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  #121  
05-23-2021, 06:51 PM
latreche34 latreche34 is offline
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By studying the DD mechanism further based on the new document that Hodgey posted I learned new things, The sensor coupled to the motor is called pulse counter, That's what determines how much the head tilt is based on the motor rotation direction, forward the pulses are +, reverse the pulses are -. The other sensor with half arc flap is the reset sensor, I believe that doesn't send pulses it just reports the position of the drum every reset to make sure it is in the neutral position, I'm assuming that gear turns very slow and for the entire position spectrum from left to right it turns half a turn.

I will keep posting when I learn new things and hopefully we can come up with an electronic solution, Though the disabling of gears is a must and cannot be avoided for a perfectly aligned head, or at least not leaving them in the wrong positions if the motor were to be disabled. So the head neutral position procedure that I posted at Videohelp has to be done unfortunately, there is no way around that.
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  #122  
05-24-2021, 12:36 AM
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deter deter is offline
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Yes I kind of agree that with that plastic gears causing these machines to go in loading mode is a bad design. Quality was always an issue for me and getting the best possible quality out of a tape. Go check the records on this site the 1st high end VCR that I got was the 7800 besides the broken down AG-1980. I purchased it for $40. The 9900 is a 10 times better machine in my opinion. I just repaired a guys Panasonic Japanese VCR which kind of looks like the JVC 9000 series I would put that one on the lists of VCR's to use. The 7800 or 7600 or the JVC SR-V101US or the other model like that I am going to say no. I fix AG-1980's, in the last 3 years did 33 repair jobs for members of this site and video help. Not one person has come back and said I need my AG-1980 fixed again or I am having problems with the picture. Those machines you can get to last for a really long time.
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  #123  
05-24-2021, 03:58 AM
latreche34 latreche34 is offline
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Yes, quality always matters for capturing valuable memories that's how we got into this hobby in the first place.

If we can find a way to disable the DD motor entirely by a mean of electronic pulse mimicking, the entire drum assembly can be replaced with a fixed style drum from a newer VCR with the same type of mechanism, The new head has to have the same head count, the same stator poles, In other words the head ribbon pins and motor ribbon pins have to match perfectly.

I have a working VCR with a defective DD drum system that is in storage right now, I will try to get some free time and get it, Then I use the oscilloscope or the true RMS DMM to measure the frequency of the signal coming from the motor sensor during initial motor check and its trimmed voltage, using that we can source out a tiny frequency generator that feeds those pulses directly into pin 59 (DD_FG) of the main processor ICU3001 and 5V supplied to the DD board CN3701.

As to the second sensor, as I said above I think it just reports ON or OFF position, meaning that if the flap covering the sensor, it is OFF if not, it's ON. I will have to double check that as well.
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  #124  
12-28-2021, 04:12 AM
Blackout Blackout is offline
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hi latreche34....you have taken my thread to the next level indeed. Ive been thinking for a long time about how to bypass this whole DD system and you seem closer than anyone else at achieving it....you are on the right track for sure. Some kind of piggyback board that connects to those pins 1-6 and sends voltages that mimic the sensors is where the solution lies. Please keep going with this investigation....

"Every day, somewhere around the world, another DD fails." - Blackout
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  #125  
12-28-2021, 01:55 PM
latreche34 latreche34 is offline
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Good to hear from you Blackout, You have been gone for a long time, I hope everything is alright. Yes I'm trying to get around this but too little time to spare, I have some other designs I'm working on for other commercial purposes, between design and prototyping and testing and working full time, Very little time left for my hobby, I will get one on a work bench and poke around with my oscilloscope to find out what the frequencies are and go from there.

https://www.youtube.com/user/latoak34/videos
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