GSSL HELP THREAD!!!

[radiance]

@ J.Hall: Try swaping all IC's from the left to the right channel.
That may answer your question. I hope you have everything in sockets...

 

[j.hall]

i did that....nothing changed

right channel is still passing audio about 30 db down or more.

 

[Greg]

hmm...

well if your rails are fine and all the ICs are fine, then perhaps a resistor/cold joint check in the right channel is next :? The problem is probably some passive component I guess.

These cases are usually such a pain in the...

 

[j.hall]

yeah....major pain

as far a blown component, everything looks fine.

all solder joints are nice a shiny and looking good, but i haven't started testing them.

figure i'll just pump in 1k tone and track it through with an O-scope.

 

[j.hall]

ok.....i located one problem, but i'm not sure if this is the actual problem or just something i caught while checking the unit out.

look at the attached jpg.

if the circled 15k resistor was accidentally switched to a different value what effect would that have on this circuit. (right when i found it i realized i was late for a meeting, didn't measure it, but it looked like a 10k, maybe a 100R.....can't remember the colors that close right now)

http://download.prosoundweb.com/~j.hall/ssl_sch.pdf

 

[Ian MacGregor]

If that resistor is lower than 15K, the gain that the op amp is giving will be less than unity. I would guess that it is something low like 100R, which would explain how you are hearing one side down ~30dB or whatever. Definately replace it with a 15k and take a listen.

Ian

 

[j.hall]

it was a 120R and once changed to it's proper value of 15k the whole thing is rocking.

thanks!!!

 

[fum]

So how long do you guys normally let yourself cook on a problem before checking back and asking advice? :roll:

I'm still laborin over my SSL's, they've been on the bench a few weeks. I'm ready to be done with them, so that I can put them to use =).

I try to keep a rotation of projects to work on, so I don't burn myself out on one thing ( it can be frustrating to bang your head against the same wall day in and out, I do that enough already), but perhaps I should check in with what I've been up too on these.

I think the majority of my problems are a poor PCB etch. This was the first board I etched ( over a year ago), and the traces ended up a little blurry. I've spent a bit of time tracing signals and cutting improper connections. Found about a half dozen of those.

One of them works well, but has this crosstalk(described above) that I can't track down, as I can't seem to get my scope to show me whats goin on. I've used the scope with success on projects previous, but something I'm doin aint right(the scope is fine, I'm thinkin it's how I'm using it).

I swapped the main boards between the units, and it helped me isolate better where some problems were. The unit that works fine, does not when I put it in the other unit, which told me there's a problem with the control panel layout (either pcb or wiring). And the one that doesn't work fine, still doesn't work fine in the other unit, which tells me there's still something wrong with the main board too (besides it's control panel ).

Since I can't get the scope to tell me what I want, I've spent some time checking resistances to ground from points in the circuit ( comparing the two), and it has helped track down some problems, but seems somewhat arcane and time consuming.

Supply voltages are a all good. Audio signal passes through. I'm still looking into different stuff, but suggestions are welcome

:grin:

ju

 

[fum]

Hah! Finally some success. My Fluke checks frequency, so I started using that to trace signal through. Managed to eliminate the crosstalk, and have one unit up and working correctly. Again, just a bad etch, with traces connecting where they shouldn't be ( albeit one of them I could not see, even with a magnifying glass, but the continuity check doesn't lie)

One down, one to go :green:

ju

 

[Steve Jones]

I'm sure this has been asked before, but I can't find it - is it OK to use a THATS 2180LC for the sidechain VCA as well as the main GR VCA's? or does the sidechain VCA have to be a diferent type?

 

[Ian MacGregor]

totally fine steve

 

[Steve Jones]

Thanks MacDude! :guinness:

 

[mich]

hi all

trying to troubleshoot my ssl clone ,got some problems,maybe someone can help....

ive got all voltages right (+/-15 and +/-12 )where it should be...

the unit is passing audio in both channels (clean & good) but not compressing at all.the meter (100 uA with the 330R resistor) is not reacting to nothing.. actually none of the controls is working properly.

one funny thing- the make up gain pot-when turned to 0 resistence is turnning the power led off..

also checked ac signal coming in on pin 7 of tl074(o.k) but nothing on pin 8......................any ideas?

im also confused with the meter resistor-having read somewhere that it should be 20k instead of 2k for a 100uA meter (posted by jakob) and the schematic calls for this 330R...

thanks.

 

[mich]

sorry, i didnt mention i am using verbos dbx 1252 vca's.

 

[gyraf]

Mich,

Check for shorts on your control-panel board - specially from makeup-gain pot wiper to +/0/- rails.. Check value of the resistor in series with makeup-gain pot wiper.

Have you tried reading through this thread? I think we've had that symptom before..

Jakob E.

 

[mich]

thanks jakob, ill check that.
yes, i read through the whole thing....(19 pages)....

 

[mich]

that was the fastest troubleshoot ever....thanks jakob. :grin:
the wiper was definitly touching the 0 rail- through the bypass switch that was conected upside down - A and C points of the bypass switch- i think its wrong on the schematic? anyway now the meter is working but ive got distortion when threshold is high....ill go back to reading this thread...

 

[ChrisA]

So, I've built two ssl clones that came out great...Thanks Jakob and to everyone else here...this forum is amazing.

I was just trying to finish up my third clone and ran into a strange problem I haven't come across before...It passes audio fine with the threshold wie open and gain all the way down... i'm also sure all of the vcas are working and in right, but its doing some very strange stuff.

The main weird symptom is when I turn the make up gain pot it creates a spark inside and the pot actually starts to fry...the threshold pot isn't really working quite right either and it is intermitently compressing....when it does it is also distorted...

I've started checking all the resistors and can't find any mistakes yet swaped out all of the chips and its still giving me the same problem...

from these symptoms...any ideas of the best place to focus on where the problem might be?

 

[gyraf]

Chris,

Check - like Mich did - for shorts from pot wipers to -/0/+ rails. Check pot wiper series resistors and values. Try measuring what voltages you get at the pot wipers when you turn them - the schematic gives a good clue to what the voltages should be.

Jakob E.

 

[mich]

hi again.

still troubleshooting....

now bypass works,make up gain works and the meter is responding,but
on fast attack time its cliping like crazy..& i hear no compression-only at fastest attack and high threshold there is some compression hapening-but with distortion.

someone have any ideas on where to search?...

p.s: i also noticed that the tl072 is reversed on the schematic or the pcb,but i guess its only the stages numbers on the chematic.