Ts18 verticle problem

[timmy]

Still didn't figure this out, but there is 2 10meg resistors at the 6sl7 that I checked and also tried others and didn't work was the same no different but the one 10meg that is across pin 4 and 6 if I put a 1 meg across the 10meg I get a picture and vert hold the linearity is off on top and the hold is Alittle touchy. pin 6 is wired for ground and the one end of the .004 is also tacked to ground. It seems as if the tube is not conducting by why with a 1 meg it calls for 10 meg. If I try a 1 meg across the other 10meg it works very little bad picture and no response from vert hold or size. All this changes with the one resistor at 4 and 6 . I can't measure the voltage on the plates of the 6sl7 with a Dvom I won't get an accurate reading but measuring I do get a reading of 120 Vdc and 75 Vdc the SAMs shows a lot more so my meter won't tell but changing that resistor to a 1 meg I'm thinking lowering that resistor seems to allow the tube to conduct with possibly low voltage on the plates but the screen is super bright. The plates get voltage from the hv with the resistors which check ok. This is nuts already, I'm open to anything at this point

[jr_tech]

Have you tried a different 6SL7? Possibly this one has grid emission.

Could there be a carbon path in the tube socket between pins 5 and 4 that is pulling the grid more positive than it should be?

You really need to get better voltage measurements... can you get another HV probe or fix the one you have?

jr

[timmy]

Originally Posted by jr_tech

Have you tried a different 6SL7? Possibly this one has grid emission.

Could there be a carbon path in the tube socket between pins 5 and 4 that is pulling the grid more positive than it should be?

You really need to get better voltage measurements... can you get another HV probe or fix the one you have?

jr

I tried several 6sl7 no change as for my hv probe tossed it last year could not fix it. Carbon path , well anything is possible but I need to find out how to know if there is a carbon path taking place befor I get into changing that socket. Do you have an idea how to determine if there is a carbon path. I don't here anything arcing nor do I smell any corona from hv. Pin 5 SAMs shows 320 Vdc and I find odd that the 6.8 meg at pin 5 gets warm but the other 6.8 don't.

[jr_tech]

I would unsolder all of the connections to either pin 4 or pin 5 and mesure resistance between the two pins... leakage as high as 10 meg or so could mess up the bias on the tube.
You really need to get another HV probe, as low HV could be te main source of the problem.

jr

[timmy]

Originally Posted by jr_tech

I would unsolder all of the connections to either pin 4 or pin 5 and mesure resistance between the two pins... leakage as high as 10 meg or so could mess up the bias on the tube.
You really need to get another HV probe, as low HV could be te main source of the problem.

jr

I thought maybe low hv but the crt is super bright and I tried adjusting the ring on the 1b3 and of course no change. Should the tube remain in the socket when I remove from one pin and test?

[jr_tech]

The tube shouldn't make any difference, unless it is the cause of leakage... try it both ways. You could also check the tube itself for any leakage between pins, but since you have tried several different tubes without changing the symptoms, it is unlikely that you will find any leakage unless they all have the same fault.

jr

[EdKozk2]

Timmy,
Did you ever try spraying any cleaner into the vertical hold and size control to see if it would stabilize the vertical roll? Did you try wiggling V9, V11, or V12 while the set is on to see if it helped? I come across worn and dirty contacts all the time in old equipment. The cause of all sorts of issues. Just because parts are swapped or tested doesn't always eliminate the root cause.
Do you understand how the vertical feedback loop works with this set? If you have a scope, check to see if you are getting the proper trigger signal to your vertical oscillator grid from the sync separator/ integrator network.
Ed