Alesis echo unit - Does not turn on

musicalstash

Can anyone help identify the fault with a Alesis q20 rack unit  which refuses to turn on .


Was working fine this morning with no issues , then got home plugged it but now no signs of life at all - no hum etc. 

Did not hear any bang or anything so not too sure what it is .

I have opened the top to see if there is anything obvious but cant see anything - there is what looks like  fuse under the circuit board  could this be the issue or maybe the battery ? 

https://ibb.co/rm7GPX8
https://ibb.co/MPDzpJ6

I have tried removing the plastic cover to access the board but the white plastic has what looks like a tag of some sort which runs through the plastic into the board . 

any help would be appreciated 

ICBM

It will be the fuse if it's either of them. Get the fuse out and see if it's blown - if it's badly burned the chances are there's some other fault and it's the result not the cause. If it's cleanly broken it could just be an old fuse that failed due to vibration over the years. If it has failed due to some other fault I would guess a shorted electrolytic cap is probably the most likely - they degrade and eventually fail with age.

Danny1969

Leave the battery alone, if you disconnect that it will lose all the stored patches and you might have something valuable stored like Echos of the past or your own patches. 

Try the fuse and change if blown but if the new one blows then don't try a 2nd as there's obviously a fault which will probably need a tech as these things are a mix of thru and SM components, plus the way they have wired the rear outs make the board a pain to get in and out. 

musicalstash

Thanks will order a new fuse and see what happens... It has the eprom with the charlie hall presets installed, if I change the battery will it affect the patches.? 

There is a piece of white plastic with a battery change date (2017)  on top of the board but has been connected through with some sort of clip so unable to access the screws . Is it Can I swap the fuse with the board in place?

https://ibb.co/QC8MT62

https://ibb.co/pjGSrkC

Danny1969

musicalstash said:

Thanks will order a new fuse and see what happens... It has the eprom with the charlie hall presets installed, if I change the battery will it affect the patches.? 

There is a piece of white plastic with a battery change date (2017)  on top of the board but has been connected through with some sort of clip so unable to access the screws . Is it Can I swap the fuse with the board in place?

https://ibb.co/QC8MT62

https://ibb.co/pjGSrkC

Yes you will lose the EOTP patches. You have to hot change the battery to avoid losing them as the midi dump is disabled to protect Charlies work. From memory the fuse is a 2A  but I can't remember where it is and can't access your photos at the mo . 

musicalstash

Thanks . Was able to access the fuse but it looks OK, is there more than one ( this was next to the plug socket) 

Fuse 2A 250vc 5x20mm F - is this a slow or quick .

From the services manual it says Fuse 2A 250vc 5x20mm F fuse ( is this slow or quick blow?) but says  holders so guessing maybe more than one.

https://ibb.co/RDjZKLh

https://ibb.co/BzXc70r

musicalstash

I checked the fuse with  a multmeter and the continuity reads 008   so guessing it must be something else. Gutted as I have not idea what could have happened , used it for the last few days with no issues .. 

ICBM

Hopefully this is a stupid question, but have you checked the power cable?

If so, and it's not even humming quietly when on, that indicates power not getting to the transformer. If it's not the fuse, that really just leaves a broken connection or a faulty power switch as the other possible causes - unless the transformer itself has died (open circuit - a short would blow the fuse), but that's extremely unlikely.

Since you have a meter, check resistance across the switch contacts in the on position - with the unit unplugged from the wall of course!

musicalstash

Thanks , yes I have tried a couple of cables and the same issue ( they work with other units).  does a reading of 008 on the fuse rule that out as being the issue . Will try in the morning to see if I can get board out to reach the switch 

ICBM

musicalstash said:

Thanks , yes I have tried a couple of cables and the same issue ( they work with other units).  does a reading of 008 on the fuse rule that out as being the issue . Will try in the morning to see if I can get board out to reach the switch 

It should be 000, but the meter probably has a significant zero error. If the fuse was blown it would show an open circuit.

Looking at your first pic again, I think that fuse may actually be on the secondary side of the transformer - it's too large a value to be the primary fuse, and the rest of the circuitry around it looks more like a low-voltage supply... I think the bridge rectifier is under the 'QP TST 1' stamp. In which case there may be another fuse, probably closer to the power switch.

musicalstash

Thanks - is this the fuse? Can't see any other glass ones. 

https://ibb.co/c60cG29

Danny1969

No that's an inductor  ... I worked on one of these units a few months ago. I'll see if I've got photos on my phone, I normally take a few of every job for reference 

Danny1969

I only have photos of the main PCB but I found the PSU by using the PN from the service manual .. 9-79-B401



See that white JTS header on the bottom left. That should have ground, +15V and - 15V for the audio and 5V for the digital  ... work back from there because if those voltages aren't present then it's pointless looking at anything else. The fault will be on that PSU 

ICBM

Ah, so new enough to have a SMPS. Ignore what I said above about transformer hum and the fuse being for a low-voltage power supply then.