March 28, 2022 at 9:08 pm #3619
My first post on Beoworld forum. I’ve been restoring a BeoGram 6000 turntable, and have regained the audio output by replacing both transistors in the series regulator on the RIAA pre-amp circuit board. So it now plays.
But my next problem is mechanical: the 3 spring steel plates that are supposed to hold the platter in suspension (away from the chassis) must have lost some of their spring. I thought I had fixed the problem by raising the screws that hold the plates in place, but then then they are too high to allow the brushed aluminium covers to be replaced.
Has anyone come across this problem, and know a fix? Can the plates be re-bent to restore their spring, or does this risk breaking them?March 30, 2022 at 2:24 am #3640
I have never seen the leaf springs fail. I have seen the plastic inserts break down and leave pieces interfering with the suspension. I would carefully examine the transport screw mechanism for these. When I do a referb of either 400x 0r 6000 I remove the entire sub chassis to clean out the pieces left behind. If you do remove the transport screw assembly be careful of the multiple washers and there orientation and ordering.March 30, 2022 at 5:37 pm #3663
Thanks for your helpful reply Mark-sf.
Yes, the plastic inserts in the transport screw mechanisms had broken into lots of pieces and fallen into the bottom of the chassis. I’ve picked them all out as far as I can see, and they don’t seem to be interfering with the suspension. But a complete strip-down is beckoning.
I still can’t figure out why the leaf springs don’t seem strong enough to hold the sub-chassis in suspension. They’re struggling to bring the platter surface level with the surface of the cover plates… Also the platter isn’t quite central in the opening in the main cover; the service manual suggests that the leaf springs can be moved side-to side to adjust this, but on my model no adjustment is possible.
Maybe a strip-down will reveal all! (The label inside my unit says it’s a model 5502.)March 31, 2022 at 6:10 am #3674
First, confirm all of your springs curl up when the sub-chassis is unhooked. Then you use the rear nut to bring the sub-chassis high enough to float between the lower and bottom stops. Then tweak the three nuts to ensure the platter is level but not necessarily even with the top plate. If you then need additional height, you can loosen the locknut on the center bearing and raise that as it is threaded. You will then need to make sure your arm cued-up position will still clear the record.
As to centering, there is some side play in each leaf spring and you can also get some side or front/back play by slightly bending the rear height screw. I have never seen the need for more than 1-2mm of adjustment. If you do then look at your top plate alignment as that is likely out.April 8, 2022 at 7:59 pm #4034
Thanks again for your guidance, Mark-sf. After lots more tweaking, I discovered how the position of the leaf springs can be adjusted just enough to centre the platter – as you pointed out in your first post. So I’ve got it pretty much sorted now. The platter is central, and the top surface is exactly level with the cover plates – until I place the drive belt over the motor pulley! It’s a recently purchased replacement belt, and I suspected right from the start that it might on the short side, as it was a tight-ish fit just around the drive surface of the platter. Can you recommend a reliable supplier for replacement belts?April 9, 2022 at 12:00 am #4037
The belt should be 88mm in length. You can measure it by aligning it flat with just enough tension to have the two sides flat against each other and that should measure 44mm. One reliable vendor is here at https://www.beoparts-shop.com/product/platter-belt-3/ if it turns out your belt is over 1mm shorter. Also make sure that the pulley height is such that the belt runs fully on the subplatter.April 17, 2022 at 7:36 am #4255DillenBRONZE Member
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Transport screws fully losened?
MartinApril 19, 2022 at 9:05 pm #4325
Thanks again Mark-sf. I just got back from hols and measured my drive belt using the method you suggested. It is 560mm long. I think your figure of 88mm must be for a different belt? But thanks for the link to Beoparts-shop – this is a really useful, as they also sell the drive belt for the carriage servo motor, which I need.
Martin – thanks for the reminder about the carriage screws. I think these are fully withdrawn but will check again!April 20, 2022 at 12:37 am #4327
Sorry, there was a typo in my response. I meant 88cm.April 20, 2022 at 9:48 pm #4356
So if the correct belt length is 88cm, and mine is 56cm, then it’s seriously under-sized! This explains a lot. Time for a new belt.
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