Malekko Ekko 616 smoking?!

[Samnunn92]

Hi all,

I'm just getting back in to pedal repair after a long stint of illness and have some pedals I haven't repaired yet. One of them, a Malekko Ekko 616, seems to smoke horribly whenever I insert a lead into the input jack and effectively power the pedal on. It happens whether I'm powering it with a battery or the mains adaptor. I can't find any schematics online and would really like to get this working again would smoking like that indicate theres some sort of short somewhere?

Thanks for any help

Sam

[duck_arse]

screwdriver and meter time. you'll need to test across the circuit board V+ and ground for a short. if you're really lucky, it'll be a reverse protection diode still hanging together with a little more smoke to give.

[R.G.]

Ditto.

If you're really unlucky, you fed it 9Vac and smoked more than the input protection diode.  But the answer is going to be inside.

[Samnunn92]

Thanks both for the reply - so to be clear, I'm looking for anywhere the +ve terminal connects to ground (effectively any point both ground and V+ are continuous?) Sorry for the nooby questions, I've always been a hobby repairer but am attempting to come at it more scientifically this time around! Can't find any suspect diodes at the moment but will continue searching.

Again I really appreciate the help!

[DougH]

A visual check for parts that are burnt and/or smell burnt is a good first step. Then the next step would be yes, checking for continuity between ground and V+.

[duck_arse]

hunt us down, and post a circuit diagram, that will help as well.

[Samnunn92]

Thanks for the replies again, I went back through and checked all the diodes and one had a much lower voltage drop than the others (around 240 on the continuity test compared to 700 for the others.) So I desoldered it and powered the pedal up again - success! No smoke & it now functions perfectly too, except the true bypass section doesn't seem to be working which I assume is as a result of the diode not being in circuit. Would the low voltage drop indicate it's undergone reverse breakdown?

Edit: Also, I'm having real trouble finding a replacement for the diode. Googling the markings doesn't help at all - it looks like it says "1B44" on it, or IB44 or some other permutation. It doesn't match any of the codes I've seen on the internet and I'm pretty stumped. Anyone know what it might be?

[duck_arse]

does your peadl look something like this .... ?



how did you even find the diodes?

[Samnunn92]

That's the one well they are marked on the board as D2 etc, the one I removed is located on the top left hand side of the board in that picture, marked as D5.

[R.G.]

Six trimpots??

AGH!