Ducretet Thomson L524 - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

rockinmark · 16th Jun 2020, 10:20 am

Sorry Chris I did notice your last post can I replace c23= 40nf with 0.047uF 1000V Polypropylene Axial Capacitor I cant find what to replace c24 = 10nf with you say y class and what voltage for this one. Found this one 250vac
Thanks mark

Herald1360 · 16th Jun 2020, 11:57 am

The cap pictured is the correct spec but is one of the notorious Rifa stink bombs

Unless it's brand new (in which case it'll probably be OK for ten years or so). I'd go for something like this:

https://uk.farnell.com/epcos/b32022a...22?ost=1609522

C23- 40nF seems excessively large. 4nF would be more reasonable. Is the actual capacitor really 40nF? I'd probably try something like 2.2nF.

rockinmark · 16th Jun 2020, 12:53 pm

Thanks for that Chris i will get that one I as for c23 is so bad it hasn't got any markings on it but i was going by the schematic

rockinmark · 16th Jun 2020, 2:18 pm

Presumably 630v will be OK for that

rockinmark · 16th Jun 2020, 2:53 pm

Here is picture of l524 and l624 everything seEms the same but that one capacitor and I don't know why its 40nf unless it's a mistake.

Herald1360 · 16th Jun 2020, 9:11 pm

I'd stay with 1000V for the C23.

Value wise, even the 624 has 10nF which still seems rather high. A quick simulate suggests that 40nF will have the treble response down by 3dB at 1kHz. That's going to sound very woolly. 10nF moves the -3dB point out to 4kHz which is still going to cut what little treble there is in an AM signal somewhat. Admittedly '40s / '50s tastes did run to "mellow" sound but like the DAC90A I suspect some more brightness would suit nowadays. I'll stick with my 4.7nF suggestion. You could just add another in parallel if it sounds too bright!

16th Jun 2020, 10:20 am	#21
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Ducretet Thomson L524 Sorry Chris I did notice your last post can I replace c23= 40nf with 0.047uF 1000V Polypropylene Axial Capacitor I cant find what to replace c24 = 10nf with you say y class and what voltage for this one. Found this one 250vac Thanks mark Attached Thumbnails Last edited by rockinmark; 16th Jun 2020 at 10:43 am.

16th Jun 2020, 11:57 am	#22
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Ducretet Thomson L524 The cap pictured is the correct spec but is one of the notorious Rifa stink bombs Unless it's brand new (in which case it'll probably be OK for ten years or so). I'd go for something like this: https://uk.farnell.com/epcos/b32022a...22?ost=1609522 C23- 40nF seems excessively large. 4nF would be more reasonable. Is the actual capacitor really 40nF? I'd probably try something like 2.2nF. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

16th Jun 2020, 12:53 pm	#23
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Ducretet Thomson L524 Thanks for that Chris i will get that one I as for c23 is so bad it hasn't got any markings on it but i was going by the schematic

16th Jun 2020, 2:18 pm	#24
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Ducretet Thomson L524 Presumably 630v will be OK for that

16th Jun 2020, 2:53 pm	#25
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Ducretet Thomson L524 Here is picture of l524 and l624 everything seEms the same but that one capacitor and I don't know why its 40nf unless it's a mistake. Attached Thumbnails

16th Jun 2020, 9:11 pm	#26
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Ducretet Thomson L524 I'd stay with 1000V for the C23. Value wise, even the 624 has 10nF which still seems rather high. A quick simulate suggests that 40nF will have the treble response down by 3dB at 1kHz. That's going to sound very woolly. 10nF moves the -3dB point out to 4kHz which is still going to cut what little treble there is in an AM signal somewhat. Admittedly '40s / '50s tastes did run to "mellow" sound but like the DAC90A I suspect some more brightness would suit nowadays. I'll stick with my 4.7nF suggestion. You could just add another in parallel if it sounds too bright! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O