[ICOM] Ailing IC-745 - any thoughts?

[Richard Peterson]

Gary, K8IZ, suggested I take a look at the regulator (especially R1) -- and 
I have had just done so. R1 is cooked - completely carbonized.

I have not yet checked the regulated voltage just for the heck of it, 
primarily because I cannot find the fool little regulator board in any of 
the schematics. I have found the parts list, but I have spent a good, honest 
hour trying to find that little board schematic, and I give up.

Does anybody know where that regualtor schematic it is hiden in the shop 
manual? Thanks.

Richard
WB5NEN


>From: "Gary P. Fiber" <gfiber at clearwire.net>
>Reply-To: ICOM Reflector <icom at mailman.qth.net>
>To: ICOM Reflector <icom at mailman.qth.net>
>Subject: Re: [ICOM] Ailing IC-745 - any thoughts?
>Date: Tue, 12 Jun 2007 07:52:46 -0700
>
>Richard,
>
>When ever the IC-745 does strange things check the +8 volt regulator 
>generally its at fault. This regulator is located on a small circuit card 
>attached to the side in the bottom of the radio. Its quite small about 1" 
>by 1" as I remember. Going from my rusty memory R1 on that card likes to 
>change value a lot. Its 1/8 watt as I remember replace it with a higher 
>wattage resistor. I do not believe it was designed as a resistive fuse as 
>they almost never open up. Another problem could be a PA oscillation or an 
>RF unit board problem. Sometimes a transistor like to go into oscillation 
>on the RF unit and will cause this, generally its involved in the receive 
>on the RF unit as I remeber.
>
>A low +8 volts will make the logic do lots of strange things. I once has a 
>caller who told me the radio would only transmit in the memory channels one 
>and two even though all of the memories were programmed correctly, it was 
>the +8 volts DC supply at fault. I doubt seriously it has anything to do 
>with the ram card.
>
>Gary K8IZ

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