Nothing Major
 

UPDATE, SEPTEMBER 13, 2018
Nothing Major.
From Mike: I hooked up a variac to the chassis a couple of days ago and started it at 25 volts. Then about 5 minutes later I set it to 50 volts and watched the power supply tubes start conducting. They are a set of 5U4’s and there are 3 of them for the different voltages that form the power supply. The purpose of this exercise is to determine the exact running voltages that were originally designed in to the system using the 5U4 vacuum tubes. I got the voltage up to the nominal 120 VAC after many small steps and I got smoke from one of the resistors in the power supply. NOT a surprise at all. The reason for the smoke is an “open” capacitor in the power supply section of the circuitry. As it turns out, Westinghouse made this chassis such that the “power supply” is not limited to the chassis below in the cabinet. That chassis is only the first stages of the supply, which is rectification and “preliminary” filtering of the pulsating DC that is created from the rectifier tubes. There are a number of places in the chassis where they placed “redundancy” filtering to make sure that he DC was always pure everywhere in the system. I will be doing a lot of re-capping as a result of diagnostics in an effort to methodically bring this thing back to life. Once I determine what the “actual” operating voltages are, I will be installing solid state rectifiers in place of the 5U4’s and then applying resistance values in the system to reproduce the proper and “original” DC supply values. This placing of resistance values is necessary due to the fact that the solid state rectifiers are much more efficient than the original 5U4’s that are very inefficient by comparison.

I just placed a very large order for capacitors so I can press on to the next phases.

Regards, Mike.
Author: No photos on this one.

UPDATE, SEPTEMBER 14, 2018
I live in a retirement community which has its own wood and metal shop. Today friends helped move the Westinghouse cabinet and we drove it to the wood shop.

https://visions4netjournal.com/wp-co...C5576C921.jpeg

https://visions4netjournal.com/wp-co...449DA144F.jpeg

Make sure to keep it under watch so no old ladies talk their husband into making it into a book case...

Will do, and my wife said “not another one?!”

Lol.

Just curious as o the reason to replace the 5U4.s

Perhaps the power trans runs hot or is a common failure point...That is the only reason I ever switch from tube to SS rectification (except for 6X5s which I have no faith in).

I’m the owner of this set, but Mike who is far more experienced then myself is doing the chassis restoration.

Quoting Mike: “By doing these modifications it not only eliminates vacuum tube heat, it also eliminates a lot of unnecessary wiring that has the potential to cause arcing which of course is very undesirable.”

He said the wiring in the area is in poor shape.

It will also give you a stiffer(lower impedance) supply rail, which helps with voltage regulation when picture content changes. On the down side solid state devices are less resilient to voltage spikes. In heavy duty audio applications it's common to see 2 or 3 diodes placed in series to lessen the chance of a melt down if one shorts.

We need two more.

https://visions4netjournal.com/wp-co...A61C48BCA7.png

As long as the chassis is out, would you mind measuring the depth of the white screen mask, as in how deep it extends?

The one on my H840CK15 is missing, and I'm going to try to construct a duplicate.

When I return to the shop, I’ll measure the depth.

UPDATE, SEPTEMBER 24, 2018, Day 55

Greetings Marshall. I have recapped the main power supply and verified the design voltages as they are at this time. They will likely be lower during later tests since I have the sweep circuits disabled for the preliminary testing. For the foreseeable future, and maybe permanently, I will be leaving the original design in place with the 5U4 tubes. We will see how that goes later. OK, now for the pictures.

Picture #1 shows a couple of caps replaced but except for that, the chassis is as I received it. Mostly "untouched" which is how I like to get them. These caps were actually broken off at the terminals so I went ahead and replaced them. They can be seen as orange and brown components at the lower left.
Picture #2 is the main power supply chassis before re-capping.
Picture #3 is the main power supply chassis after re-capping.
Picture #4 shows my oscilloscope screen showing the waveform of the grid drive to the Horizontal Output Tubes (6BG6's).

This tells me that the horizontal oscillator is running and the drive signal to those tubes is good even before recapping. This signal on the scope is about 200V P-P and the Photofact refers it to be 150 V P-P. Given the fact that most of the running voltages are a bit high right now because I have the main power to the sweep circuits disabled, it is expected that the signal would be a bit high. This is good at this point.

This step is important because it means now, that I can do some testing of the flyback transformer. It won't tell me everything about it, but I will tell me a lot.

Mike.

Link for full size images: https://visions4netjournal.com/westi...-carousel-6116

https://visions4netjournal.com/wp-co...978F2F598D.png

The flybacks on the 15 inchers don't seem to be terribly failure prone. I would reinstall the jug at this point and try to get HV, horizontal deflection, vertical deflection, even in a brief test, and a quick check of the convergence circuitry and CRT itself before going any further. My 2 cents...

There's little sense in continued restoration efforts if critical parts are dead. I don't like the test results of the 15GP22 at all...

The dynamic convergence transformer is T-701. It needs to be replaced with a Folsom reproduction ASAP, before you damage pots in the focus circuit.

Thanks. Mike wanted to know if it was the T-701. I think I have John’s email.

I'd be surprised if John has any left; I think my friend Ed got the last one about a year and a half ago as a precautionary measure.

My cabinet is home now and miniman82 is doing the complete restoration on my chassis. I don't have a good 15GP22, but at this point I'm thinking out a plan :)

Good luck with it. Maybe we can compare notes. Nice Marantz. I have a Model 20.

The mask is so large, it could accommodate a larger CRT.

The 21AXP22 in our 21CT55 tested like this.

https://visions4netjournal.com/wp-co...927771187.jpeg

These figures are about the same as the test on 15GP22.

As we have posted on another thread, the 21AXP22 puts out a decent image despite the tired CRT. I wonder what criteria was used by the ETF. The CRT was described “good” and “excellent” prior to the auction. Fingers crossed.

That 21AXP22 is definitely tired, and according to your own post, the green gun on the 15GP22 is even lower than the 0.8 reading you're getting on all the 21AXP22 guns.

Also keep in mind that for sufficient brightness, you'll have to draw more cathode current from the 15GP22 cathode as it runs a lower ultor voltage than the 21AXP22 does (or should) in the 21-CT-55. 19.5 kV for the CT-100 versus 25 kV for the 21-CT-55. The difference in apparent brightness with the two different ultor voltages will be not be negligible.

At the very least I would expect poor tracking, and quite possibly insufficient green. I suppose your saving grace here is that the weakest gun is the green gun. If it were red, you'd be in worse shape...

I too am curious as to what happened here as far as testing goes. Your results certainly don't look "excellent". I don't doubt Steve's integrity. Perhaps your tester needs looking at? Do you have an extremely strong like new tube to compare with?

Personally, I have limited faith in the ETFs CRT tests. I've had "excellent" tubes test significantly lower than advertised at home, and 'bad' tubes that were good but lightly asleep and could have been confirmed good with a bit of patience...

I'm at the point where I rather test it myself before bidding my top dollar than trust the accuracy of the posted info.

My guess they either have an iffy tester, an iffy operator, are taking consigner's word for CRT health or some combination thereof.

I think different measuring devices will give different results. Fingers crossed for good results. We have a way to go. Going into these old sets and restorations is taking a leap of faith. We are 2000 miles from the ETF. We inquired prior to the auction, did our due diligence and hope for the best. There are no guarantees, go big, use our best judgment and hope to be rewarded with a sweet set.

About the convergence transformer that needs to be replaced, is the convergence transformer for the Westinghouse the same as that of the other early color chassis with 15GP22 CRT?

I don't know. I’m assuming no. Westinghouse did not necessarily follow RCA with their designs. I contacted John.

The part is exactly the same as that used on the RCA CT-100. Westinghouse had to source the CRT, along with the yoke, convergence hardware, etc, from RCA.

IIRC at the dawn of radio RCA was formed as a patent pool/consumer radio products division between GE and Westinghouse...There was probably still some corporate friendship between them at the time.

I don't believe the relationship between RCA and Westinghouse really had much to do with it. In fact, I recall reading that David Sarnoff was annoyed that Westinghouse had beat RCA to the punch with the H840CK15. Not that it really mattered; nobody was buying color sets anyway.

I think this is more an issue of the ONLY tube being available for Westinghouse to start constructing color sets with was the RCA 15GP22, and thus some hardware would have to be the same among all of the 15 inch color sets.

Before someone mentions the CBS 15HP22 as an option that Westinghouse could have explored for the H840CK15, those tubes appear to have been engineering samples only, though there is evidence that one of the 15HP22s at the museum was installed in a stock Westinghouse set. I have to wonder, if CBS had placed the 15HP22 into production in the same manner that RCA did the 15GP22, would manufacturers have adopted it right away and abandon the RCA tube? I think it's safe to hazard a guess of "absolutely" given how eager they were to adopt the 19VP22 and 21AXP22, albeit probably more for reasons of size.

I think it's also rather telling that Westinghouse rolled out a 19 inch model rather quickly, as did Motorola, abandoning the RCA tube for the CBS tube. Then, Westinghouse utilized the 22EP22 in 1957, which I assume has some relationship to the CBS rectangular tube, before finally moving back to the RCA color tubes with a short-lived model in '57 or '58 using the 21CYP22.

UPDATE, OCTOBER 2, 2018
Hi Marshall. I spent some time this evening working on the distressed wiring in the High Voltage cage. The purpose of the “wiring fix” is to allow me to test the circuit as designed before I make any modifications during the restoration process. The wiring fix involved “putting back” some of the wires that had simply fallen off of places from age and from the “trip”. Anyway, I am now able to confirm that the flyback is “alive” at least to the point of generating High Voltage. I got 20 KV on the final anode lead with the regulation tube disconnected. Obviously this is a critical thing to verify early on in the restoration process. It is now time to test and replace tubes and then look at a bunch of other signals with the oscilloscope as we proceed. It is also time to start replacing a lot more capacitors. At some point, probably very soon in the process, I will return to the High Voltage section and do some more work there. But this test verifies a lot of components like the “doorknob” capacitors and insulators in the High Voltage section.
YAY!!
Mike
Author: Great news!

Link: https://visions4netjournal.com/westinghouse/

Hi Mike and VK members,

Great news. I think the nominal ultor voltage for this set is 19.5 KV?

I’m told the convergence transformer in question is identical to RCA.

Best,

Marshall

Yes, that is what the nominal HV should be at the 2nd anode. The actual HV generated should be, I think, more like 22.5kv or more. This is due to the function of the 6BK4 Shunt Regulator that keeps the regulated voltage at the 2nd anode at roughly 20KV at all brightness levels. The overhead voltage is so the shunt regulator can do that job at different beam currents. I made this test with no shunt regulation at all. I believe that the initial HV will come up quite a bit after some recapping and tube replacements like the 6BG6 Horizontal output tubes. I still have to go through the tubes and test them all. But this tells me that it is now OK to move forward with the whole project.

Can you go ahead and arrange the convergence transformer purchase? Or are there none left to be purchased? Do I have to build one?

Cheers, Mike


Mike,

I’m glad that we can continue to proceed with the restoration! :-) I’m not sure what the issue is with the transformer. A VK member said “The dynamic convergence transformer is T-701. It needs to be replaced with a Folsom reproduction ASAP, before you damage pots in the focus circuit.” Further, its the same as used in the RCA CT-100. Apparently the part is near impossible to find if bad.

Another VK member said it’s doubtful that John Folsom has a replacement because the last one was sold to a collector. I contacted John a week ago with no response, perhaps my mail went to his junk folder as I haven’t corresponded with him in quite some time.

We don’t know if our transformer is bad? It’s called the vertical convergence transformer T-701. When you reach that point you can test, no? I will post this on VK.

Cheers,
Marshall

I believe that transformer is both vertical output and convergence. The convergence is high voltage, and the failure mode of the transformer is breakdown of the insulation of the HV convergence winding and the other windings. The current drawn when it shorts damages NLA/unobtainium parts like the focus pot.

Thanks for that Tom. Just received another email from Mike. He remembers the issue from reading about it in the past. He understands the issue and has rewound transformers in the past. He has the materials to rebuild and equipment to test a rebuilt transformer.

If John has one available, we would like to purchase one and avoid the tedious work. I think Mike is going to contact John directly. On the bright side we may have a good transformer, but it wouldn’t hurt to have a spare.

UPDATE, OCTOBER 3, 2018

Let’s add clarity

OK. I have studied 3 different schematics.

The Photofact for CT100 RCA calls for a primary transformer DC resistance of 1200 OHMS There are 2 secondaries. Secondary #1 calls for 1800 OHMS and secondary #2 calls for 7200 OHMS.
The Photofact for Westinghouse chassis calls for Primary DC resistance of 1000 OHMS. Secondary #1 is 3200 OHMS and secondary #2 is 3800 OHMS.
Westinghouse factory schematics calls for Primary DC resistance of 1000 OHMS. Secondary #1 is 1350 OHMS and secondary #2 is 375 OHMS.
I realize that these are DC resistance values and the actual IMPEDANCE for the components is not really called out on the schematic. BUT, these numbers should agree to a much greater degree of precision before I believe that the RCA part is the same as the Westinghouse.
I ran out of time tonight but I will be doing DC resistance checks tomorrow night in an effort to sort this out.
Stay tuned!
Mike.
Link: https://visions4netjournal.com/westinghouse/#

VDC transformer
 

After further testing Mike found the VDC transformer open. Thanks to Ben for the heads up.

Out of curiosity, which winding was open on the VDC?

Both secondary windings are open.

The DC values listed on the Sam's Photofacts for both the Westinghouse and RCA are in relatively close agreement. The values given in the Westinghouse service information are extremely low. When you're measuring a DC resistance of the same part, in examples of the same model set, and one of those values is extremely low compared to the other, that's a pretty decent indication that the low reading values were taken with a simple VOM, and the higher values with a VTVM.

In any case, the discrepancy doesn't matter. If you had read John's write up of the new transformer you would see that they've been used in CT-100s, 15 inch Westinghouses, a 15 inch Motorola, etc.

Any differences that may exist between the two parts are too small to make any difference in circuit.

We found this to be true. Can you direct us to John’s write up? Is it in this forum?


Edit: I found it.

Would you please share the link to John's write up?

Hear you go. On the ETF site.

https://visions4netjournal.com/wp-co...911C3A78AC.png

http://www.earlytelevision.org/class..._for_sale.html

The tail end of that page.

Now, the RCA part numbers for the vertical convergence transformer in the Westinghouse and the transformer in the CT-100 are in fact different; the Westinghouse is 241T1 while the CT-100 uses part 3T127.

But, I have a parts catalog that shows them cross-listed as identical. I think it is safe to assume they're the same part; one part number used for OEM transformers in sets built by other manufacturers, one part number for sets built in-house by RCA.

The different part numbers can be accounted for by the fact that in the CT100 the transformer is "potted" in a 5 sided metal box that bolts onto the back of the HV cage. In the Westy, it is just an open frame transformer similar in appearance to a regular vertical output trans.

I wonder why RCA took the trouble to put the transformer in a “box”? Isolation? Did this part fail in the CT-100 as much as the Westy?

No way to know why RCA potted it in a box. Perhaps to better protect it from high humidity or dampness. Failure seems to be across the board in all the sets this trans is installed in. May have been due to defective materials or poor engineering.

Transformer ordered and shipped. Recapping continues, finding poor resistors along the way.

Link: https://visions4netjournal.com/westinghouse/