JVC Dynamic Drum Ultimate Fix

[dellsam34]

I don't quite understand what was done in those videos either, In the video if I remember correctly he is claiming the DD system control looks for motor movement through the butterfly shutter mounted on the motor shaft detected by the corresponding optical sensor as well as the correct position of the halfmoon gear which has to block the other optical sensor but it doesn't have to show movement (or vise versa), I though both sensors have to detect movement, If this turns to be true it simplifies the mechanical bypass and I may have to come up with a revised version of the mechanical bypass, but I think hkorpim is the right person to confirm or debunk this new theory demonstrated in those videos, At the moment I don't have any spare VCR that I can experiment with.

[lordsmurf]

12voltvids opinion on jvcs with DD Drum is that "they are all junk." On the other hand he praises FUNAIs for their simplicity LOL. As he grows older, he becomes more careless and bored. He now repairs cheap VCRs with profit in mind, not technology and preserving authenticity. Pay attention to his desk. It's dirty and he drags delicate machines against wood. He judges machines based on the profit he can make by repairing them. If they are complicated, he doesn't touch them. He has stopped examining them thoroughly like he did years ago.

Quoted because it needs repeating. I've stated this exact sentiment for a few years now. It's nice to see that others are noticing the same.

[hkorpim]

Thanks, Aristarhos, for finding DD repair videos by NorCal715.

That, added with comments by dellsam 34, made me testing the sensor topic once again. Based on my results, it seems, that his testing of repeated picture play function changes were not sufficient. DD motor rotation sensor (1st sensor, butterfly shutter) is sufficient as long as there is no need to tilt the head drum, but once switching to picture search and back from that, the vcr needs confirmation also from 2nd sensor (neutral position, halfmoon gear) and if that signal is not present, the vcr will either directly shut off or alternatively gets frozen while waiting for the signal.

On the other hand system processor allows to repeat some function changes to overcome individual error states before SHUT OFF, but if the error gets repeated enough times, it’s resulting to SHUT OFF. I have just uploaded a new video, link below, of my testing, that hopefully clarifies, that signals from both sensors are timely needed in order to keep the vcr operating correctly in every situation.

My video also presents the conditions to use DD gearbox remote mounted if one ore more "outer gears" have cracked.

https://youtu.be/qWe23c6ZbQI

[dellsam34]

Nice experiment Hkorpim, As much as I wanted the 2nd sensor to be not needed, at least now with your confirmation I don't have to revise the mechanical procedure.

[Tony90]

Nachdem mein JVC 9500 sich nicht mehr einschalten ließ, ergab sich folgender Fehler: Der DD-Motor hatte einen Totpunkt, weshalb es zu keiner Signalfunktion kam. Ich öffnete den Motor, reinigte den Kommutator, erhöhte etwas die Vorspannung der Schleiffedern, ölte die Lager und baute ihn wieder zusammen, er läuft einwandfrei! Nach Entfetten der Zahnräder wurden die Stirnseiten der Räder und der Metallwelle mit Sekundenkleber verklebt. Die Trommel wurde mit den zwei Stellschrauben auf einen Astand von ca. 1mm gleichmäßig auf Abstand zur Grundplatte gebracht und mit den Federschrauben blockiert. Da nur die Zahräder für die Signalgabe blieben, läuft das Getriebe völlig lastfrei mit der Hoffnung, dass es so noch eine Weile hält. Nach leichter Korrektur des Bandlaufes funktioniert der JVC wieder einwandfrei.
Zum Glück bekomme ich aber nun einen DDemulator von Heikki Korpimaa, wodurch alle Probleme endgültig behoben sind.

[hkorpim]

Gut gelöst, Tony90!/ Well resolved!