I am very grateful to all who answered my question about the "faulty" relays. As the answers are of general interest, and not all were copied to Moon-Net, I have attached them. Many thanks David, g4YTL Betreff: Re: [Moon-net] CX600 relay problem Von: TexasRF-at-aol.com Datum: Thu, 12 Aug 2004 17:42:37 EDT An: david.hilton-jones-at-clinical-neurology.oxford.ac.uk Hi Dave, I wish I had a dollar for every relay seen with your described problem. All of the ones in use at my station show this condition if they have not been operated recently. In fact, the computer software I use for EME operation has a special hot key that triggers the ptt line about 50 times in quick succession to help clean up the relay contacts. It is my understanding that oxides form on the relay contacts due to exposure to atmosphere and they cause a resistive film to develop. I also understand that the real "fix" for this is to make sure a small current of a few ma can flow through the contacts when they are operated. I have never done this so no first hand input on this issue. I have been told that silver oxide is a good conductor so it makes some sense to silver plate relay contacts. Again, Ihave never done this so no first hand data here either. I do make cold sky to 50ohm load noise ratio tests frequently enough that I know when a relay is giving trouble. The 50 pulse ptt trick so far has taken care of the problem but on occasion I have to do that three or four times. I would be interested in knowing about any really good solutions to this problem. Tnx/73 de Gerald/K5GW Betreff: Re: [Moon-net] CX600 relay problem Von: w2drz Datum: Thu, 12 Aug 2004 17:47:53 -0400 An: David Hilton-Jones CC: moon-net-at-list-serv.davidv.net Hi David, Not having any of that type relay would think the problem is the contacts do not wipe as the close, would think them to be silver contacts and as such be of a non contaminated contact device.. As normal silver will stay low resistance as they oxidize in the atmosphere.. but there are other contaminates (such as do you smoke or have home heating using fossil fuels) that will cause the type of problem observed in your case if the contacts do not wipe in the closure motion under low power operation.. If you have a relay burnishing tool (relay special cleaning tool) that will clean the contacts, NO FILE OR SAND PAPER!!! Also a clean piece or writing paper, "of a non glossy surface" between contacts, when switched closed several times being pulled through the contacts each time closed, will clean with no damage to the contacts is a other way to clean the contacts, in the "USA" I have use our paper money (a dollar bill) to do the same cleaning in a pinch/emergency of nether items at hand to use.. best tom >> David Hilton-Jones wrote: >> >> I have recently had experience of two CX600 relays with the same type >> of contact problem, and wonder if anybody else has seen the same? >> >> Both relays had been used in relatively low power situations. One had >> been properly sequenced, I'm not sure about the other. On both the >> problem was with the NC contact. DC resistance was 2-3 ohms, but very >> unstable. SWR was high and again unstable - so gently tapping the >> relay would have a marked effect on the resistance/SWR. The NO >> contacts were fine when the relay was energised. >> >> The contacts look OK to the naked eye, as does the plunger mechanism. >> >> Thanks for your thoughts. >> >> 73 >> >> David, G4YTL >> >> --------------------------------------------------------------- >> _______________________________________________ >> Moon-Net posting and subscription instructions are at >> http://www.nlsa.com/nets/moon-net-help.html -- http://www.w2drz.ramcoinc.com/index.htm http://www.downeastmicrowave.com/ best 73 tom W2DRZ FN02LA FCC # PG-20-2479 what we do: work: http://www.ramcoinc.com/index.php http://www.amtronix.com/ fun: Lat 42.02.27n Long 079.04.01w 12 digit grid FN02LA19XT22 EME on 1296 / 23 cm 6M WAS #505, VUCC 6M #857,2M #166,220 #21,432 #86,902 #29,1296 #38,2.3 #60,10 GHz #105 Betreff: Re: [Moon-net] CX600 relay problem Von: ERICKE6RCI-at-aol.com Datum: Thu, 12 Aug 2004 18:15:17 EDT An: david.hilton-jones-at-clinical-neurology.oxford.ac.uk Run a piece of rough paper between the contacts. The resistance should definitely be zero ohms. Eric/ke6rci Betreff: RE: [Moon-net] CX600 relay problem Von: "Russ Pillsbury" Datum: Thu, 12 Aug 2004 19:52:08 -0400 An: "David Hilton-Jones" CC: Hello David & Tom. David I guess Tom forgot about the problems we went through at his QTH with those relays (I'm pretty sure they are the CX600 ones). We ran into the exact problem you are describing and also another issue. The 'other issue' was that none of the relays we had, had their coil wires soldered to the contacts on the shell on the inside! The wires were wrapped tightly around the contacts but never soldered. Of course that is easily fixed. The contact resistance problem was not one of cleaning contacts, but of an hour of very careful adjustments to the parts to bend things 'just so' so that the relays made reliable contact both energized and open. I was able to get them to be reliable but it was difficult. Hope this helps, 73, Russ K2TXB >> -----Original Message----- >> From: moon-net-bounces-at-list-serv.davidv.net >> [mailto:moon-net-bounces-at-list-serv.davidv.net]On Behalf Of w2drz >> Sent: Thursday, August 12, 2004 5:48 PM >> To: David Hilton-Jones >> Cc: moon-net-at-list-serv.davidv.net >> Subject: Re: [Moon-net] CX600 relay problem >> >> >> Hi David, >> >> Not having any of that type relay would think the problem is the >> contacts do not wipe as the close, would think them to be silver >> contacts and as such be of a non contaminated contact device.. >> As normal silver will stay low resistance as they oxidize in the >> atmosphere.. >> but there are other contaminates (such as do you smoke or have home >> heating using fossil fuels) that will cause the type of problem observed >> in your case if the contacts do not wipe in the closure motion under low >> power operation.. >> >> If you have a relay burnishing tool (relay special cleaning tool) that >> will clean the contacts, NO FILE OR SAND PAPER!!! >> >> Also a clean piece or writing paper, >> "of a non glossy surface" >> >> between contacts, >> >> when switched closed several times being pulled through the contacts >> each time closed, >> >> will clean with no damage to the contacts is a other way to clean the >> contacts, in the "USA" I have use our paper money (a dollar bill) to do >> the same cleaning in a pinch/emergency of nether items at hand to use.. >> >> best tom >> >> > >>> > David Hilton-Jones wrote: >>> > >>> > I have recently had experience of two CX600 relays with the same type >>> > of contact problem, and wonder if anybody else has seen the same? >>> > >>> > Both relays had been used in relatively low power situations. One had >>> > been properly sequenced, I'm not sure about the other. On both the >>> > problem was with the NC contact. DC resistance was 2-3 ohms, but very >>> > unstable. SWR was high and again unstable - so gently tapping the >>> > relay would have a marked effect on the resistance/SWR. The NO >>> > contacts were fine when the relay was energised. >>> > >>> > The contacts look OK to the naked eye, as does the plunger mechanism. >>> > >>> > Thanks for your thoughts. >>> > >>> > 73 >>> > >>> > David, G4YTL >>> > >>> > --------------------------------------------------------------- >>> > _______________________________________________ >>> > Moon-Net posting and subscription instructions are at >>> > http://www.nlsa.com/nets/moon-net-help.html > >> >> -- >> >> http://www.w2drz.ramcoinc.com/index.htm >> >> http://www.downeastmicrowave.com/ >> >> best 73 tom W2DRZ FN02LA FCC # PG-20-2479 what we do: >> work: http://www.ramcoinc.com/index.php >> http://www.amtronix.com/ >> fun: >> Lat 42.02.27n Long 079.04.01w >> 12 digit grid FN02LA19XT22 EME on 1296 / 23 cm >> 6M WAS #505, VUCC 6M #857,2M #166,220 #21,432 #86,902 #29,1296 >> #38,2.3 #60,10 GHz #105 >> _______________________________________________ >> Moon-Net posting and subscription instructions are at http://www.nlsa.com/nets/moon-net-help.html Betreff: Re: [Moon-net] CX600 relay problem Von: Chris Bartram Datum: Fri, 13 Aug 2004 00:21:55 +0100 An: moon-net-at-list-serv.davidv.net Hello David When relays handle power, thin films of corrosion which inevitably form on the contacts are broken down by the currents that flow through them. That's not true of relays that only carry small signals, where the corrosion can easily cause exactly the problems you're experiencing. There are metal contact systems which avoid this problem, although without getting-out my copy of 'Modern Relay Technology' I can't remember the details. The other solution is to allow a mA or two of DC to flow through the contacts: this is know as 'DC Whetting', and is often used where relay intermods. are important. My solution isn't to use relays like the CX600, but instead to go for decent professional relays like those manufactured by Transco, RLC, and the like The Russian REW15 (75ohm) and REW14 (50ohm) relays available on the Net for about £15ea., also seem fine from this viewpoint, and will handle 'lotsa watts' to >432MHz. I'm now on 432/1296MHz tropo, and heard you with a good signal during the 432 Activity Contest. I was a bit shy of transmitting as I had an audio problem - which I've since located and cured. I was on 432MS during the Perseids, and worked OK1DFC (1460ish km) and SM3AKW at 1786km. The QSO with Karl, 'AKW, seems to be a new UK 432MS record. Sorry Conrad!! I was particularly pleased to work Karl, as we ran about a dozen 6hr 432MS skeds in the late 70s/early 80s. A sked with SM2CEW at nearly 2200km didn't go, but the time wasn't really right. Another with Tom DL7UAE in JO62 failed because FSK441 seems not to like the doppler and spreading inherent in 432MS. We'd have made a QSO on HSCW... 73 Chris GW4DGU On Thursday 12 August 2004 21:43, David Hilton-Jones wrote: >> I have recently had experience of two CX600 relays with the same type of >> contact problem, and wonder if anybody else has seen the same? >> >> Both relays had been used in relatively low power situations. One had >> been properly sequenced, I'm not sure about the other. On both the >> problem was with the NC contact. DC resistance was 2-3 ohms, but very >> unstable. SWR was high and again unstable - so gently tapping the relay >> would have a marked effect on the resistance/SWR. The NO contacts were >> fine when the relay was energised. >> >> The contacts look OK to the naked eye, as does the plunger mechanism. >> >> Thanks for your thoughts. >> >> 73 >> >> David, G4YTL -- Christopher Bartram MIEE Christopher Bartram RF Design Blaenffos Pen-y-Bont CARMARTHEN SA33 6QG 01994 419600 e-mail: chris-at-chris-bartram.co.uk URL: http://www.christopherbartramrfdesign.com _______________________________________________ Moon-Net posting and subscription instructions are at http://www.nlsa.com/nets/moon-net-help.html Betreff: Re: [Moon-net] CX600 relay problem Von: Art Datum: Thu, 12 Aug 2004 21:32:56 -0400 An: "David Hilton-Jones" I had a similar problem many years ago, and asked an OT about it. It was a t-r relay for my novice station, a surplus 48v dc coil unit. He brought over his burnishing tool, the first time I'd ever seen such a device. It fixed the problem for a few qso's, but it was never right. Finally, he advised me to drive the relay to turn it on and to reverse the polarization when I wanted to turn if off. This always leaves the coil energized, so it's not for everyone:>: But, it did work. Even if the CX-600 has a mechanical stop, driving it to open and to close should keep the contact surfaces clean because the relay slams from the NC to the NO position and visa versa, instead of being allowed to 'coast' by just removing the coil voltage. I'm not sure currently manufactured relays with dc coils will work with this scheme. A desirable side effect of this will be faster switching as the relay is actually driven off instead of having the power removed and having it passively fall back. I think there is some chatter about this in the 50's to 60's Handbooks where the faster turn off time is used for keyers of that era (vacuum tubes driving old technology clunky relays), relays needed to be heavy duty to carry the higher voltages and currents used in transmitter keying in those days. Art At 04:43 PM 8/12/04, you wrote: > I have recently had experience of two CX600 relays with the same type of contact problem, and wonder if anybody else has seen the same? > > Both relays had been used in relatively low power situations. One had been properly sequenced, I'm not sure about the other. On both the problem was with the NC contact. DC resistance was 2-3 ohms, but very unstable. SWR was high and again unstable - so gently tapping the relay would have a marked effect on the resistance/SWR. The NO contacts were fine when the relay was energised. > > The contacts look OK to the naked eye, as does the plunger mechanism. > > Thanks for your thoughts. > > 73 > > David, G4YTL > _______________________________________________ > Moon-Net posting and subscription instructions are at http://www.nlsa.com/nets/moon-net-help.html Betreff: Re: [Moon-net] CX600 relay problem Von: "David Tanner" Datum: Fri, 13 Aug 2004 20:03:48 +1000 An: While we are on the subject of CX600N relays, I suspect that both the NC and NO connectors are only a tight press fit into the body of the relay as on one occasion I had the connector separate itself from the body, do not put any strain on them otherwise you will not have any contact at all. Also, they are only rated at about 600 watts on 144 mhz, although I had no trouble at about three times that power in days gone by. David VK3AUU. _______________________________________________ Moon-Net posting and subscription instructions are at http://www.nlsa.com/nets/moon-net-help.html Betreff: RE: [Moon-net] CX600 relay problem Von: Leif Asbrink Datum: Fri, 13 Aug 2004 13:44:31 +0200 An: "David Hilton-Jones" Hi Dave and all, >> I have recently had experience of two CX600 relays with the >> same type of contact problem, and wonder if anybody else has >> seen the same? >> Both relays had been used in relatively low power situations. >> One had been properly sequenced, I'm not sure about the other. >> On both the problem was with the NC contact. DC resistance >> was 2-3 ohms, but very unstable. SWR was high and again >> unstable - so gently tapping the relay would have a marked >> effect on the resistance/SWR. The NO contacts were fine when >> the relay was energised. >> >> The contacts look OK to the naked eye, as does the plunger mechanism. I was using six of these relays on my 4x14 x-yagi array and I have had the same problem with the NC contact. The relay was the one nearest to the antenna which was used to swich between Rx and Tx. It was connected in parallel with the DC supply to the preamp and the NC contact was used for transmit. (The Rx input was protected when the entire station was switched off). Under normal operation the contact problem was invisible, but since I used a PIN diode switch in the Tx line to line to listen between dots and dashes (full QSK) I noted that the receiver (through the PIN diode) was dead when I switched over to tx mode until I pressed the key once. After that everything was normal until I went over to Rx and back to Tx again. I was operating like this for quite some time and the open circuit through the NC contact was always sucessfully repaired by the first key-down. I took down the antenna and opened the relay. Only with magnifying glass I could see a dark spot on the gold pin of the center contact. I cleaned it with a strip of paper (the type one filters coffe through) and I did not do any adjustment at all. The relay served fine after that for several years until the antenna was destroyed in a storm. My faulty relay had a much larger contact resistance than a few ohms. The rx was literally dead - at least 20 dB below normal. I do not remember. It seems to me that these relays use a very thin gold coating and that they therefore are designed to have no "scratching" at all. The contacts separate by lifting at 90 degrees directly. The contact pressure is small and it is essential that the surfaces are very clean. 73 Leif / SM5BSZ