ADA Microtube 200

[Skitzo]

Hi all,

I have a microtube 200 amp and it's been great so far!  However, I have no sound now.  When I plug it in, the lights on the front come on indicating power is getting in.  I opened it up and all three fuses are fine.  I also have (believe it or not) an old-school tube tester.  Both tubes are fine.  I don't see any blown capacitors....

Does anyone know of any tricks or known issues on this amp?  (I attached a pic)

[rnolan]

Hey Skitzo, only thing I can see from the pic is the tubes (particularly RHS in pic) could be a little better seated in their sockets, although it doesn't look enough to stop them working.
Apart from the usuall (which you may have done already) spray/clean the pots and sockets this topic may help (http://adadepot.com/index.php?topic=138.0).   The MT200 has a protect mode controlled by a neon bulb.  If that doesn't fix it, then it's over to MJMP et al for more serious fault finding.
Cheers Richard

[Skitzo]

Tell me more about the protect mode....  Perhaps it's just stuck in this mode?
How do I turn it off and on?

Thanks!

[rnolan]

Hey Skitzo, my understanding of it (from this topic which also tells you how to fix it (ADA Microtube - "protect" problems http://adadepot.com/index.php?topic=138.0)) is that when the MT200 warms up, it stays in protect mode (no sound) until the tubes have warmed up.  When the tubes are ready the neon light brings the PSU chip (power supply unit) out of protect mode, you can't switch it yourself.

(From one of Sparkers posts in that topic - "I think when the MT200 PSU startup thing was discussed some time ago, the neon inside the box, NE1 (a NE-2H type) was thought of as a suspect. This neon acts as an under-voltage protection for the PSU chip when the amp is switched on, when the neon strikes on the PSU chip is brought out of shutdown. The neons can degrade over time and the strike voltage can change, also they can show sensitivity to light")

Have a read of that topic (in the Power Amp Tech area), it's where I learnt about it. Cheers R

[Skitzo]

Thanks for the info.  A neon bulb eh?  Did you happen to see one in that diagram I posted?
If that is the culprit, where would I get one?

[GuitarBuilder]

Let's do a systematic check instead of just trying stuff.

First off - do you have the schematics?  If not, download a copy.  They are going to be very helpful.

1.  You say the lights come on.  Is the Protect LED on as well?  If not, then it's not in Protect mode.
2.  Does the fan come on?  If so, we know the transformer is getting power.
3.  Measure the voltages from the power supply.

Do all this and get back to us.  Please be careful inside - the high voltage will hurt you.

[Skitzo]

Yes I have the schematics....but I think it's the protect mode.  I can't get it to turn off.  It's been plugged in for the past 20 minutes and that protect mode light is still on.  Tubes have not heated up and the fan is not running.  The transformer and coil look fine.

Is there a trick to get the Protect mode to turn off?

Thanks!   

[MarshallJMP]

No the only thing you can do is replacing NE1.That soves this problem in 98% of the cases.

[Skitzo]

Damn... I downloaded the schematics at work and now when I try to open hem they won't decompress.  Anyhow, the NE-1 is that Neon Bulb thing?  Where would I get one of those? 

[rnolan]

From MJMPs previous post on ADA Microtube protect problem topic ("Only the MT200 has the protect  led.This is because it's the only ADA amp that has a switching power supply.Like sparker said,change the neon bulb and the problem will usually be solved.Let me know if you can't find one,i have a few lying around.") so MJMP may be able to get you one although my understanding is it's not a hard part to buy.

[Skitzo]

I PM'd MJMP - you guys are awesome!! Thanks for the help! I hope the bulb is the solution.  I don't live anywhere near an electronics store. So perhaps he still has one or someone can put me onto an online store?

You know how it died.... I was playing a gig and using the amp to power a couple small monitors.  A bunch if people were dancing really close and a guy stepped on the 1/4 cable going into the monitor.  He bent it and sent a signal back to the amp putting it in protect mode forever and ever. Next tone I buy monitors or PA speakers, they will be powered.

[Sparker]

I PM'd MJMP - you guys are awesome!! Thanks for the help! I hope the bulb is the solution.  I don't live anywhere near an electronics store. So perhaps he still has one or someone can put me onto an online store?

You know how it died.... I was playing a gig and using the amp to power a couple small monitors.  A bunch if people were dancing really close and a guy stepped on the 1/4 cable going into the monitor.  He bent it and sent a signal back to the amp putting it in protect mode forever and ever. Next tone I buy monitors or PA speakers, they will be powered.

Hi Skitzo - wish you had said this to start with!! If it wasn't in protect mode before the speaker stomping guy, you may have something blown / short in the output or PSU stage. It could also be in protect mode because of this.

[Skitzo]

Sorry, but it did work after he stomped it. But not for long - we were able to finish the set.  I took it to the electronics teacher at the school I work at and we tested everything we could and it all appears fine....  Which is why I think you're correct with NS1 being the variable.  We never even thought that it could be a factor. 

[Sparker]

Hi Skitzo, well it's an easy hit to change the neon anyway, so carry on as planned and let us know .

[Skitzo]

Hey Sparker,

I haven't been able to get in touch with MJMP so I tried ADA Tech suppor and didn't hear from them.  So, I'm just on a hunt for the NE1 bulb.  The one question I have is - Should the bulb be coupled to the unit?  I took the cover off the power supply and found the bulb and it got this white goop on it attaching it to the unit. Should it be like that?  Does it matter? 

Any idea where I can find an online catalogue and order and NE1 bulb?  (Sorry about the quality of the picture)