Need some help on an 8TS30.... - Page 8 - Videokarma.org TV - Video

old_coot88 · #**106** 12-20-2015, 05:54 PM

Shucks, for some reason I thought the chassis was already out of the cabinet. If you haven't pulled it yet, and while those tubes are still removed, try to get an analog current reading on R127B.

Kevin Kuehn · #**107** 12-20-2015, 06:00 PM

Another thought - Those resistors may actually run hotter if you're leaving the back cover off the chimney. Something about convection not being able to pull cool air up through the bottom opening, and the heat just sort of hangs around.

***Kamakiri*** · #**108** 12-20-2015, 06:17 PM

Chassis is out of the cabinet at the moment. Putting it back in is a 10 minute job....no big deal there. If the HV lead doesn't need to be connected I do have an adapter lead to hook up the socket so I can set the tube next to the chassis. I don't have a test tube here. And the cover is definitely off the chimney

Just tell me what's next. This set has a ride back home next weekend if we can get it figured out. If not no big deal.....it would just have to wait till the next time.

Kevin Kuehn · #**109** 12-20-2015, 06:35 PM

I've kinda lost track of what kuszactly the current state of affairs is?
Maybe there should be a live web camera aimed at the Kamakiri workbench.

old_coot88 · #**110** 12-20-2015, 07:53 PM

With the chassis out, you don't need the CRT hooked up for troubleshooting this particular problem. It's not going to make HV anyway with those tubes removed.
If you've got an analog milliameter with a 0-500 ma (or 0-250 ma) range, just stick it in series with R127B, variac the chassis up to normal line voltage, and see what the current thru R127B is.

***Kamakiri*** · #**111** 12-21-2015, 06:44 AM

Quote:

Originally Posted by Kevin Kuehn

I've kinda lost track of what kuszactly the current state of affairs is?
Maybe there should be a live web camera aimed at the Kamakiri workbench.

Well, if a visual aid helps....

FYI, here's the meter I've been using.

I don't have an analog milliameter. I have two analog meters, a basic Micronta voltmeter, and a prehistoric Weston model 697 that works, but doesn't have the range.

Decided to power it up to get a reading on my digital meter. Started it off on the variac at 75v, and all of a sudden heard and saw a SNAP. Looked like the spark came from the area of the chassis ground lead below the chimney, but inside the chassis. The *only* thing in that area, but further down below, is the horizontal centering control.

Y'know, I'm about ready to give up on this stupid thing......

***Kamakiri*** · #**112** 12-21-2015, 06:48 AM

Now let's back it up a sec. When I had missed the ground lead on R128A, everything was acceptable except the heat going to R127B. I'll say this out of frustration, but can't I just leave that ground lead off, and stick like a 50 watt wirewound in R127B?

Yeah, didn't think so.....

***Kamakiri*** · #**113** 12-21-2015, 07:12 AM

Wait, wait, wait wait. Careful study of the chassis just revealed something to me.

It seems that someone back in the day replaced C3 before I recapped the set, but didn't anchor it properly to the chassis. With the jostling of moving the chassis around, C3 must have knocked loose and the floating ground was very lightly touching chassis ground.

Odd thing is that I don't recall it being loose during the restoration, but there it is loose, with only one rivet hole drilled all the way through and one missing rivet.

Gonna fix that and try it again.

***Kamakiri*** · #**114** 12-21-2015, 09:34 AM

Got that all fixed, and powered it up. Now I've got no HV. Dammit.

Kevin Kuehn · #**115** 12-21-2015, 10:24 AM

Quote:

Originally Posted by Kamakiri

Got that all fixed, and powered it up. Now I've got no HV. Dammit.

So now with that cap not shorting to ground, are things running any cooler? Did you re check the DC voltage across R127B?

***Kamakiri*** · #**116** 12-21-2015, 10:45 AM

Friggity frack, this thing is haunted.

I did NOTHING to it since the last power up, and now I have a picture.

Here's what is on the screen, bear in mind I've made no adjustments because I didn't want to run it out too long. Contrast control does nothing, brightness past halfway causes the picture to bloom and lose focus.

Resistors R127A and B are pretty damn toasty, but measuring 40.3 V across R127B.

Kevin Kuehn · #**117** 12-21-2015, 11:17 AM

Well 40.3 volts DC across R127B is really close to where it's suppose to be, provided your voltage reading is accurate. I'd replace R127B with like a 20-25 watt unit, install the chimney back cover and let it run a while.

old_coot88 · #**118** 12-21-2015, 11:36 AM

Well sunnava gun. Now, with that Micronta meter, you can get a reliable current reading using the analog voltage across R127B, per I=E/R (current=voltsXohms). Then for wattage, P=EI (watts=voltsXamps).
Be interesting to see if the voltage reading on the Micronta matches the digital's.

***Kamakiri*** · #**119** 12-21-2015, 01:22 PM

This has GOT to be the world's crappiest analog meter. The DC V scale only goes up to 15, and then a VERY coarse 0-1000 V. Ugh. Model 22-027U. I'll be honest in saying that I hate analog meters....had a couple Simpson 360s along the way that I really wanted to love.....but just couldn't. Guess it's all in what you're used to.

Time to take a Holiday break and order up some big honkin resistors for this sucker. I don't expect they'd be in any time before next week, so unless anyone has any other thoughts (which are always appeciated), we'll pick this one up after Christmas.

Meanwhile, I just might toss this Zenith roundie chassis on the bench and get going on it

ChrisW6ATV · #**120** 12-21-2015, 06:39 PM

You will get this set working, I am sure. Enjoy your holidays, and get back to this set when you have both time and desire. Lots of us here are ready and willing to offer help.