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Test Capacitors

Luxman Amplifiers India

lifewater

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Hi, having seen so many posts of re-capping of vintage amps, building new circuits etc, I would like to pose this question to all of you "HOW DO YOU TEST A CAPACITOR ?". Now we can always do so with a capacitance meter, but the problem arises when the ESR factor creeps in. For a casual DIY'er like me I have access to a digital VOM meter and also a LCR meter but is a high price gadget like ERS meter justified for me ??.

Many a times we hear "The caps all look okay with capacitance within limits but with HIGH ESR, so it has to be replaced". now how do we take a decision to re-cap a high-end vintage amp with only the defective(physically looking OK) capacitors replaced. Or how to pull out a cap from our parts bin and confirm it id "OK" and use in a circuit like say Myref or DCB1 or a Pass B1.

Regards,

Lifewater
 

linuxguru

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... For a casual DIY'er like me I have access to a digital VOM meter and also a LCR meter but is a high price gadget like ERS meter justified for me ??.

There's a component tester available on EBay and various other places that uses an ATMega328 microcontroller driving a 2-line LCD display, which can test a whole lot of components, including the ESR of electrolytics. The meter itself is an open-source HW/SW project, so you can build one yourself for less than Rs.500..1000. However, it's just around $20 or thereabouts on EBay, so you can buy a ready-made unit if you wish. I have one, and it's a life-saver for testing both actives and passives - in particular, it can autodetect pinouts of BJTs and FETs.

It measures ESR with a resolution of 0.01 ohms, which is fine for almost any application, except maybe motherboard VRM bypass caps, which typically have ESR below 10 mohms. Even there, it's only faulty caps with high ESR that need to be weeded out, which is still possible with this meter.
 

lifewater

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There's a component tester available on EBay and various other places that uses an ATMega328 microcontroller driving a 2-line LCD display, which can test a whole lot of components, including the ESR of electrolytics. The meter itself is an open-source HW/SW project, so you can build one yourself for less than Rs.500..1000. However, it's just around $20 or thereabouts on EBay, so you can buy a ready-made unit if you wish. I have one, and it's a life-saver for testing both actives and passives - in particular, it can autodetect pinouts of BJTs and FETs.

It measures ESR with a resolution of 0.01 ohms, which is fine for almost any application, except maybe motherboard VRM bypass caps, which typically have ESR below 10 mohms. Even there, it's only faulty caps with high ESR that need to be weeded out, which is still possible with this meter.

Thanks very much Shiva. However international shipping to Assam is a big problem. I tried to get many stuffs but failed miserably.:sad: Any other options in India. Or any other way to go about it ....

Thanks

Lifewater
 

omishra

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For vintage gears we generally change following caps without testing or look by visual appearance of bulge, leak etc -

Electrolytic caps: on power supply rails and small decoupling caps near sub modules. I never test it and replace it it its 20+ years old.

Ceramic bypass caps: take decison after looking original. Mostly retain it. no change

Signal passing caps: Silver foil, Non Polar electrolytic. Silver foil retained while electrolytic upgraded to better one.

Other caps: retained

Tuning caps, trimmers etc: Retained.
 

linuxguru

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Wonder which one ? There are several listed on Ebay with wildly differing cost.

Maybe this one: ESR Meter Digital Transistor Tester Diode MOSFET Diode Capacitance mos PNP NPN | eBay

There are some with an ATMega168 (and slightly reduced functionality) and others with an ATMega328 (which are more expensive, but can do additional stuff, like depletion-mode JFETs and MOSFETs). If all you want to measure are capacitances and ESR, you can go with the $12 ones.

FM Quad has built one using locally available parts, and several others including me have plans to clone the 328 board using Eagle. I have local vendors for all the parts including the LCD display and the ATMega328. The most expensive part is probably the Textool ZIF socket. No timeframe for the completion of the layout, but it can be done within a month if there's a will.
 

quad

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FM Quad has built one using locally available parts, and several others including me have plans to clone the 328 board using Eagle. I have local vendors for all the parts including the LCD display and the ATMega328. The most expensive part is probably the Textool ZIF socket. No timeframe for the completion of the layout, but it can be done within a month if there's a will.

Transistortester mit AVR - Mikrocontroller.net
AVR-Transistortester - Mikrocontroller.net

Eagle layouts are available from the links above. Or I can post my
copy here if someone is interested.



However, you can easily build it on general purpose perf board. The most
expensive components are the Atmega8, 16x2 LCD display and the
ZIF socket (optional), so can be built under Rs 300 locally. You need
a way to burn the hex file to a Atmega8, or someone to send a
pre-programmed one.

The ebay versions have much fancier bit mapped graphical displays,
including OLED etc
 

lifewater

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Messages
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Location
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There are some with an ATMega168 (and slightly reduced functionality) and others with an ATMega328 (which are more expensive, but can do additional stuff, like depletion-mode JFETs and MOSFETs). If all you want to measure are capacitances and ESR, you can go with the $12 ones.

FM Quad has built one using locally available parts, and several others including me have plans to clone the 328 board using Eagle. I have local vendors for all the parts including the LCD display and the ATMega328. The most expensive part is probably the Textool ZIF socket. No timeframe for the completion of the layout, but it can be done within a month if there's a will.

Hi Shiva, thanks for the pointer. I am interested too if you build one. I am sure lots of others would be too perhaps a group buy.

Thanks to Quad for doing the good work.

Best wishes,

Lifewater
 

lifewater

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Fantastic

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The HTC CM1500 can measure up to 200,000uF ! That covers all possible power supply capacitors !
The MASTECH can do only 20uF max. Neither seem to do ESR.
 
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