Westinghouse K840CK15 Restoration - Page 12 - Videokarma.org TV - Video

etype2 · #**166** 07-26-2019, 11:29 AM

UPDATE, JULY 25, 2019, DAY 355

LIGHTS OUT.

From Mike:

“Hi Marshall. Recently I have noticed that the power supply voltages are not stable at the voltages that they need to be at. There are basically 3 voltages supplied here. The Westinghouse prints call them to be 410 VDC and 310 VDC, and 120 VDC. The issue with the variations in voltage are simply design related. The 310 VDC supply is also supporting the High Voltage regulator circuits and the bias on that stage is critical. I was having problems with the High Voltage regulator becoming unstable and causing fluctuations in the high voltage setting. I decided to replace the two 5U4 rectifier tubes that supply the 310 VDC with silicon rectifiers. I added a 300 ohm 50 watt resistor in the system to keep the voltage at 310 VDC since the silicon rectifiers are more efficient than the 5U4’s. I also decided to keep the 5U4 that supplies the 410 VDC since that is mainly for the sweep circuits, and that is all working fine. I have also been working on the edge convergence and NOT having much luck with that so far. Tonight, as I was tinkering with that problem, one of the silicon rectifiers shorted and all the lights went out in the shop! Not sure why that happened yet. Possible, just a sporadic failure of the rectifier. I will review the specs on the parts that I used and continue with the progress. This edge convergence problem is next.

Cheers, Mike”

etype2 · #**167** 07-27-2019, 03:14 PM

Hi Marshall. The voltages naturally would have been a bit higher with the silicons in there but I never allowed that to happen. I wanted to keep the voltages in that part of the power supply at the specified 310 and 120 so that is why I added the 300 ohm 50 watt resistor to that line. I suspect the previous variations were caused by the two 5U4's that are wired in parallel and support the 310 and 120 supplies. Tubes can vary as they warm up, even if they are new. The silicon rectifiers fix that. The single 5U4 that supports the 410 volts for the sweep circuits is not a problem because the overall loads there are way within the capability of the 5U4. And yes, one of the silicon rectifiers shorted which is what brought down the shop. One thing that puzzles me is I recently added a line fuse which should have blown, and it did not. The fuse was rated at 10 amps and perhaps I should have rated it at about 6 or 7. The puzzling part is that the inverter that powers the shop should have handled a 30 amp load which should have caused a 10 amp fuse to blow, and it did not. It is possible that the fuse is somehow out of range too. But that is not by any means a normal failure mode for any kind of fuse. They normally fail safe and their "trip" value decreases with age. Long story short, I will be replacing it with a lesser value before continuing.

Be back soon, Mike

Electronic M · #**168** 07-27-2019, 06:01 PM

Inverters tend to monitor load real time and trip out instantly on loads much higher than they are rated to drive...on the other hand many fuses are slow blow and take noticable time to open.

etype2 · #**169** 07-27-2019, 06:50 PM

I think your saying the inverter detected the fault before the fuse reacted to the fault? Would you care to speculate as to the cause?

Electronic M · #**170** 07-28-2019, 10:21 AM

Quote:

Originally Posted by etype2

I think your saying the inverter detected the fault before the fuse reacted to the fault? Would you care to speculate as to the cause?

Condensed version of above explanation: Tslowblow_fuse_open>>Treal_time_load_monitoring_fa ult_open.

When the diode shorted it probably did so instantly and the load spiked above both devices rating instantly rather than slowly ramping.
If 2 safety devices in series are both instantly brought to fault input state whichever one has the faster reaction time will open regardless of actual current ratings of the individual devices and how extreme the fault is.

If you took the line 10A fuse from the Westinghouse and put it in series with a fixed resistive load that draws 20A and plugged that fused load into the 30A limited inverter the load would probably receive power for a humanly noticeable time period then 10A fuse would blow and the inverter would stay on. If you took 2 such load/fuse pairs wired them together and plugged the combined 40A load into the inverter then the inverter would probably trip first at a much faster speed.

etype2 · #**171** 08-06-2019, 01:31 AM

UPDATE, AUGUST 5, 2019, DAY 366

From Mike: “Hi Marshall. I have made significant headway on the convergence issues. But I have had no time to document any of it. The problem that I had with the convergence control was a failure due to arcing to the “floor” of the high voltage cage. Fortunately, my original design was really OK and I had purchased qty 2 of the Zenith 63-7145 controls so I had a spare. I have installed the spare, and insulated the floor of the cage and since then I have been able to achieve good convergence, except for the blue on top and bottom. I may not win that one. But there may be some small thing that I have missed. I will be reviewing the Westinghouse convergence procedures again and see what happens with that. And, I am really not happy with the crt response, at least compared with the images that I had on the 21FBP22 jig tube. We may want to talk about that at some point. It is true that the numbers came up after some “use” but they did not come up by very much. The blue numbers are quite good compared to the green and red. The red is especially poor in my opinion. I will be sending some more photos of the convergence and picture quality within the next few days. In general, things are becoming more reliable but the high voltage issues and arcing and corona have been a big problem. When I look in to the high voltage cage, and see the design, it makes me wonder how some of it ever worked. No kidding. Everything is way too close together within the cage and arcing from stage to stage was most certainly a problem from the beginning. These engineers were under way too much pressure to “just get it going so we can market it”.

OK to post all of this as a part of Westinghouse history, as far as I am concerned.

More to come soon. And ETA is likely sometime in October if all goes well.

Best Regards, Mike”

Author: I know Mike is preparing me for disappointment in the picture quality, but even prior to the purchase of this Westy, my expectations were not high based on the images I’ve seen on 15GP22’s. We purchased the Westy for its history. Mike knows I’m a perfectionist when it comes to picture quality based on our interactions on two previous roundie restorations. Strangely enough, the green gun tested weaker than the red and yet, all three guns are in the “good” area of the tester. We will know more when Mike sends the first images on the 15GP22. (Edit: Other than crosshatch patterns.)

trinescope · #**172** 08-06-2019, 07:55 AM

I think the 15GP22 is just going to be limited in performance due to two factors. First, the phosphor dot pattern is a bit large for the screen size, so it's going to give GE Portacolor levels of resolution. Second is the red phosphor which is going to limit overall brightness as well as needing to run the red gun much harder than the other two.

Something I noticed when I had my set running is what looks like a horizontal brush stroke pattern in the upper third of the faceplate. It appears like it's behind the flat faceplate surface. It becomes noticeable when there is a bright area of solid color, like a bright blue sky, for example.

etype2 · #**173** 08-06-2019, 11:43 AM

Quote:

Originally Posted by trinescope

I think the 15GP22 is just going to be limited in performance due to two factors. First, the phosphor dot pattern is a bit large for the screen size, so it's going to give GE Portacolor levels of resolution. Second is the red phosphor which is going to limit overall brightness as well as needing to run the red gun much harder than the other two.

Something I noticed when I had my set running is what looks like a horizontal brush stroke pattern in the upper third of the faceplate. It appears like it's behind the flat faceplate surface. It becomes noticeable when there is a bright area of solid color, like a bright blue sky, for example.

I will be looking for that pattern. Do you think it’s a manufacturing defect?

trinescope · #**174** 08-06-2019, 01:00 PM

Probably less of a defect than an artifact of the manufacturing process which was different than that of the 21AXP22 and later tubes. I'd have to go back and re-read the RCA process description to see how the dot pattern was laid down, but I do remember that it was silk screened instead of a photoresist process used on the later tubes. Perhaps a layer of binder material was applied first, or it comes from the silk screening of the phosphors.

trinescope · #**175** 08-06-2019, 01:30 PM

In addition, I don't have a CRT tester as of yet, but based on what I have seen so far i believe i have a decently good 15GP22. I was getting a good grayscale out of it and decent brightness for a CRT of its type (no, not like a Chromacolor or Trinitron, but you don't have to squint in a dark room, either). I haven't installed the CRT since doing the IF alignment, so I don't know what kind of improvement I have made with that. I need to get more .1uF capacitors ordered, and need to find a solution for the convergence transformer. I was getting grayscale shift due to leaky bypass capacitors on the G2 grids causing the voltages to change by several volts.

dtvmcdonald · #**176** 08-06-2019, 03:04 PM

My 15GP22, before going gassy, also had the "brushstroke" effect, though very minor.

If you want the best picture, I suggest scoping the red gun signal, right at
the CRT, and set the contrast so that the red gun grid never goes
positive with respect to the cathode. Then readjust the blue and green guns for correct gray scale.

You will never get perfect tracking with such different peak currents.

etype2 · #**177** 08-06-2019, 03:57 PM

Quote:

Originally Posted by dtvmcdonald

My 15GP22, before going gassy, also had the "brushstroke" effect, though very minor.

If you want the best picture, I suggest scoping the red gun signal, right at
the CRT, and set the contrast so that the red gun grid never goes
positive with respect to the cathode. Then readjust the blue and green guns for correct gray scale.

You will never get perfect tracking with such different peak currents.

I will pass along your suggestion to Mike.

etype2 · #**178** 08-06-2019, 04:12 PM

As a side note, anyone know why Westinghouse used copper cladding on the chassis. Admiral did the same thing.

Also, what do the designations GP in 15GP22 and XP in 21XP22 mean? XP for experimental?

Electronic M · #**179** 08-06-2019, 04:33 PM

Quote:

Originally Posted by etype2

As a side note, anyone know why Westinghouse used copper cladding on the chassis. Admiral did the same thing.

Also, what do the designations GP in 15GP22 and XP in 21XP22 mean? XP for experimental?

P4 = monochrome phosphor, P1 =green oscilloscope phosphor, P22= tri color phosphor for color TV. Previous letter(s) is a randomly chosen identifier picked when the tube is registered as a new type with IIRC the RMA. There were other types of phosphor (for a variety of applications including radar) with their own P number (Wikipedia has a list). A 7JP4 tv CRT and a 7JP1 scope CRT are identical parts asside from phosphor color and you could interchange them with each other with out issue (as long as you don't mind a white scope trace and green TV picture).

In 1968 the government passed a law that TV screens had to be sold and CRTs identified by viewable area diagonal and not envelope diagonal. Many tubes made after that point had a V as the first letter and the diagonal number was 2" smaller....So a 1966 25XP22 might become a 1969 23VXP22.

etype2 · #**180** 08-06-2019, 04:50 PM

Quote:

Originally Posted by Electronic M

P4 = monochrome phosphor, P1 =green oscilloscope phosphor, P22= tri color phosphor for color TV. Previous letter(s) is a randomly chosen identifier picked when the tube is registered as a new type with IIRC the RMA. There were other types of phosphor (for a variety of applications including radar) with their own P number (Wikipedia has a list). A 7JP4 tv CRT and a 7JP1 scope CRT are identical parts asside from phosphor color and you could interchange them with each other with out issue (as long as you don't mind a white scope trace and green TV picture).

GOOD TO KNOW. THANK YOU.

In 1968 the government passed a law that TV screens had to be sold and CRTs identified by viewable area diagonal and not envelope diagonal. Many tubes made after that point had a V as the first letter and the diagonal number was 2" smaller....So a 1966 25XP22 might become a 1969 23VXP22.

I LEARNED ABOUT THIS MANDATE BACK IN THE DAY. I TAKE YOUR POINT.

I don’t recall anyone discussing copper chassis? Benefits?