[QuadList] Dropout Compensators

[WVGO]

As far as TR-70 DOCs go, the 70As and 70B that I have here all have the 
two module DOC. 
The  main  dropout compensator module in these machines has a metal tag 
attached with the MI number, that is reminescent of a 3M tag in it's 
colors and font, although there is no "3M" printed on any of the 
boards.  This module also differs substantially in construction from 
typical RCA module assemblies, in that printed circuit boards are used 
and not the usual point to point wiring that RCA used.  So I would 
concur that they were built by someone else, probably 3M.  The other 
module, the "dropout proc" in this pair is definitely RCA built though 
and resembles every other module in the machine in it's construction.  
I'll check the diagram manuals when I get a chance to see if there is 
any notation about 3M there.
The 70Cs that I have all have the single module DOC....also again 
appearing with circuit board construction and even some integrated 
circuits.  The construction and metal tags on these single module units 
also appear to be made by the same company (3M) as the earlier TR-70 ones.
There was apparently a lot of evolution happening in the DOC in the time 
frame of TR70 production.  The circuitry and layouts differ considerably 
from one generation to the next. 
Guy

www.GuySpiller.com




>
> *Sent:* Friday, May 01, 2009 10:06 AM
> *To:* quadlist at quadvideotapegroup.com
> *Subject:* [QuadList] Dropout Compensator
>
>  
>
> Maybe someone can answer the question about who made the drop out units. 
>
>  
>
> Ampex had the unit that was a plug in board for the VR-1200 series.  
> This was made by them.  It did not have the color phase inversion so 
> you might see the replacement.
>
>  
>
> 3M Mimcom built the three rack unit that was installed in the 
> VR-1200's that I had.  It had the color inversion and even had a test 
> generator for it.
>
>  
>
> RCA had a module that plugged into the TR series units. 
>
>  
>
> I heard a rumor that 3M built the units for RCA.  Does anyone know?  
> Was this done only for the later machines?  The early ones that I 
> have information for does not have the color inversion.  The early 
> ones were two modules wide.  The later ones that were for the TR-60 
> and TR-70 was a single modules.  It had a switch on the front that 
> stated off, mono, and color.  There was also a color phase screwdriver 
> pot on the front.  This is the one that I had heard was built by 3M. 
>
>  
>
> Chris Hill
>
>  
>
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