|
|
|
#151
12-20-2016, 04:57 PM
|
|||
|
|||
|
Here is the HV lead going to the CRT. I used some 20KV wire and a connector and boot from an old color portable TV gotten free from the curb. I replaced the 40KV wire with my 20KV wire and put the 470K resistor in line like the instruction sheet had shown. I double heat shrunk the whole assembly. I also replaced the 20awg standard hook up wire from the 1X2A rectifier tube to the door knob capacitor because it was carrying full HV with the same 20KV wire. The terminal on the tube socket was also double heat shrunk.
I know the instruction sheet shows the resistor directly connected to the door knob cap connector, but I thought using a small piece of 20KV wire which is stranded, it would hold up better to any movement. What do you think? I'd prefer that the resistor was hard mounted to some phenolic or terminal strip but it does look like it'll work. I'm including a picture of the portion of the instruction sheet.  
Last edited by Crist Rigott; 12-20-2016 at 05:02 PM. 
|
|
#152
12-20-2016, 05:14 PM
|
|||
|
|||
|
Here's is another "kooky" thing about this kit.
They talk about "Insert a polyethylene sleeve over the 1X2 tube and socket." on instruction sheet 6 after all the steps have been completed. Here are a couple of pics of the supplied sleeve and the note on the instruction sheet. I'm guessing that the sleeve it there to prevent a shock to service people rather than to prevent arc over. Could be both though. The sleeve reminds me of the container we used to get aviation spark plugs in. I'm thinking I have to cut the crimped end off and just slide the rest in place. No mention as to how it is secured. Could I just double heat shrink each tube socket terminal and accomplish the same thing? Is there any other way that I could use?   
|
|
#153
12-20-2016, 08:13 PM
|
|||
|
|||
|
OK, I cut the crimped end off of the sleeve and slid it home. Then I tied it off with some lacing cord. Not as goofy as I thought. It has to be used to prevent arc over because the HV is exposed on the end of the door knob cap.
  
|
|
#154
12-21-2016, 12:25 AM
|
|||
|
|||
|
Wahoo!
|
|
#156
12-21-2016, 09:40 PM
|
|||
|
|||
|
Thanks KV.
|
|
#157
12-21-2016, 09:48 PM
|
|||
|
|||
|
OK, first problem.
I can't get the CRT into good focus. The yoke is pushed all the way forward up on the CRT. This is an aluminized tube so no ION Trap. HV is shown at 11KV on my unreliable HV probe. I did notice this statement from the GE datasheet for a 21FP4/A/C, the CRT I'm using is a 21FP4C. It states having a minimum resistance on Pin 6 (Focus) and Pin 10 (Grid 2 B++). See attached photo. This TV does not have a minimum resistance on pin 6. it goes directly to B-. Should I have at least a 100K resistor in there?  
|
|
#158
12-21-2016, 11:33 PM
|
|||
|
|||
|
At another persons suggestion, I tried taking pin 6 (Focus) from B- to B+ 130v and to B++ 300V with no joy.
|
|
#159
12-22-2016, 10:15 AM
|
|||
|
|||
|
Compliments once again on your outstanding workmanship sir.
 But offhand, it seems a minimalist, low-B+ design chassis trying to drive a large CRT is not going to deliver optimum performance, particularly with only 11KV on the anode (if your HV meter is correct).Try this for a moment.. short out the resistor feeding G2 (screen grid) of the 25CD6 to raise G2 voltage a bit. See if this improves HV, width and focus at all. If it does, it suggests that a higher B+ supply voltage on the H output/damper circuit would improve performance. If it doesn't, then maybe a smaller CRT would work better with this chassis.
|
|
#160
12-22-2016, 10:51 AM
|
|||
|
|||
|
Quote:
I would only halve the G2 resistor, another one in parallel. All the low B+ larger screen sets I worked on, seemed to use a 25DN6 instead of a 25CD6. IIRC, Sylvania designed the tube for that purpose. It looks like the tube in your set is the old style 25CD6G. After the resistor trick, the first thing I would try is a 25DN6. 
|
| Audiokarma |
|
#161
12-22-2016, 12:02 PM
|
|||
|
|||
|
Actually the 25CD6 and 6CD6 are identical except for heater ratings.
http://www.datasheetarchive.com/dl/4...3319916/O/6cd6 Last edited by old_coot88; 12-22-2016 at 12:06 PM.
|
|
#162
12-22-2016, 12:41 PM
|
|||
|
|||
|
Quote:
I tried another 470 Ohm resistor paralleled with R63 which is connected to pin 8 of the 25CD6. No joy then I added another resistor in parallel and still no joy. The schematic does list a 25DN6 in parenthesis next to 25CD6.
|
|
#163
12-22-2016, 12:43 PM
|
|||
|
|||
|
I have the proper HV probe to go with my VTVM on order. It'll be here within the week. then I'll know for sure what the HV really is.
|
|
#164
12-22-2016, 02:45 PM
|
|||
|
|||
|
If nothing else pans out, I would try this as 'proof of concept' for raising B+ voltage feeding the H.sweep circuit: String a few 9V batteries in series, and put this in series with the +130V going to the plate of the damper tube.
If raising B+ improves HV, focus, and width, then consider building a small dedicated supply to put in place of the batteries. Just a thought. 
|
|
#165
12-22-2016, 03:30 PM
|
|||
|
|||
|
I thought I'd do a voltage check according to the schematic. I found some voltages out of wack!
I started with V15 Vert. Output and went down. Here's what I found. First volt listed is what the schematic says, the second is what was measured. V15 Vert. Output - 3 Plate 125V - 119V 4 G2 130V - 129V 8 Cathode 17V - 15V V14 Vert. Osc. & Sync Limiter 5 Plate 130V - 55V V13 Horiz. Damper 3 Cathode 350V - HIGH VOLTAGE! Blew out my MM which was set at 1000VDC V12 Horiz. Output 5 G1 -25V - -22V 8 G2 125V - 120V V11 Horiz. OSC. & Phase Det. 1 G1 -46V - -41V 2 Plate 155v - 142V 4 G2 20 - -9V 6 Cathode -10V - -6V V15 looks good V14 Plate voltage is low V13 Wow, blew out my MM V12 looks good V11 Pin 4 G2 voltage is wrong Last edited by Crist Rigott; 12-22-2016 at 03:51 PM.
|
| Audiokarma |
 |
|
|
Linear Mode
