Re: Cleaning TM500 module pushbutton switches

Glenn Little

Ensure that you remove all traces of the WD40.
WD40 is a water displacer.
It will leave a gummy mess.


On 7/10/2020 11:30 AM, Renée wrote:
I have the same issue only with the plastic on plastic ( the actuator for finger poking to the to the outside world) is causing the sticking. they were cleaned with soap and water ( yes disassembled) to remove dirt and then ipa without success. suggestions?
I have used WD40 to soften grease for easier removal. leave it sit for a day or two, sometimes multiple applications...I try not to make it too messy.
thanks for the procedure, some things I had not considered, very helpful!

On 7/10/20 7:42 AM, Nenad Filipovic wrote:
On Fri, Jul 10, 2020 at 3:05 AM W1PJE <@W1PJE> wrote:
I have multiple TM500 modules that have developed sticky / intermittent
pushbutton switches (the square small ones). Is there a recommended cleaning procedure? I was going to do the standard use of Caig's DeOxit in a sparing manner, but perhaps there is a better way.
In some cases hard patina forms on contact surfaces and DeOxit can be ineffective or just a short term solution. Additionally, DeOxit cannot restore the original grease which is likely fully decomposed and dry due to age. In that case I use the following procedure to restore these without any desoldering: - Gain access, carefully uncouple and remove the pushbutton shaft. - Remove the clamp next to the spring, carefully remove the tiny parts (spring, tiny rocker bolt and its elastic support). - Carefully pull out the switch shaft at the back of the switch body - care must be taken to go slow and grip the two metal contacts (use tweezers) before they fully come out (otherwise they may fly off and get lost). Note (or take photo of) the orientation of contacts with respect to their slot in the shaft (the bend in the middle should be oriented away from the switch body). - If the switch is radio button type it will contain a "clutch" sliding plate that needs to be pushed to one side so the shaft could be released and removed. - Sometimes a PCB component may get in the way of shaft removal, I almost always find it easier to remove the offending component rather than the switch body. - If switch parts are clogged by ancient dried up grease, clean/wash everything (both plastic and metal parts) with a paintbrush in petroleum benzine (pharmaceutical grade, in Europe we get it in regular pharmacies; however most non-polar solvents which are not aggressive to plastic would do). Do not let the plastic parts sit in benzine for too long, all this can and should be done in just a few minutes. Let the clean parts dry. - Using a soft brass brush (I get these at dentist supply shops) gently scrub the patina off the active side of the metal contacts. Soft brass brush should not damage the contact plating that needs to be preserved. - Use cotton ear buds soaked first in petroleum benzine, then IPA to clean the internals of the switch body. I spend at least two sticks per switch. - Grease all sliding surfaces of parts sparingly (innards of the switch body, shaft, contacts, rocker bolt pathway in the shaft) with plastic safe light grease. The goal of contact greasing is protection from moisture and oxygen that may re-deposit the patina again in time. Light grease won't interfere with low current low voltage electrical contact properties. - Re-assemble and exercise the switch. HTH, Best regards, Nenad  .

Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

Join to automatically receive all group messages.