DX-390 - blank LCD.

[ruchitel]

High everybody.

I bought DX-390 in thrift store. On checking it at home - radio works (can hear stations in FM and AM), but LCD is completely blank, no signs of life. Is is realistically fixable at home? Anybody run into the same problem before and has any leads?

 

[TAC4]

No, that radio would be for advance electronics training. It's
a chip base micro processor radio not fixable for the "do it
your self". Looking at the block diagram in the service manual
IC403 is the microprocessor and part of its job is the LCD
screen.

So that chip would be suspect along with the ribbon cable to
the LCD screen if it has a cable. All the voltages around that
chip would have to pass before condemning the chip and
even then there is no guarantee it's the chip at fault.

Getting that chip out and putting a new one in would very hard
without damage. I think the chips are still available on
eBay but not sure. Here is what that chip looks like.
The pins would be a nightmare to solder also there
could be other ICs in that block diagram that can
also be faculty. I checked the net and nothing came up
for a simple fix. If it has a factory reset button you can try
that also.

My advice is the radio is not worth fixing.

 

[ruchitel]

Thanks for response. Logically thinking, since that micro controls many things besides LCD - buzzer, buttons, etc - end all of these functions work, I assume microprocessor is good. It may have a blown out lines that drive LCD, but unless some bug crawled in and shorted those selectively - it's highly unlikely, LCD uses very little current to be driven. Also, LCD may have dedicated power source and that could have been blown too. Unfortunately, I could not find anything that lists LCD in more details than monolithic bloc.

 

[Boombox]

I've heard of ribbons going bad on some radios, the CCRadios had this issue for a while. My DX-370 has an partly faulty LCD readout that probably needs the ribbon resoldered. I've also read somewhere where a guy resoldered a faulty LCD ribbon on a radio (don't recall which radio), but it wasn't with an iron. There's some other way they reform the solder. Some sort of heated air source used for surface mount electronics? I just can't remember how it was done.

I wouldn't junk the radio, though, especially if it works OK. On MW it's fairly easy to count the channels while tuning the band. Just use the up and down buttons. Same could be said for the SWBC bands as well. It would be like DXing in the blind, but it could be done. The DX-390 is pretty good for SW and MW (although in my location MW needs an external loop, because I live in a hole).

 

[KD9KSO]

It's called 'reflowing'. It's normally done with heat ir hot air.

 

[TAC4]

Looks like pins 1-15 on IC403 is the for the LCD segments.
I would start there and see if you have any voltage activity
on those pins when you rotate the tuning dial. Wrap a thin
piece of buss wire around your test prob so you can get
at the tiny pins without shorting them out.

If you do have voltage activity next see if you have voltage
activity at the base pins at the LCD screen it self.

I still don't think the radio is worth fixing but that is just me.
Also when you go thrift radio shopping bring your own variable
power adapter with the accessory plugs noting the center
tip polarity, that way you can try stuff out before buying
so you don't hosed.