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Posted By

Retroshire
on 2021-07-07
05:56:08

Finetuning trimmers Plus/4

I just replaced a frequency crystal NTSC to PAL. Is there anything to say about adjusting the fequency trimmer next to it? I don't see a lot difference when turning the screw.

The same thing about the trimmers in the modulator, what is the function of the different trimmers? Is it effecting the composite output or only the RF output?

I cannot find a screenutility or something for this.

Posted By

TLC
on 2021-07-07
14:45:59

Re: Finetuning trimmers Plus/4

Frequency tolerances for both PAL and NTSC are pretty tight (at least what the standards specify). In the Plus/4, every clock frequencies, including the color subcarrier, are derived from this single oscillator here. The trimmer there is for fine tuning this oscillator's frequency. With typical machines and TVs, by turning the trimmer, you'd notice the color to disappear and re-appear. The trimmer should be tuned to match standard frequency (---> the color subcarrier, as divided by the TED from this oscillator's frequency, should match that of defined PAL / NTSC subcarrier frequency within tolerances). In practice, as an amateur, one'd set that using a standard PAL/NTSC color display, by letting the machine warm up first, then finding points where the color appears / disappears by carefully turning the trimmer around - and finally setting the trimmer to the mid-position in the "color" area between the discovered points. (With a display seemingly immune to NTSC subcarrier variances, this unfortunately won't be possible.)

I don't know much about the RF modulator, unfortunately.

Posted By

Hifi
on 2021-07-07
10:45:58

Re: Finetuning trimmers Plus/4

Helló,helló ÚJRA ITT vagyok....... Az RF modul (OKOS modul....YEAH!) tudja a dolgát! A DIRECT kimeneteleknél (LUM,COLOR,COMP...) CSAK kimeneti ILLESZTŐ feladata van! Az RF kimeneten a TV vagy MONITOR LEGYEN PAL (ill. NTSC) COLOR feldolgozásra alkalmas (ill. UHF frekvenciára.... a TV!) !!! ENNYI! Üdv.: HiFiofTLT

Re: Finetuning trimmers Plus/4

Hello, hello, I'm HERE AGAIN ....... The RF module (SMART module .... YEAH!) knows its stuff! For DIRECT outputs (LUM, COLOR, COMP ...) it has ONLY an output adjuster function! The RF or MONITOR on the RF output must be capable of PAL (or NTSC) COLOR processing (or UHF frequency.. the TV!) !!! THAT'S IT! Greetings: HiFi of TLT

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