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Old 22nd Jan 2022, 3:01 pm   #1
OldKitMan64
Diode
 
Join Date: Jan 2022
Location: Bishops Stortford, Hertfordshire
Posts: 5
Default Testing before replacing Reel Motor A77 Mk3/4

After getting my Revox A77 case apart I have found the reason for a strange burning smell and lack of power on the right hand reel motor of my A77 Mk3/4.
I have attached a photo to show what I have found.
This looks like the failure.Click image for larger version

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Now - I have sourced a replacement motor from eBay (1.021.205) which looks fine but before I replace this I wanted to check voltages and characteristics of what I should see on the 4 supply pins (from the motor supply board) on the A77.
I think from the manual I downloaded these are D13 (Yellow), D14 (Green), D15 (Blue) , D16 Brown.
I have not found yet how to check the supplies before swapping over
Does anyone have any test procedure on this that will help me out.
I have access to a good AC/DC multimeter and somewhere in one of my cupboards I have an old Philips Oscllioscope but have not used it in years.
Any help and pointers on this would be much appreciated to ensure things are stable before putting in the new motor
What is puzzling why the reel motor would fail like this. Anyone else seen this happen ?
Thanks
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