calrec PQ1549 help thread

[jasonallenh]

I think the frontpanel is from pusherman: Gyraf Calreq EQ Stereo – 19″ 2U Anodized Black Aluminium Panel – Pusherman

This general design has existed for a while. I'm almost certain it wasn't originally a Pusherman creation, but the FPD file is out there. I have the same one with my own changes/logo

 

[AudioPro]

Hey guys does anyone ordered pcb's from Jacob's gerber files?Since the format is old the drill holes are not appearing for pcb fabrication.Is there any solution?I've looked trough the comments but did not encounter similar problems.

 

[JMan]

This general design has existed for a while. I'm almost certain it wasn't originally a Pusherman creation, but the FPD file is out there. I have the same one with my own changes/logo

Do you happen to know where the FPD might be floating around? I have been thinking about trying this project, but would prefer to tweak the panel aesthetics slightly (as you did).

 

[estocastico7]

Hello,i have tbe pcbs to make this projects and i go to take all the components in banzai music,but i dont see the dual 100k potentiometers neg log.
I see that there are potentiometers stereo,but i dont know if they work.What is neg log???type c potentiometers??
In tayda i found this unit:
https://www.taydaelectronics.com/100k-ohm-anti-log-dual-taper-potentiometer.html
Thanks a lot,ita a great project,but i have problems with this pots and switchs.Thanks!

 

[gyraf]

dual=stereo

TypeC= neg.log = reverse-log pots

 

[estocastico7]

dual=stereo

TypeC= neg.log = reverse-log pots

Thanks a lot friend!

 

[janczmok]

I tried to power my built (gyraf pcb) with the lab PSU, with 15V300ma, no problem, same with 16&17V - but with 18v it jumps into OVP.
Any thoughts where to check ?

 

[gyraf]

what is ovp?
what opamps did you use (rated for +/-18V?)?

 

[jasonallenh]

Hi Frank,

that´s what I did before already. But it´s always good to do it twice.

I sloved the problem meanwhile.

It was a short around the 6n8 by IC5a. Now the other half of my calrec is working too and it sounds very good.

I will do more tests and compare it to other EQs soon.

Thanks for help.

Cheers

Can't remember if it's mentioned in here or not, but one of the clear signs of a short in this circuit is that the IC will get verrrrry hot. I may have had this exact short, IIRC. There is an IC with a couple traces that are very tight and easy to short.

 

[jasonallenh]

what is ovp?
what opamps did you use (rated for +/-18V?)?

Maybe 'overload protection?'

 

[JMan]

Maybe 'overload protection?'

That would be my guess as well -- over-voltage protection

 

[janczmok]

Sorry, yes, my bench PSU has OVP (over voltage protection).
There is no measured short between +/- and GND.
The ICs i use: LM833N (rated +/-15v) , Elcos are rated 25V, but the tantals are rated 33uf/16.
More or less according the order list.

 

[Walrus]

Sounds more like Over Current Protection than voltage.
Unless the power rails have series resistors inline with the opamps, then the power supply must be limited to 15 volts or lower.

Edit: I see that the LM833 is rated for up to Plus/Minus 18v rails. But it still would seem that your bench power supply is going into current limit not voltage protection.
What is the make/model?

 

[Harpo]

... Elcos are rated 25V, ...

When you apply +/-18VDC, the leftmost 22uF Elco sees 36V. For sure a higher voltage rating required.

 

[janczmok]

Bench Power Supply is a RigolDP832, fed Voltages to the PCB as 15/16/17/18V and 400mA - with OVP and OCP.
I get the message with 18V - i realized i do have the OVP set to 18V, this cannot work. set OVP to 18.5V and now everything works *sigh*

 

[janczmok]

When you apply +/-18VDC, the leftmost 22uF Elco sees 36V. For sure a higher voltage rating required.

For the moment, it seems to work - however you are correct. But according to parts list (Gyraf Audio - Public Domain Circuits - DIY Calrec EQ - Parts list) tantals are rated 16V, same as Elcos. - but i check my parts bin and fix those ... But you are reffering to those:



Update: 22uF / 50V should be sufficient, do you agree ?

 

[gyraf]

yes

 

[Harpo]

For the moment, it seems to work - however you are correct. But according to parts list (Gyraf Audio - Public Domain Circuits - DIY Calrec EQ - Parts list) tantals are rated 16V, same as Elcos. - but i check my parts bin and fix those ... But you are reffering to those:

View attachment 121861

Update: 22uF / 50V should be sufficient, do you agree ?

22uF/50V will be sufficient. (the two marked caps are not in question, the leftmost cap below the shelf pushbutton is in danger and maybe/probably already blown.)

 

[janczmok]

22uF/50V will be sufficient. (the two marked caps are not in question, the leftmost cap below the shelf pushbutton is in danger and maybe/probably already blown.)

Okay, you are referring to the 22uF left of IC 11b i assume or which one ?

 

[Harpo]

Okay, you are referring to the 22uF left of IC 11b i assume or which one ?

yes, with +/-15VDC supply 30VDC across this cap, with +/-18VDC supply 36VDC across this cap.