Deja vu. It feels like I've been on this forum before.

https://live.staticflickr.com/65535/51574961806_29ca516773_z.jpg

I've had this Admiral 17T1 for 11 years, and I've had three previous episodes of trying to fix it. This is the fourth episode checking and rechecking the
electronics against four different schematics. Before last night, this was the best I could do:

https://live.staticflickr.com/65535/51574964609_fdddcd5621_z.jpg

Last night I got this. I touched no control except 'on' and 'off.'

Flickr link to video: https://flic.kr/p/2mycedY

Overnight I changed nothing, but this morning I got this:

Flickr link to video: https://flic.kr/p/2mzpadh

One question to start. So far I've been using a combination VCR/DVD with a coaxial cable and F connector for both tapes and disks. I want to use a DVD player. How do I get the signal from the player with RCA plugs and sockets into the TV?

Thanks for listening,
Winky
aka Little Radio Man.

You need to use a video modulator. Cables with RCA connectors go between the DVD player and the modulator. Then a cable with F connectors goes from the modulator to a 75 to 300 ohm balun transformer that converts to twinlead that connects to the TV terminals. I have a RCA modulator but I don't think those are available now.
https://www.amazon.com/GE-RF-Modulator-with-S-Video/dp/B087V5YB4L/ref=sr_1_2?dchild=1&keywords=video+modulator&qid=1633960697&sr=8-2
You should get a modulator like this now, they put out a old NTSC analog signal.
At some point only the modulators that do digital will be available, those will not work with vintage TVs.
There may be something mis-wired on that TV. Do you have an oscilloscope?
Maybe the deflection frequencies are far off or badly distorted. Maybe the video detector is installed backwards. The sync separator might be fowled up. A scope could help sort it out. Have you checked the voltages in the deflection circuits?

Notimetolooz beat me to it ;)

Thanks for the reply. My approach to electronic restorations is that if all the parts are good and you put them together in the right way, it will work. Beyond that, my understanding of electronics is minimal.

Sometime recently I came across someone making and selling modulators. Maybe it was the guy on Amazon. I'll follow up on that.

I'll look into the television sections you mentioned. What are you referring to as the video detector? When I hear "video detector" all I can think of is a tube--which even I can't install backwards.

As for oscilloscopes, I can't even spell it. Plus, in Idaho possession of an oscilloscope is a class B felony.

Thanks again,
Winky

Indeed, a cheap RCA modulator will work just fine.

https://www.amazon.com/gp/product/B06XC9Y3VB/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

jr

That's an interesting picture. Your horizontal oscillator is 100 miles off from where it should be. There also appears to be a sync issue, and about 2/3 of your vertical is compressed into a band at the top.
The horizontal is either half, or double of the normal horizontal frequency in the first video.

Has the horizontal hold control slug been turned way to the bottom or the top?

Try adjusting the H hold control from one extreme to another.

Has the set been recapped?

What work has been done to it?

Does this schematic match your set fairly well ?

http://www.earlytelevision.org/pdf/admiral_17t1_telaides.pdf

jr

I'll look into slug tonight.
The set has been thoroughly recapped.
I have four schematics. I settled with the Telaides schematic, which matches almost perfectly. The Admiral 19A1 and 17T1 had a number of production changes over time plus recommendations for dealer-installed upgrades. So all four are different.
I'll make a list of things I might have screwed up.
Always grateful for your patience and guidance.
Winky

The reason I asked about the oscilloscope is that many times if there is an image on the TV screen it sort of functions as a oscilloscope itself, but this image is so scrambled that it is tough for me to figure out. A scope would let you view the vertical scan, horizontal scan and video signal separately which may clarify what is going on.
I think there are several problems being seen at the same time, so it is confusing.
Some sets used a germanium diode for the video detector. If the set has been worked on it may have been installed backwards. That might invert the sweep sync pulses and confuse both vertical and horizontal scans. However the video signal doesn't seem to be negative so maybe the detector is not the problem.
Tubes, caps and resistors are not the only things that can cause problems.
Also if it has been re-capped, there could be mistakes made.
If you have been trying to get the set to work for some time, do you have links to what went on during those earlier attempts?

I am looking through notes and photos going back to 2010,and I will shortly post the history with schematics. The short story is: I bought it and it worked. The chassis had some previous modern repairs, but also had failed soldered connections, a cardboard electrolytic with goop oozing out, and other stuff. I started "fixing" it and it broke.

This is the saga of the Admiral 17T1. I bought for $100. Took it home, hooked up a VCR, and this is what I got:
https://live.staticflickr.com/65535/51574961806_29ca516773_z.jpg (https://flic.kr/p/2mzvaiq)Adm 17T12 010 (https://flic.kr/p/2mzvaiq) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Click the pics for the original photo.

I opened the chassis and saw stuff that had to fixed. Like these open solder connections:

https://live.staticflickr.com/4325/35158699564_5d4c07404a_z.jpg (https://flic.kr/p/VyRwtf)17T12 035 (https://flic.kr/p/VyRwtf) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

And this cardboard electrolytic:

https://live.staticflickr.com/4316/35609637730_26cafc84b0_z.jpg (https://flic.kr/p/WfGGFd)17T12 037 (https://flic.kr/p/WfGGFd) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

The point is that it really needed electronic restoration, which I started two years later.
Two potential problems were (1) I was using an early 19A1 schematic, and (2) The only diagnotic equipment I had was a multimeter.

Making no progress, I resorted to testing components by replacing them. Someone suggested that C37 and C39 might be problematic. Unlikely that mica caps would fail, but I went ahead and replaced them. Unfortunately, I didn't notice that they were rated 1,000 volts, so I used 630 volt caps. Here's a schematic showing the offending condensers (in yellow):

https://live.staticflickr.com/65535/51582181044_f7293f18fd_z.jpg (https://flic.kr/p/2mA9ak3)Adm 17T12 8900 (https://flic.kr/p/2mA9ak3) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Lo and behold, the instant I turned on the power some wire insulation melted, the wax on C41 melted, and the horizontal size pot was toast. I replaced the pot, wiring, and resistor and then put the set away for six years.

I started again last year with the Wallace-Telaides schematic, tube testers, a capacitor tester, and lots of other stuff. Tested every capacitor and resistor except micas, ceramic, and tiny dogbone resistors. Checked continuity throughout the set including the resistance of every coil. And ensured that I had a good set of tubes. Even tested the picture tube on a Philco 7053 CRT tester.

Replaced everything that needed replacing, then rechecked the wiring for every component. This is what it looks like today:

https://live.staticflickr.com/65535/51545230070_7f9e0a6c6a_z.jpg (https://flic.kr/p/2mwSM6h)Adm 17T12 5020 (https://flic.kr/p/2mwSM6h) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

For Tube TV: I'm guessing that the horizontal hold control with the slug is the transformer on top of the chassis directly over the hhold pot. If so, the slug is centered and has no screwdriver slot for other-than-factory adjustments.

Phew, that was a lot of work. I hope the links work.
Winky

One more thing. When I restarted the project last year my biggest concern was I had errors related to using a 19A1 schematic. My first step was to invent the "Schematic Differential Too." The Rider 19A1 schematic and the Telaides 17T1 were made on the same template. I printed the Rider schematic in red on white paper and the Telaides in black on transparency film. This is how I identified differences in the schematics:
(I just learned how to embed photos that you can click to go to the original)

https://live.staticflickr.com/65535/51525258825_40175fc02b_m.jpg (https://flic.kr/p/2mv7qkt)Adm 17T12 5000 (https://flic.kr/p/2mv7qkt) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Hence I wired the 17T1 to be in compliance with the Telaides schematic. Except for R41.
Thanks again.
Winky

Hummm, C41 is across some tube filaments, hard to see how the wax could melt and the filaments did not burn out unless it was a dead short.
That doesn't explain why the horizontal size pot burned.

Are you sure you read the value on C37 and C39 right?
They look a bit small for 1000 pf, 1000V.

What do you mean "factory adjustment"?
The coil may adjust with a hex tool (non-metallic).

If those mica caps were in the deflection stages then they are likely to have failed. Deflection circuits are much harder on micas than tuner and IF stages are. About a year ago I found a mica dead shorted in a 7" Philco electrostatic deflection TV's sweep.

It looks like you used some sort of ceramic cap for C37 and C39 ? Unless those are C0G type dielectric that could cause problems.

I don't think the core of the horizontal transformer is adjustable.

The horizontal sweep circuit is very cleaver.... I am going to re-read this several times to try to understand how it works, maybe the cause of the apparently distorted horizontal waveform is excessive ringing. :scratch2:

http://www.earlytelevision.org/pdf/admiral_tv.pdf

jr

, maybe the cause of the apparently distorted horizontal waveform is excessive ringing. :scratch2:


jr

I was thinking along the same lines. Those could be 100pf instead of 1000pf.
Also ceramic caps can change their capacitance as the voltage changes a great deal (as in a sweep circuit).

Indeed they are ceramics. I've looked through my stuff and the only alternative I have to meet the capacitance and voltage rating is yellow film 630V caps wired in series. But first I have to post some information for reference. Thanks

While rethinking what I've done with this set I need to deal with one issue at a time. First issue is the wiring of R41, replacement of C37 and C39, and the destruction of the H-size pot. Everything I've said is based on assumption and memory (or misassumption and forgetfulness) from 10 years ago.

I'm going to post here several 17T1 and 19A1 schematics. I'll follow that up with photos showing what I really know about these components. Patience, please...I have to write everything offline first because of my slowness I can't even write a quick response without being logged off.

This is overlay of the Rider 19A1 schematic (Red) and the Telaides 12T1 (Black):

https://live.staticflickr.com/65535/51525258825_40175fc02b_z.jpg (https://flic.kr/p/2mv7qkt)Adm 17T12 5000 (https://flic.kr/p/2mv7qkt) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Telaides 17T1:

https://live.staticflickr.com/65535/51524579638_d7925b1997_z.jpg (https://flic.kr/p/2mv3Wrm)Adm 17T12 5005 (https://flic.kr/p/2mv3Wrm) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Rider 19A1:

https://live.staticflickr.com/65535/51524579568_f2b2f06239_z.jpg (https://flic.kr/p/2mv3Wq9)Adm 17T12 5010 (https://flic.kr/p/2mv3Wq9) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Sams 19A1:

https://live.staticflickr.com/65535/51580636122_9619fba58a_z.jpg (https://flic.kr/p/2mA1f5s)Adm 17T12 5001 (https://flic.kr/p/2mA1f5s) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Figure 59 19A1 (I don't know what publication this is from):

https://live.staticflickr.com/65535/51582317680_4d81db834c_z.jpg (https://flic.kr/p/2mA9RWQ)Adm 17T12 5016 (https://flic.kr/p/2mA9RWQ) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Hand-drafted 19A1 (I don't know the source of this one, either):

https://live.staticflickr.com/65535/51554669930_5e0e9b4f7b_z.jpg (https://flic.kr/p/2mxHaeu)Adm 17T12 5014 (https://flic.kr/p/2mxHaeu) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

R41 C37 C39 H-size pot in three different schematics:

https://live.staticflickr.com/65535/51584242639_fbd29b28dc_z.jpg (https://flic.kr/p/2mAjJaM)Adm 17T12 5018 (https://flic.kr/p/2mAjJaM) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Original R41 (It definitely connects to V12 pin 2):

https://live.staticflickr.com/65535/51584480205_28c911b356.jpg (https://flic.kr/p/2mAkWMK)Adm 17T12 5017 (https://flic.kr/p/2mAkWMK) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

A few more historic photos for illustration.

Original C37 & C39 in situ.

https://live.staticflickr.com/65535/51586495430_a4f4206de8_m.jpg (https://flic.kr/p/2mAwgR1)Adm 17T12 9003 (https://flic.kr/p/2mAwgR1) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Actual first replacement caps:

https://live.staticflickr.com/65535/51585818808_8ac68642a8_m.jpg (https://flic.kr/p/2mAsNH7)Adm 17T12 9002 (https://flic.kr/p/2mAsNH7) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Damaged horizontal size pot:

https://live.staticflickr.com/65535/51586317854_d84fefa878_m.jpg (https://flic.kr/p/2mAvn4m)Adm 17T12 9004 (https://flic.kr/p/2mAvn4m) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Regarding my scenario of destruction of the H-size pot after replacing C37 C39 with 630 volt film caps. The problem with the image on the CRT may have preceded that blunder, and instead of one or both of the 630V caps failing, I could have miswired them

RE: Are C37 and C38 .001 mfd or .01 mfd? They are both 102K 2KV, and the Sams and Rider parts lists specify .001 and 1000 volts. I thought I had posted this before, but I can't find it.

Have you done voltage checks around horizontal, vertical and sync tubes? It would be interesting to compare to the values posted in the Telaides info.

Is there confusion caused by v12 being labeled as v13 in the Sams info and/or missing power supply connections lost in the fold of the Sams page?

jr

Winky Dink, please chose a schematic and stick with it. You can't mix and match sections from different schematics.
Also you are just confusing every one shifting back and forth, the part names (like R41) are different between schematics.

If you don't have the correct parts needed you will have to get them.

I have stayed with same Telaides schematic. I know about different part numbers. If I refer to a part number from the schematic I'm using and then refer to the same part on a different schem, I will have made the number translation.

I've stayed with the Telaides schematic until I got to R41, whose original (factory) placement did not agree with the schematic. The set worked when I got it, so I chose to stick with the original R41 wiring. That's what all the photos and schems are for--to illustrate the conflict and show what I've done. I use a lot of illustration because I may not be able to communicate things is electronic language.

Thanks. I'm reviewing more photos to find when the problem started.

Response to jr tech: I have some voltage data from 2018, and I'll run that again and compare them before addressing any issues. There is no confusion with Sams numbering. I learned that on the first project I worked on. In this case I started with Telaides and Rider which are identical, and if I look at something in Sams, I'll translate the parts numbering first--especially the tubes.

OK, I see now that the ceramic discs C37 and C38 in your pictures are 0.001 uf. It is a bit hard to read the value, I thought that they might be marked 100 (on some earlier ceramic discs (or even mica) that might mean 100 pf) not 102. Unless ceramic caps won't work there they should be OK.

So you haven't made it clear how you think R41 was connected if it didn't match the Telaides.
What schematic would show that.

I assume that you have already replaced the horizontal size pot R46.

R41 is directly connected from the sweep of the horizontal size pot to pin of V12. As show in this photo, it is the original factory connection. Yes, I did replace the pot.

https://live.staticflickr.com/65535/51584480205_28c911b356_m.jpg (https://flic.kr/p/2mAkWMK)Adm 17T12 5017 (https://flic.kr/p/2mAkWMK) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Also, since the question arose about some voltage data, here's a full run done last night. It's basically the same as it was in 2020 and 2018.

https://live.staticflickr.com/65535/51588919681_9ecd194d4c_m.jpg (https://flic.kr/p/2mAJGur)Adm 17T12 8910 (https://flic.kr/p/2mAJGur) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Thanks once again.
Winky

R41 actually has nothing to do with the operation of the horizontal size control or horizontal circuit. That side of the pot is going to B+. They're just using it as a handy connection point for R41 which is part of the sync amp.

You can't use ceramic caps for C37 or C38 unless they are C0G/NP0 type. Plastic film would actually be more stable than your average ceramic cap.

Weak video might cause poor sync... the very low voltage at the plate of v9 will likely cause weak video. Fixing that might help. Check the resistance of L9, R35, L10 and R36 and replace as necessary.

jr

jr tech: L9 and L10 coils have exactly the specified resistance, R36 is exactly right, and I can't measure R35 because it's a resistor-through-coil. I could disconnect the coil to check the resistor, but I think it's more significant that the voltage before the L10 resistance is only 65 volts. L10 is also a resistor-through-coil, but it doesn't look that way on the schematic.

Notimetolooz: To make the wiring of R41 agree with the Telaide 17T1 schematic: From V11 pin 2 there is a 1 Meg resistor R39 which connects to a tie strip. That would be the connection point for R41.

Hence I wired the 17T1 to be in compliance with the Telaides schematic. Except for R41.

Winky

You shouldn't put a teaser out like that.
The obvious next question would be "So how is R41 wired?".
After searching the schematics that you posted, and ignoring the ones of questionable heritage, the connection of R41 are all the same except the SAMS 19A1. That SAMS shows it connected to B+, the same source as the horizontal size pot, this indeed seems to be how your R41 is done.
The set uses what is sometimes called a "split supply" like many. The audio output stage (V4) receives B+ for power, the audio output tube is one of the tubes in the set conducts a fairly constant high current. A voltage is developed from the cathode (pin 8) that is also fairly constant, this voltage is used by several other circuits for power. The Wallace Telaides schematic shows this voltage supplies R41 not B+. B+ is much higher than the voltage from the audio output cathode.
Just to eliminate them as a source of a problem why not replace C37 and C39 with micas. Micas are available.
https://www.digikey.com/en/products/detail/cornell-dubilier-electronics-cde/CDV16FF102JO3/1918615
Expensive but maybe worth saving the torment of solving the problem.

Weak video might cause poor sync... the very low voltage at the plate of v9 will likely cause weak video. Fixing that might help. Check the resistance of L9, R35, L10 and R36 and replace as necessary.

jr

It could be that the video output (V9) is drawing more current than normal.
The current draw could depend on the contract control.
He has checked all the resistors.

Is the voltage low on both sides of R-36? :scratch2:

jr

jr tech: Yes, voltage is low on both sides of R36. I tracked it back through a couple more components and it's consistently low.

Notimetolooz: Early this morning I replaced C37, C39 with plastic film caps, each with two 630V caps in series yielding 950pF. I'll see if they make any difference tonight, but I'll order the mica caps as well.

I'll also mention that for audio output my set has a 6Y6 as in the Telaides schematic. The Telaides voltage chart shows a 6AS5 for audio output, and all of the other schematics (regardless of heritage) show a 6AS5.

Winky.

So R-36 is connected wrong.... the supply end should have the same voltage as V-9 pin 6, which you measured at 138 volts. Check the wiring around V-9. :scratch2:

jr

I'm working on it. Will pick it up tomorrow.
Thanks.

Your voltage table shows 138V on V9 (pin 6) screen and 58V on V9 (pin 5) plate. A difference of 80V, most would be dropped across the 8.2K R36, that gives a plate current of nearly 10 ma. which could be. The listed drop should be 15V, but that can be effected by the contrast control. If L9 or L10 has a higher resistance then some of the voltage drop will across them and the current would be lower.
Don't worry about R35, the lower coil resistance will make that value unimportant in comparison.
Things could also be wired wrong.

Winky Dink, in the future avoid 'rewiring a set to match a schematic' if a set varies from schematic and the parts and workmanship look original you should keep it that way.
The only time to force a set to match it's schematic is when it's been hacked up by an idiot, or when you know which stage of the circuit the problem is in and you've exhausted all other possible fixes.

I traced every connection from each V9 pin until I ran into a different tube or other stopper, but I found no errors.

BUT!! As I was pondering cutting the coil in a resistor-through-coil to check the resistor, I also pondered Notimetolooz's mention that the contrast controlled the voltage. When reading the voltages, my contrast was set at the max. Although the instructions were to set the controls at the midpoint, I only set the rear controls. My bad. Voltage at V9 pin 6 varied with contrast from 56V to126V, and V9 pin 5 varies to a much lesser degree. Setting the contrast control at the approximate midpoint, pin 5 was 142V and pin 6 was 118V. Ta dah!

It's no solution, but at least that low voltage can be ruled out as a symptom of the problem.

“pin 5 was 142V and pin 6 was 118V”

Are these backwards?

jr

Yes. Backwards. I'm trying to think of an excuse. I'll let you know if I find one.

“jr tech: Yes, voltage is low on both sides of R36.”

Is this still true when the contrast control is adjusted properly for voltage table comparison? Should be about 24 volts across the resistor. :scratch2:

jt

I'll check that now. Could be up to 30 minutes after now.

Twenty-seven volts. 143V on the pin 6 (grid) side. 116V on the pin 5 (plate) side.

So r-36 is apparently connected correctly, and post 34 was in error, as the measurement across r-36 should have shown the 80 volt difference measured between pins 5 and 6 of v-9, as notimetolooz stated in post 37. :scratch2:

jr

The voltage difference between pins 5 and 6 of V-9 is dependent on the setting of the contrast control. When contrast is set at midrange as directed in the instructions, the voltages are consistent with the specifications in the voltage chart.

The 80-volt difference is correct when the contrast control is at its max setting.

Have C-37 and C-39 been replaced with mica caps yet? :scratch2:

jr

Yup. C37, C39 are now .001pF mica, but no improvement. Reassessing the problem. Set worked before I started restoration. Intended to do nothing but replace paper, cardboard, electrolytics, and defective components. But after I started work, the set didn't work. Two possibilities are (1) I inadvertently changed something, or (2) There are one or more failing components which have not be identified. So, my current plan is to restart the project using the 200 chassis photos I took before I touched anything. I think I can reproduce its original condition (from the previous restoration), and recheck every connection and component. This could take a few weeks. Hope you all will be there when I start posting again.

Thanks for all the help so far.
Winky.

Hello again. I've spent a lot of time ensuring that this set is in exactly the same condition as when I acquired it. Also checked the values of 20 original ceramic caps and replaced one disk that showed more than twice the specified capacitance and one with possibly overworked leads. Also repaired and reinstalled the original horizontal size pot. Other than replacing defective parts and upgrading parts to comply with advice from this forum, the set is exactly the same as when I bought it.

Now, to address one issue at a time, please consider V15, 6SL7, Balanced Vertical Output. I have inconsistent voltage readings going back to when I first started working on the set. Now, rather than trying to describe my difficulty in reading the voltage, here's a quick video of the multimeter on one plate and one grid.

https://live.staticflickr.com/31337/51807258885_1ec78fa437_m.jpg (https://flic.kr/p/2mW2K8t)Adm 17T12 9015 V15 Jitters (https://flic.kr/p/2mW2K8t) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

I checked it with another meter and with another tube, but both grids, both plates, and one cathode still give the same result. What might cause this phenomenon?

Here's a link to the 17T1 schematic:
https://flic.kr/p/2mv3Wrm

The plate voltage for the 6SL7 comes from the HV supply thought a string of voltage dividing resistors. If the RF HV supply isn't working properly or any of those resistors are off, you can get strange results. Like the voltage may fluctuate with the screen brightness if the HV rectifier tube is weak.

Thanks. I've been looking things over. Retested the 1B3 and even though it's quite strong, I tried switching out another strong 1B3. To no avail. I'm rechecking the resistor chain(s) and everything connected as if I've never seen it before.

Possibly your dmm is measuring the dc value plus the instantaneous value of ac vertical sweep voltage present on the tube elements mentioned. :scratch2:

Do you have an old meter with a needle (slower response time) such as they likely used when making the voltage measurements in these ancient service documents?

jr

1. Regarding the HV supply to the 6SL7, the circuitry is correct and all components are the right values. I followed the voltage from the tube back through the resistor chain until I reached 500V at R73. The voltage readings were still fluctuating.

2. Regarding "instantaneous value of ac vertical sweep voltage" (not sure what or how that happens): I have no analog meter. But wait--I do have a 15 volt panel meter! I set the needle at 1 volt so I could see negative deflection, checked the grids and cathodes, then reversed the leads and repeated the readings. The readings were perfectly steady: G1 1.5V, G2 zero, K1 zero, K2 4.5V. So, does that mean the vertical sweep voltage is the cause of this issue, and I can ignore the irregularity of the voltages?

“-I do have a 15 volt panel meter! I set the needle at 1 volt so I could see negative deflection, checked the grids and cathodes, then reversed the leads and repeated the readings. The readings were perfectly steady: G1 1.5V, G2 zero, K1 zero, K2 4.5V. So, does that mean the vertical sweep voltage is the cause of this issue, and I can ignore the irregularity of the voltages?”

Perhaps... the ac voltage (vertical sweep signal) may be disrupting the measurement of the dc voltage, as your fast response dmms may be sampling the dc voltage as well as the value of the ac signal at the instant(s) the samples are taken.

Or perhaps the dmm is attempting to auto-range to track the varying voltage :scratch2: .

On the other hand, the jumping could be caused by a noisy resistor in the hv circuit (popcorn noise), but it seems that your panel meter would have indicated fluctuations.

Do you have a high voltage probe?

jr

Yes, I would think it's the sweep voltage causing those readings. It's a pretty large sweep sawtooth wave on the plate and grid.

High voltage probe-no. I should mention that with the dmm set for AC, when reading what should be 300VDC, then I get the erratic reading in the neighborhood of 30 volts-whereas I would usually expect less than one volt.

Popcorn noise? Is that audio? I have been getting some crackling noise (with no signal) which I didn't notice previously. To rule out noisy resistor, I could do a temporary switch of ALL suspects if you could tell me which ones to do.

Thanks. I'd better leave it that. I can't deal with much more than one thing at a time.

30 volts fluctuations, or 30 volts signal?

Can’t point out a particular resistor, any can become noisy/erratic.... high meg ohm resistors are likely the worst offenders.

je

30 volts signal--fluctuating within the 15 to 40 volt range. Nearly all of the resistors in the megohms have been replaced with new. I may start replacing the old ones to see if that helps. Beyond that, I have no direction to go with this project.

30 volts signal??? is this measured on pin 5 and/or 2 of the 6SL7? I woud expect hundreds of volts of vertical sweep signal. :scratch2:

jr

Sorry. I wrote this reply earlier but apparently failed to post it.
Repeated those readings several times with similar results for the plates, pins 2 & 5. The readings are from numbers erratically flashing on the meter for less than half a second. Always ranging from 10V to 65V when the meter is set for AC. (Actually, one time I got steady readings of .8V and 1.0V, but the set wasn't turned on.)

Interesting! what do you see on the screen while you make this measurement?

I’m really scratching my head on this one!

jr

On the CRT? Nothing! All the rear controls are set a mid-range. Without more brightness there is nothing on the screen. Most recently, with a lot of adjusting, I could see an oblong blob in which you tell, if you knew what you were looking for, that the TV was trying to show of a test pattern.
Thanks for sticking with me. I'll have to pick this up tomorrow morning.
Winky, "The Eternal Novice"

OP can you repost the schematic you're using with this repair so I can follow along? I'm have quite a bit of confusion which schematic we're using.


It would be a good idea to pick up a regular multimeter. Even a cheap harbour freight / hardware store grade one. They deal with some measurements that a DMM is just too sensitive to get proper readings compared to the schematic.

This is the 17A1 schematic from Wallace-Telaides:

https://flic.kr/p/2mv3Wrm

The set I have is a 17T1 chassis. There were relatively few of these made compared to the 19A1 chassis. They're very similar, but the 17T1 has some additional circuits and some production changes. The catch is that the previous restorer probably used a 19A1 schematic. Apparently they knew what they were was doing. It's a sloppy restoration, but it worked when I got it. I'm trying to replicate what the previous restorer did.

Here's another link that may be helpful. It's the 17T1 schematic overlaid on a 19A1 schematic. Printing that's only black (not black with red overprint) indicates a difference between the two chassis.

https://flic.kr/p/2mv7qkt

Thanks for the tip about an analog meter. It never occurred to me that they still made those.

This is 13 seconds of a test pattern video from 09 Jan 2022:

https://flic.kr/p/2mY1fbd

The four following links show one second of the video frame-by-frame. The time between each image is approximately .029 seconds.

Frames 1-9
https://live.staticflickr.com/65535/51829483166_8eb2114b18_m.jpg (https://flic.kr/p/2mXZDCJ)Adm 17T12 9031 01-09 (https://flic.kr/p/2mXZDCJ) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Frames 10-18
https://live.staticflickr.com/65535/51829599208_3989402ed2_m.jpg (https://flic.kr/p/2mY1f8s)Adm 17T12 9032 10-18 (https://flic.kr/p/2mY1f8s) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Frames 19-27

https://live.staticflickr.com/65535/51830207465_72f65008e9_m.jpg (https://flic.kr/p/2mY4mWD)Adm 17T12 9033 19-27 (https://flic.kr/p/2mY4mWD) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

Frames 28-36
https://live.staticflickr.com/65535/51829599168_dc9368daa1_m.jpg (https://flic.kr/p/2mY1f7L)Adm 17T12 9034 28-36 (https://flic.kr/p/2mY1f7L) by H Boyars (https://www.flickr.com/photos/36873716@N03/), on Flickr

That is very interesting how it goes from a stretched vertical to a full collapse and back at random like that.

I would be looking with a fine toothed comb in the vertical oscillator circuit.

I'll have to put more thought in on this one.

I would start with the power supply to the vertical circuit.

I think, unless you are very lucky and stumble onto something, you are going to have to get some more test equipment.
Many times when something is seen on a TV screen it will give a more definite cause of a problem and a scope will not be necessary. Where the image is distorted in both the horizontal and vertical directions however diagnosis is very hard. A scope would straighten things out rather quickly.
I believe your meter was trying to follow a moving target when looking at the vertical output. An interaction between the measuring cycle of the meter and the vertical signal.
Normal trouble shooting methods would look at the power supply to the suspected circuit stage first, however in this case the power for the vertical output originates in the HV CRT supply (after going through the voltage dividers). You can't measure the HV without a HV probe for your meter.
It looks to me that some supply or something else is cycling up and down over a second or two.

Definitely looks like a noisy/erratic power supply problem.

Can you see/hear any evidence of arcing/corona discharge in the HV supply and related components including pots and resistors as well as capacitors?

Is the low voltage supply stable and noise free (audio ok?)

Very nice video and photo work.:thmbsp:

jr