Cleaning relay contacts


Mike GD6ICR
 

Been going through my sma relays and testing them on my primitive spectrum analyser has shown that I have quite a few lossy relay on TX as high as 4dB and quite a few showing around 1dB on RX side. I wonder if anyone can suggest a suitable contact cleaning method - one suggestion Ive had is connect 12v thru 500ohm resistors to NO and NC and leave them switching for about 5 minutes

Some of the relays of coarse can be dismantled and cleaned but most cannot - any comments please
--
Mike GD6ICR IO74PF73TW


Andy G4JNT
 

I cured a few of mine by just operating them a few times



On Sun, 28 Mar 2021 at 16:56, Mike GD6ICR <gd6icr@...> wrote:
Been going through my sma relays and testing them on my primitive spectrum analyser has shown that I have quite a few lossy relay on TX as high as 4dB and quite a few showing around 1dB on RX side. I wonder if anyone can suggest a suitable contact cleaning method - one suggestion Ive had is connect 12v thru 500ohm resistors to NO and NC and leave them switching for about 5 minutes

Some of the relays of coarse can be dismantled and cleaned but most cannot - any comments please
--
Mike GD6ICR IO74PF73TW


Dave - G4RQI
 

Hello

Unless someone says otherwise you might try this http://www.dl6nci.de/sma.htm

David - G4RQI


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Mike GD6ICR <gd6icr@...>
Sent: Sunday, March 28, 2021 4:56:02 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: [UKMicrowaves] Cleaning relay contacts
 
Been going through my sma relays and testing them on my primitive spectrum analyser has shown that I have quite a few lossy relay on TX as high as 4dB and quite a few showing around 1dB on RX side. I wonder if anyone can suggest a suitable contact cleaning method - one suggestion Ive had is connect 12v thru 500ohm resistors to NO and NC and leave them switching for about 5 minutes

Some of the relays of coarse can be dismantled and cleaned but most cannot - any comments please
--
Mike GD6ICR IO74PF73TW


Mark GM4ISM
 

Mike

Hot switching a small  DC current  really does work in many cases.

 You generate micro-arcs at the contact surface  which disrupt the  oxide layer and promote  a lower contact resistance

 Some system designs  allow a few 10ms of mA DC to switch alongside the RF  in service to whet  the contact at each switching event

I used to use special very slightly abrasive paper pulled between contacts on old (large) PO relays It was routine maintenance but even that  did damage the contact surface and it  was a constant battle

Mechanical  'cleaning' of delicate contact surfaces as in most RF relays is a recipe for disaster.

Mark GM4ISM

 

On 28/03/2021 16:56, Mike GD6ICR wrote:
Been going through my sma relays and testing them on my primitive spectrum analyser has shown that I have quite a few lossy relay on TX as high as 4dB and quite a few showing around 1dB on RX side. I wonder if anyone can suggest a suitable contact cleaning method - one suggestion Ive had is connect 12v thru 500ohm resistors to NO and NC and leave them switching for about 5 minutes

Some of the relays of coarse can be dismantled and cleaned but most cannot - any comments please
--
Mike GD6ICR IO74PF73TW

Virus-free. www.avg.com


Mike GD6ICR
 

Thanks Mark Im aiming in the switching DC on the contacts as per http://www.dl6nci.de/sma.htm Thanks to Dave RQI for this - its really good design especially 24/12v relays

Circuit building tomorrow
 

--
Mike GD6ICR IO74PF73TW


John Fell
 

Clamp gently in a vice onto the lid and whack the base with a small lump of wood - should break the epoxy seal and allow cover to come off .
Contacts can be seen and if appropriate cleaned with a contact strip - do not file !
Test results on a SAnn.
DC Wetting is useful , mainly on the RX contacts that are often NC for long periods and develop surface resistance .

73
JOhn
G0API

On Sun, 28 Mar 2021 at 16:56, Mike GD6ICR <gd6icr@...> wrote:
Been going through my sma relays and testing them on my primitive spectrum analyser has shown that I have quite a few lossy relay on TX as high as 4dB and quite a few showing around 1dB on RX side. I wonder if anyone can suggest a suitable contact cleaning method - one suggestion Ive had is connect 12v thru 500ohm resistors to NO and NC and leave them switching for about 5 minutes

Some of the relays of coarse can be dismantled and cleaned but most cannot - any comments please
--
Mike GD6ICR IO74PF73TW


Alan Melia
 

Mark beat me to it :-(( I was getting a number of Pye/Philips M290 relays going HR on receive contacts in the 1990s. This was not a coax relay but switching a few milliamps several times returned the receive sensitivity without needing to replace the relay (an RS stock item). I believe it was a BT method in the days of Strowger.

Alan
G3NYK


Andy G4JNT
 

I see an intelligent relay rejuvenation project in this.   Swap over the contacts repeatedly, with a constant current driven though each.   Monitor the voltage drop after each change to a make position and report the findings.



On Sun, 28 Mar 2021 at 19:42, Alan Melia via groups.io <Alan.Melia=btinternet.com@groups.io> wrote:
Mark beat me to it :-((  I was getting a number of Pye/Philips M290 relays going HR on receive contacts in the 1990s. This was not a coax relay but switching a few milliamps several times returned the receive sensitivity without needing to replace the relay (an RS stock item).   I believe it was a BT method in the days of Strowger.

Alan
G3NYK






Chris G8BKE
 

On a slightly related subject has anyone found a long lasting way to clean "contactless" key pads on things like TV remote controls which seem to rely on a resistive / capacitive button  to come into contact with a printed "electrode" on the pcb. Despite these being gold plated they seem to need frequent cleaning with IPA to ensure correct operation. I've lost count of the number of times I've had to open mine up to clean said contacts only to have them fail again a few weeks later.

73


Stefan
 


Hi Chris
 
it is the button that is the problem, not the PCB, the minute carbon deposits wears off. You can buy pure silverpaint that has a hydrocarbon glue,
specially made to repair tracks and keyboard buttons.
Alternative if you want to go cheap use super glue and aluminium kitchen foil and adhere it to the button.
 
VK4CSD Stefan 73

----- Original Message -----
Sent: Monday, March 29, 2021 7:02 PM
Subject: Re: [UKMicrowaves] Cleaning relay contacts

On a slightly related subject has anyone found a long lasting way to clean "contactless" key pads on things like TV remote controls which seem to rely on a resistive / capacitive button  to come into contact with a printed "electrode" on the pcb. Despite these being gold plated they seem to need frequent cleaning with IPA to ensure correct operation. I've lost count of the number of times I've had to open mine up to clean said contacts only to have them fail again a few weeks later.

73


Chris G8BKE
 

How come cleaning the button clears the problem for a while then?

73


Stefan
 


dont know, maybe there is a minute build up of oxides or similar non contactive layer build up. I seen  it throughout all of those keyboard type button, test gear sufferes equally, my HP8563e is getting worse and worse and will need previous mentioned treatment.
 
Good Luck 73

----- Original Message -----
Sent: Tuesday, March 30, 2021 7:37 AM
Subject: Re: [UKMicrowaves] Cleaning relay contacts

How come cleaning the button clears the problem for a while then?

73


Stanislaw Ziemczonek
 

On a slightly related subject has anyone found a long lasting way to clean "contactless" key pads on things like TV remote controls which seem to rely on a resistive / capacitive button  to come into contact with a printed "electrode" on the pcb. Despite these being gold plated they seem to need frequent cleaning with IPA to ensure correct operation. I've lost count of the number of times I've had to open mine up to clean said contacts only to have them fail again a few weeks later.


Oguzhan Kayhan
 

I think I have a similar problem ..
Using some "used" relays on my VHF PA
one sma relay for low power side (driving 30-40w), and a qro relay for PA output (up to 1200W) .
Both are old relays..
I dont have any problems with TX side, some little warm up only on qro side.

But on receive, I am experiencing something strange..
If I don't tx for a few mins, I can see there is a 2-3 dB dropdown on my rx signal
Sometimes if I just PTT without any power applied, but mostly after txing a few seconds, RX level goes up again.

Does the symptoms fit? 


On Tue, Mar 30, 2021 at 10:07 AM Stanislaw Ziemczonek <sp6gwb@...> wrote:
On a slightly related subject has anyone found a long lasting way to clean "contactless" key pads on things like TV remote controls which seem to rely on a resistive / capacitive button  to come into contact with a printed "electrode" on the pcb. Despite these being gold plated they seem to need frequent cleaning with IPA to ensure correct operation. I've lost count of the number of times I've had to open mine up to clean said contacts only to have them fail again a few weeks later.


--
73
de TA2NC


Bob Lockley VK6KW
 

From my observation and limited experience it appears to be leakage of the plasticiser as the flexible membrane ages and some of its components denature. The “gooey mess” (a technical term) is often difficult to remove and in doing so the conductive surface on the underside of the keys also suffers – sometimes applying a light coat of graphite from a 2B or other ‘soft’ pencil on these ‘contacts’ will work. In the case of remote controls, a replacement “programmable, universal” remote is the optimum solution.

73,

Bob VK6KW.

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of Stefan
Sent: Tuesday, March 30, 2021 6:26 AM
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Cleaning relay contacts

 

dont know, maybe there is a minute build up of oxides or similar non contactive layer build up. I seen  it throughout all of those keyboard type button, test gear sufferes equally, my HP8563e is getting worse and worse and will need previous mentioned treatment.

 

Good Luck 73

----- Original Message -----

Sent: Tuesday, March 30, 2021 7:37 AM

Subject: Re: [UKMicrowaves] Cleaning relay contacts

 

How come cleaning the button clears the problem for a while then?

73


Stefan
 


Thanks Bob
 
for your explanation. I remember doing the soft pencil application once and it did work better for a short term, but using the adhesive silver paint seems a permanent fix
 
73 Stefan VK4CSD

----- Original Message -----
Sent: Wednesday, March 31, 2021 12:08 PM
Subject: Re: [UKMicrowaves] Cleaning relay contacts

From my observation and limited experience it appears to be leakage of the plasticiser as the flexible membrane ages and some of its components denature. The “gooey mess” (a technical term) is often difficult to remove and in doing so the conductive surface on the underside of the keys also suffers – sometimes applying a light coat of graphite from a 2B or other ‘soft’ pencil on these ‘contacts’ will work. In the case of remote controls, a replacement “programmable, universal” remote is the optimum solution.

73,

Bob VK6KW.

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of Stefan
Sent: Tuesday, March 30, 2021 6:26 AM
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Cleaning relay contacts

 

dont know, maybe there is a minute build up of oxides or similar non contactive layer build up. I seen  it throughout all of those keyboard type button, test gear sufferes equally, my HP8563e is getting worse and worse and will need previous mentioned treatment.

 

Good Luck 73

----- Original Message -----

From: Chris G8BKE

Sent: Tuesday, March 30, 2021 7:37 AM

Subject: Re: [UKMicrowaves] Cleaning relay contacts

 

How come cleaning the button clears the problem for a while then?

73