#16
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Last edited by andy; 11-20-2021 at 03:43 PM. |
#17
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yes i did check L14 the ohms, compaired to the sams. if im correct i didnt cut it from the circuit i just measured the ohms and it was where it should be so i didnt feel i should remove it from the circuit.
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#18
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Quote:
Last edited by timmy; 01-01-2015 at 03:17 PM. |
#19
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You have a HV problem, then. Start looking at the horizontal section or HV rectifier.
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Evolution... |
#20
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Last edited by andy; 11-20-2021 at 03:42 PM. |
Audiokarma |
#21
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Perhaps the HV reg resistors or caps that tested good on low voltage test equipment break down and stop working at rated voltage.
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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 |
#22
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well i already tried a solid state 3a3 rectifier, no difference. i also checked the hv regulator resistors and they checked at 1.6m and 1.59 close enough to 1.5 meg. the funny thing is first getting this set from the beginning the hv was a problem so since then i changed all the caps under the chassis with no change in the hv regulation including the flyback. i thought i found the problem when i changed the fly when i found the focus 1v2 was wired wrong but that didnt help after correcting that. i had thought there was a problem somewhere in the crt drive circuit chroma board or somewhere else affecting the regulation of the hv but im all out of options as to where to look. i was trying to cover as much as possible befor pulling the crt and swapping to rule it out because i am limited to room here and yet the crt in the set tests very good for the age.
Last edited by timmy; 01-04-2015 at 06:58 AM. |
#23
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Last edited by andy; 11-20-2021 at 03:42 PM. |
#24
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lol,lol, thats just it i dont know anymore whats going on with the set. and yes i have to swap the crt and if another crt does the trick then ill be amazed at what may be wrong with the other seeing as it tests great. but it could be alittle gassy enough to create this problem and that would be a real shame because it does test good.
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#25
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Quote:
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Evolution... |
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#26
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well with my on going hv issue with this set i do have a question. with the set on hv present at anode crt plug off should there be any voltage at any of the crt pins. i checked with a dvom to ground and have no voltage at all except at the focus pin which was 7 volts , would this sound right ? and the hv with the anode wire off the crt is 19kv just at the wire. anode wire back on, crt plug off i was lucky to get 22 kv, thats it, picture scene changes and will dip right down to 19 kv or less. i didnt try another crt yet but was looking around for something concrete here that may give me an idea the crt is finished maybe due to gas. i read an article online about crts and what was said about getters is that a bright shiney mirror like getter is good no air or gas. however what also was said was that a white of course means it took on air but the last was a getter that is coal black no mirror shine at all indicates gas in the tube. has anyone heard of this coal black getter meaning a gassy crt ?
Last edited by timmy; 01-09-2015 at 11:22 AM. |
#27
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Unless white there is no sure indicator, looking at getthers, of gas.
__________________
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 |
#28
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Well if it's 19kv with no load, you've got a chassis problem. It should shoot up to the setpoint of the shunt regulator and stay there with no CRT attached, does the HV pot do anything in that state?
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Evolution... |
#29
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the hv pot adjust does seem to work but to get even 19kv the pot has to be maxed. there is nothing else i can seem to look at as i looked at what seems to be everything already and have not found anything wrong. so if its a chassis problem then i am overlooking something here. or it is infact the crt. i thought the hv without connected to a crt will be limited because the crt acts like a capacitor so being off the crt 19kv sounds maybe like thats all i would get, i dont know at this point. but then again hooked back up to the crt i would think it would shoot up but didnt. does anyone know the leads that come of the hv regulator tube as to which one if there is a specific lead that does the triggering of the regulation, maybe a specific lead from that tube i can trace if this lead is used as some kind of reference for the hv regulation. because this hv just sits dont raise up just dips as if there were such a wire were cut.
Last edited by timmy; 01-10-2015 at 08:04 AM. |
#30
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the HV adj should not "seem to work" it should work, in a very linear fashion.
Disconnect the pot from the circuit and confirm (preferably with an analog ohm meter) that it is working as it should (500k to near 0 resistance as you adjust). Confirm the voltage readings at the shunt tube grid and cathode, make sure the grid varies with the pot. Confirm the total bias of the shunt tube is within specs of the sams. At some point I recall you saying the HV would go to 30kv with out the CRT anode attached. If now you are saying the max is 19kv without the CRT attached then only 3 things can be wrong. Remember you are working with high voltages all over the place (400v around the cathode and grid of the shunt, 30kv at the anode) so be careful. 1) bad shunt tube 2) bad shunt tube bias 3)no loner getting 30kv with shunt tube disconnected. |
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