philips: Replacemnt cords

Hello Radiofriends,
I address this spectacular community asking for help:
I have a Philips radio to restore, model B4CH74A and I have a big problem. Rmorg does not have a diagram of the cord drive. My radio had no wire or pointer, so I couldn't find my way around.
If anyone has the cord replacement diagram, I would be very grateful if you could upload it here on Rmorg. I have the radio ready and it is pending for this reason. I've done several tests, but something always goes wrong. The difficulty lies in the variable capacitors being moved at the same time during channel scanning. and it is curious that the AM/FM exchange is done by switching.
My thanks in advance, from Portugal, Júlio Branco

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Dear Júlio Branco,

With Philips models, it is sometimes helpful to look at similar (or even identical) models from other countries. After a brief search, this Dutch radio B4X72A seemed to me to be comparable, e.g. the back of the chassis looks identical.

There is a comprehensive service manual available, which includes a cord diagram. You can enlarge it by clicking on it.

I hope that it also fits the Swiss model B4CH74A.

Update: The model B5X72A shows the same diagram, but has an additional part. Most probably there are two kinds of stringing cord used, a thicker one (textile) and a thinner one, maybe steel braid.

Please see the attachment.

Best regards
Bernhard Nagel

• Philips B5X72A dial cord diagram (89 KB)

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I've used whipping twine, bead cord, crab line, fishing line and steel guitar wire for various models. So craft shops, music shoprs and fishing tackle shops. Heavy braided steel wire is on bicycle control cables, but I've never needed that. Cotton and polyester threads are no good, but sometimes linen button hole thread is suitable.

Sometimes heavy nylon fishing line works instead of steel wire, but one Philips and one Ever-ready (car-portable) needed single strand wire.

I've also used springs from ball-point pens to tension.

Look at scale and which end is high frequency (AM) and thus the capacitor fully open. FM ia sometimes inverted. Cord thern also needs to wind about 3 times around rust-free drive spindle so that clockwise makes pointer go right. By such observation and a trial you can sketch out how an undocumented cord should work. The gap on a drum on the capacitor should not be quite reached at either end of travel. I've had sets where the drum had been moved. 

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Hello Bernhard and Michael
I begin by thanking you for your prompt assistance.
Note that the B4CH74A only has one pointer that will be used for AM/FM tuning, so the cords will rotate the variable capacitors at the same time. For the first time, in so many cords that I changed, this system never appeared. The AM/FM switching is done by another switch separate from the ones on the keyboard, this one already has a steel wire to operate the AM/FM switch independently of the cord drive system.
This drive scheme that I present is almost similar to the one on my radio, except that it has two more rollers as shown in the figure. An atypical cord drive system.
Any help you can give me I appreciate.
Julio Branco

/forumdata/users/3656/drive_cords.pdf
 

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Hello friends Bernard and Michel
First of all, I want to thank you for all the effort you have put into helping me restore my B4CH74a radio.
In my case, my radio only has one pointer and only one drag mechanism to activate the AM/FM variable capacitors.
OK, after many tests and many meters of damaged cords, I finally managed to finish the job, and the entire drag mechanism is working perfectly.

I will attach here some photos of how I managed to assemble the cords in the respective drag mechanism to give some clues to other radio friends who may need to replace them, because, as I said before, it is an atypical drag system, even the drag axis is not aligned with the drums fixed to the AM/FM variable capacitors. The difficulty was compounded by
A big thank you
Julio

See attachments

/forumdata/users/3656/Imagem_WhatsApp_2025_06_11_as_21_53_05_54e5f3ab.jpg

/forumdata/users/3656/Imagem_WhatsApp_2025_06_11_as_21_53_06_dd99dd36.jpg

/forumdata/users/3656/Imagem_WhatsApp_2025_06_11_as_21_53_06_f87cd608.jpg

/forumdata/users/3656/Imagem_WhatsApp_2025_06_11_as_21_57_58_6422a268.jpg

/forumdata/users/3656/Imagem_WhatsApp_2025_06_11_as_21_57_58_f7654b27.jpg

PS.: If Rmorg authorized it, it would be much less work for us to upload a short video, it would be more enlightening

To thank the Author because you find the post helpful or well done.

Hello friends Bernard and Michel
First of all, I want to thank you for all the effort you put into helping me restore my B4CH74a radio.

In my case, my radio only has one pointer and only one drag mechanism to activate the AM/FM variable capacitors.
OK, after many tests and many meters of damaged strings, I finally managed to finish the job, and the entire drag mechanism works perfectly.

I will attach here some photos of how I managed to mount the strings on the respective drag mechanism to give some clues to other radio friends who may need to replace them, because, as I said before, it is an atypical drag system, even the drag axis is not aligned with the drums fixed to the AM/FM variable capacitors. The difficulty was compounded by.

A big thank you
Julio

See attachments

PS.: If Rmorg authorized it, it would be much less work for us to upload a short video, it would be more enlightening

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Hello

Although you already managed the problem.....

Here what the original Servicedokumentation says:

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Actually good sketches, text and a a couple of photo are far better than a video for something like this.

And on web page, not a PDF. Accessibility is poor on PDFs. Really they should now only be used for paper.

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Thank you very much, Mr. Walter.

Maybe it wouldn't be a bad idea to upload this image to the technical information sheet for this radio, I think.

Julio

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