Garrard RC121 4h Size Selector Issue

[PsychMan]

Hi Folks,

I have a restored Garrard RC121 4h deck in a Fenman RM radiogram.

I was moving it to another part of the house so thought I'd take the opportunity to look at few minor issues while I did.

One being the size selection mechanism. Now, this has been stripped down and relubricated well by another forum member, and initially I noticed noticed wrong with it as I only play 78s on it.....

But what happens is you set the needle set down position correctly on a 10 inch 78. It works great for 78s, 12'' and 10'', sizes detected and set down works as calibrated.

The minute you change the turntable speed to say 33rpm for an LP, the set down is off slightly, enough for the stylus to not land on the lead in.

You can set the calibration again, and it will be fine. Put it back to 78 RPM, and it then needs recalibrating!!

So all sizes work fine on 78rpm when calibrated, but change speed and it needs adjusting. If you go back to 78 of course, it behaves as calibrated.

I cant work out how this could be. I thought the only difference in operation with the different speeds was just that - the speed which the turnable rotates and in turn the automatic mechanism works.

At least that has been the case on every other autochanger I have worked on. Slipping problems on the idler would surely slow both platter and mechanism down in equal measure?! Though actually an RPM meter puts this deck as VERY accurate within 0.5 bpm anyway.....

I will have to dig out the manual to check im missing something....But any ideas?

Cheers
Adam

[PsychMan]

The manual doesn’t offer any assistance here as suspected.

I’m beginning to think this might relate to spring tension around the size selection arm - some springs look like they might have been replaced or re-tensioned, i imagine as part of the overhaul.

I wonder if too much spring tension could cause the selection arm to move too quickly, such that the size selection doesn’t work correctly at lower speeds. The speed of the mech itself will be dictated by the platter speed, but the movement of parts due to spring tension won’t

I remember having a problem on a 121 mk2 where a change in spring tension had caused some problems..

[Michael Maurice]

How far out of calibration does it go when changing speed?

I reckon its something to do with the speed that the turntable rotates rather than the mechanics of the speed change.

[PsychMan]

I agree it’s not the speed change, I wasn’t suggesting that but may not have been clear enough.

All the speed change seems to do is move the idler away from the motor pulley and return it higher or lower to make contact with the correct step on the pulley.

It doesn’t go out by much, But enough for the speed to be unusable without calibration.

I can get it perfect for 78 rpm records (of any size once adjusted for 10” records) say just past half way in on the lead in grove. If I then try a stack of 33rpm records (again of any size), the needle sets down say 5mm away from the edge of the record.

On this record changer, the size selection arm comes across to detect the record size then flips back. There are some springs involved in this so the speed of this operation would be static, and depend on the spring tension and how freely it can move. Perhaps this has changed and no longer occurs at the correct time for the change cycle on lower RPMs...

Frustrating fault but I’ll get there!

Adam

[Michael Maurice]

Are you absolutely sure that this deck was stripped, cleaned and relubricated? I don't know about others, but I think this might be a lubrication problem.

[PsychMan]

Yes as sure as I can be. I know the previous owner is a user on here and posted about his work on it, which incidentally was very good throughout the radiogram, and if only playing 78s the fault would never have been detected. The grease that is there all looks good and recent

[PsychMan]

Well, I've given up on this particular fault. I think you're correct Michael, there could be some dried grease lurking somewhere much deeper in the mech that had been missed on the previous stripdown. Though usually the change cycle looks less smooth when this is the case...

I experimented a bit with spring tension around the size selector arm, no change.

While trying different speeds, I noticed that on 16-45 rpm, the idler was slipping a bit sometimes and there was a bit of "slop" in the speed change mechanism. I spent some time on this and wondered whether this could be linked to issues in the change cycle.

I replaced the spring attached to the idler assembly from one off a scrap deck, this made a big difference. I ensured the pulley, idler and turntable rim were all clean (wiped down with alcohol). A surprising amount of muck came off the turntable rim actually..

But upon re-assembly, speed change is now solidly working, but the size issue remains...

I probably wont resolve this until I completely dismantle and overhaul it myself. I simply cant justify the time to do that right now, for a deck that will only be used for 78s. Maybe one day...

[Michael Maurice]

I normally replace the idler with a rebuilt one from Terry's rubber rollers. Be careful stripping those decks, they are very complicated.

[PsychMan]

Oh, I know all too well how these decks can be, I've stripped and refurbed a few RC121 MK2s! Really, the size selector mechanism, while useful, is a pain in the backside for folks like us!

I shall have to look into Terrys rubber rollers, I have a Rockola jukebox that desperately needs the idler re-doing, I wasn't aware anyone could do that kind of work

The idler on this deck is very soft and supple, I imagine its not original. I find some of the later idlers made in the 70s (?), and found on SP25s for example, to last much better than those from the 50s and 60s.

Cheers
Adam