First NTSC Receiver 1941
 

A question which has been lurking in the back of my mind for a long time is what was the first manufactured NTSC standard receiver?

The prewar receivers from 30 April, 1939 followed the RMA standard 441 line AM sound negative video modulation vestigial sideband video transmission. The standard 525 lines FM sound was adopted by the NTSC by April 1941 and authorized by the FCC July 1, 1941.

I have seen RCA TRK12's modified from 441 to 525 line video (change of horizontal sweep frequency from 13,230 to 15,750 Hz) and the use of slope detection from AM to FM audio demodulation. Were there any TRK12 or other receivers manufactured between April 1941 and 1945 with proper FM discriminator circuits specifically for the new NTSC Standard?

Of course Pearl Harbor in December 1941 put an effective halt on television. However Iwould have expected in the six months leading up to the US entry into WWII and prior to the unveiling of the RCA postwar 630TS an NTSC manufactured Television Receiver.

This is a good and interesting question.

You may already know that the TRK-9 and TRK-12 from 1939 also have 1940 versions called TRK-90 and TRK-120. (One main difference I know in the 120 is that its radio chassis does not have the eye tube that is in the TRK-12, but I do not know of specific TV differences if any.) Rider TV manual #1 has service information for the TRK-9, 12, 90, and 120, and if I remember right it does include two separate tuner modifications that change some or all of the frequencies of the five channels those tuners receive. One or both of the mods mention that the channels will now be 2-6 rather than 1-5, and I know there are TRK-12s that do have a decal with the new channel numbers.

I do not remember any mention of circuit modifications for FM sound (they do mention slope detection) or for the horizontal scan rate change. Also, there is definitely no mention of any TRK-120s built with FM sound circuits or 15.75 kHz horizontal sweep as standard. I also do not remember if either or both tuner modifications were from post-war or not.

What seems likely to me is that TV sets were not selling enough for manufacturers to design and release new models after the initial group of 1939 designs, other than the two 1940 RCA ones I mentioned.

It would be good to find information on TV broadcast schedules and TV set sales in the USA between 1939 and the end of 1941. Were they expanding, or stalled/shrinking?

As a TRK-12 owner I've done a fair amount of research and as I understand it the horizontal circuit can sync to 441 or 525 line in the original design from the factory with just a twist of the user horizontal hold control. Other owners have told me so, and I hope to see for my self when I recap the TV receiver chassis (last one not done) of my set later this summer.

I've heard that the slope detection on the TRK-12 worked for FM from factory without realignment too.
Those sets saw 1-2 channel frequency changes for TV stations depending on if they saw use post war.

This is a fascinating topic that I've wondered about myself before.

ISTR hearing about some rare GE prewar set that wasn't an RCA in a different cabinet that had a British CRT that I think the owner may have mentioned was built after the NTSC monochrome standard.

I'd love to hear from someone who is an authoritative source on pre-war sets on the OPs question.

Slope detection for the FM audio was far from optimum as it would lead to non linear distortion. Also optimum sound would not provide optimum video unless the alignment was touched up.

As was previously pointed out, almost all pre-war sets were manufactured in 1939 and 1940. Overall sales were much lower in 1940 so manufacturers were not willing to spend the capital to design new sets. RCA actually sent a letter out to employees on March 26 1940 offering deep discounts on existing sets. A TRK12 went from $600 to $250 while a TT5 went from $199.50 to $75.

In 1941 RCA sent a letter to all owners of their sets stating they would realign the sets for audio (slope detection) at no cost. No adjustment is needed on any pre-war set for 13,230Hz vs 15,750Hz as the horizontal controls have enough range and the width can be touched up.

GE sets were all designed by internal engineering in Schenectady and shared nothing with RCA other than purchasing RCA manufactured CRT's. GE also sourced MW series CRT's from Philips in Holland for the HM225 and HM226-7A sets which caused issues between GE and RCA resulting in RCA sending inferior CRT's to GE. (documented by the GE engineer charged with fixing the situation)

As for NTSC compliance, RCA was none to eager to jump on the FM bandwagon after having shut out Armstrong and his FM experiments at RCA only a few years earlier. Armstrong found a supporter in GE who built the first FM receivers, GM-75 in 1938 and HM-80 in 1939.

I have W.R.G.Baker's HM226-7A television that was updated for FM sound by GE engineering. The audio IF's were changed to unique non-adjustable units about 1/3 the size of the production ones while a 6AC7 Limiter and 6H6 Discriminator were added. This however appears to be a one-off.

The only NTSC compliant pre-war production set I am aware of is the GE M90 which has an unusual history. These all started life as the HM275-3A in 1939.

They were basically unchanged from the prototype GM295 except for the addition of a AM/Shortwave radio of dubious design (that's what the -3 is for in GE nomenclature, the number of tubes in the radio) containing only a single tube Conv/Osc, a single IF stage and a detector. It is assumed that since these sets were the top of the line they would most likely only be sold in and around New York and didn't need a sensitivity radio, although it's still an odd choice for the top of the line television. For comparison, the HM226-7A uses one of their standard 7 tube radio chassis with excellent performance.

For what ever reason, GE decided not to sell the HM275-3A of which 75 were built according to an engineers account. These of course were not NTSC compliant at this point.

In 1941 they decided to modify the existing HM275-3A's for NTSC adding a 6AC7 Limiter and 7K7 discriminator and rebrand them as M90's under their Musiphonic line of products. Oddly the original blueprint I have for these sets calls them HM275-3B and not M90. The M90 label on the back of the sets was hastily affixed over the existing HM275-3A label and many times parts of the HM275-3A label are visible.

The M90 sets were sold to the public so I believe this is the only NTSC compliant pre-war television sold.

Thanks I appreciated your assessment. I suppose even before Pearl Harbor, the writing was on the wall with regards to Television development. Also in 1941, the Great Depression was still lingering and it wasnt until the postwar boom and the military veterans returning home was there the impetus to proceed further.

Interesting your thought and prewar RCA's avoidance of anything to do with FM. Slope demodulation is so inferior despite the distaste for FM, I am surprised there are no pre-war RCA sets modified at the time. This implies RCA decided to take a hiatus for the duration. Although the development of the Image Orthicon camera tube was proceeding and until its debut in 1946, I think that was what tipped the balance. The iconoscope just wouldn't cut it.