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Old 8th Apr 2019, 3:33 pm   #1
Hartley118
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Default RGD-branded Garrard 78 head - How do I replace stylus?

I'm just tackling the restoration of a Garrard RC60 autochanger with an RGD branded pickup head (78 only). I'm pretty sure that the unit comes from a 1946-ish deluxe RGD 1046 radiogram (push-pull PX4s etc) pictured below - acknowledgement RGD museum website.

The autochanger runs wery well, complete with its ingenious record size detector. The challenge I have is with the pickup head. As far as I can see, it's a customised version of the Garrard 1940s miniature magnetic 'High Fidelity' head, reputed to be a remarkably good performer for its time. Mine has a good 5000 ohm coil and plays cheerfully but, unsurprisingly it needs a new sapphire stylus and new internal rubber suspension for the armature.

But I can't get inside the pickup head.

I've removed all relevant screws, but nothing budges, including the original stylus. As far as I can see, this must be one of the first pickups to use a jewel stylus instead of conventional steel needles: there's no needle chuck or retaining screw. Imagining that the existing stylus might be just an interference fit, I've tried grasping the aluminium stylus shank with instrument pliers and pulling, but it's firmly stuck: any more force and it'll break off, landing me in deeper trouble. Were the designers so enamoured of the new-fangled sapphire stylus that they made it a 'fit and forget' item? I do hope not: surely a sapphire must have been designed to be replaceable? I have what looks like a suitable brand new vintage spare ready to fit, but need to remove the original first.

The magnet/coil assembly needs to come out if I'm to replace the rubbers, but it seems intimately stuck inside the bakelite head moulding. Tolerances are very tight with barely a gap to get any sort of lever in. I've used the hairdryer treatment to warm up and expand the bakelite, but to no avail. I have noted that bakelite seems to shrink over the years and tighten its grip on any internal assembly, but this is either totally vice-like or else has some adhesive involved.

I'd be most grateful for any advice from any member who's successfully tackled a similar problem, whether it's 78 stylus removal, or releasing an assembly from the grip of bakelite. For example, what adhesives were in use in the 1940s? Am I likely to be able to soften the adhesive holding that front anodised aluminium 'RGD' plate on? That would probably expose the internal gubbins.

I attach some relevant photos, including one from the RGD Museum site of the 1046 radiogram. Aside from my challenges, this RC60 and its miniature high quality Garrard/RGD head make an interesting example of the quality of the best of early post-war 78 playback at the time when record manufacturers were progressively improving their recorded frequency range.

Martin
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Old 8th Apr 2019, 4:49 pm   #2
tracypaper
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

Hi.
Never seen one of these before but looking at your picture 4 I agree that taking of the anodised plate is your best bet and that notch might be helpful?
Gaz.

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Old 9th Apr 2019, 10:28 am   #3
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

That looks depressingly like any steel parts inside could have rusted and swollen into the bakelite housing.

Repeated careful levering with suitable sized screwdrivers in any handy slots might help but you could end up with a broken head. Don't know whether "Plus Gas" would help release any rust or hinder by swelling the bakelite.

Does anyone have a good, easily dismantled one, to post pictures showing how it all sits in the shell? There might be some mileage in strategically drilled holes to allow the guts to be pushed out. The holes can always be filled afterwards with glue/bakelite powder mix.
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Old 9th Apr 2019, 1:14 pm   #4
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

You could try applying freezer spray to the needle while the Bakelite is warm to increase the differential thermal expansion.

No personal knowledge, but I was under the impression that diamond styli were available pre-war. In one of P G Woodhouse's stories, Jeeves uses a diamond gramophone stylus to check if a gem is genuine.
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Old 9th Apr 2019, 1:34 pm   #5
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

I don't think it was a diamond stylus but my father's Garrard RC 4 had a Garrard magnetic head with a very long life ( sapphire? ) stylus. This was back in the very early 1940's
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Old 9th Apr 2019, 4:02 pm   #6
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

I wonder whether it would take Columbia 99 needles. As far as I know they were just an interference fit. If it is beyond repair could it be replaced by a standard Garrard head and a ceramic cartridge?
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Old 10th Apr 2019, 12:43 am   #7
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

I have been asked by a friend to upload the attached pictures.

They show the Garrard stylus once removed from the head.
Gentle leverage on either side of the plate should allow the unit to be removed from the body once you have broken the seal made by the rubber washer which will now have gone hard and will be stuck solid.

Hopefully these pictures will help you.

Mike...
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Old 10th Apr 2019, 8:58 am   #8
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

There seems to have been two versions of this pickup head, see attached. The bizarre thing is the pictured stylus, which looks like the one in #7, looks more like it's for the non-replaceable version!
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Old 10th Apr 2019, 5:09 pm   #9
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

I'm delighted to report progress thanks to our informative members.

The helpful Garrard catalogue extract from WD40 addict confirmed that there was a version of the High Fidelity pickup head that had to be returned to Garrard for stylus replacement. And that's the one I've got! Clearly the designers had an over-optimistic view of the life of the then new-fangled sapphire stylus. By modern stylus criteria, bearing in mind its tracking force of around 25 grams, that would have required the user to return the head after playing some 50 discs. Interesting too that the head was clearly a Garrard product rebranded RGD in this case.

Having established that there was never an easy method of stylus replacement intended by Garrard, Mike Barker's post with photos (courtesy of his friend) was particularly valuable in giving me the confidence to remove the silver-coloured sole plate, showing that it would be stuck on by the perished rubber washer. Local heat was the answer: I heated the soldering iron to 400C and applied it to the sole plate until I could smell hot rubber. Gradually then the perished rubber softened and I was then able to gently lever off the sole plate.

The attached photos show the polepiece/armature/stylus assembly removed from the magnet/coil unit which is clamped (maybe stuck with adhesive) in the bakelite head housing.

I'm aiming to replace the old rubber washer suspension with a disc cut from suitable latex from a rubber glove. That'll require some experiment because there seems no centring adjustment for the armature.

As far as I can see, the armature is held neatly by a tiny torsional suspension where it passes through the sole plate. That's still flexible, providing lateral compliance but preventing fore & aft movement. It will need the additional stiffness of the rubber disc, and perhaps some miniature rubber tube round the armature, to provide stability and prevent the armature being attracted to one or other polepiece.

The real challenge will be attaching the new stylus. The original stylus has an aluminium shank which seems to have been clamped permanently in the upper part of the squashed tubular iron armature. I need to attach a new stylus securely without adding significant mass. I wonder about a strong type of Araldite such as 'Steel Weld', but am doubtful of its adhesion strength to aluminium.

So it's a now a further work in progress. I'm so glad that I sought the advice of this forum. If all else fails, I could take Paul's advice to fit a new cartridge: I'd probably use the Garrard recommendation and use one of my Decca XMS collection which Mike B has done a great job rewinding. However, for now I'll persevere because I want to test just how good was this innovative Garrard High Fidelity head and how it compares with a Decca XMS which I believe came a year or so later. It was probably ahead of most available recorded 78 disc quality of the time, with the likely exception of Decca FFRR discs.
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Old 10th Apr 2019, 7:03 pm   #10
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

Glad to help a fellow 39//JH owner

The page actually comes from 'Points on Pickups', the cross reference stylus / cartridge guide once issued by Farnell.
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Old 10th Apr 2019, 7:11 pm   #11
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Default Re: RGD-branded Garrard 78 head - How do I replace stylus?

In my experience, ordinary Araldite grips Aluminium securely. In the early 1970's I made a power supply in a recycled folded Aluminium box with several holes that had accommodated potentiometers. I filled them with what I guess is now called Araldite professional, and the filled holes are still secure. I did roughen the edges, followed by a clean with IPA.
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