Finally joined the club! (CTC-9 content)

[leadlike]

Would you mind explaining how to hook all of this up to monitor cathode current? I've just about got my '9 dialed in, but I'm afraid to run it for long periods as I have little understanding of how to do this. The Sams says to remove a jumper, but I have yet to see where this jumper is at that I can hook my ammeter to...

[miniman82]

Originally Posted by zenithfan1

Too bad mine needs recapping at the moment or you could borrow that too.

I tell ya, I'm gonna buy stock in all the major capacitor companies! At the very least, I'll cause my own stock to go up with all the parts I'm buying. hehe

Those color bars look great on that 21CYP22! That generator is fun to play with huh?

I know, right? I'll take a shot later on when it's darker outside, so you can really get a feel for the satuartion. On a side note, I may have found an issue with my Portacolor while playing with the gen... More on that later.

The thing is great for doing purity, just press the red button

Yep, and purity on the 9 is spot on for all guns.

[miniman82]

Originally Posted by leadlike

Would you mind explaining how to hook all of this up to monitor cathode current?

Sure, but let me explain my way of doing it as well.


Sams has you use different moving needle meters to make the measurements: a 0-1ma meter for the 6BK4 cathode, and a 0-500ma one for the 6DQ5. Normally you would either unsolder a ground connection (in the case of the 6DQ5), or clip a little wire jumper (on the 6BK4) and place the meter inline to take current readings. Instead, I chose to permanently install 1-ohm 5-watt resistors from the cathodes to ground. This allows me to set the DMM to read voltage instead, so I can move 1 meter around vice watching 2. It gives the same exact readout as it would if you were reading current, I just think it's easier to move leads around to different resistors.

Plus it's somewhat less dangerous-not so many wires to run into while making adjustments. And even if I did bump a lead loose, there's little risk of hurting anything since the circuit would still be complete. If you measure current with an inline meter on the 6BK4, I shudder to think what would happen since the high voltage would be instantly unregulated if a current meter lead came loose.

The Sams says to remove a jumper, but I have yet to see where this jumper is at that I can hook my ammeter to...

For the 6DQ5, you have to remove the ground wire on pin 3/6 for a current reading/install resistor for voltage reading. On the 6BK4, you have to follow a wire from pin 1 back to a terminal strip. On the strip, you'll find a little loop of wire. Clip that loop, and insert the current meter or install the resistor.

[miniman82]

Today old tv nut and myself went through the entire Sams horizontal adjustment proceedure, to try and get the current lower. First we connected a scope to the horizontal sinewave coil, and adjusted it for 'equal peaks'. Then we used 2 current meters, one on the horizontal output one on the HV regulator, and a high voltage probe on the anode supply. We tweaked the efficiency coil for lowest reading on the output, then adjusted high voltage for <.8ma on the HV regulator while reading 23.5kv on the HV probe.

Result: 6DQ5 cathode finally settled at around 176ma.

Next, I'm gonna try rolling a few different output tubes to see if I can get it even lower. Chas mentions there were some issues with some iterations of it, so I went right to Ebay and ordered a few. My hope is that the new HOT will get me the rest of the way there.

Also, Moyers does not have a replacement flyback for the '9 at any of their stores...

BTW, I found out what happens if the HV regulator becomes defunct: a whole lotta nothin'. HV jumps up to like 27k, but nothing that would stand out at get your attention. It happened when the current meter came off the 6BK4, just like I said it would. lol

[miniman82]

Forgot to update this thread!

I was finally able to mod the CTC-9 to include a drive control, which basically involves installing a pot, cap and resistor. I just copied the schematic of the CTC-7 chassis, and it worked a treat. Cathode current is now spot on where it should be, and the picture quality did not suffer. Width is still good, too. last thing I'm gonna do is see about getting a few louvers punched into the HV cage, then I'll install a fan and call it done. That should make a very stable platform for long-term watching.

[wa2ise]

Originally Posted by miniman82

BTW, I found out what happens if the HV regulator becomes defunct: a whole lotta nothin'. HV jumps up to like 27k, but nothing that would stand out at get your attention. It happened when the current meter came off the 6BK4, just like I said it would. lol

Usually, variations in the very high voltage on a CRT makes the size of the raster change. Higher voltage makes a smaller picture, as the higher voltage is pulling on the electrons harder. Changes in the picture content in a set with DC restore will change the current draw on the flyback, brighter makes the voltage sag and the picture will get a little bigger. B&W sets usually did not have DC restore, when the TV show showed a night scene, the blacks would get gray. And the grays would get blacker if it was a sunny day in the TV show, so the current draw was fairly constant and thus the picture size stayed pretty much the same. But no DC restore looks crappy on a color set, so they put it in, and then the need to regulate the HV shows up.