Electronics whizz?

[Andrew_Fanner]

Further down the rev counter saga I've identified a failed component, a rectifier maked SEL B30C50. Is there such thing as an equivalence catalogue to find a modern version, googling suggests that the component is obsoltere and only to be found by firms with a $300 minimum order.

Failing that, the thing turns up to 12VAC into DC, will pretty much any old thing I can solder in do the job? Electronics (and soldering them) is not my forte

 

[savageseadog]

It might be a twin schottky diode stack. How do you know it's bust, if it is bust what caused it?
Can you post a pic of it close up?

 

[Andrew_Fanner]

The device has no continuity through it and all other wiring is fine. The only other compnents on the pcb are a 1K resiistor and a variable pot, presumably for calibration. Photo this evening. As for why it is dead, no idea beyond anno domini or water ingress, I suspect its 37 years old like the rest of the boat.

 

[mikefleetwood]

In answer to your original question - I expect pretty much "any old thing" will do. A bridge rectifier rated at 1Amp @ 50V will cost you about 40p from Maplin, etc.

I am guessing your device has 4 terminals, probably marked +, - and two marked with a squiggle (~) or AC. Any cheap replacement will be marked similarly.

If your device has only two terminals then the replacement is even cheaper. A standard rectifier diode 1N4001 should be about 10p. Higher current devices are more expensive, but I doubt you will need it for your rev counter.

I would have thought that a 37 year old unit was unlikely to use shottky diodes. May be germanium or selenium though - both low voltage drop like shottky, but I doubt if this makes any difference if this is part of the power suplly bit. If it is part of the sensor circuit, then I will wait till I've seen the photo to be sure.

Hope this helps.

 

[rogerthebodger]

Have a look at this site and do a search for the component number "B30C50" and it looks like they have a branch at

Brandt Limited
69 Great Hampton St
B18 6EW Birmingham
West Midlands, England

 

[misterg]

Does it look like this (pdf file)?

If so, it would be a pretty safe bet that a generic replacement would do, and would be worth a try. Guessing a bit, I think the original rectifier would have been 5 amp, 30V (max). Noting your reading of 125v, and because over specifying the voltage rating doesn't do any harm, I would try RS part number 226-5603 which is 6 amp and 400V (£1.55+VAT). [edit] Note that the chamfer on the package is opposite to that on the old datasheet[/edit]

But before you do that - How are you checking for continuity? If you are using a digital meter on its resistance range, then the device may well look like open circuit, even if it is OK. If your meter has a diode test, or continuity range test the rectifier using that. Test from each '~' pin to '+' and '-' pins with the meter leads both ways around. You should get a reading of about 0.6Volts (or continuity) with the leads one way around, and open circuit with them the other way around. A reading of zero is bad.

Andy

 

[Andrew_Fanner]

Thanks for the advice everyone. Photos from my fancy Cybershot phone camera won't resolve the component code on the thing but given the suggestions that a generic part should do I'm off to Maplins this evening to get a part from them, given that they are on the route home. My philosophy at present is that the gauge doesn't work, so pretty much nothing I can do will make it worse.

Yup, four connections +, - and 2 x ~.

To follow, Why Semiconductor Devices Fail When Incompetent People Solder Them Without Using Heat Sinks

 

[Andrew_Fanner]

As promised:
To follow, Why Semiconductor Devices Fail When Incompetent People Solder Them Without Using Heat Sinks

New VDO gauge: most of £200
AQ97 rectifier from Maplins: £0.23
Advice and encouragement from here: priceless.

OK, it was the second 23 pence worth that worked (see above re heatsinks) but I now have both rev counters working and showing the same reading when run off the lathe at minimum speed. To be fitted back to the boat this weekend.

 

[rogerthebodger]

Does yoy gauge and sender have a VDO ref number on them as I would like to conpare with the ones I have.

My gauge number is N 02 012 165 on label on side it is 3000 rpm

Thanks in advance

 

[misterg]

[ QUOTE ]
(see above re heatsinks)

[/ QUOTE ]

Just turn the blowlamp down a bit /forums/images/graemlins/grin.gif

Very pleased to hear you got it working.

Andy

 

[Andrew_Fanner]

[ QUOTE ]
Does yoy gauge and sender have a VDO ref number on them as I would like to conpare with the ones I have.

My gauge number is N 02 012 165 on label on side it is 3000 rpm

Thanks in advance

[/ QUOTE ]

Sorry for delay in reply.

Gauge id is 815/22/2 1:2 7.74, these are very obsolete but, as it transpired, very fixable. Per VDO the 1:2 represents somehting that runs from a generator at about half engine speed and the 7.74 is a date code.

HTH.

 

[hightech]

Sounds like a simple bridge rectifier, so any old generic ariant would do as the current has to be fairly miniscule.