Let's dig in and get this TV working! If you'd like access to support the channel and gain access to bonus content, please consider becoming a Patreon here: / bandersentv
That transformer salvaged from a parts chassis works quite nicely! The team of engineers who designed this set likely didn't anticipate some of them to be still operating in the 21st century.
Wow Bob, your knowledge of the circuits, how they play into the actual outputs, and knowing exactly how to troubleshoot is amazing! I love watching your logical and methodical approach and the resulting gratification of expected positive achievement. Great job getting this old girl functioning with a minimum of parts and effort!
There were many cases I found when the H osc tube-6SN7- would no longer work for it's function, but you could swap it with another 'SN7 from the vert. circuit ant it would work just fine. Also for some reason, I found that sometimes one had to go through several new SN7's to find one that would work in the circuit. This was mostly from the "Asian Imported" tubes, but sometimes the US made ones. Many of the "discounted' tubes sold in the back of the magazines were a different matter. "Set tested" meant they were put in a set right next to the transmitters in NYC and they would work. ( TV techs in NYC I knew said the sets would even work with dead tubes or even the tube pulled out!) Often they were "Hot Shot" Over voltaged on the filament to bring up the emission enough they would test good. The 'Guarantee" meant nothing. I bought some 6CB6's that showed short and they sent them back as " No problem found". (They did make good .22 targets, as they were good for nothing else.) I have found that the MicaMold caps are all failing also. I fought a H sync problem for 2 days and replaced them with new CDE epoxy dipped micas to solve the problem. The other tech had a tuner problem he fought for over a week and finally listened to me and replacing the caps solved the problem. I had tested the MicaMold caps with 3 different cap testers and they passed just fine with capacitance and voltage tests. Even on a Sencore LC53, A Sprague Tel-ohm 3 or 5, and eye type testers, plus ohmmeter tests. Even the NOS MicaMolds the shop had passed the tests just fine but were bad from age or ?? I always replaced all the old 'lytics and wax, plastic & bumblebee caps too.- IRC that set had split sound and those were a real PITA to get right. Also your CRT has a phosphor burn in the center.
I find it interesting that the vertical oscillator section along with o/p trans is contained in its own little sub-chassis but the 6k6 o/p tube is on the main chassis.
I am a big fan and follower of your videos (I have about 6 TV's (two are consoles: 51 Zenith and 68 Sylvania, many other B&W sets I want to tackle). One point I would make, there is a difference between guitar amp people and audiophiles. Guitar people want distortion that is unique to tubes and audiophiles don't (usually single ended designs with no negative feedback that you normally have in ultralinear tube circuits). Keep up the good work!
Funny you should mention the issue with Audiophiles wanting distortion & guitar players wanting it: I had a shop in Denver for 10yrs about 10yrs ago (Mars Amp Repair). I was applying for Line6 warranty and one of the test equipment requirements was a distortion analyzer. I called the rep to be certain this was true & he confirmed it. I asked him (jokingly) if they wanted a distortion analyzer to determine if the amp had ENOUGH DISTORTION! We both got a good laugh about that...I never bought an analyzer & of course never needed one. BTW at the time i was referring to the digital distortion setting that Line6 had on their Spider amps called 'INSANE' where it introduced so much distortion that pretty much anyone could pick up a guitar & just pick the strings anywhere in any key and it sounded like MEGADEATH!
@@whatleyglen7148 For a long time (longer than I wanted to admit) I thought that guitar players liked the clean sound of tubes. The band Boston used a defective effects pedal for their "Third Stage" album. In his own words: "No Synthesizers! That’s right! Honest! And no violins either (so how do you make thunderstorms without a synthesizer? A twenty-year old Vox Tone-Bender with a bad transistor). In other words, the Boston sound is powered by old, straight ahead rock-n-roll equipment, as opposed to midi-interconnected-computer-sequenced synthesizers. Tom Scholz" Funny how there are so many "Off label" uses for gear.
@@bandersentv I believe that 1B3 is original too. Low hours set is my guess. I have a 621TS with an almost complete original tube set that works great. I just cleaned and recapped it and it powered right up.
Instead of measuring the voltage waveform at the plate of the HOT, what if you insert a precision 1%, 1 ohm resistor in series with the plate, then measure the voltage across that? From what I’ve seen, the plate current is usually about 120-180 mA, so across a 1 ohm resistor, that should be about 120-180 mV or so. Essentially reading a current waveform instead, using the scope as an ammeter. 🤔
A few issues with that. One, you need to cut the HOT plate cap lead. Two, you still have a lot of voltage on your test leads with respect to ground. If one of the leads came near the chassis, it could arc over. Reality is I've never needed to measure it. Once you have a raster, you can observe the image to see if circuits are working properly.
No, it can handle up to 18,000 volts. It was designed specify for use with sets like this. The focus coil interferes with the image. I'll show this in the next installment
@@bandersentv OK, you know a lot more about tube TVs than I ever will. When I was around 7 until my teens I would hang out at the local TV repair shop. I learned a lot and would tell my friend if the horizontal oscillator was running. That, as well as running to the corner store for his coffee and snack, were my duties. It was the mid to late '50s so I saw TVs newer than the ones you work on. Not many had big 60 cycle transformers in the power supply.
I couldn't help noticing the actual test CRT has some air bubble inclusions in the glass... at least that is what it looks like. If the image collapses intermediately for half a minute (or at least a few seconds) or so, could that be attributed to dropping high voltage, Bob?
Probably, also an ion burn and scratches. It's been used a lot. Air bubbles are fairly common in early CRTs. Not sure what you mean by collapse? Just the vertical or no image at all?
The picture is just fine one minute, the next it seems to shrink and become garbled towards the vertical center of the screen before collapsing almost to nothing at the bottom of the crt... after a while the picture would just as unexpectedly "bloom up" again as if nothing happened... it repeats ad infinitum. It's a strange phenomenon and I was wondering if you ever experienced something similar and what was the cause?
I was going to ask if were possible to repair transformer ,UNTIL,I saw all that awesome tar.Still would be interesting to melt that stuff away and see where it broke(wire),perhaps cause shorted /leaky C146B?
I ended up rewinding the opened vertical blocking coil in my Emerson and it took way too much time. I think it was a few days overall. Worse yet it started acting up again later, probably a shorted turn. It's probably my fault for trying to splice and reuse the old wire. For around the price of new enameled wire you can buy a "new" transformer and avoid the hassle.
@@bandersentv Probably a "universal" wound (criss crossed weave).And I mentioned the C146B since it was in 6sn7 cathode circuit defective causing high current thru tube? taking out coil possibly.
Love your content Bob, im from the UK but find your work on vintage US TV's fascinating and like your restoration approach, not too anal but very methodical, you've probably been asked this before but what is with the Anarchist looking symbol scar on your hand?
That transformer salvaged from a parts chassis works quite nicely! The team of engineers who designed this set likely didn't anticipate some of them to be still operating in the 21st century.
Wow Bob, your knowledge of the circuits, how they play into the actual outputs, and knowing exactly how to troubleshoot is amazing! I love watching your logical and methodical approach and the resulting gratification of expected positive achievement. Great job getting this old girl functioning with a minimum of parts and effort!
Looking at some of those tubes, I can hear Shango's voice saying "Baked!" 🤣
LOL That's what I heard in my head as I examined them too.
There were many cases I found when the H osc tube-6SN7- would no longer work for it's function, but you could swap it with another 'SN7 from the vert. circuit ant it would work just fine.
Also for some reason, I found that sometimes one had to go through several new SN7's to find one that would work in the circuit. This was mostly from the "Asian Imported" tubes, but sometimes the US made ones. Many of the "discounted' tubes sold in the back of the magazines were a different matter. "Set tested" meant they were put in a set right next to the transmitters in NYC and they would work. ( TV techs in NYC I knew said the sets would even work with dead tubes or even the tube pulled out!)
Often they were "Hot Shot" Over voltaged on the filament to bring up the emission enough they would test good. The 'Guarantee" meant nothing. I bought some 6CB6's that showed short and they sent them back as " No problem found". (They did make good .22 targets, as they were good for nothing else.)
I have found that the MicaMold caps are all failing also. I fought a H sync problem for 2 days and replaced them with new CDE epoxy dipped micas to solve the problem. The other tech had a tuner problem he fought for over a week and finally listened to me and replacing the caps solved the problem.
I had tested the MicaMold caps with 3 different cap testers and they passed just fine with capacitance and voltage tests. Even on a Sencore LC53, A Sprague Tel-ohm 3 or 5, and eye type testers, plus ohmmeter tests. Even the NOS MicaMolds the shop had passed the tests just fine but were bad from age or ?? I always replaced all the old 'lytics and wax, plastic & bumblebee caps too.-
IRC that set had split sound and those were a real PITA to get right. Also your CRT has a phosphor burn in the center.
Sure, test CRTs do not have ion traps. They all get burns.
With my Emerson the opposite was true with the SN7s: one tube wouldn't work right in the vertical but would work right in the horizontal.
Hard to believe those electrolytics from the late 40s are still good!
I find it interesting that the vertical oscillator section along with o/p trans is contained in its own little sub-chassis but the 6k6 o/p tube is on the main chassis.
I think that is legacy from the earlier RCA 630TS which has more circuitry in this area. This is a simplified design with the same basic chassis.
I am a big fan and follower of your videos (I have about 6 TV's (two are consoles: 51 Zenith and 68 Sylvania, many other B&W sets I want to tackle). One point I would make, there is a difference between guitar amp people and audiophiles. Guitar people want distortion that is unique to tubes and audiophiles don't (usually single ended designs with no negative feedback that you normally have in ultralinear tube circuits). Keep up the good work!
Funny you should mention the issue with Audiophiles wanting distortion & guitar players wanting it: I had a shop in Denver for 10yrs about 10yrs ago (Mars Amp Repair). I was applying for Line6 warranty and one of the test equipment requirements was a distortion analyzer.
I called the rep to be certain this was true & he confirmed it. I asked him (jokingly) if they wanted a distortion analyzer to determine if the amp had ENOUGH DISTORTION!
We both got a good laugh about that...I never bought an analyzer & of course never needed one.
BTW at the time i was referring to the digital distortion setting that Line6 had on their Spider amps called 'INSANE' where it introduced so much distortion that pretty much anyone could pick up a guitar & just pick the strings anywhere in any key and it sounded like MEGADEATH!
@@whatleyglen7148 For a long time (longer than I wanted to admit) I thought that guitar players liked the clean sound of tubes. The band Boston used a defective effects pedal for their "Third Stage" album. In his own words: "No Synthesizers! That’s right! Honest! And no violins either (so how do you make thunderstorms without a synthesizer? A twenty-year old Vox Tone-Bender with a bad transistor). In other words, the Boston sound is powered by old, straight ahead rock-n-roll equipment, as opposed to midi-interconnected-computer-sequenced synthesizers. Tom Scholz" Funny how there are so many "Off label" uses for gear.
1:14 That Damper Tube is from the 43rd Week of 1948. I believe the dash between those numbers signifies that it IS original to the set.
Amazing that it lasted so long.
@@bandersentv I believe that 1B3 is original too. Low hours set is my guess.
I have a 621TS with an almost complete original tube set that works great. I just cleaned and recapped it and it powered right up.
at 18:45 I can hear that whistle of the old set, its a nostalgic sound for me, its also surprising your mic captures that
You have good ears. All I can hear is the scope fan.
Thank you for not shot gunning ! I just wish the newbees didnt. Ends in many sad stories.
Zeno
Having spare parts saves the day. Burning the after midnight oil with Cannon on the TV? Doing good so far Bob!
Thanks. Yes, MeTV has led to some bad habits. Star Trek, Alfed Hitchcock, Mannix and Cannon if I'm really motivated.
very enjoyable
Thank you. It is a welcome change after all the Philco Predictas.
Instead of measuring the voltage waveform at the plate of the HOT, what if you insert a precision 1%, 1 ohm resistor in series with the plate, then measure the voltage across that? From what I’ve seen, the plate current is usually about 120-180 mA, so across a 1 ohm resistor, that should be about 120-180 mV or so. Essentially reading a current waveform instead, using the scope as an ammeter. 🤔
A few issues with that. One, you need to cut the HOT plate cap lead. Two, you still have a lot of voltage on your test leads with respect to ground. If one of the leads came near the chassis, it could arc over. Reality is I've never needed to measure it. Once you have a raster, you can observe the image to see if circuits are working properly.
Is that zenith chassis on the shelf a parts chassis? If so I could use the channel indicator if you'd be willing to sell it. Thanks
I think the high voltage is too high for that 5" CRT. When the picture stops rolling, it blooms because the voltage goes up.
No, it can handle up to 18,000 volts. It was designed specify for use with sets like this. The focus coil interferes with the image. I'll show this in the next installment
@@bandersentv OK, you know a lot more about tube TVs than I ever will. When I was around 7 until my teens I would hang out at the local TV repair shop. I learned a lot and would tell my friend if the horizontal oscillator was running. That, as well as running to the corner store for his coffee and snack, were my duties. It was the mid to late '50s so I saw TVs newer than the ones you work on. Not many had big 60 cycle transformers in the power supply.
I have the set I grew up with 1949 12 inch picture rca console.Hor.osc not ru nning now.Crt is shot. Takes a 12Lp4.
I couldn't help noticing the actual test CRT has some air bubble inclusions in the glass... at least that is what it looks like. If the image collapses intermediately for half a minute (or at least a few seconds) or so, could that be attributed to dropping high voltage, Bob?
Probably, also an ion burn and scratches. It's been used a lot. Air bubbles are fairly common in early CRTs. Not sure what you mean by collapse? Just the vertical or no image at all?
The picture is just fine one minute, the next it seems to shrink and become garbled towards the vertical center of the screen before collapsing almost to nothing at the bottom of the crt... after a while the picture would just as unexpectedly "bloom up" again as if nothing happened... it repeats ad infinitum. It's a strange phenomenon and I was wondering if you ever experienced something similar and what was the cause?
@@TechneMoira If it is a more modern TV, I would suspect the power supply. Especially if it is switch mode.
Pretty much knew it was they blocking transformer, they fail a lot, it was bad in my arvin 9219-cm-uhf television
I was going to ask if were possible to repair transformer ,UNTIL,I saw all that awesome tar.Still would be interesting to melt that stuff away and see where it broke(wire),perhaps cause shorted /leaky C146B?
With such high resistance values, there must be many, many turns of thin wire. I suspect it would be very difficult to repair.
I ended up rewinding the opened vertical blocking coil in my Emerson and it took way too much time. I think it was a few days overall. Worse yet it started acting up again later, probably a shorted turn. It's probably my fault for trying to splice and reuse the old wire. For around the price of new enameled wire you can buy a "new" transformer and avoid the hassle.
@@bandersentv Probably a "universal" wound (criss crossed weave).And I mentioned the C146B since it was in 6sn7 cathode circuit defective causing high current thru tube? taking out coil possibly.
Love your content Bob, im from the UK but find your work on vintage US TV's fascinating and like your restoration approach, not too anal but very methodical, you've probably been asked this before but what is with the Anarchist looking symbol scar on your hand?
I was curious about that as well. It might be a remnant of a tattoo he had gotten in his younger years that he decided to remove.