ql printer repair woes

[Martin_Head]

Bit of a long shot, (well a lot more than a bit) Try re-soldering the connections on the back of the printhead, in case there is some kind of dry joints after all the years.

[Chr$]

Bit of a long shot, (well a lot more than a bit) Try re-soldering the connections on the back of the printhead, in case there is some kind of dry joints after all the years.

I did consider that, they looked good magnified though. But it's too late now as I opened up the broken print head and everything fell all over the place, pins everywhere in the wrong order etc! So that one is definitely just an ornament now.

[Martin_Head]

Out of curiosity. Do the suspect coils look like burnt, or anything?

[Chr$]

I couldn't really see much. There is a large round magnet where I think the ends of the pins would have been positioned in the middle.

[Dave]

I haven't located the PCB. Would you like me to send this print head?

[Chr$]

I haven't located the PCB. Would you like me to send this print head?

Yes please. Will PM address right now.

Edit: PM not available, I don't have skype set up so will need another way.

[Dave]

Email me: dave@sinclairql.com

[Chr$]

Email me: dave@sinclairql.com

Emailed. I tend to end up in people's spam lately!

[Chr$]

I got the printer head from Dave, so have attempted to repair the printer. I also ordered 3 replacement TK3L10Z transistor packs as they seem to be what drives the print head pin solenoids.

Certainly one of them (the top one of the 3 circled in red) had very different basic resistance measurements over 3 different pins compared to the same pins on the other 2 and the 3 new ones, so I suppose that's a good sign it was a dud (measured out of circuit).

Up-stream from that transistor pack is the 4.7k resistor pack, also circled. That seemed fine. Up-stream from the resistor pack is the large controller chip. But as I feel reasonably confident that the transistor pack 3 is likely to have been bad, I'm not going to the trouble of replacing that oddly spaced unsocketed monster... looks like it's a 2.5mm pitch?

Anyway, I just need to set up the printer near to the main QL and I'll give it a go.

[Chr$]

Three show open, one shows 1.8M, all the rest show 33. Working pull I did a test print on right before taking that pic.

No, unfortunately it is still faulty.

Pins 1, 3 and 4 are not firing. I get the same readings: 6 are around 33 ohms and 3 are open, so that would correspond with the 6 working pins. But if it worked for you, then that would still suggest my PCB has an issue I suppose.

But at least it's all together again and I haven't made it any worse.