Wonderful score today

[Steve McVoy]

Prewar sets with AM detectors work just fine with a standard RF modulator using slope detection. That is how we operate them at the museum.

[tubesrule]

Congratulations Dave! These sets are relatively easy to restore and perform well.

Originally Posted by David Roper

Far from absolutely necessary, as the success of slope detection with the unmodified restored sets at the ETF has proven.

Dave,
The problem I've run into with slope detection, while it does work it requires the audio carrier to be centered right on the slope, meaning any slight drift in the LO and the audio moves off the slope and drops out. The RCA LO design seems to be a bit more stable than the GE, but they require constant touching up of the fine tuning the entire time you run them. The other problem is modern modulators set the audio carrier -16dB from the video whereas it was originally set to -6dB.
I've given up on slope detection since my converters are capable of AM and FM audio modulation and variable carrier level. Driving these sets with a -6dB AM signal is night and day from using slope detection. As a bonus I program the converter for 441 line and the original carrier frequencies not that this is required.

Darryl

Edit:
Steve,
You posted your reply while I was writing mine. How much drift do you notice in the sets, especially the GE's when operating them? What I found was I had to constantly touch up the fine tuning to keep the audio on the slope. With AM modulation and the fine tuning having such a limited range on these sets, it pretty much doesn't matter and the sound always comes through strong with less distortion.

[Steve McVoy]

Darryl,

I find the Andrea and RCA sets are fairly stable.

You are right about the aural carrier being -16 db relative to the visual. That means you have to hit the sets with a lot of RF to get good audio level. I typically hit them with about +25 dBmv.

Of course one of your modulators with AM audio would be a much better solution.

[tubesrule]

Steve,
That's definitely a higher RF level than I was using which probably accounts for the difference. I'll have to check that out in May.

Darryl

[bgadow]

Regarding restore vs. keep as-is, if the crt is good (or a good one can be obtained) I would do a very careful restoration including neat restuffing of the caps, etc. Just speaking for myself, if I couldn't use it, I wouldn't care to own it.

[David Roper]

Originally Posted by tubesrule

The problem I've run into with slope detection, while it does work it requires the audio carrier to be centered right on the slope, meaning any slight drift in the LO and the audio moves off the slope and drops out. The RCA LO design seems to be a bit more stable than the GE, but they require constant touching up of the fine tuning the entire time you run them. The other problem is modern modulators set the audio carrier -16dB from the video whereas it was originally set to -6dB.
I've given up on slope detection since my converters are capable of AM and FM audio modulation and variable carrier level. Driving these sets with a -6dB AM signal is night and day from using slope detection. As a bonus I program the converter for 441 line and the original carrier frequencies not that this is required.

Almost five years after the fact I guess I'm still not used to the obsolescence of NTSC and the reality that all analog sets require some kind of converter now. And yet I did deliberately use past tense because I wasn't certain that the museum was still running the prewar sets with an ordinary modulator rather than one of your converters.

[earlyfilm]

For the two Steve's, there are minor differences noted between apparent factory schematic at

http://earlytelevision.org/tv_schematic_diagrams.html

and the Rider one at

http://bs.cyty.com/menschen/e-etzold...andrea/1f5.htm

with the first one seemingly the older version of the set.

My thoughts when seeing Dave S's first post yesterday was the thread was going to quickly turn to speculation on whether or not that this set had been converted to NTSC picture standards, or was out of service by 1941. Now that we are up to post 37, I'll just casually mention this question.

441 or 525? How many installed channels does the tuner have?

Oh, and Steve S, congratulations on the find and I can hear that set screaming, "Get me out of the car!!!"

Jas.

[cwmoser]

Originally Posted by Dave S

WA2ISE: that would probably be beyond my "shade-tree engineer" capabilities, although I'm certain all of you guys could and would talk me through such a project.

I'm currently discussing the merits of restoring such a set vs. just leaving it in original condition with a fellow collector. I wonder if anyone wants to jump in on that discussion? Maybe it would be appropriate to start a new thread for that.

-- Dave

Dave, when you do start your restoration, start a thread and post your
pictures, thoughts, and progress. I think a lot of us would like to follow
with you when you do the restoration.

Carl

[Steve McVoy]

James, the only difference between the 441 and 525 line standards is the horizontal scanning frequency, and all the sets have plenty of range on the controls to adjust to either. So no modification is needed.

This set was made for 2+ years and there are several versions. Some used 6V6s and some used 6AG7s as video outputs. Some had 2 channel tuners and some had 3.

Dave's set may be missing its tuner, since the shaft is gone.

[Dave S]

There appears to be something in the tuner position, but I won't know for sure what it is until I get to take a closer look.

Had a really nice long talk with Chuck A. last night and he said that in his experience most prewar sets had been converted to the postwar standard, which would make sense. I got the impression that he was talking about more than just tweaking the horizontal oscillator frequency, but maybe not. He also said that (again, in his experience) many prewar sets had new tuners installed at some point soon after the war.

Carl: I promise to document the daylights out of anything done on this set. This set is even more significant than my TRK-120, which is much more of a basket case. I'm currently in the middle of working on a nothing-special radio for a neighbor and I take a lot of pictures even of something like that: http://sdrv.ms/1j3oR0X.

-- Dave

[Steve McVoy]

The two mods that I've seen in prewar sets are 1) a 12 channel tuner, and 2) a FM audio detector.

I've never seen a 1-F-5 with a 12 channel tuner, though it would have been possible to do.

Also, I've never seen a FM detector in one either.

Most likely your set has the original circuits.

[earlyfilm]

Originally Posted by Steve McVoy

James, the only difference between the 441 and 525 line standards is the horizontal scanning frequency, and all the sets have plenty of range on the controls to adjust to either. So no modification is needed.

Since the Andrea, and in fact most electrically deflected sets, don't use the horizontal signal for HV, this set would have been relatively easy to convert.

I have no experience converting 441/60i to 525/60i, but a little over 50 years ago I did convert a 405/72i to 525/60i and it was much harder to do than I had expected. The worst part was, at the time, I was unable to determine the exact specifications of the set. Not having an accurate frequency standard, nor a scope, I used an actual TV signal and a little red-neck engineering. I was so far off on horizontal that I had no idea how far I was off -- all that I knew was it was way too high, but I could see the wide vertical signal rolling, so I first converted the vertical to 60i and then was able to see the horizontal well enough to bring it in, but when I did, the drop in B Boost was enough that it messed up the vertical again, and so I had to redo the vertical.

When I got it on speed the V & H size and linearity controls were out-of-range. If memory serves me correctly, I had to change some capacitors by over 50% and adjust resistance.

Jas.

[tubesrule]

Originally Posted by earlyfilm

Since the Andrea, and in fact most electrically deflected sets, don't use the horizontal signal for HV, this set would have been relatively easy to convert.

Jas.

James,
All pre-war televisions, electrostatic and electromagnetic, except the German E1 used brute force HV developed right from the mains. Only the E1 used a flyback. There is no issue with changing the horizontal frequency on any of these pre-war sets. I have run my 12" electromagnetic RR359 from 240 through 819 lines with no changes to the circuitry, just adjusting the coarse horizontal control.

Darryl

[wa2ise]

Originally Posted by tubesrule

I have run my 12" electromagnetic RR359 from 240 through 819 lines with no changes to the circuitry, just adjusting the coarse horizontal control.

Darryl

Thought comes to mind if that set could handle 1080i or 720p. B&W HDTV, use the luma jack. Though 720p would be nearly the same as 1440i, which seems too much a stretch beyond 819i.

[ChuckA]

Originally Posted by earlyfilm

For the two Steve's, there are minor differences noted between apparent factory schematic at
http://earlytelevision.org/tv_schematic_diagrams.html
and the Rider one at
http://bs.cyty.com/menschen/e-etzold...andrea/1f5.htm
with the first one seemingly the older version of the set.

My thoughts when seeing Dave S's first post yesterday was the thread was going to quickly turn to speculation on whether or not that this set had been converted to NTSC picture standards, or was out of service by 1941. Now that we are up to post 37, I'll just casually mention this question.
441 or 525? How many installed channels does the tuner have?
Jas.

In Nov 1941 Andrea put out an upgrade kit and 3 page instruction sheet to convert the 1F5 to the new standards. It included new antenna & oscillator coils and a new sound IF transformer in addition to a few new resistors. Reading through the instructions the tuner coils were changed to allow the tuner to receive the "old" new channel 2 at 51.25MHz & new Channel 3 at 61.25MHz.
The conversion did not add an FM detector to the audio circuits, the new sound IF transformer allowed the set to be tuned easily for slope detection for the new audio standard FM.
The instructions describe tuning the audio first to 8.25MHz and final adjustment is peaking the audio at 8.15MHz

Also included was an extension shaft and knob to make the sound sensitivity (fine tuning) control accessible from the outside.

So if a set has the FT control knob on the right side of the cabinet there's a good chance it has the mods.



Chuck