Poor Man's Pultec EQP1-A Build Support Thread

[wave]

Brice,
Here is my crappy diagram. I hope it helps. On this I drew the second 6.3VAC secondary as being capped off and not used but you could very well use it to power a 6.3V Fender style jewel lamp for a power on indicator on the front panel.
Anyway good luck, and feel free to ask any other questions. God knows, I've asked my share

Dave

 

[ruffrecords]

Nice diagram. Well done. What did you use to create it?

Cheers

Ian

 

[wave]

Nice diagram. Well done. What did you use to create it?

Cheers

Ian

Thanks Ian.
I use Adobe Illustrator for these and my homebrew etch files.  So I was correct in connecting one of the 6.3VAC secondary wires (in one pair) to the 75V hole on the PCB? In my etch file (I sent you in an email) I made it with 6.3VAC in and out terminals with the in connected to the 75V spot.
I'm going to make an overall PMEQP-1A hookup diagram so I'm sure you will be getting questions about that!

Dave

 

[ruffrecords]

Nice diagram. Well done. What did you use to create it?

Cheers

Ian

Thanks Ian.
I use Adobe Illustrator for these and my homebrew etch files.  So I was correct in connecting one of the 6.3VAC secondary wires (in one pair) to the 75V hole on the PCB? In my etch file (I sent you in an email) I made it with 6.3VAC in and out terminals with the in connected to the 75V spot.
I'm going to make an overall PMEQP-1A hookup diagram so I'm sure you will be getting questions about that!

Dave

Yes, you were correct in connecting one of 6.3VAC wires to the +75V hole. That 75V is for heater elevation.

I was thinking of doing an overall hookup diagram but since you just volunteered I am happy to let you do it and I'll check it for you!

Cheers

Ian

 

[wave]

Thanks Ian,
I think it will be great practice in my never ending struggle of reading schematics.

Dave

 

[funkymonksf]

Thanks again. I've been studying this whole layout and I love the challenge. Sure glad I have good people to help!

 

[ruffrecords]

Here is a hand drawn sketch if what I think you need. I am sure you can make it look much better.

Cheers

Ian

 

[wave]

Ian,
Thanks for the sketch. It really helps.
One question: I also have the PMEQP1A Hookup pdf and in that diagram there is no 12K resistor strapped across the input transformer secondary before the EQ in/out switch. Was that overlooked in the PMEQP1A hookup pdf?

 

[ruffrecords]

Ian,
Thanks for the sketch. It really helps.
One question: I also have the PMEQP1A Hookup pdf and in that diagram there is no 12K resistor strapped across the input transformer secondary before the EQ in/out switch. Was that overlooked in the PMEQP1A hookup pdf?

Yes, you are right, it was overlooked in the Hookup pdf. The idea was to make the nominal load on the transformer close to 10K and with the 12K across the secondary it is close to 10K when all the pots are in the off position (no boost or cut). As soon as you apply some EQ the load impedance drops at some frequencies (the ones you boost) and rises at other (the ones you cut) but that's just a property of passive EQ.

For most sources  (where the driving impedance is much lower than 10K) it doesn't really matter.

Cheers

Ian

 

[WNStudios]

Looking through the schematics and my boxes of salvaged parts.

Does it have to be a 6CG7 tube?
I got 3x 6DJ8/ECC88 Philips ones and 2x 6BL8/ECF80's Philips.
I'm going with the pcb and BOM that's provided by Ian and it would just be nice if those old guys would get some use after all these years.

 

[ruffrecords]

Looking through the schematics and my boxes of salvaged parts.

Does it have to be a 6CG7 tube?
I got 3x 6DJ8/ECC88 Philips ones and 2x 6BL8/ECF80's Philips.
I'm going with the pcb and BOM that's provided by Ian and it would just be nice if those old guys would get some use after all these years.

You could use the 6DJ8/ECC88 tubes but you would have to reduce the HT to no more  than about 250V but that is just a matter of using larger dropper resistors in the power supply. YOu might need to change bias resistors too. I'll look into it. Note the gain would be much higher than with a 6CG7.

Cheers

Ian

 

[WNStudios]

You could use the 6DJ8/ECC88 tubes but you would have to reduce the HT to no more  than about 250V but that is just a matter of using larger dropper resistors in the power supply. YOu might need to change bias resistors too. I'll look into it. Note the gain would be much higher than with a 6CG7.

Cheers

Ian

I've found a toroid readily availible for me that has a secondary of 185V, would that be way under what i need? I was thinking a stereo unit at first but i think i will do two seperate units so it would only run 1 makeup stage. "Primary 230V, secondary 185V 0,04A and 6.3V 1,4A." to be exact. If it's much higher, could i simply put an output pot on there, or even an output transformer just to tame it?

 

[ruffrecords]

You could use the 6DJ8/ECC88 tubes but you would have to reduce the HT to no more  than about 250V but that is just a matter of using larger dropper resistors in the power supply. YOu might need to change bias resistors too. I'll look into it. Note the gain would be much higher than with a 6CG7.

Cheers

Ian

I've found a toroid readily availible for me that has a secondary of 185V, would that be way under what i need? I was thinking a stereo unit at first but i think i will do two seperate units so it would only run 1 makeup stage. "Primary 230V, secondary 185V 0,04A and 6.3V 1,4A." to be exact. If it's much higher, could i simply put an output pot on there, or even an output transformer just to tame it?

That should work fine because by the time it has been rectified it will be around 260 volts and you would aim to lose about 30 volts across the RC filters which gives you 230 volts which should be fine..

Cheers

Ian

 

[WNStudios]

Thank you very much for your help Ian! Really looking forward to this project. Hopefully a couple of questions will be cleared when i got the pcb's and i'm sure some other will pop up

 

[funkymonksf]

I'm considering using a inductor for the top bell position. Using Ian's list I gather I'll need a 50mH, however I cannot find that value in any usable size. Can I use a 47mH?

Also if I am using an inductor should place the capacitors in that positions or short them out or do nothing at all? And if I don't use an inductor should I short the position?

Thanks for all the help,
Brice

 

[ruffrecords]

I'm considering using a inductor for the top bell position. Using Ian's list I gather I'll need a 50mH, however I cannot find that value in any usable size. Can I use a 47mH?

Also if I am using an inductor should place the capacitors in that positions or short them out or do nothing at all? And if I don't use an inductor should I short the position?

Thanks for all the help,
Brice

47mH is close enough. You need to include appropriate value capacitors to create the bell at the frequency you want. If you do not use the inductor you do need to replace it with a shorting link.

Cheers

Ian

 

[WNStudios]

Got the PCB's today Ian, extremely fast! Thank you! Will start populating them with what i have today.

 

[adeptusmajor]

First, I apologize if this has already been discussed here...

I am finally starting to move forward with this project, started sourcing components the other day.

I noticed that the values of the diodes and electrolytic caps for the power supply are different on the schematic and bom from the values silk screened on the board itself.

Should I stick with the bom and schematic, or should I up the values to what is printed on the board? I am building a two channel unit if that makes a difference.

Thanks.

 

[ruffrecords]

First, I apologize if this has already been discussed here...

I am finally starting to move forward with this project, started sourcing components the other day.

I noticed that the values of the diodes and electrolytic caps for the power supply are different on the schematic and bom from the values silk screened on the board itself.

Should I stick with the bom and schematic, or should I up the values to what is printed on the board? I am building a two channel unit if that makes a difference.

Thanks.

The power supply PCB was originally designed for another project that needed larger value smoothing capacitors. You should use the values in the circuit diagram/BOM. Also, the diodes on the PCB were for a higher power supply, but for just two channels regular 1N4007 diodes will be fine.

Cheers

Ian

 

[adeptusmajor]

That's what I figured. Just had to be sure.

Thanks