Build Thread:PQD2

[Potato Cakes]

You're wiring the power switch to be ON-OFF. All you're wanting to do is connect AC to the transformer primary. Gustav covers this in his universal wire guide. This is also found in the various assembly guides on his site.

Thanks!

Paul

 

[Beeswax]

My voltages tested well and I finished it up. Right channel only is passing audio and functioning. Left doesn't pass audio. Left tube appeared to be illuminating less strongly so I switched them - same result. Any suggestions where to begin to chase this down?

 

[Gustav]

My voltages tested well and I finished it up. Right channel only is passing audio and functioning. Left doesn't pass audio. Left tube appeared to be illuminating less strongly so I switched them - same result. Any suggestions where to begin to chase this down?

Tubes are powered in series - one gone = both gone.

You can take the filter out of the equation by jumping the two outer pins on the three pin connector from main board to filter board.

If you have audio through when doing so, your problem is in the filter board. (most likely both gain stages are working if one is -its a simple signal path).

If thats the case, try swapping the connections. If the "working side" stays, your problem is the cabling/connections being made. If it moves, its in the filter itself.

If it turns out to be the filter, youre lucky. In this case it will be extremely easy to find the problem, since you have a working side to compare to!

Gustav

 

[Beeswax]

Thank you, Gustov. So, the tubes are not the issue as I am getting proper DC readings even though one tube is illuminated more strongly than the other.

Please, could you clarify which of the two "3 pin connectors" between the main board and filter board you are suggesting I jump - is it the connection with only 2 wires between them (Left/Right)? My wiring from main to filter board looks correct.

Could you explain what function the two sets of connections from the board to the filter perform?

Thank you for your help. This has been a productive build from which I continue to learn.

 

[Gustav]

Thank you, Gustov. So, the tubes are not the issue as I am getting proper DC readings even though one tube is illuminated more strongly than the other.

Please, could you clarify which of the two "3 pin connectors" between the main board and filter board you are suggesting I jump - is it the connection with only 2 wires between them (Left/Right)? My wiring from main to filter board looks correct.

Could you explain what function the two sets of connections from the board to the filter perform?

Thank you for your help. This has been a productive build from which I continue to learn.

Jump it from side to side - middle pin carries the ground.

The signal path is: Signal into the main board, then we send it to the filter (connector), and take it back from the other end (connector), then to the gain stage, making up for the loss of amplitude in the filter. So the connectors are send/return to the filter, which is passive.

They have an asterisk to denote the orientation.

We only take the middle pin from the left connector, when we connect to the filters, becuase that carries the ground, and we only want to connect that once

Gustav

 

[Beeswax]

Thank you, Gustov. So the asterisks represents the "send" or "return", not left/right? Am I understanding correctly that I should solder a jumper between the outside points on 3 pin connector (see pic with my fingers)?

 

[Gustav]

Thank you, Gustov. So the asterisks represents the "send" or "return", not left/right? Am I understanding correctly that I should solder a jumper between the outside points on 3 pin connector (see pic with my fingers)?

I cant really see the connections on the picture due to the angle/fingers.

Solder the outer connections, yes. I cant remember if the asterisk is "send" or "return", thats why I do things like putting the asterisk there, so its just a matter of matching * to * when connecting the boards.

If you had a scope, it would be a simple as probing it.

Gustav

 

[Beeswax]

My little digital scope wasn't giving me good feedback so I've placed the jumper. Is this correct? This is the grounded connection on the main pcb. If I get audio passing on both channels in this test that means the problem is on the filter board, yes?

 

[Gustav]

If I get audio passing on both channels in this test that means the problem is on the filter board, yes?

Exactly!


And if its not, run a check with the "working channel" with both filters, just to eliminate it as a source of additional error, before you start hunting for the problem on the main board. This will save you the trouble later, in case there happens to be an error in both parts of the circuit.

Gustav

 

[Beeswax]

So, with the jumper in I'm still only getting right channel and strangely the filter was still activating when I switched bypass on/off. I thought the jumper bypassed the filter board entirely.

 

[Beeswax]

oops, I only saw the "Exactly" portion of your reply before. So, to test the filter section is it the other pair of connector wires that are the left/right connections? Am I simply crossing over those those wires from main board to filter board (right to left and left to right) in order to rule out the filter as the problem?

 

[Gustav]

Im sorry, but you lost me, and I think I lost you, so Ill take it from the top.

The documents for the PQ2 are here.

https://drive.google.com/drive/folders/1BF1dT0CIHx1Ks9KsvXLPzB759YCp3j5C
There is a schematic.

In the input section, you can see the pins connecting between the main board and the filter board (pic 1).
after the filter, you can see the pins connecting the filter board back to the main board (pic 2)

These are pin 1 and 3. (On the input screenshot, you can see pin 2 grabbing the ground as well)

This goes for both the left and right channel, so do it on both, 1 is send, 3 is return, and even though you can get them crossed while attaching the filter, we dont care which is which when jumping them.

If you jump 1 to 3 (pic 3), the filter should definitly be out of the way. This is just meant to be a quick test to see, if you have issues in the signal path/bypassing the filters, and when we know, we can proceeed.

And of course, you will have to do it on both channels!

Hope that helps!

Gustav

 

[Beeswax]

Thank you very much, Gustov. So, with both connectors jumped and bypassing the filter board entirely I'm still getting only right channel. Does this point to a main board issue on the left channel then?

 

[Gustav]

Thank you very much, Gustov. So, with both connectors jumped and bypassing the filter board entirely I'm still getting only right channel. Does this point to a main board issue on the left channel then?

Yes - if you are not getting audio through, you have a problem on the main board.

1.Please verify that you tried swapping the tubes.
2. Please check heater and HV voltages on the individual sockets.

If you have one channel working, the basic PSU should be working.
This leaves you with just a very small section to cover for trouble shooting (check the schematic for reference, youll see what I mean), and you should also inspect the board visually.

You mentioned having a scope - I would advice you to invest some time in getting that up and running.

Gustav

 

[Beeswax]

Oh man, my hubris is too much. One of my transformers was missing a solder joint! Everything is working and sounding beautiful. Thank you very much for offering support here, Gustov. I'm glad I got to understand the circuit a little bit more through this problem.

Would you share with me what you had previously posted on your website about how your "pultec" circuit differs from the original? I was interested to read that again but don't find it on your site anymore.

 

[Gustav]

Oh man, my hubris is too much. One of my transformers was missing a solder joint! Everything is working and sounding beautiful. Thank you very much for offering support here, Gustov. I'm glad I got to understand the circuit a little bit more through this problem.

Would you share with me what you had previously posted on your website about how your "pultec" circuit differs from the original? I was interested to read that again but don't find it on your site anymore.

Glad to hear you made it!

About the circuit, you probably read it on Gyraf.dk !?

This project was based off Gyraf's PeQ DIY version. I just doubled the amount of channels run off the same supply and controlled everything using PCB mount/off the shelf Lorlins so it would be a breeze to build it.

Produktside | PCB Grinder

Ill be happy to help with any build issues - if I can!?

Gustav

(from the first post of this thread).

Gustav

 

[shagcity]

Hello Gustav! I assembled the unit and I'm struggling to hunt down an issue. The AC voltages are measuring correctly. The high voltage DC is measuring around 250, but the DC that is supposed to measure 12.6 is only measuring around .4 volts.

When I power on the board, I hear a slight hissing sound that sounds like it's coming from the in/out transformers but it's hard to tell without sticking my face in there.

Audio is not passing beyond the transformers whatsoever. I'm wondering if you have any hunches as to what's going on. I visually inspected and reflowed a few joints on the main PCB and everything looks good.

Thanks in advance!

 

[Gustav]

You say the heater voltage is off, so I would start by looking into that. The schematic is in the folder on the site, and were talking 2-3 parts that make up that portion of the circuit.

Would you know what to do, if I told you to check if you are shorting out the regulator to the case?

Gustav

 

[shagcity]

You say the heater voltage is off, so I would start by looking into that. The schematic is in the folder on the site, and were talking 2-3 parts that make up that portion of the circuit.

Would you know what to do, if I told you to check if you are shorting out the regulator to the case?

Gustav

Aha you nailed it! The regulator was shorting to the case. Everything is working and sounding beautiful. Thanks Gustav!

 

[Gustav]

Aha you nailed it! The regulator was shorting to the case. Everything is working and sounding beautiful. Thanks Gustav!

Sounds like that was a "yes" then

Great job!

Gustav