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Author Topic: DBX 160X  (Read 1348 times)

ilyaa

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DBX 160X
« on: March 14, 2016, 03:29:33 PM »
having some problems with this thing distorting -

wondering if anyone here has any knowledge of these units?

i know op-amps alright, but theres a lot of *s!!t* going on here......

specifically: im trying to figure out if U103 is powered okay. its got -12V at pin 4 and +17V at pin 7. shouldnt those both be +/-12V?

schematic: http://rdn.harmanpro.com/product_documents/documents/602_1324058489/160X%20Schematic_original.pdf
« Last Edit: March 14, 2016, 03:40:55 PM by ilyaa »

Vitrolin

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Re: DBX 160X
« Reply #1 on: March 14, 2016, 05:44:41 PM »
well it isn't powered ok + and - should be sort of the same, the both come from the unregulated supply
If you look at the connector J112 that shown as to be connected to P101 the positive 24V (Pin 6) is supply to U103 so around +/- 24V is good +17 and -12 very bad... if i have read the schem correctly there is a lot of long thin parallel lines..

Vitrolin

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Re: DBX 160X
« Reply #2 on: March 14, 2016, 06:03:20 PM »
i just realized that LF351 is rated max +/-18V so its very good that you don't have +/-24V :duh
ofcourse there is two voltage dividers R115-116 and R120-122 so maybe +/-12V would be ok
the voltage divider is affected by the push-pull transistors (no designators) and the components around them.
i would start by mesuring voltages at the top and bottom of the two dividers, if supply i good, most go to the transistor stage..

ilyaa

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Re: DBX 160X
« Reply #3 on: March 14, 2016, 09:32:33 PM »
okeey

so i was a little misled because of the separate 12 and 24V supplies (like you).

after some scopin around, i saw that the waveform at C142 and C242, negative pole, looked not so good. kind of a really gnarly sine wave. i replaced those two and the voltages are looking better!

now the positive ones are still a bit iffy - not a good looking ripple. ill switch those out next and we'll see if problem solved!

 

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