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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Fri 09, 2018 4:47 am 
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Location: Central Illinois
Looks like my dumpster diving is payoff again. Volts are higher than needed on the .000005 but is an NPO type.
C217 replacement
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GE806-40.jpg
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C214 replacement
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GE806-41.jpg
GE806-41.jpg [ 117.57 KiB | Viewed 138 times ]

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Fri 09, 2018 5:09 am 
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Nice! If you can, good idea to test them before installation. Those could be nearly as old as the TV. :wink:


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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 4:46 am 
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I don't have a tester for caps that small of value. Getting C217 cut loose sure did bring up the volts in the whole set. I have a new 5mmf jumped in with test leads and have this for volts,B+ 150v line is now 165v B+ 265 line is now 305v and B+ 275v line is now 320v. Volts on top of R219 is now 96v. Looks like I could add some more ohms ahead of my new diodes.
Attachment:
GE806-42.jpg
GE806-42.jpg [ 138.76 KiB | Viewed 113 times ]

Still have about the same on the screen.
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GE806-43.jpg
GE806-43.jpg [ 109.63 KiB | Viewed 113 times ]

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 5:13 am 
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Here is a pic that shows the offending cap. I cant get to the bottom end to cut it of so far with the tools I have on hand.
Attachment:
GE806-44.jpg
GE806-44.jpg [ 192.06 KiB | Viewed 111 times ]

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 5:21 am 
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Great that the voltages went up. Of course you will need to install the new cap
so that it has very short leads.
It sort of looks like corrosion might have been a factor.

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 5:34 am 
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Frequenceme wrote:
Here is a pic that shows the offending cap. I cant get to the bottom end to cut it of so far with the tools I have on hand.


Very good. Have you verified your voltages are now closer to correct on pins of V3A?

It would be interesting to see if you're getting a change in automatic gain control voltage corresponding with signal input to the set. To determine that you could measure dc volts at pin 1(grid) of V4(1st IF). You should see the voltage change when your rotate the contrast control through it's range, and even more change when you disconnect your signal from the sets antenna input. If you have that change in voltage when disconnecting the signal from the antenna input, it's then safe to assume you're getting signal though the video IF stages and it's being detected by V7A (video detector).


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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 5:56 am 
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The clip leads are going to act as both capacitors and coils. So the tuned circuits are going to be tuned very far from the correct frequencies. Quite likely far enough to keep the set from working. Tacking the parts in with shorter leads might make the set sort of work.
The high voltages will not keep the set from working. The worry is that the high voltages will stress some of the tubes. But the stress won't be enough to consider this an urgent problem.
I can see that it will be hard to replace those caps correctly. The old ones look like a form of ceramic caps. Ceramic caps almost never fail, so this failure is very surprising. But almost never is not never.
If there is corrosion, could the corrosion itself be what is causing the short?

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 6:11 am 
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Tom Schulz wrote:
The clip leads are going to act as both capacitors and coils. So the tuned circuits are going to be tuned very far from the correct frequencies. Quite likely far enough to keep the set from working. Tacking the parts in with shorter leads might make the set sort of work.
The high voltages will not keep the set from working. The worry is that the high voltages will stress some of the tubes. But the stress won't be enough to consider this an urgent problem.
I can see that it will be hard to replace those caps correctly. The old ones look like a form of ceramic caps. Ceramic caps almost never fail, so this failure is very surprising. But almost never is not never.
If there is corrosion, could the corrosion itself be what is causing the short?


Think it would work to solder the 5pf cap directly across pins 6 and 8 of V3, so that it's between the base of the tube and top side of socket? Only problem may be getting the tubes pins to reach far enough into it's socket with the added thickness.


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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 6:33 am 
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Kevin Kuehn wrote:
Frequenceme wrote:
Here is a pic that shows the offending cap. I cant get to the bottom end to cut it of so far with the tools I have on hand.


Very good. Have you verified your voltages are now closer to correct on pins of V3A?

It would be interesting to see if you're getting a change in automatic gain control voltage corresponding with signal input to the set. To determine that you could measure dc volts at pin 1(grid) of V4(1st IF). You should see the voltage change when your rotate the contrast control through it's range, and even more change when you disconnect your signal from the sets antenna input. If you have that change in voltage when disconnecting the signal from the antenna input, it's then safe to assume you're getting signal though the video IF stages and it's being detected by V7A (video detector).


V3A pin 6 is 95v Pin 7 is -3.6 pin 8 is 0.

V4 pin 1 Contrast control full CW, -1.42v full CCW,-1.70v Signal disconnected while still at full CCW position, -1.60v

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 6:46 am 
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Tom Schulz wrote:
The clip leads are going to act as both capacitors and coils. So the tuned circuits are going to be tuned very far from the correct frequencies. Quite likely far enough to keep the set from working. Tacking the parts in with shorter leads might make the set sort of work.
The high voltages will not keep the set from working. The worry is that the high voltages will stress some of the tubes. But the stress won't be enough to consider this an urgent problem.
I can see that it will be hard to replace those caps correctly. The old ones look like a form of ceramic caps. Ceramic caps almost never fail, so this failure is very surprising. But almost never is not never.
If there is corrosion, could the corrosion itself be what is causing the short?


I figured from what I have learned here that my clip leads were sure to mess with wire dress. Didn't want to get into the tuner area but its clear now it was needed.

I have lots of resistors and already added 15 ohms that brought the voltages close to normal with the 150v line a bit low. It always is compared to the other two B+ lines. Could that mean I have another shorted component on that line?

Thanks for the tip on keeping the leads short. I will do my best. There sure isn't much room considering I haven't taken the tuner out. As far as corrosion goes it does look like the lead to B- on C217 may have corrosion. Don't see how that would cause a short to B-. Corrosion might have migrated into the cap and caused a short?

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 6:56 am 
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Frequenceme wrote:
Kevin Kuehn wrote:
Frequenceme wrote:
Here is a pic that shows the offending cap. I cant get to the bottom end to cut it of so far with the tools I have on hand.


Very good. Have you verified your voltages are now closer to correct on pins of V3A?

It would be interesting to see if you're getting a change in automatic gain control voltage corresponding with signal input to the set. To determine that you could measure dc volts at pin 1(grid) of V4(1st IF). You should see the voltage change when your rotate the contrast control through it's range, and even more change when you disconnect your signal from the sets antenna input. If you have that change in voltage when disconnecting the signal from the antenna input, it's then safe to assume you're getting signal though the video IF stages and it's being detected by V7A (video detector).


V3A pin 6 is 95v Pin 7 is -3.6 pin 8 is 0.

V4 pin 1 Contrast control full CW, -1.42v full CCW,-1.70v Signal disconnected while still at full CCW position, -1.60v


Hmm. Time will tell but I'm afraid your tuner has another problem in front of V3. V3A grid (pin 7) really hasn't changed much since your last measurement, in fact it's .4v more negative than before, and those AGC voltages seem very low and not really much change between signal levels. I also looked back at your tube voltage measurements and notice the grid bias on both V1 and V2 also seem off. Need to think some more about this. Wish I had a working set here with this same tuner, but no such luck. But regardless your 5pf cap needs to be replaced.


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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 7:27 am 
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Ok thank you, at this rate I am going to end up being a tuner guy and don't even have the equipment and knowledge to realign an AM radio correctly. I need to remeasure all the tube volts and see what I have. If I can get the 5 pf in with short leads first would that be more accurate? Kinda need to get it back in so I can put the domino back over it right.

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 8:31 am 
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Yes I agree the first line of business is to get the 5pf cap installed with short leads. In the mean while I will keep pondering this circuit and hopefully others will chime in.

Oh, was also meaning to ask, do you see any change in the snow or retrace lines, anything that changes at all on the CRT when rotating the contrast control throughout it's range, or changing channels or fine tuning? You mentioned that the last time you had a picture the fine tuning needed to be at one extreme, and next thing your picture vanished. So I'm still thinking something else is wrong in the tuner. But any indication of change in the noise on the CRT could indicate an ever so faint signal is still getting through.


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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 6:12 pm 
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I am just wondering if you could crush the old caps in order to remove them. That would leave their leads in place but the body would be gone. Perhaps there would now be enough room to put the new caps in mostly the correct location.

With the new caps in mostly the correct location the tuner would work well enough to get a picture if nothing else is wrong. You would then see if the picture looks good enough as is.

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 7:13 pm 
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I ended up using a small file to carefully cut most of the way through the last lead of C217. Had to be sure I was missing the coils fine wire near by. I did leave the old lead ends to tie too in several places. No room to work in there to try to get to pin 6 on V3A C214 got replaced as well and the domino put back over it all.
Attachment:
GE806-45.jpg
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Attachment:
GE806-46.jpg
GE806-46.jpg [ 168.57 KiB | Viewed 76 times ]


The contrast control has never had much effect on this set, it apears to still be about the same. The fine tuning however does change things, here are pics of it in three different positions. Audio by the way is good still maybe better now that C214 is not shorted.
Edit: The sound is different I now have sound in all positions of the fine tuner, before I did not.
Attachment:
GE806-47.jpg
GE806-47.jpg [ 122.37 KiB | Viewed 76 times ]

Attachment:
GE806-48.jpg
GE806-48.jpg [ 109.44 KiB | Viewed 76 times ]

Attachment:
GE806-49.jpg
GE806-49.jpg [ 114.46 KiB | Viewed 76 times ]

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Last edited by Frequenceme on Nov Sat 10, 2018 8:06 pm, edited 1 time in total.

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 7:28 pm 
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I have always wondered if the fine tuner is right. Looking closer I notice it has corrosion. I have not used any thing to clean it, is Deoxit ok?.
Attachment:
GE806-50.jpg
GE806-50.jpg [ 143.2 KiB | Viewed 74 times ]

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 8:04 pm 
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Well for some reason I'd assumed you had no audio either. If you have audio you know your tuner is working as well as the sound is being picked off after the video detector. So basically things are working up to that point. Does the fine tuner tune the audio as it should? The fine tuning is a variable cap, so I doubt corrosion is keeping it from working entirely.


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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 8:10 pm 
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Kevin Kuehn wrote:
Well for some reason I'd assumed you had no audio either. If you have audio you know your tuner is working as well as the sound is being picked off after the video detector. So basically things are working up to that point. Does the fine tuner tune the audio as it should? The fine tuning is a variable cap, so I doubt corrosion is keeping it from working entirely.

Before I only had sound if I tuned it in with the fine tuner. Now I have sound throughout all the traveler of the fine tuner.

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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 8:17 pm 
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Have you tried reception on an adjacent channel? It's easy enough to forget what channel the tuner is on when you have a bare chassis on the bench. The sound is actually picked off after the second video amp, so you have some sort of signal getting to at least that point. If you haven't already, ohm out L258 to make sure it's not open. In fact it would not be a bad idea to check all the coils after the detector(V7A).


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 Post subject: Re: GE806 1949 with stand
PostPosted: Nov Sat 10, 2018 8:51 pm 
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Looks like L258 fell victim to the mouse that was in the set. Also L260 is open. I wasn't sure how to test them but it looks like they are such low resistance that you can ohm them while in circuit. I have some new and used coils from the dumpster dive, do these have to be real exact?
Attachment:
GE806-51.jpg
GE806-51.jpg [ 190.64 KiB | Viewed 64 times ]

Looks like L260 might have gotten hot. Maybe the old 10 uf was shorted?
Attachment:
GE806-52.jpg
GE806-52.jpg [ 192.31 KiB | Viewed 64 times ]


Thank you again for the help.

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