the problem and his speedy replies, thanks again problem solved.

I am glad that we got to the bottom of the problem, and to hear that all is well now.