Prototype set is here

[JBL_1]

Originally Posted by ChrisW6ATV

I wonder if it would be feasible to connect either a sweep generator plus scope, or a spectrum analyzer with tracking generator, to various circuits in the chassis to figure out their resonant frequencies and bandwidths as currently tuned.

Sweeping the bandpass amplifier is a great idea! The response may not be peaked at the subcarrier. The peak could be staggered to make up for any roll off in the IF or bandpass/lowpass filtering.

But the information still could be usefull if you looked at the overall video response of the chassis.

[Penthode]

Please find attached two papers, both from Hazeltine. The first one on general color receiver design pertains to CPA only. The last page has a nearly full CPA demodulator. Note the demodulator does not use a crystal! The design is a straight reactance controlled Colpitts oscillator. This is interesting in as much as it is expected to keep sync over the entire line from onlyeight cycles of gated burst reference! Note the color hold control- if there is no crystal on this prototype I would trust there is a color hold control on the front!

The second Hazeltine paper is by Bernard Loughlin. His name conjures up a lot of early NTSC development. His 1966 paper is timed with the launch of PAL in Europe. It is interesting to read his reflections since the NTSC did much of the earliest PAL and PAF work.

I find his interesting note in passing on the second page (numbered 154) under the heading Stationary Axis. Mr Loughlin refers to his October 1951 IRE paper whereby the R-Y axis was stationary and the B-Y axis switched or inverted 180 degrees. He goes on to state the 1952 PAF NTSC testing made the B-Y axis stationary and the R-Y axis switched. In PAL, the R-Y switches at line rate.

I would be interested to see how closely the prototype receiver follows the Hazeltine decoder.

[Pete Deksnis]

It's a minor thing, but it made me recall the crystal socket that was discovered last Saturday. Went back to my photos and confirmed that the subcarrier oscillator was, in fact, built on a removable chassis. The tube is a 6U8, one RCA used in this circuit in pre CTC2 chassis before introducing the 6AN8. Unfortunately, the name of the builder of this chassis is no closer to being known. The crystal in this photo was from a CTC2.

Pete

[old_tv_nut]

Originally Posted by Pete Deksnis

Went back to my photos and confirmed that the subcarrier oscillator was, in fact, built on a removable chassis. Pete

Is there a chance that some markings are hidden and would be visible if the subchassis is removed?

[JBL_1]

You haven't been around long enough;-). There are way too many
of those projection sets around and I bet there are few collectors
that have just the chassis to use for flybacks and hard to find parts.
It is very unlikely that any have used the power supply chassis. I think
would be a very good fit.

[Pete Deksnis]

Originally Posted by old_tv_nut

Is there a chance that some markings are hidden and would be visible if the subchassis is removed?

While I didn't take under-chassis photos, from what I recall, your idea could probably be tested without completely removing that assembly; there seem to be only four screws in the photo associated with the chassis.

I thought perhaps the separate chassis was for flexibility during engineering design and testing.

I'd of course love to work on the chassis, but there are no current plans to do so at this time.

Pete

[miniman82]

Originally Posted by Penthode

if there is no crystal on this prototype I would trust there is a color hold control on the front!

Perhaps I should have been more clear:

There was no crystal INSTALLED, though there is a SOCKET for one.