Second Emerson 571 triage
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- Опубликовано: 27 мар 2024
- We took a look at my 571 and its bizarre power supply last year. Here's another that's mostly stock. Let's take a look and attempt a power up.
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Great triage video Bob, and obviously a great candidate for complete restoration!
LOL!!! The original flat-screen!
Amazing how some sets just sort of work after decades of storage, I bought a 1948 set that had last been used in 1959, apart from replacing an open smoothing cap, it just worked!
Always a great start to a restoration, when all the major parts are working to some degree.
Thanks for a great video love this channel bob your the best
Thanks. Another video uploading right now :)
Wow, that's a crazy power supply! I would think that having 5 rectifier tubes would decrease reliability somewhat, because if any one of the 5 goes bad it could affect performance. That's a very promising first power-up
Nice. Good results on first power up. Good luck with it.
That is a funky design for a voltage doubler. The thing I'd think about it is that it could still be susceptible to current hogging due to differences in rectifier tube characteristics, and thus overload a rectifier tube. I agree that it probably was also to economize on the transformer, though if the point was to add enough voltage to 117 volts to get to 125 volts, and a line-tied chassis is okay, a smaller transformer ought to suffice without incurring the bulk of an autotransformer.
That rectifier setup is crazy.
Love your comment on the amount of 1B3 tubes you have available! i Have a box of pulls in my stash of tubes. They're probably in any used lot of tubes for sale. Interesting power supply. Maybe the government had millions of 25Z6 in surplus. Good luck on this one, Bob.
Either they had an endless supply of 25Z6's, or a good deal on transformers that didn't have a 5 volt secondary. Otherwise, that's a needlessly expensive way to get B+.
Well it did work in the 1980s. For the early design with the full compliment of rectifier tubes that is something.
yardbirds with Jimmy Page !
Neat old set!
One step up from a muntz. 😅
I'm still on the fence if this television thing will catch on. I made the deal of a lifetime on a warehouse of war surplus tubes let's design a TV around them.
Bob, you're correct. All those knobs are RCA except the tuner. That tuning backplate should not be carved out so crudely at the corner of the screen bezel. The electronic design is terrible. Hardly any sync circuitry, horrible power supply. And they still put in a power transformer, though dubious. Not a good design, not even for 1948. Amazing to see a picture on it.
I think the tuner may have been replaced which explains the crude cutout and the mismatched knob. All the data I have suggests that this earlier chassis version was only shipped with a 13-channel tuner, but a 12-channel one is present. My 611 has the _newest_ version of this chassis and even it has a 13-channel tuner.
The power supply is indeed crazy on this older version but the sync circuit is great. I have the later revision chassis (which has the exact same sync circuitry) and it delivers a solid lock instantly without any trouble. What's the benefit of a more complicated circuit?
Somewhat disappointingly for me but beneficial to you, this set has the later revision of the early chassis. Other than the slight difference in the power supply I believe it's identical to your personal set with the earlier revision. The later versions are substantially different. Look at Sams 46-25 and the 571 factory manual on the ETF website, ignore Sams 76-11.
A brief summary as I understand it:
Chassis 120066: earliest version, used in your personal set. Underchassis power resistors and Split-carrier audio.
Later version (for sets after May 1948): uses ballast tube but AFAIK otherwise identical
Chassis 120086B: major change. switches to intercarrier audio and uses more miniature tubes. Different underchassis layout. Still uses 5 rectifier tubes.
Chassis 120087B-D: same but uses 4 selenium rectifiers.
The first part of the serial number is the same as the last part of the chassis number. On these sets the sticker is next to the power transformer.
Also of note, I suspect this set has had its tuner replaced. This would explain the mismatched knob and the hacked-up channel plate. The service data suggests the older versions all shipped with 13-channel tuners and _some_ of the newer versions shipped with 12-channel tuners.
Thank you for the summary. Aside from the ballast, it seems there may be some component placement/wiring differences between this and mine but it's a hard to say. Both have some old repairs that complicate matters.
It is a little tempting to disconnect the five rectifier tubes and installed some power silicon diodes underneath.
@@bandersentv If you replace the rectifier tubes with silicon diodes you'll want to disconnect the boost tap and even then you need to be mindful of voltages. Before the tubes start conducting there'd be close to 700v between B+ and B-, enough that you'd probably want more than 630v-rated capacitors in some locations. I would also suggest that all high-voltage electrolytics after the rectifier have a surge rating of at least 400v. If you keep the tube rectifiers their slow turn-on characteristics mean you can get away with the lower-voltage parts you may have already ordered.
@@eDoc2020 Good point. I wonder how they managed in the later version with selenium rectifiers?
@@bandersentv That's what I have. They're just relying on the surge rating of the capacitors. I seem to recall reading somewhere that the old capacitors have an extra 50% above working voltage for startup surges and this makes the 250v capacitors just good enough.
If I'm not mistaken there's significantly more leakage current when running at surge voltage and this causes self-heating. With their greater mass the old caps can handle more self-heating before they get too hot.
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LOST IN SPACE !
You never mention the power factor of the A/C going into a television like that I would imagine that it's a mix of resistive and inductive loads
5 dollars for such a tube doesn't sound too bad. After all the sellers have to pay storage and packaging costs and such.
If you buy a hundred at once, I would think a discount should be possible.
Electrocution, fire, CRT implosion,, x-ray and carcinogenic heavy-metals hazards -all combined into one cheaply-constructed old corroded package. I’ll pass….
Be careful man 🤞
It's what I do. There are no xrays at these voltage. Really no fire risk. Electrocution? There's that risk with anything that plugs into an outlet. Heavy metals? Don't lick your fingers. What corrosion? Cheap? Not really. Some bad old repairs maybe