Given the current Loran situation I know this might have come a bit late but thought it worth sharing in case it's of any benefit to others. If it's old news then apologies for that but I've not seen it documented elsewhere. Along with other equipment, the 2100 is known to suffer in the long term from keybounce problems with the front panel tactile switches. A common "cure" is to increase the keybounce time constant on the 74C923 keyboard encoders, the 1uF fitted to the 2100 is quite low and I've found that this can be increased to at least 10uF without adding any additional problems. However, there is likely to come a time when this is no longer an adequate fix and switches can become severely intermittent or even totally open circuit. Replacements are available from Mouser or Digikey, the current manufacturer is E-Switch, but with the numbered key caps not being a stock item I checked my "faulty" switches to see if the caps could be removed and the original numbered caps transferred to new switches. Having found that, with care, the caps can be removed, I also discovered that these switches are mechanically straightforward and physical failure is highly unlikely. Other than the cap itself, the only moving part in the switch is a metal "clicker dome" which when depressed shorts across the contacts formed by the internal ends of the solder pins used for mounting the switch. One of these pins is in the centre of the switch, directly below the centre of the dome, and the other is in one corner with a corner of the dome plate resting on it. I'm not sure what the plating is on these pins but, in my switches anyway, the contact surfaces were heavily tarnished and this was the source of all the problems. Prior to cleaning the contact surfaces were dark brown to black and looked very much like tarnished silver, albeit in this case seemingly non-conducting. This tarnishing also seems to have a knock on effect on the gold plating on the contact surface of the dome so this will need cleaning too. Given that the dome plate has four distinct corners it's easy enough to ensure that a fresh corner is used as this contact. A small drop of isopropyl alcohol with a folded offcut of cartridge or printer paper used for burnishing seems to do a good job of removing the tarnish and polishing the contact areas, I certainly wouldn't recommend anything more severe. After cleaning and reassembly all my switches have a contact resistance of 0.1 Ohms or less and the unit is fully functional again. I could probably now reduce the 10uF debounce capacitors but all is working ok so have left well alone. Practical tips.... It isn't necessary to remove the switches from the circuit board in order to remove the caps but it will need a very fine blade or hook to get in alongside the cap and lever it out. What I used has been in my tool kit for years and I'm not even sure what it is, some kind of sewing implement I think, with a plastic handle and a bent bent end with the bent section around 3/8 inch long, very hard and pointed, and not much thicker than a reasonably fine sewing needle. The black caps of the flat faced switches used on the numeric keypad and for the back light switch have a lug approx 1/8" wide protruding downwards from the centre of each side. These seem to be fairly rugged and careful leverage alongside the lugs should remove the caps without damage. The white caps with a raised tapered section, on the switches along the bottom of the front panel, have only two lugs, top and bottom, and these seem more fragile. I found it best to lever out the top of the cap first, top being defined as when viewed in the panel, having broken the end off a bottom lug when levering one out bottom first, thanks be for superglue:-), but offer no guarantees that what worked for me will be the best solution for anyone else. Given the cost of replacement switches, plus delivery charges, a few hours work has saved me over 50GBP, so again I hope this information may be of benefit to others. Unfortunately though, from this point on, you're on your own, you break it, you fix it:-) Regards Nigel GM8PZR

Good timing. I have just noticed that my 2 button has started acting up. Thanks Paul WB8TSL On Fri, Mar 9, 2012 at 8:48 PM, <GandalfG8@aol.com> wrote: > Given the current Loran situation I know this might have come a bit late > but thought it worth sharing in case it's of any benefit to others. If it's > old news then apologies for that but I've not seen it documented > elsewhere. > > Along with other equipment, the 2100 is known to suffer in the long term > from keybounce problems with the front panel tactile switches. > A common "cure" is to increase the keybounce time constant on the 74C923 > keyboard encoders, the 1uF fitted to the 2100 is quite low and I've found > that this can be increased to at least 10uF without adding any additional > problems. > > However, there is likely to come a time when this is no longer an adequate > fix and switches can become severely intermittent or even totally open > circuit. > > Replacements are available from Mouser or Digikey, the current manufacturer > is E-Switch, but with the numbered key caps not being a stock item I > checked my "faulty" switches to see if the caps could be removed and the > original numbered caps transferred to new switches. > > Having found that, with care, the caps can be removed, I also discovered > that these switches are mechanically straightforward and physical failure > is > highly unlikely. > Other than the cap itself, the only moving part in the switch is a metal > "clicker dome" which when depressed shorts across the contacts formed by > the > internal ends of the solder pins used for mounting the switch. > One of these pins is in the centre of the switch, directly below the centre > of the dome, and the other is in one corner with a corner of the dome > plate resting on it. > I'm not sure what the plating is on these pins but, in my switches anyway, > the contact surfaces were heavily tarnished and this was the source of all > the problems. > Prior to cleaning the contact surfaces were dark brown to black and looked > very much like tarnished silver, albeit in this case seemingly > non-conducting. > This tarnishing also seems to have a knock on effect on the gold plating on > the contact surface of the dome so this will need cleaning too. Given that > the dome plate has four distinct corners it's easy enough to ensure that a > fresh corner is used as this contact. > > A small drop of isopropyl alcohol with a folded offcut of cartridge or > printer paper used for burnishing seems to do a good job of removing the > tarnish and polishing the contact areas, I certainly wouldn't recommend > anything > more severe. > After cleaning and reassembly all my switches have a contact resistance of > 0.1 Ohms or less and the unit is fully functional again. I could probably > now reduce the 10uF debounce capacitors but all is working ok so have left > well alone. > > Practical tips.... > > It isn't necessary to remove the switches from the circuit board in order > to remove the caps but it will need a very fine blade or hook to get in > alongside the cap and lever it out. > > What I used has been in my tool kit for years and I'm not even sure what it > is, some kind of sewing implement I think, with a plastic handle and a > bent bent end with the bent section around 3/8 inch long, very hard and > pointed, and not much thicker than a reasonably fine sewing needle. > > The black caps of the flat faced switches used on the numeric keypad and > for the back light switch have a lug approx 1/8" wide protruding downwards > from the centre of each side. These seem to be fairly rugged and careful > leverage alongside the lugs should remove the caps without damage. > > The white caps with a raised tapered section, on the switches along the > bottom of the front panel, have only two lugs, top and bottom, and these > seem > more fragile. > I found it best to lever out the top of the cap first, top being defined as > when viewed in the panel, having broken the end off a bottom lug when > levering one out bottom first, thanks be for superglue:-), but offer no > guarantees that what worked for me will be the best solution for anyone > else. > > Given the cost of replacement switches, plus delivery charges, a few hours > work has saved me over 50GBP, so again I hope this information may be of > benefit to others. > > Unfortunately though, from this point on, you're on your own, you break it, > you fix it:-) > > Regards > > Nigel > GM8PZR > > > > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >