10KV caps.
 

I'm triaging a 1951 Andrea to see if it's restorable (going to get it running first), and it has a three 10KV caps in it. Two are 470pf (this TV has dual 1B3s) and a 500pf which I assume is the doorknob. I haven't really gotten into it yet, just perusing the schematic.

Digikey has several choices for HV caps, what are some safe ones to use if I need to order some?

John

Doorknob caps have been made until recently and some are still available through mouser and digikey. I typically buy those and machine pegs to adapt their threading to the mounting style of the original doorknobs. They are expensive, but original and on the early color sets that comprise my main use case it is worth the investment.

If the CRT has good dag on it and there is a cap in parallel with the cap formed by the CRT dag then you can probably eliminate that cap.

May also be able to get away with leaded ceramic caps to save money, but I haven't tested any in that application yet to give any endorsements.

On some sets the caps are used to support the HV rectifier, so leaded replacements won't work.

If you replace the cap a with leaded cap and a plastic, ceramic or phenolic stand-off to mechanically support the socket in the same manner as the old door knob it would work. It would not look original, but would work.

Doorknob caps often do work, but a decent percentage of failures have been seen....If they are not known bad you could fix the rest of the set and see if they are ok.

The doorknob on this one is mounted on the flyback board and is not used as a standoff - just appears to be wired in electrically.

John

I decided to move along a bit on the Andrea, and brought her up on a variac. A can filter refused to reform and decided to puke itself, so I pulled the 40/500 - 40/500 and restuffed it.

I found the B+ normal and nothing running hot. The HV was around 1500v, so I checked the two 1B3 rectifiers, damper, and horiz output tubes. Interesting, this TV uses two HV rectifiers as a doubler - something I'd never seen before. I image the plan is to improve the reliability of the flyback.

The tubes checked good so I pulled the two 470pf 10KV caps I suspected might be an issue at 70 years old:

https://i.imgur.com/gM6Is8X.jpg

I found one reading very little capacitance and some leakage at 600V (the most my Z meter will provide) and the second one decided to become a 15 ohm resistor.

Probably explains my low HV...

I'll take the doorknob out next and check that. I'll order some ceramic caps and see if she'll run.

John

I've ordered some 470 10KV caps to replace the leaky/shorted ones, but was wondering what a nominal HV reading should be with a 16GP4 tube. Should I expect around 15K give or take?

John

Per the GE Tube Manual, typical anode voltage is 12KV. Design max is 14KV.

Excellent. Thanks for the info Tom. The Sams makes no mention of nominal anode voltage, and I've never worked on a TV this old.

John

Minor update. I ordered some 470pf 10KV ceramics and installed them on the flyback in the voltage doubler circuit (two 1B3s in this TV), and I get 12KV now, which according to Tom, is right in the ballpark.

I have an image of sorts, but it's extremely overdriven. In fact, with the brighness control anywhere except all the way down, it blooms to the point of HV loss. It also has short vertical deflection.

There are some .05s which are clearly leaky in the chassis as they are throwing the DC voltages of is several circuits, but what's odd is the extreme ringing visible:

https://i.imgur.com/nTea5BE.jpg

Hoping the ceramics in place of the 10KV film caps aren't causing issues.


John


EDIT: the raster is actually full horizontally. If I adjust the contrast, the screen will wash out and fill the screen, although it remains darker on the right side. The ion trap affects it but won't change what I see when the brightness and contrast show a clean snow pattern. Also, I don't want to shotgun this particular unit as I am am working through it as if it was a fairly new TV to bone up on my vacuum tube skills. I started in this trade at the end of the tube era but still worked on many through the late seventies.

Surprisingly, the CRT is strong. I found this TV with a brightener hanging off the back of the tube, and coupling with the fact that this metal coned beastie isn't known for a long life anyway, expected to find the tube junk. On my tester, it actually showed decent emission after about 10 minutes. When firing up from a cold start, I get a very bright partial raster in about 30 seconds, so I think I'm good on the tube anyway.


.

If there is a B+ boost line that is powered by the flyback I'd make changing any paper cap connected to it my first priority for replacement....It could be causing all problems you're seeing.

Is that the Andrea model tv16 or something like that ?

It's a cvl16, or at least the table model version.

John

I didn't change any papers around the damper yet, but I brought home my backup scope from work, and there's a nasty pulse modulating the video at the horiz rate, so there's an open bypass in there.

I'll get back to it Saturday unless my brake job on my truck runs into Murphy's Law..

John

Murphy always comes visiting during brake jobs. It's one of his favorite things to screw up.

Yep. My nephew brought his truck by last Sunday, and two lug nuts were over torqued. My impact couldn't touch them and my old standby of using my cross bar and four pound dead blow hammer couldn't crack them. I told him to bring it to the tire shop who put the tires on and have them crack them loose.

My two dirty tricks for stuck nuts&bolts (not just lugs but anything somewhat beefy) are breaker bar with 6' extension pipe*, and if that fails I configure my breaker bar such that it has to move up to come loose then I stick a bottle jack under it and slowly jack up on the breaker bar...1/4 of the cars weight either breaks the bolt free or off (99% of the time it comes loose) or worse case scenario it starts to lift the car or the persuasion rig slips apart.

When I did my inner tierods I had to come up with something new....they have to come loose with an open ended wrench (the ends of my wrenches are not shaped right for the jack to grip at the angles available) my arms couldn't break the original 18 year old ones free...so laying on my back I managed to hold it on with my arm till I could get my foot on the wrench....then I used the greater muscle strength of my legs to get them loose.

*That pipe usually lives in my suburban due to its lugs seeming to tighten themselves if left alone a few months.

Torn muscles suck! Work smart not hard my friends.

Cool the table version , never saw another table model besides mine .
You will like the picture on this when you get it running , perhaps the best 16" I've ever seen

I took a quick look yesterday morning before work and found the noise sitting on the filter in the negative supply, so I brought it to work and restuffed that one.

I installed the can this morning and the raster is now clean - and the bright and contrast controls work properly. I haven't seen a picture yet but the snow pattern is crisp

Two more issues: horizontal running off freq and short vertical.

Im trying to pace myself but it's hard to stay away!

John

Progression from first plug in after 4 decades or so:

Had no HV. The main can filter decided to puke it's guts, so I restuffed it. Replace 10KV caps to get a "raster" of sorts:

https://i.imgur.com/RinNVpH.jpg

Found another can getting warm, so restuffed that. Found leaky paper cap in video amp overdriving CRT (no control over brightness). Changed three paper caps and 6S4 vertical output tube gave me more deflection, but not enough. Replaced bypass electro filters to get this:

https://i.imgur.com/yLXFxh6.jpg

Connecting RF input and adjusting continuous Mallory inductuner to get to this point where the horiz is out of range:

https://i.imgur.com/Ihoijkm.jpg

Found the horiz hold control was wide open in the middle of the range. Surprisingly, the osc still ran. Running some cleaner through it cleared the open spot in the control. A couple of paper caps in the horiz osc gets me here:

https://i.imgur.com/YjijTRg.jpg

Those lines are artifacts are from resizing the image.


Vertical still short, so that's next. Once I get it right, I'll go ahead and do a full recap of all parts that haven't been changed. I've restuffed three cans so far, and will do the rest before putting the chassis back in the cabinet.

Thrilled that the metal cone 16BP4 tube (that had a brightener on it when I found it) is strong. Very slight IF ring/smear as it's tuned, but I haven't touched any IF tubes. Despite that, has a very good picture.

John

Normaly I just do all the caps , check resistors and tubes and then fire it up and see if there's more issues or just adjustments need to be made.
Your case is a slow replace this or that and fire it up , interesting way to do it but from what I see in the pics a full recapp and it probably will be good to go.

When I restore anything more complicated than an AM radio, I first get it running to verify if the "hard" parts are good or not. If it had a dead CRT (which was actually expected since it had a brightener installed at some time in the 1960s), or a bad flyback, or a bad yoke, or a bad power transformer, I'd abandon the project and move on to something else, particularly with a rare bird like this Andrea. If it was a common TV like a 630, I might be inclined to shotgun it and deal with a bad transformer or yoke if I came across it.

Ordinarily, I would indeed just recap the Andrea at this point now that the hard parts are verified to be working, but I wanted to use some tube troubleshooting skills that I last used (at least with television) in the 1970s or early 80s at the latest. If I was restoring this for a customer (I've done a few), I would have shotgunned it. But there is a big thrill in getting it going bit by bit. It was fun seeing the tube light in the first pic, then another thrill at each step, and I was smiling ear to ear when I got the first picture on it.

So instead of shotgunning the old girl, I'm working through it. Once it's running 100%, I'll go ahead and restuff the remaining cans (I think there's four more cans) and replace the balance of paper caps.

BTW, I like restuffing the cans because I hate adding terminal strips and external caps underneath the deck. If someone in another 70 years works on this TV again, the bottom layout will still look like the pictures in the Photofact. So it's not for originality, it's for keeping things neat and recognizable for the next guy. Hopefully, this TV will be running long after I'm gone (to the Carolinas hopefully :) ).

Working on the various circuits instead of shotgunning is like building a model: I can't tell you how much I'm enjoying each step, and will be a bit sad when it's finally over.

John

Update on Miss Andrea
 

Vertical sorted out. Video improved. I'm at the point where I know this TV will be a good performer, so I'm going to go ahead and replace the remaining paper caps and restuff the rest of the cans.

This is from a standard DVD of the Twilight Zone (Mr. Dingle the Strong) fed through a cheap modulator:

https://i.imgur.com/Om5bkpW.jpg


I think the IFs are a bit out of alignment and my best equipment only does 45mhz. I have an old Precision 415 but I've never used it. Have to give this some more thought.

John

I think that picture looks wonderful on that old crt. I'm inclined to believe the video IF is about perfect, can't tell on the sound from here. I applaud you for taking the time to keep your trouble shooting skills sharp. I too feel that's a big portion of the enjoyment of getting these going. Routine replacing of caps is rather boring after you've done few million. ;)

I forgot about the sound! I dismounted the speaker/transformer from the cabinet and plugged it in. There's only a bit of sound in a *very* small area of the fine tuning. Strangely, the FM works pretty good considering the only antenna is the one inch of twin lead on the balun transformer that's feeding the DVD player into the tuner input. It picks up half a dozen stations with no real antenna, although it's a bit distorted but listenable.

I haven't touched the sound section, but I suspect it will come around when I shotgun the rest of the caps and filters.

Man, I've had a blast so far. I've not spent any more than a half hour on any one session to make the fun last, and quite honestly I'm sure I'll be disappointed when it's all done and stuffed together. I've got a late 50s RCA metal portable that I'll have to do next.

It's not a sickness, is it??

John

You may need to walk the IF.... Basically tune the IF for max volume, shift fine tuning closer to best picture tune the IF for volume again till best sound and pix are in the same place.

The distortion could be ratio detector adjustment.

Definitely recap (and maybe check resistances) before playing with audio alignment.

Early post WWII TV stations used stronger sound carriers so TV and sets were not designed to have the same sound IF gain as 50s sets....It may end up like my Stromberg Carlson Dumont RA-103 clone where TV sound is adaquate with volume at max and FM radio is far beyond adaquate at a lower setting.

You got the affliction bad.... Just be glad it's TVs and not that other affliction going around.

If I'm not mistaken the sound is picked off just after the 1st video IF. If so there shouldn't be too much interaction with the video.

A bad audio IF tube and weak output improved things, and I walked the audio IF as you suggested. Sound is very good but not all that loud - sounds like the way you described your SC..

Here's what's weird: when I put the TV/FM switch in the FM position, the screen of course goes dark but the TV sound gets considerably louder. I would be thrilled if the audio level was that loud when it's in the TV position. Note to those who are not familiar with this TV: the TV/FM function switch is NOT a bandswitch. This uses an infinitely variable Mallory "inductuner" (not a 12 position incremental type), so it tunes the FM continuously between VHF low and VHF high.

The TV/FM switch does several things: it lowers the B+, it disables the sweep by ungrounding the 6CD6 cathode, and turns off the filaments to the video section and CRT. It looks like it's supposed to also ground the -11V source at the bottom of the main bypass caps but that doesn't seem to happen, but then there are also a couple of changes made in my version than the SAMS I have for it.

All I did so far was disconnect the part of the switch that lowers B+ and the sound didn't improve, although the picture certainly deteriorated with the low B+.

I don't see how it could be the shutdown of the filaments because the increase of sound is immediate when put in the FM mode, and decreases immediately when it's put back in TV mode.

I'll play some more with it tomorrow.

Kramden66 was certainly right: this TV has a very good picture, better than I hoped actually.

https://i.imgur.com/hDwmMKm.jpg?1


The video IF definitely is a little off. When tuning from one extreme to the other, the picture is sharp on either side of center, but differently sharp (hard to describe it). One side has a bit of ring on vertical edges, the other a bit of noise. The center is free of artifacts but it has much less detail.

I mean, it's very good, but not optimal. When I'm finished done recapping and verifying the resistors, I'll do an alignment.

John

I have had 5 decades aligning these early sets with split sound like yours. The distortion cannot be just the ratio detector because the sound IF in a split sound set changes with the fine tuning. Remember it isn't an intercarrier sound set where the sound carrier beats with the video carrier to maintain sound over the video tuning range. In a split sound set you adjust for best sound and the picture should and must be set at that point optimally. The sound tunes like an FM radio and when tuned you accept the video as is. This is why you need the proper equipment to do the alignment.

You need a sweep generator and accurate marker oscillator to align the video and audio IF. There is lots of literature on this. Follow the manufacturers notes.

I have aligned split sound Westinghouse, Dumont and RCA sets. (I currently have 4 pre-1950 RCA split sound sets). They all work superbly with full 4MHz video bandwidth and excellent sound. The alignment process is less forgiving but the picture quality is second to none when done right. And I prefer them as you do not get that intercarrier buzz!

Remember that the video is transmitted vestigial sideband and so the video carrier must be at 50% down on the nyquist slope. The picture when tuned correctly will be sharpest not brightest.

Seems to me you are almost there and hope to see you cross the finish line.

In split sound sets there is interaction when fine tuning because the same front end local oscillator is responsible for the creation of the video if and sound if.

And I've got none. Attention being paid!


The distortion is gone. Bad cap in the ratio detector and a couple of cranky tubes. Also eardrummed the audio IF. The sound is nice and clear, no buzz, just a tad low in overall volume. Still, it's usable as is.

I have several pieces of equipment and, unfortunately, none work at 24mhz that this old girl uses. I've been thinking of modifying my B&K415 (that I bought new). I aligned a few 44mzh TVs back in the 70s with that genny, and it's easy to use and works well.

I also took my VA48, set it to burst sweep, and fed its video output into a B&K1077B analyst (also bought new) and was able to have it convert the VA48 multiburst signal to 24mhz - the 1077 has an infinitely variable IF output.

I don't have the courage to try this hack setup on the Andrea, although I was considering just connecting it to the IF and scoping the video at the detector and see what the multiburst looks like. I may have something else of no value that I can use that frankensetup to experiment with.

I do have a Precision E-200 for which I only have a couple of crystals, but I don't know how accurate a wobbulator setup is.

Thanks. I planned to finish by the fall, and I'm way ahead of the schedule, so I backed off a bit for other projects.

What I really need to find is some sort of matching mahogany base to put it on.

Thanks for the info.

John

There's a thread on here where someone found a way to heterodyne the IF of a B&K 415 down to the old 20MHz IF range using a precision oscillator and mixer...it was all external gear that can be easily added and removed from the B&K depending on what IF freq you are aligning in a given day.

The problem heterodyning a 41 MHZ sweep generator down to 21
is that to keep the markers correct you need to have the fixed oscillator
at about 20 MHz, which is too close to 21 even with a balanced modulator.

On the other hand you can heterodyne it UP easily to VHS and run it into the tuner ...
if that is aligned broad enough. You can of course check to see that by trying different channels.

O you can just use the markers at their upside down places and get the shape right,
knowing where they actually are.

I forget how exactly they did it but mixing 2 some waves creates new sine waves at both the sum and difference frequencies so they may have used the difference and a higher frequency oscillator or double conversation. ISTR the markers were in the right places...

I may be using my B&K to align a 44MHz set tonight and if that goes well I may dig up that thread and use that to down convert my generator.