JayDee

calrec PQ1549 help thread
« on: February 26, 2005, 01:27:27 PM »
Hi,

don´t know if there is an official calrec help. If not this may be the first topic?

I am building a stereo calrec. One is sounds great, on the second the hi shelve isn´t working. When I track the signal at the freq pot (e.g.) there is no change in freq. All other band work quite well. What are the parts I have to check? No cuts , no shorts , both (left & right) look exactly the same.

cheers
jaydee


nrgrecording

calrec PQ1549 help thread
« Reply #1 on: February 26, 2005, 07:05:31 PM »
Hi.

If you bought alphastat potentiometers... i would check these first. I got at least 2 or 3 wrong assembled or labeled pots every delivery :?
Does the opamps IC3, IC5, IC6 gets power? If you used IC sockets you could try to change IC3,5,6 with IC10,11,12 if theres something different then, you could try to replace the opamps. (if you don't have LM833 at home, NE5532 will do)
Because you got one channel working... have you compared the resistor values (colour codes) with the other channel?

Frank.
Frank Röllen. www.energyrecording.de [FORUM · DIY WEBSITE · STUDIO]°°°° www.frontpanels.de [Engraved Frontpanels]°°°°

JayDee

calrec PQ1549 help thread
« Reply #2 on: February 27, 2005, 10:12:10 AM »
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

nrgrecording

calrec PQ1549 help thread
« Reply #3 on: February 27, 2005, 10:17:21 AM »
it works... super! :thumb:
Frank Röllen. www.energyrecording.de [FORUM · DIY WEBSITE · STUDIO]°°°° www.frontpanels.de [Engraved Frontpanels]°°°°

calrec PQ1549 help thread
« Reply #4 on: February 27, 2005, 09:55:02 PM »
I had mine working perfect, I went to put it into the box 2 days ago,
and darned if I didn't mess something up.

Now I've spent several days trying to figure out what I've done,
I had that thing fully tested too, everything worked. (I haven't built the other side I'm waiting patiently on the board, hopefully that will help me troubleshoot.)

But I sure am learning ALOT about filters.

All the features work still, it's just 2 filters are a hair too loud. The bypass isn't perfect, and I had the thing bypassing without a chain in gain.

calrec PQ1549 help thread
« Reply #5 on: March 01, 2005, 11:03:10 PM »
Ok, It's been several more days, I've tried swapping everything I can think of and I still have the same issue.
All IC's have power, I swapped all IC's.
Here is what everything looks like with the pots at null..

I can of course move the dip or the peak, the dip is the low mid, and the peak is mid-hi, the q, changes the peak crest.
[/img]
I can not drop the mid-hi lower than it is wrong in gain, only to about where it should be for bypass and I can't boost low and higher the same way.
I had this working so I had a flat bypass line, but I have fowled it up somehow, I have pretty much changed everything more than one, the back of the boards looking pretty used at this point.
but I can't seem to solve the basic problem, and I'm not sure how I introduced it in the first place, because, it was working, all it did was move around in a  box a little.
I have:
swapped with each other the 33u's.
swapped the 22p's
removed the pots, twice, moved them around.
replaced a switch.  
swaped with each other, then replaced completely the 22n's on
7a and 8b.
swapped with each other, then replaced completely the 68n's on 9a and 10b
swapped some 100n's.
swapped the 47ufs with each other.
freq is flat at 20k leading into 8a.
6k8 contains offending frequency. at volume (think it was by itself.)
removing 10k from bal - still seems to be the proper volume level between
bypasses relitivily.

Hopefully I can build anotherone right off the bat and be back to where I was, but, then if I break it again, I'm at a loss, there a few differences, in the rev's, but I figured I would have stubled on it by now and I'm pretty sure everything was in there right, cause it was working, so, what would cause it to go wrong like that?

paxworth

Calrec 8.1k resistor
« Reply #6 on: March 11, 2005, 01:25:21 PM »
I have searched all over mouser, newark, and digikey but I cannot find an 8.1k resistor.  Does it have to be exactly that number?  I have found an 8.2k resistor.  Would that work?

gyraf

calrec PQ1549 help thread
« Reply #7 on: March 11, 2005, 01:32:36 PM »
Yes.
..note to self: don't let Harman run your company..

paxworth

calrec PQ1549 help thread
« Reply #8 on: March 11, 2005, 02:52:59 PM »
Yes the number has to be exactly 8.1k or Yes an 8.2k resistor will work?

gyraf

calrec PQ1549 help thread
« Reply #9 on: March 11, 2005, 03:08:35 PM »
Yes, 8k2 would work..
..note to self: don't let Harman run your company..


calrec PQ1549 help thread
« Reply #10 on: March 23, 2005, 09:36:32 AM »
according to magnuses partslist you need


6x22u/16V radial
3x100u/16v radial

This fits with revision 4 as found on the Gyraf page, but on revision 5 you have to add one 22u and deduct 1 100u.  

I have marked the changes,,,and could someone help me with which way to turn the 22u ? the + must have been over a hole in the silkscreen.



Gustav

calrec PQ1549 help thread
« Reply #11 on: March 23, 2005, 02:33:39 PM »
I also noticed, and pointed out in another thread, that the 33uF are reversed on the board from orientatin in the schematic.

calrec PQ1549 help thread
« Reply #12 on: March 23, 2005, 04:04:53 PM »
Quote from: "thedug"
I also noticed, and pointed out in another thread, that the 33uF are reversed on the board from orientatin in the schematic.


ugh.
Ive really been trying to trace the schematic through the PCB, but I just cant, so I havent caught anything like that.

Could you point me the thread ? Im almost done soldering all this stuff up..

Gustav

calrec PQ1549 help thread
« Reply #13 on: March 23, 2005, 04:09:59 PM »
I'll check when I get home, but I am pretty usre that most of the 33uF caps are backwards as compared to the schematic.

For the 22uF it is the same as the 100uF. It just got rotated and downsized. Just from memmory I think it is + to the left of the board, i.e. connect to those contacts.  

Doug

calrec PQ1549 help thread
« Reply #14 on: March 23, 2005, 10:06:56 PM »
I think I've found other descripancies in the schematic. If this thread is correct, http://www.groupdiy.com/index.php?topic=75664#75664, then the default positions are show wrong.

Also, for a specific example of the 33uF tantalums, check out the tantalum on the just below the HQ switch for the low-mid. The schmatic shows the - terminal connecting to the 24K and 43K resisters. But the board has the + terminal connecting to those resisters.

calrec PQ1549 help thread
« Reply #15 on: March 24, 2005, 07:31:01 AM »
Quote from: "thedug"
I think I've found other descripancies in the schematic. If this thread is correct, http://www.groupdiy.com/index.php?topic=75664#75664, then the default positions are show wrong.

Also, for a specific example of the 33uF tantalums, check out the tantalum on the just below the HQ switch for the low-mid. The schmatic shows the - terminal connecting to the 24K and 43K resisters. But the board has the + terminal connecting to those resisters.


Unfortunately schematics are totally greek to me, so I can only go by the PCB drawings. Ill see if I can get someone at work to guide me through it when easter vacation is over. No hurry, Im still waiting for benkler to come back with a shipping price for a case.  :roll:

Gustav

calrec PQ1549 help thread
« Reply #16 on: March 24, 2005, 01:08:53 PM »
Ok.
This is for verification only, nothing is certian here.

Could someone verify that the red circles indicate discrepancies between schematic and PCB silkscreen, and the green circles indicate agreement ?
Im not done building yet, so I have no way of knowing what is correct, and I dont know wether to trust the schem or the PCB layout.




Gustav

calrec PQ1549 help thread
« Reply #17 on: March 24, 2005, 01:34:36 PM »
I'll try to have a look tonight.

I'd really like to hear what Jakob has to say because, people have built these based on your boards and they work.

Also, I have found other problems with the schematic too. Check out the 4PDT switches. The schematic says that they are in their default position, yet there are some poles that are connected to the wrong pin.

Doug

calrec PQ1549 help thread
« Reply #18 on: March 25, 2005, 03:06:42 AM »
Mine is together and working.  Both sides.
After mucho trouble with it. switchwise I ended up using panel mount
so I just used the same format accross and it worked.

Todo...

The gain is still wrong, if off = 0 db. then bypass = 0. then
eq in will = around +8db.  While this isn't a show stopper I'd just like
to confirm everybody elses works this way because both sides of mine are
identically flawed if so. And I literaly ripped one set of boards apart trying
to find a problem and that problem too.

everything else is perfect, I tested each q perside, the tracking on each of the pots, with the q, with gain.  Only one of my pots was a hair different.  very happy.  Put the knobs on today.  the noise floor is -93db with the +8db eq in. it gets flat as a pancake.

Yeah, orientation was a pain, there was 1 I had to guess on then later kind of guessed out because it is only in rev 5. it's the 22u around the insert point.  (having to look upside down here.)

But all of then have a little of the + except one of the rev 4 pdf if you look really close.

Course I'm still a newbie and it's not like I had built it before, but I do have the two sets working identically and it is a *****en eq. I like the pultec's high and low end better for mastering sudletly but everything else and inbetween, this thing rocks.

calrec PQ1549 help thread
« Reply #19 on: March 25, 2005, 03:24:14 AM »
Quote from: "cwatkins"


Yeah, orientation was a pain, there was 1 I had to guess on then later kind of guessed out because it is only in rev 5. it's the 22u around the insert point.  (having to look upside down here.)


Could you draw the orientation into one of the pictures I posted ?

Quote from: "cwatkins"

But all of then have a little of the + except one of the rev 4 pdf if you look really close..

Yep, I could read the +'s on the boards, but the problem is that some orientations on the board differ from the one in the schematic. Did you just follow the rev4 PCB layout (which is the same as rev5 for the 33 u orientation) ? or did you follow the schem for this ?

Also, how does this thing sound ?

Gustav


 

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