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  #61  
Old 12-31-2018, 08:13 PM
ZenithNut ZenithNut is offline
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Heres the power supply Tom.

I was wondering if it was necessary to have the tubes populated to load it down for accurate B+ checks. I had the chassis pulled with tubes populated and it was whinning so I pulled all the tubes to check b+ out of cabinet. I didnt know the fly was apart of that set up.

When I disconnect the screen should I repopulate the horinontal tubes or..?
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  #62  
Old 01-01-2019, 12:26 AM
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My slightly annebriated new years troubleshooting advice:

You are right, some of your B+ voltages are well outside of tolerance, however those rails are derrived from other rails that are also not dead on spec (and things may not be loaded correctly) which may give GIGO data.

No tubes should be pulled with the H out screen and plate (the top lead connection) disconnected. The fly will not (or at least should not) be loading the B+ in this state. The flyback typically only loads the highest B+ rail (through the damper)...So if it is driving you nuts that all your B+ rails are high and you have a variac you can cheat your way to normalizing your B+....To do this connect a DMM to the 405V rail on your schematic and dial your variac till that rail reads 405V then you can accurately access how screwed up your lower voltage B+ rails and circuit voltages are*. This is probably the ideal state to do what you should focus on: Getting the H osc on frequency with test instruments, getting the osc amplitude and waveform up to spec and most importantly getting that signal delivered to the H output grid and developing negative H output grid voltage within 10% deviation of spec. Only when you have a decent approximation of correct H output grid voltage will it be safe to reconnect the H out plate and screen (that is a $25+ output tube so I don't advise running it outside of specs). When you have good H out grid drive you should be able to put the circuit back to stock connection and then have HV, horizontal sweep, and other working-set-like goodness (though shorts on the fly side could hamper much of that if present).

If the osc is not behaving and is powered by a lower B+ rail that is way out of spec even with variac normalization of the high B+, then what you should do is trouble shoot everything on that lower rail and try to get that rail properly loaded by working circuits.

*This may lower your heaters and make marginal tubes show their uglier sides.
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  #63  
Old 01-01-2019, 02:06 PM
ZenithNut ZenithNut is offline
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Quote:
Originally Posted by Electronic M View Post
My slightly annebriated new years troubleshooting advice:

You are right, some of your B+ voltages are well outside of tolerance, however those rails are derrived from other rails that are also not dead on spec (and things may not be loaded correctly) which may give GIGO data.

No tubes should be pulled with the H out screen and plate (the top lead connection) disconnected. The fly will not (or at least should not) be loading the B+ in this state. The flyback typically only loads the highest B+ rail (through the damper)...So if it is driving you nuts that all your B+ rails are high and you have a variac you can cheat your way to normalizing your B+....To do this connect a DMM to the 405V rail on your schematic and dial your variac till that rail reads 405V then you can accurately access how screwed up your lower voltage B+ rails and circuit voltages are*. This is probably the ideal state to do what you should focus on: Getting the H osc on frequency with test instruments, getting the osc amplitude and waveform up to spec and most importantly getting that signal delivered to the H output grid and developing negative H output grid voltage within 10% deviation of spec. Only when you have a decent approximation of correct H output grid voltage will it be safe to reconnect the H out plate and screen (that is a $25+ output tube so I don't advise running it outside of specs). When you have good H out grid drive you should be able to put the circuit back to stock connection and then have HV, horizontal sweep, and other working-set-like goodness (though shorts on the fly side could hamper much of that if present).

If the osc is not behaving and is powered by a lower B+ rail that is way out of spec even with variac normalization of the high B+, then what you should do is trouble shoot everything on that lower rail and try to get that rail properly loaded by working circuits.

*This may lower your heaters and make marginal tubes show their uglier sides.
I have the screen disconnected. So now I am going to populate the tubes, connect it all to the yoke etc. Then check my voltages with everything except the h output tube.

With no tubes as of now, I have 50 volts positive at the grid of the h osc. Instead of swinging negative it goes up to 80 v positive at pin 2-6 of the h output. I will plug the tubes in and all that and check again. Hopefully the tubes will load down the B+. Theres a hor waveform coil that is connected to the cathode of the h osc with a .01 cap in parallel with then it goes to ground.
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  #64  
Old 03-12-2019, 08:01 PM
ZenithNut ZenithNut is offline
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Alright,

So the reason the B+ was out of whack was from a 600 ohm 18 watt power resistor shorting internally. So instead of dropping 400v down to 350, it stayed 400.

With this corrected, I still have no sound or video. Grid 1 of the horz output is 55 volts positive.
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  #65  
Old 03-12-2019, 08:59 PM
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Quote:
Originally Posted by ZenithNut View Post
Alright,

So the reason the B+ was out of whack was from a 600 ohm 18 watt power resistor shorting internally. So instead of dropping 400v down to 350, it stayed 400.

With this corrected, I still have no sound or video. Grid 1 of the horz output is 55 volts positive.
Probably time to turn your focus back to the horiz osc.
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