Philips MW tuning - UK Vintage Radio Repair and Restoration Discussion Forum

Paul Mathew · 14th Sep 2020, 5:53 am

I have a B3X08, which has a close enough schematic to the B3X02: http://www.philipsradios.nl/Schemas/B3X02A.pdf
After a mains and, a few other dodgy cap replacements, the radio works well on both MW & FM.
I'm just not picking up a station near the lower end of the AM waveband (567kHz), even when the main tuning caps are fully meshed.
I was wondering whether trimming the local oscillator or main tuning padders, would be the way to go, in shifting the reception?
The trimmer caps, all appear to be the beehive type, with a healthy glob of paint on the adjusting nut, so I'm reluctant to start fiddling with that!

peter_scott · 14th Sep 2020, 8:38 am

Hi Paul,

The trimmers are to adjust the other end of the scale. The oscillator coil is the adjustment for the 576kHz end. If that doesn't bring it in range then your IFs might be tuned to the wrong frequency.

Peter

Andrew2 · 14th Sep 2020, 9:15 am

This is why some kind of calibrated sig gen is so valuable. You could set the radio to the bottom end of its coverage and manually sweep the gen upwards until you hear a signal. This would tell you how far the LO needed adjusting with the MW osc coil.

Paul Mathew · 14th Sep 2020, 9:52 am

Thanks for the input. I'll be taking the radio to a friend with all the equipment to run the tests you've suggested.

boxdoctor · 14th Sep 2020, 3:34 pm

Have you checked for short-circuits on the tuning capacitor vanes when nearly fully enmeshed?
Just a thought. Tony.

14th Sep 2020, 5:53 am	#1
Paul Mathew Pentode Join Date: Jan 2014 Location: Cape Town, South Africa Posts: 214	Philips MW tuning I have a B3X08, which has a close enough schematic to the B3X02: http://www.philipsradios.nl/Schemas/B3X02A.pdf After a mains and, a few other dodgy cap replacements, the radio works well on both MW & FM. I'm just not picking up a station near the lower end of the AM waveband (567kHz), even when the main tuning caps are fully meshed. I was wondering whether trimming the local oscillator or main tuning padders, would be the way to go, in shifting the reception? The trimmer caps, all appear to be the beehive type, with a healthy glob of paint on the adjusting nut, so I'm reluctant to start fiddling with that!

14th Sep 2020, 8:38 am	#2
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: Philips MW tuning Hi Paul, The trimmers are to adjust the other end of the scale. The oscillator coil is the adjustment for the 576kHz end. If that doesn't bring it in range then your IFs might be tuned to the wrong frequency. Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

14th Sep 2020, 9:15 am	#3
Andrew2 Nonode Join Date: Mar 2010 Location: Dukinfield, Cheshire, UK. Posts: 2,037	Re: Philips MW tuning This is why some kind of calibrated sig gen is so valuable. You could set the radio to the bottom end of its coverage and manually sweep the gen upwards until you hear a signal. This would tell you how far the LO needed adjusting with the MW osc coil. __________________ Andy G1HBE.

14th Sep 2020, 9:52 am	#4
Paul Mathew Pentode Join Date: Jan 2014 Location: Cape Town, South Africa Posts: 214	Re: Philips MW tuning Thanks for the input. I'll be taking the radio to a friend with all the equipment to run the tests you've suggested.

14th Sep 2020, 3:34 pm	#5
boxdoctor Rest in Peace Join Date: Sep 2010 Location: Ripley, Derbyshire, UK. Posts: 785	Re: Philips MW tuning Have you checked for short-circuits on the tuning capacitor vanes when nearly fully enmeshed? Just a thought. Tony.