PTBM121D4X (Cybernet SSB) chassis - adding a 5KHz drop

[lbcomms]

By request: PTBM121D4X (Cybernet SSB) chassis - adding a 5KHz dropper switch

Before doing this, check the PLL chip type. These radios used one of 5 different types.

If it has the NPC PLL, PLL02, or the PLL02A, then the modification will not work.
If it has the PLL02AG or a MC145109, it can be rewired for 5K steps as below.

Caution #1 - this will only work on radios with SSB. AM only and AM/FM only radios need a lot more work to do this on.

Caution #2 - this is written with experienced people in mind and a lot of simple simon info (such as the correct type of soldering iron and wire) is left out (assumed knowledge). If you are not comfortable inside a radio and with modifying digital electronic circuits, then find a good tech to do the mod for you.

Step by step:

a) Connect pin 4 of the PLL chip to ground (same trace as pin 16).

b) Isolate pin 7 from ground (you'll need to cut the trace in two places, one either side of the pins solder joint).

c) Join the now isolated pin 7 to pin 8 (a blob of solder will do it). This is the 5 volt rail of the PLL (zero ohms to pin 1).

d) On the other row of PLL chip pins (i.e. towards the front of the radio) cut the traces to pins 9, 10, 11, 12, 13, 14, and 15.

e) Connect the trace that used to go to pin 15 to pin 14 of the PLL.

f) Connect the trace that used to go to pin 14 to pin 13 of the PLL.

g) Connect the trace that used to go to pin 13 to pin 12 of the PLL.

h) Connect the trace that used to go to pin 12 to pin 11 of the PLL.

i) Connect the trace that used to go to pin 11 to pin 10 of the PLL.

j) Connect the trace that used to go to pin 10 to pin 9 of the PLL.

This leaves pin 15 connected to nothing.

k) Follow the trace from pin 5, it will go to a 0.1uF capacitor and a 3.3K resistor. Change the resistor to either 5.1K or 5.6K.

At this stage, turn the radio on. The channels and modes should be as they were before. Make sure the SSB audio hasn't gotten any worse (if it has, recheck step "k").

l) Isolate an unused switch, such as NB or CB/PA.

m) Connect one side of the switch to pin 15, and the other to the blob or link created in step "c".

With the switch OFF you will have the "fives", and with the switch ON you will have the "zeroes".
For example, mid channel 40 (27.405) will drop exactly 5KHz to 27.400 when you turn the new switch on.

That's all...

[jocarl011]

Thanks for that info, I'm going to get on with that tomorrow if I have a spare 5.1/5.6k resistor kicking around.

Just aligned my Lafayette 1200FM and completed all the audio mods so she's sounding perfect now and bang on frequency too! I also opened up the clarifier so just this mod to do and it's complete.

Carl.

[163TM847]

Damn both my Natos have NPC O2A's and the spare O2A's i have none are 02AG Not to worry info is noted and will give it a try next time a PTBM121/059 comes along as they normally used the O2AG.

What about a Cybernet radio thats using an MC145106 ? I sometimes use an MC145106 if i dont have an O2A spare.

[lbcomms]

Isn't the MC145106 an 18 pin device (the extra 2 pins being an on-chip reference oscillator and a 5.12MHz output)?

That's not going to fit in a Cybernet without a lot of work, such as a small adapter board.

BUT: if you do make an adapter, it will work, but the pin numbers will be different from my original post...

[jocarl011]

Edited this as I had no audio on the zeros at first but all sorted now, the mod works perfectly!

[jocarl011]

I wired to the CB/PA switch but didn't disconnect the ground wires from the switch so received fine on the zeros but transmitted no carrier! All sorted now and everything is fine.

Is it normal to have to adjust SSB mic gain after the mod? Mine needs turning down a little. Perhaps due to changing the 3.3k resistor to 5.6k?

Thanks Carl.

[lbcomms]

Good to see it worked for you. That mod has nothing to do with the mic gain, the resistor is part of a low pass filter for the PLL (if you halve the step size the resistor has to be increased by 50%, all other things being equal). The VCO frequencies are the same before and after the mod if pin 15 is open, so the audio and RF levels can't be affected.

You might have disturbed something else, or you may have a cap on the way out. If adjusting the mic gain got the levels where you want them it's only an academic point - leave well alone...

[jocarl011]

yeah I adjusted the mic gain and all is fine now, your probably right I may have caught something...

Thanks for the mod and the other help you gave last week.

Carl.

[163TM847]

This mod works fine with a Cybernet using an MC145106, Thanks

[lbcomms]

Thanks for testing it, until yesterday the MC145106 PLL version only existed on paper.

Now we know 100% it works, here it is in public for the benefit of anyone else that wants to do it.
Almost identical, except for the changed pin numbers.

MC145106 PLL in a Cybernet SSB - adding a 5 KHz drop

a) Connect pin 6 of the PLL chip to ground (same trace as pin 18).

b) Isolate the pad that pin 9 connects to (2 trace cuts may be needed)

c) Join the now isolated pin 9 to pin 10 directly opposite with a short wire link. Check this link also goes to the 5 volt rail of the PLL (zero ohms to pin 1).

d) Cut the traces to pins 11, 12, 13, 14, 15, 16, and 17.

e) Connect the trace that used to go to pin 12 to pin 11 of the PLL.

f) Connect the trace that used to go to pin 13 to pin 12 of the PLL.

g) Connect the trace that used to go to pin 14 to pin 13 of the PLL.

h) Connect the trace that used to go to pin 15 to pin 14 of the PLL.

i) Connect the trace that used to go to pin 16 to pin 15 of the PLL.

j) Connect the trace that used to go to pin 17 to pin 16 of the PLL.

This leaves pin 17 connected to nothing.

k) Follow the trace from pin 7, it will go to a 0.1uF capacitor and a 3.3K resistor. Change the resistor to either 5.1K or 5.6K.

At this stage, turn the radio on. The channels and modes should be as they were before. Make sure the SSB audio hasn't gotten any worse (if it has, recheck step "k").

l) Isolate an unused switch, such as NB or CB/PA.

m) Connect one side of the switch to pin 17, and the other to the link installed in step "c".

With the switch OFF you will have the "fives", and with the switch ON you will have the "zeroes".
For example, mid channel 40 (27.405) will drop exactly 5KHz to 27.400 when you turn the new switch on.

Enjoy...

[163TM847]

Just too add, I recently modified a Stag 357 from an LC7120 to an MC145106 and had a PIC coded so i could use the original LC7120 selector [6 line in 8 line out] and PIC does Lo.Lo, Low, Mid, High, +10kc [And can do UK40]

Well, I also did the zero mod to the PLL on it and it works great

I want to try it too a WKS 1001 but im not sure it would work as some of the PLL pins are used for band switching ?

Edit: It does work in the WKS1001/Colonol FR360 which is handy as it puts the 10m [28.365 - 28.805] onto 28.370 - 28.810 unfortunately because of the channel positioning it wont get 28.500.

But hey it gets zeros

[lbcomms]

We did an Intek 120 (same as the WKS1001/Colonol FR360) as a proof of concept a couple of years ago. Replaced the channel selector with a rotary encoder switch and replaced the PLL with a serial one. A new display board was made on perfboard as it was only a one-off for a good customer. Control was done with one of those ultra cheap "nano" AVR ATMega328 boards from eBay.

Used the A/B/C switch to select 1K, 5K, or 10K steps. The radio covered from memory about 26.3 to 28.8 before the VCO and RF stages started to fall off. Didn't bother with UK40 as a separate band, no FM and it's not a lot of use down here

Might have some pics and a hand drawn circuit around somewhere if you are interested.

PS: Can you guys now use SSB and AM on the 27/81 frequencies now, or are they still FM only?

[163TM847]

27/81 is and more than likely always will be FM only, Not much point in SSB on 27.60125 to 27.99125

[14CS06]

Hello

Please look at this link for Alpha channels

http://ham-international.nuxit.net/PLL02.htm

http://ham-international.nuxit.net/HomeEng.htm

@+
Claude

[Juremm]

Hi,

I was wondering what is freq. range of the radio with that mod?


Cheers
Jure