GME tx842 clarifier mod

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davebnz
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GME tx842 clarifier mod

Postby davebnz » Monday 30th Jan 2012, 8:40

hi does anyone have info on how to mod gme 842 or 840 clarifier to work on transmit as well

davebnz
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Re: GME tx842 clarifier mod

Postby davebnz » Sunday 26th Feb 2012, 20:40

Any GME electrophone channel or clarifier mods out there?

lbcomms
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Re: GME tx842 clarifier mod

Postby lbcomms » Sunday 26th Feb 2012, 23:31

There are many variations on this chassis, so instructions like "cut the pink wire and join the green and brown together" usually won't work, and may even kill your radio!

You need to have some basic idea what you are doing (or take it to someone who does).
Only basic gear needed - soldering iron, multimeter, and maybe an exacto knife / scalpel / stanley knife:

Unlocking the clarifier on almost any 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.
- Isolate the track / remove the wire from the "cold" side of the pot. Connect this pot terminal to chassis common (ground).
- Isolate the track / remove the wire from the "hot" side of the pot. Connect this pot terminal to a well regulated source of 8 or 9V, via a 1K resistor.

Presto! Unlocked clarifier.

To reset the "12 o clock" center position, realign the reference oscillator offsets.
These are usually the nearest 3 slugs (for USB, AM, and LSB respectively) to the 10.240 crystal.

If you are not sure which are the "cold" and "hot" pot terminals, they are the outer connections.
If you get them swapped over, the clarifier will work backwards but no damage will happen.

A tech or an experienced tinkerer can do this to almost any SSB radio in 10 minutes flat.
If you don't understand basic instructions like the above, then take the radio to someone who does.

GME electrophone channel mods

Not for newbies or the faint-hearted. It involves constructing external oscillators (including the SSB and clarifier offsets), or replacing the PLL with another programmable one, like the Digiswitch boards we make here.
Even most techs won't touch a job that complex. We can do them here, but its not economical to do so - it can easily cost more than the price of a new radio.

Better to sell it and buy a more easily converted radio, like one of those so called "10 meter" amateur things.

Sue

davebnz
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Re: GME tx842 clarifier mod

Postby davebnz » Monday 27th Feb 2012, 20:19

thanks, that was sort of what i was going to try, the hot side of the pot has 2.8v but the cold side goes into the rf gain pot from memory,
the clarifier mod on my delta force magnum has a 5v regulator and resistor added to feed the clarifier pot, and that was what i was going to try, but i thought i would get some more info before i gave it a go

lbcomms
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Re: GME tx842 clarifier mod

Postby lbcomms » Monday 27th Feb 2012, 22:00

hot side of the pot has 2.8v but the cold side goes into the rf gain pot

Doesn't matter. Isolate these 2 connections and connect the pot terminals to +V and ground respectively.

delta force magnum has a 5v regulator

No need for that. There is a regulator in the 8 or 9 volt range present in nearly every chassis type.
It's usually near the audio output IC. Could be a 3-terminal regulator or a PNP power transistor, both types use a TO-220 case (same package as a "final").

Failing that, take it from the supply pin of the PLL IC.
Google the PLL IC type, that will give you the pinout.
Look for a pin called Vcc or Vdd - that's the supply pin.
This will have a very well regulated 5 to 6 volts on it.

Hope this helps,
Sue

davebnz
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Re: GME tx842 clarifier mod

Postby davebnz » Tuesday 28th Feb 2012, 18:59

the magnum was like that when i got it. thanks for the info, ill give it a go when i get a chance


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