All, I am going to replace the rectifier in this.. However The schematic seems wrong.. On a normal rectifier the Anode is Plus But on schematic it has the Cathode Plus.. I seem to recall that these schematics were wrong ..
They had not decided which way at that time if it was hole flow or electron flow. The schematic is correct but the picture on the selenium rectifier is wrong.
+1 Anode is connected to the AC and the cathode is the DC output.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 01-01-2019, 03:27 PM by Radioroslyn.)
For some it may be worth the effort if your into construction and Kit building.
^^^^ I don't know how that got written into my reply but its like my mind was read aloud ...
A I have one of the Heath-kit models, it is a bit shabby, paint loss and minor dial damage... Its a lot smaller (transistorized) than the Millen's I have.
Well, instructions for assembly are the only ones there are so give it a whirl on a snowy winter weekend...
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Hello everyone, It's really an odd coincidence I found this thread just as I'm having some trouble in re-building one of these.
For such a simple circuit, I shouldn't be having any trouble but, it seems I am.
My plan was to change the electrolytic and selinium rectifier in my GD-1B.
On the way, I installed a grounded power cord and did some corrections to the original wiring.
So, I've spent quite a bit of time trying various schemes (I was going to try re-stuffing the original cap, but abandoned that idea.)
and figuring out ways to mount the new components.
So, here I am, everything complete, I've double, triple, quadruple checked all my wiring, tested all resistors, and everything looks great, but.....
My measured voltages are way too high!
I'm taking measurements with the variac at 50 VAC, which goes through the transformer, rectifier, supply caps.
On the schematic, it shows the output from the supply caps to be 95 VDC, then passing through a 6800 ohm resistor to arrive at pin 1 of the tube with 45-52 VDC.
So even though I'm not applying full voltage (50 VAC), my pin 1 voltage is 60 VDC and follows any change I make in line voltage.
I considered that I'm using a silicon diode to replace the selinium rectifier, but there is a 1K resistor between the 20 Mfd caps and adding another 100 ohm resistor seems like a drop in the bucket when the tolerance of that 1 K resistor is considered.
I've been measuring and inspecting everything I can think of and can detect no shorts or parallel circuit paths to explain the lack of a voltage drop across the 6800 ohm resistor, which I measure at 7100 ohms.
I'll try taking a few pics tomorrow,
If anyone has any ideas about what I could check, I'm all ears.
Thanks,
Robert
If you are applying less than half the voltage to the primary of the transformer then the heater voltage on the tube is going to be very low. This causes the tube not to draw much plate current thus very little load across the hv.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
