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Old 7th Dec 2017, 11:46 am   #17
shawthing
Triode
 
Join Date: Oct 2005
Location: London, UK.
Posts: 40
Default Re: Revox A700 flutter only at 7.5ips?

Thanks Timtape, Gramofiend and Radio Wrangler for your replies: I am indeed familiar with the tape tension being a part of the system that might affect things.
Last night I thoroughly cleaned and very lightly oiled the tension rollers' shafts (another quick and easy job that can be done form the front), the pinch roller shaft and the flutter roller. I'd given them a quick going over previously but I think I may have missed some tiny hardened deposits on the shafts which perhaps were enough to cause less than perfectly smooth rotation: this seemed to produce a slight improvement but I'm not sure this is really where the problem is. Interesting though that this should affect speed stability at only one speed, not all three.
To Timtape, I used the word 'flutter' on purpose as that's what I'd say it is: I understand the difference between the two, and I'm talking about fast speed variation, audible in the upper - or perhaps upper mid - range, say 500Hz and up: held high or high-mid piano notes or chords that should be steady are audibly not.
I'm going to have to postpone further investigation until I finish work (9-5 work that is) for Xmas in a couple of weeks - and I can then move the machine from where it usually lives onto the workbench and go through it properly, get out my W&F meter (a very good Meguro one) and scope and see what's happening.
I do also have some spares of the rare chips but not sure I have spares of them all, or whether they're actually working or not (bought years ago and untested!).
I agree these are complicated machines and that Revox were perhaps a little ambitious - they were part of the late 60s / early 70s crossover between hi-end hi-fi and semi-pro kit - you can see from their brochures the whole range, and the A700 incorporates an entire amp section, multiple inputs, routing etc and they really went to town.
Interested to read of experiments between A700 and B67 as I too have wondered about moving boards between the two...
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