ADA Depot - A Forum To Support Users of ADA Amplification Gear

Let's Get Technical => Troubleshooting Problems => Topic started by: emunstar on November 15, 2014, 11:56:26 AM

Title: No lights, no display, no sound
Post by: emunstar on November 15, 2014, 11:56:26 AM: I've got a MP-1 that died on me a few years ago. I had it at a gig when the singer inadvertently killed the stage power while hanging a backdrop. The unit was on at the time but once the power was switched back on my MP-1 had no display, no light, and passed no audio. Looking inside I can hear the transformer hum and the tubes are glowing so there is at least power up to the tubes. Any ideas? The power was shut off and rapidly turned back on in a matter of seconds so my best guess is something on the unit has blown. Nothing inside appears burnt, there are no swollen capacitors or other visible signs of component failure.
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on November 15, 2014, 12:18:40 PM: If you have a backup of your presets you could try to pull the RAM chip out and back in,sometimes with a brown out the RAM can become corrupt,not always but i've seen it before.

But first can you measure the voltage over the 3 big caps near the power supply?
Title: Re: No lights, no display, no sound
Post by: emunstar on November 15, 2014, 05:21:14 PM: Thankfully there are not any presets that I would mind erasing. I'll try pulling the chip. What are the voltages I should be seeing at the caps?
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on November 15, 2014, 08:12:05 PM: The 3300 µF cap should have 8 to 9 Vdc,the 2200µF caps should have around 20-22 Vdc
Title: Re: No lights, no display, no sound
Post by: emunstar on December 29, 2019, 01:25:29 PM: Quote from: MarshallJMP on November 15, 2014, 08:12:05 PM
The 3300 µF cap should have 8 to 9 Vdc,the 2200µF caps should have around 20-22 Vdc

To revive an ancient thread, I fianally got to test the caps and the results are

3300µF is 7.4vdc
2200µF were 23.2vdc and 22.9vdc......
Title: Re: No lights, no display, no sound
Post by: vansinn on December 29, 2019, 03:24:48 PM: Wow.. talk about combined deja vous / flashback..
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on December 30, 2019, 05:52:20 AM: 7.4V is quite weak, a 7805 5V regulator needs a 2.5V difference on the input.
Title: Re: No lights, no display, no sound
Post by: emunstar on December 30, 2019, 07:58:10 AM: Quote from: MarshallJMP on December 30, 2019, 05:52:20 AM
7.4V is quite weak, a 7805 5V regulator needs a 2.5V difference on the input.

Would you suggest changing the 3300µF cap?

Additionally, does anyone know the appropriate crystal to use should it need replaced? I attempted to measure its frequency and got nothing. I'm not sure if its faulty or my DMM just can't read it. If I'm reading the crystal right its 12mHz.
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on December 31, 2019, 03:57:53 PM: Well if the 3300µF cap is leaking then you should change it. Does it get warm?

Yes it's a 12MHz crystal. DMM's usally go up to 100kHz so best way to measure it is a scope. Also you could try to measure the voltage on pin 6 of the Z80, in theory you should measure 2.5Vdc (maybe less).

Try to fire the unit up without the tubes in it, see if it will start.
Title: Re: No lights, no display, no sound
Post by: emunstar on December 31, 2019, 05:22:20 PM: I have tried to fire it up with the tubes in it and it did not start up. I've also tried to get it to start by rapidly switching the power on and off to no avail.

I'll feel the cap and see if it gets warm.

Funny thing, I just noticed that there isn't a battery in the unit either.

Question on the crystal, will any 12mHz crystal work our is it like a capacitor in that you need a few parameters matching like farad and voltage?
Title: Re: No lights, no display, no sound
Post by: bunkyloo on December 31, 2019, 05:30:07 PM: I have a unit with the same issue exactly. Where is this crystal located? I tried to fire up both ways . The tubes do glow . Looks like same issue possibly. Thanks Steve
Title: Re: No lights, no display, no sound
Post by: emunstar on December 31, 2019, 07:31:30 PM: Quote from: bunkyloo on December 31, 2019, 05:30:07 PM
I have a unit with the same issue exactly. Where is this crystal located? I tried to fire up both ways . The tubes do glow . Looks like same issue possibly. Thanks Steve

It's circled in yellow on the attached picture. Right side of the main board.
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on January 01, 2020, 03:32:29 AM: Check if you have 5V on pin 26 of the Z80.
Title: Re: No lights, no display, no sound
Post by: bunkyloo on January 01, 2020, 11:19:04 AM: I did manage to check my caps the 3300 was 11.25 vdc and the 2200's were22.3 vdc and 22.7 vdc.
Pin 26 on the z80 was 5.11 vdc and pin 6 was 1.6 vdc. I should also mention I see a quick ADA logo and sometimes version text only for a split second when I power off and it looks like a September of 87. I guess anything could be wrong.
Any thoughts ? Thanks Steve.
Title: Re: No lights, no display, no sound
Post by: bunkyloo on January 03, 2020, 03:47:27 PM: Emunstar any luck with you're findings ?
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on January 04, 2020, 01:21:54 AM: Can you also check pin 16?
Title: Re: No lights, no display, no sound
Post by: bunkyloo on January 04, 2020, 07:16:26 AM: I have 3 volts on pin 16.
Title: Re: No lights, no display, no sound
Post by: emunstar on January 12, 2020, 08:18:06 AM: Quote from: bunkyloo on January 03, 2020, 03:47:27 PM
Emunstar any luck with you're findings ?

I haven't had time to check anything further, hoping to dig back in soon.
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on January 13, 2020, 05:14:50 AM: Do you have access to a scope?
Title: Re: No lights, no display, no sound
Post by: bunkyloo on January 13, 2020, 07:34:35 AM: I do not have one. If it is going to be needed I can look into getting one I suppose. Any specifics I would be looking for?
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on January 15, 2020, 07:51:00 AM: a 2 ch 20MHz will be fine.
Title: Re: No lights, no display, no sound
Post by: bunkyloo on January 15, 2020, 07:58:21 AM: great I will look into it Thanks Steve
Title: Re: No lights, no display, no sound
Post by: bunkyloo on March 01, 2020, 03:20:46 PM: Well I grabbed a cheap handheld scope. So go slow with the next tests Im just learning the basics with that thing. Thanks in advance.
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on March 02, 2020, 12:57:16 PM: Ok you got that Hantek 2D42 scope right?

You know what, maybe we can do a skype session, else it will take to long. Also then I can see what you measure, and I can tell you where to measure. And when we solve the problem we can put the problem and solution in this topic.

So send me an email to see when we can do this.
Title: Re: No lights, no display, no sound
Post by: bunkyloo on March 03, 2020, 06:01:03 PM: Yep I did MJMP I hope its up to par and that's a great idea and makes sense I will email you soon. Thanks again.
Steve
Title: Re: No lights, no display, no sound
Post by: MarshallJMP on March 04, 2020, 11:42:35 AM: From what I can see it should be on par. The highest frequency in the mp-1 is 12MHz.