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Best Electrolytic Capacitor to Recap an Oscilloscope?
ResistorRob:
I have 2 vintage oscilloscope that have issues related to old/defective electrolytic capacitors.
Can someone tell me what I should be looking for in replacement caps? I obviously know about capacity, voltage, temperature, and going with a name brand. What I don't know is the secondary specs like ESR. If someone has a specific series of capacitor I should use that would be amazing help. As an example Panasonic sells like 10 different series of capacitors. I can eliminate a few, but I'm not sure how to select what I really need. I only want to do this once and have it last at least 5-10 years, so cost is not a factor. I'm really good at soldering and safety procedures, so I just need to know what to buy.
electricMN:
Look at the capacitors you're taking out and get the datasheets for them. Then find equivalent replacements if you can't get the originals.
rsjsouza:
Just a few of my observations along the years. I am pretty sure you will find other opinions around.
If cost is not a factor, in general you are looking at the highest working temperature versus number of rated hours. Also, polymer or tantalum capacitors usually have a longer lifetime. In some cases you may need to carefully look at the ESR so you don't blow any diodes at power up. Also, sometimes you need to fit a capacitor in its alotted space, so the dimensions are important - IME ultra small capacitors always compromise on one or more of the prior specs above.
In certain spacious places you can also reduce the stress on the capacitor by using a higher voltage part.
One additional detail is that, in certain places, it may be tempting to replace a lower value electrolytic with a MLCC (they can potentially last forever). However, the circuit may be designed to work with the inferior frequency response of the electrolytic and therefore nowadays I only replace them with the same approximate type (sometimes poly or tantalum).
Soulfetish:
What's the make? I know that Tektronix of a certain vintage (465 comes to mind) use radial electrolytics with a unique mounting footprint. Someone designed a universal PCB adapter to allow you a lot of flexibility in choosing the best currently manufactured replacement. Below is a link to an example sold on ebay (no affiliation) if you need it:
https://www.ebay.com/itm/Capacitor-Adapter-Tek-Tektronix-7000-Series-Recap-6-square-1-triangle-adapter/272799971348
Miti:
In the power supply I always use Nichicon PW series, they never failed me. I’ve also used them to recap the main board of a Tektronix 2445B. In general I only use Nichicon and Rubycon in all my important repairs.
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