Garrard Model 770

the jewel in the crown
jdjohn
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Re: Garrard Model 770

Post by jdjohn » 14 Jan 2019 16:49

Getting really frustrated with this unit. I've basically torn-down the entire tt, cleaned, re-lubed, and re-assembled it (can post more pics), but tracking on the inner-third of records is still bad. It sticks and skips very easily, and *if* it gets to the deadwax runout, it doesn't move across towards the spindle.

It was doing this before the full teardown, and I hoped a good servicing would help, but not the case. I pulled-off all the layers of the Unimech in order to finally get to the tonearm bearing. I cleaned the tube, post/pillar, and bearing (which is just a single ball-bearing between the post and that bolt mentioned in earlier posts). The arm moves freely, but again, gets stuck towards the middle when playing. Even with anti-skate set to zero, it gets hung-up. Btw, anti-skate is just a small-coiled spring.

I'm wondering if it simply wants/needs a cartridge with higher VTF. I've been using an M91E at 1.25g, but maybe that's not enough force. The arm seems very light to me in weight and construction, so I was hoping to use a higher compliance cartridge. But maybe it's not meant to be, especially with the spring-loaded VTF???

I noticed the SRA tilts forward quite a bit, likely because this is a stacker, and 'ideal' SRA is with two or three records layered. But I've used an additional mat to get the same effect, and tracking is still poor.

Any ideas?

DSJR
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Re: Garrard Model 770

Post by DSJR » 14 Jan 2019 17:27

1.25g will almost certainly be completely beyond this unit - hell, it was marginal on the full size models until after the Zero 100 came along and the later large format SB models*. I don't think the later SP25's (V and VI) and 125SB could track safely that low despite much work being done on the linkages under the tonearm! I seem to remember the 125SB managing 1.75 cleanly, but that was about as low as these could safely go I recall - the Unimechs weren't ever as good as this I gather...

* - My first 1972 AP76 wouldn't track end of side below 1.5g (maybe this one was faulty) although my current example is fine and free right to side end. My Zero 100 has a refined trip assembly from slider to pawls themselves and the 86SB I have is further refined along Dual's lines...

Look at the trip pawls and levers. They seem massive on this model (Duals and period Beograms are light, wafer thin and very frail in comparison on these parts). These almost certainly MUST be dry (no oil or grease anywhere) and totally free to move with no stiction at all!

Seriously, get either an AT91 (conical tip) or better, an AT95E (kind to sloping arms but with a nicely polished elliptical tip). maybe try to find a thick rubber or cork mat to put on top of the stock one to bring the arm nearer to level. Garrard used to supply a wedge to fit between the cartridge and carrier, one way round for decks like yours and t'other way for the AP76 which has the arm sloping upwards to the headshell (the original tonearm use was in the SL72B with lower set smaller platter, but Garrard altered this for the 76 model so the little wedge was used to make the cartridge more level).

The AT91 cartridge is surprisingly good, regardless of tip used. It's lively and utterly forgiving at 2g tracking and in its various forms, millions have been sold worldwide I reckon. The US price list also shows this for twenty nine dollars -

https://www.audio-technica.com/cms/cart ... index.html

Aluminium cantilever and more common further up the range. Not sure if it's actually in practise better than the 'carbon' cantilever. In the UK, the Rega Carbon is a nice 'posh' alternative and sells for twenty six quid over here, but it price-suffers in the journey across the pond, making the AT91 version a better financial bet.. FAR better than a dull old period Shure 75 EJ or 6s (Garrard sold the universal-75 body M93E here in their upper models - a safe 2g tracker) and with a far nicer diamond too ;)

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Re: Garrard Model 770

Post by jdjohn » 14 Jan 2019 18:27

Thanks for your reply, DS, Jr., and all the info. I'm looking through my stable for some higher-weight trackers, and might have some good candidates. I hate to buy a new cart when I have so many already :) I think an old AT10 might work at 2g, and be a good fit in that tier of performance. Nagatron 210E at 1.8g, but it has a nude mount that might out-class the 770 deck. I have an older Ortofon available, but will need to check the specs. Shure M44E at 2g is actually looking like a good prospect; it's also a heavier cart in general, so that extra mass would likely help. Most of those I mentioned are taller carts, so might help get the SRA right.

I was thinking my next mechanical check will be the trip pawl. It seemed very free-moving (and dry) to me when I removed the main cam, but worth another look. And you're right - it does seem to be larger than necessary compared to Duals I have worked on.

Thanks again!

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Re: Garrard Model 770

Post by DSJR » 14 Jan 2019 19:03

I don't mean to come across as a bleedin' know-all here. It's just that Ive been playing with these things since the late 60's and professionally since 1973 or thereabouts. Sorry to be a smart-arse here, but I tend to remember what works and what doesn't - and decks, arms and cartridges seem to stick in my memory as all else gets confused - cough ;)...

Garrard worked very hard indeed on the Autoslim chassis and the final SP25's and 125SB were light years different (better) than the mechanically related changers from the 60's. The 125SB didn't do badly in the first mid 70's HiFi Choice - Turntables and in fairness, BSR did similarly with the BDS80, a belt drive version of the HT70 which was an improved tall-platter version of the UK-famous MP60 deck (P128?). To me, the heavier tonearms of the SP25 III/IV and V range might have been better, but then, reducing mass ruled even though the arms became fragile and flimsy.

Glad you're doing all this work on this model, as by then, the market for HiFi decks had moved on and in the UK at least, the Pioneer PL-12D ruled the waves and sold hundreds of thousands over here! The Unimech decks were all but forgotten in UK audio shops and the larger models too, including the direct drive decks and belt siblings, just kind of faded away here I remember.

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Re: Garrard Model 770

Post by jdjohn » 16 Jan 2019 04:26

All good, DSJR :)

UPDATE: I diagnosed and fixed the sticking/skipping problem, and it wasn't at all what I originally thought. Using a higher VTF setting up to 2g appeared to work at first, but in the end did not fix the sticking problem. Sliders and trip pawls were all fine and moving freely. In the end, it was clearance between the bottom of the tonearm bearing assembly and chassis that needed to be tweaked.

The spring for adjusting needle-drop indexing hangs low at the base of the tonearm, and it needs to clear the chassis as shown here with the red arrow:
G770baseclearance2.jpg
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Behind the tonearm pivot, the indexing jig needs to clear the flathead screw as shown with the yellow arrow:
G770baseclearancerear.jpg
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Overall, the top clearance should be tight as shown with the blue arrow, and the tonearm pillar should be above the chassis as shown with the green arrow:
G770baseclearance1.jpg
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The way to adjust the height/clearance is via the bottom tonearm bearing bolt shown below. It has a 5mm bolthead, and of course tightening will raise the tonearm, and loosening will lower the tonearm.
G770tonearmbolt.jpg
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You can see below the bolt that the suspended chassis is supported by a glossy hardback book in the foreground, and a paperback book in the background. I used various spacers from around the house (as shown in the pic below) to try and get the chassis level for testing purposes.
G770test.jpg
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In the background of that pic, you can see the supportive cardboard circle I used to support the chassis when inverted. It slips inside the circumference of the platter space.

In the end, the sticking/skipping/bad-tracking I experienced on the inner-third of records was due to the indexing spring and rear jig not clearing the chassis properly. I was having all kinds of crazy movement on needle-drops, etc., and it was all due to that spring loading/unloading, etc. Once I sufficiently raised the tonearm post via the 5mm bolt underneath, all the tracking problems went away :D

I've played three albums now at 1.75g without any issues whatsoever. The challenge now might be to see how low can I go? Keeping it real: even playing well now, (via headphones) I have noticed a low-frequency swooshing noise in quiet passages, so this deck does have its limitations. It would highly benefit from a low-pass/rumble filter in the phonostage section of a chain. Still might be a good basic vintage used option...when properly serviced :D

I will post more pics of the teardown, but wanted to share my success with the tracking issue!

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Re: Garrard Model 770

Post by A70BBen » 19 Jan 2019 23:46

If that bolt is the one I'm thinking of, I ran across a Garrard 775...a 770 with S-shaped arm... that would not track below 4.5 grams. That screw had been tightened up too much, apparently at the factory, causing excessive friction. I slackened it so there was just the barest amount of endplay, and.that solved the problem. 1.5-1.7 gram tracking. The lower priced Unimechs...6-300, 440, model 62, 620S, etc... do not have that adjustable screw, they have a plastic cap and a thrust-bearing loading spring instead, nonadjustable. They track down to 3 grsms, according to the Service msnual.

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Re: Garrard Model 770

Post by jdjohn » 02 Feb 2019 02:38

I was actually able to get this 770 tracking down at 1.25g, but 1.5g sounds better, so I think that should be the absolute minimum with this deck. To run that low, I went with the M91E, and discovered something in the process related to cartridge alignment.

The headshell with the 770 does not allow for adjusting alignment, and it was really made to be used with a Shure M91/93E body with clip attachment. It has two fixed screwholes (not slots), so you basically mount a cartridge and that's it - no moving it or sliding it. During my initial testing, I used a spare AT71 variant since it tracks heavier, and I just wanted to see if I could get the tt working. Just for grins and giggles, I got a paper protractor out to see how alignment looked. The AT71 pointed towards the edge of the record on both Baerwald and Loefgren B, which means it would need to move backwards in order to get proper alignment. When I went lower with VTF, I swapped-out the AT71 for an M91E. You can probably guess now what I noticed. When I put the M91E on a protractor, it aligned perfectly with Baerwald and/or Loefgren B. Okay, I know it can't align (perfectly) with both, but it was so close that I couldn't call it, and the point is that the M93/91E bodies with clip are the way to go for getting the best alignment (and sound) with these decks. Apparently, their fixed overhang distance is perfect for Baerwald/Loefgren alignments with the 770, and other models, I'm sure.

I'm determined to add more posts with pics of my teardown of the Unimech. The cue lift damping assembly is next in the process.

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Re: Garrard Model 770

Post by jdjohn » 02 Feb 2019 04:25

Unfortunately, I did not take a picture of the Unimech after removal from the sub-chassis. But to remove the next layer of the Unimech, three screws need to be removed. Two of them are easily accessible and obvious, but the third one is covered by part of the cue lift assembly, so that has to be removed in order to proceed.

To remove the cue lift assembly, this is really the only screw holding it in place.
G770cueliftscrew.jpg
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Be careful of the plate and spring, but after removing this screw, the cue lift assembly can be gently lifted up-and-off, BUT attention should be paid to the tiny anti-skate spring, as it is anchored onto the cue lift assembly.
G770antiskcoil.jpg
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The spring can be carefully twisted-out of the anchor with tweezers.

Here is the cue lift assembly after removal:
G770cueliftmech.jpg
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G770cueliftmech2.jpg
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A70BBen
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Re: Garrard Model 770

Post by A70BBen » 03 Feb 2019 01:04

The Unimech Models 70, 770, 775 63SP and perhaps others were sold as an integral "Module" with Shure M75 and M9x cartridges so it is not surprising that they would align closely with them.