Hotpoint 17S301 Update, formerly Jail Bars issue.

[Eric H]

Fiddling with this Hotpoint that i recapped 15 or so years ago but never finished.

There are vertical bars across the entire face of the screen and it's just a bit darker on the left edge. Caps have all been changed and all the resistors on the sweep board checked, I also checked most of the resistors on the video board but only found two slightly out of spec, I replaced those.

Checked all the tubes, subbed the damper and output to no effect.

If anyone has any ideas I'd really appreciate hearing them.

Schematic: http://vintagetvsets.com/schem/Sams%...t%2017S301.pdf

[old_coot88]

Did it have the jail bars issue after you recapped it 15 years ago? If not, I would first try jumpering the Boost filter cap (C7). It mighta just dried up while sitting.

[Eric H]

Originally Posted by old_coot88

Did it have the jail bars issue after you recapped it 15 years ago? If not, I would first try jumpering the Boost filter cap (C7). It mighta just dried up while sitting.

Hard to say for sure, I don;t recall them but I didn't run it much.
I have this one picture from back then, can't see any bars but it's a pretty low res image.

I'll sub the cap and see what happens.

[tom.j.fla]

Hi Eric, 1 or 2 things jump out at me, 1st put the scope on the B+ lines anything but a flat line go after the filters, MM line sets have a stacked B+ circuit so swap the 12CA5 to check for H-K leakage. 2ed put your scope on the agc line anything but flat line is bad news. Your pic looks like you have vertical foldover with retrace lines at bottom of screen. Also looks like there is bowed raster lines at top of screen. Well hope this helps,Tom

[Eric H]

Okay, just to verify, the Boost cap is C7 right? I jumped it and no difference.

Tom, I have a Scope but have never used it, I could probably figure out how to use it enough to check for ripple on the B+.

The bowed raster lines may be because that is an 8" test CRT so the geometry probably isn't going to be good.

I just checked the 12CA5 and it checks fine with no shorts, if I can find another one I'll sub it and see if it makes a difference, the sound on this set is excellent with no hum.

[tom.j.fla]

Eric that's correct C-7 is the boost cap. As for the scope use ac coupling to view for stray signals on the B+ lines. Use a low sweep speed and set the input for 1V p-p,then set sweep speed higher to check for horizonal signals on B+lines. Noise on the low B+ line could mess with tuner, video IF's and video amp and not cause any hum in the audio. Agc line must be completely flat. Some how either vertical or horizonal sweep is getting in where it does not belong. Did not see that it is a test CRT. As far as using a scope there are many books on line for sale and some e books for free. One other thing use a isolation transformer, we would not want the scope or the device under test to go BOOM!! All the best,Tom

[Eric H]

Thanks Tom, I'll see what I can do with the Scope tomorrow.
It does seem to be a video problem rather than a sweep problem, the picture doesn't seem wrinkled when the scene pans side to side, it just has dark and light bands.

[Eric H]

Okay, an update, and a solution.

I found that if I pulled tubes in the video circuit, the bars would still stay on the screen for as long as it took the sweep tubes to cool off, even pulling the video output tube, which pretty much eliminated everything in the video circuits so it had to be something else.

I checked the voltage at the base of the CRT, pin 11 is the 490 volt boost, run through a 1.2 meg resistor and it was supposed to be 480 volts, it was about 300 volts, (why would it be 480 volts after going through a 1.2 meg resistor? Misprint?) anyhow, I checked the resistor, it was fine, 1.1m, so I jumped it, this made the CRT brighter and also eliminated most of the bars.

I decided to put the correct 17ATP4 tube back in and that was all it took to fix it, apparently the test CRT isn't quite compatible in some way.

The voltage on pin 11 is still 300 volts but that's probably about right.

There is something slight towards the left side when there's no signal, also some Barkhausen on the right but this is not visible when there's a signal.

I also know there's some high voltage sizzle going on inside the flyback cage, I took it apart last night and cleaned it all up and replace the socket for the 1X2 but I still hear some sizzle somewhere. The set has very healthy HV, 13kv with the CRT lit up and it'll arc right through the cap of the 1X2 if I touch a screwdriver to it. possibly the Fly itself is sizzling or the socket's still giving some trouble, I suspect the latter because moving the HV lead around makes it change a bit.

Well at least one thing is solved, and this set has an incredibly good picture, probably one of the best of all my 50's era sets, the sound is great too, I always thought these GE/Hotpoints were on the cheap side but the performance is outstanding.

The camera really exaggerates the moire effect.

[Eric H]

I've got this set almost back together, this was just suppose to be a quick finish up to a job I started 15 years ago but it turned into a major project.

Besides removing, cleaning and replacing the flyback I had to swap out the broken CRT socket, the antenna/ac interlock assembly and the volume control/switch with parts from a spare chassis. I also redid some wiring in the power supply area with better wire, I redid it years ago but used Belden automotive wiring that wasn't rated for the voltage involved.

It looks pretty nice, I still have to put the Hotpoint emblem on the front and install the back. It's picked up a scratch or two since I painted it all those years ago but they are minor.

The second picture is what it looked like when I got it, it had been painted white with a brush and some house paint, they were really sloppy and got it on the knobs and the screen too, the cord was also painted white so I soaked it in some TSP and scrubbed it clean with a wire brush.

This set has a UHF tuner, the dial for it is underneath the clear fine tuning knob, the fine tuning knob is also the UHF tuning knob, you just turn it beyond where the VHF fine tuning range and it adjusts the UHF through a Rube Goldberg string setup, it really seems like an afterthought on the part of the designers.

[Radiotronman]

Great restoration, that set looks like new now!

[tom.j.fla]

Hi Eric, found 3 books on scope use that you or anyone else might find usefull or are wanting to learn how to use a scope and best of all there free. Titles are 1)Know your Oscilloscope By Paul C. Smith 2)Troubleshooting with the Oscilloscope by Robert G. Middleton and 3) Oscilloscope Techniques by Alfred Haas. These books were found at SMC Electronics ,web address www.smcelectronics.com, from home page go to merchandise page select parts & accessories then select downloads scan down to service info where you will find the titles I spoke of, and a whole bunch of good stuff. All the best Tom

[Eric H]

Originally Posted by tom.j.fla

Hi Eric, found 3 books on scope use that you or anyone else might find usefull... Tom

Thank you Tom, I got them.

[jr_tech]

" I always thought these GE/Hotpoints were on the cheap side but the performance is outstanding."

Perhaps some of the quality that they left out of the 9" set found its way into this 14" model.

jr