Hi,

I recently aquired a DBX 160XT from ebay, I live in the UK and used an adapter to test the machine not realising that it only had a 1amp fuse in the plug. I switched on the unit and it was quite noisy at first (please let me know if this is normal) then I lifted the ground nob on the back to LIFT then the noise stopped. I never had chance to see if the lights on the front were on while it was making the noise and since it stopped making the noise it hasnt worked since.

So it as at this point that I realised that I had used a converter plug with a 1amp fuse, . . . . . so I went to my local electronics shop and purchased a good converter plug with a 13amp fuse, but it still dosent work ! I have checked the fuses inside the dbx (2x300ma 250v) but they dont look blown however they have very thick wire inside which is blackened in the middle a little but not split ? If anyone can help it would be great as i'm pulling my hair out !!!!!! anyone with experience of repairing the unit or anyone with a us version in the uk please post your advice

P.S In the morning I plan to go and find the fuses for the dbx as my first point of call.

Sorry to hear about your difficulty. I'm not familiar with this unit but it looks to me like there may be a partial short somewhere in the unit. I don't think it is likely that you hurt the unit during the initial power on (or smoke test as it is sometimes called). Based on your description, it is probably a coincidence that the power cut off (or blew the 1A fuse?) at the moment you switched the ground lift. Perhaps that is what caused the power outage. Regardless, at this point there should have been no harm done (or maybe I should say, no more harm done), because the protection circuit functioned as designed.

But this changes after purchasing the plug with a 13A (!) fuse inline and powering it up a second time. If the internal fuses weren't functionng and the unit tried to pull more than 1A, there was no 1A line fuse to stop it from pulling a higher current... all the way up to 13A. This could be the cause of the blackened wires. If so, I would be surprised that it didn't catch on fire! You should check those internal fuses with an ohmmeter or a continuity check.

If you aren't handy, then a technician should look at this for you. But if you or someone you know wants to tackle this, the following tools are a good start:
a variac
a voltmeter
a soldering iron
a few fuses (proper type and size)
a schematic
a fair amount of patience
a fair amount of luck

-Thom

Hi Thanks for the reply,

The 1amp fuse was only in my uk converter and not the machine itself, do the american plugs have a fuse in them ? if so how do you get at it ? I have noticed that there is a panel on the back of the dbx XT which when removed has a slider switch from 110 and 230 ??

Thanks for all your help guys !

No, most US plugs do not have fuses inline with the actual power cord itself. The fuse is typically located on the rear panel, after the ac input and before the power supply. The better built units have a fuseholder with a removable cap for easy replacement. The cheaper designs have an internal fuse which you have to remove the cover to get to.

Regardless of where the fuse is located, I can't imagine that this unit takes a 13A fuse. 1 to 5A would be typical for a low powered device operated at 110 or 230 VAC. For proper operation in the UK, your slider switch should be set to 230. If it was set at 110 during intital power on, again that would not have caused any damage. It would just run very poorly (if at all) and the lamps would be very dim.

Hi

Are you not looking at it from the wrong direction?

If it was designed to work on 110 volts and was connected to 230/240.. it would not have bulbs glowing dimly.

I'm worried about the "converter" he speaks of. By converter, is it simply a plug adaptor that allows a USA ac connector to plug into a UK socket... assuming that the voltage selector on the unit is set to the corresponding voltage...?

or

Is it a step down transformer?

I think it more likely the former. I suspect it's the sort of adaptor that you use in the UK to plug a 2 pin electric razor into a 3 pin wall socket...or a simple international adaptor. Hence the 1 amp fuse.

The fact that it was plugged in... and then the voltage switch noticed... worries me.

DeeDee needs to confirm exactly what the devices are and what the unit's voltage was set to when he plugged it in.

Hi,

The 1amp Fuse that I spoke of was in the 2pin the Uk converter plug that I used to connect it to my plug socket !!! I did the following:

Pluged my dbx 160XT with switch set to 110v into my pin converter plug (which had the 1 amp fuse) into a 230v uk power socket.

Today I took the machine into University's electronics dept who confirmed that the two 300ma 250v fuses that are inside the dbx are blown and they think that the transformer indide the dbx may have gone also, we put in two new fuses ( 315ma 250v as thats the closest we had to 300ma 250v) and it still does not work !! It looks like its the transformer inside the dbx with the 110 & 230v switch that has blown ?!

Any suggestions on what to do next would be greatly appreciated !!

Hi

I'd be surprised if the transformer is blown but it could be that electronics downwind of it are toast.

Find a dBx distributor in the UK and get it rebuilt?

Hi Geoff,
Ooops... Yes indeed, I was looking at this from the wrong direction (from across the pond where everything is 110). Looks like it was one of those late nights when my fingers pulled ahead of the still functioning part of my brain. Hmmm, maybe I need to get out more ~8^|

All the points that you've mentioned are spot on - had the switch been set to 110, there wouldn't have been anything dim about those bulbs.

Let's just hope that Dee Dee can confirm that the switch was set to 230 before power was applied.

-Thom

Hi

Sadly, no... for some implausible reason, the 240v 50Hz power was applied prior to establishing what voltage the unit had been set to and then, to the sounds of frying components and their effects on the audio path, the unit was left on for more time.

I don't have a diagram for a dBx 160 but would hope that it had IC regulated power supplies and the IC's gave of the lives as they tried to accomodate twice the normal voltage hitting them.

As they make a huge difference to the noise and ripple on the rails, the hum noise could have been the ripple passing through onto the audio.

What the IC's did with an unregulated and much higher voltage is anybody's guess... in fact, all I have written has been guesswork and assumption but, equally sadly, it will probably cost more to repair than the price he paid for it.

A hard lesson indeed....

He probably fried the power transformer and possible the 78/7915 regulators as well. Also, there are + - 24 volt unregulated rails to power the unbalanced LF351 opamp output. So, you need to check the opamp and the discrete power transistors for this output as well. Replacing the regulators won't help if there's a short on the unregulated transformer's outputs. Also check the mains filter caps as they also may be fried.

This sounds like a complete rebuild if he connected 230 volts into it. The school of hard knocks is an expensive place to go.

Jim Williams
Audio Upgrades

Just thought I would give you all an update, thanks to John at Orchid Audio in the UK my DBX 160XT is being repaired! looks like I fried the transformer so it wont cost me the earth.

Thanks again for all your help and advice

Hi

I really hope that is the case but I am amazed that no other components were harmed. I'd clarify this issue with him if I were you because, once he has juice going into the unit, a whole new can of worms might open... making a bigger dent in your wallet.