RF Modulator Problems

Discussions about Sinclair ZX80 and ZX81 Hardware
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RF Modulator Problems

Post by dmemphis » Thu Mar 22, 2018 2:28 am

So what's the skinny on the RF modulators?
My ZX80 original has the UM1082 and it doesn't work.
I have a good video signal going in and power, but
it doesn't output anything to channel 2.
I had good output for an instant once while touching
around the coil- where it is split in 2. Is that area really touchy?
Are there typical failure modes? Might it just need
solder touch up on the bottom?

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Re: RF Modulator Problems

Post by 1024MAK » Thu Mar 22, 2018 3:50 pm

With TVs having composite video inputs these days, not many users worry about using modulators anymore.

To get access to the solder side of the PCB that is inside the modulator is a lot of work, and attempting to remove it may be destructive. So you may be better off seeing if anyone has a modulator they are willing to sell to you.

One possible problem with yours may simply be that it has drifted off tune from the intended TV channel. If you put your hand near the components, the extra stray capacitance will change the frequency of the RF oscillator.

Try tuning your TV through the range of channels.


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