Watchman Sonic Oil tank meter failure and repair

>>> .. How to fix it if the 0.33uF capacitor has failed .. <<<

The Watchman Sonic power supply unit/ display meter in the kitchen threw a wobbly.

It was blinking in a funny way – see video.

(Just in case it confuses you the calibration table taped on top of the watchman sonic on the video is my own)

So I tried re-pairing the part that goes on top of the tank with the power supply/display meter a number of times.

The first time I tried this a few months ago it worked.

Then I had to do it again a month or so later and it worked. Then a month or so after that it would not pair at all!

(I had also tried replacing the battery in the part that sits on top of the oil tank. A new battery made no difference)

It had failed.

So I cut all around the edge of the power supply gently with a hacksaw and got inside.

See attached photos below.

>>> No obvious component burn out <<<

So I bought a new complete Watchman Sonic as a replacement.

Then paired the old part that goes on top of the tank with the new wall power supply/display meter. Those parts, old and new, are now working together perfectly.

So I know the problem is with the old wall power supply/display meter.

Since this consists of

• power reduction electronics from 240v a.c possibly to 5 v d.c. TTL
• other electronics including display electronics

can anyone suggest which component(s) have failed (lots photos below) ?

Bear in mind the parts that have failed made a slow failure as described above. Capacitor? Still not sure, and can remember little of my electronics.

Looking forward to your replies !

Thanks 🙂

>>> UPDATE 1 , Thu 09/10/2014 <<<

Turns out that this component (photos below), after searching http://uk.rs-online.com/web for “B32922” (as shown on component) is a 305V polypropylene film capacitor.

• The film will have failed (slowly, which fits with what was observed above).

The capacitor part search is

http://uk.rs-online.com/web/c/passive-components/capacitors/polypropylene-film-capacitors/?searchTerm=b32922&h=s&sra=oss&redirect-relevancy-data=636F3D3226696E3D4931384E4B6E6F776E41734D504E266C753D656E266D6D3D6D61746368616C6C7061727469616C26706D3D5E5B5C707B4C7D5C707B4E647D2D2C2F255C2E5D2B2426706F3D313326736E3D592673743D4D414E5F504152545F4E554D4245522677633D424F5448267573743D62333239323226#esid=cl_4294967294,cl_4294959626,cl_4294956056,cl_4294955811,cl_4294957569,cl_4294467990

and the choices of capacitance offered on the RS site are 0.047µF, 100nF, 150nF, 220nF, 330nF, 470nF, 680nF.

However the manufacturer site :

http://www.epcos.com/action/epcos-en/529294/products/product-search/keyword/529294/search.do?query=b32922

seems to suggest (?) this capacitor part may no longer be made. So the offerings on the RS Components site may be incorrect as far as a replacement goes.

I cannot identify the component properly from the three above photos. Anyone who understands the codes on the device able to do this ?

>>> Can anyone identify this capacitor properly, so we can identify a replacement <<<

>>> Since I reckon this is the failure component that everyone else is getting can anyone recommend a robust non failing replacement ? <<<

🙂

>>> UPDATE 2 , Fri 10/10/2014 <<<

According to page 5 of the following doc
http://www.epcos.com/inf/20/20/db/fc_2009/X2_B32921_928.pdf

the capacitors in the EPCOS beginning part number B32922 all vary slightly in size.

There are only 2 capacitors that are close in size. These are :

• 0.22uF,  7.0 mm × 12.5 mm × 18.0 mm, B32922C3224+*** ◆,  3320 3600 4000 2
• 0.33uF,  8.0 mm × 14.0 mm × 18.0 mm, B32922C3334M*** ◆,  2920 3000 2000 2

The capacitor device size I measure on the Watchman sonic, as best I can is : 17 mm x 7.5 mm x 13 mm, with a lead spacing between the two pins underneath the device of 15mm.

While the top of the capacitor is clearly marked “33 M 305V” indicating a possible 0.33uF device the size is closer to the 0.22uF. The devices are cheap.

The farnell web http://uk.farnell.com/ lists these as

Brand = EPCOS,   Part No = B32922C3334M000,  Description = CAP, FILM, PP, 330NF, 305VAC, RAD,   Farnell order code = 1112844,    cost each = £0.40.

or a

Brand = EPCOS,   Part No = B32922C3224M,   Description = CAP, FILM, PP, 220NF, 305VAC, RAD,   Farnell order code = 1112842,    cost each = £0.37.

an exact size comparison with existing device should give away the correct replacement.

I will get some ordered up, try them out, and post an update 🙂

Farnell web was £20 minimum order and couldn’t think of anything else to order to bring the price up.

Searched B32922C3334M000 and B32922C3224M on http://www.ebay.co.uk and got two of each for £7.72 delivered. Awaiting delivery ! 🙂

>>> UPDATE 3 , Tue 14/10/2014 <<<

This part, B32922C3334M000, just arrived by post.  The 0.33uF capacitor. It’s the same size as the existing.

Here is where I got it www.ebay.co.uk/itm/EPCOS-B32922C3334M000-CAPACITOR-CLASS-X2-0-33UF-305VAC-/181228519169?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item2a320fbf01

So I got the soldering iron out, removed the old one, fitted this new one, taped the unit back together, switched on, and IT WORKS perfectly !!!

Paired it with the part that sits on top of the tank and tested it by moving it to various distances above the floor and the meter reads correctly  🙂  🙂

WATCHMAN SONIC FIXED !!

 

>>> UPDATE 4, Mon 20/10/2014 <<<

If Ur interested to know the purpose this capacitor serves on the circuit board have a look at this simple explanation from St Andrews Uni.

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part5/page1.html

As to why so many PSU’s (eg phone chargers), computers and other electronic devices have failed in recent years, this page

http://en.wikipedia.org/wiki/Capacitor_plague

suggests that “A researcher is suspected of having taken the secret chemical composition of a new low-resistance, inexpensive, water-containing electrolyte when moving from Japan to Taiwan”, thus explaining all the early device failures.

EPCOS, http://www.epcos.com, the manufacturer of this capacitor is a TDK company and whether the original, or even the newly purchased replacement capacitor, is of an old batch made in Taiwan with a defective electrolyte formula is not known.

If the new replacement fails I will source a different : much higher spec, upped voltage capacitor, replacement.

 

ps  .. pls click on images for higher res to identify components