Zoom g1 doesn’t turn on

Yorkie

Had this connected to a daisy chain power supply. All pedals (before and after this pedal in the chain) working ok, but zoom g1 suddenly turned itself off and now it doesn’t want to turn on. Have tried batteries and another power supply already. Manual is not helpful on this. 

Got another Zoom (505) and that one works OK with the same power supply. 

Any idea how to revive this thing? 

Thanks,
Jon

ICBM

There are two main possibilities -

Physical damage, to the power jack or its connection to the PCB, which will stop it working even on the batteries since the battery current goes via the switch in the power socket. Cracked connections between the power jack and the PCB are by far the most common fault on these. It could also be the ring terminal of the guitar input jack, since that's used to turn the power on.

Or electrical damage which will probably be a shorted protection diode. When it's on batteries, do the batteries get warm/hot if you leave it connected for a while? If so, it's this.

Yorkie

Hi, 
Thanks for your reply. I took it apart and got a couple of shots at the PCB. Could not find anything strikingly wrong. This pedal does not need a jack inserted in INPUT to turn on while it's plugged, so that shouldn't affect. Still need to try the batteries on, but it doesn't look like I'll be able to revive this pedal. Photos:

https://imgur.com/iZ0pREQ
https://imgur.com/HR7HP6W

ICBM

Do you have a multimeter? It should be possible to meter various points in the circuit and probably work out where the fault is.

Likely candidates are the power jack itself - the PCB joints look OK - the protection diode (small black cylinder with silver end, directly below the 'rhythm' button), or one of the filter caps (large black cylinders), if any of these are shorted - or the large grey resistor on the other side being open circuit. If none of those then the voltage regulator (IC3, with the middle of three legs cut short) may have failed.

If it's a total power failure it's most likely to be one of those. Beyond that and you're into small-scale surface-mount parts which are tricky to change anyway, and the larger chips will be unobtainable even if you could identify which one.

There does rapidly come a point where these sort of units aren't worth the effort though, you could buy another one off Ebay for less than a tech would charge for an hour's work. There are a couple there just now, one at £15 with some bids and one with a Buy It Now of £35.

Yorkie

Hi again, 
Sorry - it’s been a busy week. I will have a go at testing the bigger components asap. 

At this point I am not really considering replacing it. I’ve got a couple of modelling amps with similar built-in effects and so this thing had already been benched for a while. I just wanted to see if I could use it as a boost before a Wiretap pedal. While I am using the Wiretap mainly for recording sections, I sometimes do the odd loop for practising. I have now ordered a Blackstar LT Dual, which from what I have seen in the videos can do clean, dirt and everything in between. 

However, I still want to have a proper go at figuring this out. Your messages have no doubt boosted my motivation. 

Thanks,
Jon