ADA8000 Behringer No Power

[ReRibbon]

Hi all.

Just picked up an AdA8000 that doesn't power up. The seller said one day it just stopped turning on.

I've heard that these can be useful units and can even be modded to be nicer sounding.

Any suggestions on how to identify the power problem? I have a multimeter.

Thanks in advance.

 

[radardoug]

Gosh, this is like 'My car just stopped, whats wrong with it?'. I dont think any of us here are mindreaders or magicians. You have a multimeter, start measuring.
It probably has a switchmode supply so WARNING!!! THEY BITE!! Quite possiblly dry caps, or broken dropper resistor for the switchmode chip.

 

[ReRibbon]

Yeah, I guess I deserved that. I dont know quite what to look for.
Is anyone familiar with these units and their faults? I'd like to be able to use it.

 

[Khron]

The common fault with these is that (half of) the primary burns out (a small toroidal transformer). And beside, the secondary voltages are unreasonably high with the stock one, so the regulators run a bit hotter than they'd need to.

I did an extensive modding on one, shoehorning in a 12VAC transformer and some voltage doubling stuff to give me a close-ish bipolar voltage for the analog stuff and the phantom power. Mainly because that was the only transformer i had at the time, and i wanted to get it working.

That being said, if you can find a 2x14 or 2x15 VAC little toroidal, that should be MacGyver-able in there, with a voltage doubler / multiplier for the phantom.

https://khronscave.blogspot.com/2017/11/25-behringer-ada8000-ultragain-digital.html

 

[Khron]

I should also add that my initial hack-fix was less than ideal - when installed, the lid rattled like a mofo from the magnetic field from that EI transformer

At the time i just wanted to prove a point or something... And to try to make sure everything else survived unscathed.

 

[ReRibbon]

I guess what I'm asking for is advice on the proper method to troubleshoot. What to look for etc.

 

[JohnRoberts]

If you have a dead rock the obvious first path is to look for PS voltages.

Be careful probing around mains voltages.

JR

 

[Whoops]

Is anyone familiar with these units and their faults? I'd like to be able to use it.

Yes, and there's a discussion already in this forum on this subject, there's some models that the PSUs fail, do a search and you will find the thread and the relevant information there.

I would just take out the original crap PSU and make a new and propper one and install it.

 

[ccaudle]

Any suggestions on how to identify the power problem?

Start by measuring the outputs of the power supply to see if any are at the correct voltage. If some are good and some are not that narrows down where to look. If none are, either something early in the power chain is not working, or there are interlocks that turn off all rails if any one is out of regulation.
Look for any blown fuses, look for electrolytic capacitors which have a bulging top or have any traces of electrolyte leakage. Bad electrolytic caps are a common source of problems on cheap equipment. Look for any broken solder joints, especially around heavier components like large capacitors, transformers, etc. that might have resulted from a drop to a hard surface or high vibration (being carried around in a truck for example).
I do not know the internals of an ADA8000, look around the power supply to see if there are any stickers or labels indicating it may be from a third party. If it is an off-the-shelf supply you might be able to find information online.
Sometimes you can disconnect the power supply from the rest of the circuitry to check whether a short downstream is preventing the power supply from turning on, but that doesn't always work with switching supplies, some need a minimum load to run and won't power on correctly with the load disconnected.

I just found a picture online of the internals of an older model. Does yours look like the one in this picture?
ADA8000 teardown picture

If so you are in a good starting position, that is a plain linear power supply, no tricky switching power supplies to debug. Start following connections through components, and draw yourself a schematic diagram to keep track of everything, then start measuring voltages through the circuits. It is a little easier if you have access to an o'scope, but you can do a lot with just a multimeter. With AC power removed check the diodes, make sure none are shorted or open. Check the caps for bulges as mentioned previously. Apply power and measure across the caps, make sure whether power is getting through the diode bridge and charging up the caps. Measure AC voltage across the caps, that should be a very low value (e.g. on a 5V DC supply I would expect less than 0.5V AC and around 8V DC, or less than 1V AC on 15V for the 12V DC supply).
If the supplies are OK at the caps, check the outputs of the linear regulators, possibly a regulator was underspecified or has an undersize heatsink. Touch the heatsinks carefully to see if a regulator is heating up really quickly, that would indicate either a blown regulator, or a short circuit downstream from the regulator.

That should give you a good start, there are only so many things that can go wrong with a linear power supply. I don't know what voltages are present, probably +/-12V or +/-15V for the analog components, 3.3V for the digital components, and either an extra winding from the transformer, or a diode tripler type circuit to generate 48V for the microphone phantom supply. Possibly a +5V analog for the A/D converters, you would just have to look up some component specs to see what to expect. If you are lucky there will be labels on the PCB for the various voltages, otherwise you will just have to start measuring.

 

[Khron]

The ADA8000 has a toroidal transformer, which is infamous(?) for toasting its primary windings, for whatever reason.

No fancy interlocks in the power supply / regulation whatsoever, just a handful of 7805 / 7815 / 7915 and an LM317.

As it happens, i do in fact seem to have at least a partial schematic of this thing. Just a couple of GIFs, no idea where i found them, so don't blame me for the quality (or lack thereof)

 

[okgb]

A friend rebuilt [ modded it ] his psu no problems since [ the problem was it drew too much current when used in 120v ? ]
the info is out there!

 

[ReRibbon]

Tha ks for the amazing replies and the schematic drop!!!!

I have a different version. I'll try and post pics shortly.

 

[ccaudle]

a toroidal transformer, which is infamous(?) for toasting its primary windings

That seems strange to me. I would be interested in hearing from other experienced designers, what mistake results in failing on the primary side. I have seen secondary side problems from too much current, I suppose something similar could cause the primary to fail if the primary winding wire size was undersize by a large amount. I thought that usually safety requirements resulted in enough insulation thickness on primary windings that they rarely pull apart.

 

[ReRibbon]

So mine has a different setup coming from the transformer. On mine there are not any capacitors before the diodes.
I've tried loading pictures. Will see if I did that right.

 

[ReRibbon]

Maybe this is a better pic.

 

[Tubetec]

I dumped the entire preamp section on my ADA8000 , everything runs nice and cool now .
I wired the front panel XLR's via coupling caps to the ADC inputs on the wavefront ICs , so now balanced line level input only.

I did have to add back the master and lock leds from the main board to the stripped out front panel after .

 

[Tubetec]

Best check continuity on the transformer primary with the multimeter ,
With the unit plugged out and disconnected from the mains , check the resistance between the live and neutral pins on the IEC socket with the multimeter , ensure the front panel switch is on , if theres no reading in the low ohms range either the fuse or the transformer primary is out .

 

[ReRibbon]

That's cool. How did you setup the coupling caps?

 

[cyrano]

Maybe this is a better pic.

The voltage regulator(s) look fried...

The problem with the primary of the toroidal was only bad on the second generation ADA8000. It seems the primary was split in 100/130V and with some (US 110V) units, the 100V winding was connected in stead of the 130V. That resulted in too high temps for the voltage regulators and they burned out. The first gen had a 110/110V split but that wasn't ideal for some places in the USA because of brownouts. It also meant no units for Japan (100VAC).

But even in 230 V units, the voltage on the secondary is too high. I remember measuring something like 76 VDC on the poor 48V regulator input.

If you stack these in a rack without spacing and additional cooling, they usually won't last very long. I've got three of them.

The only mod I would consider, is what Tubetec has done. Remove the mic preamp board. Should give you line level at around -8 dB, which is fine for inserts on most analog mixers.

I've put some diodes in series with the DC+ rail to alleviate the heat a bit.

 

[Whoops]

READ THIS THREAD

https://groupdiy.com/threads/behringer-ada-8000-owners-please-read.20591/