X10 European Lamp Module (LM12 etc)

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Although I live in Australia, I will head this request as "European" since  
the X10 modules sold in Australia appear to be the same as those in Europe  
/ UK (Marmitek, etc) except with the standard Australian / NZ plug / socket
 arrangement. So, I have had a couple of these which have died on me, and I
 am trying very hard to repair them as I still have a very good application
 for using them. Having dismantled the modules and checked the associated c
ircuit board, I can see that most of the circuit appears to be similar in d
esign to that widely published on the Internet by SM Bloom for the 110v lam
p module with obvious changes to take account of the higher supply voltages
 in European countries (220v through 250v). However, there is one area of t
he circuit that leaves me perplexed. In the 110v circuit, the 120Khz 'contr
ol' signals are fed to pin 1 of the associated 78561 microcontroller via a  
variable coil and what appears to be a couple of clamping diodes and a 33pF
 series capacitor.  

However, on the European models, the associated circuitry is much more comp
lex. The 120KHz signals are again fed to pin 1 of the 78561 via a variable  
coil but then via a much more complex circuit consisting of two extra trans
istors as well as a number of associated capacitors and diodes. I have trac
ed the circuit and there are certainly some anomalies! The first transistor
 used is marked C705 and a 'net search shows this as a small signal RF NPN  
transistor. However, the references to this show a nonstandard pin configur
ation (ECB rather than EBC)) which certainly does not appear to be the case
 on the one I have removed from a PCB. I am 99% certain that the one used h
as a standard EBC configuration. The second transistor is marked C623 which
 seems to be the same as others on the PCB. I have a sketch of how I believ
e the circuit is laid out, based on the best of my ability and without dest
ructively unsoldering too much (The tight layout makes this a difficult tas
k, to say the least!). My question is, does anyone have ANY knowledge of wh
at the purpose of this extra circuitry is and how it works? I am happy to s
hare my sketch if there is anyone out there that might be able to answer me
!

Oh, and my fault-finding so far seems to indicate that the major problem is
 a breakdown of the initial 0.33uF 630v polyester capacitor that is used in
 place of the "large blue" 0.68uF capacitor on the 110v modules.

Many thanks in advance for any assistance - there is precious little inform
ation available on 'true' European voltage modules.

Re: X10 European Lamp Module (LM12 etc)
    miweaver@gmail.com writes:
Quoted text here. Click to load it

If that capacitor short circuited, I suspect it will have blown
all the low voltage circuitry, unless a zener diode held on for
long enough to blow the resistor in series with the capacitor
(which you can test with a test meter, although it's often
obvious when they blow).

If it just went open circuit, then you should be able to simply
replace it. Use a Class X1 or X2 capacitor to reduce chance of
it shorting (these are designed specifically to have mains
voltage across them and remain safe).

Quoted text here. Click to load it

--  
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Re: X10 European Lamp Module (LM12 etc)
Andrew Gabiel replied: - If it just went open circuit, then you should be a
ble to simply replace it. Use a Class X1 or X2 capacitor to reduce chance o
f it shorting (these are designed specifically to have mains voltage across
 them and remain safe).  

Thanks Andrew. Somewhat independently, I had already decided that might be  
a better solution. It's also easier as the 'main' electronics retailers her
e don't stock a decent range of HV mylar capacitors, but do keep a range of
 X2 mains caps. (I've ordered some fom overseas, but they do take a while t
o reach here. We'e a long way from anywhere!) It doesn't - thankfully - loo
k like it went s/c - it actually measures 0.113uF rather than 0.33uF, so ho
pefully it won't have destroyed anything beyond it. I'm keeping fingers cro
ssed!

Re: X10 European Lamp Module (LM12 etc)
Quoted text here. Click to load it

That means the dropper LV supply will only be able to supply 1/3rd of
the original current to the LV circuitry, and it's unlikely it was
originally over-spec'ed by a factor of 3, so that very likely explains
why the circuitry wouldn't work.

--  
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

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