Spot the component

It's obvious init!. It's an engine room heater. 240v in one side, 240v in the other, a big coil of wire in the box and the heat sinks to dissipate the heat. Simples.
 
Ok, this is getting wierd...

Right as directed, taken the offending item out opened it up and...

well pics attached. No I'm no electrical expert, but I did do some electronics on a college course a few years ago, so I know the difference between a diode, a resistor and a transistor. I've knocked up a little circuit diagram because I doubt the components will be clear in the pics. I didn't get as far working out the size of the resistors, started losing the will to live. It took some hours to clean the sikaflex out of the box.

Anyway the key point is that the plugs don't are connected to each other at all except through the chassis ground. There are 2 separate identical circuits that are made up of 2 transistors, 2 resistors and diode. There is no apparent output. The only guesses I have are: Can it smooth the input voltage? or is it just a heater!

Any pics and circuit diagram:
 
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The TIP36C's are swithcing power transistors capable of hadling 25A or so, the TIP41s are being used to drive them, so I would guess that this is some kind of solid state switching for something. Wired off a mains connector because presumably they were cheaper than 25A 12V DC connectors.
 
Are you sure both 'tabs' are actually connected to the chassis? Is the diode a zener diode?

Looks a *bit* like a 'constant current' circuit which might be used for charging nicads or maybe 'gel' batteries from an unregulated supply.

Andy
 
Yep, bolted right through, sorry can't tell one diode from another, it's black with a silver band!

I'm wondering if I'm making a huge assumption here, just because the plugs are labelled L, N, E doesn't mean thats actually what the wiring is connected to
 
I'm wondering if I'm making a huge assumption here, just because the plugs are labelled L, N, E doesn't mean thats actually what the wiring is connected to
As far as I can see, they are solid state switches. The LNE thing is a red herring. N is 0V, E is the control signal and L is switched to 0V. I guess that you would connect one side of a load (say a screen demister or something) to +12V, and the other side of it the L pin on your box. Applying a low current 12V signal to E makes the thing switch on and allows current to flow through your load to ground. Why do it this way rather than use a 12V relay is beyond me, however...
 
Yep, bolted right through, sorry can't tell one diode from another, it's black with a silver band!

I'm wondering if I'm making a huge assumption here, just because the plugs are labelled L, N, E doesn't mean thats actually what the wiring is connected to

Hmm dunno, then. I can't see it does much if B & C of the TIP36C are connected together...:confused:

Any numbers on the diode?

I'm pretty sure you shouldn't connect it to the mains, though :eek:

Andy
 
Hmm dunno, then. I can't see it does much if B & C of the TIP36C are connected together...:confused:
They aren't both TIP36C. One is a PNP and the other is a NPN, which explains why the B & C are connected. The only real way to find out what it does is connect it up to a variable power supply and measure what comes out.
 
They aren't both TIP36C. One is a PNP and the other is a NPN, which explains why the B & C are connected. The only real way to find out what it does is connect it up to a variable power supply and measure what comes out.

Yer but no but....

If you have a look at the schematic he's drawn, the TIP36 B is connected to the TIP41 C leg. The TIP41 C is connected TIP36 C via the mounting bolts. Ergo: TIP36 has it's B&C connected together as the circuit is drawn. It makes more sense if there was no connection via the transistor mounting bolts, when the circuit looks something like a constant current source - generally along these lines (but not 100% the same):

20071022124544764.gif


(probably with pnp & npn transistors reversed, and maybe with a zener diode in the biasing circuit).

Suggest that the next step is to subject it to a "deep water flotation test". If it passes, then we'll have another look :D

Andy
 
I did look for numbers on the diodes couldn't see any. The whole lot was covered in sikaflex so maybe I didn't clean it off enough. maybe it's sikaflex setting circuit.
 
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