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465 Dead HV Multiplier?

 

My lovely 465 died immediately after I finished some cosmetic repairs. Low voltage test points all look good. No beam, except when I disconnect the ground lead of the HV multiplier as suggested by VintageTek Museum on youtube (). (I also hear some crackling sounds with the multiplier disconnected, so I haven't run it in this state for more than a few seconds.) Could the problem be anything else besides the multiplier? I have a digital scope but no high voltage probe. To measure high voltage DC I have been using a 10MOhm resistor and analog ammeter, but of course that's a significant load.

If the problem is the multiplier - part number 152-0552-00 - does anyone know if they're still available? I see that a couple members have built replacements, and I would really appreciate a schematic and/or component values. The location of the multiplier within the scope, and the requirement of potting, will make it difficult to troubleshoot a DIY replacement and I have little high voltage experience. So I'd like to get it in 1 shot.
 

One quick bit: Don't use that 10meg resistor (or any other ordinary resistor) again for HV measurement.?A typical voltage rating for a half-watt resistor is just a few hundred volts, above which HV will arc through/around it, effectively shorting it out. If you don't want to blow things up, you'll have to use a proper HV probe.

The multiplier hasn't been manufactured for many years, so you'll either have to find a used one somewhere (which itself could be defective), or make your own replacement.

Tom

On 4/22/2025 12:26 PM, gabrielkrell+tek via groups.io wrote:
My lovely 465 died immediately after I finished some cosmetic repairs. Low voltage test points all look good. No beam, except when I disconnect the ground lead of the HV multiplier as suggested by VintageTek Museum on youtube (). (I also hear some crackling sounds with the multiplier disconnected, so I haven't run it in this state for more than a few seconds.) Could the problem be anything else besides the multiplier? I have a digital scope but no high voltage probe. To measure high voltage DC I have been using a 10MOhm resistor and analog ammeter, but of course that's a significant load.

If the problem is the multiplier - part number 152-0552-00 - does anyone know if they're still available? I see that a couple members have built replacements, and I would really appreciate a schematic and/or component values. The location of the multiplier within the scope, and the requirement of potting, will make it difficult to troubleshoot a DIY replacement and I have little high voltage experience. So I'd like to get it in 1 shot.
 

You can use a ECG/NTE538

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/g/TekScopes/topic/475_dead_voltage_multiplier/7648063
 

One quick bit: Don't use that 10meg resistor (or any other ordinary
resistor) again for HV measurement. A typical voltage rating for a
half-watt resistor is just a few hundred volts, above which HV will arc
through/around it, effectively shorting it out. If you don't want to
blow things up, you'll have to use a proper HV probe.
Appreciate concern - I am actually using a high-voltage resistor rated for 10KV, which I happened to have available. It's a few inches long to prevent arcing. But the load is too high to measure anything that can't source a milliamp.

You can use a ECG/NTE538
Thanks. These are relatively cheap and available. I see the original Tek part had a series resistor at the end, was that just for technician safety?

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