K2 Relay contact resistance

[Stewart Baker]

Having decided to join the melee trying to work 3Y0X on Peter One Island, I
dusted off my FT1000MP. The only time that I use it are on occasions such as
this when a separate receiver is useful when working split.

I noticed that the receive sensitivity was varying on 20 & 40m, and traced this
to the HPF board at the front of the receiver. This board contains 8 miniature
relays which do the filter switching. If I tapped the board the received signal
strength varied. From notes I found on the web this is a known problem where the
solution is to change all 8 relays. I didn't fancy changing these small relays
if there was a better solution.

I remembered that the FT102 had big problems with people were changing relays by
the bucket full. Yaesu don't seemed to have learned the lesson of the FT102 !
A local amateur came up with a fix which consisted of running a small DC current
through the contacts to break down any oxide layer that had formed over time.

This morning I modified the HPF board to run about 1mA through the contacts.
10 resistors and 2 caps later - End of problem - Fixed....

The big relays in the KAT100 should not have a problem, but what about the
smaller ones in the K2, KAT2 ? As far a I can tell a number of these have only
very small AC signals passing through them. None have any DC current flow.

It took about 7 years before the problem surfaced with my FT1000MP, I would be
interested in comments on whether in the same time scale I might expect to get
similar problems with my Elecraft gear.

73
Stewart G3RXQ
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[Don Wilhelm-3]

Stewart,

All I can say is that K2 SN 00020 is working fine after 5 years with no
relay problems, and in all the K2s that I have worked on, I have found only
one relay failure.

Relay contact failure can also be prevented by using relays that possess
wiping contacts.  I know not how much wiping action exists on the latching
relays used in the K2, but they are speced by the manufacturer (Omron G6H
relay data sheet) for 100 million operations with 50 milliohms maximum
contact resistance.  The contacts are gold plated silver and I would believe
they should not normally need cleaning by means of a DC bias.

Perhaps another couple years on the K2 will give a comparison with the
experience with your MP1000 - only time will tell the true tale.

73,
Don W3FPR

> -----Original Message-----
> ...
> This morning I modified the HPF board to run about 1mA through
> the contacts.
> 10 resistors and 2 caps later - End of problem - Fixed....
>
> The big relays in the KAT100 should not have a problem, but what
> about the
> smaller ones in the K2, KAT2 ? As far a I can tell a number of
> these have only
> very small AC signals passing through them. None have any DC current flow.
>
> It took about 7 years before the problem surfaced with my
> FT1000MP, I would be
> interested in comments on whether in the same time scale I might
> expect to get
> similar problems with my Elecraft gear.
>
> 73
> Stewart G3RXQ
>

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[Stewart Baker]

Don,

Thanks for your prompt reply. I think that the problem (if there is one) will
only show up after a number of years. Maybe 7 years is the magic figure.
It also will depend to a great extent on the quality of manufacture, cleanliness
etc. I had a look at the Omron G6H data sheet.

The 100 million operations are the mechanical service life. For the electrical
service life you must look under the Characteristic Data.
Unfortunately the electrical service life curves only show 2 graphs.
One for a 30VDC and one for a 125VAC, both into a resistive load.
There is no definitive data presented for when there is no current flow.

Like you, I am not sure if these small relays have a wiping action.
Perhaps there is a relay expert on the reflector ?
Otherwise as you say - only time will tell the true tale.

73
Stewart G3RXQ

On Sun, 12 Feb 2006 08:15:24 -0500, Don Wilhelm wrote:

> Stewart,
>
> All I can say is that K2 SN 00020 is working fine after 5 years with no
> relay problems, and in all the K2s that I have worked on, I have found only
> one relay failure.
>
> Relay contact failure can also be prevented by using relays that possess
> wiping contacts.  I know not how much wiping action exists on the latching
> relays used in the K2, but they are speced by the manufacturer (Omron G6H
> relay data sheet) for 100 million operations with 50 milliohms maximum
> contact resistance.  The contacts are gold plated silver and I would believe
> they should not normally need cleaning by means of a DC bias.
>
> Perhaps another couple years on the K2 will give a comparison with the
> experience with your MP1000 - only time will tell the true tale.
>
> 73,
> Don W3FPR
>
>
>> -----Original Message-----
>> ...
>> This morning I modified the HPF board to run about 1mA through
>> the contacts.
>> 10 resistors and 2 caps later - End of problem - Fixed....
>>
>> The big relays in the KAT100 should not have a problem, but what
>> about the
>> smaller ones in the K2, KAT2 ? As far a I can tell a number of
>> these have only
>> very small AC signals passing through them. None have any DC current flow.
>>
>> It took about 7 years before the problem surfaced with my
>> FT1000MP, I would be
>> interested in comments on whether in the same time scale I might
>> expect to get
>> similar problems with my Elecraft gear.
>>
>> 73
>> Stewart G3RXQ

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[Ken Wagner K3IU]

Entering into an area where I know little, the following from the Omron web
site

        http://www.omron.com/ecb/products/pry/111/g6h.html

Found under
"Characteristics
Endurance Mechanical:   100,000,000 operations min. (at 36,000
operations/hr)
                Electrical: 200,000 operations min. (at 1,800
operations/hr) "

Not sure whether this relates to the discussion or not...
73,
Ken K3IU

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Stewart Baker
Sent: Sunday, February 12, 2006 10:11 AM
To: Don Wilhelm; Elecraft Reflector
Subject: RE: [Elecraft] K2 Relay contact resistance

Don,

Thanks for your prompt reply. I think that the problem (if there is one)
will only show up after a number of years. Maybe 7 years is the magic
figure.
It also will depend to a great extent on the quality of manufacture,
cleanliness etc. I had a look at the Omron G6H data sheet.

The 100 million operations are the mechanical service life. For the
electrical service life you must look under the Characteristic Data.
Unfortunately the electrical service life curves only show 2 graphs.
One for a 30VDC and one for a 125VAC, both into a resistive load.
There is no definitive data presented for when there is no current flow.

Like you, I am not sure if these small relays have a wiping action.
Perhaps there is a relay expert on the reflector ?
Otherwise as you say - only time will tell the true tale.

73
Stewart G3RXQ

On Sun, 12 Feb 2006 08:15:24 -0500, Don Wilhelm wrote:

> Stewart,
>
> All I can say is that K2 SN 00020 is working fine after 5 years with
> no relay problems, and in all the K2s that I have worked on, I have
> found only one relay failure.
>
> Relay contact failure can also be prevented by using relays that
> possess wiping contacts.  I know not how much wiping action exists on
> the latching relays used in the K2, but they are speced by the
> manufacturer (Omron G6H relay data sheet) for 100 million operations
> with 50 milliohms maximum contact resistance.  The contacts are gold
> plated silver and I would believe they should not normally need cleaning

by means of a DC bias.

>
> Perhaps another couple years on the K2 will give a comparison with the
> experience with your MP1000 - only time will tell the true tale.
>
> 73,
> Don W3FPR
>
>
>> -----Original Message-----
>> ...
>> This morning I modified the HPF board to run about 1mA through the
>> contacts.
>> 10 resistors and 2 caps later - End of problem - Fixed....
>>
>> The big relays in the KAT100 should not have a problem, but what
>> about the smaller ones in the K2, KAT2 ? As far a I can tell a number
>> of these have only very small AC signals passing through them. None
>> have any DC current flow.
>>
>> It took about 7 years before the problem surfaced with my FT1000MP, I
>> would be interested in comments on whether in the same time scale I
>> might expect to get similar problems with my Elecraft gear.
>>
>> 73
>> Stewart G3RXQ

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[n6wg]

Hi Stewart
I have K2 s/n 12 in pretty constant use here, particularly in contests.
So far as I can tell, I have no problem with the relays, either in the
basic K2 or in the KAT2.
Good luck and 73
Bob N6WG
Teh Little Station with Attitude

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Stewart Baker
Sent: Sunday, February 12, 2006 4:24 AM
To: Elecraft Reflector
Subject: [Elecraft] K2 Relay contact resistance


Having decided to join the melee trying to work 3Y0X on Peter One Island, I
dusted off my FT1000MP. The only time that I use it are on occasions such as
this when a separate receiver is useful when working split.

I noticed that the receive sensitivity was varying on 20 & 40m, and traced
this
to the HPF board at the front of the receiver. This board contains 8
miniature
relays which do the filter switching. If I tapped the board the received
signal
strength varied. From notes I found on the web this is a known problem where
the
solution is to change all 8 relays. I didn't fancy changing these small
relays
if there was a better solution.

I remembered that the FT102 had big problems with people were changing
relays by
the bucket full. Yaesu don't seemed to have learned the lesson of the FT102
!
A local amateur came up with a fix which consisted of running a small DC
current
through the contacts to break down any oxide layer that had formed over
time.

This morning I modified the HPF board to run about 1mA through the contacts.
10 resistors and 2 caps later - End of problem - Fixed....

The big relays in the KAT100 should not have a problem, but what about the
smaller ones in the K2, KAT2 ? As far a I can tell a number of these have
only
very small AC signals passing through them. None have any DC current flow.

It took about 7 years before the problem surfaced with my FT1000MP, I would
be
interested in comments on whether in the same time scale I might expect to
get
similar problems with my Elecraft gear.

73
Stewart G3RXQ
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[wayne burdick]

Stewart,

The small relays we use all have wiping action. This was one of our
selection criteria. We also ran them through millions of switching
cycles just to be sure, and not a single one failed, which bodes well
for relay life in our products. Gary, our customer support engineer,
has noted that relay failures in the field are also extremely rare, and
in most cases can be traced to damage during initial installation
(e.g., melting a corner of the package with a soldering iron).

Even if a relay did develop a problem, you should only replace that
relay, not an entire group. All of our manuals include signal-tracing
procedures that should be helpful in identifying a failing relay. In
the case of our internal ATUs, you can exercise each relay individually
using the rig's ATU menu entry. The T1 allows individual relay testing
using its switch/LED user interface.

If you ever do have to replace a relay, it's wise to remove *all* of
the solder using a large (not wimpy!) vacuum desoldering tool, followed
by solder-wicking all pins to clean things up. Even still, you might
have to pry a bit with a jeweler's driver to get the relay off.

Since all of our PC boards are double-sided, there's a small risk of
pulling out the plating on one or two plated-through holes when you do
this. But we anticipated this, so we make all PC board connections to
relays on the opposite side of the board. The loss of through-plating
is then a non-problem. We apply this rule to all large components that
obscure their top-side traces. The rule is harder to follow in dense
areas around ICs, but in this case you can solder the pins both top and
bottom if plating is lost.

We also strive to maximize the size of PC board pads and traces
whenever possible. This simplifies possible rework, lowers trace
impedance and improves reliability. Our PC layout methodology is in
sharp contrast to most of the electronics industry, which seems to use
the smallest trace widths they can get away with, even when PCB
real-estate isn't an issue.

73,
Wayne
N6KR

-----

www.elecraft.com

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[N2EY]

In a message dated 2/12/06 12:07:24 PM Eastern Standard Time,
[hidden email] writes:


> K2 s/n 12 in pretty constant use here, particularly in contests.
> So far as I can tell, I have no problem with the relays, either in the
> basic K2 or in the KAT2.
>

Perhaps that 'pretty constant use' is the key.

IIRC, the original poster said he "dusted off his '1000MP". Which means it
has probably been sitting around idle for a long time.

Wiping action only works if the relays actually cycle once in a while.

73 de Jim, N2EY
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[Nick Waterman]

Ken K3IU wrote:
> Electrical: 200,000 operations min. (at 1,800 operations/hr)

Eeek. I was intending to set up some software to monitor IBP beacon
frequencies for 3mins each. 1 band change every 3 minutes, 5 beacons to
get through, call it 2 operations every 15 minutes for each relay
involved, so admittedly "only" 8 operations/hr not 1,800, but that still
gets me 200,000/8 = 25000 hours, that's about 3 years life expectancy,
or admittedly "min" life expectancy...

Better hope I manage something closer to Wayne's "millions of switching
cycles"  :-/

--
"Nosey" Nick Waterman, G7RZQ, K2 #5209.
use Std::Disclaimer;    [hidden email]
The only thing worse than raining cats and dogs is hailing taxis.
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[Stewart Baker]

Wayne,

Thank you for your very comprehensive reply.

The FT1000MP gets switched on about once a month, and I tend to switch between
bands and functions. This is not an excessive idle time, and I think that if
decent relays were fitted there would be no problem. All relays are not created
equal, and I have my doubts about those that were fitted to my FT1000MP.

The  wiping action of relay contacts certainly makes as big difference, and I am
pleased that the Omron ones selected do that.

My experience of Elecraft PCB's is that their construction is really robust, and
providing care is taken when removing components no tracks or plated through
holes should be damaged. Despite removing/replacing components in a number of
areas, I have yet to lift a track.

Your mail has really put my mind at rest, and I will continue to enjoy my
Elecraft gear with no worries.

73
Stewart G3RXQ

On Sun, 12 Feb 2006 10:16:23 -0800, wayne burdick wrote:

> Stewart,
>
> The small relays we use all have wiping action. This was one of our
> selection criteria. We also ran them through millions of switching
> cycles just to be sure, and not a single one failed, which bodes well
> for relay life in our products. Gary, our customer support engineer,
> has noted that relay failures in the field are also extremely rare, and
> in most cases can be traced to damage during initial installation
> (e.g., melting a corner of the package with a soldering iron).
>
> Even if a relay did develop a problem, you should only replace that
> relay, not an entire group. All of our manuals include signal-tracing
> procedures that should be helpful in identifying a failing relay. In
> the case of our internal ATUs, you can exercise each relay individually
> using the rig's ATU menu entry. The T1 allows individual relay testing
> using its switch/LED user interface.
>
> If you ever do have to replace a relay, it's wise to remove *all* of
> the solder using a large (not wimpy!) vacuum desoldering tool, followed
> by solder-wicking all pins to clean things up. Even still, you might
> have to pry a bit with a jeweler's driver to get the relay off.
>
> Since all of our PC boards are double-sided, there's a small risk of
> pulling out the plating on one or two plated-through holes when you do
> this. But we anticipated this, so we make all PC board connections to
> relays on the opposite side of the board. The loss of through-plating
> is then a non-problem. We apply this rule to all large components that
> obscure their top-side traces. The rule is harder to follow in dense
> areas around ICs, but in this case you can solder the pins both top and
> bottom if plating is lost.
>
> We also strive to maximize the size of PC board pads and traces
> whenever possible. This simplifies possible rework, lowers trace
> impedance and improves reliability. Our PC layout methodology is in
> sharp contrast to most of the electronics industry, which seems to use
> the smallest trace widths they can get away with, even when PCB
> real-estate isn't an issue.
>
> 73,
> Wayne
> N6KR
>
> -----
>
> www.elecraft.com

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[Dan Barker]

That was 200,000 with (memory check?) 1A on the contacts. You need to use
the mechanical numbers, since the current is << 1A.

Dan / WG4S / K2 #2456

<snip>
> Electrical: 200,000 operations min. (at 1,800 operations/hr)
</snip>

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