Is there a Capacitor Reforming Service in Australia? - Page 1
Forum section: electronics / repair

author: Domokelly
author_rank: Contributor
timestamp: January 19, 2021, 03:12:31 am
content: Hi everyone,I have a Tek 545B which is in excellent condition, but hasn't been powered in a while.I've read from a few places (including from Mr Carlson's Lab) that the Tek caps of this era were very durable and often don't need to be replaced.So I don't want to replace them if I don't have to- but at the same time some of them are rated up to 475V and I don't have the equipment to reform caps of that voltage.So I was wondering If anyone knows if there's an individual or company who will reform the caps for me?I'm in Sydney, Australia and there are 17 caps in total, 250v-475v and 10uf - 150uf.Cheers, Dom

author: WattsThat
author_rank: Frequent Contributor
timestamp: January 19, 2021, 03:38:07 am
content: here we go again. There is no such thing. Turn it on and leave it on for a couple of days. All reformed. If they go boom, you need new ones.

author: TMM
author_rank: Frequent Contributor
timestamp: January 19, 2021, 05:32:16 am
content: Safest way is to turn it up slowly on a variac with a incandescent bulb current limiter, or remove each cap from circuit and turn it up slowly on a current limited high voltage DC power supply.FWIW I considered the caps in my Tek 536 bad even after 'reforming'. Leakage in the milliamps = watts of dissipation per capacitor can. Would it have ran without exploding, probably yes, but I wouldn't risk them getting any worse and taking out tubes or the unobtainable power transformer.

author: Runco990
author_rank: Frequent Contributor
timestamp: January 20, 2021, 04:28:05 am
content: Tube scope? Bring it up slowly on a variac. Then let it run for a day.Opinions on caps differ, so I won't get into that. Just bring it up sloowly at first.

author: nexus
author_rank: Regular Contributor
timestamp: January 20, 2021, 05:38:26 am
content: If you actually want to use the instrument long term then I would simply remove the old caps and find new replacements. If you're going to take an iron to it and physically pluck the old capacitors, there is no point in trying to preserve them.As long as you match the voltage and capacitance ratings, you shouldn't have any issues; I don't see anything inside of an old scope needing special properties like high ripple current etc.If the instrument is just furnishing on your mantlepiece then no need to worry about reliability, leave the dusty old caps where they are.

author: nanodocl
author_rank: Contributor
timestamp: January 22, 2021, 10:21:58 pm
content: I did not know caps can be reforming. Is this possible?

author: Runco990
author_rank: Frequent Contributor
timestamp: January 22, 2021, 10:53:57 pm
content: Caps are initially "formed" at the factory. This is an electro-chemical process. Under normal use, the "forming" remains. If a cap sits un-used a long time, it fades. So to be safe(r), it is a good idea to "re-form" a long dormant capacitor. In theory, if it is still physically sound, it should resume working normally. But it is NOT a way to save failing capacitors, in case the "Vintage Marantz Sound" crowd is listening.If you google it, there are papers on this subject.

author: AlfBaz
author_rank: Super Contributor
timestamp: January 22, 2021, 11:07:01 pm
content: A lot of VSD manufacturers recommend reforming their DC bus caps if not used for more than 4 years.I recollect installing a brand new Siemens drive that had, as part of its installation procedure a mandatory step for reforming the bus caps prior to first time use. Admittedly this was 20+ years ago so things may have changed

author: serg-el
author_rank: Regular Contributor
timestamp: January 22, 2021, 11:12:00 pm
content: Based on our experience and manufacturer's recommendations, capacitor recovery is possible. Limit the current through the capacitor to 10 mA. Wait a day. The reform will be completed.

author: serg-el
author_rank: Regular Contributor
timestamp: January 22, 2021, 11:15:32 pm
content: According to the instructions, it must be turned on with a reduced voltage. And wait at least a day.

author: Runco990
author_rank: Frequent Contributor
timestamp: January 23, 2021, 02:44:47 am
content: Quote from: serg-el on January 22, 2021, 11:12:00 pmYes, providing the capacitor is internally still GOOD. An old leaky cap won't come back.I hope that is obvious to everyone here, but I am on forums where hope is high.

author: aqibi2000
author_rank: Regular Contributor
timestamp: January 23, 2021, 02:45:53 am
content: Anyone used a RC battery pack charger/discharger on a cap to see if it can help reform?

author: helius
author_rank: Super Contributor
timestamp: January 23, 2021, 04:17:38 am
content: Quote from: aqibi2000 on January 23, 2021, 02:45:53 amFor one thing, you are going to have a pretty hard time finding RC chargers with 500 VDC output.For another, they do not normally continue operating below a certain holding current (because from the charger's perspective, the battery has been fully charged). This means that they cannot reform a capacitor. Some advanced chargers may have a "refresh" function that uses a timer instead of current cut-off.The type of instrument that has been designed for testing and reforming capacitors is the Sprague Tel-O-Mike. A HV leakage tester like the Sencore LC-53 can also be used. These have selectable output up to 600 VDC and display leakage in milliamps. They can be set to operate for hours or days as required for reforming.

author: austfox
author_rank: Regular Contributor
timestamp: January 23, 2021, 09:03:12 am
content: Silicon Chip did a reformer project in 2010:https://www.siliconchip.com.au/Issue/2010/August/Electrolytic+Capacitor+Reformer+%2526+Tester?res=nonflash&page=-1

author: Gyro
author_rank: Super Contributor
timestamp: January 23, 2021, 11:56:00 am
content: Haha, always a good idea to use a Pic micro when a simple resistor will do.

author: CJay
author_rank: Super Contributor
timestamp: January 23, 2021, 12:53:43 pm
content: Quote from: Gyro on January 23, 2021, 11:56:00 amTo be fair, it is a tester as well as a resistor