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#1
09-30-2022, 03:18 PM
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I really don't understand what you are trying to say, there is no “setting” of the -45v on the grid of the HOT, and that is not an absolute value by any means, it is a general voltage in DC, that means the horizontal oscillator is running.
There is no current measurement there. DC voltage only. The ONLY current measurement is cathode current, and this is done through a coupling cap AND a current meter for both tubes independently, but only when the set is up and stable. The meter you have does NOT have the range to do the cathode current test, so don't try. I'm not sure what you were attempting, but nothing but dc voltage measurements should be done on the grid of the HOT.
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=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために 
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#2
09-30-2022, 03:19 PM
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This tv is a huge cluster fxxk I tried 2 new hot no different and I tried a new 3at2 no different oh and now the 3 b+ voltages are low 275 is down 15 v 190 down to 185 and the 145 down to 138v this is nuts all I did was the 680k and that’s it.
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#5
09-30-2022, 09:06 PM
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That is not how horizontal is adjusted on the set, in fact -45v is not an adjustment at all, but as I indicated, an voltage that shows that the oscillator is running and does not have to be exact, the frequency, timing and waveform there is what matters, and this is set by horz hold and hoz afc.
The ONLY measurements in the area are at the cathode of the HOT, and you do not have the meters to do this, you would need 2 meters that can measure current up to ½ amp, and do both tubes at once, cutting pin 2 from ground and putting a .47 uf cap from pin 2 to ground on both, and then measuring the current across that cap 120ma, both, but since this set does not seem to have a horizontal efficiency coil to adjust, this is not needed on this set. What ever mistake you did in this, you most likely cremated your damper tube, and it will need to be replaced, it is rather weak and easy to damage, much more easy to hurt than the outputs.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#7
10-01-2022, 11:30 AM
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Certainly possible. I have a Silvertone CTC-15 clone that would short it's damper and completely loose HV if the horizontal frequency went too far off...It blew at least 2 good tubes when I was working on it. That was the first color set I restored to working and it sat a few months with dead HV because until I borrowed the damper for another set I and discovered it had failed I didn't retest it because it tested good before I lost HV.
That same set later had a weak damper that would test great unless you held the test button down for like 30+ seconds to get it to slump. That weakness caused unusably low HV. Some problems are spooky in that the failed component WON'T test bad unless subjected to conditions more extreme than the normal use case of the test equipment.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#9
10-01-2022, 03:43 PM
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Hi!
A few observations.... 1. When the Horiz Output tube in Timmy's set gets red plates, it's most likely due to a poor horiz drive to G1, from improperly working Horiz Osc. Remember the damper rectifies the collapsing coil field and makes the current available for use in other circuits. It may be a good idea to replace it anyway since it does a lot of work..... 2. Timmy states that he adjusts the -45V to the G1's of the Horiz Output Tubes. He does this with the Horiz. Hold control. By adjusting the frequency the resulting bias on the G1's of the Horiz Output tubes moves closer to normal. Is it a good thing? Who knows. - but it should keep the output circuit safe. Best idea would be that when he feeds a signal to the tv and it gets a picture that locks, after that leave it alone. 3. Yamama suggested that once the tv gets a picture and the HV is normal, PS Voltages are normal, that Timmy leave it alone for hours and see how long it runs like that. - I Like that idea a lot! You really need to determine what causes the two states that this tv operates at, A) Semi-Working, and B) Low HV and Red Plate HV Output tubes... What causes these 2 states? Is it taking the chassis out? Putting it in? 4. AGC, a normal tv will work without HV fluctuating with an overloaded signal, and with no signal at all it gets snow, and in both conditions no glowing plates on the horiz output tubes..... One thing Timmy needs to do is measure the AGC line voltage when the tv is working and when it's in its Overheating tube state and see if there is a difference. If so, then you need to set up a battery that can force that line between the 2 levels and see if the AGC is the ultimate cause of this TV taking 34 pages to track down this problem. Could the AGC be causing IF circuit tubes to be drawing too much current? If you are going to order a new damper tube, then order a Voltmeter with 10A Current scale too, and get one that is NOT Auto-range, get one that you have to turn the dial to read 10A, 2A, etc. I'll say it again with a 10A Scale, the resistor inside the meter is actually a piece of wire with almost 0 ohms, and you will have almost 0 resistance added to the circuit when you measure 500ma, or 1/2 Amps. .
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Yes you can call me "Squirrel boy"
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#10
10-01-2022, 06:23 PM
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Not sure where we are now but.......
To measure H Out current you need to open the cathode pin from GND and put a ampmeter in series with it. Depending on the meter you should decouple the cathode with a cap to smooth it out. It goes in // with the meter. SAMS has instructions on value of cap & procedure. Adjusting the H. osc ( hold) will effect the G-1 negative voltage. Keep in mind the whole thing by design needs to be in resonance to be happy. If the G-1 is in spec you are good till that point. A freq counter or scope can show you if its at 15,750. AGC as a rule goes to the RF amp & IF # 1 & 2. SAMS will show AGC voltages either with or without a strong signal or both ways. AGC problems are VERY rare, I cant really remember many in 40 yrs & tens of thousands of sets. 73 Zeno  LFOD !
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#11
10-01-2022, 06:31 PM
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Quote:
As mentioned above, this set does not have a horizontal efficiency/linearity coil to adjust, so where the cathode current can be measured, there is no way to adjust it on this. and yes AGC problems are rare, they do happen, bit in this case, it's more likely the IF alignment is messed up.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために
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#12
10-01-2022, 06:50 PM
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Tomorrow I’m going to check resistances on the 6hs8 according to sams. when I had this running the agc control on the rear turning both ways made no difference at all but the noise gate did I do get video but it is distorted but can see images so since making k1 will see what this does. There is a .4 v rf source to agc if that’s missing from the tuner I don’t know what the consequence is if that’s not there.
Last edited by timmy; 10-01-2022 at 07:01 PM.
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#13
10-02-2022, 10:47 AM
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Checked resistances on 6hs8 they are all wrong even with the couplet I made up tried it anyway and it seemed to make it worse. I don’t know if the couplet all together would have to be potted I did incapsulated it in heavy heat shrink.
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#14
10-02-2022, 01:04 PM
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Quote:
I don’t think that the potting is important. jr
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#15
10-02-2022, 02:14 PM
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My mistake I had to measure from x2 not x1 and it turns out they are all good. But the voltages are not right at all 6hs8 pins 6-145v 114 7-200 119 3-2.5 8.3 8-230 143 9-140 31 2- 275 1-190
Last edited by timmy; 10-02-2022 at 02:42 PM.
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