My 630

[Geist]

Hi All;
Old Coot, Yes, it is the same Schematic.. I cannot take that Cap apart, again it would destroy it.. But, I can unwire that one from ground and install an external Cap.. All three Caps in that Can are wired with common Negative connection..
THANK YOU Marty

[Geist]

Hi All;
All I have at present is one Electrolytic Cap that is 350 Volt at 10 MFD.. It calls for a 150 Volt at 80 MFD.. I could try the 10 MFD just to see If it makes any difference.. While disconnecting the one in the Can.. I am going to look at the old Can and see IF it has that one cap internally wired Backward in reference to the others..
THANK YOU Marty

[Geist]

Hi All;
Old Coot, I just looked at the Can and it has (as near as I can tell) the negative as the common point.. I also, Just looked at the Sams and It also shows that the + (positive) side of that cap going to Ground..
On another Cap the (C225) on the Riders, When C225A is connected to Cap C221B, then the voltage goes LOW, about 45 volts at 120 volt input to the transformer, But when C225 is not connected to C221B, the the Voltage is about 230 volts, still slightly low, by 70 Volts, but that could just be my Rectifier, since they are all old Tubes.. So when C225 is connected either what is connected on the other side of it or the other Cap, Is pulling things down.. I have yet to disconnect the rest of the wires from C225 to see IF it has any affect on the Voltage Dropping..
THANK YOU Marty

[old_coot88]

Originally Posted by Geist

..Yes, it is the same Schematic.. I cannot take that Cap apart, again it would destroy it.. But, I can unwire that one from ground and install an external Cap.. All three Caps in that Can are wired with common Negative connection..

If all three are wired with common negative, that would be correct. AND the common negative should be 'floating' above ground since it is the negative supply rail (or buss). It is floating and not shorted to ground, isn't it? Looks like it should show around 500-600 ohms to ground, with a bit of variation when you turn the focus control.

I just looked at the Can and it has (as near as I can tell) the negative as the common point.. I also, Just looked at the Sams and It also shows that the + (positive) side of that cap going to Ground..

Good. Then Sams has it correct.

On another Cap the (C225) on the Riders, When C225A is connected to Cap C221B, then the voltage goes LOW, about 45 volts at 120 volt input to the transformer, But when C225 is not connected to C221B, the the Voltage is about 230 volts, still slightly low, by 70 Volts, but that could just be my Rectifier, since they are all old Tubes.. So when C225 is connected either what is connected on the other side of it or the other Cap, Is pulling things down.. I have yet to disconnect the rest of the wires from C225 to see IF it has any affect on the Voltage Dropping..

Have you checked the Horz centering and Vert centering controls? Both should be 20 ohms according to the schematic. An open element in either one could really screw things up since they're both in series in the B+ chain feeding out to the 275V buss.

Um.. You are taking your voltage reading at the 275V source, right?

And another thought.. is the center tap of the power xfmr's HV winding connected to the common-negative 100V buss? In re-reading your thread, you mentioned some strangely low B+ readings coming out of the 5U4s. An unconnected or mis-connected center tap could do this.

[Geist]

Hi all;
Old Coot, I guess I am a little mixed up from your previous postings.. I take it that my Cap is OK, and NOT wired Backwards.. From what you have last written..
At present when I am measuring my voltages I have been measuring from Pin 8 of the 5U4 and not from the 275 Volt tap at present.. My DMM is attached to Chassis Ground on one side and pin 8 on the other side.. Since it is connected to something that is causing it to show a low value..
You, may be right in that it could be either Centering pot..
Tomorrow I plan on unhooking all the connections to the negative side and the other cap positive side, to see if the problem still exists, these seem to be the connections to the Centering pots.. Then connecting the other wires on till I find the Culprit that is bringing the whole system down.. This is before it even gets to the 275 Volt tap and so it still could be something that the Tap is tied to and not the centering pots.. So, I have alot of places to check..
And, Yes, the Center tap on the Transformer is connected to C221 Common can side, which is above and Isolated from ground..

[old_coot88]

Originally Posted by Geist

...I take it that my Cap is OK, and NOT wired Backwards..

Yes, as long as C220C, the negative supply filter, has its positive end to ground, it is correct.

... At present when I am measuring my voltages I have been measuring from Pin 8 of the 5U4 and not from the 275 Volt tap at present.. My DMM is attached to Chassis Ground on one side and pin 8 on the other side..

This is with nothing else (except the filament) connected to pin 8, right?
As mentioned earlier, the meter has to see pure, filtered DC in order to get an accurate reading of the B+ coming out of the 5U4. You mentioned having a 10mf/350V cap available. Did you try jumpering it between pin 8 and ground? This would allow the meter to give a pure, no-load DC reading.

..And, Yes, the Center tap on the Transformer is connected to C221 Common can side, which is above and Isolated from ground..

Good. And what is the resistance from that point to ground? It should be the additive resistances of the focus coil, ion trap coil, and bleeder string R185a, R186a, and R186b. It looks like around 500 - 600 ohms. And it should vary slightly with turning the focus control. Does it?

As far as the V and H centering pots, it should take only a few seconds to check 'em with with an ohmeter (on the RX1 scale).

But the very first thing is to establish how much juice is coming out of the 5U4 pin 8.

[Geist]

Hi All;
Old Coot, The Cap C220C is wired Correctly, Thank You for the clearification..
I have (for now) a wire connected to the 5U4 Pin 8 which goes to the meter.. Pin 8 is also connected to C221A, C220A, C220C, as well as the field coil, which connects to C221B at present and with one rectifier tube in gives a voltage of 230 Volts.. I had at first nothing connected to the 5U4, but right after checking that I connected back C221A and after working my way thru the field coil connections It also was then connected, along with the related caps.. So I didn't connect in the 10MFD 350 volt cap, since I had the others in.. I had only suggested it as a sub for C220C if it was backwards, which it is not..
At present the Centering pots and the focus coil are not connected to it.. I have not measured the Resistance in them, yet, But I can do that after I finish this posting..
I have been trying to work my way thru each wire and each section one at a time.. I have at present as stated above 230 Volts and that is without the focus coil and the Resistor dividers and the Centering pots..
I next want to put in C222A and make sure it is OK, I also will put in the Second Rectifier tube to see if the Initial voltage coming out of the Tubes will increase with the addition of the second tube.. And then I can see what I can do with C225A and C225B..
THANK YOU Marty

[Geist]

Hi All;
Old Coot, With the second Rectifier plugged in the Voltage dropped to 200 Volts on pin 8.. And the Bulb lit up.. I took out the Bulb and left the rest the same, it now reads 270 Volts at pin 8.. Which is close to the 300 volts specified, for that pin..
So now my Question, Should I leave out the Bulb or for safety sake keep it in for the present while I am testing ???
THANK YOU Marty

[old_coot88]

Originally Posted by Geist

...I have been trying to work my way thru each wire and each section one at a time.. I have at present as stated above 230 Volts and that is without the focus coil and the Resistor dividers and the Centering pots..

???Are you saying the focus coil and resistors R185a, R186a, R186b are not in-circuit? If so, then there is no path to ground for the center tap of the power xfmr. The CT has to have a path to ground before the 5U4 can supply the correct B+ voltage. Or is the focus coil simply unplugged, leaving R182, R183, and the focus control still in-circuit?

Again, what is the resistance between the power xfmr CT and ground?

...With the second Rectifier plugged in the Voltage dropped to 200 Volts on pin 8.. And the Bulb lit up.. I took out the Bulb and left the rest the same, it now reads 270 Volts at pin 8.. Which is close to the 300 volts specified, for that pin..

Probably the filament load of the second 5U4 lugged the primary down, lighting the Bulb and dropping the secondary voltages.

So now my Question, Should I leave out the Bulb or for safety sake keep it in for the present while I am testing ???

For now, leave the Bulb in, stay with a single 5U4 until you find out the resistance between the power xfmr CT and ground.

Once you verify the CT has the proper path to ground, stick both 5U4s in and get rid of the Bulb, and bring the primary up slowly toward full line voltage while monitoring the B+ at pin 8 (being sure not to exceed voltage rating of the new filters).

[Geist]

Hi All;
Old Coot, again you are right, I have NO resistance from the Center tap of the transformer to ground.. I didn't notice their relationship, while taking things out.. I am in the process of measuring these for a resistance value.. Both the Horizontal and Vertical Pots measure about 20 ohms and the wipers work in both of them.. Then I will connect the ion coil and the focus coil and let you know what changes..
THANK YOU marty

[Geist]

Hi All;
Good News, I measured the Ion Trap Coil with the 56 ohm resistor accross it and got 22.9 ohms, just like Bob did.. The Focus coil measures about 240 ohms.. And After connecting that part of the circuit up.. I GOT on pin 8 of the Rectifier 330 Volts with the Variac set at 60 Volts, I didn't dare take it up any further..
Now to connect the 275 Volt voltage divider circuit and see what happens..
THANK YOU Marty

[old_coot88]

Say hey! Good goin' amigo.

[Geist]

Hi All;
More good news, I hooked up the 275 Volt lead, and at pin 8 of the rectifier, I get 302 Volts, with the Variac set at 115 volts and the Bulb lit anyway.. With one rectifier tube.. Special Thanks to Old Coot.. Now for another wire the one going to C223A..
THANK YOU Marty

[old_coot88]

Geister,
It might help to simplify what's going on in that circuit. It uses what's called a 'back bias' scheme to generate negative voiltages for various other circuits in the chassis. It's used extensively in '30s radios with power trannys and in a lot of early TVs.

First visualize the CT of the HV winding going directly to ground, and the rectifier tube putting out full B+. Now visualize a resistor from the CT to ground. As the rest of the tubes pull current, a voltage is developed across that resistor, and it's negative with respect to ground. The resistor can then be tapped (or a daisy chain of resistors used) to obtain specific negative voltges.

[Geist]

Hi All;
I got all the wires hooked up.. And it didn't drag anything down, which is the good news.. With one Rectifier tube and the 40 watt light bulb in series after the Variac.. Here is what my readings show, the bulb is dimly light..
105 volts on the Variac
Rectifier pin 8 307 volts, shows on schematic +300 volts
275+ divider tap 238 volts
135+ divider tap 185 volts
-100 on cap -13 volts
-18 on divider tap -5 volts
-2 0n divider tap -.5 volt

THANK YOU Marty