[ICOM] R70 issue

[Steve Sutfin]

I appreciate the input Gary. I don't think it's the trimmers either  
and the 13.8v & 8v lines seem to be steady.
The S-meter drops when the fault occurs.
It doesn't loose power, just the signal goes but have background noise.
All controls work normally (which I find odd).
Have tried 12v PS, no difference.
I've thought about an ESR meter before but never got one.
So, aside from caps, which is likely, I'm giving thought to a  
possible mechanical issue.
Time to dive in again.
Steve k7dna


> As other's mentioned I would look at the power supplies in the  
> radio. Generally there is an 8 volt line running through most of  
> the vintage radios, T8 and R8 for TX and RX. Of course the R-70  
> would not have a T8 line. The 8 VDC line may also only be called  
> that. Lots of times when these radio do strange things the 8VDc is  
> in trouble,  low voltage usually. Also as others mentioned since  
> the R-70 is long in the tooth you could have some faulty  
> electrolytic caps through out the power supply or bringing a line  
> like the 8 VDC down. So it is good to give all that a look.
>
> Does the S-Meter still show signals when the fault occurs?
> When it all goes out does the R-70 loose power completely or just  
> signals disappear?
> When the fault appears does the volume control still raise and  
> lower the volume? RF Gain control still appear to be working?,  
> usually moving that will raise or lower the S-Meter
> What do you hear then?
> Have you tried powering it from an external DC Power supply? I will  
> have to down load a schematic diagram can't remember if it had an  
> external DC Input.
>
> Basic test gear is about all that is needed. Most trouble shooting  
> at Icom was done with a DVM. Sure they had other test gear but the  
> DVM seemed to take the first stab at the fault so I would not worry  
> to much yet about your test gear. When messing with possible faulty  
> electrolytic caps an ESR meter is handy. Ask around your local  
> circle of ham radio friends, they are pretty common anymore and you  
> might be able to borrow one if you do not have one. Maybe see if  
> they also have a signal tracer or scope too. Look over the caps for  
> leaking electrolyte or bulged ends but indicators of a faulty cap.
>
> Wish I could lead you to the fault, maybe the questions I asked  
> might spark something in it's operation.
>
> Gary K8IZ
>
> On 10/13/2016 9:37 PM, Steve Sutfin wrote:
>> Hello to the list,
>>  My Icom (aged) R70 receiver started having a problem after xxx  
>> years of good service. When I turn it on sometimes there is no  
>> signal, just the usual background noise. But after a bit it comes  
>> to life like normal but the signal dies after 30 sec. to 3  
>> minutes. The voice doesn't get distorted when it quits but sounds  
>> more like wind blowing across the mic. If left on it comes back  
>> and sounds like normal for a bit then goes out. All voltages I've  
>> traced on the schematic are fine but my test gear is basic.
>> Any thoughts?
>> tnx & 73,
>> Steve k7dna
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>
> ----
> 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/
> To support QSL/QTH.net: http://www.qsl.net/donate.html