Alesis 3630 for beginner

[AcdNrg]

So I´ve done a fair number of Eurorack DIY projects and now want to get deeper into electronics. A friend of mine has a faulty 3630 which he gave to me. I´m looking for a point to get started, so maybe this behaviour rings a bell:

- Power supply appears to be ok, LEDs lights up
- And that´s the problem: Almost all LEDs light up, with nothing except power plugged in. It seems a strong signal is generated somewhere and it´s on both channels.
- Unit is constantly compressing, unless bypassed
- Gate function appears to work
- Link function appears to work
- Input and Output gain meters (LED) is constantly "full on"
- There is some coloring around the voltage converters, but this looks like kind of normal with hot parts and years of use.

What could be a likely root cause?
If I get this box fixed, I plan on doing the mods next, at least for the fun of it and some soldering practice

 

[Rob Flinn]

Have you put a meter on the power rails to verify they're are the correct voltage or are you assuming they're Ok because the led's light up ? I say this because you say you have the same issue on both channels, & the only thing that is common to both channels (unless things change when you operate the link switch) is the PSU.

The other thing is you are using the phrase "appears to work" quite a lot. That's not too useful in troubleshooting. It either works or it doesn't. Which is it ?

I have a friend who years ago had 2 of these compressors & he had been reading about all the mods people had been doing to them. We modified one of the boxes & kept the other standard. I'm sure there will be other people who will disagree with me, but we didn't really notice any significant differences between the two boxes when A/Bing them afterwards. The second unit got kept standard.

 

[AcdNrg]

Hey Rob, thanks for pointing this out.

I had just opened the box yesterday and didn´t do any measurement yet. I will check for power later. "Appears to work" because I only did a visual inspection so far. For gate, setting the dials to a position that would make sense I see the green and red LED indicate there is a state change and that works as expected (when dialing other settings). I haven´t plugged in any audio yet, that comes later today or during the week. After that I can make better statements. If the metering does display what´s going on though, I ´m prepared for a lot of nasty noise ^^.

Thanks for sharing your modding experience, I´ll keep that in mind (if I can fix this thing in the first place).

Cheers!

 

[soapy_goat]

I´m looking for a point to get started

Start working your way through, do you have the service manual?

Here: https://www.manualslib.com/manual/2886701/Alesis-3630.html?page=26#manual

 

[Rob Flinn]

"Appears to work" because I only did a visual inspection so far.

In my experience quite often visual inspections can mean next to nothing or be misleading.

 

[Script]

Here's a mod -- for later though. Matching the resistors L&R around the input and output across channels -- is what I found makes sense with this unit. Other than that, maybe PSU caps, but definitely gate switch. But that's it really.

Hope you can get it running again. It's a fun FX comp -- nothing less but also not much more.