[ICOM] R70 issue

[Richard Bown]

Hi
I'm in the middle of ripping an old 211E apart to replace the VFO
 I dont know if the R70 used a similar LSI chip in the synth, its possible due to similar vintage.
But a problem I saw was the one of the programmable dividers inside the LSI chip would play silly
S***s , possibly temperature related, but it would go miles off frequency, still staying in lock.
power cycling sometimes got it back on frequency.
It would produce the same symptoms you are seeing, a frequency counter on the VCO o/p would show
this up.

hope this is of some help


On Sat, 15 Oct 2016 10:52:12 -0700
Steve Sutfin <stephoto at mind.net> wrote:

> 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
> >> ----
> >> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> >> Icom Users Net: Sundays, 1700Z, 14.316 MHz
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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  
> 
> ----
> 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



-- 
-- 
Best wishes /73 
Richard Bown

Email : richard at g8jvm.com
HTTP  :  http://www.g8jvm.com
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