The white bars roll right along as I adjust the vertical hold out of lock, and back in place when I adjust the vertical into lock.
I'm not sure how much ripple would be needed to cause a symptom like that but G2 has in the neighborhood of 3VAC present on it without any signal injection.
The aquadag still looks intact and making connection to ground, looks can be decieving though I'm sure. Is there a good way to test it's connection to ground to rule it out?
What a mystery we have. Maybe it was the butler in the library with a pipe wrench?

LOL. Here is a clue on that aqua dag check. If you use the grounded screw driver CRT technique to discharge the HV, then use the same tools set up the same and with the set on touch the blade of the screwdriver to the aquadag coating in a few spots and if you get an arc or spark then the CRT's dag ain't properly grounded. Might also be able to use a HV meeter instead of a screwdriver.

Awhile back I accidently confirmed I had this issue on my CTC4 with my hand.....it shook me up and made me swear like a pirate. 25KV can certainly alter ones vocabulary and mood.

Well that rules out G2 and leaves only the cathode of the CRT. Try this for the heck of it- hook that 10mf electrolytic from ground to the cathode (observing polarity of course) and see if the bar remains.

One other thought- After doing the cathode shunt, try shunting G2 with the 10mf cap. Hook its neg. end to top of C116B (which carries smoothest B+) and the positive end to G2. This will effectively kill all ripple on G2, just in case the 3VAC is sufficient to cause the bar.

Maybe he was in the library with a wench.

:tongue:

Negative on both counts :sigh:.
I also did the grounded screwdriver trick to spots on the dag with the set on to check grounding of the crt and it was ok.
Could it be the tube itself?

I'd try running the filament of the CRT on it's own transformer to rule out hum leakage from a heater-cathode short.

Interesting suggestion. What kind of amperidge would that need? The schematic calls for 8A on the heaters for everything else, but no rating on the CRT filament.

I don't know the exact specs, but probably around 800mA should be enough. As long as the filament is not running more than 1 volt high or low it should be safe for a quick test.

The CRT heater already has its own dedicated 'floating' winding in the power xfmr, designated 'Y and YZ', going to 'KIN' (for kinescope, the archaic term for CRT).

Try this- unplug the CRT from the socket and check for heater to cathode short with the ohmeter on highest range. It should read infinity (although a short might occur when the heater warms up). Also check DC resistance form the floating winding to ground. It should also read infinity, but double check the schematic to verify this, and that it's not connected to B+.

With the set on (and the CRT reconnected), measure the DC voltage between heater and ground, and see if it reads the same as the cathode (or not). Ideally, it should not if it's truly 'floating'. Then try shunting the heater to ground with the 10mf cap, first from one side of the heater and then the other. And see if the bar remains.

It reads infinity on the Megohm scale.

It has a path to ground, but it's connected to B+

http://farm8.staticflickr.com/7061/6...c854c8e988.jpg

It reads a different voltage than the cathode. Heater reads +225V and cathode reads +195V, which I see is a little low so I took a measurement where it should read +425V and it only got +350V. It's right on the 20% mark but it looks like I'll be going resistor hunting at some point to address that.

:no: The bar wins this round.

Why is the heater connected to HV? Is that to reduce the potential and the arcing possibility between it and the cathode?

VTS1134,

OldCoot is suspecting one problem, and he very well may be correct.

Let's stop and think about the problem.

I see the vertical section attempting to run at 120 cps and it is badly speed modulating the sweep resulting in dual white bands. In other words, the normal 60 cps sawtooth is being speed modulated by a two backwards steps at a frequency of 120 cps.

The wrong speed operation could be caused by either a 120 cycle hum being fed to it from the power supply or from some component in the vert osc/output circuit being badly off value. (A heater cathode short would introduce a single band. Only the 120 cps hum can create a double band and 120 usually is only found in a full wave power supply.)

1) I assume that you do not have a service scope. If you do, the first thing to check is the B+ and B- power supply sources for hum. Then check to see if the waveforms from the sync separator through the vertical output are correct.

2) Substitute the vertical tube. If you don't have a spare, switch the video output 6SN7 with the vertical output 6SN7 tube. If this changes your problem, then you probably have a bad vertical output tube.

3) Since you restuffed the electrolytics, you might check to confirm that no electrolytic can became accidentally grounded. None of the original electrolytic cans in either the power supply or the vertical section were grounded when RCA built the set.

4) Check every electrolytic in the vertical to make sure you have a close to correct value and it is wired in with the correct polarity. On the Riders on the ETF website, which I've copied in an attachment, the positive side of the electrolytic is always marked with the section marker (ie, the triangle, square or inverted cup). Especially, check C127B between the height control wiper and the 100K going to the wired end of the vertical hold. Another possible source is an incorrect electrolytic across the cathode resister of the vert output. Also check C131B at the vert output transformer.

5) If you had a real mess up in the front end of the power supply you would hear a rather annoying buzz from the speaker, as the field coil of same is used as the filter choke. (If you have a loud hum, then pull the audio output tube and if it continues, then there is a problem in the power supply.)

Hope something here helps.
James

Exactly.

:saywhat:By golly now that we got more of the schematic to eyeball, there's one more CRT element, the focus electrode or "G3" that hasn't been shunted with the .1 (or .25) cap.
Try clamping it, with the cap going from B+ to "G3" (pin 6). If the bar still remains, Mr. Earlyfilm has an idea i hadn't thought of yet:
Hah. "Speed modulation" of the v sweep waveform itself. That's an idea worth exploring.
IIRC, VTS1134 has a variac. While troubleshooting a vert problem in his vintage Majestic set, the idea was floated of driving the vert. yoke winding directly with the variac. Even though it's a pure sine wave, if it were tried on this set, it would at least reveal whether the bar is sweep derived (ie., 'speed modulated' sweep) vs. a rogue pulse on one of the CRT elements.

The focus anode is sitting at around 1500V so even bypassing to B+ is still way over 1000V. Better have a cap rated for this.

I wuz just goin' by the schematic which calls for approx. 495V (varies with focus control setting).

I'm not sure why they show that. The voltage on the focus anode is going to vary between 1475V and 2250V based on the resistor values shown. The RCA spec sheet for the 7DP4 says it should average around 1800V for 7500V operation. Definitely need to use cation and a high voltage cap.

Darryl

Actually the exactitude of these voltages is not all that important as long as you have a bright, in-focus pic and the brightness control has proper range. Having the proper bias relationship between K and G1 is what's important, not so much the voltages themselves relative to ground.

Good call. Maybe it's a misprint of 1495V.:saywhat:

Thank you for your thorough and thoughtful insights. I can answer a couple of things right away.

I have inherited a scope but it is badly out of calibration, and the probe is questionable at best. After reading a few period TV servicing books from front to back two or three times, and with several more on the way I have strengthened my resolve to acquire a working scope and learn how to use it. Unfortunately this doesn't help me currently.
One thing to note about the vertical sync pulses: I performed the following test. I disable the vertical osc by shorting the the grid to cathode and injected vertical grid pulses directly at the grid of the vertical output from my B&K television analyst. My thoughts were to isolate the output from the oscillator to see if the problems came from the sync/osc stage, or elsewhere. I'm not sure if I would have totally isolated the problem as being sweep derived (as OC suggested with the variac test), but the two white bars remained.



I had previously swapped the 6SN7s around in the set and the problem was unchanged.

I'll check on this.

I'll recheck all of the lytics, but I can tell you with certainty that 127A and B is polarity and value correct (in so far as the markings on the cap itself). It was one of the cans that I uninstalled and checked twice. Also R145, the 100K resistor going to the wired end of the vertical hold, checks ok. I'll recheck the other two capacitors tomorrow just to be sure.

There is no buzz or hum in the speaker. I get audio output on channel 2 through my television analyst and what sounds like FM on channel 1.

I'll report the other findings tomorrow. Also if I have time in the day tomorrow I'll have some pretty pictures of the cabinet to share as I put some decals on.

Re: +495 volts on focus anode on schematic

Darryl,

RCA specified that all voltage readings were to be read with a Voltohmyst. Those meters were very sensitive service meters for the era and only have a 11 meg ohm per volt circuit load on DC. The WWII era Voltohmyst was limited to 1,000 volts DC, without the high voltage attachment. (Confirmed by the manual for my RCA 195-A, although the meter scale goes higher. Duh ! )

Note the little asterisk beside the +495 volts on the schematic.

The asterisk means they specified that pin 6, the focus anode, was to be measured only with the brightness control turned fully counterclockwise. This would bias the Kinescope to cutoff.

I suspect cutoff would drop the focus voltage to within the range of the Voltohmyst. It also would increase the 2nd anode voltage to 7,500 volts, which most 1946 service shops could not measure.

This has nothing to do with curing the present vertical problem, but once the set is operational, it would be an interesting experiment to perform, since the focusing anode voltage dropping with beam cutoff, goes against conventional logic.

James.

I was looking at all the entries. Thanks to all that provided all those excellent pictures. I'm not sure what approach I'm going to take on my set. I see all the high value resistors that probably need changing, as well as the caps.:scratch2:

James,
Something still doesn't add up. The focus voltage does not change much over the full operating range of the crt as the load is negligible. The RCA manual does indeed say that besides the Junior Voltohmyst you need the optional high voltage probe which allows measurements to 10KV. That must have been used only for the 7500V measurement as the Voltohmyst was capable of 1000V on it's own, so if the 495V is correct, the meter was used without the HV probe.
The loading of the meter is a fixed 11meg, not 11meg/volt, but even with this extra load, and with the focus control turned to the low side you still end up with 966V. With the control to the high side you get 1250V. I'm still guessing this was a misprint in the original RCA manual and just got duplicated in Riders and elsewhere.

I suppose one of us could go measure it on a working set. Since modern meters are 10M input impedance, any digital or VTVM should work.

Darryl

Well I did have some time today to apply the decals to the set. There were a few coats of lacquer applied to the set to smooth out the surface. There will be many more coats applied now to bury the decals into the finish. I was surprised to find out that the finisher never uses grain filler, instead he simply shoots lacquer and sands until he gets a glass smooth finish (if that is the goal). I'm very happy with the progress so far and can't wait until I see the finished product.

http://farm8.staticflickr.com/7040/6...f0407663_z.jpg

http://farm8.staticflickr.com/7196/6...41ca9ee826.jpg

The sides of the set are a bit darker than the front and top. I would have been happier if they were the same color. The lighting accentuates this fact a bit more than what it looks like in person.

http://farm8.staticflickr.com/7067/6...4f779c0303.jpg

http://farm8.staticflickr.com/7196/6...bd01b2abe8.jpg

The decals are not 100% where they were before, but I think unless you had a picture next to it you'll never notice.

http://farm8.staticflickr.com/7177/6...6370a1daec.jpg

http://farm8.staticflickr.com/7196/6...16ab1875de.jpg

http://farm8.staticflickr.com/7066/6...84fb5be8b2.jpg

Now to get back to the chassis!

Wow! That cabinet work looks fantastic...She'll a nice set when its all back together ::yes:

Nothing wrong with the way it looks! You are on the home stretch with that cabinet...

I'd like to tell a cautionary tale for any one reading this that wants to learn from other peoples mistakes, rather than make their own.
Rebuilding multi-stage electrolytic capacitors has been the most challenging thing I've done thus far on this restoration. As those of you know who have been following this thread from the beginning, I replaced all of the paper and electrolytic capacitors in this set before I applied power. Due to a misprint in the schematic I put a 160v capacitor where a 450v capacitor belonged. What I was greeted with was a cloud of capacitor smoke. Taking the schematic at it's word and thinking that I some how miswired the restuffed capacitor I rebuilt and hooked up the same valued capacitors outside of the set to have visual confirmation that my leads were ok. Again I was greeted with a pop and a cloud of foul smelling smoke. Slightly frustrated at this point I dived into the schematic, and the wiring of the set and deduced that the voltage rating of the cap was indeed the problem. At this point I had two things going against me, I was frustrated because I had two "failures" and I was cocky because I, a rookie, had "cracked the code" and figured out that the schematic was incorrect. I should have turned the lights out and came back another day, I didn't. What I did was hurry to rebuild the capacitors in question so that I could feel like progress was being made and I could shoot that nice raster picture to post here. The result was an incorrectly wired capacitor that was done in such a way that even when another cap was jumped across it's leads it wouldn't show itself. I can, however, take a positive away from this mistake, and that is what I have learned through the trouble shooting steps that the knowledgeable and helpful people here at VK led me through.
Learn from my mistake, when frustration or any other emotion that forces you to work anything less than 100% focused and deliberate, turn the lights out and come back another day.


Now for the good news. The set currently resembles a patient on life support as I have frankenwired some capacitors outside of the set to take the place of the multi-stage can in question.

http://farm8.staticflickr.com/7204/6...a6dd7442bf.jpg

I have ordered smaller replacement capacitors for that section but for now I have a much better picture on screen :)

http://farm8.staticflickr.com/7052/6...0197d10681.jpg

There is still much work to do, but for tonight I'll turn the lights out and come back another day.

:smoke:


Not tooting my own horn or anything, but I had a feeling that was the problem. Can't blame yourself though, I frequently find errors in schematics so it's not a very big leap to assume something was misprinted. Glad you found out what was causing the issue, pic looks great from what I can see. :thmbsp:

And, also at the risk of sounding "cocky", if you are replacing a multi-section capacitor, the values are usually written on the can so you can "double check" the schematic. Bet the error was in a Sams Photofact? They are usually good but can have mistakes. Glad you sorted it out...

Congrats, I'm glad you got it sorted out too :)

Good job of sleuthing it out, Mr. Dragonslayer. :banana: And you learned an important point too: Sams is notorious for misprints and diagram errors. The old adage "Trust but verify" always applies. I liken it to riding a bike on city streets. Assume every parked car door is going to swing out on you.

BTW, which cap was it?

I think the more important lesson to take is that I was frustrated and worked in a hurried manor that caused me to make a mistake. Learn from my bone headedness and when you get :gigglemad turn the lights off and return when you're :cool:.

I need to learn to re-read stuff. Doh.:o

Making some more progress on the set. I went though every resistor in the horizontal circuit and replaced quite a few that were way out of spec, or completely open. I fired the set up after each replacement to make sure nothing went wrong, and to enjoy seeing the picture get better and better with each step. I still have (at least) two problems with the video currently. One problem I could not get completely sorted out with resistor replacement in the horizontal circuit was a bit of tearing at the top of the screen.
http://farm8.staticflickr.com/7040/6...7376780cea.jpg
It was easiest to photograph the phenomenon by injecting video right at the grid of the video amp and adjusting contrast until it showed up. It is possible to get a stable picture most of the time, but when there is full motion video on screen it will occasionally tear horizontally at the top of the screen, just like the picture above but some times much worse. The last set I worked on had a Sams for it and gave a procedure for horizontal adjustment. I cannot seem to find one in the Rider for this set however. Maybe it's just a matter of adjustment that I'm missing?
My other problem is before the video amp. I'm getting some trailing ghosting in the picture.
http://farm8.staticflickr.com/7208/6...1298cb4b89.jpg
I haven't dived into this problem just as I would like to get the horizontal sorted first but thought I'd share.

In regards to those trailing ghosties, be sure and check peaking coils L105 and L106 for continuity.

Seems like the tearing/'flagging' is related more to signal overload than horiz. adjustment since it straightens up as you lower the contrast. This set doesn't appear to have any AGC (automatic gain control) at all. The contrast ('Picture') control adjusts the gain of the 2nd IF tube, requiring you to manually adjust it for varying signal strengths. Too strong a signal and the pic gets the bends. Just one of the charms of the old beasties, sorta like riding the gain on an old TRF radio.

L105 and L106 read a bit low on my voltohmist but they are in the neighborhood.
I've shot a couple of videos of what the set is doing. The first one is from the B&K 1077 and shows that the two problems seem to be interrelated. When I adjust the picture control I can get a steady picture with ghosting, or a ghost free picture with tearing, but not both. The ghosting is much easier to see in the black blocks at the bottom of the screen (is there a proper name for those blocks?).
http://www.youtube.com/watch?v=rLJRdzFB-yU
The other video displays the occasional horizontal tearing towards the top of the screen with full video that I described before.
http://www.youtube.com/watch?v=28X9hkIWCQE
I'll check the resistors and voltages in the video and if stages next to see if anything jumps out there.

The tearing seems to be from overloading, the ghosting possibly some misalignment in the i.f.'s?

Whaddabout the case ? I have a VERY GOOD furniture refinisher here...I've used them quite a lot & they understand about tube diagrams, decals, etc.. Just sayin. PM me for their addy/phone #

The 'ghosting' doesn't look like the smearing/ringing of fine detail you typically see with IF misalignment.
What happens if you inject video at the CRT grid, working back point by point? Have to reduce the B&K's output as you move back (to keep the pic from flagging) and reverse the phase a time or two. See at what point the ghosting appears.

Sorry that there's not much to report on the cabinet. Since I'm not doing the work myself I can't post regular reports with pictures. The only piece of news I have is that the day after I applied the decals to the set my refinished sprayed a coat of lacquer to seal them in. He just underwent hand surgery on both hands so he's working slowly. He knows how picky I am and is doing some other less intricate projects while he heals up. :) all the more time to perfect the chassis.

Regarding the tearing, I don't know what the horizontal setup procedure is for this set but it might be due to instability?