President Grant - Clarifier Shift

[Animal]

Radio Make and Model: President Grant (Black Front)
PCB Number: PC999AE
PLL Number:

Test gear available: Stand Alone Counter, Digital VOM

Symptoms: Coarse clarifier control doesn't shift 5kc either side.

What is working: Everything else works fine.

What has been tried: Nothing (I'm just a keen hobbyist!)

Did it suddenly happen ?: Just got it so I don't know it's history.

Anything else that may be of help?:

Any help would be much appreciated.

[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's the best thing you can do to a Cybernet.
Then you'll have to realign it all.

Dave.

[Animal]

Cheers Dave,

Scrap Cobra 148's - perish the thought!!!

I've got a RD16HHF1 MOFET (sealed in anti-static package) if you want to do a swap for some varactor diodes?

Steve

[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.

[Animal]

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's the best thing you can do to a Cybernet.
Then you'll have to realign it all.

Dave.

Dave, Which are the ITT410's in the Concorde II???

Cheers

Steve

[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.

[Animal]

Dave,

On the Xtal board of the Concorde 2, D1 & D4 look totally different to each other?

Steve

[zodiac]

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

[Animal]

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

That's me on the naughty step (again!)

Okay, swapped D1 from the Xtal board on the Concorde into the Grant (D44 position) & it's just the same (all three bands)

I know that one diode is used for two of the bands but I thought I might have seem some change?

Steve

[zodiac]

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

[Animal]

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

I didn't realize it needed unlocking tbh Dave

How do I do that exactly (I have my claw-hammer & oxy-acetylene torch at the ready!)

Cheers

Steve

[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 the also empty holes for R120, located at the front edge of the board next to the coils and crystals.
Fit a 1/4 watt 470 ohm resistor in at the empty holes for R120.
Solder the grey wire to the 8v rail leading from TR39's collector, there are two unused holes on the board that come from TR39 to the front of the board.
Replace D79 with a link wire and remove D45.
Does it work now Steve ?.

Dave.

[Animal]

It's the black front version Dave (with both coarse & fine) but the coarse only moves 2kc either way.

[zodiac]

Erruummm, well that's all i did with the black ones, just fit the diodes and tune up.
Did you look at the diode before you fitted it, it should have ITT310 or 410 on them.
The reason I say that is because a IN4148 diode will work as a varactor but it won't shift as much and it sounds like that's what you've fitted.

[zodiac]

Steve,
Have you sorted it yet ?.

[Animal]

No Dave,

Checked the voltages & all seemed to be in order.

I've ordered some of those large cap varicap diodes (25-500pF) & will let you know how I get on.

Steve