a real challange? - Page 13 - Videokarma.org TV - Video

Yamamaya42 · #**181** 03-23-2020, 11:20 AM

As I suspected, Im finding out of tolerance resistors

Mostly the 10% ones, not seen any 5% bad yet, but 40% of the 10s are unacceptable.
Example, 470k tested @ 562k and 330 ohm tested @ 389 ohms.

JohnCT · #**182** 03-23-2020, 01:36 PM

Quote:

Originally Posted by Yamamaya42

As I suspected, Im finding out of tolerance resistors

Mostly the 10% ones, not seen any 5% bad yet, but 40% of the 10s are unacceptable.
Example, 470k tested @ 562k and 330 ohm tested @ 389 ohms.

I don't have a ton of experience on vintage tube gear, but what I've found out is that most circuits will run just fine with well over 20% difference in resistance and capacitance values.

John

Kevin Kuehn · #**183** 03-23-2020, 04:04 PM

Agree about the resistors, although no harm in changing them. You should check the video peaking coils for continuity. Those are the coils in the video detector, video amp, and video output stages. Normally they have a fairly low dc resistance but sometimes go open from aging, more so if the set has been stored in a damp environment.

Yamamaya42 · #**184** 03-23-2020, 08:45 PM

Quote:

Originally Posted by Kevin Kuehn

Agree about the resistors, although no harm in changing them. You should check the video peaking coils for continuity. Those are the coils in the video detector, video amp, and video output stages. Normally they have a fairly low dc resistance but sometimes go open from aging, more so if the set has been stored in a damp environment.

it spent the years from 196x -- 1996 in a basement in Franklin PA, and the rest in a shed in central TX in a box.

Yamamaya42 · #**185** 03-23-2020, 09:31 PM

I'm not so sure about the resistors, I mean...
https://imgur.com/WdcsiK7
this plate resistor is almost 1k too high... Orange , Orange, Red 3.30k is reading 4.23k that really has to be messing with the tube bias

Electronic M · #**186** 03-24-2020, 01:28 PM

I'm not surprised it passes color video passband of monochrome sets was originally 4.5MHz in late 53 they mixed color into monochrome video 3.58MHz and up. And 55 and later models started being designed to limit response over 3.5MHz. Some pre-54 sets actually had color wheel NTSC adapters connected to them with no RF/IF alignment change.

The soild state 5V4 damper may fail in your application... that part was designed for 60Hz guitar amp power supplies its diodes may not switch fast enough for horizontal rate and damper service is at the edge of voltage ratings of the tube...the solid state part may or may not be rated to handle a voltage spike that would harmlessly arc the tube.... I'd stick with a tube unless you are fine blowing the SS part to learn if it works.... Alternatively you could take the base off a dud octal tube, and spec out a diode that will handle what the circuit can supply and make your own.
The current tube in it is likely just fine. Blue glow is usually fine (stray electron bombardment of the glass), but purple/Violet is usually indicative of gas leakage.

Yamamaya42 · #**187** 03-24-2020, 01:53 PM

Quote:

Originally Posted by Electronic M

I'm not surprised it passes color video passband of monochrome sets was originally 4.5MHz in late 53 they mixed color into monochrome video 3.58MHz and up. And 55 and later models started being designed to limit response over 3.5MHz. Some pre-54 sets actually had color wheel NTSC adapters connected to them with no RF/IF alignment change.

The soild state 5V4 damper may fail in your application... that part was designed for 60Hz guitar amp power supplies its diodes may not switch fast enough for horizontal rate and damper service is at the edge of voltage ratings of the tube...the solid state part may or may not be rated to handle a voltage spike that would harmlessly arc the tube.... I'd stick with a tube unless you are fine blowing the SS part to learn if it works.... Alternatively you could take the base off a dud octal tube, and spec out a diode that will handle what the circuit can supply and make your own.
The current tube in it is likely just fine. Blue glow is usually fine (stray electron bombardment of the glass), but purple/Violet is usually indicative of gas leakage.

Well something is not right, cause as of now, I have very low HV, with the new rect tube, I can hardly get 4-5 kv, where it should be 9-10kv.
Be it caused by weak tubes, or really out of tol resistors , not sure, still looking through it for crappy resistors, and IMOH, I can't really see how it can work correctly with ones as bad as I mentioned off the video output plate that's 28.18% off 3.3k :O (not replaced yet, don't have bulk 1w ), but I'm sure I will find others like it

But I can tell that both the HOT & damper have been replaced before, as they are not RCA tubes, where as most every other one in there is, this tends to tell me that of all the tubes that were going to fail in this, they were most likely the first to go, so I tend to suspect them being a problem, but I have no way to try a substitute. So I will try to find new (well, new as I can find,) and see what happens.

Yamamaya42 · #**188** 03-24-2020, 02:33 PM

additional, I think I see a problem already

, Not confirmed yet, just looking at photos I took, cause I'm not at home to check, but R120 does not look very good... (cathode resistor of HOT), missed it before. Will check later.

Yamamaya42 · #**189** 03-24-2020, 04:09 PM

https://imgur.com/ASrbzio

Oh yeah,,, it's bad.
52 ohms R120 is toast...

EDIT
R122 is also bad
what must have happened, C90 went bad and took out the resistors, no wonder i have weak HV :/
i need a set of 1w resistors now

Yamamaya42 · #**190** 03-24-2020, 10:30 PM

what I don't get is why do they have the Parallel resistors on g2 on the HOT, 22k & 18k...
does it have to be EXACTLY 9.9k there? or would a 1 10k 2w work fine?

I mean, right now they have the 2 in Parallel , both 1w, the 18k is very bad, so i gotta replace both, do I have to put them back exactly as they were? or will 1 larger one do?

Kevin Kuehn · #**191** 03-25-2020, 02:08 AM

Quote:

Originally Posted by Yamamaya42

I mean, right now they have the 2 in Parallel , both 1w, the 18k is very bad, so i gotta replace both, do I have to put them back exactly as they were? or will 1 larger one do?

Hard to guess why they did that other than parts availability and wattage. I'd be comfortable with a 10k metal oxide in that location, although I'd be tempted to bump the wattage up to 5, just to give it an easy life. But in theory modern film and oxide resistors can endure more heat per surface area than the old carbon composition variety.

Yamamaya42 · #**192** 03-26-2020, 10:57 PM

the horizontal output tube is most likely bad / weak, replaced the bad ( scorched ) cathode resistor 100 ohm, tested @ 45, replaced the pair of G2 resistors with a large 10k, All voltages look OK and match what is shown in RCA 630ts service manual, Cant measure plate voltage with it running, but with wire removed, its 318v at the wire.
the waveforms even are pretty much spot on what is shown in the 630ts service manual for the HOT, so all that is left is a bad tube

Yamamaya42 · #**193** 03-27-2020, 04:38 PM

ummm, is this a problem, i really hope not, cause if it is, I'm screwed.

https://imgur.com/x1izfje

between point 2 -3 I get 250 ohm on a DVM but from 1 - 2 it's 95.6 ohms.
is the FBT bad ? T_T

there has been no red plating of the HOT..

JohnCT · #**194** 03-27-2020, 06:54 PM

Quote:

Originally Posted by Yamamaya42

ummm, is this a problem, i really hope not, cause if it is, I'm screwed.

https://imgur.com/x1izfje

between point 2 -3 I get 250 ohm on a DVM but from 1 - 2 it's 95.6 ohms.
is the FBT bad ? T_T

What I would do is see if there's an alternate schematic of the TV, like a SAMS or Riders to be sure it's not a mistake. Otherwise, it looks like you have some adjacent turns shorted.

A ringer would show that, as would something like a B&K analyst or Sencore VA48 etc. that would drive the flyback directly.

John

EDIT: that looks a lot like a 630, and that looks like RCA's drawing... If it's a clone, then RCA also has 180 ohms for that part of the winding.

Yamamaya42 · #**195** 03-27-2020, 08:11 PM

Quote:

Originally Posted by JohnCT

What I would do is see if there's an alternate schematic of the TV, like a SAMS or Riders to be sure it's not a mistake. Otherwise, it looks like you have some adjacent turns shorted.

A ringer would show that, as would something like a B&K analyst or Sencore VA48 etc. that would drive the flyback directly.

John

EDIT: that looks a lot like a 630, and that looks like RCA's drawing... If it's a clone, then RCA also has 180 ohms for that part of the winding.

then this has quickly become a lost cause, and wasted time and effort, as the chances of finding a replacement a pretty much none, unless there some how a way to fix it, which i really doubt..

this really sucks