My Alesis ProLinear 720 DSP Failed

[rp88.2]

Good advice, all. A VOM is an essential studio utility belt item, right next to the DeOxit and WD-40. Also, a touch of DeOxit behind the ears makes the ladies swoon.

+1 on the VOM, DeOxit and WD-40. DeOxit works wonders on those little MOTU Ultralite knobs! Will try the the behind the ear trick this weekend.

As for the wattage of the resistor, you can [usually] tell by the thickness-- if you google the topic you can get an idea of the wattage. Go up one size (watttage rating) just to be safe when you replace.

Good luck!!

[mikehalloran]

Thank you, Mike.

The bad resistor's broken in half so I figure I'd have to measure the "good" one. Only, if I snip one of the stems, how do I rejoin it if need be? Perhaps it's not the "done thing".

Just forget about it and replace both, I suppose...

Yes. The value need not be exact since resistors are always made within a stated tolerance. You want a pair of them as close as you can get. And, as stated by others, up the power rating by one size. Power rating = heat tolerance. If one cooked, the other will. Count on it.

[monkey man]

Thanks guys.

[monkey man]

OK... managed to take the power module into a local electronics store and asked the experienced dude there to eyeball the component for me.

Turns out (if he's correct) that it's an NTC thermistor. After looking it up on Wikipedia 'though I wonder if it might be a PTC thermistor.

Apparently no way to measure it, so there's that. At this point I think I need someone who understands the part and its use in amps to take a guess as to what the rating might be; there are apparently 30-odd flavours.

The amp is the built-in Alesis Prolinear 720 DSP's power amp, rated at 120w IIRC.

[tetrasect]

OK... managed to take the power module into a local electronics store and asked the experienced dude there to eyeball the component for me.

Turns out (if he's correct) that it's an NTC thermistor. After looking it up on Wikipedia 'though I wonder if it might be a PTC thermistor.

Apparently no way to measure it, so there's that. At this point I think I need someone who understands the part and its use in amps to take a guess as to what the rating might be; there are apparently 30-odd flavours.

The amp is the built-in Alesis Prolinear 720 DSP's power amp, rated at 120w IIRC.

I have the 820 DSP's and the thermistor at RT1 is a N10SP005 by UEI. It looks identical to this one:


https://www.yoycart.com/Product/526366328972/

About a year or two ago one of my speakers didn't wanna turn on and I opened it up to see that thermistor was fried. At that time I didn't find anything on google and figured "SP10" must mean 10ohm (it's actually supposed to be 5 ohm) so I replaced it with this one and it has been working perfectly ever since: https://za.rs-online.com/web/p/thermistor-ics/0467620/


About 2 weeks ago my other speaker started turning off so I decided to replace the thermistor on that one as well. Lasted a few days before it started turning off again. I replaced the 5A 250V fuse which is next to the thermistor but now it won't switch on at all! Also tried replacing the thermistor once again but it didn't help.

Anyone out there have an idea what else might be wrong? Is it possible that my terrible soldering skills are to blame?

[monkey man]

Man, how can I ever thank you? Thank you so much!

There's an RS Components store in Sydney that I'm hoping will be able to post a set of the EPCOS B57235S0100M000s down to me soon.

I noticed that the store you linked to is in Kyalami, so...
Is jy van Suid-Afrika? Ek het daar grootgeword tot ek 12 was.

As for the other speaker's refusing to fire up, I'm sorry I don't have a clue what it might be. Most things electrical are way above my pay grade. I'm sure many of the peeps here will have some ideas as to what the issue might be 'though, so hang in there. I mean, your info is the most-solid (and relevant) I've received in 3 months in two forums. I've been waiting patiently whilst my speakers sit covered on the kitchen table.

Thanks again mate, and hang in there...
Nicky

[tetrasect]

Glad to be of help!

I figured maybe my 10 ohm thermistor isn't playing nicely with my second speaker so I ordered the 5 ohm EPCOS B57235S0509M000 which is (or is closer to) what was originally in there and will give that a try.
If that fails I will have to try find a "real" electronics tech, which are hard to come by in these "replace the whole board" times.

Lol funnily enough I moved to South Africa when I was 12, so I can't speak Afrikaans but I do understand the more everyday stuff I hear on the street.

I'm quite certain your speakers will be good as new soon, good luck!

Oh one last thing... if you do the repair yourself, get a soldering iron with a fine tip cause I made a mess with mine. Burned silicone seems like an indication of a job done badly...

[monkey man]

Ha! So you moved in at 12 when I moved out at 12. Too weird.

Please let us know how the 5Ω thermistor goes!

Thanks for the update, broer.