So the 2.7 k will work but may not last.

It's not going to immediately explode, throwing fire and sparks all over, it will work, but it will always be a weak point, prone to fail at some point.

I don’t understand what’s going on with this set anymore I put the other 2 resistors in v2 the image is even better but the b+ voltages are dipping again and maybe at this point if the voltages were up where they should be I might have video now. One moment there good the next they drop. I’ll have to change the 2.7k resistors maybe v1 v2 are drawing to much because they are not conducting at full. Who knows.

You guys need to read the datasheet a little more closely and take a step back.
The limiting factor on the resistor is power dissipation. Nothing to do with voltage rating.
https://www.mouser.com/datasheet/2/3...20-2758246.pdf

If you had 750 volts across a 2.7K resistor, it would be pumping out over 200W!

Old TV Nut had it right, you hit the 3W mark at 90 volts so there better be much less than that across the resistor.

It's not more concerned 750 "across" the resistor itself, but more the being at that potential as a whole, and the possibility of there to be a breech of the outer layer if the voltage rating is to high.

The resistors he ordered are fine.

Breach of the outer layer to what? The 750 for the Vishay is across the resistor and subject to the same power limits.

Generally speaking for all resistors. 1W can handle 350 volts, 2W, 500 volts, 3W, 750 volts across the resistor. Constrained by power disippation and ambient temperature etc.

As for diodes I can’t see putting higher amp diodes in only to feed a draw and that’s not fixing a problem the output diode is way to hot it is definitely not normal I can’t even touch it it’s that hot and I tried the cheapy diodes and the output still gets hot. It appears that when working all the controls are working color controls vertical I have to find out why they are hot as it may answer why the video is not there yet.

not really.

you have shown that you have good video with direct input, more than once I believe.

did you do a current test on this set now that you have a meter to do so?
was it more than 580-590ma?
if the original diodes are worn, it could explain them getting hot, and as mentioned before, the cheap ones are suspect as being counterfeit diodes, so they won't be much better, so putting in new 1a or 2a diodes should put the heating problem to rest.

Since you get good video from direct input, it is safe to say its not related to the power supply.

I did do the ma test and it was 550ma so that would suggest there’s no short I have these big diodes but don’t know the rating. And again after the set is on 10 or so minutes the voltage comes up within 5-7 volts normal voltage so now all the resistors are in v1 v2 and this video is so close. I noticed that the video would flicker on the screen as perfectly clear video so something is upsetting the video path.

"So if this is only drawing 550ma then the diodes should not be getting hot not warm but hot. Another mystery."

This is within the norm range.

These diode are 57 years old after all, and after getting hammered each and every time the set is turned on and the caps charge up, it would not be any surprise that a pair on new ones would help quite a bit, and the price dif between 1a & 2a is almost nothing.

Yes that’s true I will have to end up changing them if I could only get video it is so close I could taste it there is a coil right at the antenna input maybe someone turned it so I’m going to turn in and out carefully watching exactly how many turns if no better I’ll put it back exactly where it was because it almost seems like a very weak input signal. Nothing to lose at this point.

Are c1, c2 and c3 staying cool? :scratch2:

jr

Yes but one is in the area of the 550ohm resistor it gets hot in that corner.

one you may want to try is listed on page 6 on the sams, step 5, coil A13, it is a visual only adjustment.

the 20w 550 gets hot enough to cook a steak in a decent amount of time! :D:yes:

That’s the last coil in the IF I already tried that one turns in and out little if any difference put it back exactly where it was that’s the coil with the diode video detect.

I’m almost burned out with this set although i don’t give up easily but trying that coil no difference from befor just alittle but I put it back. I’m wondering about the .001 caps in L4 and L5 to be honest I already did the leakage test with the .1 cap to ground and the cap dropped to 0 so I guess this means they’re good.

One thing to try is an AGC override, as shown on page 6 on sams, this is easy and needs few items and clip leads. Shown below. If it helps get a tuned picture , it means AGC is the problem.

500k potentiometer, linear.
9 v battery.

Wire the battery to the outer lugs of the potentiometer.
Hook negative line to chassis, and wiper of potentiometer to test point A on chassis.
Start sweep from 0v and work up from there to see if it gets a reaction.

You know I had a small feeling that the agc may be the problem because the agc pot does absolutely nothing if the agc is maxed couldn’t it distort the video like this. What could cause the agc not work or have it maxed. Wouldn’t the agc affect the video input B.

Input at point B bypasses the tuner and IF sections, and thus leaves ACG redundant.

Thus the point if you can't get it to work, you can always build a simple video amp to get the contrast levels right and go that route.

https://www.electronicsforu.com/elec...ideo-amplifier

That’s another thing with the little video I have the contrast bearly makes a difference is this because of possible agc problems. And of course don’t have a 500k pot I think I have a 700 don’t know if this would work.

if its 700k then it should be OK,, anything above 100k should work, i picked 500k, cause they were most common.

700 OHMs, may load the battery down a bit however, not sure.

There’s not much to this agc the 50k pot and a 33k and 47k the pot checked good so this pot adjusts the bias on pin 6 of the 6hs8 correct?? I redone the k1 and it’s in this time I got a 680k rather then 680 ohm.

https://www.amazon.com/RadioShack-10...s%2C242&sr=8-6


It's audio taper, but should still work for the AGC bypass test.

Pics from today does this look like the agc maxed.

It's most likely 1 of 3 things.

A) the IF is so out of alignment that you cant tune in anything.

B) AGC is messed up and you can't tune in anything.

C) combo of both.

applying bias to the AGC test point will rule out one of these.

What if there is a higher voltage at the test point holding the tube at full agc then the test won’t work using a 9 volt battery how would this setup lower higher voltage if that works that way. Or does it maybe need a certain amount of voltage like the battery to turn it off per say. I do know that test point has 7.5volts there.

If you look at the “alignment instructions” in the sams, it says to connect a variable bias supply to point A, this will override any voltage present and allow you to set your own due the the high resistance of the the source.
Using a potentiometer and a 9v as described, should allow you to set the test point from 0 to 9v, which should be enough to see if AGC is the fault.

Ok well I’ll put that together and try and from what I have read agc is really not needed anymore since we are not using antenna anymore but rather stable inputs like cable.

This would be correct if the circuit were working as intended, but it may also so out of wack that it won't let you tune in anything.

The intent of doing this bias sweep on point A is to see if it has any effect at all on the screen, better / worse.
If there is a noted change, then it prob is AGC related, if not, then it's IF and alignment.

I’m going to go over a few resistors in the agc circuit then on to the 9v get up.

Just for the heck of it chassis back on back but upon plugging it in have a test lead on v1 with antenna and just as the hv came up it jumped 4kv and when it did the voltages on v1 and 2 neared 100 v then hv dropped again did this twice this just about confirms something is getting in or shorting intermittently somewhere. I never seen this since working on this chassis.

Well it’s official the 9v setup proves an agc problem voltage jumps up 11 volts on v1 and that’s a huge difference using the only pot which was 900k

The voltages when it first comes on really don't mean that much, it's once it is all warmed up and stable that matters.

There is a reason for doing the AGC bias test, this goes back to 2016 when I was working on my CTC-16XL and it too had IF problems, and old_tv_nut said the following..
---
The AGC circuit is a feedback circuit. This means that the 9 volts at the plate does not necessarily mean anything is wrong with the AGC circuit itself. It may be getting an incorrect detected video signal at the grid due to some other reason (like a dead IF) and trying to correct it by changing the AGC voltage. You need to check the detected video for starters. If it's missing, check and/or replace the AGC tube. And, you may be right that some component is bad. Check all the voltages in this area. Check resistor values wherever voltages are way off. Further trouble shooting could involve breaking the feedback loop by connecting an adjustable bias to the AGC line, as you would for aligning the IF. If video is missing or wrong amplitude and you can't get it by manually setting AGC bias, there is something dead in the IF or tuner.
---
so please try that bias override, and see the results.

So I assume the voltages at the agc tube 6sh8
3 7.95v 9 32.53 6 116 7 83. Doing the 9v setup then check voltages?

This should be done with the crt hooked up and a signal being fed in the tuner, adjusting the AGC bias to see if it makes any marked improvement in the picture on screen.

Ok let’s say it makes a huge difference nice picture what would be the next step because I’m lost at this point I have checked all the resistors in and around the tubes associated with the agc so if this proves to give a great clear picture what’s next.

If it does turn out to be an AGC related issue, the whole AGC / NOISE GATE system will have to be taken into account, as Old TV Nut pointed out, this is a feedback system, involving not just the 6HS8 immediate area, the whole point of this is to find if there is or is not a problem in this circuit.

if there is not, then on to the IF.

Well unfortunately the bias test did nothing I even jumped the pot and gave it 9 v no change. This is beginning to really hurt. So I guess the agc is trying to fix or adjust the input.

Since you have given test point A a bias sweep of 0-9v with no results, and been over the resistors in the IF section more than once from what I can see, this basically only leaves one thing left, the IF is badly out of alignment, this is likely causing AGC to overcompensate, as there is no video for it to reference to, causing the abnormal voltages.

Who knows, the de-tuned state may also disrupt the normal voltages, be that as it may, color sets are quite hard to align even for the most experienced techs with the right equipment on hand.

It took me 3 tries to align my BW Arvin set (45mhz), and that was just with a frequency generator and a volt meter.
But for color, you need a sweep marker generator and a oscilloscope plus lots of know-how.

But the one thing that must never be done is, try to visually align a color set's IF, this will always end badly and make is worse than when sttarted.