Olympus BHA

tony.poole · Post by **tony.poole** » Sun Sep 25, 2011 2:09 pm

Hello,

I was using my newly acquired BHA microscope this afternoon when I heard a low hissing and popping noise, then the trip went in my domestic consumer unit. I found the fuse in the base of the microscope blown, but more worryingly there is a light brown cylinder in the base wired just after the fuse, it looks as if it is made of waxed cardboard. Out of one end of this cylinder there is what looks like pink melted wax. Could anyone please advise me or point me in the right direction to get help.

Thank you

Tony P.

ChrisR · Post by **ChrisR** » Sun Sep 25, 2011 4:16 pm

Capacitor? Choke? A photo might help? I have an Oly BHSomething with a load of electrical gubbins I'll never use...

Chris S. · Post by **Chris S.** » Sun Sep 25, 2011 5:23 pm

Tony,

I know very little about microscopes, but do have a pdf of the BH2-MJL Electrical Troubleshooting Manual. I don't know how similar this model is to your BHA, but if you're interested in seein this manual, PM me with your email address, I'll send you the pdf.

Looking at this manual, the next thing in line, after the use, is a transformer. For this model, it doesn't look like a cylinder, but for your BHA, might it? I have no idea.

I note that for the BH2-MJL, there are several parts that come in two versions, depending upon the voltage ("100v" vs. "200v"). These parts include the fuse, transformer, and a few other bits. Is there any chance that your BHA was made for low voltage USA/Canada use, and you are located somewhere with different wall current?

Cheers,

--Chris

SiBurning · Post by **SiBurning** » Sun Sep 25, 2011 7:06 pm

Almost certainly an old paper style electrolytic capacitor, probably installed as a smoothing/storage filter. Even modern electrolytic capacitors will dry out and go bad if not in use for a few years, but the paper ones should definitely be replaced by now. The pink wax might be part of the build--they were sealed with wax, sometimes when installed, and it does drip--so that doesn't say much. Basically, you want to post a picture, and try to capture or type any words and numbers on that part. The problem is that if that went, other parts beyond it could be damaged.

It would be helpful to have a schematic, but barring that, perhaps a picture of the entire electrical system would do. Not sure if it's feasible to fix it over a message board, and you will need a tool or two, but maybe if nothing else comes up...

tony.poole · Post by **tony.poole** » Mon Sep 26, 2011 1:43 am

Thanks to Chris S, Chris R and SiBurning,

I think the old paper capacitor is favourite to be the problem, unfortunately I'm away from the computer and microscope until 7th Oct. I will try and post a photograph then.

Thanks.

Charles Krebs · Post by **Charles Krebs** » Mon Sep 26, 2011 12:15 pm

Tony,

Just looked through my Olympus PDF "stash" but no luck on a BHA repair manual.

If you have no luck tracking down the info needed, you might want to contact Rocky Mountain Microscope Company in Fort Collins, Colorado. (Email: rmmcorp1@qwestoffice.net Phone: (970) 484-0307). Much of their business is repair work, so I don't know how willing they might be to "share" information. But they are the one place I know that very likely has the repair documents and electronic schematics for these scopes.

tony.poole · Post by **tony.poole** » Wed Oct 05, 2011 7:23 am

Thanks to Charles Krebs for that address, I have emailed them, and two images for ChrisR and SiBurning to peruse.

Thanks again

SiBurning · Post by **SiBurning** » Wed Oct 05, 2011 9:22 am

Can't help with just the picture. Everything looks fine in the picture, and that wax looks perfectly normal, at least from that angle. That part looks like a power line noise filter with 3 capacitors inside--you can read the values: 0.1 uF and 2 x 2500 pF all rated for 250 volts ac. If it were mine, I might guess at the configuration and replace it with 3 parts, or just ignore it altogether, but I'm not sure enough to recommend that path for you since that kind of filter can also play a small role in electric safety, preventing surges from passing through--basically when the internal wire breaks or melts. If something beyond that is broken, e.g. if there's a short further down, you'll end up replacing this part again after plugging it in. There were some surges on the US east coast during or after the recent hurricane that took out computers and the like all over, but they happen frequently in many places. But I'm rambling...

Not sure what to recommend, short of getting that repair manual and pulling out a multimeter.

ChrisR · Post by **ChrisR** » Wed Oct 05, 2011 11:57 am

I concur - it should be possible to find something similar, and I doubt very much that it's critical .
Can't read the third line of writing, what does it say?

tony.poole · Post by **tony.poole** » Thu Oct 06, 2011 7:04 am

Hello Chris,

The third line reads:

+1M Omega+2x2mH 1A MPF

SiBurning · Post by **SiBurning** » Thu Oct 06, 2011 4:19 pm

I was wondering why the first word was LCR. So it also has... looks like 2 coils (the L) and a resistor (???) for additional filtering.

... Sorry about the edits... It's hard to follow all of the wiring so I'm really not sure. It might not be where I think it is, in which case it would have a different purpose and a critical one. The values definitely support it being there for noise suppression.

By the way, it's there to prevent noise generated by the bulb from getting into your household wiring, not so much to stop noise entering the microscope. But I see ChrisR already explained that better while I was editing.

ChrisR · Post by **ChrisR** » Thu Oct 06, 2011 4:46 pm

If you google "Supply Filters" etc, you'll find a lot.
This is just one typical arrangement of components inside a filter, you'll find others:

It came from here:
http://www.relec.co.uk/FMLB-41_Series

There are only two parameners to worry about ( apart from getting the connections right

), which are the working voltage, as marked, and the load current. You wouldn't want one cabable of handling a much higher current than your scope draws (1 Amp, it appears).

Note that the positions/designations for the "X" and "y" capactors are standard between makes.
I'm not sure what the 2MΩ is about. It's low to be insulation resistance. If you google enough you'll probably find similar things.

The thing is in there to absorb "spikes" etc on the supply, and stop your scope sending out interference.
I can't think why a scope would be "Susceptible" to interference, so I expect it's all about "Transmission". Some of that could be wire-borne "Conducted" and more "Radiated". Those are the words which are standard in literature.
In other words, it's more about what the thing sends out, than protecting the thing, so in practice it may well make absolutely no difference whatsoever if it's completely missing !.

tony.poole · Post by **tony.poole** » Fri Oct 07, 2011 1:11 pm

Thanks for your posts, I'm waiting for a reply from a chap in America who may have a repair manual.