dbx 162 schematic

any body have a 162 schematic in electronic form that is high rez enough to read.

i found one posted in the lab but it was unuseable.

my 162 passes audio in bypass, as soon as you engage the circuit all audio dies.

nothing comes out at all.

power looks good, all solder joints look good (i don't have a magnifying glass) .

need a schematic to continue.

thanks for the help!!

I think I have one kicking around from when I got mine. Let me see if I can dig it up when I get home tonight.

-dave

I am also interested.
Thanks,
Peter

http://avensonaudio.com/tech/DBX/

Hopefully those are pretty clear. It's been a while since I scanned all that stuff so I don't remember.

Thanks, Brad!

The problem with many DBX-manuals is that their schematics are very badly printed - almost unreadable even from original manual..

For some of the parts, you'll have to use qualified guesses..

Jakob E.

thanks brad. that is very helpful!!

> a 162 schematic in electronic form

I have a genuine 162 manual in my hand. (This is the circa-1981 black-face stereo compressor/limiter, right?)

That whole complex schematic is printed not much bigger than my hand. The other version cited is actually pretty good, considering. If you have a specific squint-question, ask here and I'll squint. If you really need a better copy, I can try, but the tiny printing will be a challenge, and the file size might end up gigantic to be sure of covering every blurry detail.

> passes audio in bypass, as soon as you engage the circuit all audio dies.

Some history would help. Did it work last night, not this morning, and no thunderstorm? Or did you just get it off eBay and it was sick when you opened the box?

BOTH channels? There isn't a lot that can foul-up both channels. Check your supply voltages again. OA3 pin 7 at +15.0V, OA3 pin 4 at -15.0V.

If supply is perfect, pull both VCAs (PC7 and PC8) and jumper each socket pin 3 to 5. That is equivalent to VCA at unity gain, and will prove that the basic audio path works (or not).

Be sure there is nothing ugly hanging on the Quad Connector at the back (it should be unconnected unless you know what it is for).

It might be possible for the anti-thump (all those FETs) to stay Muted and kill output, but odd that both channels could be blown at once.

history....

i acquired this unit from a friend that took a long term job in france. it's not a 220 PSU and so he intrusted it to me if he ever returns to reclaim it.

he said it might have issues as he hadn't used it in years.

so, that's as much as i know about it.

both channels pass audio in bypass, release the bypass switch and they both go silient.

J-

I noticed over at PSW that you got it fixed. What was the culprit?

-dave

the strangest thing EVER.

(i didn't fix it)

first off, i tested the 24 volt supply and it all looked good.

i couldn't find a bad solder joint so i called my tech.

here's what he found.

first off, the 15 volt supply was dead. well i didn't have a schematic so i didn't even now there was a 15 volt supply................color me stupid i was looking for something simple (cracked solder joint)

he fixed that thinking it just went south. 2 transitors, 1 chip, and four resistors. it popped again.

he started looking for shorts......

there are about 5 daughter boards plugged into the top of the mother board. i'm guessing two are the VCA's.....not a clue as to the other three.
two are the same, two more are the same and there is a fifth different from both.

ok. after looking and looking, and pulling cards and so on. he pulled two of the same cards (must have been desperation at that point)

the short went away. confused (since he pulled both of those cards idividually before) he took a closer look at each card.

turns out...............the same exact tant cap on each card shorted

seems really odd for a tant to short in the first place. but two of them, in the same position on two different cards???????

that's just weird.

anyway, it's up and running and kicking butt.

[quote author="j.hall"]seems really odd for a tant to short in the first place. but two of them, in the same position on two different cards???????[/quote]


no, thats what they do when they go bad, they short. When I went through all the opamps in my console, there were consistent shorts in the same two power decoupling tants across the lot of the cards. The audio tants were mostly fine, but the tants on the power rails were about half shorts.

dave

i understand that tants short when they blow.

i just thought it was odd that the tants blew at all....apparently it's common.

> there are about 5 daughter boards plugged into the top of the mother board. i'm guessing two are the VCA's.....not a clue as to the other three.
two are the same, two more are the same and there is a fifth different from both.

2 VCAs 210, each has a quad of transistors wrapped in aluminum.

2 output amps 230, each has two beefy power transistors and a (bootstrapped) opamp.

1 Dual RMS Detector 225.

Shorted Tantalums? Ummmm, mine is in mission-critical duty..... wonder if I should be proactive, or let a crisis happen......

without taking the thing back apart i can't tell you which boards it was.

i can tell you this.

the tants that failed, if you look at the component side with the multipin connector facing down (like it plugs in)

the tants were in the lower right corner. obvioulsy PSU related.

If it were me, I'd replace the tants in decoupling positions with 'lytics. I saw many different pieces of gear disabled by shorted PS decoupling tants when I worked in the repair biz. So you have to replace the 'lytics every twenty to thirty years... big deal :wink:

> without taking the thing back apart i can't tell you which boards it was.

Pointless. The 162 is such a bear to get open, and so easy to work in once opened, that I would just replace anything Tantalum in one go.

There are complex political reasons why it makes sense to keep my feet on my desk until someone complains of smoke..... then I might swap-in a Beringer Composter (it don't suck much) and eBay the sick/re-capped 162.

[quote author="PRR"]There are complex political reasons why it makes sense to keep my feet on my desk until someone complains of smoke...[/quote]

Oh man, do I ever hear you! Sometimes management and bean-counters need gentle reminders of the value of tech support.

[quote author="PRR"]There are complex political reasons why it makes sense to keep my feet on my desk until someone complains of smoke..... [/quote]
Amen brother!

I was famous in my coin-op tech days for presenting invoices that showed the difference in cost between a natural failure mode and a created one...."original repair would have been $50, but your in house solder monkey did $400 more damage chasing symptoms and not cause" or "if you had brought it to me when you first noticed that sizzling sound I would have replaced a $39 flyback transformer instead of a $600 monitor"

I know it's only a paycheck for most in the electronics biz, but it seems the average is to want it done as cheap as possible, without regard to how long a half-assed repair will last (or how much more it costs in the long run) vs. the few that are smart enough to trust a good tech or engineer to do it right to the best of their abilities no matter what the cost.

The interesting thing is that the companies that wanted me to do it right are still around, the ones where the cheapest repair was king are all gone, folded or sold.......

Best!

SmashTV

well......money doesn't grow on trees.....HOWEVER, i've always prefered my gear to function properly.....or in some cases better then it did to begin with.

i can do a certain amount of chasing.....but i know my limits and i know not to go jacking around with something if i haven't a clue.

i paid 100 bucks to have my 162 fixed, and considering i got it for free.........i figure i'm still WAY ahead of the game.....and hey, i get to actually use it now.

to me, tech bills are just part of studio ownership......some cost more then others.