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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 6th Feb 2018, 2:06 pm   #21
emeritus
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Default Re: Philips D8334/05R - Toothless gears

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Old 6th Feb 2018, 8:55 pm   #22
SiriusHardware
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Default Re: Philips D8334/05R - Toothless gears

Hopefully that will be your problem sorted, Emeritus.

I took one of the decks on the Philips 8334 further apart today - it was, as speculated earlier, necessary to get around to the front side of the deck and unclip the head carrier bar in order to reveal the clips which would release the autostop arm obstructing access to the white cam and, underneath that, the broken yellow gear. Removing the cam while spreading the three delicate 'latches' holding it onto the spindle was an especially nerve wracking job.

So, here are images of the broken gear and one of the 3D printed gears which, as you will remember, was meant for a Philips 8443, not the 8334 I'm working on.

As you can see they are very similar indeed with the same number of teeth on the outer rim (39), the same number on the inner gear (14) and the same helical slant on the teeth on the outer rim.

All of these things put together make me think that the original gear from the 8443 (which the white gear is meant to be a copy of) is the exact same gear as the broken one in our 8334. Having looked at the white gears when I first got them my immediate concern was that there was a lot of dross in between all of the teeth, and, of greatest concern, the teeth on the inner gear are very truncated and 'blunt', so that the indentations between them are not very deep. By contrast, the ones on the original gear are very clean and prominent.

The first job was to clear out the dross from the centre hole and then drill it out to the correct diameter. Once fitted and with the deck mechanically put back together, I was surprised to find that the mechanism functioned perfectly, with just one problem: A 'ssst' noise once per revolution of the new gear, only when under load - ie, when something is loading the take up spool.

I didn't have time to take it all apart again but I'm hoping this is just due to some detritus in between some of the teeth of the new gear. I'll try doing a meticulous tooth by tooth clean up and see if that makes it run quietly.
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Old 13th Feb 2018, 12:34 am   #23
SiriusHardware
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Default Re: Philips D8334/05R - Toothless gears

Quick update on this, I decided the printed gears I'd been supplied with were just too rough and the inner cog in particular too poorly defined, with round 'bumps' rather than teeth.

I got back to the (USA based) company who had printed them and asked them if they would mind printing them again as slowly as possible at the highest resolution available and to my surprise, they seem willing to do just that.

To use a conventional printing analogy, the gears they originally supplied were so comparatively rough / crude that they might have been printed in high speed 'draft' mode.

I'm waiting to see what they come up with by way of improved replacements.

-More images of one of the printed gears (originally made for the 8443) and one of the original damaged 8334 gears. You can see how much better defined the inner cog needs to be.
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Old 13th Feb 2018, 3:04 am   #24
Boater Sam
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Default Re: Philips D8334/05R - Toothless gears

If re-printing fails, I would try using the old small cog implanted in the new larger gear.
If carefully inset with a backing stiffener on the plain side ( or even both ), epoxy glued, it should be OK.
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Old 13th Feb 2018, 11:51 am   #25
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Default Re: Philips D8334/05R - Toothless gears

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Originally Posted by Boater Sam View Post
If re-printing fails, I would try using the old small cog implanted in the new larger gear
I had already considered that until I found that the printing company seemed amenable to having another go, but my physical / mechanical skills are such that I would be very unlikely to be able to get the inner core perfectly centred and secure.

If it ended up offset by even a fraction of a millimetre it would cause problems. A good idea, supremely difficult to get exactly right in practice - maybe not for the small army of fine mechanical engineers among the forum membership here, but certainly for me.

At the moment my hopes are pinned on a better reprint.
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