buzzing relay

It's a common ac voltage rating for caps

NT

Reply to
tabbypurr
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Yes. I sort of assumed it was part of a conventional DC power supply.

Reply to
Dave Plowman (News)

I have a humidity switch in the bathroom which uses a similar power supply. It started failing (failing to switch off when humidity dropped). I found that the 10 volt rail (zenered) to the level set trimmer was low. Tested the series 0.47uF cap and found that the capacitance was way low - forgotten figure. Replaced with correct value and it has been working ok for months...

Reply to
Geo

Interesting thought. I was wondering about that cap. Is it reasonable to have a cap rated at 275vac in that position, bearing in mind AC mains voltage of 240v RMS peaks at somewhere around 325v ?

Still waiting for the replacement cap to arrive. Ordered from RS, delivered by Parcel Force. Should have come last Wednesday. Following the tracker etc. I see they have an incomplete address and 'delivery was attempted' on that day, but presumably without the full address, delivery unsuccessful! I'll have to chase it up. It's the weekend. Nothing works at the weekend. Groan!

Reply to
Chris Hogg

I had an RS order a few weeks back that did not arrive when expected and the racking info said incomplete address but that is cr4p as my address is spot on on the website and was complete when the package eventually turned up a couple of days later. Parcel force like many carriers are putting more and more load on their delivery drivers and one of the ways of handling the excess that can't be delivered in a working day is to mark incomplete address or address not found. Going back a good few years now RS used DHL for their deliveries and there were no such problems in my deliveries.

Reply to
Bob Minchin

Conclusion: capacitors eventually arrived, an e-mail, phone call and seven days late.

Removed old capacitor and soldered new one in place with no obvious problems, making sure polarity correct.

Result: rather less than total success! Output from full wave rectifier now at 210v DC (was 29v DC) with significant AC component. Relay not working at all and indicator light not coming on. Don't know what went wrong, but seems to be FUBAR!

Sigh.

Sent off for new controller.

Well, at least I tried!

Thanks anyway, folks.

Reply to
Chris Hogg

Oh Well - maybe stick to horticulture and abandon electronics as a hobby lol

Reply to
Bob Minchin

Sadly, I have to agree with you. Everything was OK until transistors came along - components were a decent size back then. Now they verge on the invisible, especially to old eyes :-(

Reply to
Chris Hogg

Trough hole components are still ok even with my old eyes. It's the most common surface mount machine assembled stuff that I give up on. ;-)

Reply to
Dave Plowman (News)

I guess you somehow managed to break the circuit between the rectumfryer chip and the load (including the two voltage clamping zenner diodes). If you're very lucky, that new 50 volt rated cap is also on the load side of the break (otherwise I would have expected it to crack open or fly off its bung like a pressurised water bottle rocket).

Repair right now, might be just a matter of repairing the break (damaged cct trace or a broken/displaced zero ohm smd resistor acting as a bridging link)

Reply to
Johnny B Good

or a bad rectifier diode

NT

Reply to
tabbypurr

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