1936 RCA RR-359B Restoration

[Penthode]

Thanks Bob. That appears to be the missing link.

So the transition includes from 1934 thru early 1936 343 lines with a 4 MHz channel and 2.25MHz carrier spacing. For the July 1936 343 line first public demonstration, RCA engineers moved to the 6 MHz channel where it was first used with double sideband video and a 3.25MHz carrier spacing.

The question remains when the 4.5MHz carrier spacings were adopted. The RCA paper said the first time it was applied to the transmitter was March 1939 which agrees with another paper I read indicating VSB was first implemented just prior to the NY World's Fair in April 1939.

Logically VSB was probably first tested on a 3.25MHz carrier spacing channel for direct comparison with 3.25MHz carrier spacing full double sideband. VSB 3.25MHz spacing would not entirely fill the 6MHz channel and so this would suggest by March 1939 4.5MHz carrier spacing was introduced.

[tubesrule]

Originally Posted by Penthode

So the transition includes from 1934 thru early 1936 343 lines with a 4 MHz channel and 2.25MHz carrier spacing. For the July 1936 343 line first public demonstration, RCA engineers moved to the 6 MHz channel where it was first used with double sideband video and a 3.25MHz carrier spacing.

Last time in the hopes that anyone reading this in the future will not have bad information. The pages from Television II clearly show the 343 was 2.25MHz spacing and the 441 was 3.25MHz spacing.

NO, as all the actual dated original documents that have been presented here have shown, the 343 line field test was NEVER at 3.25MHz carrier spacing. The RF Alignment manual I copied showed they were aligning the 343 line RR-359 sets to 2.25MHz in November of 1936. I fail to understand your instance to the contrary without ever providing a single piece of original documentation of support.

[Penthode]

Originally Posted by tubesrule

Last time in the hopes that anyone reading this in the future will not have bad information. The pages from Television II clearly show the 343 was 2.25MHz spacing and the 441 was 3.25MHz spacing.

NO, as all the actual dated original documents that have been presented here have shown, the 343 line field test was NEVER at 3.25MHz carrier spacing. The RF Alignment manual I copied showed they were aligning the 343 line RR-359 sets to 2.25MHz in November of 1936. I fail to understand your instance to the contrary without ever providing a single piece of original documentation of support.

I went back to read the Joffieffe presentation to the FCC on June 15, 1936. In it Jollieffe asserts a resolution around 440 lines and the need for a 6 MHz channel. However he explains that the construction of the transmitter for the July 1936 first television demonstration was 343 line and a 2.25MHz carrier spacing.

So the impeding move to 441 line was pending, I have not found a date for it's first public demonstration but i suspect it must have been late 1936 or early 1937.

So for the record, I fully agree with your statement and appreciate your dilligent clarification.

[Penthode]

Originally Posted by tubesrule

If only Holmes and Lev had read the Television books before writing the RF Alignment engineering note for the RC-199 (RR-359A main chassis) dated June 22, 1936

The RC-199 (RR-359A) was 2.25Mhz spacing, the initial change to RC-199B (RR-359B) was 3.25MHz, the final modifications to RC-199B was 4.5MHz.

What is interesting is the figure 2 attachment showed the video carrier on the trailing slope of the response curve. That means the RCA engineers realized by June 1936 that economy on TV receiver design could be accomplished with less tubes by using a single sideband. Jollieffe alluded to this on his presentation the the FCC on June 15, 1936 when he suggested if a single sideband could be employed in a 6MHz channel video transmission, greater detail with less bandwidth could be employed. This suggests the RCA engineers by June 1936 knew of the possibility of single sideband delivery but had not yet figured out vestigial sideband operation. That would take another couple of years until 1939!

[Mr Hoover]

I'm surprised they didn't use RCA acorn tubes/valves in the
tuner,these were developed by RCA and available by the mid
1930's.Performance would have been way better.954 955 956
series
https://en.wikipedia.org/wiki/955_acorn_triode

[Penthode]

Originally Posted by Mr Hoover

I'm surprised they didn't use RCA acorn tubes/valves in the
tuner,these were developed by RCA and available by the mid
1930's.Performance would have been way better.954 955 956
series
https://en.wikipedia.org/wiki/955_acorn_triode

I agree. I have an RCA frequency calibrator from 1935 which used the acorn triode 955. And a 1939 Hallicrafters S27 UHF radio which uses the pentodes. Maybe 1935/36 was a bit too early?

[bandersen]

I decided to partially reassemble the set while I focus on the power unit chassis down in the workshop.




I need to remove a bunch of screws and rotate that screen mask 90 degress.




Also picked up an RCA highball glass from the 1939 New York world's fair to celebrate when I get it working.


A heavy duty turntable makes it much easier to manipulate the very heavy PUI chassis on the workbench.

[bgadow]

A real eye towards serviceability the way that chassis is mounted. Now, remember, you're only allowed to use your RCA equipment when testing this. Have to keep it real.

That's a great decal. I wonder if anybody has fashioned a reproduction yet?

[tubesrule]

I have water slides of the "RCA Television" decals I made on my Alps printer using gold foil. I'll send Bob some.

(artifacts are not in original)

[bandersen]

Thank you. I do plan on having the cabinet repaired and refinished.

I started on the PU by checking the resistance of all the transformers and filter chokes.
All appear to be OK, except for the replacement HV transformer. The HV secondary is open.

Out it goes. I wasn't happy with the way it was crammed in there anyway.


I also removed the added 2.5 volt filament transformer.


You can see the scars where openings were enlarged for the TRK transformer.


I'll be replacing them with two Triad filament and a neon sign transformer.




I'd been tipped off that an RCA radio from the 30s might have a suitable shell.
That trigger a memory that I had parted out a rough 1930 Radiola 80 years ago.
I went hunting in the garage and sure enough I still had the power chassis.
Bingo! The largest box is exactly the right size!
The three new transformers should fit nicely inside and I can restore the wiring to the original configuration.
It will also hide the cuts made in the chassis.


I need to bake out the contents and strip the brown paint.
A few taps and it will drop into place.


While I wait for new transformers to arrive, I can start on restuffing this box capacitor.

[Chris K]

Mouse chews there? Damn rodents!

[bandersen]

Looks like it. That's about as far as they got though thank goodness. No rodent urine corrosion to deal with.

Moving on to the bleeder resistor board. It's warper and cracked. Seems they added a ceramic standoff during the "B" upgrade which put stress on the board.
You can see the two holes where it used to have a metal support like on the other side
I'll fabricate replica dogbones using this technique and repair/replace the phenolic board

[Chris K]

I guess you want to be as authentic as possible, but I wonder if, since you're going to use modern resistors in handmade dogbone shells anyway, why not keep the original resistors in place on the phenolic board but take them out of circuit while mounting the new resistors in circuit hidden on the back of the board? The original resistors could be kept for display on the front while modern resistors do the actual work on the back. Would save the time and effort of making new/old looking resistors and you'd keep the originals.

[bandersen]

Some transformers have arrived.
Both are well made and should fit inside the salvaged transformer box.
Not sure if I can fit another Triad filament transformer in there though. If not, I'll hunt around for a smaller one. Don't need 10A for the 2X2 filament.

[Dave S]

Bob, the story about the “001073” stamped on the chassis is one of those absolutely charming coincidences that always make me smile.

And Daryl, I could be wrong but although Ray Kell was surely often the smartest guy in the room, I don’t believe he was a PhD.