Hi Rob,
Yes I'm at 2.5 grams, and the first one (closest to record start) is right up against the reed switch and works nicely to stop the inward drift. You are right, it controls that bit of no man's land where the cam spring has disengaged and the arm is in freefall. However, the one closest to record trip, I have to bend it almost horizontally. Any closer and it literally pulls the arm in really sharply. It's so apparent that I'm sure it would do some bad record damage if left like that. I can't help but thinking it should be at least reasonably close to the reed switch like it originally was.
If I remove the magnet completely, none of this happens so it's definitely the magnetic pull.
I thought about using an opto sensor as a bit of an inquisitive experiment. I think some of the later NSMs used them.
Do you have any documentation on how they should be adjusted ? I've got 3 or 4 manuals for jukeboxes with the 1100 in them but none of them mention their purpose or adjusting them.
Nigel
On 8 Nov 2023 at 19:32, Chan Gade via Jukebox-list jukebox-list@lists.netlojix.com wrote:
Nigel, those two “fingers” are an anti-drift anti bias device.
With careful positioning they can slightly prevent the arm from boosting inward at the start of a record when the keeper on the can releases it.
I allow –slight—inward drift at the spiral.
They are touchy and very slight changes make a difference. In the original spec’ of 5 grams VTF it didn’t really matter. Since i use a better stylus and ran them at 2 gm I wanted the best possible setup.
RobNYC On Wednesday, November 8, 2023 at 09:54:21 AM GMT-5, Nigel Pugh via Jukebox-list jukebox-list@lists.netlojix.com wrote:
Rowe 1100/1200 anti skate.
Having some issues with my JBM and the erratic stylus landing point. Its none of the obvious suspects. What it is, I have proven, is the magnet that operates the trip reed switch is dragging the arm inwards. The whole assembly has become magnetised. As the record lands, before stylus touches groove, the magnet pulls the arm in a little. Ive replaced the reed switch with its metal bracket from an unused spare and de magnetised the area with a tape head demagnetiser. Thats all fine, and it works perfectly again.
But, my question is, behind the reed switch are two brackets about an inch apart. I have always thought these were a crude anti skate system. However, the bracket nearest the end of record play has to be bent right back. If its by the reed switch the arm really swings back due to the magnet and bracket attracting to eachother. Now magnetised or demagnetised, shouldn't matter, as metal to magnet will attract anyway. I can see how it could have been designed to bias the arm alightly outwards towards the end of the record to compensate for the natural pull inwards, but with this bracket in the correct place and not bent back, its brutal. Is it possible the actual trip magnet has got stronger over the years ??
I think you need to be very familiar with this mechanism to understand what i am saying as its not related to any others in the way this is set up. It's going to be an age and materials related issue as I've literally worked on 100s of these Rowe's on site and restored, and surprisingly only my own, which was only out of use between bar and my house for 2 years in the mid 80s, and has been used every single day for a few hours since, is the only one I've seen the problem on.
Tone arm missing record trip is removed and cartridge wire is off a Rega tonearm, there are no other factors it is 100 percent magnetism.
I shouldn't have to bend this bracket back as that's definitely not where it should be....
If I can find the parts in my shed I'm tempted to replace it all with a simple Rock Ola blade switch instead.
Nigel, uk.
Jukebox-list mailing list -- jukebox-list@lists.netlojix.com To unsubscribe send an email to jukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives: http://jukebox.markmail.org/
Jukebox-list mailing list -- jukebox-list@lists.netlojix.com To unsubscribe send an email to jukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives: http://jukebox.markmail.org/