Ducretet Thomson L524

[rockinmark]

Hi I'm asking for a friend because he is not very computer minded would anyone have schematic or anything on Ducretet Thomson L524 I tried some French sites but still no luck

[rockinmark]

Sorry not sure why this got moved as I'm only after information like is the L624 almost the same set or where to find out and I cant find anything

[DMcMahon]

Here is a schematic that I got from radiomuseum. If you do an internet search and look at "Images of Ducretet Thomson L524 schematic" there are several similar schematics and a little other service info.

[rockinmark]

Thanks for that DMcMahon do you know what type of capacitors are in there are french sets the same as British set where you have hunts and wax ones that need changing or do they use different styles. I have told him not to turn it on anymore because he said it starts ok but then goes quite.

[DMcMahon]

No sorry I know nothing about any radio sets. I would guess that due to its age its coupling/de-coupling capacitors may be paper di-electric type.

David

[AC/HL]

Please do not post any radiomuseum schematics. They can be downloaded directly by request if required.

[DMcMahon]

OK understood.

David

[Herald1360]

Originally Posted by rockinmark

Thanks for that DMcMahon do you know what type of capacitors are in there are french sets the same as British set where you have hunts and wax ones that need changing or do they use different styles. I have told him not to turn it on anymore because he said it starts ok but then goes quite.

You will have the same problems with capacitors in French sets as UK or any other country sets.

You may find the extra confusion of capacitance values in "cm" This is a cgs unit for capacitance. 1cm = 1.113pF. For any except precision applications, 1cm = 1pF will be near enough.

[rockinmark]

Thanks for that chris I think he wants to get someone to fix it for him so I might ask on the forum for him I enjoy doing stuff for myself at my own risk of it not working but not somebody's stuff

Thanks everyone

[Herald1360]

There's a non RM originated circuit I uploaded a while back in post #2 here:

https://vintage-radio.net/forum/showthread.php?t=70958

[rockinmark]

What would I replace a 0.25nF axial capacitor with? Would I use a 0.22nF?

[barrymagrec]

Yes.

[DMcMahon]

Yes and of course make sure the replacement voltage rating is at least equal to the original.

[Radio Wrangler]

Before changing anything, what type was the original, and what was it doing?

Changing to 0.22nF == 220pF might make no noticeable difference in audio circuitry, but in the tuned circuits of a radio, it could cause trouble.

David

[rockinmark]

Not sure what they are just trying to get bits together voltages are very high its a French radio

[rockinmark]

I have managed to get this radio, he thought it would cost him too much to get fix so I did a swap. It has a lot of glass type capacitors that are falling apart they have high voltages on them 1500v/2500v. Would they have to be that high or would the yellow axial 650v type do?

Mark

[Herald1360]

Looking at the voltages in the circuit I posted (figures in circles) and considering the low voltage valve lineup, apart from the capacitor from output anode to chassis which could usefully be a 1500V type and the RF filter cap from mains line to chassis which should be a class Y part there's no reason to use anything rated higher than 400V. So 630V would be more than adequate.

[rockinmark]

Looking at the scismstic that Chris posted I can't see why the capacitors are 1500V. I didn't notice until I took the one out I could read. The sheet in post 15 is from a similar radio but are the same types that got for reference.

Mark

[DMcMahon]

Originally Posted by DMcMahon

Yes and of course make sure the replacement voltage rating is at least equal to the original.

This would be a standard/general recommendation.

In this case with the updates that some of the capacitors are rated at high voltages, it may not apply strictly, needs more checking why these particular capacitors are rated that high.

[Station X]

It was nothing unusual for sets to be fitted with capacitors which were too good for the job. ie lower voltage ones would have sufficed.