microscope dimmer circuit

[dengue]

I need help with repairing a dimmer circuit on an old microscope. The bulb is 30 watts and it lights but no dimmer. I apologize if the photos are no good. It is an old style circuit if you can see and I believe the burst grey cannister triac is the problem. Can anyone help with what/where I can get a replacement? It is marked with a line of japanese script and "ES-0001".
Or could I just replace it with a modern say 200v, 6 A triac like SC141B?
Or should I just scrap the whole thing and retrofit a standard wall switch dimmer?
Thanks for any help
dengue

 

[The Mad Professor]

I dare say it could be repaired but a retrofit would be a better option.
Have you considered using LED illumination ?
This might add new use to an old instrument.

 

[dengue]

thanks for your thoughts. I never considered LEDs. Can I impose further to ask for a reference or some leads on designing a dimmable LED circuit? The 'scope was originally and still is, a very capable unit.

 

[philba]

If it were my unit, I'd do exactly what you said. try an appropriate triac first. can't be that expensive. if that doesn't work and there is space, use the premade dimmer. LEDs are fun to play with but it will be a lot more involved than the other two options.

 

[bigkim100]

Actually, your pictures are better than most. Just try any old triac that has a suitable raiting.
There are a crapload of simple dimmer circuits out there (hundreds were found with 1 google search) if you just wanted to start from scratch..since you seem to have quite a bit of space to play with. You can use just a standard wall dimmer as well

 

[Hero999]

Since it's low current a TICP206 will probably do, they're very cheap and quite reliable too. I have loads of these in my junkbox, they're very handy.

 

[JimB]

Excuse me if I am being a bit thick here, but, all the triacs I have ever seen had three connections and came in either plastic or metal packages much like other semiconductor devices.

Things which come in grey plastic wrapped cylinders with two wires look like capacitors to me.

JimB

 

[Hero999]

You might be right but I've seen some very wierd looking transistors before. I've got some that look like capacitors, they are metal cans covered in red sleaving but I'm sure they're transistors.

 

[Nigel Goodwin]

You might be right but I've seen some very wierd looking transistors before. I've got some that look like capacitors, they are metal cans covered in red sleaving but I'm sure they're transistors.

Post a picture of one then! - I'm sure we'd all love to give an opinion?

I also agree that the picture at the start of this thread looks more like a capacitor than anything else - specifically a mains interference suppressing capacitor. It's also the sort of component which is likely to blow a hole through it's side!.

 

[Tarsil]

Hmm...I'd also say that the grey thingie is a capacitor cause of the big hole in it : lol. But I've said about a cap in a pic that's a coil :lol.
About the main problem....Just remove the old components and put something like 4Xwhite leds (I've seen some 5mm/13000mcd @ 20 degrees angle and <.5$) comanded by a variable curent source made with a LM317. de 2X2 goup uses max 80mA @ 3V.
For power supply use a cheap adaptor at 6V or 7.5V and 2&2 leds in series.

 

[dengue]

wow - thank you all for the feedback. sorry to break up the transistor capacitor triac debate, but it's my bad photography that did it. The blown grey beastie has 3 wires:blue red and brown.
If I replace it with a TICP206 as hero999 suggests, where should I place a fuse to prevent it from blowing up again? thanks

 

[Hero999]

Nigel,
I'd love to post a picture but I can't find my digital camera.

dengue,
Place the fuse on the phase/live/hot conductor series with the whole circuit.

 

[Nigel Goodwin]

wow - thank you all for the feedback. sorry to break up the transistor capacitor triac debate, but it's my bad photography that did it. The blown grey beastie has 3 wires:blue red and brown.
If I replace it with a TICP206 as hero999 suggests, where should I place a fuse to prevent it from blowing up again? thanks

Check EXACTLY where the wires from it go, three wires is common on mains suppression capacitors - it doesn't resemble a triac at all?.

 

[JimB]

Looking through the hole in the side of the grey cylinder, there appears to be a coil, judging from the colour. Could this thing be a mains filter?

JimB

 

[Tarsil]

How about taking the circuit apart an replacing it with a modern version. The circuit itself is quite hard to repair not knowing what every part does (grey or not ).
After that u can post a lot of pictures of the canister for easier identification. U realy want to rely on a....30 Y old pot, cap etc.?

 

[Hero999]

You could by a simple wall-mount dimmer switch, strip out the circuit and use that.

 

[dengue]

here are more pictures and a schematic of the circuit. now what do y'all think?

 

[Hero999]

Are you sure that 150uF capacitor isn't 150nF?

Anyway, looking at the schematic, I garee it's probably a triac but it does look different to a standard phase controller.

 

[kchriste]

There is something wrong with that diagram, because it shows all the mains current passing through the control POT. It looks like you've confused the black on/off switch wires with the ones that go to the legs/wiper of the POT. I see a total of 4 wires going to the POT/Switch in your first pic. Check it again.

 

[dengue]

Actually there are 3 wires to/from the control pot: black 120v TO the on/off. brown FROM the on/off to the wiper. Then brown and blue from the leg/wiper to the circuit. I'll put a fuse in series before the pot as hero999 suggests. But it does look like yes the mains current goes straight to the control pot.
The cap is labelled "Sprague Atom. TVA - 1207.5 150UF-25vdc"