EQP-1S5 500 series PULTEC ---- HELP/BUILD thread

[mitsos]

Thanks! Yes I took some tape, and now they sits perfectly. But now when I put the module into my 51x rack to calibrate it, the LED doesn't seem to work. How can I test if this is broken?

Good to hear that's sorted.  See below for LED info.

I left out the R5-R6 as you suggested. First I thought I wired the on/off switch wrong, and switched but still no light. And no signal

Well, you should only leave out R9... not any other resistors.  R5 should not affect signal coming in or out, but for sure r6 affects the LED, it's the current limiting resistor, without it the LED circuit is broken.

To check for signal, you can probe at the topmost header near the input trafo (module held vertically). That's the secondary of the input trafo, signal here confirms your relays and input trafo are wired/working properly.  Then check the third header. That's the output of the filter, you should see signal (about 21.6 dB lower than at pin 1). If no signal then you need to check the filter PCB for shorts to ground. If this is OK, then probe around C47, the output cap, that will show problems in your opamp circuit, and finally the output pins of the card edge to check for issues with the output trafo. 

It's so typical, I thought this build was really a quick one, with no strange things, just easy enough for me.
Any clues?
Best regards
John

Don't worry it's not only you... I find its always the easy ones that give me problems!

 

[Monoklang]

Ok, R6 will be easy to put in... but R5 now when the two boards are together will be tricky. I will see what I can do...

I'm not even sure there were none signal, I just saw that the LED didn't lit. I'm might panicked and didn't check the DAW in full.

I'll try to fix this tomorrow.

Thank you very much!
John

 

[mitsos]

Ok, R6 will be easy to put in... but R5 now when the two boards are together will be tricky. I will see what I can do...

OK I see where you got confused on the resistors.. those instructions are referring to the 5534 adapter PCB, not the main PCB..  sorry, I should have put those instructions at the end. I'll do that now so no one else gets confused.

For R5, some little needlenose pliers might help position it, but you'll want to remove the PCBs and solder from the bottom because of the other parts near the resistor.

good luck, post back with results!

 

[Monoklang]

I managed to solder R5-R6 without taking the boards apart.   How should I wire the on/off to do it right?

John

 

[Monoklang]

Now the LED is working, and when in off mode the signal runs through it. But when in on, I now try to calibrate it, how many turns? Nothing seems to happen here. So I'm guessing I'm doing something wrong... I should turn the trim clockwise, right?

John

 

[mitsos]

Cool!  Guess you figure out the switch

As for the gain trim, it works just like the gain control of an amp.  If you installed it the way it's shown on the PCB, clockwise should give you more gain.  Did you preset it to halfway? I can't tell you how many turns as it's a multiturn trimmer and it would depend on the initial setting. If you turn it and start to hear it clicking, it means you went all the way to the end of its travel, which would mean either you're going the wrong way or that there is a problem somewhere.

 

[Monoklang]

Yes there is some problem here. Nothing happens when I turn the trim, and the signal of my output does not sound the same as the one I send in.

I can't post a sound file here so I will mail it to you. The signal drops all the way down to nothing and this half distorted sound comes instead of my beautiful 400hz tone.

John

 

[Monoklang]

Did you preset it to halfway? I can't tell you how many turns as it's a multiturn trimmer and it would depend on the initial setting. If you turn it and start to hear it clicking, it means you went all the way to the end of its travel, which would mean either you're going the wrong way or that there is a problem somewhere.

How do I know when the trim is halfway?

 

[mitsos]

That's a beautiful 400Hz tone indeed

RE trimmer being halfway... you have to check it prior to installing.  Now that it's in place, tun it off, keep turning the trimmer in one direction until it clicks, then turn it back 12-15 complete revolutions. 12.5 turns "should be" halfway as it's linear.  EDIT, Upon further inspection these trimmers don't seem to have a clicky.  SO, we'll make it easier, just pull out the opamp (with module turned off) and measure between the negative input (DOA socket closest to the trimmer) and ground.  You should be able to see the trimmer resistance directly here.  Turn it to about 2K to get you in the ball park.

 

[dandeurloo]

Thanks guys!

 

[okgb]

I'd call it a straight forward build  ...............only three extra parts left
[ joking ]  and it worked first time [ after I remembered to soldered the pcb's together  ]
strange to solder more caps than resisters

I think it would be handy to have the actual markings from on the caps as another column in the list
so you can see exactly what C28 should look like for reference .

Being paranoid about the l.e.d.  solder , I used a fine flat file to get it low and then exacto knifed
a bit of electrical tape onto the bottom of that pot .  Careful cutting the leads off as cutting into the solder
can make it spread out more

the first doa socket I put in was snug and I thought great I don't want it to be flush and risk solder
flowing in  , when the next one was looser I simply put the pcb on it's edge and did the rest that way .

When it seemed like the xfmrs maybe loose I put a couple strips of electrical tape on top , I don't know if they were
in the end but it didn't hurt .

I ran the xfmr wires below the pcb like the pic on the buy thread , if you do this leave enough wire to go around the Stand off

Like parts stuffing it's a good idea to put the knobs on from the middle first , start with the low bst & hi bst select

BTW what is the correct size of  allen key for the knobs ?

Crap now i gotta use it which means I gotta practice before I can record

 

[Marcocet]

Finally got a chance to give these a listen today. WOW do they sound good. You totally nailed is Mitsos. Thanks again!

 

[mitsos]

Nice pic Dan!  Four channels o'fun! 

Great job for all three of you guys in fact, thanks for the comments, they are always welcome!  Greg, I'm re-wording some things in the build doc, I'll add the cap desciptions to help people out, thanks for pointing that out. 

I too like the trafo wires below the PCB, looks a bit neater, doesn't it? Of course, it works either way.

Enjoy your EQs guys!

Monoklang: my emails to you keep bouncing back, not sure if you are getting them?  Let me know if you have another email.

 

[Monoklang]

Ok, hmm strange. Yes you can mail to this adress instead:
[email protected]
or [email protected]

There's something wrong with server...

But have you received  any mails from me?

Regards
John

 

[jandoste]

Hey Mistos& Niels,
Got the new inductor Thanks! Thanks! Thanks
so, here we go! Amazing! it's sound wonderful! my best Pulteq EQ! and thanks again for this sound!

 

[mitsos]

Ok, hmm strange. Yes you can mail to this adress instead:
......
.....

There's something wrong with server...

But have you received  any mails from me?

Regards
John

Hi John,
I sent the emails via PM here, and I've just now replied to all three email addresses. Let's see which ones go through!  
Was just some thoughts on troubleshooting.

FWIW, I think you should delete your email addresses from your post above, to avoid that any spambots pick them up.


@Jandoste...  ahem... nicely stuffed rack ya got there... 

Glad it's all worked, out, very happy you like the EQs, they are my faves too!  ;D

 

[sonic02]

Sonic02: That is a new one on both of us. It might help to know which JLM opamp you are using and a bit on your test methods? 

To expand a bit on Niels comment on the JLM, there is no feedback cap used with a 2520. At least there wasn't one in the original and we haven't used any.  There is however a spot for it marked CF, since I didn't know what opamp people would use, and some may want to see one. If you try this, I would try a C0G/NPO or mica cap between 47-100pF. 
 
The resistor in parallel with the cap will allow a bit of DC to get into the transformer winding, and is what API did to "tame" the low end boost in their circuit (I think I may have explained this somewhere, but there is a thread where member Abbey Road d-enfer posted graphs showing what it does).  I will look for it and post a link if I find it.

The 1K8 load resistor on the output transformer would change its response, so if the cause of your problems is the JLM opamp's interaction with the outpu trafo, that might help things. If you decide to try this, temporarily putting a 5K trim pot in there would allow you to find the best possible value.

I would first try the CF.

Thanks for the info guys. The opamp was JLM99V. I tested with a 1kHz test tone. I took the JLM out and switched with an API 2520 from my 550b and adjusted for unity gain, worked perfectly. Just waiting on a GAR2520 to arive, should works the same.

Ran some vox, snare and guitars through it, simply beautiful. Very very smooth. The bottom end on the gtrs was very lush, and the upper mids to add clarity to the vox didn't add sibilence 
A great feature for me is the High Band Attenuation, as I suffer from high end build up syndrome  gonna luv this feature. 

The only down side is that i'm afriad that i will wear out the silkscreening, gonna get a lot of use from this, and the silkscreen may not hold up over time, no biggy though.
Great work guys.

 

[mitsos]

Glad to hear you got it working.  I had a feeling it was the JLM, I'll see if I can get a hold of Joe and see why it might be.  All I know is that they have a fairly large DC offset, but it should otherwise be stable.  For now, I added a note in the build doc so people are aware it didn't work in at least one situation.

Also very glad you enjoyed the EQ, I too love it on voice.  The lows can give a male singer some real cojones, and the highs are real sweet.  No artificial sweeteners here! ;D

I wouldn't worry about the silkscreen, it was done by an excellent shop, they do great work.

Thanks again for taking part!

 

[JLM Audio]

Glad to hear you got it working.  I had a feeling it was the JLM, I'll see if I can get a hold of Joe and see why it might be.  All I know is that they have a fairly large DC offset, but it should otherwise be stable.  For now, I added a note in the build doc so people are aware it didn't work in at least one situation.

I wonder if the DC offset of the 99V has something to do with it?
[Joe] Yes it will as the current circuit has no dc gain removal cap.

  Or maybe you could shed some light?
[Joe] Without the 100uF shown added to the circuit I have attached the opamp will do 20dB of gain from DC to 1MegHz roughly. So the 1v offset at the 99v output pin will be about +13v so there will be no where for the opamp to swing positive any more. Adding the 100uF is recommended for all opamps as it allow all types to work in there with minimum dc offset problems. 100uF cap can be in series with the trim pot either before or after it.

There is normally no feedback cap (there is a spot for one on the PCB), but the amp should only be doing a bit over 20dB of gain, so I didn't think that'd be it.
[Joe] Actually the the feedback cap is usually needed at low to medium gain setting as the bandwidth at these settings goes very high to usually above 1MegHz. So the cap is needed to keep the opamp stable by bandwidth limiting it down to 200Khz or so and to stop RF pickup at -IN an the opamp OUT pin especially in a modern mobile phone world and open frame 500/51X racks.

Anyway if you can shed any light, I'm interested to know.
[Joe] Both caps would be best fitted so all opamp types can run stable in the circuit with better headroom including the 2520. In all EQP1A3 Solid States that we have refurbed at JLM have added a 120pF feedback cap as recommended in old API 2520 notes as it improves the wideband THD measurements. Most other opamps will be fine with 47pF like our 99v. See circuit mod below.

Hope that helps. Post here if you have more questions on this as I have subscribed to this thread now.

 

[Vernois]

I seem to be missing where to find the build instructions, any help?
Thanks, Gavin