GSSL HELP THREAD!!!

[tree]

:shock: :shock: :shock: :shock: :shock: :shock: :? etc etc.
i've beenreading, re reading and metering all weekend, trying to make some troubleshooting sense on my own, but i seem to simply be over my head with this first build...that so far doesn't work....

Tree,

Try tracing the sidechain signal all way through to DC control voltage at the vca's..

Jakob E.

Used 1k test tone @ 0db for unit DCVolt Meter testing...my first dumb question is; Is it possible to "trace a signal" thru this kind of project with only a v.meter?

At Jakob's suggestion and from previous threads it looks like i should first look seriously at TLO74, Pins 1, 7, 8 and 14 in particular?

Pin 1; DC varies with signal level (via thresh) .24-.65
Pin 7; DC barely varies with signal, .01 -.02
Pin 8; DC varies with signal level, .01 to -.52
Pin 14; DC varies with level input, -.48 to -4.9

Pin 14; DC also varies with ratio selection;
1:2 ; -.47
1:4 ; -.14
10:1; +.16

when unit is in bypass
Pin 1; 2.01
Pin 4; 12.46
pin 7; .04
Pin 8; .01
Pin 14; -.45

I can't help think these are mostly awful low as readings?
I measured all kinds of other suggested DC points today, :shock: but since i don't know where i'm at already, thought i best start right at TLO 74 and ask for advice...with the usual apologies.
so...
What kind of trouble am i in so far???!!!!

thanks all.

 

[tree]

GOT IT!!!!!!!!!!

I idioticaly managed to put a 47k resistor where 47R belonged!!!!!!
In VCA section.
Didn't even catch it until my SECOND time thru checking ALL values AND after a SECOND time thru resoldering ANYTHING looking remotely suspicious.

The box sounds great, btw and
I've learned a ton along the way.

Thanks Chris, Drpat and of course, Jakob!
Your patience and help truly appreciated.

"CHECK AND RECHECK", indeed.
:green:

 

[chrissugar]

Hey Tree,

Glad your SSL is finally working.

There is one advice I can give to all DIYers and mostly to beginers. Although I build electronic circuits since I was 5 years old, I still do the PCB stuffing with great care. I don't trust my capability to decode colour code from resistors and also don't trust the colours from the resistors (I know, I'm paranoid), so I measure each resistor before I put it in it's place.
Look at the schem, look at the PCB, take the resistor, measure the resistor, put it in it's place and then check, and then check again. I know it is slow and seems crazy, but for me this method works and never had to troubleshoot one of my projects in the last few years.
I have to repair many things for others, and I hate to repair, so I try to do my best to not be in the position to repair my own projects.
Trust me, this method is much more rewarding even if you do it much slower and you are concentrated, than building the thing quickly and then to waste more time for troubleshooting.

chrissugar

 

[Flundran]

I'm currently troubleshooting my control PCB, measuring up values.

I'm having some difficulties measureing on some resistors allready soldered to the PCB. The voltmeter show an incorrect value. When I desolder the resistor from PCB and measure it, Voliá! The value is correct. What is the reason for this phenomena?

 

[martthie_08]

you only have to desolder one end of the resistor in question.

in general: when you measure resistance with an ohmmeter from point A to point B in a circuit, you are always measuring "the path of least resistance", when you are measuring a resistor for example and there is another resistor with the same value hooked up in parallel, you will get half the resistance reading of one resistor... not very scientific, but I think you get the idea?

 

[Flundran]

Ahh, ok, that cleared it up. Thanx martthie_08 :wink:

 

[drpat]

...

 

[Flundran]

Ok, I would need some help troubleshooting my first DIY compressor..

It's passing signal thru fine, both channels. Makeup pot work. But no compresson is going on and the meter is frozen in a postition slightly above zero.

Today I made a discovery: When I adjust signal level (on input) to a certain level I suddenly get a VERY gentle compression on the sound, and the meter is bouncing VERY gentle... The frame for the input signal is about 1-2 dB. When the input is above or under, the old symphtoms comes back.

This is an checklist based on something Jakob wrote on page four of this thread:

1.) Check that you have the needed +/-12V voltages present.

2.) Check that you have signal coming to your sidechain, TL074 pin7.

3.) Check that you have DC varying with signal at the output of the sidechain, TL074 pin8

4.) Check that pin 1 and 7 on the TL074 has DC varying with signal level as well as a superimposed DC signal from threshold (TL072 pin1) and makeup (TL072 pin7). These two are your VCA control voltages.

I've checked all above in my SSL, and it all seems correct. Any suggestions on what to do next?
I'm using two DBX 202XT's in this SSL b.t.w.

/Flundran

 

[higginsrob]

Can someone please help me I've finished stuffing my GSSL, now it lights up and passes audio, but no compression or metering (meter jumps at power on, then back to 0). The knobs don't do anything. I've checked the wiring, I have +/- 15V, and TL074 seems to be functioning ok, but where do i check next?

If anyone is in the LA area, I could buy you a few :sam:'s to take a look at it. I'm new to this so it's probably an easy fix

Thank you

Rob

 

[mfdu]

tree

thanks for your summation of points to check on the ssl - good timing.

i am only getting a very low level distorted signal out of my ssl.

have tried swapping vca's around to no avail. have not yet tracked voltages, but the +12/-12 is hitting the board fine.

in place of the 6.8uF cap of the control board, i used a 6.8uF BP electrolytic. is the fact that it is not a directional cap causing a problem?

(i used the same on my 1176's and suspect thats the problem there too)

read through the entire thread, but no mention of the fault i am experiencing.

any tips?

chris.

 

[gyraf]

chris,

There's only one way to do this: check for shorts, connections, and component values. Use a printout of the PCB layout for reference - and an ohmmeter (in continuity mode) to check for unwanted shorts.

Check that you have correct supply voltage on all appropiate IC supply pins.

Also try to isolate your problem to input- or output stage - you have the output of the input stage at one end of the two 47K resistors summing into the sidechain.

Jakob E.

 

[mfdu]

its the whole pelasure and pain thing, isn't it?

i do really love diy, but . . . no. thats it. i really do love it.

if i can get the weekend off the wife, i'll be up to my elbows in ssl bliss.

sionara.

chris.

 

[drpat]

Sounds like a weekend ON the wife would be much more fun anyways!

 

[mfdu]

cheeky

 

[dirk666]

An odd fault.

the threshold pot, turned clockwise , fades the power led down?

ive had this unit working before and took it apart to fix the inter PCB connections(wiich were intermitant)

got no sound now either

Just thought id see were to start looking. Any ideas?

 

[gyraf]

the threshold pot, turned clockwise , fades the power led down?

We've had that before - search the archives..

I don't remember the exact problem, but my guess is something shorting to the centre pin of the pot either on the control pcb, at the inter-pcb connection, or at the mainboard. Try tracing pot-centre-pin all way through and check for shorts to nearby things, gnd, and psu lines

Jakob E.

 

[Flundran]

My SSL is passing signal thru fine, but I can't get any compression. It seems there's something is wrong with threshold signal.

I have a question reg. CV to SC. Shouldn't this vari with threshold level? I've done measurements at TL072 pin 7, and the voltage here varies with audio signal, but is the same regardless of the threshold position.

/F

 

[gyraf]

..the two halves of the TL072 is switched on the schematic, pin numbers differ..

 

[Flundran]

Ok. At TL072 pin1, I get with threshold set all the way CW: 0.01V, and CCW: -0.01V.

I just discovered the fault when measuring resistances...

The two 47R in the SC section are in fact two 47K on my PCB!! I will run to ELFA tomorrow and buy the right components... Hopefully this will fix it.

/F

 

[Flundran]

Ok, now I have compression, and the threshold seems to work. But the compression (and gain reduction) is very gently, even with ratio at 10:1 and threshold at full anti-clockwise.

From TL072 pin1 I've measured the following voltages:

Threshold at CCW: -2.99V
Threshold at CW: +2.99V

Are these values correct?


/F