#16
|
||||
|
||||
Quote:
Dave Last edited by Zenith6S321; 01-21-2017 at 05:33 PM. |
#17
|
||||
|
||||
Last page.
|
#18
|
|||
|
|||
Quote:
According to Sams, it's stated as resistance wire. It's a small guage solid wire, instead of stranded wire, like used on practically all the flybacks, that I ever replaced. I don't know, how much voltage drop is required, as Sams doesn't specify a resistance value. |
#19
|
|||
|
|||
Quote:
All the HV rect filamant loops I ever replaced were standard anode wire. Occasionally there was one (usually B&W) that had a small resistor of a few ohms in series with the fil. This was always in other brands than Zenith. Last edited by old_coot88; 02-17-2015 at 08:57 PM. Reason: typo |
#20
|
||||
|
||||
Thanks everyone, and special thanks to Dave with the pages posted. This turned out to be a great thread that I think will be an excellent source in the future for others. I think I am far from the first to be hunting a corona or arching issue which just can't be seen; even in the dark.
As I have said before; I don't know if I would ever have found this if the damage from the arching hadn't burned my rectifier socket causing a pin to pull with the tube and leading me into further investigation.
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
Audiokarma |
#21
|
||||
|
||||
Quote:
"The most common cause of vertical fold-over is failure of the vertical oscillator output tube. Vertical output grid coupling capacitor being shorted or leaky can cause improper operation of the vertical output tube, causing vertical fold-over." So maybe replace the grid cap and try some other vertical output tubes? Dave |
#22
|
||||
|
||||
Quote:
Dave |
#23
|
||||
|
||||
Thanks for extra pages and tips! Lot to try here.
|
#24
|
||||
|
||||
Quote:
I still can't help but wonder how I had HV with the resistor burned in two. My only guess is that it was arching across the two burned open ends of the resistor. The burned out socket (pins 4 and 5) as well as same tube pins badly corroded may be further evidence backing this theory. Heck, pin 4 is a blank! Beyond a shadow of a doubt the resistor didn't burn any of the last number of times the set was in use. Beyond the resistor topic my immediate concern will be that of HO cathode current being high at line potential. I doubt that this repair will correct that, but all of this is a learning process for me. Perhaps the issues mentioned and soon to be corrected do play a hand in that. I will know as soon as the socket arrives (hopefully later today). Lots of snow here for this part of the country which makes for a perfect day to work on electronics projects.
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#25
|
||||
|
||||
Quote:
I see the 25LC schematic AC input is designated 120v - within spec of modern utility voltage. Was looking for "troublesome" degaussing thermistor and found the 25LC20's have no automatic degaussing coil Last edited by NewVista; 02-17-2015 at 10:49 AM. |
Audiokarma |
#26
|
||||
|
||||
This may sound ridiculous, but I have to ask if anyone can verify some 3AT2 pin outs for me. Simply what I need to know is whether the jumper replacing the 1.5K resistor joins at pin #4, or pin #5 along with the crt second anode lead.
As I have said, my sockets connectors 4 and 5 both fell out, but when I first pulled the tube and discovered this I thought that #4 came out with the tube and had nothing soldered to it. The new socket has the resistor and anode lead at pin #4 which again is a blank pin. I am probably just mistaken about which connector came out with the tube. The blank pin is probably just used as a junction for the "series" resistor. If it went to #5 then it looks like both ends of the resistor or jumper would be across or shunted to the cathode by looking through the glass. I just want to wire this up right the first time and need to be sure. The schematic only shows the heater connections and plate cap. Thanks!
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" Last edited by Tubejunke; 02-17-2015 at 07:26 PM. |
#27
|
||||
|
||||
The 25MC30 schematic shows the 1.5K resistor connects to pin 1 and 9 of the 3AT2. The 3AT2 PDF shows that pin 4 is a no connect. So pin 4 could be used as a tie point for connecting the other end of the resistor to the anode lead. The schematic does not show this, so I'm guessing.
Dave 3AT2 PDF: http://frank.pocnet.net/sheets/049/3/3AT2.pdf |
#28
|
||||
|
||||
OK, I just figured out that I have been using Sams Set 722, Folder 4 which is for the 25LC30/U! Geez! It only specifies pins 1 &12 as heater connections. Mistake #1! Either way, like you I am assuming that the NC #4 is indeed a tie point as #5 certainly would not be right. I need to get a .pdf on my 25MC30 somewhere. However, it shows pins 1 and 9 according to what you are seeing and that would still have the resistor shunted to the cathode as the.pdf states, "pin 5 same as pin 1."
I hope I am correct in thinking like you that only one end of the resistor would be at the cathode, or pin 9 and the rest simply goes to second anode at CRT.
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#29
|
||||
|
||||
Quote:
__________________
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 |
#30
|
|||
|
|||
Quote:
|
Audiokarma |
|
|