DBX F900a power transformer...

[Eliani]

Hey Guys,

I've got this DBX F900a rack that has a power problem. Everything works great when I start the module up. After a couple of minutes all the leds start flashing, like there's not enough power to drive them. I've looked at the power supply unit, and I can tell that it has been worked on. The edge connector between the power supply and the main board is missing, and the power supply is connected directly to the main board using double wiring, I guess to cope with the high current flow. The other thing I notice is that the rectifier has been replaced with a KBL04, but from the schematics I can't tell if this is the right one (CRA1 FVLC266? or FULC288?). Now about the power transformer. The schematics show a 4 to 3 wire transformer, no output voltage stated. but mine has been replaced with an Arabel TK142-EK 150VA 2x18V 4,26A. Is this sufficient to get the +24V and -24V needed for the DBX modules? I have 6 DBX 905 EQ's, and 2 DBX 903 compressors that I would like to start using properly...

 

[Biasrocks]

Hey Guys,

I've got this DBX F900a rack that has a power problem. Everything works great when I start the module up. After a couple of minutes all the leds start flashing, like there's not enough power to drive them. I've looked at the power supply unit, and I can tell that it has been worked on.

I don't think so.

It is most likely a 24VAC power transformer in the original, since you need two voltages, +/-15 and +/-24.

Looking at the schematic, the first two capacitors past the rectifiers are rated at 30 or 35v, so that seems to bear it out.

Have you checked the voltages to verify they are correct?

Regards,
Mark

 

[sodderboy]

Were the PSU caps replaced?  IIRC the originals would have been glued-down with a tan glue.  If you can get to the bottom of the board you will see what was replaced because 99% guarantee the work was not defluxed and will look different from factory soldering.
Definitely have to check all voltages when things are flashing.
Mike

 

[Eliani]

@biasrocks, the replaced power transformer has only +18v and -18v, they get upped to 24V unregulated, and 15V regulated. I read that the 15v needs to be within 0,1V tollerance. That wasn't  the case, +14.8V and -15.3V, put them where they needed to be.

The PSU caps are the original as far as I can see. The card edge connector was removed, and replaced with wires.
I've got 4 modules running stable, on/off switches are a bit old too...

I'll keep adding modules, one every day, to see if one of the modules is the problem.

I'm looking into getting a few DIY modules build for the DBX rack. Ok so no Phantom power, but a compressor like the GSSLwould be nice. Even if we could make an adapter to put 500 modules in, would be nice... I've seen people talk about this on the forum before...