Is this the 17MT80 chassis? If so, all the pots on mine were dirty and needed a good scrubbing. Seems it was a pretty cheap chassis, the controls are not up to RCA standards.

yep that's it. Very cheap pots used on the back. every single pot in the front is also very dirty. The IF section is all SS, my other one has a good pic, but a bad tube socket (I think) in the blue output tube (likes to flicker more or less blue) socket. I checked the PCB very closely, triple checked all the ground stakes, prodded the parts around it. if you move the tube it would flicker blue. a real PITA. I don't like the use of large PCBs for tube sets, just seems to be asking for trouble.

If trying a new tube ,cleaning the tube pins and socket, and reflowing the traces going to that tube don't help then you should swap the socket out for a new one.

yea I know I should replace the tube socket, just got tired of fooling with it.

Heres a trick, if you can find a garden snail, squeeze the juice out of the snail on the socket. It will cause the socket to swell and the pins will tighten up.

You really need to get laid.

cleaned the pots on the front, that cleared up all the sync issues. Tuner needs cleaning. the brightness pot needs to be turned up pretty high. I will be checking the 12GN7 video out soon, if its weak it can cause a CRT bias issue cutting off the crt. I tested the CRT and it tested very good so the high screen settings tell me something is a not right.

this set controls the brightness by biasing that 12GN7 thru the cathode with a 500 ohm ww pot and a 82 ohm resistor. On my other set that 82ohm had drifted up, which would increase the bias, causing the higher plate voltage and again upsetting the CRT bias. The Vert seems to shrink as it warms up, the vert out bypass cap sits right next to a big power resistor so it gets pretty hot from that. I will replace that one just because I dont like the high heat its getting. its in a single can, the PCB has holes for axial and a can in for that cap.

I think I can get to that 82 ohm resistor without pulling the chassis, its mounted right at the pot.

One last issue is the focus, varies from about 3.3 to 3.7 kv.

I plan to check the 66meg resistor, and maybe try a new focus rectifier.

I made up a 120pf cap to replace the 130pf 6kv that couples the output from the focus coil to the cathode of the focus rectifier. I have had issues with focus coils before when not using the EXACT replacement. Hope that is not the case here.

I would still like to try a HV silicon rectifier some day instead of one of the Se sticks.

Mine had a tube rectifier in it, I prefer OEM style.

yea but those stick types are hard to find unless you know of a source. I am down to 1 NOS GE CR-1 and a couple salvaged ones. I came up with a unscientific approach to test them. Used a VTVM on a low volt scale and a few 9v batteries in series for 45v and the stick in a circuit to see how much voltage I get thru the stick then reverse the stick and try again. I used the NOS GE and when compared to a known weak rectifier the diff was large. Crude but it is a quick way to compare. Not sure how much difference is ok, so its still a process being worked out.

Use that leakage test on the cap tester. They get sensitive to the temp and work better as they warm up. SI would be the way to go. Take apart a trippler and harvest the diodes

Yeah, rapidly fading from scene is the old craft of circuit diagnosis/troubleshooting by old techies who did this fulltime for a living back in the day, and the many little hints, tips and quirks that were gleaned only from experience.

it was the focus coil. I subbed in another (this time with some jumper leads so as to save the time if it was no better) and voila I get very sharp focus with plenty of range on either side. that was easy...

I will install the new coil and button it up later.

operating on a hunch that the phasing of the 1st replacement focus coil was not adding but only subtracting to the focus voltage, I reversed the leads in the yoke circuit and now get a much sharper pic, but I still like the second focus coil as it seems the adj range is broader, and easier to nail the right setting.

ok back to the 1st replacement. the 2nd one broke right at the mount enough fo a chunk off the form to make it unreliable. so the 1st replacement was used. Don't know why but the range is fine with it now. focus is right in the middle and easy to adjust. Of course I managed to break the center coil wire, argh... but was able to graft on a hair thin piece and reconnect to the term lug. thats what I get for working on it out in a dimmly lite garage.

Anyway its looking VERY good. it has all the orig parts and a couple new tubes.

the vert is a bit bouncy, so I will end up pulling the chassis and going thru those cap in the feed back circuit/the cathode bypass cap and coupling caps at the video and the color amp tubes. I see some brown drop low volt caps around there.

I am kind of tempted to just set it up on the bench and monitor it to see if that vert settles down.

then I need to decide if I should just stash it away for spares or do something with the cabinet. the ply base is starting to delaminate. It looks like it screws on to the wood frame rails. It would not be hard to make a new base. the sides are cheap fake looking wood that is all bunged up.

I have been wanting to try to build a new cabinet, this looks like a good candidate. I am thinking of using the frame to hand on some nice lauan ply.

I have some nice wood legs that have a danish modern look. the performance of these philco hybrids is very good. I have a nice metal cabinet model, but a pretty wood one would be nice too.

Very helpful post. It's given me a few things to test. I am working on a Philco 50-T1404 and had no HV (i've only tested tubes including crt and replaced the electrolytics). I pulled out my Sel-Sun test pic tube/yoke (removed the existing yoke plug which also disconnects the focus coil) and voila - had HV and a raster on the test tube. I'll ring out the focus coil and deflection coils directly tonight and see what I come up with. I'll also check my HOT cathode current.