Sylvania Superset Update
 

I replaced (what I assume is) the boost cap as the old one blew out its bottom and was so far gone one of the leads was broken off on the inside of the cap, I reflowed all the joints on sand around the flyback, I cleaned the inside of the housing. I included a couple before and after photos.

The speaker buzz is still occurring in a slow pulse (approximately 10 seconds of no buzz, 20 seconds of buzz), there were no other visibly bad caps on the board, so I may just replace a bunch in that area of the circuitry.

And while I was cleaning the inside I knocked the convergence & purity rings out of position with my dumb limbs. I ordered an hdmi to RCA converter so I can try to fix my screw up there running test screens off my laptop.

Last thing, I didn't touch the pots on the main board for picture/brightness/color etc, but on the front pots I'm running it with picture & color roughly 2/3 up, and the brightness pot almost all the way off. (I can turn brightness & picture all the way down and still seem an inage, although probably not in a really bright room).

Anyway I just wanted to post this and say thanks again for your help. Overall I'm pleased as punch.

-Sean

First off, if this is an update of another thread, it should be posted there.

Regarding the picture with the red smearing to the right of the forehead, and brightness all the way off, that's a clear indication that the CRT bias (screen controls) are set wrong and the red video output is going into saturation on highlights. Going through the setup procedure should fix it.

Sorry I'll try to get this thread deleted and this response in the proper place once I figure out how.

As for the red smearing it's way better now that I've replaced the busted capacitor, but it's there if I crank the color pot all the way up, I'll have to find a setup how-to and follow along.

In the mean time, any thoughts on a slow pulsing buzz coming from the speaker?

In the absence of setup instructions, you can take a stab at it.

If this set has a SETUP switch, switch to setup mode, which should give a single horizontal white or gray line. Turn down the G2 (screen) R,G,B controls until you just barely see a neutral dark gray line. Switch out of setup mode and adjust the brightness control as needed.

If there is no setup switch, try turning down the brightness some with the G2 (screen) R,G,B controls and then turning brightness back to normal with the brightness control. You may end up with a color tint in the shadows; fix that by turning down the predominant one or two of R,G,and/or B.

Note: some sets had a jumper to set the G2 range to higher or lower.

About the buzz - sorry, no idea.

Thanks i'll give that a try. And sorry I can't figure out how to delete this thread.

Even with bad setup, a strong tube won't flare like that except for the auto-AKB twin focus models like Zenith made when the G2 was set too low.

Remember that the CRT heater voltage is sourced from the fly, so if your HV is low, your filament voltage will be low in a proportional amount. Even an otherwise strong tube will flare with low filament voltage.

With a TRMS meter, measure the filament voltage (AC) at the CRT socket to see if you're getting 6.3V. Don't use an analog meter and don't use a meter that isn't a true RMS type because your AC is at the horizontal rate, not 60hz.

If the voltage is low, your HV is also low, and that could have to do with the retrace capacitor you changed (as well as other things such as B+)

John

The jug sure looks soft especially the red. If the G-2 & heater check out we can give you a cheat. I dont think its a Zenith EFL, IIRC NAP never used it.
Between NAP, RCA / Thompson & Zenith they built almost all US tubes
and many for JA & Korean sets. May be one reason neither had EFL's.

73 Zeno:smoke:
LFOD !

Hey,

Okay, the SAMS lists the filament voltage at 22V. I'll check. Also I'm not quite sure what you mean by "B+".

As for the softness of the image, I did knock the convergence rings out of place with my arms while I was cleaning dust out of the cabinet (accidentally, of course). I haven't tried realigning them yet. The picture was much sharper before then, smearing aside.

Edit: I just checked the multimeter I have at home, and it's not TRMS, so I'm going to have to wait until I get back to work, and see if the ones we have there are.

Edit2: In regards to the misaligned convergence rings, I did position them back close to how they were, but obviously I didn't do the best job.

B+ is basically a universal electronics term for the power supply voltage(s).

It dates back to the tube battery radio era. Back then the heaters would be powered by an A battery, the plates would be powered by a B battery and the grids would be biased by a C battery. Eventually they figured out how to make the B battery bias the grids with resistors, then they figured out how to make AC power supplies do the work of batteries (causing battery radio bonfires in many cities in the late 20s), but the A and B designations stuck...A fell out of use with the transistor and certain solid state devices started using VCC, VDD, VBB and or supply design voltage as designations, but B+, and B- are still in common use, and far from dead.

Your useless trivia lesson for the day...

Not completely useless, definitely interesting.

Tom gives a good run down on B+. One of the terms you will CONSTANTLY see
used here. If you look at any little radio the battery is the B+ source.
On your set odds are the heater is NOT the problem. If the G-2 is
set right look at this:

The pix is bad when the set is cold but gets better with time.
The pix improves with reduced brightness & contrast.
Thats all assuming the 200 V DC for the three video outputs is good.
At this point a manual would be needed. Any NAP chassis will work if
a close match ( C-5, C-6 etc. ).

73 Zeno:smoke:
LFOD !

Both things you suggeted is right. The picture is worse at the beginning, but gets better over time; and the picture is a little clearer during dark scenes (and turning down brightness/contrast. I set it at 2/3 contrast, almost 0 brightess, since that gave me a decent picture, and the brightness isn't necessary to see anything.) Not to say that at any point the picture is terrible, just a bit blurry. ALSO I set the Color pot to like 2/3 as well. All the way up is way too much color to me.

I have the appropriate manual for this TV + Chassis, unfortunately it's over the file size limit, and even making a compressed file leaves it over the limit. I'll have to find an alternative way to share it.

If anyone else has a smaller file manual, it's a 26C8 Chassis.

Edit: I haven't checked the G2 yet, but this is what it's doing at its current settings.

It's not 22V, it's 6.3VAC on that tube. I literally worked on a thousand of them. Sams misprint I suppose.

The flaring in your picture is not a convergence issue. Misconvergence will show as a clearly defined border of color, not a general lazy flaring off the picture on brighter images.

Hopefully, your HV is low, which can happen if the retrace capacitor is too high in value compared to the original (it must be an *exact* value - no upping by 10-20% like other caps allow). If the HV is low, your filament will be low and will cause that general flare off the bright on-screen objects.

As tubes get older, they become more sensitive to filament voltage than when they'r new. Most CRT testers of the time had a "life" test. Pushing the "life test" button would reduce the filament voltage a few tenths up to a half of a volt. A strong tube would barely lose emission but a weak tube would drop into the "yellow" or "red" area.

Ordinarily, a flare like that is a soft tube, but since you changed the retrace cap which has a big effect on the HV (and therefore filament), checking the filament voltage at this stage is the best thing to do.

If the voltage is 6.3 (not 6.1!) with a TRMS meter, your tube is soft and your repair was fine. If the filament is low, revisit your retrace cap change and double check the value.

John

Okay, i'll do that. Thank you for the explanation. Sometimes the terms used don't translate in my head properly.

I checked the filament voltage and got 2.2 (or 1.5 if I used the low-impedance setting). Both seem wildly incorrect. Would the retrace-cap value being low also drop the voktage? I know I got some cheap ones, but I'm not certain what the effects of high capacitance vs low capacitance are in the circuit.

Also I'm assuming I measured correctly. I measured across the two filament joints (in my case pins 9 &10).

Thanks in advance.

Edit: I also tested the voltage within a couple minutes of turning it on rather than waiting until the image became clearer. If that matters.

You must use a True RMS (TRMS) meter, not an ordinary multimeter (average reading), because the voltage is pulsed.

I used a Fluke 114, which claims to be TRMS. Unless there's a way to turn on and off TRMS, I did read the manual, but couldn't find anything that said that so I assumed the AC setting would work as TRMS as default. But yeah it said 2.2 and would waver around there between like 2.17 and 2.29.

I don't think the tube would even light at 2.2V. The meter is on "AC" (~), correct?

Have you verified the meter? Try it on your wall plug to see if you are getting about 120VAC.

If the retrace cap is low in value, the HV and filament would be high.

I don't recall the pin numbers of the filaments, but they should read very low ohms (power off) across the filament pins (couple of ohms) if you are on the right pins.

Since sweep is regulated, the voltage will be the same hot or cold.

John

Hey John,


Yeah the meter gets calibrated everyb6 months for my works IDK certification stuff, I set it to AC for sure, I even did it again after watching a movie a couple hours later just to confirm.

The pin numbers are 9 and 10. I measured across those.

I also included pictures from the manual of the circuitry and board.

I feel like I've clearly done something wrong, but I don't know what it is.

Hmmm - if you are reading different voltages with the high and low impedance settings, it seems to me the filament voltage source may actually be open circuit somewhere and you may be just picking up some capacitively coupled pulses - check the filament supply for continuity.

22 volts is normal IF you look at it with a scope.
They are hoz spikes from the FBT. The meter is trying
to average what it sees. Different meters may show different
readings.

73 Zeno:smoke:
LFOD !

Hmm. Well it'll be until next week that I get access to that multimeter again. I should ask and see if work has a scope I could borrow as well. I'll also do continuity checks all around the board.

I've never seen a Fluke TRMS meter not read accurately on scan derived filaments, but then I've never used that particular meter either..

If you can borrow a scope, you can measure the p-p of the pulse, should be 22V.

What was the value of the original retrace cap and what is the value of the one you installed? (I might have missed that)


John

The original cap value was 22 uF 250V, I bought a cheap pack of 10 at the same value, I didn't think to check before I installed, but I'll check the others maybe one is real close to the original value.

The 114 is an electricians model...some compromises may be made to reduce/eliminate ghost readings.

https://www.fluke.com/en-us/product/...ters/fluke-114

Looks like TRMS readings are only specified to 1 khz... might be way off at 15 khz. :scratch2:

jr

That's not the retrace cap - that's the B+ bypass cap off the flyback. The retrace will be a 1500V film cap. If B+ bypass cap opens, the pulse from the horiz output will feed back to the regulator and cause start up and shutdown. While it's possible, I don't see retrace caps fail in anything but a binary fashion (good or bad), but I do remember one particular RCA that used a retrace cap with two or more sections in series. One section shorted, the value of the cap increased, the HV went down and the horizontal scan went very wide. That was the only one I remember that went off value.

Sounds like you're down to proper set up and a weakish picture tube.

John

yeah, man your tube is worn got to face it. now adjust you contrast down to where it does not smear and just watch it. those nap sets always smear when contrast is turned up. there were like that out of the box. to me the picture was always not the best.

yeah, man your tube is worn gotta face it. when brightness is set where you have a good bright picture and the contrast is set at a picture that is acceptable picture. then it starts to smear and you turn it down and you still cant get a good picture tube is worn. one of the pictures posted looked like that contrast was to high adjust it and it would decent picture.

I kinda figured. It got used heavily while I was growing up. I'm really only using it to watch VHS tapes about once a week (maybe less if I'm busy) anymore. The picture is pretty good with contrast at like 2/3 turned up and brightness up a little bit, I think I need to adjust the focus, as the image was a bit crisper before I replaced the cap I did.

As for the film cap that JohnCT mentioned isn't bulged or anything, but I'll keep a lookout for one on ebay, who knows. I did find a nos PTC thermistor for the degaussing circuit.

I'll triple check the filament voltage when I get a chance, and I still have to figure out this audio buzz issue maybe a worn cap or something in the audio circuit.

I was fascinated by furniture looking sets like this one.

I wouldn't. Those caps pretty much are good or bad. If the retrace cap was causing low HV and filament, your horiz sweep would also be too wide. Now, being a raster scanned analog TV, these tended to be a bit overscanned anyway so customers didn't complain about shrinkage.

John

Yeah, man. I think tvs like this are super cool. Mine is almost blemish free too. Except my dumbass set a bottle of acetone on it a year or two ago and have a spot where the wood/design is screwed up.

Okay. I gotta be honest, as is I'm pretty happy with it. It is a big improvement over how it was before.

Now that I've said that, I know it's old and tired, and with light usage, if I can get a couple years out of this tube I'll be pretty happy. If I found a 26" CRT, would it be feasible to swap the internals into this cabinet? And I mean tube, chassis, and whatever else makes the donor tv operate.

I'm not sure if the curvature of screens changed a whole lot over the years. I know Sony Trinitrons were cylindrical, and that eventually there were flat screen crts.

If your TV is a 25", a 26" won't match the original mask as the 26" was a bit more square and flatter IIRC. Besides the fit, the mounting flanges wouldn't fit the original mask, so you'd have to swap the mask at the same time which is possible with a bit of cabinet fabrication.

Back in the 80s-90s, we used to do custom cabinet swaps. We'd take a customer's 60s or 70s console and gut them, then we'd buy brand new wood table model Zenith consoles and break up the new cabinets to swap out the guts, and that included the entire front mask which was usually held in place by heavy staples nailed into the wood cabinet. Once the Zenith mask was free from the donor and fitted to the original cabinet, we'd remount the new Zenith tube and chassis. There was a frame shop next door to us and they would cut and fit any trim wood to finish the mask to cabinet clearances if required. These looked absolutely factory when done and we got top bucks to do this.

There are a ton of these Philips consoles ( Sylvania, Philco, and Magnavox) floating around for free on FB Marketplace. There's an excellent chance you can find one with a perfect tube for zip, even if it's a plastic table model with the same tube.

John

Hey thanks, John. I'll keep my eye out.

At the very least my model number indicates a 26", but maybe the tube is a more common size crammed in, I'm not sure how to determine that. Either way I'll keep my eyes open for a possible donor.

And also thank you for all your insight, it was very helpful, and I learned a lot.

Sean

one way to tell the size if the tube number starts a63 that's a 25" a66 is a 26" a68 is a 27".

A rad. I looked through the pictures that I had taken, and one does show a66 on the back.

Thanks!

OK that's a 26"