vB Easy Archive - Repair Bag Phone Handset LED?

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Repair Bag Phone Handset LED?
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Posted by: Dagorath

I purchased a Motorola bag phone back in 1996. I am not sure what the model is but the handset has the red LED display as opposed to the LCD display that came with other bag phone models. One of the manuals I have suggests the model might be SJN4976B but I'm not sure. Can any of you Motorola buffs tell me anything about the model number?

The phone works well but the LED display in the handset stops working occassionally. I have paid twice to have it repaired and now it is broken again. I don't feel like paying to have it repaired again.

I have heard it's very easy to fix, just a burned out component on the circuit board in the handset. I can desolder and replace small surface mount components but I have no idea exactly which part(s) need to be replaced. Can anyone tell me which part(s) need replacing? Is there a mod I can do to prevent it happening again? Any links to pics that identify the part(s)? Any advice would be helpful, thanks.

Posted by: DaILoMaC

got pics??

Posted by: jsmithepa

we're buffs, not museum techs!

The entire display goes blank or just certain segments burn out? LED don't really burn so my initial reaction is, cold solder joints. Previous repairs just replaced the module, which have the same manufacturing defect.

Posted by: Dagorath

Here is a pic, transciever and handset removed from carry bag. The 7 lower buttons are not very clear. They are:

RCL

CLR STO SND

PWR FCN END

Posted by: Dagorath

Quote:

Originally Posted by jsmithepa

we're buffs, not museum techs!

Museum techs, lol.

The entire display goes blank. LEDs do burn if they draw too many amps, just hook one up with insufficient resistance in the circuit if you don't believe me. They can be over-volted to some extent but excessive current fries them instantly.

Anyway, I've had it repaired twice at 2 different shops. Both shops told me the display itself does not need replacing, just a part on the circuit board. It is a well known problem with this model. Of course the repair techs won't tell me which part needs replacing and I can't find any evidence of a repair. Often you will see cooked flux from the solder surrounding the part that got replaced but they cleaned away any evidence. The last guy that repaired it knows I can solder electronics and can do the repair myself if I can find the part that's fried so he cleaned away the evidence. He was very careful about it too as there is not a telltale scratch anywhere.

I searched the Motorola site for a document detailing the repair but came up empty handed.

Posted by: jsmithepa

Over-Amp, oh I know, but if they used a faulty/un-spec regulator, u would think subsequent repairs they would have replace the item with one of of correct spec/tolerance.

Look for the common ground, or common+ to the display, I would start the tracing there.

If these guys were independent repair shops, I may believe they replaced a single component, but if they were Moto, no way, they just swapped out the module and moved on. Moto can't afford to have them spend time on a single phone.

Posted by: Dagorath

Both previous repairs were done by independent shops, not warranty work by Moto. It's not just my phone that has this problem. All phones of this model have the same problem. It's a well known problem, every cell phone shop here in Calgary knows about it and knows how to repair it. I'm the only one who doesn't know how. I'm not in the cell phone business, btw.

Thanks for the tip but I don't have time to trace it, would be cheaper just to pay a shop. I thought maybe someone here would know exactly which part needs replacing in which case it would only take 5 minutes for me to fix it. But I don't have time to trace and guess and maybe fry the entire board, nope, been there done that before.

A friend has exactly the same model and his display went blank too. Lucky for him it was still on warranty. Moto gave him a new handset the first time, the second time it went blank they replaced the handset with the LCD style handset from the earlier model. Those handsets work well, only problem is they were not backlit so you couldn't see them in the dark. The newer model, with LED, was supposed to be an improvement because they are readable in the dark.

Mine lasted until after warranty expired so I didn't get a free replacement handset. I have been using it without the display but now I have to change service providers because my current provider, Rogers, is dropping analog service. I need the display so I can get it reprogrammed to a new provider. And the only reason I need this damn phone is because with the optional black box I can send/receive fax on it which can't be done on the newer digital signal phones. Otherwise I would just go get a new phone and be done with this piece o' crap bag phone.