500 series Sontec / GML type eq

[kosi]

http://www.thedonclassics.com/#all-kits

 

[thomasdf]

Stupid me! Thanks!!
Thomas

 

[Studio Mollan]

I just finished my two kits and they do sound amazing!

There's two things though i cant get my head around.

1.  A few of the trimpots, the ones in the filter section, won't zero out the voltage across the test points. I'm between 4 and 50mv on a few of them. The filters sound good though after a very short first test.

2. the Modules are about 2mm to deep to properly fit my desk. An vintage API 2488. Anyone else had this issue? The modules are floating above the top of the adjacent modules when the connector is fully in. I have double, and triple checked that I've assembled the front panel as in the manual. If i moved the top nuts to the other side of the front panel i might get a snug fit. Also the knobs are all about 2mm above the face plate when pushed in fully.

Also i had to connect pin 5 with pin 13 to get it working. Don't know if this is related to me using them in a desk as opposed to a 500 rack.

/
Emil

 

[jensenmann]

Did you use 25turn precision trimmers or single turn versions. With precision trimmers I could calibrate the servos down to the 10uV region.

 

[Studio Mollan]

Hi,
I used the ines from the BOM. 25 turns seem right from what I remember. They are not single turn. At least 10 turns.

Did you use 25turn precision trimmers or single turn versions. With precision trimmers I could calibrate the servos down to the 10uV region.

 

[Rogy]

Deleted...

My issue appeared to be a measurement setup issue; my four units are working flawless!

Best Rogy

 

[benewell]

Hi There,
Long time lurker, first time poster, I purchased 2 kits last summer and they are absolutely Wonderful!

Unfortunately only the BOOST function for each band works on one EQ... I'm not able to cut at all. Has anyone experienced this, or have any hints I could try to isolate the issue?

I've:
- reseated the ribbon cable
- made sure TPS 1-TPS 2 read 0mv
- tested all switches and pots work mechanically, and are easy to switch/rotate
- tried different slots in 500 series rack

And I still have the same issue of not being able to cut with any band. My other EQ works flawlessly however. Any help or suggestions are greatly appreciated!

Best,
Brian


other notes: I also swapped R69's for 51k as per suggested earlier in the thread, getting a nice gentle +-, instead of the full 12dB. The only other issues I noticed are the mv's at each frequency band test point are slightly off (anywhere from 2-50ish similar to another user), but that doesn't seem to affect the functionality of the unit.

 

[Zander]

For those who used Pier Paolo's APP992, did you adjust or leave out some components.


Zander

 

[Studio Mollan]

Hey,
There must be an issue round about here in your EQ.
Check for cold solder joints or missing, faulty components. the ribbon cable is a candidate,. Try the one in the functioning unit, or check for continuity with a DMM. Truly great eq's!

Hi There,
Long time lurker, first time poster, I purchased 2 kits last summer and they are absolutely Wonderful!

Unfortunately only the BOOST function for each band works on one EQ... I'm not able to cut at all. Has anyone experienced this, or have any hints I could try to isolate the issue?

I've:
- reseated the ribbon cable
- made sure TPS 1-TPS 2 read 0mv
- tested all switches and pots work mechanically, and are easy to switch/rotate
- tried different slots in 500 series rack

And I still have the same issue of not being able to cut with any band. My other EQ works flawlessly however. Any help or suggestions are greatly appreciated!

Best,
Brian


other notes: I also swapped R69's for 51k as per suggested earlier in the thread, getting a nice gentle +-, instead of the full 12dB. The only other issues I noticed are the mv's at each frequency band test point are slightly off (anywhere from 2-50ish similar to another user), but that doesn't seem to affect the functionality of the unit.

 

[benewell]

Thank you for the response!

Unfortunately I have been busy, but will try those suspects you suggested soon! I'm noticing that on my working EQ I added the optional C18a, as well as ccomp4 and compIC5. As I am a bit of a novice with circuit design and it was mentioned as optional/TBC, I wasn't sure if they were necessary... but am considering adding them to the non-functioning EQ.

Would it be beneficial to have those as well?

EDIT: Found the issue! There was a nick along the top of the Top PCB preventing signal from CCW on the Ribbon Cable to R48. Good news, everything looks neat and all solder issues/mv problems are gone with done soldering, I just wish I noticed this earlier hah Bad News is now I have to repair the trace alone the top, which shouldn't be too hard but I guess there's a first time for everything!

Thanks Studio Mollan for pointing me in the right direction!

[/quote]

Hey,
There must be an issue round about here in your EQ.
Check for cold solder joints or missing, faulty components. the ribbon cable is a candidate,. Try the one in the functioning unit, or check for continuity with a DMM. Truly great eq's!

 

[Spino]

bump this.

and also, nobody commented on the sound of the 250eqs with those in.

For those who used Pier Paolo's APP992, did you adjust or leave out some components.


Zander

 

[Studio Mollan]

Hi,
Yes you should fit them all. C18a isn't crucial, but recommended, but the Ccomp4 and compic5 should be fitted.

Thank you for the response!

Unfortunately I have been busy, but will try those suspects you suggested soon! I'm noticing that on my working EQ I added the optional C18a, as well as ccomp4 and compIC5. As I am a bit of a novice with circuit design and it was mentioned as optional/TBC, I wasn't sure if they were necessary... but am considering adding them to the non-functioning EQ.

Would it be beneficial to have those as well?

 

[benewell]

Good to know!

I've fitted Ccomp4, compic5, and C18a, as well as found the issue (broken trace at the top of the PCB before R48). Both EQ's are back up and working flawlessly  ;D

Thank you Studio Mollan!

Hi,
Yes you should fit them all. C18a isn't crucial, but recommended, but the Ccomp4 and compic5 should be fitted.

 

[Studio Mollan]

No problem dude, Glad they're working now!

Good to know!

I've fitted Ccomp4, compic5, and C18a, as well as found the issue (broken trace at the top of the PCB before R48). Both EQ's are back up and working flawlessly  ;D

Thank you Studio Mollan!

 

[Zander]

SOLVED. David suggested to try this under its intended load. So I used a 600 Ohm (he calculated that for me ) resistor to ground from the negative filter rail. The zener is working just fine. Thank you David.

I have both my sontecs set for +/-24v for the main doa and +/-18v for the filter rails. In both Vcc- is too low. -19.5 and -18.7. Vcc+ is fine. Combined this is over the max supply voltage of 36v.
I suspect the 6V2 zeners 5% tolerance. I changed them out with a few others. Which were all giving me to little voltage drop.
I think I have two options: 1) changing the zeners for new ones or order 7V5 zeners. 2) use the +/-16v voltage rails.

Am I overlooking something? Anyone here set up the power rails like I did? It’s option C in the manual.

Zander

 

[baslotto]

Hey guys!

Not sure anyone is still hanging around here but I just finished 2 of these great units and all the voltages and measurements were right before I passed music through them.

Once I did that I realized  that for one of the channels the BLUE gain knob won't do anything.

Can anybody help me figuring this out? It looks like all my soldering has been done correctly, I don't see any missing points.

I swapped the gain knobs modules to see if that affected the other module but it's not the knob module.

Any other measurements to help me identify where to start?

Thank you for any help.

Stefano

 

[Studio Mollan]

try using the ribboncable from the working unit. It might be a bad cable.

Hey guys!

Not sure anyone is still hanging around here but I just finished 2 of these great units and all the voltages and measurements were right before I passed music through them.

Once I did that I realized  that for one of the channels the BLUE gain knob won't do anything.

Can anybody help me figuring this out? It looks like all my soldering has been done correctly, I don't see any missing points.

I swapped the gain knobs modules to see if that affected the other module but it's not the knob module.

Any other measurements to help me identify where to start?

Thank you for any help.

Stefano

 

[baslotto]

try using the ribboncable from the working unit. It might be a bad cable.

OMG it was the ribbon!!!!!!!! These things sound insane!!

THANK YOU!! YOU NAILED IT!!!!!!!!

 

[Studio Mollan]

Glad to be of help! they are indeed fantastic!

OMG it was the ribbon!!!!!!!! These things sound insane!!

THANK YOU!! YOU NAILED IT!!!!!!!!

 

[Blackdawg]

Eyeing these hard. But my racks only do 16v..is that okay??

Edit: read the manual. Looks like I'll be good, however, does that mean I can still use DOA? or just ICs?