TFW8bit composite mod board

[Lardo Boffin]

I added a resistor going to ground and that definitely improved the picture somewhat!

A nice clear K and no more jailbars.

I used 100 Ohms as a start point. I may need to change it slightly as there is occasional interference on the screen but definitely a step in the right direction.

[Lardo Boffin]

Its FrankenZeddie’s Monster!

It will do while getting it right though.

[Moggy]

Nice one Lardo.

Like I say in my case I used a miniature variable resistor using the centre (sweep) pin and the left pin and altered the resistance till the display was satisfactory, removed the resistor,measured the ohm-age between sweep and left pins then used a fixed resistor of a near enough value.

Looking at how that board is set up near the rest of the modulators gubbins(if still connected) I suspect it may be picking up some interference, and inside a nice grounded empty modulator box the display would be much better.

[Lardo Boffin]

Thanks Moggy. The modulator should all be disconnected - the 5V goes straight to the composite mod board as does the video in. Nothing goes to the modulator.

If I am brave enough to sell one of these with this board then I will most likely empty the whole modulator case anyway. Otherwise it would not look the best even if tidied up.

I assume I need to remove the modulator to empty it?

[1024MAK]

If you are not wanting to keeping the innards in a working condition, it is possible to remove them without desoldering the modulator from the board. However you do it, you do need a powerful iron to do the desoldering. These were not designed to be easy to disassemble

I’m normally too lazy to remove the innards, so just squash the old components down...

Mark

[Lardo Boffin]

Understood! I had troubles replacing the modulator on a C64 so don’t really want to repeat that.

[Moggy]

Oddly enough I find the solder around the two pins holding the modulator fairly easy to remove with a good iron and solder sucker, and then de-solder the video lead and 5 volt lead to the modulator from the board, replacing these with your shiny new boards video and 5 volt leads.

Then I...(SERIOUS COLLECTORS AND THOSE THAT THINK A ZX81 IS A FUTURE PENSION PLAN LOOK AWAY NOW)..get a pair of pliers and rip the innards to bits and throw them in the bin where they belong.

I do tend to hold onto the transistors though because they are handy for when I need to knock up a composite transistor board for an issue 3 ULA zeddie. I mean good God,a transistor a cap a resistor and a couple of bits of wire and some Vero board what could be easier?
Though in fairness this mod only tends to be useful if you have an old CRT TV, the LCD types tend not to play well I've found.

Be brave Lardo shedding a modulator of its workings is nothing to be scared of as they say.

[1024MAK]

I can’t disagree with Moggy. Whether you just attack the existing modulator board from the top (with electricians wire cutters and other suitable tools) or desolder it and attack the existing board from below, is up to you...

The last one where I did it properly, was a ZX80. That got some new electrolytic capacitors on the board and a ZX8-CCB fitted in the modulator. I can’t find the photos I took of it at the moment. But this was work done for a customer.

Mark

[Moggy]

I can’t disagree with Moggy. Whether you just attack the existing modulator board from the top (with electricians wire cutters and other suitable tools) or desolder it and attack the existing board from below, is up to you...

The last one where I did it properly, was a ZX80. That got some new electrolytic capacitors on the board and a ZX8-CCB fitted in the modulator. I can’t find the photos I took of it at the moment. But this was work done for a customer.

Mark

Nice to know we agree on something Mark!

Seriously though I always gut the modulator and to be honest the hardest part I find is removing the metal divider without distorting the Modulator box.

I too have converted my ZX80 this way C/W wiring from the video board to an external jumper for inverse display and fitted a switching regulator!!!

At this point Moggy applies for police protection as gangs of serious collectors try and burn him at the stake for committing sacrilege against a Sinclair classic.

[anightin]

(Please come back to us PokeMon!!!)

Our prayers have been answered

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https://www.sellmyretro.com/offer/details/24241

I've just ordered 2 off.

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