Prototype set is here

[Steve McVoy]

You can follow the restoration here:

http://www.earlytelevision.org/rca_cpa_restoration.html

[miniman82]

Here is the series of pictures from the convention, where we mounted the proto CRT into Bob D's CT-100 donor cabinet and attempted to run it with a CT-100 chassis.


Begin with a spare CT-100 cabinet.




Remove factory CRT mask.



Prefabbed proto CRT 'conversion' mask, plexiglass hasn't been installed yet.



Place conversion mask in cabinet.



Install plexiglass into front of conversion mask, secure with self tapping wood screws.



View from the rear of the cabinet.

[miniman82]

Install proto CRT into custom mask. This required the use of a CT-100 support ring, held in place by support rods that were fabbed on site because the factory ones were far too short. These were Bob Galanter's idea, made from threaded rod that we cut to size. We then heated the ends with Bob's mapp gas torch to bend J-hooks into the end so they would fit into the U-hooks in the CT-100 cabinet.



Front view, with CRT in place.



Rear view, with CRT installed.




CRT being powered by the CT-100 at the ETF, which had unreasonably low HV (first attempt, on Friday).



Attempt #2 on Saturday, with CRT being powered by the Model 5 chassis. The Model 5 worked a lot better than the CT-100, but horizontal frequency tended to drift out of lock and we weren't able to get it back. Various things were tried in hopes of getting the Model 5 chassis repaired including replacement of caps and the horizontal frequency transformer, but were unsuccessful.



On Sunday we tried Bob's CT-100 chassis, but in the end we discovered that there is an issue with how much current the convergence electrode on the proto CRT is drawing out of the HV divider string in the chassis, which plays hell with the HV regulation. I will soon be modifying my CT-100 chassis so that the HV pot is no longer at the end of the divider string, but rather on the B+Boost line. This will ensure that HV remains steady, so convergence voltage is not chasing anode voltage anymore. Between this and some different value divider resistors (I bought a pair of 100 and 25 meg to try), I am confident I will at last be able to converge the proto CRT and get some decent screen shots. By the end of the day on Sunday we were all pretty tired...

[tubesrule]

Nik,
I meant to ask you at the convention, but to determine if this is a fault with the proto crt or by design, how is the convergence voltage derived on the proto chassis?

Darryl