Still Having RCA 8TS30 Issues

[Chris K]

Originally Posted by old_coot88

I feel your frustration bro. I might've missed it, but have you checked voltages on:

V118 (6SK7) 1st sync amp ----- pertinent voltages are pins 4, 6, 8 (that's G1,G2, plate)

V119 (6SH7) sync separator --- pertinent voltages are pins 4, 6, 8 (that's G1,G2, plate)

V120 (6SN7a) 2nd sync amp -- pertinent voltages are pins 1 & 2 (that's G1 and plate)

Are those tubes lighting up good? If any are metal, they should be getting warm after a few minutes running.

I really don't see a smoking gun here except for the lower voltages associated with the reduced 135V line being bled off to another voltage line source.

6SK7 #4 -3.6V #6 96V #8 187V
6SH7 #4 -4.3V #6 104V #8 103V
6SN7a #1 -1.3V #2 68V

[old_coot88]

A suggestion - from a dead-cold start, with your voltmeter on the 135V source (jct. of R185/R186), turn the set on. Since the 5U4s give full B+ almost instantly, is the 135V still low? Or is there a signifigant drop as the rest of the tubes begin conducting? This would tell you if it's tubes lugging the 135V down, or something else circuit-wise.

[Chris K]

Originally Posted by old_coot88

A suggestion - from a dead-cold start, with your voltmeter on the 135V source (jct. of R185/R186), turn the set on. Since the 5U4s give full B+ almost instantly, is the 135V still low? Or is there a signifigant drop as the rest of the tubes begin conducting? This would tell you if it's tubes lugging the 135V down, or something else circuit-wise.

Great suggestion. The diagnostic skills available here are an invaluable instruction. I don't know why trying that didn't occur to me...it should be a pretty revealing exercise but I guess that's part of the learning curve! I will take a look at that this evening and thank you so much for hanging in there with me.

[Yamamaya42]

Again, I'm not saying this is the same problem that your set has, but it's the one that MINE had, I too had a weird problem with the 135v rail being very low, it did not cause me any sync problems, but did cause tuning and contrast problems, the fault was eventually tracked to the WHITE HI-Q 1500pf caps on the IF power rail, the ones with the red ends, NOT the brown tube like ones, on mine, many of those red ends seemed to have degraded and gotten gummy, some of the caps looked like they leaked something even, after replacing only those white HI-Q 1500pf caps, my 135v rail then came up to nominal range, and things worked much better, not perfectly as my tuner is a bit weak, but much better then when I started.

Again, not saying that this is the problem you are having, but worth looking at.

[Chris K]

The old style ceramic caps?

[Yamamaya42]

Originally Posted by Chris K

The old style ceramic caps?

yes, I posted pics of the ones that gave me problems on your other thread.

http://videokarma.org/showthread.php?t=276630&page=2

[bandersen]

I'm wrapping one up right now and all five of the 270pF mica IF coupling caps were bad. Symptom was poor gain. That might account for your tuner being weak.

Never had trouble with the white Hi-Q caps but of course anything is possible.

[Yamamaya42]

Originally Posted by bandersen

I'm wrapping one up right now and all five of the 270pF mica IF coupling caps were bad. Symptom was poor gain. That might account for your tuner being weak.

Never had trouble with the white Hi-Q caps but of course anything is possible.

I just know that a third to a half of the ones in mine had rather soft like red ends, and a weird brown sap like stuff that seemed to be coming from them, I really did not get where it came from or how it got there, other that it must have come from the cap somehow.
I can post a pic of some before they were removed later.

And yes, the 270pF micas in mine are still OEM, and most likely need to be changed, but the tuner was in poor shape as well, but did work to some degree, looking inside, I could see insulation starting to come off of the wiring inside, I did try to clean contacts, but not too much, for fear of making it worse, the pair of 150 ohm resistors in the rf amp were quite out of tol when I tried to test them, how far , I don't recall.
This set, does not get snow with no input, but does get a picture (with some slight fuzz) with a normal rf modulator, and crystal clear when I BLAST it with a Blonder Tongue micm-d.
It can do with an alignment, as it's hard to get the sound and video to tune in at the same time, though I don't have sweep marker generator, I have the digital RF generator, which I used on the Arvin TV, which ironically is the only one of my older BW sets that gets snow with no input, meaning that they all could use a touch up.

[Yamamaya42]

http://suzaku.live-evil.org/0415202203(1).jpg

pic of the weird brown stuff on the white caps

[Chris K]

Originally Posted by old_coot88

A suggestion - from a dead-cold start, with your voltmeter on the 135V source (jct. of R185/R186), turn the set on. Since the 5U4s give full B+ almost instantly, is the 135V still low? Or is there a signifigant drop as the rest of the tubes begin conducting? This would tell you if it's tubes lugging the 135V down, or something else circuit-wise.

295V DC when first turned on and it held for 4-5 seconds and then took a steady dive down to 104V in the next minute.

[Username1]

Originally Posted by Chris K

I really don't see a smoking gun here except for the lower voltages associated with the reduced 135V line being bled off to another voltage line source.

6SK7 #4 -3.6V #6 96V #8 187V
6SH7 #4 -4.3V #6 104V #8 103V
6SN7a #1 -1.3V #2 68V

.

These voltages are I think pretty far off.... How are the resistors R160, 161, 157, 228, 153, 156, 157....
I'm wondering about the -18, -2, and -100 v sources, as it looks like they are providing bias for all
the little tubies that are also using the 135V & other sources... Higher G1 voltages will
mean all the tubies conduct just a little bit more for each one.... and you know
what that means.... More Ampies being used.... and if the 3 tubies you
provided G1 voltages for, they are each a little higher..... More
ampies means B+'s all go down..... Good suggestion about
monitoring the 135V as the set warms up, I suspect it will
go down as the set gets going, no surprise there...

.

[Chris K]

Originally Posted by Yamamaya42

http://suzaku.live-evil.org/0415202203(1).jpg

pic of the weird brown stuff on the white caps

I don't have those caps in my TV...it has the resistor-like caps all of them in the 6.3V filaments to ground.

[Chris K]

Originally Posted by Username1

.

These voltages are I think pretty far off.... How are the resistors R160, 161, 157, 228, 153, 156, 157....
I'm wondering about the -18, -2, and -100 v sources, as it looks like they are providing bias for all
the little tubies that are also using the 135V & other sources... Higher G1 voltages will
mean all the tubies conduct just a little bit more for each one.... and you know
what that means.... More Ampies being used.... and if the 3 tubies you
provided G1 voltages for, they are each a little higher..... More
ampies means B+'s all go down..... Good suggestion about
monitoring the 135V as the set warms up, I suspect it will
go down as the set gets going, no surprise there...

.

Hello there...from my read of the schematic the volts on these should be:

6SK7 #4 -4.3V #6 129V #8 165V
6SH7 #4 -5.2V #6 135V #8 134V
6SN7a #1 I don't know! #2 88V

As for resistors, 228, 153, 159, 157, 158, 160 all test dead on. I replaced 154 and 155 because they were a smidge high.

[Username1]

.

Yes, and did you not post these readings:

Originally Posted by Chris K View Post
I really don't see a smoking gun here except for the lower voltages associated with the reduced 135V line being bled off to another voltage line source.

6SK7 #4 -3.6V #6 96V #8 187V
6SH7 #4 -4.3V #6 104V #8 103V
6SN7a #1 -1.3V #2 68V

With each G1 a little higher than what the schematic calls for?

Anyway, Please post all the Minus Voltage Sources, I'm interested...
Thanks....



.

[old_coot88]

Originally Posted by Username1

... Higher G1 voltages will
mean all the tubies conduct just a little bit more for each one.... and you know
what that means.... More Ampies being used.

Higher negative G1 voltage with respect to cathode reduces plate current. Plate voltage is in reverse phase to the grid.