[ICOM] R70 issue

[bonddaleena at aol.com]

Hi. Better caps are those rated at 105 C....

ron
N4UE


-----Original Message-----
From: f1gwr <f1gwr at free.fr>
To: ICOM Reflector <icom at mailman.qth.net>
Sent: Fri, Oct 14, 2016 2:43 am
Subject: Re: [ICOM] R70 issue

Hi,

Mort may be right.

But one common issue is the VCO capacitors. Not only the electrolytics but also the trim caps. Thanks Icom they didn't give out the value of these caps, only unknown references, uh! If I remember well they should all be replaced by 10 or 12 pF. After realigning the VCO after the Service Manual, this solves the problem. There are a lot of references about this problem on the net, but found one that states one of the lower value trim cap (around 6 pF) must be replaced by a larger value than initially for best results.  I read that if you replace all caps by 10-12 pF, you still have lowest cap value to obtain PLL capture over the full range.
HTH.

Best 73
Christian F1GWR

Le 14 oct. 2016 à 07:09, "Mort Arditti" <marditti at dslextreme.com> a écrit :

> Steve,
> 
> The R70 is a senior citizen.
> 
> One possible issue may be electrolytic capacitors causing DC voltage
> problems.  These devices 'dry up' with time which causes 
> capacity loss and high leakage.  If you have the means to check the various
> DC voltages and ripple.  This will require an 
> oscilloscope.  The power supply has large such capacitors.  Sometime as
> capacitors age, you may see some bulging and/or
> some build up on the positive end wire lead near the seal.  This is a sign
> of bad capacitor.
> If the voltages are proper and minimal ripple (guess at <50 mV peak to
> peak), it is not the capacitors.  On the other hand if the 
> much higher start replacing electrolytic capacitors.
> 
> If indeed it is capacitor issue, replace them all.  Observe proper polarity
> - this is very critical.
> 
> For long reliable life make that the capacitor are rated for 85 Deg. C and
> low ESR.
> 
> I hope this helps.
> 
> 73,
> 
> Mort,  NA6MA
> 
> 
> -----Original Message-----
> From: Icom [mailto:icom-bounces at mailman.qth.net] On Behalf Of Steve Sutfin
> Sent: Thursday, October 13, 2016 9:38 PM
> To: ICOM Reflector
> Subject: [ICOM] R70 issue
> 
> 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
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To support QSL/QTH.net: http://www.qsl.net/donate.html