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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sat 09, 2015 5:29 pm 
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The manual lists test points for voltages. It says to connect the probes "between the test point and ground". Is "ground" the chassis?


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sat 09, 2015 7:03 pm 
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Location: Wyoming, Michigan
There's probably a curly-fry tube under that bulb but make sure you're using a CFL and not a LED (or incandescent). Better yet, grab one with a more open construction and try again.

Your original photo on page 1 shows an electromagnetic-type beam bender (ion trap magnet). Those are especially difficult to position, and often are electrically open. They sometimes double as a filter choke for other circuits. Unless you know it was correctly placed and unless you know you replaced it in the exact same position (or you know it's placed in the sweet spot by other means), and unless you know it's still electrically producing a magnetic field, you should expect a black screen up front. During this troubleshooting phase, I would grab a permanent-magnet type unit and use it to get a decent picture, then if you want, go back to troubleshooting the electromagnetic one. But I have a dozen spare ion trap magnets laying around, you may not.

Also if the curly-fry-bulb test fails you should also expect a black screen, but I'm of the opinion that the HV should be present if the deep purple glow is in the tube (the glow is the result of the HV), so there may be some conflicting findings. Maybe the CFL you are using (with the extra enclosure around the fluorescent tube) doesn't behave the same way as the one in the YouTube demo.

I've never discharged any capacitors in a TV set except the CRT (remember it doubles as a capacitor). It may be a universal statement that all TVs in all 1940s era sets like yours all naturally bleed down the capacitors in very short order after power is disconnected. But perhaps there are counterexamples. The opposite is true of the CRT, it can stay charged for hours or days.

Ground is chassis unless otherwise stated. Sometimes "Earth" is stated if true ground is needed. But this can confuse the British among us.

Test points for voltages are tested with power applied. Test points for resistance are checked with the power turned off. Safer to do the resistance checks first. I'll see if I can get my hardcopy digitized for you later today. I'll be visiting a friend with a scanner.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sat 09, 2015 7:41 pm 
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Thanks WeekendHacker. I wondered about the covering on the CFL bulb, but it is only plastic. I don't have a naked curly CFL. I do not think I have an ion trap magnet. Then again I have no idea what an ion trap magnet is or looks like, so how would I know anyway! :)

I went ahead and commenced the power supply (section 1) troubleshooting as laid out in the manual. At point 1 I get 135DC, which is low, so I move on to step 2. However, I don't know how to read AC on the multimeter. Interestingly, when I checked point C the sound went from very dim and staticky to crystal clear. And it stayed that way even after I removed the probe, and even after repeated on/off cycles with the set over the morning. The sound continues to be very clear every time I turn it on. Probing that point popped something into place, it seems.

I have some questions on how to read AC voltage on the multimeter. See photos below.
Attachment:
File comment: Chassis test points.
Section 1 test points.jpg
Section 1 test points.jpg [ 42.6 KiB | Viewed 4191 times ]

Attachment:
File comment: Steps I am following.
Section 1 test guide.jpg
Section 1 test guide.jpg [ 45.89 KiB | Viewed 4191 times ]

Attachment:
File comment: When I touched the red lead to point C there, sound became, and stayed, clear.
Probing point 1C cleared up the sound.jpg
Probing point 1C cleared up the sound.jpg [ 67.96 KiB | Viewed 4191 times ]

Attachment:
File comment: This is what I get for point A at C101. What is this reading? Per the guide it should be 117vAC.
Point 1 A, reading L.jpg
Point 1 A, reading L.jpg [ 61.97 KiB | Viewed 4191 times ]

Attachment:
File comment: This is what I get for point A at C100. What is this reading? Per the guide it should be 117vAC.
Point 1 A, reading R.jpg
Point 1 A, reading R.jpg [ 63.1 KiB | Viewed 4191 times ]

Attachment:
File comment: This is the Focus pot. Is it supposed to be open like this? The black flange on the center piece actually contacts the top of the metal coil, rubbing along it as I turn the control. Is this contact normal? Should this thing have a cover? (it didn't have a cover when I received the set.)
Focus pot.jpg
Focus pot.jpg [ 63.58 KiB | Viewed 4191 times ]


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sat 09, 2015 10:25 pm 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 930
Location: Wyoming, Michigan
I can imagine the HV gathering about the plastic dome of your CFL and discharging into your fingers before ever reaching the glass of the fluorescent tube, but that would be conjecture on my part only. But it nicely explains the glow in the 6BG6 and not at the CFL, so it's my story for now.

Google is your friend. You would need a dual-magnet trap like this (photo courtesy Bob Andersen)
Image

Most sets use a single magnet like this (photo courtesy Phil Nelson)
Image

but it's moot if you don't have a fully-stocked junk box. An even easier option would be to use a 10FP4 or some other test CRT in place of your 10BP4 until the HV and sweep and other issues are wrapped up and then go back to the original 10BP4 and troubleshoot the ion trap circuitry afterwards. But again, you need a well-established workbench.

The test point that you probed to get your sound back probably has a solder joint but from the photo it looks like it doesn't. What solder is there is likely inadequate or was improperly flown (resulting in a "cold" solder joint). Reheat it and flow more solder.

Far right, center, of that same photo there is another 10uF@500V capacitor. You have its long exposed open positive lead soldered to a red wire going off to a terminal strip. It's bad form to leave positive leads of hi-current components exposed like that. Buy a large quantity of spaghetti tubing and heat-shrink tubing at your local hamfest (or Just Radios, Mouser, etc) and cover the plus leads of caps before installing them, then tape or heatshrink the solder joint after. My two cents of course.

I'm seeing 37V and 85V for your meter readings in question. To be sure, measure a wall plug for ~120V and see what the meter reads. If it looks right then your readings above indicate a problem. If not, then the meter is suspect.

I visited the friend but forgot to pack the Sams sheet. Next time. Meantime, the troubleshooting steps you are following are a reasonable plan of attack.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sun 10, 2015 3:47 am 
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Thanks WeekendHacker. I'll check the soldering. There is some there, and I take care to make sure the joints all contact and have solder, but maybe I wasn't putting enough solder on. Or enough heat. I run my soldering iron at 750. Should it be hotter? Maybe I'll give that a try. I do have plenty of heat-shrink spaghetti tubing. I'd been using it when there was some danger of wires being crossed but not usually otherwise. I'll wrap the positive leads for electrolytics from here on out. Should have thought about checking voltage from an outlet or the Variac to see how the multimeter scales work. Duh!


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sun 10, 2015 5:51 am 
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Joined: Jul Wed 08, 2009 12:17 am
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Location: Wyoming, Michigan
Looking at your photos of the test procedure I'm guessing you tested point A twice, each time from the opposite capacitor joints to chassis ground. The test is to check AC across the two points there, not each to ground. The readings you did measure suggest significant leaking of those two caps, which is very common. They are AC main supply noise filters and many of us just remove them, as modern AC is for the most part noise free. Back in the day, not so much. If you want to be faithful to the restoration, replace them with safety caps (Just Radios sells them) which are less of a fire hazard in that application than the yellow film caps you are using elsewhere. If you want to remove them instead, nobody will probably notice or care. As-is, they are a problem if they are leaky, which it seems they may be.

That focus pot is normal. The semicircular coil is the resistance element, the wiper that drags across it forms a variable center tap, the current flow thru the circuit changes depending on the contact point's position along the resistive element. Seems like bad form not to cover it, but it probably gets toasty warm and the designers preferred to let it get air circulation over looks or potential shock/burn hazard to the TV repairman.

Plus, you don't need to worry about focus until you have a picture on your CRT to look at. :wink:


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sun 10, 2015 7:17 am 
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Location: Woodinville, WA USA
WeekendHacker wrote:
replace them with safety caps (Just Radios sells them)
Justradios also has an excellent article explaining these caps:

http://www.justradios.com/safetytips.html

The term safety cap is a little confusing to some people. I usually call them line filter caps, since their purpose is to filter noise from the AC power line. "Safety" refers to the fact that they are designed not to start on fire if they fail. Some of the old caps used for this purpose did indeed fail in an unsafe manner.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sun 10, 2015 3:10 pm 
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Joined: Jan Sat 31, 2015 10:06 pm
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I've resoldered some joints that looked dodgy. I tried 800 degrees but that seemed too hot, so I went down to about 760. One issue is this brown gunk on the terminals, which may be preventing adhesion of the solder. Is it wax? I tried a wire brush and it got some of it, but I'm wondering if what's left is causing problems.

The audio continues to be very, very dim/scratchy and when I touch a probe to nearly any wire - point A, point C, the chassis - it becomes clear. Sometimes it degrades over time, sometimes it does not. I poked physically at some caps to check for bad connections, but a physical poke had no effect on the audio at all, good or bad. But touching one probe lead to the wiring, even without the lead connected to anything, does.

After some measurements, I'm not sure the Power Supply is operating badly. My test results:
Point 1 - expected: 245vDC, actual: 280vDC. Is this discrepancy important?
Point A - expected: 117vAC, actual: 117vAC. Good.
Point B - expected: 720vAC. My multimeter says not to measure over 600 volts. How do I take this measurement, then?
Point C - expected: 345vDC, actual: 345vDC. Good.
Point D - expected: -12vDC, actual: -12vDC. Good. Note: I reversed the leads to get a positive reading on the multimeter. Also, I had to adjust the focus down until I got "12" on the MM, which is really -12 because I reversed the leads, right? Am I measuring negative voltage correctly, by reversing the leads?
Point 1 - expected: (same as above)
Point 2 - expected: 7300vDC. How do I measure voltage this high?

Here are some solder pics. Let me know if you see issues.
Attachment:
File comment: 1C is the lower joint, to the 40/500 cap. After adding solder.
Point 1C.jpg
Point 1C.jpg [ 65.4 KiB | Viewed 4138 times ]

Attachment:
File comment: The connection for the 102 cap at the top left is a typical connection before resoldering.
Before.jpg
Before.jpg [ 50.4 KiB | Viewed 4138 times ]

Attachment:
File comment: After adding solder, and attempting to get around the gunk to achieve a solid connection.
After.jpg
After.jpg [ 52.11 KiB | Viewed 4138 times ]


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sun 10, 2015 6:02 pm 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 930
Location: Wyoming, Michigan
This may help:

http://www.aaroncake.net/electronics/solder.htm

It seems thorough. Your first pic simply looked like there was no solder at all on point C but I surmised that it was just an illusion. Your later pics suggest that you went overboard. It's not the quantity of solder that matters, it's the flow and adhesion.

The brown gunk is bad. Pull a small square of 600 or 1000 grit wet-or-dry automotive sandpaper across all leads until shiny, before soldering. Use clean solder and a clean tip. The tutorial above is clear.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sun 10, 2015 10:05 pm 
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Location: Ann Arbor, MI
Reversing the leads to the meter is the proper way to measure a negative voltage. As for measuring the higher voltages, you probably can't with that meter. One of my meters has an extra input jack that allows it to measure 1000 volts, but it looks like your meter does not have that.

As for the sound coming back when you touch a lead to the wire with voltage on it: When you touch the lead there, there will be a small burst of high frequency signal generated that will be picked up by the circuits in the set. That can
cause enough extra voltage to jump over a bad connection making a temporary weld (a very very small weld.) The bad connection can be within a component such as a resistor, capacitor or coil. Or it could be between a tube socket and the pins of a tube. To check for a bad connection at a tube socket, gently wiggle each tube when the sound is bad. If the sound comes back when you wiggle a tube, you have found the correct place to work on.

I would like to again suggest that you measure the voltage at the grid of the horizontal output tube. One little measurement will tell you if the horizontal oscillator is working.

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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sun 10, 2015 10:24 pm 
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Thanks Tom. I'll check that tonight. Is this ac or dc voltage I'm checking? Band is it between a particular pin and ground? Or something else? I'm not sure what "at the grid" means.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Sun 10, 2015 11:30 pm 
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Joined: Jul Wed 08, 2009 12:17 am
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Location: Wyoming, Michigan
Image

Image


Sams resistance-check chart and tube locations, if interested. Got the rest of it scanned as well, unsure how to submit it to ETF, maybe someone here can enlighten.


"At the grid" means, literally at the grid. In general, amplifier tubes have a control grid. Triodes have only one. The 6BG6 is a pentode, so technically it has 3 grids, although the grid nearest the cathode is normally called the grid, and subsequent grids are often called screens. Except in CRTs, where they're commonly called Grid 1, Grid 2, etc. Confusing, I know. In any case, the grids are shown as dotted lines in the diagram below. The 6BG6 tube has this pinout configuration.

Image

In your case, "At the grid" is pin 5 of the 6BG6. Pin 5 is connected to the dashed line nearest the cathode. The cathode is the bracket shaped element, the sideways "]", just above the heater or filament which is the caret shaped "^" in the diagram. The topmost bar "-" symbol is the plate. This is where the amplified current flows, more often than not it's where dangerous currents at usually dangerous voltages occur. The grid on most tubes is usually a signal (AC) source biased by a couple of DC volts often for reasons technical. Current flow here is usually very close to zero, so it might be questionable to measure voltages with a meter that depends on a significant current flow. The Sams documents insist that all voltage measurements are taken with a VTVM. Perhaps the 6BG6 application here is at a high enough current to make the point moot, perhaps not. Something to research. Repairmen of the day used the screwdriver and arc trick pretty exclusively, the curly-fry bulb being a modern refinement. Measuring the voltage at the grid will do as well, assuming it doesn't require the VTVM to be accurate.

Measurement taken to ground. Assume DC unless AC is specified.

Well, you can measure higher voltages with your meter if you want. The 1000V plug in most cheapie analog meters is internally just a 2-resistor voltage divider to ground. It would be pretty easy to make a 10:1 divider and bury it in a specialized probe and then just multiply the meter reading by 10 to get the value of the circuit being tested. Would cost all of 50 cents to build. Or you could buy a better meter, or look into a VTVM, or get a 'scope. Or you could buy a 10:1 probe for a 'scope and modify it to fit your meter.

There's always a way.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Tue 12, 2015 3:10 am 
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With my multimeter, I get zero volts DC between pin 5 and the chassis. The needle does not move at any setting, all the way down to the lowest. Well it went up a tiny fraction of a millimeter as I went down, but I may have been imagining even that.

For the tube resistance chart - is that between the pin and the chassis? Where do I stick the leads? Is it with the tube plugged in or unplugged, measuring resistance between just two pins?


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: May Tue 12, 2015 4:42 am 
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Location: Wyoming, Michigan
I won't disagree with Tom that your oscillator is not running then. As long as you are counting pin 5 starting from the first pin clockwise from the key, as seen from the bottom view of the socket. Just to be sure, as pin 4 is supposed to be zero, and if you were counting counterclockwise or from the top view, you might be measuring the wrong pin.

In any case I can't recommend measuring any voltages until you've verified all resistances first. It's how I do things.

The Sams chart values are measured to chassis ground except for asterisked values, which are measured to the point specified in the corresponding asterisked note at the bottom of the chart. Tubes left in place during measurement.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: Jun Sun 28, 2015 10:21 pm 
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I've been very busy lately, out of town and such. Finally was able to connect with my TV restoration buddy Kevin in CT. He tested a number of things and found that the flyback is not working. It doesn't sound like it's an easy part to get. Does anybody know where I can get one? Can a flyback be repaired - anything I can attempt here?
Attachment:
File comment: Low ring count, no horizontal activity, no high voltage, current backing up in the 6BG6.
Flyback is bad.jpg
Flyback is bad.jpg [ 58 KiB | Viewed 3860 times ]


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: Jun Mon 29, 2015 12:14 am 
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ETF lists one available on the website. 32-8331 Flyback. Send them an e-mail to confirm availability and donation amount.

http://www.earlytelevision.org/flybacks.html

_________________
Tim

"One of the advantages of being disorderly is that one is constantly making exciting discoveries." A. A. Milne


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: Jul Sun 05, 2015 8:38 pm 
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sdyer wrote:
I've been very busy lately, out of town and such. Finally was able to connect with my TV restoration buddy Kevin in CT. He tested a number of things and found that the flyback is not working. It doesn't sound like it's an easy part to get. Does anybody know where I can get one? Can a flyback be repaired - anything I can attempt here?
Attachment:
Flyback is bad.jpg

if you cant find the transformer you need try to find a good coil rewinding service. to rewind a coil you need a coil winding tool and the knowledge to run it. a transformer is made up of two coils the primary and the secondary. the secondary has several taps for different voltages.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: Jul Sun 05, 2015 9:52 pm 
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Location: Detroit, MI USA
A lower than expected ring count on a flyback having a laminated iron core rather than the common ferrite core types may not mean it is bad. The only way to verify that is to compare it to another identical flyback and see what the results are. You also have to disconnect it from the circuit, at least remove the yoke connections so it's unloaded.

Based on your earlier voltage readings it seems certain the oscillator wasn't running, and even if the flyback was bad, that wouldn't stop the oscillator.

At this point I'd want to verify horizontal oscillator operation and drive to the output stage with a scope. You can also use a device like the old B&K analyst to get a horizontal drive signal to feed directly to the output stage.

_________________
Dennis

Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: Jul Mon 06, 2015 3:04 am 
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Mr. Detrola wrote:
A lower than expected ring count on a flyback having a laminated iron core rather than the common ferrite core types may not mean it is bad. The only way to verify that is to compare it to another identical flyback and see what the results are. You also have to disconnect it from the circuit, at least remove the yoke connections so it's unloaded.

Based on your earlier voltage readings it seems certain the oscillator wasn't running, and even if the flyback was bad, that wouldn't stop the oscillator.

At this point I'd want to verify horizontal oscillator operation and drive to the output stage with a scope. You can also use a device like the old B&K analyst to get a horizontal drive signal to feed directly to the output stage.

b&k television analyst is an awesome piece of test gear. i had one when i worked with the man who taught me electronics and i just bought one again model 1075. what one do you have mr. detrola.


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 Post subject: Re: Philco 48-1000 Complete - how to restore?
PostPosted: Jul Sun 12, 2015 2:41 pm 
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I have 2 spare chassis that I can remove one if you need it.


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