Pulse Pendulum Projects

[TinselKoala]

It looks like the HV supply is gone. I get about 6+ volts instead of 1385+/-69.5volts at the back of the CRT socket.
I figured my meter would at least 'peg' to the 1. (overload) if there was HV there but there wasn't...
Looks like you were right about the power light TK.
Now how much is it worth my trouble to hunt down the ass end of a 422?
I definitely need more coffee for this type of thing...

Peace,
PC

Fortunately the HV supply is ridiculously simple in the 422, basically consisting of a Cockroft-Walton voltage multiplier and some regulator components. The first thing I'd check, after the connector P701 and the transformer T801 is the 51 volt Zener diode D839. Just a hunch. Do a good visual check of the HV multiplier board and the HV regulator board with a magnifying glass, you may be able to see a burned component visually. Check the connections and contacts at the Centronix-type connector P701 (has the inputs to the primary of the HV supply's transformer),  and check the voltage outputs from the HV transformer T801, you'll want to unsolder the secondary output terminals 7,8,9, 10 to isolate the transformer from the voltage multiplier and filament supply to see if the transformer is putting out anything for the CW bank to multiply. If it is, then check that Zener, and the 10 diodes in the CW bank, and the electrolytic caps C829 and C849, etc.  Schematic on page 181 of the pdf manual. If the transformer is shot you are probably "s.o.l." as they say but if it's good you can probably fix the problem easily enough. Be careful poking around in there, even the CRT filament which is a low-voltage filament, is elevated by the supply to a high (negative) voltage to aid in creating the beam.
To avoid ruining your meter you can connect the scope's AC line cord to a Variac and check the behaviour of the HV system at low input voltages, you should at least be able to tell if it is working before it exceeds the range of the meter that way.

My old Tek RM503 had a fault in the HV system that caused it to blow fuses (by the way, check to see if the line fuse is the correct value and _don't_ sub with a higher current value than specified). The filament supply in the big mains transformer was internally leaking the elevated HV in the 6 volt filament circuit. The HV supply was good but because of this leak in the mains transformer it was drooping severely and also blowing the line fuse. I finally fixed it by installing a completely separate 12-volt center-tapped RadioShack transformer for the filament circuit so the HV had nowhere to leak to; the scope is 100 percent functional now. The hard part, once I figured out the problem, was finding room physically for the "extra" transformer inside the case.
In your case the filament supply comes from the HV transformer itself, a low voltage winding, which is then elevated by a section of the C-W bank. You may actually have the same problem I had and might be able to fix it in a similar manner. Since fil. supply is not from the mains transformer maybe you aren't blowing the line fuse like I was. The way to check this would be to disconnect the filament LV supply at the T801 terminals 9 and 10 and then re-test for HV at the test point. If the HV comes up, with the filament supply disconnected from the T801, then you may be able to fix it by the same method I used. Although the diode FWB D849 should probably isolate the filament windings from the HV... but you never know.
Just thinking semi-randomly...

Right, more coffee.

[TinselKoala]

Hello PC,

you may find this here interesting. This guy is serious and has a lot of experience. He has only posted
a few experiments but the quality is excellent

https://www.youtube.com/watch?v=Tm1LmkmYkjQ&list=UUVZmmMOhzhWEUamhGLPSTFQ

Regards

Kator01

LOL! I am afraid I strongly disagree with you! Do you define "overunity" as voltage amplification?

Voltage multiplication is not _energy_ multiplication. There is no "overunity" being demonstrated in that system. But certainly there are the required number of colored clipleads! A small oscillating input voltage is driving the pendulum, and as the coil swings through the strong magnetic field of the magnets a higher-voltage, very brief pulse is generated which flashes the LEDs. The system is a stripped down version of the perpendupetulum, without the "self looping" aspect where the higher-voltage pulse is triggering the drive pulse. He could add the loop by connecting the LED output to the trigger input of the FG with some tiny phase delay, so that the drive pulse from the FG to the coil happened just after the output pulse from the coil to the LEDs/FG.

But what is "overunity" about that? The PerPenduPetulum does essentially the same thing; the higher voltage pulse from the magnet passage is triggering the transistor which discharges the capacitor to produce the drive pulse in the coil, instead of lighting up some LEDs outside the drive system.

An experienced and serious researcher would never be claiming OU from such a system without a lot more solid evidence than he is presenting. And of course such evidence won't be coming, since there isn't any OU there.

[PhiChaser]

@TK I will take it out again and take a peek. It looks pretty straightforward (referring to the PDF), I just wish I had a better soldering iron...
Time for a real disassembly.
I will look for what you suggested.
Thanks again for the help!
The worst that could happen is I don't fix it right?

PC

@Kator Yeah, I saw that one. Not OU, sorry buddy, gonna have to go with TK on that one...

[PhiChaser]

Still looking...

[TinselKoala]

Ah, beauty! I love that particular era of circuit board layout. Double sided but with room enough to work. That's the HV regulator board, with the filament supply FWB is the black thing on the top right, and the associated electrolytic cap C849 is the 150 uF, 15 volt unit right there in the top center.  When you unsolder stuff from those boards, then you can heat up the pads and use a wooden toothpick to "clean" or rather open up the holes without damaging the pads on either side of the board after gently pulling the component lead out of the hole. There isn't much that can go wrong on that particular board except the Zener and the electrolytic cap and possibly the FWB. The Zener D839 is given in the parts list and the schematic as a 51 volt zener but I can't make sense of the part number on that diode, a 51 volt zener is 1n3806 but that part number on the diode looks like  it could be 1n3789 which is a 10 volt zener. Weird.

What's the serial number of your scope, maybe there is a change with different s/n.

When the scope is together and powered up, does that neon in the middle glow at all?

If you can find the wire that connects from the Anode of the D839 zener over to the HV multiplier board itself, disconnect that wire from the regulator board and then test the wire (ie the bottom end of the CW bank) for HV. Again, I'd do this by connecting the mains AC line cord to a Variac and slowly bring up the supply voltage from zero, with the DMM connected to this wire from the HV multiplier board. If the basic HV supply is working (transformer and CW bank) you should see the voltage here come up (or rather down, since it is negative wrt the chassis ground.) If the voltage does come up with the HV regulator board disconnected like this then the fault is on the regulator board, which would be good. If the voltage doesn't come up, then the fault is probably in the basic HV supply, either the transformer or the diodes. I'd do this testing with the filament supply disconnected at the transformer, wires at both pins 9 and 10 unsoldered.

If you don't have a variac then you can try doing it with full power from the mains, but I'd suggest here disconnecting one side of the main fuse and putting an ammeter in series with the fuse and the circuit to see what the input current draw is and if it exceeds or even comes really close to the specified fuse rating, stop!
Or you could also try putting a 40 Watt or lower incandescent light bulb in series with the AC mains input to reduce the voltage supplied to the scope so that your DMM isn't stressed when you go to measure the HV. You won't hurt anything in the scope by supplying it with less voltage. A Variac is a very valuable tool and has many uses around the lab.