Hello,

As Paul Browning already mentionned in a post on other Forum, measuring Capacitors ESR is a very good thing to get an idea of capacitors performances and health:
ESR means Equivalent Series Resistance. To make simple , bigger is capacitor , lower is ESR.
Exemple : A 4700µf Cap can show a good ESR around 0,02 Ohms, however, a 100µF Cap (Electrolitic too) can show a good ESR around 1 Ohms.

But a 4700µF Cap showing a 1 Ohms ESR (or higher) is poor and will fail certainly soon......

There are number of small tools on WEB to measure ESR for few money and easy to use (first price around 10 Euros)

Some capacitors are sold under label "Low ESR" , often times the are rated up to 105°C : There are designed for "High Frequency current" (Modern Power Supplies , etc....)
Do not use ordinary caps (poor ESR and 85°C Temp limit) for Modern Power Supplies as they overheat and fail early.

Here is a guide chart to give a general idea :




ESR is :
- Frequency-dependent
- Temperature-dependent
- Changes as components age

It is usually only an important consideration in selecting Electrolytic capacitors.

ESR values also depend on Capacitors families (Electrochimical, Tentalum, Polyester, etc.....)

This is great reading! One of the goals for me is to learn more about electronics so I can do more repair work on my projectors. So I love to read things like this!

As someone who does not touch electronics i also find this very informal. Thank you.

these are more important when can understand the reasons and what they do. I tend to check new components too not just the old one's, before they get replaced. I 've learned a bit more since, especially with these machines as old as they are, the beaulieu is one difficult machine to repair, and you can give up or as I do walk away for a time. I have reached my limit of understanding the theory, but I like the hands on part. Philip has been a great help and as helped me move along a bit more , we bounce ideas off each other but he's a good source of info and friendly too, he's a good guy really. As much as I'd like to ask Bill, the man's retired and i don't think its fair to keep firing question at him over the phone, I know people do and if they get there answers then that fine too. its nice to handle a few jobs yourself, but don't get too big for your boots, or it will bite you on the arse.............