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Automatic Trip Pawl - Garrard SP25 Mk II

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Automatic Trip Pawl - Garrard SP25 Mk II

Postby paul1981 » 07 Jul 2016 18:57

This is the upper pawl from the auto trip mechanism. I've looked at many photo's online but couldn't find a side view. I'm pretty sure it's not supposed to be bent like that, but I know you chaps on here will know for sure.

This deck in question part of a Dynatron unit which belongs to my brother-in-law which I'm fixing up for him, and it had been in his parents loft for 30 years from what I can gather. It had the old grease (or glue you might say) issue with the lower pawl which was totally seized which meant the arm would only go 3/4 across and then get stuck. After servicing (various issues with deck and Dynatron), it is all working. Well, that's what I thought until I carried it downstairs yesterday to have a really good listen and to enjoy it before returning it back to him. It suddenly decided it was going to auto return too early... approximately half way through the last song on an LP for example. It was doing this all day yesterday, and this happened every time, repeated tests when the arm is on 'lift' confirmed it.

I took off the table and re-studied the trip mechanism. That's when I noticed the slight marks, like little round dents in a line (possibly from pliers) on the upper trip pawl (both sides) and then realised that someone could have bent it. I then managed to question myself as to how this mechanism actually works. It seems as though the upper pawl relies on the friction/rotation of the circlip along with the shaft on which it sits on in order to rotate it towards the table gear BEFORE the lower pawl pin actually does. Am I wrong? The whole thing 'rattles like a tambourine', so there's nothing actually wrong with it as far as I can make out.

Today I took the machine back upstairs, and guess what? Working fine, auto trips in the correct place...working fine now! I'm thinking 'this deck is either playing games with me or it loves me and doesn't want to leave me!'

Question, is there an actual adjustment for the trip point? There's no mention in the service/user literature of such an adjustment. Perhaps some part of that mechanism underneath the deck has shifted and then shifted back when carrying? I'm too lazy to look myself as I've had a belly full of this Dynatron these past few weeks - you know how it goes. :D

Any advice would be gratefully received.
Attachments
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Re: Automatic Trip Pawl - Garrard SP25 Mk II

Postby A70BBen » 08 Jul 2016 03:56

It's bent. It is supposed to be straight in the side view, lying flush to the surface below it. The vertical tab is just that...vertical, at 90 degrees to the main part of the lever.

Should be easy to straighten...and there is no adjustment for the trip point. The velocity-type trip mechanism is self-adapting.

This upper lever is moved by friction on the upward round lug from the lower lever...not the circlip or shaft...but has to be able to also slide on it. The trip mechanism has to "adapt" to different end-groove diameters. When the arm is tracking recorded grooves the vertical tab gets pushed back and "reset" by a projection on the platter hub...it is not ready to enter the auto cycle...but when it tracks the faster leadout grooves the projection engages the tab solidly, rotating the main mechanism gear into mesh with the gear pinion on the platter.

Don't neglect the lower auto trip lever. Remove it, thoroughly clean it of all grease and residue, polish its shaft and the hole in the main gear if you wish, and reassemble the trip mechanism, DRY, no lubricant. Clean off the vicinity of the main gear, too; grease that has crept along it over the years, and contaminated the DRY trip mechanism is what causes the trip to stick.
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Re: Automatic Trip Pawl - Garrard SP25 Mk II

Postby paul1981 » 09 Jul 2016 21:00

Thanks for your Help. I fixed this yesterday and was enjoying the machine all evening.

The upper trip pawl does move with the circlip beneath it (because the circlip is tight on the shaft) and the weight of the upper pawl on this circlip does indeed Help it move before the actual lug does....but you're correct in that it doesn't matter, because as it gets near the end of the record the upper pawl tab will constantly get nudged back slowly with every rotation of the turntable by the edge of the flat portion of the gear - until of course, like you say, the record hits the run off section causing the upper pawl to be contacted directly by the flat portion of the gear, which in-turn starts the cam to rotate. And I say this for the benefit of other people like myself who may come across this problem - I am not intending to insult your intelligence or anything, I know that you know how it works :) - I just hope it will Help other people who may come across this same issue.

I'm really happy with how straight I managed to get it. Not perfect, but perfect enough. There were burrs as well on the tab which I have taken out. The upper pawl just sits better now, it looks correct and it looks happy as it sits there awaiting its next trip.

I didn't do anything to the turntable gear. Looks like the whole deck has had lots of hammer to me though. I think the bent tab has caused the uneven wear on the ramped part.

When the upper pawl was bent then, it must have been binding just enough (even though the whole auto-trip parts/cam were rattling like a tambourine) to oppose the gentle nudging action of the end of the ramp/flat edge of the gear. Perhaps the burr was helping it grip too, adding to the problem. As for why it didn't work correctly when it was downstairs, I'm guessing the surface flatness (or lack of) actually showed the fault up more, so it's a good job it did really.

Anyway, thank you very much for your Help, it really is appreciated.
Attachments
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Re: Automatic Trip Pawl - Garrard SP25 Mk II

Postby paul1981 » 09 Jul 2016 21:08

The first photo is not for the faint of heart...

The counterbalance weight has had an equal amount of stick as well. But for it to still be here today despite such abuse, I think speaks volumes as to how tough these decks are. Well done Garrard.
Attachments
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Re: Automatic Trip Pawl - Garrard SP25 Mk II

Postby A70BBen » 14 Jul 2016 02:11

You did well, and I'm glad you are enjoying your SP25! Further, you have saved a classic machine...which was built in a way that modern makers have forgotten. Congratulations!
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Re: Automatic Trip Pawl - Garrard SP25 Mk II

Postby baz1972 » 21 Nov 2017 16:24

hi there,
did you have any problems removing the cog ? I have the same problem and cannot remove the cog, any suggestions ?
cheers
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Re: Automatic Trip Pawl - Garrard SP25 Mk II

Postby DSJR » 21 Nov 2017 22:29

Haven't we been there before in another thread? You'll have to sweat it off with some heat. It does work doing this as the grease does melt enough for the cam to be removed and I think 'we' discussed other parts of the mech which can be cleaned and left pretty dry and other parts needing just a smear of grease. Those trip pawls pictured above should ideally be left dry after cleaning and replacing as any lubricant usually causes them to drag and 'stick' too much.

Tough old decks these Autoslim derivatives. I remember an SP25Mk2 in use in a record shop and spinning eight hours a day almost continuously for twenty years before it was replaced by a tacky midi-system thing that probably only lasted a year or two before it failed.
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