UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 6-gang FM stereo tuner heads

Radio Wrangler · 25th Nov 2022, 5:02 am

OK, in the 3324A the 30MHz PLL is the frequency standard/heterodyne mixdown LO

30MHz loop unlocked could simply mean that the external 10 MHz frequency reference has been selected and you haven't connected a 10MHz standard to the unit. If so, the fault should clear if you switch to internal reference.

It also looks like the frac-N loop does self tests at 30MHz and 60MHz frequencies. One of these could fail due to drift in the frac-N loop VCO. Might be a simple tweak to fix, otherwise these frac-N systems scare people off and are full of special and selected parts. The make of one logic gate has around a 20dB influence on spur levels!

David

25th Nov 2022, 5:02 am	#266
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,900	Re: 6-gang FM stereo tuner heads OK, in the 3324A the 30MHz PLL is the frequency standard/heterodyne mixdown LO 30MHz loop unlocked could simply mean that the external 10 MHz frequency reference has been selected and you haven't connected a 10MHz standard to the unit. If so, the fault should clear if you switch to internal reference. It also looks like the frac-N loop does self tests at 30MHz and 60MHz frequencies. One of these could fail due to drift in the frac-N loop VCO. Might be a simple tweak to fix, otherwise these frac-N systems scare people off and are full of special and selected parts. The make of one logic gate has around a 20dB influence on spur levels! David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done