OpenBCM V1.06 (Linux)

Packet Radio Mailbox


[C.D.G. OpenBCM]

 Login: GUEST

G8MNY  > TECH     20.02.19 11:30l 138 Lines 6175 Bytes #7 (0) @ WW
BID : 59772_GB7CIP
Subj: IR Remote control failures
Sent: 190220/1012Z @:GB7CIP.#32.GBR.EURO #:59772 [Caterham Surrey GBR]

By G8MNY                                        (Update Sep 12)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

Although universal replacements are available most do not offer the full set of
functions. So you may loose essential buttons like setup, or they may be quite
complex to get that mode out of the universal remote control. Because of this
it is worth while having a good go at a proper repair.

      Case      _     _     _ _Buttons
     Ŀ Ŀ Ŀ Ŀ<Case
 IR  |IR     ===       <Rubber mat with moulded in buttons
Lens |LED=============================== <PCB with its connections
      Components~~[][] ~~~ (_)(_)(_)(_) <Batteries
Each button has a conductive tip (=) that bridges 2 PCB tracks.

One of the main problems is opening a control, some have screws (e.g. in
battery compartment) as well as many hidden catches all the way around that
require top (or bottom) of the case to be bigger, so that the case catches can
be released without breaking them.

  Side view    ~Catch

It is not easy to release all the catches on all sides without marking the case
while levering it, or breaking the odd catch by not levering it in the right

Steve, G1KQH says.. "Sometimes heating the side of the case of the remote with
a hairdryer, makes the plastic more flexible and you can ease, or bend, the
catches off without breaking. DO NOT OVERHEAT!! "

These rubber pad devices often fail due to liquid getting trapped under the
rubber mat. Coffee, Tea, Sweet, will NEVER dry out on its own between the mat &
the PCB. So open it up & carefully remove the PCB (may have screws) & then the
rubber mat (over location points spigots). If is has sold plastic buttons as
well leave them in place! Wash the mat & PCB in hot water, then & thoroughly
dry. This should leave the contacts clean & fully functioning. If there were
separate plastic buttons over the mat, clean them making sure you do not
rearrange them if they have engraved tops. Put back the rubber noting any
alignment points/spigots. Put back the PCB (& any screws).

Before you click back the case if you can test it. This used to be difficult if
there was not a telltale LED on the remote, but nowadays most TV cameras can
see IR to some extent, so it can be easier to hook up a camera to see the
action of all the buttons rather than test with RC main item.

Some locations can stop IR Rx clearly seeing the IR control data. This can be
sunlight on the sensor, or light from some low energy lamps, that may be
operating on simular frequency to the IR pulses, & the low IR emmision just
enough to jam the IR Rx.

These are often wire or thin plate. If a quality unit they may be made of
stainless steel. Often the failure is in the connections, either not enough
pressure or corroded contacts. Too much pressure or dropping can weaken the
spring metal, if to the point of fatigue use added tin can/sponge to extend
contact life. If corroded but still intact then wash parts with hot water &
dry. Grease up the parts (inc battery) to stop all further corrosion. If the
parts are too far gone replace with paper clips/cut tin can etc.
These can be repaired by taking a plastiseen/wax mould of good one, then
cooling it to harden (fridge) & using silicon rubber sealant in the empty
mould, & pressing it into a broken button.
             ___           ___
            | _ |Make     | _ | Fill       _
   /|       | |Mould    |/|Silicon    /
 =      =         =         =
 Broken    Good one      Remold         Repair

When set (24 hours) warming up the mould, so it can be removed. Trim away any
spill with a sharp modelling knife. The Silicon may take a few days to properly
harden to the same strength as the rubber buttons. Paint the button to match
(if you can!)

If the button contact is warn away either on the rubber or PCB sometimes a
repair is possible with special silver conductive paint or even just a "B"
pencil rubbed over the conductive pad & PCB contacts.

From Osvaldo lw1dse
I did this simple tester to check until the IR led itself, and it is very
usefull. Although it has passed a lot of time since I don't repair no more
those apparatus because it's low cost and new ones are easily available, I
send in the expectance some people can use it.

It only uses a JFET/MOSFET operational amplifier as a current to voltage
converter, because the Phototransistor is used without normal bias. This saves
power wasted in the CE junction. In this case, a very high input impedance in
the OPA is mandatory.

This is the circuit:
           100K           IR receiver    
                 (Ĵ>Ŀ diode.     
          ıĴ-\8                  +
                 2  \  7                 9V
          3.9M      \Ŀ           Battery
.1F                   /                  -
                   3  /                  
                    /         (o)Ŀ     
           100K             BNC         
                           To scope      

Also a led can be added with a dropping resistor at the output of the
amplifier, and also a comparator can be used, like a TS393 or TLC372, but it
needs pull up resistors at its output.

Using a 9V  battery, it can be done portable, & a scope can reveal the code.

Why Don't U send an interesting bul?

73 de John G8MNY @ GB7CIP

Read previous mail | Read next mail

 23.02.2019 12:06:46lGo Back Go up