expert in crystals? electonic ones !

[simonfraser]

i think i need one of these:
click
for my garage door. Sanwa Crystals 27MHz AM
but what color ??? does it matter ?

many thanks for replies, S

 

[Phoenix of Hamble]

The colour matters..... there are matched pairs of receiver (RX) and transmitter (TX)crystals... you need a pair of reds, or a pair of greens... the RX and TX are slightly different frequencies for each colour pair, but are designed to work together..... you'll need to find out what colour is in the unbroken bit, and get its partner, or replace both.... some systems aren't replaceable, and have 'surface mounted crystals'... only opening it up to check will tell!

They are available from any good model/hobby shop BTW

 

[simonfraser]

many thanks, i'll order and get on with it. i can see them & they are surface mounted.

 

[William_H]

If they are surface mounted you won't be able to replace the crystal.
Well probably not. SMC Surface mount technology is a product of our demands for smaller, the components are placed usually by robot with a touch of glue and a solder paste under the contacts. Infra red heat heats the whole board to melt and solder the components. They are really tiny and almost impossible to replace with a soldering iron. Connections are spaced at about 1mm.
Take a look at your computer boards and you will see SMC.

The crystals you have found for sale are the older technology solder to the board or a socket is used for the crystals. So if yours is a plug in crystal or soldered in of the large size you are OK. The color coding is a system to identify that for a given channel there will be a transmit crystal of the correct frequency and a receive crystal displaced by 455Khz in frequency.

You need to identify the frequency of your transmit crystal (ie 27.096) and match this to the color code. You can see the frequency on the picture of the transmit crystal described.

You will not need or use the receive crystal if you are replacing your transmit crystal.

The reason they have a range of color coded frequencies is for use in radio control (ie aircraft) where every set on one field has to have a different frequency (channel) to avoid interference. Not so important with your garage door controller because they also transmit a peculiar code.

good luck with the repairs.

 

[simonfraser]

many thanks, its def pos to remove and resolder the TX part.
there is also a pot on the board to ??? adjust thre frequency a bit.
i shall go and order some parts.
the garage door co wants 35 squids plus !
and it's interesting

 

[lw395]

How have you deduced it's the crystal? They're pretty robust.

 

[simonfraser]

def, they've been replaced by the garage remote firm at great cost previously!
now i've got one with a broken pin :-(

 

[William_H]

The little pot is probably a variable capacitor used to either set the feedback or tuning of the output coil or to adjust the frequency. Last not likely) I suggest you don't touch it. olewill