Alphacom from eBay with defective power supply

[mrtinb]

Hi

Today I received an Alphacom from eBay, but when it arrived, it had a defective power supply. (The description on eBay said it would turn on, but otherwise not tested. It didn't turn on.)

The supply says: Input AC240V 50Hz Output AC26.8V 1A. When I measure it I get a shift between 0.0V - 0.1V AC.

I tried to find some old power supplys in my basement, but unfortunately they supply DC output.
One is: Input 240V AC Output 22V DC 0.6A
Another one is Input 230V AC Output 24V DC 550mA

Any suggestions?

[PokeMon]

Hmm I would try this one. 24V AC is not too far from specified 26V AC - so would give it a go.
http://www.ebay.de/itm/222423447396

[Moggy]

Hmm I would try this one. 24VA is not too far from specified 26V - so would give it a go.
http://www.ebay.de/itm/222423447396

I would also take chance on this one, I have just looked inside my Alphacom and the only power reg I can see is the usual 7805 for 5v and a TIP100 Darlington power/switching transistor which I suspect may be there to control current to the printing platen.

Either way please persevere Martin as the printer is a good one with paper readily available.

I assume plug fuse has been checked (not sure if there is an on-board one) mains and output cable checked for breaks etc

[1024MAK]

I think, if the AC voltage is too low, the thermal print head will produce poor contrast. Some years ago, I was playing about with a non-original supply. Then again, it could have been something else.

Mark

[PokeMon]

Well 10% less is not that significant I would say.
So you will get maybe only 90% blackness but anyway you could check if the printer is working in general.
If heating is just a resistor (wire) you could try a DC power supply as well and maybe could try optimum with an adjustable PS.
So I would try ...

[1024MAK]

Sorry, my post was a bit misleading. The supply I tried was a lot less than 24V AC.

Mark

[msansom]

I'm fairly certain that the original power supply was an unregulated transformer. If so, a modern regulated 24V should work just fine. Certainly an unregulated supply isn't going to be accurate to better than 10%.

I would probably like to find one rated for the full 1A output if possible though unless that printer is known to run on less.

[mrtinb]

I'm trying to open the power supply. Has anyone here tried to do that?

I removed the 4 screws at the bottom, but somehow it seems to be glued together as well. I don't feel like opening it with a hammer but the sides are unmoveable.

[mrtinb]

Maybe the heat from the transformer, at melted the plastic together.

[1024MAK]

Big Clive on You Tube sometimes uses a vice to open plastic cases that have been glued closed.

Mark