Capacitor inside an olympus BHB microscope

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smollerthings
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Capacitor inside an olympus BHB microscope

#1 Post by smollerthings » Sat May 28, 2022 7:58 am

Hi All,

Does anyone know where I can find a replacement capacitor for this little guy who probably burned a decade ago. I could read "Marcom MP something 500 wv.dc something". Thanks! I think those are used to avoid sparks when turning on/off? Since nothing bad happened I presume this component is not indispensable?
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smollerthings
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Re: Capacitor inside an olympus BHB microscope

#2 Post by smollerthings » Sat May 28, 2022 11:51 am

Edit: Moved to a new thread
Last edited by smollerthings on Sun May 29, 2022 10:11 am, edited 2 times in total.

GerryR
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Re: Capacitor inside an olympus BHB microscope

#3 Post by GerryR » Sat May 28, 2022 11:55 am

500 WVDC is good to know, but you need to know the capacitance in uf (microfarads). Most items, if not specialized for a particular application can be purchased form, Allied Electronics, Newark Electronics, Digi-key, etc. The value in uf is important and can be gotten from a schematic, or from someone with the same scope, willing to open it up.

smollerthings
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Re: Capacitor inside an olympus BHB microscope

#4 Post by smollerthings » Sat May 28, 2022 1:04 pm

I think it is 0.1uF from the burnt plastic cover...

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Re: Capacitor inside an olympus BHB microscope

#5 Post by smollerthings » Sat May 28, 2022 1:08 pm

Found a guy with the same issue here:
https://www.electro-tech-online.com/thr ... pe.160112/

SWmicro
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Re: Capacitor inside an olympus BHB microscope

#6 Post by SWmicro » Sat May 28, 2022 1:12 pm

smollerthings wrote:
Sat May 28, 2022 7:58 am
I could read "Marcom MP something 500 wv.dc something". Thanks! I think those are used to avoid sparks
or filtering/interference suppression ?

Bruce Taylor (of this parish) had a very similar problem in 2013
https://www.photomacrography.net/forum/ ... 25&t=20285
and describes a Marcon cap in the 8th post down
" It says (under the Marcon logo): MP CAP .1uF (M) 500 WV.DC 20k "

good luck :)

smollerthings
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Re: Capacitor inside an olympus BHB microscope

#7 Post by smollerthings » Sat May 28, 2022 2:35 pm

SWmicro wrote:
Sat May 28, 2022 1:12 pm
Bruce Taylor (of this parish) had a very similar problem in 2013
Thanks. So the mystery remains. What is that for? I think that it is to avoid current discontinuity and sparks when the switch is turned off.

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Re: Capacitor inside an olympus BHB microscope

#8 Post by blekenbleu » Sun May 29, 2022 12:23 am

smollerthings wrote:
Sat May 28, 2022 2:35 pm
I think that it is to avoid current discontinuity and sparks when the switch is turned off.
Exactly. A transformer is very much like an automotive ignition coil.
Without that capacitor, a high voltage surge when opening the switch
could break down e.g. (lacquer) insulation on transformer windings.
Metaphot, Optiphot 1, 66; AO 10, 120, EPIStar, Cycloptic

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Re: Capacitor inside an olympus BHB microscope

#9 Post by DrPhoxinus » Sun May 29, 2022 7:53 pm

As a ham radio operator I can attest to what a pain old electrolytic capacitors are.

Many were defective not just because of age but erroneous manufacture.

https://en.m.wikipedia.org/wiki/Capacitor_plague

SWmicro
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Re: Capacitor inside an olympus BHB microscope

#10 Post by SWmicro » Sun May 29, 2022 9:31 pm

Also an amateur radio op here,
and I'll second that about electrolytics !

curious thing is that this one is a non polarised cap., which were less prone to spectacular failure :)
From the discussion in that other place, it appears that this one is directly across the mains input and with no surge transient suppression it is vulnerable. Also, if used on 240v mains (Europe) 500v p-p working is a little marginal anyway ??

The inductive load is quite small in this usage, and I think this is more for transient suppression/interference getting back onto the local wiring and causing clicks on other recording lab equipment.

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Re: Capacitor inside an olympus BHB microscope

#11 Post by smollerthings » Mon May 30, 2022 8:23 am

SWmicro wrote:
Sun May 29, 2022 9:31 pm
The inductive load is quite small in this usage
I was wondering on that matter: isn't the transformer coil a pretty large inductive load?
Frankly if it is signal filtering, I will do without. If it is for spark prevention, I would rather have it in there.

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Re: Capacitor inside an olympus BHB microscope

#12 Post by SWmicro » Mon May 30, 2022 10:05 am

smollerthings wrote:
Mon May 30, 2022 8:23 am
SWmicro wrote:
Sun May 29, 2022 9:31 pm
The inductive load is quite small in this usage
I was wondering on that matter: isn't the transformer coil a pretty large inductive load?
Frankly if it is signal filtering, I will do without. If it is for spark prevention, I would rather have it in there.
A bit of a dilemma that one,
discussing an interesting subject in a forum is one thing,
giving advice on what to actually do involving mains voltages is something else ! :)

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Re: Capacitor inside an olympus BHB microscope

#13 Post by smollerthings » Mon May 30, 2022 1:10 pm

I think I will just put a modern 0.1uF X safety capacitor in there and see if the magic smoke arises or not.

Leitzcycler
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Re: Capacitor inside an olympus BHB microscope

#14 Post by Leitzcycler » Mon May 30, 2022 6:38 pm

see if the magic smoke arises or not
If this is like Lomo transformers try to keep the smoke inside. They a powered by smoke and if the smoke escapes they do not function ay more :)

SWmicro
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Re: Capacitor inside an olympus BHB microscope

#15 Post by SWmicro » Tue May 31, 2022 12:41 am

smollerthings wrote:
Mon May 30, 2022 1:10 pm
I think I will just put a modern 0.1uF X safety capacitor in there and see if the magic smoke arises or not.
And that is a whole new rabbit hole to go down ! If you're happy to introduce X cap specs I am happy that you know something about it all and we need not mention Y specs, failure modes etc. et al.
all of which is post that vintage of Olympus knowing best :)

If you are worried about the longevity of the switch then use the switch on the wall socket /outlet :)

The predictability of the occurrence of the emission of the smoke may require divine intervention but we do, nevertheless, expect a pic. of it :)

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