[QuadList] TRT Headwheel Pnl-TRT nightmares/TR-70/TCR headwheel tip

[Ted Langdell]

Hi, Phillip,

Thanks much for the historical info and repair tip.   We have a few  
TR-70 owners on the list who might benefit from the Gyptol removal, if  
it's not already gone.

Do you happen to remember where the final seven TCR's were headed? (A  
long shot, but had to ask. : )

Ted.


On Dec 22, 2008, at 8:50 AM, Phillip G. Shaw wrote:

> This memory has invoked my nightmares of the TRT Tube modulator. The  
> matching/seasoning of tubes to settle that sucker down took days and  
> then it would run for >3 months unless some fool changed a tube. The  
> Servo Amps, seldom a problem but regular application of the  
> traditional rubber hammer in tool kits (arcing gas tubes) How many  
> times has someone asked you what that hammer was for?..We have come  
> a long way baby!
>
> I think the Evolution (State of the Art) of Videotape best explains  
> the head wheel transition. Ball bearings & brushes worked just fine  
> in that era
>
> A) Low Band Mono TRT1B & the color version TRT-!C Tube era with the  
> first RCA Transistor Proc-amp  (Sync & Video level) The picture in  
> advert is a TRT-!B showing only 3 racks of the 5 rack machine. The  
> TRT-1C was 7 racks
>
> B) The TR-3/4, TR5, TR22 were transistor versions using Geranium  
> 2N404 & 2N585. The head wheel Vacuum was part of the Blower Assembly  
> (Noisy bugger) these machines where Low Band Mono and Color and  
> upgrading kits may have been offered but not the best option. RCA  
> did switch head panel pickup to transformer but Air bearings?? I  
> don’t think that would have improved performance of those Machines,  
> but RCA would sell any upgrade & have a field guy install it.
>
> NOTE:  7.5 IPS was not a normal Broadcast feature (Bandwidth). I  
> think some 8 head military data versions played in those regions.  
> The features like “Pilot tone” weren’t popular in the US but found  
> some use in PAL applications. I may someday tell the story of   
> “removing” Pilot Tone from TR600’s in Australia
>
> C) The TR60/61, TR70  The silicon era 2n4400 series brought in HI- 
> band & Air Bearings & the Venturi for head wheel guide Vacuum. Most  
> Stations supplied Hi pressure Air from a central system. The drop  
> out Comp, and decent TBC
>
> My memory also triggered a TIP for those PPL who restore RCA TR 70C  
> & TCR-100 Machines. The Turnaround Tape Guide (below the supply TT  
> on the 70C and after the Capstan on the TCR100) has one of those  
> stupid factory-induced flaws. The assembly required that the threads  
> of the screw attaching the Vertical post (shaft) to the Boss have a  
> drop of Gyptol (thread Lock)
> The brilliant factory Gorilla (same guy for Years) assembling those  
> parts filled the Boss with Gyptol, this resulted in the Post been  
> effectively mounted on a flexible base (rubber like). The Fix is to  
> remove the shaft & clean the mounting area of all Gyptol, apply lock  
> tight to threads and reassemble. The tape path will then be  
> absolutely perfect. This problem was finally found during Customer  
> checkout of the final 7 TCR100's built & sold, it was the end of  
> Shimming Capstans and delaying Cue detection.
>
> I would hazard a guess that 99 % of EOT tape damage & Operational  
> miscue faults (TRC100) were due to this fault.
>
>
> Phillip G. Shaw
>
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Ted Langdell
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