calrec PQ1549 help thread

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Hey Everybody,

I'm finally getting around to putting together a single channel of the PQ1549. I'm having a lot of trouble getting it to work and am wondering if any of you have suggestions...

I've narrowed it down to the negative power rail. The PSU (I'm on my second and it's an old lab supply) is working fine. I'm getting +/-15 until I plug into the pcb. At that point the negative side drops to around -1 volt. I've checked and re-checked everything that I can think of along the power rail. The positive side stays at 15 and the positive voltage shows up at pin 8 of each of the ic's. The unit passes no audio (except in bypass) but the led lights both green and red when the switch is pressed. I've replaced the diode and the caps that are right off the power supply and checked continuity and I'm stumped...

Any ideas?...

Thanks a bunch.
 
Hello

I am building a singe channel calrec into a rec.channel. Got a 15 v PSU.

I pluged the PSU in with wrong polarity first, fried one 22 uf. Got that fixed, but no there are no power after the diodes. Can't find them in the schematics. Is it possible that they are wrong rotated?

Andreas
 
Thanks for fast reply Jacob

Sorry, but I been looking trough my electronics books and I don't understand what the diodes do.

I have traced trough the whole unit, but can find any errors. Checked caps, resitors and tried to look for shorts. I have changed the diodes and they are rotated the way the PCB says. Something is defenetly wrong.

When I connect power and messure voltage on the power ins on the calrec pcb the voltage slowly, but stedly goes up from 4 volts on both + and-. After about 3 minutes the two 22 uf caps explodes. It looks like the are caring them selfs up.

Any ideas for where to look?

A
 
When I connect power and messure voltage on the power ins on the calrec pcb the voltage slowly, but stedly goes up from 4 volts on both + and-. After about 3 minutes the two 22 uf caps explodes. It looks like the are caring them selfs up.

Then your supply voltage is either FAR too high - or you've connected powersupply with reversed polarity - or you've reversed polarity of the electrolytics.

Check, check, and recheck..

Jakob E.
 
Thanks again

I have to thank you for this build.

I still wounder what the diodes do, can you tell me?

I will check, check and recheck

I now have gotten the voltages steady but at only 8 volts. the supply when not connected is 15,1 on both + and -

Have checked polarity on the caps, now I'll check for shorts
 
I still wounder what the diodes do, can you tell me?

They protect all the IC's from wrong polarisation of the PSU. Had it not been for those, then ALL your IC's would be dead by now.. And they also helps to filter psu a bit.

Jakob R.
 
im planning to build one stereo unit.

is there any point using switches instead of pots? i have my hands on decent priced 2x24 / 4x24 switches.

how can i calculate the resistor values to match the potentiometer curves or better yet, calculate resistor values for certain frequencies/decibels/q etc?

thanks,

eero
 
how can i calculate the resistor values to match the potentiometer curves or better yet, calculate resistor values for certain frequencies/decibels/q etc?

It's a standard state-variable filter - you should be able to find formulas in any filter-cookbook

Jakob E.
 
dude.. 2 and 4 by 24 switches.... at a decent price? is this that EU online store with guitar fx diy and stuff like as well? because i can never remember that site

billy
 
Hi There,

I am getting problems in my Calrec eq. I have built 3 channels & all are sounding like motor bike ( low freq. oscilation) with no input. I have checked my PCBs with schematics & found some changes, Some reversed Caps & some diffrent resistances. Two 1M resistances are also wrongly placed.

Can anyone send me the correct PCB layout & schematics?

Thanks & Regards

Dinesh
 
okipoki! im building this one chanel calrec eq as my first bigger thing and hmm... till today only the bypass sounded but i found this little "link or set point" (i think it said) and i put a little link there and the thing started sounding.

ive had it on without this link for some time... can this have damaged any components? the thing has a bussing sound in the highs now and the sound gets distorted when i tweak on a line signal from a synth, not really sure i wiered things the right way on the ins and outs and ground and ooh... seems like youre on your own after the PCB´s

to here! but not further! or its just things that everybody should know...

are there any threads on this? i mean... it should be!

/jonas
 
[quote author="Jonas K:strand"]... i put a little link there and the thing started sounding. ive had it on without this link for some time... can this have damaged any components?
I don't think so. You just didn't pass the signal from one point in the circuit to another... The link was meant for Hi-Lo pass filter insert point or a gain stage if i remember well from the posts that i had read...

....the thing has a bussing sound in the highs now and the sound gets distorted when i tweak on a line signal from a synth, not really sure i wiered things the right way on the ins and outs and ground and ooh...
Shouldn't be sounding the way you described...Are you overloading the input of the Calrec? What about input resistor,"You could try changing the two 10K series resistors at the balanced input to something larger - say 22K should take you down 6dB etc.."quote-Gyraf... Try to look for the misplaced components, shorts of all kinds....Magnifying glass with a lamp is very helpful for this sort of problems, if you are not using one already....

...seems like youre on your own after the PCB´s
as you can read you are not

are there any threads on this? i mean... it should be!


cheerz

/jonas[/quote]

use the "search" function it is very useful. I know very little about electronic, almost nothing, but reading the forum and using the search function i've complited the Calrec project with success.
 

Latest posts

Back
Top