Originally Posted by mneary

The "transistors" are SCRs', if it matters.

Well, I certainly am feeling guilty for not looking up the datasheet. In his first post he called them transistors and I made an ass-umption without bothering to look them up.

I am not good at looking at photographs and reverse engineering, only the "obvious" things. I see that line voltage is being rectified here for the control circuit, but I would be curious to know if the voltage the devices are switching is AC or DC.

If the SCRs are rectifying when they switch it might be a problem.

And if he jumpers them, well who knows if the circuit will operate properly or draw an acceptable current. I wouldn't want to guess.

Was just trying to help and made wrong assumptions. I hope he reads this before potentially destroying his lights.

karlb123,

Sorry I didn't post this earlier on TUES - I meant to, but forgot as I burned the midnight oil out late night.

What kind of control chip (IC) is mounted on that 2008L (803) mini PC thru board that drives the gates of those 4 switched (UTC?) PCR406J SCR's?

You really need to post another pix of the component side of the PCB only from the opposite direction.

I would have thought that the mfr would have given you that Strobed option on the PCB, but I see it's only an ON/OFF only scheme with the switch on the GRD side. Kinda weird, but I guess it saves on the micro-switch contacts arcing! I guess if you wanting just straight ON/OFF LED lights then you would just buy them that way.

Shorting out an SCR, or any similar device is NOT highly recommended at all. It only results in SMOKE & FIRE!!

Those PCR406J SCR's btw follow from left to right K-A K-A K-A K-A. Not sure what the J designation is for, but my guess is that it has something to with European standards possibly??

Hope to see another pix from the other side of that 2008L (803) mini PC thru board.

Frank

Sorry to be a killjoy, but modifying this unit is not a good idea unless you like risking fire and shock. In theory, such a mod could work, but the unit is already dangerous.

I've got a couple of these LED chains with flasher control units off eBay, and they're all unsafe. Similar ones have been banned in the EU and recalled, mainly because they are a fire and electric shock hazard. Definitely don't leave them unattended, and keep children, pets, and anything flammable (e.g. your house) away from them.

The wires attached to the contacts have too small a cross-section (0.11mm²) for carrying mains (the two contacts at the left of the pic above) or a measured 208V DC, which is the maximum output on each of the 4 lines (the one on the extreme right of the picture is the common line). The same type of wire is used for both mains and DC feeds.

The wire also has no resistance to being stretched and broken, so you can end up with live wires pulled out of the flasher if a child or pet treads on the mains lead. Cable strain relief is provided by glueing the wires into the flasher control box, but one gentle pull broke the mains wire outside the box, and left live strands easily accessible.

I replaced the mains lead with proper 2-core mains flex for safety, so I could test it. The feeds to the led chains (25 LEDs per chain) are PWM - the power is rapidly switched off and on, being left on for a longer period when the LEDs need to appear at their brightest. Bypassing the switching PCR406s will only add to the risk of shock, so I'd recommend chucking the flasher unit into a dustbin. Keep the LEDs for another project (with a lower voltage feed - not mains).

You would be better off going to a reputable high-street seller, paying a few quid extra, and getting a non-flashing set of lights which you can use for several years without injuring anyone or starting a fire.

Hope this helps.