06-01-2020, 04:39 PM
I'm working on a 1980s solid state 12" video monitor. All pretty conventional stuff. But the LOPT sometimes shrieks at half linescan frequency. I've measured it by beating against an audio oscillator. It's a horrible noise. Goes away if I prod the LOPT. May well go away altogether if I tighten the mounting bolts to clamp the core a bit better.
But why HALF frequency? I know magnetostriction noises can happen on harmonics of the frequency, but subharmonics?
I'm looking at this monitor with a view to converting it to 405. Has reasonable prospects but I hope the LOPT isn't too loud. If I succeed I will replace the Prowest PM14/1 at the Vintage Wireless Museum which always seems to give trouble. Since I may have more than 1 of these monitors my own PM14/1, lovely pictures but not the most reliable, may well also be retired.
But why HALF frequency? I know magnetostriction noises can happen on harmonics of the frequency, but subharmonics?
I'm looking at this monitor with a view to converting it to 405. Has reasonable prospects but I hope the LOPT isn't too loud. If I succeed I will replace the Prowest PM14/1 at the Vintage Wireless Museum which always seems to give trouble. Since I may have more than 1 of these monitors my own PM14/1, lovely pictures but not the most reliable, may well also be retired.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
