Electronics expert reqd re: pointy tail lights

I`ve opened up my tail light to try and fix the top 3 pairs of LED`s being dim ( K4 naked bike ), but i`m now stuck.
Tried using a solder iron on the joints incase there was dry solder but its made no difference, so I thought i`d upload some pics of the circuit board incase any electronics experts can shed some light on what could be wrong.
The faulty LED`s are supplied from the 2 black wires at the top of the pics. It seems that each pair of LED`s are connected in series with each other but the bottom 4 sets are in paralel with the other 3 bottom pairs, and the top 3 are in parallel with the other 2 pairs, if that makes sense. Also the top 3 sets get their negative supply straight from the earth wire on the bike, but the positive comes from the part of the circuit that supplies the negative to the middle and bottom sets ? The middle and bottom sets get both positive and negative from the electronic circuit.
I`m lost

Edit, theres a couple of black blobs on the circuit board that are just flux, the board isn`t burned.

[Jayneflakes]

Silly question time, but are there any problems with the power supply lines? EG, break in the cable, damage to circuit printing?

Have the LED's burned out or popped due to over loading? A simple replacement could be all you need.

[flymo]

what happens when you press the rear brake pedal? Are they all supposed to glow brighter? Have you measured the voltages at each pair of wires?

p.s., I may have a spare rear light unit if you need.

[ophic]

Early tail light units are known to degrade. The top 3 pairs on mine are also dimmer/more flickery than the rest.

The most likely part of the circuit to degrade would be the capacitor, at a guess. Try sketching out the circuit on paper - it might become clearer.

As jayneflakes has mentioned, it's either a duff component or a bad connection/dry joint.

What's the background to this? Is it safe to assume that the fault persists when applying a known good +12V and 0V to the appropriate pins on the tail light unit's connector?

First thing I would suggest seems to have been done, but I'll say it anyway! Go over all the solder joints, and replace all internal wiring between the circuit boards. If possible I would also cut 10mm or so off the supply wires and re-connect them. Even if there isn't enough wire to cut them back, I would disconnect and re-connect the supply wires to be sure it's a good connection. If that doesn't do the trick, then it's going to be a component. Simplest thing is to remove and test them one by one, on all the boards. Time consuming I know, but often faster than trying to work out what's gone wrong. If you get as far as checking all the components, start with the semiconductors.

Good luck!

The top 3 pairs of LED`s are a lot dimmer then the rest with the sidelights and brake lights, and pulse when the indicators or hazards are switched on. I know this is a common issue with K3 and K4 models, but thought i`d try and find the cause if possible, I mean surely they would not be like that from new ?

I`ve tried the tail light connected to a brand new fully charged car battery and the same thing happens, so its not the bike wiring at fault. And also remelted all the solder on the circuit board incase it was a dry joint, no difference. I pondered connecting the faulty LED`s to the good ones to see if that worked but don`t know if it would do any damage, and for some reason Suzuki have connected them differently.

I think drawing out the circuit and posting a pic would be a good idea, I doubt i`ll be able to spot the obvious failed component as i`m not that brilliant with electronics, but we`ll see.

Originally Posted by flymo

p.s., I may have a spare rear light unit if you need.

What year is it from and how much would you want for it ?

I think 2nd hand here is going to be easier than a repair. You'll need a tidy soldering station, solder sucker and wick to ensure this all goes well. For the price i wouldn't bother.

Re-read original post. Duff LED's are more likely.

[ophic]

Originally Posted by thefallenangel

Re-read original post. Duff LED's are more likely.

Never heard of LEDs going duff, as in, dim. They usually either work or they don't. I was hoping it would get figured out so I could fix mine too

Well either de-solder the LED's and swap with other ones or easier for the price just buy new ones and fit and test. Cheapest way if you got access to soldering equipment otherwise can be expensive. I got a £10 soldering iron and it's crap.