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Unidentified tantalum capacitor

birdleg84

May 29, 2023
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Hi there,
I am currently repairing an old Hammond organ and am trying to get the foot pedals working. So far I have eliminated faults with the wiring and switches and have come across these 2 tantalum capacitors. (See photos attached). They appear to be open circuit and not holding any charge as far as I can tell. Although I am not the most experienced at these things, when testing other tantalum capacitors on the board with the multi meter set to ohms, the value slowly increases. However these ones don't.

One of the capacitors appears to have some sort of Japanese writing on it which I can't figure out what it says the value is. Can anyone help me figure out what this capacitors value is so I can replace it?

Thanks
 

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Delta Prime

Jul 29, 2020
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Welcome to Maker Pro
:)
47 microfarad
The one behind it's one microfarad
You have to unsolder one lead cannot test it in circuit.
Could you take another photo it's too much reflection just to be certain thank you
 
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Delta Prime

Jul 29, 2020
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Those type of capacitors will usually pop spectacularly.
 
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birdleg84

May 29, 2023
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Welcome to Maker Pro
:)
47 microfarad
The one behind it's one microfarad
You have to unsolder one lead cannot test it in circuit.
Could you take another photo it's too much reflection just to be certain thank you
Oh right I will de solder it and see if I can get a better photo. It is the back one that I wasn't sure of
 

Delta Prime

Jul 29, 2020
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Oh right I will de solder it and see if I can get a better photo. It is the back one that I wasn't sure of
If you use the multimeter to test "in circuit" the capacitors, independent of what type they are, it was done incorrectly you have do it all over again. I think you are just curious but that's a good thing.
Quite frankly I think you're good to go everything looks all right from what I can see anyway.
 
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kellys_eye

Jun 25, 2010
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The only proper test for electrolytics (or tantalums) is for ESR - if their value is within tolerance and their ESR reads acceptably then they are good-to-go. This measurement can only usually be achieved out-of-circuit.

Your main issue will be the capacitors BEHIND the tants as they look 'blown' (rounded top) and it's that type that fail first either due to age or for heat-related issues. Tants usually either 'work' or 'flame out' spectacularly - there are seldom in-between states for them.

Most 'old' equipment - certainly of the era yours looks to be - bnefit from a COMPLETE recapping (of electrolytics) - unless the tants are shorted or physically damaged they can remain.

Don't forget to note the polarity as you remove them and ensure replacements are similarly polarity-fitted.
 

birdleg84

May 29, 2023
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That's okay! I'm not trying to beat you up! I'm on your side. :)
I've tried to get a better photo now that it is out of the circuit, however it is a bit blurry and hard not to get reflections.

Also now that it is out of the circuit it seems to be working fine. I now know I need to remove them to test. Thanks
 

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birdleg84

May 29, 2023
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The only proper test for electrolytics (or tantalums) is for ESR - if their value is within tolerance and their ESR reads acceptably then they are good-to-go. This measurement can only usually be achieved out-of-circuit.

Your main issue will be the capacitors BEHIND the tants as they look 'blown' (rounded top) and it's that type that fail first either due to age or for heat-related issues. Tants usually either 'work' or 'flame out' spectacularly - there are seldom in-between states for them.

Most 'old' equipment - certainly of the era yours looks to be - bnefit from a COMPLETE recapping (of electrolytics) - unless the tants are shorted or physically damaged they can remain.

Don't forget to note the polarity as you remove them and ensure replacements are similarly polarity-fitted.
Thanks for that, I will replace those capacitors. I thought they still looked ok but as I said I'm not that experienced. Those capacitors don't appear to be part of that particular circuit for the pedals if I follow the traces but I guess it couldn't hurt to replace them.
This organ was built in 1979 so it is getting up there in age.
 
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