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

zodiac

If you have a black fronted radio it should have both a fine and coarse tune but if it's grey then it only has a clarifier and will need to be unlocked. Follow the blue and grey wires from the clarifier to the PCB board and remove them from the PCB only. Put the blue wire in the empty hole next to t...

zodiac

Remove the TX wire from pin 3 on your radio of the mike socket. Put a diode IN4001 to the wire just removed with it's unbanded end to the wire and a 1k resistor to the other banded end of the diode. Place the other end of the 1k resistor to the 13.8v at the on/off switch and the banded end of the di...

zodiac

Steve,
D44 is for Mid and Hi bands, you have unlocked the clarifier haven't you ?.
Dave.

zodiac

That's because they are, I said D1 is on the crystal board, I didn't say D4 was as well.
Dave.

zodiac

I don't have a schematic for that radio but check the PLL's pin 1 to see if it has 5v.
If it doesn't then find it's zener diode it's close to the PLL and should be at 5v,if not replace it with a 5.1v zener.
Dave.

zodiac

Anway he's found the fault now, it was a bad connection on the mode switch, I think!.

zodiac

Steve,
I'll have to look at the schematic for that.
D3 and D13 out of any UK Cybernet rig with the 134 board in it, Harrier Rotel York etc, or D4 and D1, D1 is on the crystal board of the Concorde 2 or again any 121 boarded Cybernet SSB radio Higain 5, Cobra 150, Tristar 747.
Dave.

zodiac

Steve,
It's a Jumbo (Cybernet) not a Uniden, they don't have any binary adders they switch to a different crystal for each band.

zodiac

I'll have to think hard about that Steve.
Ok I'll never use it but I'll find you a couple of diodes that'll do the job.
Dave.

zodiac

Steve, I forgot to mention that I did about 6 or 7 Grants many years ago with zero switching from super low to the UK 1 to 40, with Alphas and without unlocking the clarifier. I used one crystal for the 4 FCC bands and one just for the UK band so it could be tuned for the UK offset of 1,25kc's on FM...

zodiac

Klaus,
Spectrum Communications in the UK have the MC145151P at £6 plus post.
Dave.

zodiac

Steve, I am working on an Eprom to use with the original MC145106 PLL that's fitted to the radio, that will give the zero switching, the only thing is it may need the crystal change. Then you'll need a 4 pole 5 position rotary switch, as fitted in the Cybernet SSB radios like the Tristar 777, Nato 2...

zodiac

What MOD Steve ?.

zodiac

That's normal Steve, you have to change both the varactor diodes D40 and D44 one for each crystal to get it to shift further for the same as what's in the Cobra 148GTL DX MK2 MV201, have you got a scrap 148, if so then shame on you. You can also use two ITT410 out of a scrap Cybernet radio and that'...

zodiac

Klaus, You can still buy the MC145151, google MC145151 PLL, below is just one add for them. Integrated Circuit Stock and Pricing Details Stock Status: Available in Stock - Shipped in 5 Days Price: £14.25 Excluding VAT for UK & EU deliveries Quantity: Add to cart Wholesale Prices Quantity: 1-9 Pi...

zodiac

Hi Klaus,
How many MC145151 PLL's do you want ?, I do have some but not too many.
I converted about 6 Stag 357's with the MC 145106 PLL to 4 bands ( 26.065 to 27.855 ) with zero switching using pin 6 of the PLL with an EPROM, good old radios the Stag.
Dave.

zodiac

The answer is, NO but they don't fit it to there newer radios.
Unplug it and do without the front light, it's the only way to shut it up.

zodiac

Found this on openchannel.uk Don't know if it's the same as your radio. 1/ Remove the lid, top and bottom not forgetting the two screws in the back. 2/ Look at the back of the front panel and you will see the processor with various links by it. 3/ Locate the Links S1, S2, S3, S4 and remove any links...

zodiac

Dogem250,
What PLL, it doesn't have one ?.

zodiac

As you say your using LED's you'll be adding resistors in line as well, so give it a try you'll soon find out if you have any problems with it and the resistors will protect the circuit, as you'll only be using milliamps.
Let us know how you get on with it and what you've done.
Dave.

zodiac

Problem resolved. It was the CW socket that had a single strand of wire from the speakers 0v lead that was causing the problem. I decided to remove the socket just to make sure it wasn't shorted as I was convinced it had to be that after checking everything else, even though I'd checked it for a sho...

zodiac

Radio Make and Model:MK2 Cobra 18GTL DX PCB Number: PB 010 AB PLL Number: MC145106p Test gear available: Loads Symptoms: TXing all the time What is working:TX What has been tried: see below Did it suddenly happen ?: Yes, when it was thrown against the wall. Anything else that may be of help. I have ...

zodiac

0.69v is fine but the .73 needs correcting it's too high.
When you have corrected it check the voltage at the VCO's test point TP2, (that's the lead of R126 behind pin 7 of the PLL) on the highest channel and band, as Ray said above, you might have to slightly adjust the VCO.

zodiac

Check the base pins of the driver and final to make sure they are not over 0.7v with a dead key on SSB and the mike gain off.

zodiac

Check the screws that hold the main board to the chassis to make sure they are tight.
Dave.

zodiac

Your learning.

zodiac

Have you tried CBTricks under CB information.

zodiac

It's not just your set they all have some RF floating about but it doesn't cause any problems normaly.
Anyway, your now Animal the RF tamer.

Dave.

zodiac

What make is the radio ?.

zodiac

Did you want your rig fixing or a brew ?.
Dave.

zodiac

Are you using a power mike as they pick up noises that we can't here. When testing for carrier on SSB make sure the mike gain is fully anticlockwise. It's stray RF that's causing the problem and you need to tame it. One way is to put a short piece of insulated wire from the Emitter of the 2166 to th...

zodiac

Some people know how to creep.

zodiac

Steve,
I've had the same problem with the Grant and 3900.
If you lift the lid (top) of the radio at the back about 1 inch it stops, give it a try and let us know the result.
Dave.

zodiac

Try changing the electrolytic capacitors around the audio IC. Two of them are only 10v but change C132 first 330uF @ 16v.
Electrolytic capacitors dry out with old age and cause problems.

zodiac

Richard,
Have you checked the components that Scott told you about and what did you find ?.

zodiac

Thanks Scott,
It's working now Iv'e cut all the wires shorter and found a wire in the wrong position on the main board.

Thanks again Scott, all I needed was a bit of encouragement.
Now for some fun.

Dave.

zodiac

Thanks Scott,
Good job I didn't wire them the wrong way round, that's through rushing, so I've corrected it to how it's wired.
I've wired it as you said Scott and it's no different also the KC shift doesn't work, again and again

Dave

zodiac

Thanks for the encouraging reply Scott, that's just what I needed to know, that it will work. I've asked the same question on other forums and so far only had one sensible rely and yours of course. Now I need to work out the pin connections and I must add they do confuse me as to which to use and wh...

zodiac

If any one of D1 to D4 had gone short curcuit it would have blown the mains fuse.
Other than that, as Scott says.

zodiac

Has anyone ever used or fitted a MC145151 PLL to a CB radio. My intention is to fit one in a 3900 to give it the facility to switch down to the zero's. The MC145106 runs out of binary when pin 6 is switched on even with a crystal change for one that's higher than the original. The MC145151 has a hel...

zodiac

Richard, From what you've said it would appear to be wired correct. The coarse fine tune should both be at the 12 o'clock position when making the adjustment to the added 4.7k VR. You did say that the radio was off frequency and maybe that's the reason why it won't tune in but if you look at the mat...

zodiac

Richard, I forgot to mention that one of the wires from the VR needs to be wired to the same switch as the one you are using to switch to the UK band, it goes on the other pole or other side of the switch. The switch should be a two pole switch with three pins on each side making it a two pole switc...

zodiac

: KC.png (18.67 KiB) Viewed 21397 times

Connect a wire from the 4.7k variable resistor to the unused hole for L35 at the front of the board, this leads to the centre of the KC shift. Connect another wire to 0v Grnd back to one of the other pins at the VR and adjust the VR for the UK off set.

zodiac

Try adjusting the VCO slightly to see if you get any more channels than you've got, somebody might have been playing with it, like they do.

zodiac

You could try Richard at Truck-King, he may be able to help you.
01636 676 898
Tell him Dave in Oldham gave you his number.

zodiac

Have you got a friend that has the same radio that you can borrow the chip from, just to see if that's the problem before you buy one.

zodiac

Yes that's right. If you look at the voltages you have given above there is next to no change between channels 23 and 40 as you have reached it's limit. The PLL runs at 8v so the VCO cannot operate above that, you should see a small increase in the voltage as you change channels from the lowest chan...

zodiac

You'll find TP2 just at the back of the PLL's pin 7, it's R126, 27k.
It's looking like that's all that's wrong with it and the other Eprom that was in was a good one maybe.
With a bit of luck you'll have it working again soon Richard.
Anybody on 40 to give us a rig check PLEASE.

zodiac

Richard,
Did you find the problem yet ?.

zodiac

The codes you have given indicate that things are working as they should right up to the PLL itself and points to the VCO needing slight adjustment as Scott said.
Have you made any adjustment to the VCO ?, even though it had an Eprom in the radio before and shouldn't need adjusting.
Dave.

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