[ICOM] IC775DSP display backlight problem

[Juan Pablo Mercé LU4DX]

Hi Anders,

I am going to try with this the next time that open the rig to install the 
optional filters and the INRAD roofing filter.
I expect to be able to find the problem.
I have my IC-775DSP a few days behind and already love it, it is excellent.
Thank you very much for the advice, also to Bob and Jim.

73's Paul LU4DX



----- Original Message ----- 
From: "Anders Janis SM4RNA" <sm4rna at telia.com>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Sunday, June 18, 2006 8:15 AM
Subject: Re: [ICOM] IC775DSP display backlight problem


> Check Q19 on the main board that i gets the "low"-signal and that the 
> transistor it self is ok.
>
> If that works you can try this to find out if Q16 is ok.When enabeling 
> "low"-light you sould see that the voltage is dropping at the emitter of 
> Q16.
>
> To get to the main board there is a lot of work and a lot of cables to 
> disconect. If you are not used to work with complex radios, get help from 
> someone that is.
>
> GL
>
> /Anders
>
>
> ----- Original Message ----- 
> From: "Juan Pablo Mercé LU4DX" <lu4dx at hotmail.com>
> To: "ICOM Reflector" <icom at mailman.qth.net>
> Sent: Sunday, June 18, 2006 2:39 AM
> Subject: Re: [ICOM] IC775DSP display backlight problem
>
>
>>I have a problem related to the display in my IC-775DSP.
>> This one works well and without intermittences but I cannot change the 
>> intensity of the display, try to change the value to LO and HI into the 
>> menu but nothing happens like the preset to change the low intensity.
>> The level seems to be in the high position.
>> The previous owner said to me that the display backlight was intermittent 
>> and he resoldered the lamp's power transformer secondary contacts to the 
>> printed circuit board.
>> Does someone know where the problem can be not to be able to change the 
>> intensity of the display?
>>
>> Tnx in advance,
>>
>> Paul LU4DX
>>
>> ----- Original Message ----- 
>> From: "Martin Sole" <msole at loxinfo.co.th>
>> To: <icom at mailman.qth.net>
>> Sent: Saturday, June 17, 2006 5:12 AM
>> Subject: [ICOM] IC775DSP display backlight problem
>>
>>
>>> Dear Icom friends,
>>>
>>> I have a problem with an IC775DSP display that I would appreciate some 
>>> assistance with. The owner noticed the backlight flicker a couple of 
>>> times then go out. This was accompanied by a burning smell and some 
>>> smoke. Investigation shows that both Q17 & Q18 in the backlight driver 
>>> circuit have disintegrated.
>>>
>>> I would first like to know what kind of voltage the backlight is meant 
>>> to be driven with? The schematic shows it to be simply an LED driven 
>>> from a rather complicated AC source. I therefore assume that the 
>>> backlight needs more than just a few volts at a few mA.
>>>
>>> My second question concerns the voltage source itself. This appears to 
>>> be some sort of oscillator driven from the 14 volt line but I am 
>>> unfamiliar with the nature of its design. I did replace the damaged 
>>> transistors with similar items albeit 100 volt rated rather than 120 
>>> volt rated but they immediately self destructed so I assume I need to 
>>> look elsewhere for the cause.
>>>
>>>
>>> I can email scans of the circuit area if anybody would like to see 
>>> before passing comment.
>>>
>>> Thanks in advance for any help.
>>>
>>> Martin HS0ZED
>>> ----
>>> Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
>>> Icom Users Net: Sundays, 1700Z, 14.316 MHz
>>> Icom FAQ: http://www.qsl.net/icom/
>>>
>> ----
>> Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
>> Icom Users Net: Sundays, 1700Z, 14.316 MHz
>> Icom FAQ: http://www.qsl.net/icom/
>
> ----
> Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
>