My 630

[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