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142 Gtl pll issue
- Thread starter kaos513
- Start date
Should be the MB8719, do you have the pin info for this pll? If not, I can send you what I have.
edit: Also, make sure the reference 10.240 is reaching and you have something (1.43-1.87MhZ) coming from the vco downmix for the phase detector input. If those are okay, check the truth chart and compare that to the channel you are displaying, and the program pins voltage (high/low). See where that gets you.
edit: Also, make sure the reference 10.240 is reaching and you have something (1.43-1.87MhZ) coming from the vco downmix for the phase detector input. If those are okay, check the truth chart and compare that to the channel you are displaying, and the program pins voltage (high/low). See where that gets you.
Most common fault we see to cause this is for L18 to be adjusted wrong. Put the 'scope probe on pin 17 of the 8719 chip, peak L18 for highest input level to the chip. And if the slug appears to peak with the slug DEAD EVEN with the rim of the hole, that deserves mention. Tells you there's a fault with L18, and adjusting it isn't doing the whole job by itself.
And if you have turned the slug in L13, trying to get the VCO tuning voltage right, putting the 'scope on TP9 makes it easier to see when L13 is set close. If it's locked, you'll see the tuning voltage step up or down ever so slightly with each click of the channel selector.
73
And if you have turned the slug in L13, trying to get the VCO tuning voltage right, putting the 'scope on TP9 makes it easier to see when L13 is set close. If it's locked, you'll see the tuning voltage step up or down ever so slightly with each click of the channel selector.
73
