Electrical Question

I've got a kaput PC power supply with switch and power socket if thats any good? Still have to make up a fuse holder though. Even comes with a power lead.

Peter

Can't you hard wire something in place to bypass the fuse, then fit a separate fuseholder? Maybe an inline fuseholder inside the case?

BTW I was happily milling the flats on a big bronze propellor nut the other night when all the lights went out. The RCD in the house had tripped, & it's an 80mA job, not super-sensitive.

Could find no obvious cause for it, my first thought was that my son had done something daft in the house & blown himself up! After progressively switching stuff back on, & nothing tripping the supply, I realised that the DRO has failed. It's a Heidenhain VRZ

731B. The main displays are just showing a red light at each end, no numbers. I've noticed a bit of a rancid smell the last couple of days, thought it must be some stale coolant, but I've just twigged it was coming from inside the DRO! Not a hopeful sign, I'll investigate further tonight as the cold North wind blows straight in through the workshop doors & I can look at that in the warmth & comfort of the kitchen.

Getting back to fuses, the fuse on my DRO wasn't blown.

Cheers Tim Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

sell him your fuse

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

Tim

I could hard wire and insert another fuse - a touch messy but manageable. I thought that I'd ask first before I look at that!

Peter

Thanks for the suggestion - I also have a loft full of dead PC's. the benefit of this unit is that it's a fuse, switch, connector and emc filter in one!

Regards

Charles

R.S. # 352-1796 or 352-1819 ??

rswww.com

Shout!

It should be a Schurter or 'Teller' product, with hopefully a part reference around the body near to the approval logos.

We have a pile of these things, all new but there are many variants and I don't know which ones until I have a beak.

The right-hand panel either has a mains voltage selector or twin fuses.

We may well have the fuse carriers for this, but it would take a day to dig through the pile of stock.

Peter Peter

-- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk

Peter

The one in it at the moment is a Corcom unit - and I've trawled their website and it appears to be an obsolete model, hence the posting. It has a sort of twin fuse arrangement, not a voltage selector. By that I mean one fuse and what looks like a steel rod!

If you have a fuseholder, or even the whole thing in a similar size get in touch and money can change hands.

Thanks

Charles

What is the steel rod? Some of these had a space for a spare fuse.

Chuck P.

That is the spare fuse, if the first one blows just swap it for the steel rod -that won't blow!!

Regards Kevin

Charles would these modules fit:

items 26 and 27. Digikey are US based but prices include duty and shipping if you use the site. Martin

I can send one FOC, we have loads of them, but need to find the fuse carriers first, as without those, it is useless.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

Ahh, I should know that these things are never as simple as they first sound. Then I go and embarass myself again with my electronics ignorance:) Its the thought that counts, as my mother used to say....

Peter

Thanks Peter - have a root and tell me what you find!

Charles

OK, I'll try and get that sorted today, we are finished at Wembley until next week as they are painting the depot platforms and need the weekend to let it all dry off/harden.

Peter

-- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk

There's what looks like a smoothing electrolytic on the power supply which has blown an end out, that should be fairly simple to replace but the worry is what else it may have taken with it. Does anyone have access to a wiring diagram for these things?

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Another thing at high risk are the rectifier diodes. Check if any of them have gone dead short. (This would put quite a hefty ripple current through the capacitor - indeed, may well be what blew the electrolytic)

- Brian

Looked a bit closer this morning, two tracks on the PCB have melted. It looks superficially as though there are 3 separate DC supplies, each with a bridge made of individual diodes and a single smoothing electrolytic. Trying to check all the diodes while still wired in, but the DRO circuitry unplugged, with my DMM, doesn't seem to establish much as they all show roughly the same resistance in either direction (500 to 700 K), except the 4 apparently linked to the duff cap which are a bit lower. The diode test function on the meter tells me nothing. I'm guessing the battery voltage in the meter isn't enough to give forward conduction on these particular diodes - is this likely? It's a *reasonable* quality meter, bought from RS some time ago, not a Fluke but not junk. Maybe the meter battery is a bit low, but it's not saying so. Semiconductors aren't really my forte

I've gone cross-eyed trying to follow the (quite simple) double sided PCB tracks

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

coming

further

kitchen.

supply

replace

electrolytic)

direction

sided

Tim,

Typically you need only 700mV to forward bias the diodes. A simple

1.5v battery and bulb (not led) would do as a diode tester.

Mind you as they are pence each I'd probably change them anyway.

AWEM

Some success this evening, after a trip to maplins to clean them out of suitable bits.

I replaced all the diodes on the circuit with the duff cap, turns out two were definitely faulty, & replaced the diodes on the 'high power' circuit. They didn't have enough diodes to replace the ones on the third circuit but I unsoldered them & they tested OK. I replaced all electrolytics, and bridged the burned out tracks on the PCB.

Checked the voltage outputs on the plug to the main circuit, the readings didn't make a lot of sense - there's a 24V circuit on the power board & no 24V to the main electronics - but decided to connect it all together anyway and - hey presto - all the displays light up & behave as they should. Time for food now, I'll test it on the machine in the morning.

Thanks

Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service