Not quite - the B77 uses triacs that are logic controlled - same idea different method
Hi BrianYep! In my "childhood" in this biz, I first recall seeing that design in the Ampex MM1100 multitracks. Earliest versions were (in)famous for blowing up the Delco branded power transistors. Big clue....power up the recorder with no tape loaded and one (or both?) of the reel motors would run full torque.
Bri
Indeed....earlier model MCIs (JH-100???) also used AC reel motors and the diode bridge design.Hi Brian
That is right, the venerable Ampex MM1000 used a very similar motor drive configuration:
Mark
Cost savings, it is not a Studer. Spooling motors just require different voltages for tape tension and fast wind while servo control of capstan speed is mandatory.Yeah - seems strange to adopt two different systems for drive control.
I had 2 A820’s synced up to run as one using a modified Tascam controller ES50/51 I hacked. I ran these machines for 7 years and did all the maintenance - mechanical and electronic - on them as well. Great machines. Stop to play-lock in less than 1/2 sec once I got the braking set up and programmed properly.Once again it's only a B77/PR99 without tape tension electronic control built for consumer market. If you want to see how they (Studer) did full blown control of all motors to achieve constant tension and one hand edit, look at the A812/A820 schematics. Really not the same thing and cost but fascinating design.
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