Nice to see you making progress, even though there's been a couple of bumps along the way. When you get the bugs worked out, shoot me a PM and I'll get those knobs and the nameplate/control cover out to you.

Hi Bob,

I have a question about the small test CRT tubes you use. After you get a set to work with a test tube, do you need to readjust the set again when the full sized tube is installed?

Also, I am thinking these tubes do not use an ion trap, true?

Is the focus coil a problem?

Steve

You can download a copy of the Sams here: http://www.earlytelevision.org/pdf/C...Sams_160-2.pdf

The drive control is a pot. I'll try replacing the cap and measure all the voltages and waveforms in the horizontal circuits..


Thanks, I sure will!

Yes, you need to readjust, the height, width, linearity etc. They do not use an ion trap and are self focusing.

Leaving the focus coil in place does produce a blurry image. That's why when I unmounted it in the photos above the picture improved.

Thanks!, Bob

Acording to the diagram, that .25 amp fuse protects the screen grid on the 6BG6. it also supplies voltage to the horizontal drive control as well as the damper circuit. the first thing i would do is place a milliameter between the cathode of the 6BG6 & the -100 volt source that is currently connected to the cathode of the H.O.tube. power the set up & monitor the meter reading. if it is rising & starting to go over 250Ma, it is possible that the 6BG6, itself, has developed grid leakage that does not appear when it is cold. you can also sub another 6BG6 to see if it does the same thing.

about anything could be causing the fuse to blow, however the most obvious things would be the H.O.tube, the horizontal drive pot that has "whiskers" in it, the Screen resistor (r88 22k) that has lowererd it's resistance.
i would check these things first.

A bit off topic but perhaps one of these is your set.
In any case there's a fair chance it passed through that guys hands at some point.

Capehart assembly line circa 1951.

http://videokarma.org/attachment.php...1&d=1410414807

I could use his help right about now :yes:

Replacing the drive control has stopped the fuse from popping. It appears to be tin plated but I couldn't really see any whiskers.
https://farm4.staticflickr.com/3914/...7effac66_z.jpg

All the resistors and capacitors on the HOT have been replaced and DC voltages seem reasonable. The cathode waveform matches whats shown in the service info.
https://farm4.staticflickr.com/3881/...0fccd539_z.jpg

I've also tried swapping out each of the the three tubes inside the HV cage, but the low HV issue remains. Only about 6.5 kV under load. Just for the heck of it I installed a full size CRT, and you can see how dim and unfocused it is.
https://farm6.staticflickr.com/5561/...cc23d55f_z.jpg

So it seems to me that leaves the two high voltage ceramic caps inside the cage, the yoke and the flyback as culprits :scratch2:

Capehart 325
 

While looking on ebay, I noticed a similar one located one state up from me. Viewing the listing showed it had been robbed of some parts: tubes and looks like 12" speaker. What actually concerned me was the power transformer laying in the bottom of the cabinet with frayed wires while a power transformer was still mounted in the chassis. All that, the $100 opening bid, and the condition of the cabinet was enough to turn me off of it.


http://www.ebay.com/itm/Original-195...item3395211702

At least I got a photo of the missing HV cover now :)

how about the voltage on the cathode of the damper tube? it should be around 550 V. if not, the low end of the winding on the flyback most likely has shorted turns.


i would say that the flyback has a few shorted turns. have you done a "ring" test on the flyback transformer yet?. that can be more revealing than a ohmeter can be.

I have 355 VDC. Capehart service info just says HV for that voltage. Sams says 250 VDC.

Yes and it passes.

Sams Says 550 v on the cathode of the 6W4 & 280 v on the plate of the 6W4. When measuring the cathode, is that where you got the 355 volt reading? the voltage on the plate of the 6W4 is supposed to be 280 v & is 20 volts low.
if the cathode of the 6W4 is reading 355, it is too low & is a possible indication that something in that immediate circuit is drawing too much current. after all, that is the B-Boost circuit. that also could be the cause of the low B+ voltage (250v)

Yes, I got 355V on the cathode. I was referring to Sams 112-3 which more closely matches my chassis and states 250 VDC for the 6W4 cathode. For example I have a 6AL5 video detector rather than a 1N34 diode as shown in Sams 160-2.

Try pulling the HV caps. I have known them to short. In my RCA 8TC271, one got so hot that it cracked.

There's one 500pF 20kV doorknob cap under the 1B3 rectifier socket. Very difficult to get at. I'm going to try a different yoke first.

I dug up another RCA yoke plus a Y-10 and Y-11 to try. All are 70 degree yokes.

https://farm6.staticflickr.com/5595/...77873ba6_z.jpg

The owner also sent me a photo of the tube chart showing it used a Farnsworth 160-AR CRT.

https://farm4.staticflickr.com/3843/...18a75f01_o.jpg

Got a little more HV (~9kV) with the second RCA yoke also marked Y-17.

Could there be a shortage of HV filtering when using that test CRT?

Well there's a 500pF HV filter cap and when I tried a 16KP4 with aquadag coating, it didn't help. My Farnsworth 160-AR picture tube has no coating at all. Not sure if it originally did or not.

What's this? :scratch2:
An active restoration project thread that has gone nearly a month without a post? Heresy!

I'm scratching my head along with you on the HV issue but I can at least provide one facepalm-worthy suggestion to another annoyance you're having... Put the test CRT in "upside down" so the anode connection is on the other side and the HV lead runs across the top. The test CRT is small enough to probably allow the HV lead to still reach, and then the weird spring on the HV lead won't put up so much of a fight. There appears to be enough slack on the socket wiring to rotate 180 degrees without issue.


Continuing this thought-process, consider the possibility that the damned spring is sapping the HV through cracks in the very much vintage rubber HV lead insulation? That would explain the low HV measurement even with the tube disconnected. I'd bypass the whole HV lead assembly with a modern replacement and see if anything improves. There's no hidden resistor in series up under the suction-cup either, right? You've checked the filament current limiting resistors up under the HV rectifier, too? Swap the rectifier out for a string of microwave oven rectifier diodes? Aside from the flyback and doorknob cap, the HV lead is one of a rapidly dwindling list of things you haven't yet substituted for known or presumed working parts...


:para:

Going further down the grasping-at-straws path, pop an analog milliamp-meter in series with the HV supply directly after the rectifier and see if there's more current than expected being drawn. Obviously only a floating analog meter will work here. I'm sure someone makes a digital meter capable of measuring 0-100mA up around the 15kV zone, but it probably comes with a hefty price tag, and it sure isn't something you're going to use very often anyway.




:tears:

Even further down the "Nothing makes any sense, why doesn't it just work!" path:

Is your chicken blood fresh, or are you using that freeze-dried just add water stuff they sell to the wannabe-wiccans? Perhaps the bleached skulls need more dribbly candle wax on them, or maybe they need less. Swirl your tea-leaves in the opposite direction next time... Try everything! (In moderation.) :thmbsp:

Haven't had much time to work on it. The anode lead is about 6 inches to short to make it to the other side of the CRT.

As near as I can tell, there's no resistor in series with the anode lead or in parallel with the 1B3 rectifier tube filament.

When I find time, I'll try to run a new anode lead. The only way to get at that area is to take the HV box off which is not so easy since the flyback is mounted to it.

https://farm4.staticflickr.com/3952/...76974679_c.jpg

Here it is stripped down.
https://farm4.staticflickr.com/3952/...c5b9986a_c.jpg

I get about 0.1 ohms from the anode cap the the rectifier base, but I'll try replacing the lead anyway.

Flyback close up. The shiny goo around the HV lead is some RTV133 I applied to reduce the odds of it snapping off.
https://farm4.staticflickr.com/3940/...4872bc6d_c.jpg

HV rectifier area looks clean. I'll try using a solid state rectifier as suggested.
https://farm6.staticflickr.com/5615/...f11ba314_c.jpg

I recently won a little assortment of vintage TV parts on ebay and it including this air core flyback. The part # is different but it sure looks like the one in the Capehart and it ohms out very close as well. Might as well give it a try.

https://farm8.staticflickr.com/7549/...fd9f62fe_z.jpg

[QUOTE=bandersen;3119451]I recently won a little assortment of vintage TV parts on ebay and it including this air core flyback. The part # is different but it sure looks like the one in the Capehart and it ohms out very close as well. Might as well give it a try.

Bob, you certainly have nothing to loose and a lot to gain! Good on 'ya, Mate!

I think I'd have me a peek under that electrical tape before applying power.

Nothing wrong with using a temporary alligator clip jumper lead to lengthen that second anode wire. I've never had the HV arc through the insulation to the dag, chassis, or wherever else it may be contacting or draped, even with cheapies.

I'd be more scared to risk removing it absent any other justifiable reasons for investigating underneath. Obviously I'd spend a good few minutes going over the whole thing with all the bright bench lights on and with my mag-visor for signs of trouble.

I don't like those wafer-type sockets, especially on high voltage. They can have secret interwafer problems. It would be a valuable adventure to change them to good new molded ones, even ceramic ones if you're paranoid like me.

I finally got back to working on this chassis :)

The ceramic HV cap on the damper tube has been replaced and a new HV anode lead installed.

https://farm8.staticflickr.com/7353/...b728d400_z.jpg

https://farm8.staticflickr.com/7424/...dc8584b8_z.jpg

I also installed a genuine Farnsworth 160AR CRT I stumbled across on craigslist.

It had no trace of any external coating but I did fine a ground spring on the chassis so it probably should have one. I went with a temporary one made from aluminum foil and tape :)
If I get it working, I'll coat it with some Slip Plate.
https://farm8.staticflickr.com/7446/...8c499118_c.jpg

https://farm9.staticflickr.com/8563/...967bb96c_z.jpg

https://farm8.staticflickr.com/7383/...3b0393a0_z.jpg

The old hardened tape was replaced wit some cloth tape.
https://farm8.staticflickr.com/7454/...f88ef048_z.jpg

While I had the brackets off, I finally found the chassis revision number - C-281.
https://farm9.staticflickr.com/8657/...590f7a1b_z.jpg

TIme to fire it up again.
https://farm8.staticflickr.com/7401/...2baa6c19_c.jpg

HV is around 10kV. I'd rather see 11 or 12, but should be plenty to produce an image.

Sure enough after a lot of fiddling with the trap magnet, I got a raster.

I get occasional arcing. I think it's my temporary aluminum dag isn't making good ground contact.
https://farm8.staticflickr.com/7329/...08fda29e_z.jpg https://farm8.staticflickr.com/7452/...570ee622_z.jpg

I'm gonna let it run a while and see if any problems crop up. If not, I'll give that CRT a proper coating :yes:
https://farm8.staticflickr.com/7407/...3f2d80c5_c.jpg

Sooooooo, are we listing the HV lead as the culprit? :scratch2: Glad to see that you climbed right back up on this horse and got rewarded with some success. :thmbsp:

Did you connect that HV lead before the power up, or was there a brief lightning show before you noticed? :D

No, unfortunately replacing the HV lead had no effect. The HV is still about 20% low and for a while it dropped down to only 5 kV. Still not sure what the problem is. Also, I just discovered the sporadic arcing is actually inside the electron gun. Maybe there's a loose bit of metal ?

Yes, I did remember to connect it up :D

My Sencore CR70 has the meter right at the edge of bad in the HK short position. It typically arcs once or twice on power up the settles down.

I went through the centering and linearity adjustments and it's looking pretty good.
I'll install an isolation type CRT booster if I can find one :yes:
https://farm8.staticflickr.com/7408/...b98fa0ef_z.jpg

Meanwhile, I decided to go ahead and coat it with Slip Plate. I'm quite happy with the results :)
https://farm8.staticflickr.com/7449/...d9b050ec_z.jpg https://farm8.staticflickr.com/7350/...a548ac7e_z.jpg

Installed the recoated CRT and did all the ion trap, focus coil linearity etc adjustments again. It's playing well but still get the occasional arc in the CRT on power up. Will try an isolation type booster when it arrives in a couple days.

Meanwhile, the picture isn't quite as sharp as I think it could be so I'll try a video IF alignment. It used a staggered tuner IF and it's a an easy procedure. Feed an RF signal into the mixer tube shield an peak each coil to the specified frequency frequency.
https://farm8.staticflickr.com/7362/...a5f6d25d_z.jpg https://farm9.staticflickr.com/8573/...f2889ff5_z.jpg

https://farm9.staticflickr.com/8612/...33a55b1b_c.jpg

I gave up on the alignment once I realized all the slugs were glue in place with something like loctite! Meanwhile I got a nice shading and balance knob for a forum member :) That just leaves the "Capehart" control name plate.

https://farm9.staticflickr.com/8632/...2ee6d176_z.jpg

I also received a link to the video about gold or silver plating plastic parts. Basically you apply a special conductive paint then use conventional electroplating solutions. http://youtu.be/czTjYlsct_k

Cool technique but all the supplies are a little expensive for just plating a few knobs.


Meanwhile, the owner of this set scored a Capehart 323 off ebay for $50 :) This one is a bit earlier with a metal cone 16GP4 picture tube.
I expect I'll be restoring it for him someday too.
https://farm8.staticflickr.com/7343/...080438b5_z.jpg https://farm9.staticflickr.com/8651/...0a5871ea_z.jpg https://farm8.staticflickr.com/7389/...c0c6a5b7_z.jpg

The missing nameplate was hiding in the bottom of the cabinet along with the owners manual :D Looks like silverfish got to it and it's falling apart but I hope it can still be scanned.
Perhaps a mold can be made from this nameplate and dups made ?
https://farm8.staticflickr.com/7405/...77bd42d1_z.jpg https://farm8.staticflickr.com/7288/...6e77ea87_z.jpg

Hey guys. I recently hear from the owner that he had the cabinet full refinished, installed new grille cloth, painted the knonbs and even scored a control cover door on ebay :)

Here are some photos. Hard to believe it's the same set.

https://farm5.staticflickr.com/4602/...2bd8d913_c.jpg

https://farm5.staticflickr.com/4765/...88d73acf_c.jpg

https://farm5.staticflickr.com/4705/...7a0439dc_c.jpg

https://farm5.staticflickr.com/4764/...e1e72bbf_c.jpg

It looks like the hold controls are under that screw mounted plate. Sets of that vintage often need touching up of the sync controls. I am surprised they would design it like that unless they used very stable sync circuits. What a beautiful set. I sure miss the days of stylish TVs.