[ICOM] Ailing IC-745 - any thoughts?

[Gary P. Fiber]

Richard,

I am sure the print of the REG UNIT appears on the print. I seem to 
remember its names as I wrote in caps too. Probably on the logic board 
side of the print.
Generally Icom used to outline small boards like that in a dashed 
square. Most of the time only that resistor goes bad. Seems to me its 
something like 4.8 ohms but do read the print when you find it there. I 
certainly would up the wattage on it to a 1/4 or 1/2 watt.. I think its 
an 1/8 watt now. The REG UNIT outputs +8 VDC. I don't remember any other 
odd voltages coming from it.

Gary K8IZ

Richard Peterson wrote:
> 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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