Replacement Enlarger Tranformers - U.K.

[pmarshall]

The Transformer for my Meotpa Omepus 6a has stopped working - no 12DV output and now the On/Off Switch is stuck in the Off position.

So my question is where can I get a replacement stabalized transformer (12V DC Output 100W ( i.e. 8 1/3 Amps ), in the U.K. - preferrably cheaply !

Many Thanks.

Peter

 

[rjr]

Check ebay.de - any enlarger transformer will do, you just might have to adapt the cord/plug. Especially the Kaiser transformers are cheap these days, selling for less than 25EUR plus shipping. "Trafo" is the german word used for transformator.

Another option is the DIY hardware store in your neighborhood, look for these halogen lamp kits - the transformers in these kits will do it fine for a while and they are both plenty and cheap.

 

[GeorgesGiralt]

Hi Peter !
Is the transformer dead or just the power switch ?
Try to figure out by measuring the voltage arriving at the transformer, after the switch. It is somewhat unusual for a transformer to die, unless it is so badly enginereed that it became a heater....
If by any chance, it is dead, go to any electronic shop and ask for a toroidal 12 V transformer (primary is your mains voltage here 230 V and secondary is 12 V) when asked for rating give them the power of the bulb you use, form memory, 100 W. You will get an ever lasting unit and of very good quality for a few pounds.
Please keep in mind that electricity is a dangerous and lethal thing if not handled properly ! So if you do not feel capable of handling this repair, keep it to a porfessional ! Life is so short !

 

[pmarshall]

Hi Peter !
Is the transformer dead or just the power switch ?
Try to figure out by measuring the voltage arriving at the transformer, after the switch. It is somewhat unusual for a transformer to die, unless it is so badly enginereed that it became a heater....
If by any chance, it is dead, go to any electronic shop and ask for a toroidal 12 V transformer (primary is your mains voltage here 230 V and secondary is 12 V) when asked for rating give them the power of the bulb you use, form memory, 100 W. You will get an ever lasting unit and of very good quality for a few pounds.
Please keep in mind that electricity is a dangerous and lethal thing if not handled properly ! So if you do not feel capable of handling this repair, keep it to a porfessional ! Life is so short !

I have checked with a multimeter, and it appears to be dead - nothing transferred across the switch. I will look for a toroidal transformer next week.

Thanks for your help.

 

[GeorgesGiralt]

Hi Peter !
"nothing transfered across the switch"....
I wonder if I understand this sentence correctly ?
mains (L) -----> switch -----> transformer ------>12 VAC
mains (N)------> switch -----> transformer ------> to bulb
If you use the multimeter, you will measure 230 V between Live and Neutral. Before the switch.
After the switch you will have 230 V when the switch is ON and 0V when OFF.
So if you check 230 V on the transformer primary when switch is on and you have 0V instead of 12 VAC at the output transformer dead.
If you do not check 230 V after the switch whatever position the switch is, the switch is dead.
BE carefull not to touch any exposed wires with your bare fingers !
Last but not least, there may be a fuse present in the circuit. Double check this one is not dead.... (some sophisticated units incorporate a thermal sensor switch to protect the transformer from burning through overheat... you need the schematics if the wiring is more complex than the one I've tried to depict above)
In case of doubt, bring the unit with you when going to order the transformer, they can check it for you and it may be usefull to choose a model able to fit in the box...
HAve a nice day !

 

[Ian Grant]

Why not try:

Meopta UK, 161 Ballards Lane, Finchley N3 1LG. Tel: 020 8371 9845 Fax: 020 8371 9844
www.meopta.co.uk

Also your looking for a very common voltage supply, try Maplins or RS Components if Meopta themselves can't help you.

 

[Bob F.]

I had a look on the Maplin site but the only PSUs with sufficient power that I could find are 13.8V (which may, or may not be, OK - probably is OK). It is probably possible to adjust them down to 12V but without the cct diagram or the PSU itself in front of us there's no way to tell.

Meopta enlargers are reasonably priced, so checking with them is probably the best option and only look for alternatives if they want large wads of cash for a power unit.

Peter, sniff the transformer - if it has a strong sickly sweet smell (the smell of burnt lacquer) then it may well be burnt out but as previously noted, this is unusual. Most likely are any fuses as already stated and any switches and the wiring between them. Anything else will need a repair person or someone with basic electronics knowledge to fix as that only leaves the regulation circuitry - I'm assuming there is a circuit board in there with some components and a power transistor or two on heatsinks? If no regulation circuitry, then things get a lot easier...

Bob.

 

[pmarshall]

I had a look on the Maplin site but the only PSUs with sufficient power that I could find are 13.8V (which may, or may not be, OK - probably is OK). It is probably possible to adjust them down to 12V but without the cct diagram or the PSU itself in front of us there's no way to tell.

Meopta enlargers are reasonably priced, so checking with them is probably the best option and only look for alternatives if they want large wads of cash for a power unit.

Peter, sniff the transformer - if it has a strong sickly sweet smell (the smell of burnt lacquer) then it may well be burnt out but as previously noted, this is unusual. Most likely are any fuses as already stated and any switches and the wiring between them. Anything else will need a repair person or someone with basic electronics knowledge to fix as that only leaves the regulation circuitry - I'm assuming there is a circuit board in there with some components and a power transistor or two on heatsinks? If no regulation circuitry, then things get a lot easier...

Bob.

There is no smell from the transformer, but the switch on the back will not stay in the 'on' position. The transformer is a sealed ( rivetted ), unit so I cannot check the internals. However when I put the multimeter across the output terminals it is dead, but there is 240v a/c on the input side. I have got a toroidal transformer ( 12v / 100w output ), which I will try.

Meopta want £80 for a transformer

 

[pmarshall]

Just to let you know, the £20 toroidal transformer works perfectly.Thanks to everyone for their help.

Peter

 

[Bob F.]

... of course, the most unlikely cause DOES sometimes occur... (he said, backpedalling rapidly ).

Glad it was a straightforward fix anyway!

Bob.