Build Thread:PQD2

[Murdock]

Hey Gustav, I got a question concerning grounding... again  ;D
I read your post on general grounding in the G-Pultec thread:

"General grounding:

- Power input gnd to chassis gnd.
- Wire XLR's pin1's together.
- Wire from xlrF(input)pin1 to input gnd on PCB.
- Also wire from this point xlrF(input)pin1 to chassis gnd."

I did it like this and like in your "Wire Guide" pdf, where only on the first channel input pin 1 is connected to gnd on pcb. And each additional channel pcb gnd is not connected.
But could it be that it would be better to also connect input pin 1 from the second channel to the gnd on pcb?
Or would that create a so called ground loop?
Because I'm starting to think that the buzz I hear is a grounding issue. The left channel (which has a connection between XLR and pcb gnd) is dead silent. But the right channel isn't.

And I noticed that the inductor in my AML ezMEQ-5 is also quite close to the power transformer and I get no buzz there...
Would be nice if you could elaborate a bit on this matter. This whole grounding thema is really confusing, especially because everybody seems to handle it different...

 

[Gustav]

could it be that it would be better to also connect input pin 1 from the second channel to the gnd on pcb?
Or would that create a so called ground loop?
Because I'm starting to think that the buzz I hear is a grounding issue. The left channel (which has a connection between XLR and pcb gnd) is dead silent. But the right channel isn't.

The ground is connected between the XLRs on the PCB, so you would just create loops with your method.

I also think its a bad place to start your investigation based on your previous comment.

Yeah, the buzz varies when I move the cable around. It also gets alot quiter when I touch the lamp holder... is that an indicator that it isn't making proper contact with the chassis/ground?

1. Disconnect the lamp  - see what happens. If it solves your issue, try drawing the ground from the lamp back to a different point (you may be using the GND test points now. Also, is this an LED or an actual lamp?)
2. Try rotating the toroid - see what happens..

And I noticed that the inductor in my AML ezMEQ-5 is also quite close to the power transformer and I get no buzz there...

Could be one is shielded, and the other is not, or any number of other factors (the power trafo plays a role as well) . I mentioned it as something worth investigating, and to do that, you can rotate the toroid a bit, try shielding it, try unmounting the inductor and move it around a bit to see if it influences the sound.

I do not have experience with the inductor you are using in the build, or the inductor you are referring to, so these are just suggestions for variables that are easy to investigate.

This whole grounding thema is really confusing, especially because everybody seems to handle it different...

The method I put up for the project should work, but your build is unique, with a unique layout, a unique choice of inductors etc.

So, other than the suggestions I made so far - experiment!

Gustav

 

[Murdock]

Hey Gustav,
thanks for your answer. Will experiment next time I opened the unit up!

I have another question:
In the "Transformer lists for projects" thread, it is stated that one could use the Peerless S-217-D as an output transformer in the G-Pultec.
Is that true? Could I use the S-217-D in the PQD2? If yes, would I have to make any adjustments to the circuit because of the higher impedance?
(http://www.bunkerofdoom.com/xfm/PEERLESS1953/Peerless_1953_08_0001.jpg)

 

[Hobbyist]

Hey guys,

I'm sharing my finished version. Have to say, after comparing with the software editions from UAD and WAVES, the sound is brilliant! So useful for many processes ! Very nice project to work on and learned a lot from it. It took a while to get 1% tolerance with all the components, but i'm glad I did it to get decent stereo balance.

Good stuff Gustav !

Cheers
M

 

[Hobbyist]

.. and another one.

 

[Vac11]

Hi Gustav,

i have some troubles with my PQD2.  Yesterday I turn on the EQ for the first time (with asistence of my friend - el. tech, he checked all wiring before).

After 30 second the bridge rectifer behind the 9VAC connector was very hot.  After another 30 sec was the round bridge rectifer dead. Where could be a problem?

I used B380C1500 (W10M, 1000V/1,5A.) for both bridge rectifers...
Toroid trafo spec. is:
TS 30VA
PRI: 2x115V
SEC:
> 230V (35mA)
> 9V (2A)
> 6V (0,5A)

Today I changed both bridge rectifers and also LM317 and same problem... Where can we start?

Thanks

M.

 

[bernbrue]

Disconnect the power transformer and measure the AC voltages of the secondary.  I don't know what kind of torroid transformer you've got there, but the white leads do not look like they were secondary windings.
Bernd

 

[Vac11]

Thank you, we try it.

It is custom toroid from toroidy.pl. On the toroid is "sec white 9V, sec purple 230V, sec black 6V"... 6V is for lamp and relays bypass pcbs, relays clics corectly and lamp shines.

 

[bernbrue]

Ok, I would measure if anyway.  Check the colour code once again. Do the bridge rectifiers have the correct orientation?  ~ ~ +- . What did you do with the 4,7 caps? 
Bernd

 

[Vac11]

Orientation is 100% correct. There are two big 5u8F soviet PIO cap instead of 4u7F foil caps...

M.

 

[bernbrue]

I've never seen a bridge rectifier melting down, so there must be either a short, a cap with wrong polarity or wiring mistake.
Bernd

 

[Vac11]

I think voltage on secondaries are OK:

sec 9V...................9,91VAC (measured)
sec 230V..............239,68VAC

We disconnected input and output xlrs and filter board  from "main" board. We connected toroid transformer secondaries (9V and 230V) to main board and main board worked properly - lamps shone, voltage on the 6,3 VDC point was 6.07 and on the 250VDC point was 179VDC (there is 22K as drop resistor, so I think when I change this resistor for smaler value voltage would be OK in range 210-250VDC). Voltage before this resistor was cca 300VDC.

My problem is somewhere in bypass PCBs wiring. When we conected "shields" (pin 1) from XLRs to main board wago conectors, the bridge rectifer started burn and smell in a few seconds.... When we disconnected shields from mainboard this problem go away....

My wiring diagram attached...

V.

 

[Gustav]

I think voltage on secondaries are OK:

sec 9V...................9,91VAC (measured)
sec 230V..............239,68VAC

We disconnected input and output xlrs and filter board  from "main" board. We connected toroid transformer secondaries (9V and 230V) to main board and main board worked properly - lamps shone, voltage on the 6,3 VDC point was 6.07 and on the 250VDC point was 179VDC (there is 22K as drop resistor, so I think when I change this resistor for smaler value voltage would be OK in range 210-250VDC). Voltage before this resistor was cca 300VDC.

My problem is somewhere in bypass PCBs wiring. When we conected "shields" (pin 1) from XLRs to main board wago conectors, the bridge rectifer started burn and smell in a few seconds.... When we disconnected shields from mainboard this problem go away....

My wiring diagram attached...

V.

Seems obvious you have an incongruent 0V reference with your wiring, but I can't see where you are drawing those by your drawn example, or by the pictures - where are you drawing your 9V, and ground reference on the bypass board?

Try looking at the PSU part of the PQD2 schem, that may give you an "aha!?" moment.

And do you have a schem of the bypass board?

Gustav

 

[Vac11]

Thanks Gustav.

Here is bypass PCB schematic and manual:
http://diy-tubes.com/image/data/manuals/bypass-en-v1.0.pdf

Toroid 6VAC secondaries wires lead to small "rectifer pcb" with four diodes and one electrolytic capacitor. After rectification I have cca +- 8-9VDC.  9VDC wire leads to SPST "bypass" toggle switch and then to bypass pcb "+V" point (on the filter pcb are joined pin holes for DPDT toggle, so filter board is permanent in circuit). From bypass pcb "OV" point leads wire to "-" point on small rectifer board I selfetched. I think maybe here could be my mistake...

Thanks again

V.

EDIT: For clarification I modified my previous wiring schematic....

 

[Vac11]

Small update:

Today I connected right  chanell xlrs direct to main board and sent signal to EQ from DAW.  EQ pass audio without any artifacts. I was very very happy what I heard. Really nice sounding EQ.

I looked at the EQ schematic as Gustav recommended. Is my mistake, that I didnt connect "OV" from bypass pcb to chassis?

 

[Gustav]

Small update:

Today I connected right  chanell xlrs direct to main board and sent signal to EQ from DAW.  EQ pass audio without any artifacts. I was very very happy what I heard. Really nice sounding EQ.

I looked at the EQ schematic as Gustav recommended. Is my mistake, that I didnt connect "OV" from bypass pcb to chassis?

I had a hard time following your description, but obviously some ground terminal error like discussed.

Glad it works!

Gustav

 

[Vac11]

Yesterday I tried EQ again. I did some wiring changes. I connected "-" from my small rectifer board to mains pcb ground,  I also connected "OV" from bypass pcb to mains pcb ground.

Bypass pcbs works corectly. EQ pass uneffected audio in bypass mod. Both chanells. So I think this wiring change was a step in the right direction.

Still have problem with bridge rectifer heating when shields from xlrs are connected. When  connected shields to main pcb WAGO connectors bridge rectifer is very hot in few seconds...

My second trouble is that left channel dont pass audio in "EQ IN" mod. Unfortunately right chanel is OK and sounds amazing so I can compare component after component. I have to try filter section alone with some audio.

So my troubleshoting continues....

 

[Lieto]

Hello, I have the same problem as Vac11 ... I use no Bypassboard ... the problem must be elsewhere. 9V bridge is very warm and there is no signal coming out of my unit. I have all the components checked, transformer connected properly etc ... Help pls! The strange thing is, the unit has been running once. Then I decided to mount the LM317 to the housing. Then it overheated the bridge. Have also taken away the LM317 from the housing again, but it does not work.

Greetings Andy

 

[Gustav]

So my troubleshoting continues....

I can see you already found a solution earlier, which wasn't really a solution after all, it seems.

I still cant follow what you are doing, and I am sorry, but you have to make it easier to help you, unless you prefer going at it by yourself.

Step 1. Basic configuration to eliminate variables! Take the bypass board out of the equation, return wiring to stock set-up.

Gustav

 

[Gustav]

Hello, I have the same problem as Vac11 ... I use no Bypassboard ... the problem must be elsewhere. 9V bridge is very warm and there is no signal coming out of my unit. I have all the components checked, transformer connected properly etc ... Help pls! The strange thing is, the unit has been running once. Then I decided to mount the LM317 to the housing. Then it overheated the bridge. Have also taken away the LM317 from the housing again, but it does not work.

Greetings Andy

Not sure how this is related to VAC 11, but I will try.

1. Bridge may not be specced to pass sufficient current
2. LM317 will not overheat the bridge by being properly cooled, Error is not the operation of connecting it to chassis to cool, error must lie in the manner it was connected, o in something else putting too much load on the bridge.
3. Any dead tubes at this point?

Hope that gives you something to go by.

Gustav