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LektroiD
Joined: Aug 23, 2008
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Location: Scottish Borders
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 Posted: Sun Jun 12, 2011 6:24 am Post subject:
Faulty Novation Drumstation
Subject description: Any help welcome |
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Yesterday I noticed the Drumstation channel on my mixing console was lit up, so I raised the gain to hear a loud buzz coming from the unit. I looked up to see the two 7-segment LEDs fully lit up (displaying 8.8.). None of the other LEDs were lit.
The sound is a pure square wave at the master outputs, and the left portion of the waveform is slightly ramped (dampened sounding square wave) on some of the individual outputs. The headphone output appears to be a square wave with some small noise artefacts. All at 101Hz.
The Novation PSU-4 power supply seems to be working; I'm getting 11.05V (Unloaded) and 7.2V (Loaded).
The 7805 regulator is outputting +6.47V at pin 1, and +3.42V at pin 3.
The unit is left on permanently since there is on on/off switch on the unit, and it is not easy to get to the back of the rack to pull the power cable out after each use.
I'm at a loss as to where this fault could be originating.
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diablojoy
Joined: Sep 07, 2008
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Location: melbourne australia
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| Posted: Sun Jun 12, 2011 8:29 pm Post subject:
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| Quote: | | The 7805 regulator is outputting +6.47V at pin 1, and +3.42V at pin 3. |
+6.47v at pin1 should be fine
+3.42v at pin 3 is definitely wrong
thats the regulated output and should be very close to 5v
within five to 10 milli volts anyway
would suggest removing the supply output to the main board and
checking the voltage at the reg 7805 pin 3 again but with a small
dummy load in place say a LED with a 2.4K resistor
if its still only around 3.4 v then chances are its the reg thats faulty
however i would also check any electrolytics nearby of
also possibly failing as well |
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v-un-v
Janitor
Joined: May 16, 2005
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| Posted: Mon Jun 13, 2011 2:56 am Post subject:
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Yes, I was just going to say, try the caps! Especially electrolytics, especially if Novation used crappy ones.
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LektroiD
Joined: Aug 23, 2008
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| Posted: Sat Jun 18, 2011 5:58 pm Post subject:
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Thanks for the replies.
I swapped out the regulator, no joy there. There's no physical sign of leakage from the electrolytic, but I'll get that swapped next time I have it on the workbench. I'll update the thread accordingly.
I can't find a service manual for this either, if anyone has one, I'd really appreciate a copy. 
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LektroiD
Joined: Aug 23, 2008
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| Posted: Tue Jan 10, 2012 6:59 pm Post subject:
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Just got back to this little box, yet it still defeats me.
I've replaced the electrolytic cap, retouched all the solder joints and it has made absolutely no difference; the problems still persist.
I just can't think of what else to do with it, except plant it at the local rubbish dump. |
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diablojoy
Joined: Sep 07, 2008
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Location: melbourne australia
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| Posted: Tue Jan 10, 2012 8:57 pm Post subject:
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without a cct its difficult
something is pulling too much current
check for anything that is a little too warm
if that does not find it
if the ic's are socketed try pulling all the ic's if you can and check the supply voltage
if that sorts the reg supply
put them back in one at a time checking the voltage after each one
it may narrow it down to an area to check
| Quote: | | The sound is a pure square wave at the master outputs, and the left portion of the waveform is slightly ramped (dampened sounding square wave) on some of the individual outputs. The headphone output appears to be a square wave with some small noise artefacts. All at 101Hz. |
does the square wave appear on all of the individual outputs or only some ? if only on some, which ones ?
maybe something common between certain individual sounds
the master and headphone cicuitry i think can be discounted for the moment as less likely area's to be at fault
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LektroiD
Joined: Aug 23, 2008
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| Posted: Wed Jan 11, 2012 4:02 am Post subject:
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| diablojoy wrote: | without a cct its difficult
something is pulling too much current
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Not sure what a 'cct' is, I did look online for acronyms but couldn't find anything relative to electronics (unless the Christian Council of Tanzania are able to help out). 
| Quote: | check for anything that is a little too warm
if that does not find it
if the ic's are socketed try pulling all the ic's if you can and check the supply voltage
if that sorts the reg supply
put them back in one at a time checking the voltage after each one
it may narrow it down to an area to check |
Only the 2 ROM chips are socketed, the rest are surface mount except a Sharp PC910 thru-hole chip which is soldered directly.
| Quote: | | Quote: | | The sound is a pure square wave at the master outputs, and the left portion of the waveform is slightly ramped (dampened sounding square wave) on some of the individual outputs. The headphone output appears to be a square wave with some small noise artefacts. All at 101Hz. |
does the square wave appear on all of the individual outputs or only some ? if only on some, which ones ?
maybe something common between certain individual sounds
the master and headphone cicuitry i think can be discounted for the moment as less likely area's to be at fault |
The 'square wave' (see pics) is the same across every output, doubled in voltage at the master out, and doubled again at the headphone out.
Each power up produces a different waveform (*Note the DC offset between the master and individuals at powerup 1). Occasionally no sound happens at any of the outs except at the headphones. Sometimes the display & LEDs light up differently too, changes happen per power up.
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diablojoy
Joined: Sep 07, 2008
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| Posted: Wed Jan 11, 2012 4:38 pm Post subject:
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| Quote: | | Not sure what a 'cct' is, I did look online for acronyms but couldn't find anything relative to electronics (unless the Christian Council of Tanzania are able to help out). |
sorry my bad vernacular
actually meant a schematic
| Quote: | | The 'square wave' (see pics) is the same across every output, doubled in voltage at the master out, and doubled again at the headphone out. |
yeah the headphone outs will undoubtable have a fair bit of gain
wouldnt have expected the masters to be double the individual though
but it is common to all channels so thats something.
| Quote: | | (*Note the DC offset between the master and individuals at powerup 1 |
there will be a summing opamp stage somewhere there to mix the individuals possibly a TL0xx series chip but i dont know for sure what they may have used. the headphone circuitry will be tapped off the master
through another opamp something like an lm386
you are going to need a schematic i think
someone out there will have one.
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LektroiD
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Dougster
Joined: Sep 20, 2005
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Location: Tucson, AZ, USA
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| Posted: Thu Jan 12, 2012 5:04 pm Post subject:
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How much do you think shipping to the States would be?
Regards,
Doug
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LektroiD
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| Posted: Thu Jan 12, 2012 8:33 pm Post subject:
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Hi Doug, I set the shipping to £30 (ballpark figure). However, it is no longer for sale...
I just discovered my bench supply was not wired correctly (I've just moved house, and in the process of resettling). Once I got the PSU rewired, I powered the unit up off the bench and it worked. So it was then time to go inside the wart... Turned out to be a burnt out bridge rectifier. I replaced the rectifier and put a more sturdy cap in for good measure (2200µF in place of the 1000µF).
One thing I will say though, after seeing the quality of workmanship inside the wart, I will never buy another Novation product as long as I live.
I unlisted the item. The nearest option was "this item is no longer working" (well, they say two grammatical negatives make a positive).
Time to go and wake the neighbours... |
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Dougster
Joined: Sep 20, 2005
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Location: Tucson, AZ, USA
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| Posted: Thu Jan 12, 2012 8:48 pm Post subject:
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Well, good on ya for fixing it! Odd how power supplies seem like they should be so simple, but I've had several items that didn't work properly and it was all due to power issues. Lessee, off the top of my head, I've repaired the power supplies in an MKS-30, an Emu Morpheus, a Kurzweil K2500R, an Ensoniq Fizmo, and of course, the granddaddy of power supply nightmares, the Rhodes/ARP Chroma...
Regards,
Doug
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diablojoy
Joined: Sep 07, 2008
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| Posted: Thu Jan 12, 2012 9:00 pm Post subject:
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| Quote: | | Turned out to be a burnt out bridge rectifier. |
ha seems i was over thinking things again
glad to hear you got it running
may it produce good sounds for you for many years to come.
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TheAncientOne
Joined: Dec 26, 2006
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| Posted: Wed Jan 18, 2012 7:09 am Post subject:
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| LektroiD wrote: |
One thing I will say though, after seeing the quality of workmanship inside the wart, I will never buy another Novation product as long as I live.
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In fairness to Novation, most of these companies buy in the 'wart' supplies, in order to get the necessary safety certification. Some oversea suppliers gradually downgrade the quality of the parts supplied, (so the unit you approved when you put out your first order may be nothing like what is being shipped later). I still think it's poor practice to put such bargain basement power units with expensive synths, though.
I just replaced a PSU in an industrial unit with an Astec switchmode. The Astec high quality unit cost £175 + VAT. It will shut down under fault conditions and has a 2 year guarantee. I could have replaced the original for £80, but it had only lasted 18 months in an industrial environment. I've had the high quality Astecs and the Coutant Lambda power supplies in non stop operation for 5 years without failure. They both also do 'medical grade' supplies, which are very high quality, but at a matching price.
I've made replacements for a lot of 'wall warts' in my own units. I don't begrudge £20 worth of bits to get a more reliable, cooler running supply, (oh, and with actual replaceable fuses where they count, too!)
Congratulations on getting it fixed.
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