DBX 160XT Issue
« on: June 26, 2020, 12:42:29 AM »
Hi all,

I'm hoping you can help me out.  I have a DBX 160XT that I got with both fuses blown.  I replaced the fuses and the top right cap in the photo gets very hot, the fuses blow, and both meters on the front light up more and more as the unit is powered on until the fuses blow.  Might anyone know what the issue is?  I'd certainly appreciate any help.  Thanks in advance!

The photo is here

https://workdrive.zohoexternal.com/external/7tRLoqCJOZ3-Mzdx0



radardoug

Re: DBX 160XT Issue
« Reply #1 on: June 26, 2020, 01:58:02 AM »
That board looks like the glue round the caps has gone bad, but it might be the caps. Start by measuring everything in that area. Could be a faulty diode or a cap. Probably change the caps anyway. Do you have tools and electronic skills?

synthiaks

Re: DBX 160XT Issue
« Reply #2 on: June 26, 2020, 04:07:20 AM »
The PSU caps must go! And probably all other Electrolytic Caps in there.

I always change the Caps before i even start the quest for anything else. Old potentially leaky caps that seep DC all over a circuit wont make Troubleshooting easier or fun.

If they weren't bad they would have gone bad sooner or later anyway.

A desoldering gun is much recommended for this task, or you will end up with broken traces.


s
"ex observer in silence"

jensenmann

Re: DBX 160XT Issue
« Reply #3 on: June 26, 2020, 08:50:18 AM »
If an electrolytic cap gets really hot then there´s a significant AC current flow. Check first if the diodes in the rectifier section are ok. Recap at least the PSU, then measure what´s going on.
Jens
Quote from: PRR
The tubes of course don't care what frequency they distort

squarewave

Re: DBX 160XT Issue
« Reply #4 on: June 26, 2020, 10:30:01 AM »
If you know someone with an oscilloscope I would poke around and sanity check things. That board looks pretty new so it's not obvious to me that the electrolytics are bad. It could very easily be something else. I like the bad diode theory. A scope would show you that quick. A DMM might tell you that.

Whoops

Re: DBX 160XT Issue
« Reply #5 on: June 26, 2020, 10:07:45 PM »
I always change the Caps before i even start the quest for anything else. Old potentially leaky caps that seep DC all over a circuit wont make Troubleshooting easier or fun.

If they weren't bad they would have gone bad sooner or later anyway.

Yes, I do the same, I replace all the electrolytic caps in the PSU first.

Then measure AC in before the power transformer, then at the secondaries (before the diodes) then the DC after the Diodes.
Then DC at the Regulators input and then DC at regulators output.

As far as I remember this PSU is pretty simple it's a linear PSU, easy to troubleshoot

pvision

Re: DBX 160XT Issue
« Reply #6 on: June 27, 2020, 02:40:33 PM »
That board looks like every 160X & XT I've ever looked at...

Fire the thing up and check the regulated & unregulated rails at the test points before the fuses blow. This will help to nail down where the problem lies

You'll probably find that the unregulated rails are OK and that one or both regulated rails are being dragged down. If that's the case replace CR18 and / or CR19 & test again

If there's still a problem, see if Y3, 4, 6 & 9 link the psu to the rest of the board. If so you could cut those to isolate the psu from the board. I had to cut traces on one of mine to achieve that

The fault on mine was a shorted diode - CR18 or CR19. The regulator survived

Nick Froome


 

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