Unlocking clarifier President George

[zodiac]

I'm looking for good detailed information no how to unlock the clarifier on the President George.
I found one site but it doesn’t make any sense and the drawings don't match the radio I have.
I can't get it in to my head as to why it uses the mike gain control when it's got a clarifier control and there is no J408 that it mentions marked on the board anywhere.
I know it's possible to do it and I thought I'd seen it on this forum years ago but can't find it even if I do a search.
The big problem with the George is, all the surface mounts on the track side of the board without any screen print to identify the components, plus it doesn't make it any easier not having the schematic.
Dave.

[lbcomms]

There are probably different chassis that use the same name - I've seen lots of different radios called "Cobra 148"...

Unlock is the same as almost any other SSB chassis.
- Follow centre pot wire to PCB. It will go to the unmarked end of a diode.
- The other (marked) end of that diode will go to the marked end of another identical diode. Cut it.
- Remove the two outer wires from the pot. Leave the centre wire in place.
- Connect the "cold" side of the pot to chassis common (ground).
- Connect the "hot" side of the pot to a well regulated source of 9V, via a 1K resistor.

Presto! Unlocked clarifier.

Notes:
The 1K resistor is not essential but recommended for safety, especially if you are not 100% sure of what you are doing.

The "cold" and "hot" are the two outside connections on the pot you removed the wires from.
If you get them reversed no harm will be done, but the clarifier will work in reverse.

The red wire is the hot side, the black is on the cold side.
The blue is the centre one that you leave on.

Occasionally you'll have to add resistors (to reduce slide range) or inductors (to increase slide range).
Worry about these 2 issues only when you have to - in 95% of cases, it will work straight away.

Some sets solder the pot directly into the board, no wires.
This then involves cutting tracks and using a multimeter to make sure you've done it completely and correctly.
If you don't have or can't use a multimeter, take the radio to somebody that knows what they are doing.

Enjoy

[zodiac]

Thanks for the reply but this is not an old fashioned radio that will last for years and stand the hammering they get from normal use.
This is a micro controller type radio with flimsy boards and bits of plastic holding the front together with surface mount components on the track side of the main PCB, making it virtually impossible to do any repairs on it apart from the outputs.
If you haven't seen one then think yourself a very lucky guy, the board number is PB-229AE.
I have now taken it apart to investigate and can see why the clarifier hasn't been used for the conversion, the rotary control is soldered direct to the front board with surface mounted components on the traces right up to the solder points for the control, with a through hole trace going to the other side of the board I can't get at to trace for other things in the way, so that solves the misty of the mike gain being used instead of the clarifier as normally would be.
The Mike / RF gain is mounted on the front metal panel as normal, the wires go to J408 and the mike socket board close to the front of the board, not as instructed in the centre, that's why I couldn’t find it.
If I can sort this out I'll have to re write the destructions and do better drawings, cause that's what they look like at present.
Dave.

[lbcomms]

I went looking for info on these (no I haven't seen one yet here on Oz) and found three variants of it.
Therefore, your instructions are for a different version to yours

the rotary control is soldered direct to the front board with surface mounted components on the traces right up to the solder points

OK, that makes it a bit easier... no need to cut tracks or worry about damaging the inners of PCB holes when removing components.

What I said before holds true then. You'll need a surface mount (hot air) rework station preferably, but you are only doing resistors, so a PAIR of soldering irons with small tips should do it. Alternately, carefully cut the tracks where they enter the outer clarifier terminals (cpu board) and diode (near the PLL).

First of all, near the the PLL (main board):

Isolate the diode circled in red.

Next, the clarifier pot(cpu board):

Either remove the resistors circled in red, or cut the tracks that go between the resistor and the clarifier pot.

Connect the side of the pot marked in BLUE to a regulated DC voltage (there will be a regulator in the set somewhere that will give you 8 or 9 volts).
Connect the side of the pot marked in GREEN to a PCB ground.

Lastly, enjoy your slider
As I said in my original reply, you might have to limit or boost the range if has too little /too much slide.

If you know basic electronics and have the right tools, this shouldn't take any more than about 10 to 15 minutes.

Doing it this way is a MUCH better alternative to cryptic instructions like "run a pink wire from Pin 7 of P123 to pin 4 of IC6".
If the authors version of the radio is different to yours, you might be doing something like putting 13V onto the chipselect line of the micro (in laymans terms, destroying a perfectly good radio).

Have fun,
Sue

[zodiac]

Sue,
That's exactly what I needed, the schematic or the part that shows the parts I need to see.
As you say much easier to do than the explanation below.


1. Disconnect the wire in the middle of the connector J408 on the principal plate (Mother board).

2. Take off (remove) the adjustable VR211 (TX-frequency adjust).

3. Connect the wire you took off (J408) and solder it at the place middle point of the adjustable VR211 (Diode side D215).

4. Cut the middle of the wire linking the modulation between MIC CONNECTION plate and MIC GAIN plate, position 2 on both connectors (near the orange wire).

5. For the part of the wire connected to the MIC CONNECTION plate; solder the other side onto J408 on the principal plate.

6. For the part of the wire connected to the MIC GAIN plate; solder the other part on VR211 strap side (The other part is on the ground)

7. Replace R408 1kohm by an 500 ohm adjustable potentiometer
Solder the two contacts of the potentiometer MIC GAIN.

8. Set MIC GAIN in middle, and adjust R408 500 ohm potentiometer to get 27.205 MHz.

9. You can now use MIC GAIN for adjusting the centre frequency.

Thanks again Sue.
Dave.

[zodiac]

Sue,
That diagram has things the wrong way round, I wired it that way and it worked the opposite way, the 33k resistor side of the control I have now got at +V.
I used 5v with a 33k in line and a 1k on the other 0v side to keep the amount of shift to a minimum.
This radio has a zero switching (down 5KC) function as standard, all I needed was to be able to move a couple of KC's to be able to get onto the UK frequency of 1.25 instead of 5 on the fifth digits.
Other than that you are spot on again.
Thanks Dave.

[lbcomms]

That diagram has things the wrong way round

It's not uncommon to find things like that - I always "tack" things in place and check first before making a nice neat permanant finish. It's much more of an issue with consumer gear like CB and ham radio stuff than it is with the pro gear, where revision levels are generally shown on both the drawings and the product.

all I needed was to be able to move a couple of KC's

The "big" freeband rig of pirate choice of the 80's and 90's here in Oz was the Cobra 148. At least half of the people we modified them for wanted to slide at least 15 to 20KC, even when we pointed out to them that 10KC would take them over to the next channel

Good to see you got it done OK.
Cheers