[ICOM] R70 issue

Sat Oct 15 13:39:25 EDT 2016

Thanks for the input Tony. Voltages seem to be steady so I'm thinking  
caps also. I've often thought about an ESR meter but like so many  
other ideas......
73,
Steve k7dna

On Oct 14, 2016, at 8:38 PM, Tony Hwang wrote:

> Hi, Steve
> IMO, good spot to start is from the audio amp chip, checking output  
> and input side.
> Other electrolytic caps on the audio stage could be bad too. Best  
> way to check a cap. is
> using an ESR meter. Simple one is like ~20.00 on eBay. I picked one  
> of those and
> found out this is a multimeter which can measure L,C,R values as  
> well as ESR.
> Was very handy when I was working on A/C outdoor unit. This thing  
> nailed bad dual run cap.
> very easily. A time saver.
> GL, 73,
> Tony, VE6CGX
>
> Steve Sutfin wrote:
>> Thanks all for the useful (and fast) replies.
>> Christian,
>>  I'm aware of the Icom trimmer cap problems since most of my  
>> research info came up on the R71 & IC751 units. What I found that  
>> seemed consistent with the trimmer caps was no output on certain  
>> bands but not all. When mine goes it's across the board. That  
>> said, it is definitely on my radar.
>> Mort,
>
>>  I get steady 13.8v & 8v on all the connectors I can find so I was  
>> ruling out the PS caps. Now I'm going to keep the various stages  
>> hooked up for a while and check the voltages when the problem occurs.
>> tnx agn everyone,
>> Steve k7dna
>>
>> On Oct 14, 2016, at 9:58 AM, Ron via Icom wrote:
>>
>>>
>>>
>>> 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
>>>> ----
>>>> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net  
>>>> Icom Users
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>>>
>>> ----
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>>
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>>
>
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