Valentine's gift (or is it a shameless trick?)

[old_coot88]

Originally Posted by Phil Nelson

This looks like a pretty complete replacement. It's physically smaller and it has different insulation. No wax -- yay!

Hmm. Differnt supplier, evidently. Ours was the wax version and came sans the frame.
The ones for Predictas were the only replacement flybacks I ever saw supplied that way.
oc

[leadlike]

I've heard the same thing from other sources about Predicta flybacks (you only got the windings for a replacement). I think Phil's set takes exception to what we have come to expect with the Predicta name (crappy construction) as it was a top of the line set for them at the time.

[Phil Nelson]

Originally Posted by Phil Nelson

With a .1 uf cap in place, I measured 118ma cathode current with the Triplett meter. That's the middle of the 100ma-140ma range given in the schematic. I'm going to quit stressing over this, since the voltages on the HOT and general performance are also normal.

Speaking of current measurement, this week I got my hands on an HP 428B DC milliammeter, which gave the same reading as my old Triplett meter, so I guess the Triplett's good enough for government work.

Andy's method worked like a charm. Clip the 428B probe over the HOT lead and measure away. Easy as pie. On this set, the Width control affects the current directly, so I turned it down to around 100ma, which gives reasonable width & picture.

I got the 428B to use on my color roundies, but it has already earned back the few shekels I paid for it, and now I feel better about just letting this Philco play away. After warming up a couple of minutes, it looks fine without the CRT brightener, so I tossed that in a box. Who knows why they put on a brightener in the first place? Maybe that was a quicker solution than diagnosing some peskier issue.

Phil Nelson

[Kevin Kuehn]

Originally Posted by Phil Nelson

Andy's method worked like a charm. Clip the 428B probe over the HOT lead and measure away. Easy as pie. On this set, the Width control affects the current directly, so I turned it down to around 100ma, which gives reasonable width & picture.

I missed something. What exactly was Andy's method?

Kevin

[Phil Nelson]

Sorry, the method is just what I said (only too briefly). The 428B is a DC milliammeter whose clip-on probe you can place around the HOT lead to measure the current. Andy C. has mentioned doing this before. I thought I had referenced that somewhere earlier in this thread, but maybe I just imagined that part.

Anyhow, it seems to work, and it's easier than lifting one end of the cathode lead to measure. Perfect for a lazy guy like me.

The manual is at hparchive.com. Talk about your cosmic gizmo. Be the first kid on your block with a second harmonic flux-gate-type magnetometer probe!

Phil Nelson

[old_coot88]

Originally Posted by Phil Nelson

...Be the first kid on your block with a second harmonic flux-gate-type magnetometer probe!

That sounds like sumpthin' out of 'Back to the Future'.



oc

[Kevin Kuehn]

Ah... so it's a clamp on amp probe. For a minute there I thought you were just clipping the lead of a convention VOM over the HOT lead and measuring current. I thought maybe somehow with the HV it was jumping through the insulation.