DBX 128 Schematic

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doulos24

Active member
Joined
Apr 9, 2010
Messages
32
Does anyone have an actual dbx 128 schematic or service manual? I bought one off ebay in "working" condition  and I can't seem to get it working. I measured the voltage from pin 4 and 7 of the OA1 lm301an. and I'm reading 170mv dc I'm guessing it's the voltage regulator chip? or that transistor that needs changed I ordered both parts. but a schematic would be very nice to have 

I ordered a NTE128 for the to TO39  transistor and the regulator MC1723CP.

dbx1181_zps15345c70.jpg
 

I started modding this before I testing if it was good :( A big mistake I won't make again. I changed out the electro caps in the psu with newer ones. I socketed all the opamps.  I removed the blue tantilum caps  in the psu. I even changed out the diodes. 
If anyone else has anything else I can try please feel free to let me know. 

thanks
 
Ok, you should be able to trace the voltage from the power transformer, it will go to 2 or 4 diodes, then to the power supply caps you already replaced...sorry if you already know this..I'm assuming you do since you mention you ordered a power transistor and regulator, is that were the power stops?
 
yes that's where the power stops. I measured from ground to pin 4 of the OA1 opamp and I get continuity so I assume it's single ended and I'm measuring 170mv instead of something like 12 to15 volts   
 
this is really frustrating I got the new parts and changed out the npn and now I'm seeing 48volts on the output of that transistor, but the regulator is max input of 40volts? still seeing milivolts on the power input of the fist op amp 
 
I would check for cold solder joints, measure the output of the regulator (using the datasheet for pinout) follow that power rail as far as you can to see were its getting stuck. Its something simple!
 
none of that helped a very nice guy got me the schematics I needed and I found 4 falty tantalium caps  that were shorting the noise reduction cards to ground and a blown nte 128 npn. I replaced them, but there is still some weird crap going on with the noise reduction cards, so I pulled them and now I basically have a dbx 118 that is working. Now I'm choppin up a filtered + - 15v supply board to inject into it to make it run quieter then the stock psu and after that I'll add a stereo balance board on the record input and output sections and call it a day.  :p


 
 
doulos24 said:
none of that helped a very nice guy got me the schematics I needed and I found 4 falty tantalium caps  that were shorting the noise reduction cards to ground and a blown nte 128 npn. I replaced them, but there is still some weird crap going on with the noise reduction cards, so I pulled them and now I basically have a dbx 118 that is working. Now I'm choppin up a filtered + - 15v supply board to inject into it to make it run quieter then the stock psu and after that I'll add a stereo balance board on the record input and output sections and call it a day.  :p
Click to expand...

Glad you got it sorted out. In retrospect you could have pulled the cards out and measured the voltage rails. Schematics are overrated sometimes. (though always make things easier)
 
Hi. I got one off eBay and they has said they tested it at 240v when it arrived i plugged it in to 240v and it blew up, I opened it up to find the switch at 110v. now the power components are fried. I am in Dubai and the technician can only find one of the three components needed to fix it.  does anyone know of a good site I can order what i need to fix this and also the names/model number/part ID? I need to buy online and have it sent to dubai.
attached is a picture of whats not working and needed apparently. thanks for any assistance!


DBX128_parts_needed.JPG




doulos24 said:
Does anyone have an actual dbx 128 schematic or service manual? I bought one off ebay in "working" condition  and I can't seem to get it working. I measured the voltage from pin 4 and 7 of the OA1 lm301an. and I'm reading 170mv dc I'm guessing it's the voltage regulator chip? or that transistor that needs changed I ordered both parts. but a schematic would be very nice to have 

I ordered a NTE128 for the to TO39  transistor and the regulator MC1723CP.

dbx1181_zps15345c70.jpg
 

I started modding this before I testing if it was good :( A big mistake I won't make again. I changed out the electro caps in the psu with newer ones. I socketed all the opamps.  I removed the blue tantilum caps  in the psu. I even changed out the diodes. 
If anyone else has anything else I can try please feel free to let me know. 

thanks
Click to expand...
 
Hiya

I can't see what those components are from your picture but Farnell is a good place to start sourcing.

http://www.farnell.com/distributors/unitedarabemirates_dgm.htm

Seems they have people in Dubai as well. Good luck and post more specific component numbers if you want more help identifying them but usually a google search will get you something. Ebay is also good for obscure components.

Gareth
 

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