[QuadList] ACR-225 (was 1" Machine glue)

[Dennis Degan]

		On Feb 3, 2010, at 7:52 AM, Trevor Brown wrote:

	> The RCA color time base corrector dumps any errors it cannot cope 
with into the mono TBC.  This dump signal is called THAF.  The Mono TBC 
dumps any errors it cannot cope with into the servo this error is 
called THA.  This extend[s] the range of the small fast TBC's that can 
cope with quad errors, by operating a closed loop.  You clamp the error 
signals to mid range until the servo locks and then unclamp and it all 
stays locked.  On the TCR you have one TBC and two servo's so there is 
still a THAF loop but no THA loop, which mean the mono TBC cannot spill 
into the servo to centre itself (not a closed loop) and as a result has 
a poor range and unlocks on air.  By stand alone I meant AVR 2 style 
TBC which has a greater window and will run independent of the servo's. 
  The Helical TBC's are big window too but designed to deal with slow 
errors and so are as you say no good for quad.
 > The sharing of a TR70 signal processing with a TCR (we did not have a 
60) is called master kit and you end up with a TR70 with a small TBC 
window Which spoils its performance too.  It's a big mod and it spoils 
your reel to reel machine, which cannot operate when you are using the 
TCR, we gave up and bought an SPU (TR600) modules, not as good as the 
SPU based on TR70 modules

		I say:

Thanks for the clarification, Trevor.  You've obviously remembered more 
than I'll ever know about TCR-100 electronics!  Although I took the 
course on the machine at RCA in Camden, it was 32 years ago when I did 
so.  I haven't even SEEN a TCR since 1980 or so.

			Dennis Degan, Video Editor-Consultant-Knowledge Bank
	  					NBC Today Show, New York