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  #46  
Old 11-29-2018, 10:58 PM
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Quote:
Originally Posted by old_coot88 View Post
Doesn't the '25 have a Kine Bias switch? If so, it might be dirty. Try cycling it a few times with a shot of cleaner.
Could be... its been about 2 years since I last saw the inside/back of one...
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  #47  
Old 11-30-2018, 04:29 PM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by old_coot88 View Post
Doesn't the '25 have a Kine Bias switch? If so, it might be dirty. Try cycling it a few times with a shot of cleaner.

Yes it does. The thing is it had everything working when I brought it home. Niw that ive done work on it i have this to figure out.

I replaced the boost diode with a 1n4007 and this other diode labled ge gecr-2 with a 1n5408. I also replaced a few small value e caps here and there.

Last night i was wondering why the h output current would go up 50+ma with the hv rectifier in circuit so i swapped the 6bk4 shunt regulator with a 6el4 and a fat (i wanna say 10 watt) 600 ohm resistor under the shunt reg started going up in flame. The leads were green anx corroded looking. So now i have that to clean up.

I do know theres hv at the fly output though.
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  #48  
Old 11-30-2018, 06:37 PM
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You should get a HV meter or probe capable of measuring at least 30KV...The difference between 18KV, 25KV and 32KV is hard to discern drawing an arc, but can be the difference between no picture/slowly killing the CRT by drawing too much current to achieve normal brightness, normal operation, and the fly arcing and shorting internally...In some cases, wrong HV can be much worse than excessive H output current.

May want to check your HV rect is not shorting. If you have HV AC going to the CRT you will be able to draw an arc, but you won't have a picture.
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  #49  
Old 11-30-2018, 06:45 PM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by Electronic M View Post
You should get a HV meter or probe capable of measuring at least 30KV...The difference between 18KV, 25KV and 32KV is hard to discern drawing an arc, but can be the difference between no picture/slowly killing the CRT by drawing too much current to achieve normal brightness, normal operation, and the fly arcing and shorting internally...In some cases, wrong HV can be much worse than excessive H output current.

May want to check your HV rect is not shorting. If you have HV AC going to the CRT you will be able to draw an arc, but you won't have a picture.
Well I did "test" the hv rectifier but that doesnt necessarily mean much, especially for sweep tubes were the tester doesnt even scratch the surface of the tubes operating range. I will think over what youve said.
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  #50  
Old 12-04-2018, 06:55 PM
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[QUOTE=Electronic M;3206251]You should get a HV meter or probe capable of measuring at least 30KV...The difference between 18KV, 25KV and 32KV is hard to discern drawing an arc, but can be the difference between no picture/slowly killing the CRT by drawing too much current to achieve normal brightness, normal operation, and the fly arcing and shorting internally...In some cases, wrong HV can be much worse than excessive H output current.

I got a two size plastic hex tool in my possession now. I also have a NIB Rca 3a3c hv rectifier coming in the mail. So now I can correctly adjust coils without breaking them.
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  #51  
Old 12-16-2018, 11:33 PM
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Well I believe Im on the right trail diagnosing this problem. I have my nib sylvania 3a3c, a thordson nib horiz eff coil, and my hex tool. I was looking at the schematic thinking why after it warms up the cathode current becomes excessive. So I thought I should make sure everything between the horz oscillator and output tube is in order. I found a .01 cap going to the grid of the horz op tube. Said cap had broken solders. So Ive stuck a new .01 in place. Also I plucked the damper tube and noticed little cruddies shaking around in it. My precision 10-12 cant test compactrons without an adapter but I dont think little bits of crap jingling around in a tube is a good qaulity. I dont have another tube so I have not fired it up again to see if thats made a difference.
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  #52  
Old 12-21-2018, 04:32 PM
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The damper tube may be OK but a 6DW4/6CJ3/6CK3/6CH3 is easy to find. I have too many. I scrapped many RCA's with bad flys over the years. It also sounds as if the 2AV2 is shorted, if it pegs the tester meter

Have you monitored the DC voltage on the 6JE6 grid? Usually the more negative it is, the lower cathode current would be. There are several .033-.068? caps across the horz eff coil too, which could cause it not to "dip" properly.

I have been able to lower the current in all post-CTC11 RCA's (not sure why yours increases beyond 220) by switching to the high line voltage tap on the power transformer primary.
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Last edited by DavGoodlin; 12-21-2018 at 04:37 PM.
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  #53  
Old 12-30-2018, 02:37 PM
ZenithNut ZenithNut is offline
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Originally Posted by DavGoodlin View Post
The damper tube may be OK but a 6DW4/6CJ3/6CK3/6CH3 is easy to find. I have too many. I scrapped many RCA's with bad flys over the years. It also sounds as if the 2AV2 is shorted, if it pegs the tester meter

Have you monitored the DC voltage on the 6JE6 grid? Usually the more negative it is, the lower cathode current would be. There are several .033-.068? caps across the horz eff coil too, which could cause it not to "dip" properly.

I have been able to lower the current in all post-CTC11 RCA's (not sure why yours increases beyond 220) by switching to the high line voltage tap on the power transformer primary.
Dave and Electronic Memory a little bit of progress has been made!

I replaced one cap between the h osc and hor output, i replaced the hor eff coil I broke with a metal tool, now i have a plastic one . I replaced the 3a3 hv rect and 6bk4 shunt tube. Also subbed the 2av2. I swapped the damper and hor osc. I cleaned up the fire works show under the shunt tube. I hooked everything up and fed my nes into the vhf side of the tuner with a coaxial to uhf splitter.

Fired it up. This time as the hv comes up it goes between 200-240 ma instead of climing up to 300ma! I didnt have the anode cupped into the crt all the way and saw crazy high voltage. I shut it off and planted the cup in better.

So NOW theres still no sound, video, or vert/hor deflection BUT when you turn the set off theres a flash of something.

Also I can hear the hv forming around the cup of the flyback. Maybe I need to add another layer of silicon because it seems theres lots of corona forming.

Im afraid to keep it on longer than for the hv to come up because I dont know what its gonna do if I keep it on.

I will check voltages maybe with the hor output tube pulled out that way I can run it and check the B+ without being a nervous wreck.

I am happy to see the cathode current peak at 240ma instead of 300ma.

Edit: Ive been getting so worked up working on this thing I havent even checked B+ at the power supply or any screen voltages. Thinking of basic routine checks has been over shadowed by an almost fear/excitement combo. I will check B+, screen voltages, etc.

Last edited by ZenithNut; 12-30-2018 at 03:04 PM.
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  #54  
Old 12-30-2018, 03:17 PM
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Good to hear you're making progress.

Definitely check your B+, h out screen and grid voltages, and report back...

Tip: if you have more than 1 meter you can grab multiple voltages at once with clip leads...if you have enough insulated color coded clip leads but only 1 meter, are careful and have plenty of cahoonies you can put a clip on every test point you care about and hot swap the meter... gotta be very careful not to touch anything conductive, but it can be done, and I have done it

Don't let the set freak you out of a logical state of mind.
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  #55  
Old 12-30-2018, 03:49 PM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by Electronic M View Post
Good to hear you're making progress.

Definitely check your B+, h out screen and grid voltages, and report back...

Tip: if you have more than 1 meter you can grab multiple voltages at once with clip leads...if you have enough insulated color coded clip leads but only 1 meter, are careful and have plenty of cahoonies you can put a clip on every test point you care about and hot swap the meter... gotta be very careful not to touch anything conductive, but it can be done, and I have done it

Don't let the set freak you out of a logical state of mind.
Thanks Tom. Its just because its a color tube set. I can play around with my tube zenith bw or my radios and fisher hifis and im a okay.
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  #56  
Old 12-31-2018, 03:42 PM
ZenithNut ZenithNut is offline
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[QUOTE=Electronic M;3207025]Good to hear you're making progress.

Definitely check your B+, h out screen and grid voltages, and report back...

Here are my results for measuring the B+ supply

Secondary winding ohmd out correctly at 7.3 ohms, 350VAC about 20v high.

Now the rest is just totally off.

B+ 1 455v

2 454v

3 436v

4 375v

5 372v.

6 288v

Its all jacked up. On pins 1-7 for the hor output grid theres 432v even though theres two resistors between the screen and B+ supply where its suppose to drop to 140v ! Pin 8 calls for -55v and its 27 volts positive. Dont get me started on how wrong the crt voltages are too.

I know bad E caps will cause low B+ but what about this?
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  #57  
Old 12-31-2018, 06:40 PM
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B+ can safely vary by 30 percent in most tube TVs.

Your h out grid being positive instead of negative is very bad, and usually means your oscillator is dead or not feeding the grid. If the h out screen is high it usually means the plate is drawing far too much current.... this makes sense since if your grid is not negative enough plate current will be high(and positive grid will red plate the hot).

What I'd do in your shoes is disconnect the plate and screen of the h output and work on the osc until the output grid goes negative. The grid gets negative by rectifying the drive signal from the osc...if you unplug the grid or cathode of the output a negative voltage will not develop at the grid.
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Last edited by Electronic M; 12-31-2018 at 06:44 PM.
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  #58  
Old 12-31-2018, 07:31 PM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by Electronic M View Post
B+ can safely vary by 30 percent in most tube TVs.

Your h out grid being positive instead of negative is very bad, and usually means your oscillator is dead or not feeding the grid. If the h out screen is high it usually means the plate is drawing far too much current.... this makes sense since if your grid is not negative enough plate current will be high(and positive grid will red plate the hot).

What I'd do in your shoes is disconnect the plate and screen of the h output and work on the osc until the output grid goes negative. The grid gets negative by rectifying the drive signal from the osc...if you unplug the grid or cathode of the output a negative voltage will not develop at the grid.

Not sure I follow all the way. Disconnect the supressor grid and leave the grid thats supposed to be negative connected?

Also the b+ voltages are way off. Like for B+ 5 is supposed to be like 125v and its almost twice that. Its supposed to drop down ex 420 to 400 to 375 to 350 to 275 so on.
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  #59  
Old 12-31-2018, 07:44 PM
ZenithNut ZenithNut is offline
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So on 6je6 theres three grids which exact one do I disconnect along with the plate?. Im not surprised the osc isnt running because all those voltages are WAY off too

Also I took the voltage measurements for the h output with everything in place including the osc but none of the plate voltages or grid voltages are right.
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  #60  
Old 12-31-2018, 08:50 PM
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I'd disconnect 1-7 and maybe pin 8...You could probably leave them connected for short powerups. The issue is that the screen grid will act like a plate if the plate is disconnected (or presents a higher resistance path, such as when the damper tube looses emission) and there will be screen current in excess of the dissapation specs damaging the tube on extended powerups.

The high B+ voltages are interesting. I no longer have a schematic for this chassis so without schematic voltage figure I can only gestimate how high the voltages are.

Be aware that the flyback is a large portion of the load on the B+ system, and when it is not drawing any current the B+ will be high. Also these sets have no B+ regulator circuits and expect around 115V input....If your line voltage is say 120V or higher, then that will also help push the B+ above spec.

The lower voltage rails may have reduced load on them from other circuits not drawing current...Vertical, audio out, and video amps are among the higher current loads on the lower B+ rails in most sets.
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