CTC-5 & Admiral, Shared Problem - Videokarma.org TV - Video

bgadow · #1 10-13-2008, 01:36 PM

Right now I am trying to get my Admiral T1000 (24E2 chassis from '63) up and running. It has hv issues that are challenging my abilities.

Right now I have meters hooked up to check current for both the HO tube and the regulator. The former should be 210ma, the latter should be set at 850 as I recall. So, I power it up and HOT current is a little high (225) and won't go lower; I can adjust the regulator all over the place with the hv adjustment. The focus is usually way out, and can't be adjusted any better. There are sometimes signs of LV being too low. (critical vertical, poor audio)

I have replaced many caps and resistors and all tubes in the circuit; the flyback is new.

Okay, here is the big clue: If I tweak the horiz hold over to the stop, then back again, the set will snap to attention. The picture improves, I get focus, it more or less behaves. (but then gets worse again.) It seems like that last 1/4 turn on the horiz hold does it.

Next thing: My CTC-5 does much the same thing, but not so severely. Upon power up I get a picture that is all out of sorts, but a quick turn of the horiz hold will put everything right. The RCA has always done that since I got it running. It has other issues that need attention. (I suspect its HOT current is set wrong) That is for another day.

I'm not sure if this horiz hold thing is a red herring, but I thought I would throw it out in case it gave anyone ideas. I'm going to keep tinkering with the Admiral. I think I'll check that hh control next and make sure it doesn't have a bad trace...it seems to me that on the ctc-5 there is a coil?

Another clue? Sometimes from adjustments, and sometimes for no apparent reason, the current levels of both tubes will go out of sight. (the HOT will peg the needle, and my dmm measuring across the regulator resistor will read 1.5v+) On one occasion last night I had a very dim blur of a raster, HO current in the 150ma range, and zero regulator current. ???
Who knows, if I keep this hobby up I just might learn something!

bgadow · #2 10-14-2008, 09:45 AM

Update: with careful adjustment I was able to get a decent raster, decent focus, good regulator current...everything was happy except the HO current which is still too high. I swapped meters but they are both the same-over 225ma. I measure the grid voltages and both are right on the money. I just can't figure out why it is drawing the extra current. I still have to fiddle with the horiz hold on power-up to get things right. I've been searching through my "vast" library of TV repair books but nothing has really helped.

mr_fixer · #3 10-14-2008, 12:14 PM

how many volts are your ac power line? 117, 120, 127? I'd put it on a variac and set to the set's rated voltage and remeasure it. Just a guess, Logan

bgadow · #4 10-14-2008, 01:23 PM

You know, one of the books I have makes a big deal of it, but I kind of blew it off. In the past I have measured it at 121 or so. Time to drag out the variac!

John Folsom · #5 10-14-2008, 04:38 PM

Have you checked the screen grid voltage on the HOT? How about the B+ for the horizontal circuit? And I assume you have tried more than one HOT?

Some of your descriptions also make me wonder if you have an AGC issue.....

bgadow · #6 10-15-2008, 01:08 PM

The screen grid voltage was right on the money, which seemed strange. I have 2 good 6DQ5's and they both respond the same. I have not looked at the B+, though. In general AGC action seems okay but I am not ruling it out.

I did measure my line voltage and it has crept higher than I thought, up to 124. I used my isotap and found about 110v worked well-cathode current is right on the mark or a little lower. Trouble is I am back to a no-focus situation. The problem isn't always there but I haven't found a pattern yet-I thought it was temp related since when I do get focus it gradually goes away, but then cooling the set down for several hours has no effect. I'll do some more voltage checks soon. I haven't read the hv lately, and have been just setting it so I have good regulator current. At this stage that means cranked all the way up. I don't have the feeling that it is that low (from looking at the raster it is giving me, which is actually not too bad aside from the focus) but I know there is a relationship there.

bgadow · #7 10-16-2008, 12:38 PM

That B+ line should be 365; with line voltage at 120 it is right on the money, but when I drop to 110 it falls to 350.

It was suggested to me to check the horiz hold control and so that is where I'll go next.