Dbx 286 repair

[CapLeaker]

Re: Dbx 286 repair

good job!

[falcontech]

Re: Dbx 286 repair

Good morning
I close the discussion as resolved, I waited a month for them to arrive, the problem was THAT4305, I ordered them from the parent company as a free sample and they arrived only yesterday, after having replaced all the chips on the board in the end they were those. .. the only thing I do not know is if only one was defective or all three because I replaced them all from the rush. That corporation sent them to me as a free sample because they are really hard to find. Thank you all for your help

[falcontech]

Re: Dbx 286 repair

Good morning
I give you updates, unfortunately with the improvised probe I could not understand much, on some ic I had both the input and the output, on some I had a distorted signal on others nothing, I decided then (given the low cost) to replace them all, at the moment I have arrived the 4580r and 074c I have replaced them and nothing has changed, the Lm339dg must arrive, the other two the that 4305 and lm3046m I could not find them in Italy, lm3046m is on ebay but it comes from china and I don't dare to imagine when they will arrive ... does anyone know if there is an equivalent? I couldn't find it and apparently it's out of production. As for that 4305 the only one to have it in order with arrival in June is mouser waiting for some news thanks

[Khron]

Re: Dbx 286 repair

https://sound-au.com/articles/troubleshoot2.htm

[falcontech]

Re: Dbx 286 repair

its better than nothing.

between today and tomorrow I will do this test, must it be done with the processor active or deactivated?

[CapLeaker]

Re: Dbx 286 repair

its better than nothing.

[falcontech]

Re: Dbx 286 repair

you need some sort of a probe, either visual like an oscilloscope or audible like high impedance audio probe of some sort.

ok then I will do so, in input I will put an audio signal, in output an amplified speaker with the hold connected to the ground output of the jack and with the signal I will go to inspect the inputs and outputs of the ICs. Tell me if this could work

[falcontech]

Re: Dbx 286 repair

you need some sort of a probe, either visual like an oscilloscope or audible like high impedance audio probe of some sort.

can you give me a link for the audio probe, to understand what it is

[CapLeaker]

Re: Dbx 286 repair

you need some sort of a probe, either visual like an oscilloscope or audible like high impedance audio probe of some sort.

[falcontech]

Re: Riparazione Dbx 286

I still think you should get or borrow an oscilloscope or something in order to see exactly what is going on inside.

BTW... on the block diagram there is a 6.5mm audio jack called insert on the back. Work and lube that jack a bit. If it isn't making any contact, nothing works on the compressor side either.

the insert is ok, possible there is no other way than with the oscilloscope? what do you mean by something like that?

[CapLeaker]

Re: Dbx 286 repair

I still think you should get or borrow an oscilloscope or something in order to see exactly what is going on inside.

BTW... on the block diagram there is a 6.5mm audio jack called insert on the back. Work and lube that jack a bit. If it isn't making any contact, nothing works on the compressor side either.

[falcontech]

Re: Dbx 286 repair

below is the description of the ic on the board, i have had a look and there are several op amps, i can't find that 4305 i don't understand what it is

which one do you recommend to start with?

[falcontech]

Re: Dbx 286 repair

i've found it's...https://cdn.badcaps-static.com/pdfs/...26bacfc613.pdf

[Khron]

Re: Dbx 286 repair

Do the "4305" chips have any other markings? 4305 sounds more like a production code (week 43 of 2005). Feel free to cross-check with the schematics I linked on page 1 here.

[falcontech]

Re: Dbx 286 repair

the pictures aren't clear enough to see what is printed on the IC's. Sorry. Download the schematic and the block diagram. You successfully eliminated the problem being at the input stage.
The problem is either the switches (not giving any audio to the compressor) or between the compressor stage and the clipper.
There aren't that many IC's on the board anyway... if you wanted to shotgun it...

below is the description of the ic on the board, i have had a look and there are several op amps, i can't find that 4305 i don't understand what it is

[CapLeaker]

Re: Dbx 286 repair

the pictures aren't clear enough to see what is printed on the IC's. Sorry. Download the schematic and the block diagram. You successfully eliminated the problem being at the input stage.
The problem is either the switches (not giving any audio to the compressor) or between the compressor stage and the clipper.
There aren't that many IC's on the board anyway... if you wanted to shotgun it...

[falcontech]

Re: Dbx 286 repair

the LEDs do not move, it will be a little difficult to find an oscilloscope, if they do not have a high cost I could decide to replace them all, maybe one at a time in order to identify the culprit, you could tell me from the photo which are the opamps thanks

[CapLeaker]

Re: Dbx 286 repair

so the problem isnt in the input stage. When you turn that bypass button to off and talk into the mic, are the 8 leds on the compressor moving? you may have to fiddle around with the two pots a bit.
I am thinking the problem is one of the op amps. Are you comfortable changing surface mount IC's? If yes, I guess you need to borrow an oscilloscope to figure out which IC is the culprit. Then you need to read the numbers of the IC's and find the spec sheet on the internet in order to get the pin out. Then test the inputs and outputs of each op amp and see where things go in, but nothings comes out.

[falcontech]

Re: Dbx 286 repair

with the processor in bypass mode, are you getting any audio out?

ok, without the processor inserted the microphone can be heard, even without 48 volts phantom ... so where can I find the problem?

[CapLeaker]

Re: Dbx 286 repair

with the processor in bypass mode, are you getting any audio out?