Re: Type 503 Oscilloscope Issues


Hello all,

I feel bad that it has been several days since my last posting. Unfortunately, my work is at a standstill right now. Over the past weekend I had focused most of my work on restoring a vintage volt meter (Triplett 630-A), which is now working (and supports up to 6000 V, although I lack the HV leads, so no -3000 V testing yet). As such, I only now have gotten time to focus on the scope.

However, when I connected the leads to the ground (chassis) and -100 V test point, plugged in the scope, and after the brief burning smell, nothing happened (no lights for the scope, no CRT turning on, no tubes activating). I discovered that the fuse had blown during my attempt to get the voltages, but after no luck in going through my fuse stock, I ended up having to order a set of new ones to come in, so that won't be until next week earliest.

For the scope, I was still able to check the non-voltage components on the power circuit. The diodes still check out, with D652 (and others) giving readings of ~0.65-0.65 on my multimeter. However, only diode D672 gave a reading of 0.041 on two different multimeters, so I suspect this one is bad. This one is connected to the +12.6 V circuit.

As for resistors, some also seem to have issues, with R692 (going to V692) being at 1.4-1.5 ohm, but it is supposed to be 4.3 ohm. I admit I am having a bit of difficulty in locating R659, so I was unable to confirm if that one is okay.

Once the fuses come in, I'll let you know how the voltages read out. However, as for the burning, think it may be coming from the wires leading to the T601 (see the photo:

- Evan

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