gar381

calrec PQ1549 help thread
« Reply #60 on: November 16, 2005, 07:50:09 AM »
thanks Jakob

GARY
RETIRED.....  from 51yrs in Show Biz

gar2520, gar1731,garAM10,gar918 DOAs at  http://capi-gear.com/catalog/index.php?cPath=71_72
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calrec PQ1549 help thread
« Reply #61 on: January 31, 2006, 05:15:14 PM »
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.
+=G=+

gyraf

calrec PQ1549 help thread
« Reply #62 on: February 01, 2006, 02:51:28 AM »
Your -15V obviously is shorted to something. Reversed opamp/diode/electrolytic?

Jakob E.
..note to self: don't let Harman run your company..

anneflyr

No power after the diodes
« Reply #63 on: February 21, 2006, 06:44:23 PM »
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

gyraf

calrec PQ1549 help thread
« Reply #64 on: February 22, 2006, 07:55:13 AM »
If you're asking if the layout is incorrect, then no. Look at the pcb layout in the pdf-file - it should be quite clear what it does.

Jakob E.
..note to self: don't let Harman run your company..

anneflyr

hey Jacob
« Reply #65 on: February 22, 2006, 09:57:41 AM »
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

gyraf

calrec PQ1549 help thread
« Reply #66 on: February 22, 2006, 10:18:18 AM »
Quote
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.
..note to self: don't let Harman run your company..

anneflyr

calrec PQ1549 help thread
« Reply #67 on: February 22, 2006, 05:56:17 PM »
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

gyraf

calrec PQ1549 help thread
« Reply #68 on: February 23, 2006, 05:33:00 AM »
Quote
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.
..note to self: don't let Harman run your company..

EEMO1

planning a build
« Reply #69 on: September 14, 2006, 04:10:44 AM »
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


gyraf

calrec PQ1549 help thread
« Reply #70 on: September 14, 2006, 04:33:58 AM »
Quote
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.
..note to self: don't let Harman run your company..

EEMO1

hey
« Reply #71 on: September 14, 2006, 04:43:16 AM »
thanks, so it's possible. :D

calrec PQ1549 help thread
« Reply #72 on: September 14, 2006, 04:47:50 AM »
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

EEMO1

hey
« Reply #73 on: September 14, 2006, 05:20:59 AM »
yeah, it is. one of my local stores or at least used to be... no pickup anymore.  :sad:

gyraf

calrec PQ1549 help thread
« Reply #74 on: September 14, 2006, 05:47:24 AM »
A link??
..note to self: don't let Harman run your company..

EEMO1

here's the link
« Reply #75 on: September 15, 2006, 02:11:18 AM »

dinesh

calrec PQ1549 help thread
« Reply #76 on: February 13, 2007, 03:48:48 AM »
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

gyraf

calrec PQ1549 help thread
« Reply #77 on: February 13, 2007, 04:22:37 AM »
The stuff on the gyraf site is already correct and is been kept up to date. check your powersupply for oscillation, and check your wireing.

Jakob E.
..note to self: don't let Harman run your company..

calrec PQ1549 help thread
« Reply #78 on: March 27, 2007, 02:39:08 PM »
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

syn

calrec PQ1549 help thread
« Reply #79 on: March 27, 2007, 03:02:54 PM »
Quote from: "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


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.


 

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