IC-756PRO No Audio at start up.

[Jamie]

I bought a used 756 Pro in mint shape, recently it has
developed a problem that i have already seen in 2 other
friends ICOMS 756 which they sent out under warranty to
have repaired. from what i understand its a bad solder joint
some where in the audio circuit (most like the Amp) that is cracked
and heels it self when the rig warms up .
Well now i own one of those, i am going to repair this my self
and thought maybe some one else may have already located the
faulty area so that it will save me some time finding it.

thanks.

 

[GS]

Congrats on getting ready to repair this yourself Jamie - THAT......is
the stuff that REAL HAM RADIO is made of! Although you might indeed
find someone who'll give you a "silver bullet" (actual quick fix), I'd
highly recommend just digging out the schematic AND circuit board layout
drawings and troubleshooting this logically. Although I don't have
those drawings myself, if you do and would like to share them (just the
sections applicable) I'd be glad to help/guide you with the
troubleshooting and repair.

73 - Gord VE1AJF

 

[Christian Treldal]

Den Thu, 10 Mar 2005 12:26:45 -0800. skrev Jamie:

I bought a used 756 Pro in mint shape, recently it has
developed a problem that i have already seen in 2 other
friends ICOMS 756 which they sent out under warranty to
have repaired. from what i understand its a bad solder joint
some where in the audio circuit (most like the Amp) that is cracked
and heels it self when the rig warms up .
Well now i own one of those, i am going to repair this my self
and thought maybe some one else may have already located the
faulty area so that it will save me some time finding it.

You can find the servicemanual here:

http://mods.dk/view.php?ListManuals=icom

Gentle tap with the plastic end of a small screwdriver at the components
in af section might help you.

Audio amp ic's are good at unsolder themselves, especially in mobile units.

Happy hunting

Vy 73's de oz1gnn

Christian Treldal

 

[Jamie]

Congrats on getting ready to repair this yourself Jamie - THAT......is
the stuff that REAL HAM RADIO is made of! Although you might indeed
find someone who'll give you a "silver bullet" (actual quick fix), I'd
highly recommend just digging out the schematic AND circuit board layout
drawings and troubleshooting this logically. Although I don't have
those drawings myself, if you do and would like to share them (just the
sections applicable) I'd be glad to help/guide you with the
troubleshooting and repair.

73 - Gord VE1AJF

yeah ok, i have been doing some research and apparrently its the relay
that deactives the specker while the unit is initiating.
i haven't taken the rig apart yet because its not totally dead! since
i have the accessory being used for Slow scan i still can hear it fine
in the computer speakers!
but in any case, i have determine that hte relay coil must be getting
partial current and maybe even noisy current (bad joint), but do not
notice it due to the fact that relays have a Peek and Hold current! once
the relay gets enough to latch down, the holding current can reduce and
not effect the unit.
so this looks like a solder joint in the circuit that is operating the
relay, most likely a transistor that runs hot or the relay runs hot and
does not have enought heating venting between the relay body board which
is causing the board to heat contract to much and thus forming bond
problems in the joints of the coil legs.
etc..
i will get to it one of those days