I'm doing the electrolytics on a Philco 50-T1403 and one section of C3 is a 5uf, 475v. How critical do you think the value is in this circuit? I will be ordering caps and will replace, but wanted to see if I could get away with what I have on hand (10uf) to bring the set up and do some checking.

Full schematci at ETF:
http://www.earlytelevision.org/images/Philco-50-T1403-Sams-115-8.pdf

it looks like its just a decoupling cap and anyway those old caps were good to within -50% to +100% so you should be fine with a 10uf.

I don't think it's all that critical. I would use a 10uf at 450 volt. It's function seems to be to stop power supply noise that could affect sync operation.

Sounds good - it is listed as a 'Synv Inverter Decoupling' cap.

New question. Same set. Had no HV and low B+ (i've only tested tubes including crt and replaced the electrolytics). I pulled out my 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 rang out the focus coil and deflection coils and the deflection looks ok. The focus coil did not 'pass' the Sencore Ringer tests. The focus coil reads 160 ohms across the coil. Is there another way to validate the focus coil?

If you have the sam's for the set I'd compare the ohms reading of the focus coil next to that part on the schematic to see how close they are, and if the difference is over 30% I'd try another focus coil.

If the HV comes back with the yoke and focus connections opened via the removed plug I'd try individually reconnecting the three different windings in turn to see which one kills the HV (might not necessarily be the focus).

If it turns out the horiz winding is killing the HV then I'd try a known good damper from a working set.
I had this problem on a roundy color set not long ago so I figured I'd mention it.

Good luck.

Tom C.

Well the ohms reading for the focus coil is right on the money per Sam's. I will try individually testing each deflection coil next.

Which Sams are you looking at, and what code is the TV?

There's a link at the top of the thread. And I don't see a chassis code stamped anywhere...

Did you replace the capacitors at the horizontal linearity coil (c 99,98)? If so there may be a problem with the linearity coil. I don't think the focus coil would be bad if it measures the correct resistance.

Do you have the -4 volts from the power supply? Do you have 250 volts at pin 10 on the CRT?

A focus coil will not ring. It is intended to have a nearly DC current through it, so there is no need for it to have good high frequency characteristics. If it has the right resistance then it should work.

Looking at the schematic, with the focus coil disconnected some of the B+ voltages will be a little low and the focus pot will run hotter than normal. If the focus coil were so bad as to be shorted, all that would happen is that some of the B+ voltages would be a little high. Now if the focus coil had a short between the winding and the case, that would really mess things up. But then there would be no B+ and the 5U4 would blow out.

Thanks for the input. Checking/replacing mentioned caps and will check voltages next. I believe both the focus coil and defelction coils are okay based on my resistance readings and the feedback on ringing.

I do have -4 volts. And 240 volts at pin 10.

Another question - I'm checking over previous work and making sure I have all my caps in stock before I move forward.

At C97 below, the 820 mica cap is in place, but there is also a .022 cap across it (in parallel) also. This is a code 125 set and per the Sam's schematic it should not be there. It does not look like someone added this. Should I replace as it as found?

Are you certain the .022uf cap added later? It makes no sense to have a 820pf cap across a .022uf cap.

screen decoupler, should not matter, I would leave it be.

It sure looks original. It's a bumblebee just like nearly all the others, and it was buried where it would have been a tough retro-fit. I checked for manufacturers notes in the Rider books and there was no mention of an update. I'll leave it for now.

The general rule of thumb is keep it the way the factory made it. But you do need to replace any bumblebee caps. The higher the voltage across it, the sooner you should replace it.

yep, bumblebees have gotz to go...

Oh yes. All old caps are now gone. And I've put that one back (with a new cap) the way I found it - left the original mica. All my critical voltages now look okay and I have about 8kv at the pic tube anode. Seems a little low, but not sure what it should be. Also hearing a little corona arc I think. The flyback did ring okay, and the HV cap (500mmf) and the two resistors in the HV chain were also good. Back to testing tomorrow!