Advice on type of capacitors for the power section of this Osciloscope.

Thread Starter

kwric

Joined Oct 9, 2021
6
Looking for some advice on the best capacitors to use in power section of this oscilloscope circuit.
Some Background
I purchased what I thought was a 1952 Cosser 1035 scope only to find it had been gutted and completely rebuilt with a customised circuit. I’m slowly drawing a schematic from scratch in able to analyse the circuit before restoration.
My question
The top transformer has 5 large PIO capacitors (Top RH of circuit marked numbers 1 to 5) one of which is leaking oil badly. I am aware of the toxic nature of these and about safe disposal. There are also 2 large cylindrical caps, also possibly PIO that failed testing so they will need to be replaced. (0.1uF 3000vdc).
Not being familiar with this rather complicated power circuit some advice on suitable replacement types for these capacitors would be apreciated.
Kevin1E364DA6-8ABA-4419-8B2F-DE7137D581A5.jpeg5ABD8E86-086D-4327-AE53-C0AECF1F7F17.jpeg
 

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LowQCab

Joined Nov 6, 2012
2,635
Single-Capacitors, to replace the ones shown, are extremely expensive.

Get some Perf-Board, and some various Plastic-Boxes.
Then buy ~100 of these ........... ( ~$75.oo )
https://www.digikey.com/en/products/detail/tdk-corporation/FG20C0G2W223JNT06/5802903

Arrange the Capacitors in Series to meet, or exceed, the Voltage-Requirements,
then create parallel groups until You meet or exceed the Capacitance-requirements.

Voltage-Divider-Resistors are a good idea to force
equal-Voltages across the Series-connected-Capacitors,
but without having a Schematic-Diagram,
I couldn't even start to guess at the appropriate values.
.
.
.
 

Thread Starter

kwric

Joined Oct 9, 2021
6
but without having a Schematic-Diagram,
I couldn't even start to guess at the appropriate values.
..
Thanks, I did attach a pdf file with a schematic, the capacitors are in the top transformer circuit. The large POI square capacitors are 0.25uF and 0.5uF. The cylindrical ones are 0.1uF.
 

LowQCab

Joined Nov 6, 2012
2,635
Looks like you've got at least ~15 High-Voltage-Capacitors to replace.
You must really have a deep attachment to that old 'Scope.

For the money You will wind-up spending restoring this "vintage" 'Scope,
You could have a very nice and modern, Multi-Channel-Pico-Scope,
running on a used LapTop-Computer from your local Computer-Shop,
and a huge Flat-Screen-TV on the wall for a Monitor.

And,
it doesn't weigh ~95-pounds,
doesn't burn ~300-Watts of power just idling,
it will easily fit in a Briefcase,
has huge amounts of Memory,
and, displays as many Traces as You think you'll need.
.
.
.
 

Thread Starter

kwric

Joined Oct 9, 2021
6
Looks like you've got at least ~15 High-Voltage-Capacitors to replace.
You must really have a deep attachment to that old 'Scope.

For the money You will wind-up spending restoring this "vintage" 'Scope,
You could have a very nice and modern, Multi-Channel-Pico-Scope,
running on a used LapTop-Computer from your local Computer-Shop,
and a huge Flat-Screen-TV on the wall for a Monitor.

And,
it doesn't weigh ~95-pounds,
doesn't burn ~300-Watts of power just idling,
it will easily fit in a Briefcase,
has huge amounts of Memory,
and, displays as many Traces as You think you'll need.
.
.
.
We all have hobbies, I already have a modern digital scope. I restore vintage radios and test equipment because I enjoy it. Seems I’m on the wrong forum, was hoping someone would suggest a suitable film cap that I could use that would suit a high voltage power circuit like this.
 

MrChips

Joined Oct 2, 2009
27,679
We all have hobbies, I already have a modern digital scope. I restore vintage radios and test equipment because I enjoy it. Seems I’m on the wrong forum, was hoping someone would suggest a suitable film cap that I could use that would suit a high voltage power circuit like this.
You are not in the wrong forum. The previous member was just making a personal statement. Take it with a grain of salt.

Your challenge will be finding such high voltage capacitors in a suitable package and affordable price.
I too am working on a high voltage circuit that requires 0.1μF @ 1000V or higher. They are not easy to come by.
 

Thread Starter

kwric

Joined Oct 9, 2021
6
You are not in the wrong forum. The previous member was just making a personal statement. Take it with a grain of salt.

Your challenge will be finding such high voltage capacitors in a suitable package and affordable price.
I too am working on a high voltage circuit that requires 0.1μF @ 1000V or higher. They are not easy to come by.
I have seen some high voltage film capacitors such as these.
https://au.mouser.com/ProductDetail/Cornell-Dubilier-CDE/940C30P1K-F?qs=KAyk88b/VhftwmIcukzsyg==
What I was hoping for was advice as to whether film caps like these can replace the PIO caps in a high voltage power circuit like the one I posted.D2B623E1-DBF4-4812-BEBA-2D66A16E5AFA.jpeg
 
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