NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)

EFIALTISFM · Post by **EFIALTISFM** » Wed Mar 23, 2022 7:59 pm

Hi guys,

Anyone seen this problem before or any ideas what it might be?

All coils made as per build instructions (also found here-> search.php?keywords=pro4&fid%5B0%5D=11)

Played around with coil spacing.
Even changed L2 coil a few times (using thicker and thinner wire and changing the default turns to 5 and 7 turns) but no major changes...

Still won't lock 88-100Mhz ... Any ideas?

Thanks

Albert H · Post by **Albert H** » Thu Mar 24, 2022 2:28 am

The clue might be that the problem only exists below 100MHz..... Check your soldering around the big 4059 IC and the switches. It's also worth checking the outputs from the switches - all four switches will have the output sequence as they're rotated.... You might have a faulty BCD switch, or a dud 4059, or (more likely) you've got a dodgy soldered joint.....

EFIALTISFM · Post by **EFIALTISFM** » Sun Mar 27, 2022 9:43 pm

Hey Albert,

Thanks for your assistance.

BCD switches, tested individual rotation and compared sequence/output. All 4 same = OK.
Soldering joints, from IC socket to BCD pins, OK, General board joint inspection, OK
2.2k Network resistor, OK

Next to be tested, the 4059.

One question though, the current chip is a HC 4059 so could I replace it with a CD (being older logic tech that can't toggle as fast as 74HC) or is it best to be a HC?

Ta

Albert H · Post by **Albert H** » Mon Mar 28, 2022 2:37 am

It MUST be the HC or HCT version because it needs the speed!

LeeCavanagh · Post by **LeeCavanagh** » Wed Apr 20, 2022 12:01 pm

On occasions the small coils need opening or closing a bit to cover all freq, bur last resort.

Shedbuilt · Post by **Shedbuilt** » Wed Apr 20, 2022 12:17 pm

Where is the variable capacitor (VC1), when you're at or just above 100MHz ?
If VC1 has to be fully closed, to lock on the lowest frequency you can achieve, then maybe you need to close the L1 inductors (the L1 coils form the primary oscillator inductance, not L2), or there may be an issue with one or more of the other circuit values in the oscillator (capacitor missing or too low value). If it will lock at, or just above 100MHz, and doesn't jump out of lock, as you reduce the value of VC1 (and will come into lock with VC1 at less than its maximum value), then it's most likely a problem with the PLL / control circuitry.

Shedbuilt · Post by **Shedbuilt** » Wed Apr 20, 2022 1:59 pm

Also; probably stating the obvious, if the issue only happens at under 100Mhz, and is ok from exactly 100MHz upwards, it'll almost certainly be with the switch, pull down resistor, circuitry around those, the chip itself, or something very much in that area.

NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)

NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)

Re: NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)

Re: NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)

Re: NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)

Re: NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)

Re: NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)

Re: NRG PLL PRO 4 - Will ONLY lock between 101-108 (will NOT lock 88-100)