Build Thread:MS PQ76

[hotmouthrecords]

Hello DIY ERS!   

This is to publicly thank Gustav for all of his help.  Thank you Sir!  PCB grinder as well!  they are awesome!  110 % satisfaction.

After a weird wiring nightmare, and some trouble shooting,    SHE LIVES!
 
and she would like to meet all of ya'll.  I just assume the slow ramp up time is Normal behavior.
She is sweeping thru Frequencies like a pro and keeping clean beautiful signal.    she is heading into my mastering chain as soon as the 2 new cables show up. may a positive DIY force spread to everybody.

HOTMOUTH RECORDS
San marcos TEXAS

Now lets make RECORDS!

 

[Gustav]

SHE LIVES!

Excellent

I just assume the slow ramp up time is Normal behavior.

Theres an errata sheet on the kits page. If you add the resistor mentioned on the last/second page, the "warm up"-time will come down.

Gustav

 

[Industrial Waves]

Hi everyone

I'm trying to finish my unit. For the on/off switch in the front pannel can I use this one?
https://www.banzaimusic.com/DPDT-on-on-Toggle-15A-250V.html

I have a problem with the hole because is of 11mm and the switch needs a 12 hole. Someone had a similar problem and how has it solved?

I soldered the 2 resistors of 2KOhms from each one of the elcos to  ground, but I don't have changed the gain pots to 22K, 5k1, and 15 K resistors. What is the outcome of this change? I can use the unit (primarily for testing) and if I have time or the benefits are relevant I can change it later.

In the toroid wich is the positive and the negative? I soldered grey and violet and I have blue and brown cables.

Can you please say me the values of the test points?

Thanks for your help.

Javi Piles

PS: I will upload some pics this week

 

[Gustav]

Hi everyone

I'm trying to finish my unit. For the on/off switch in the front pannel can I use this one?
https://www.banzaimusic.com/DPDT-on-on-Toggle-15A-250V.html

I have a problem with the hole because is of 11mm and the switch needs a 12 hole. Someone had a similar problem and how has it solved?

Since you are using a different power toggle at a larger diameter, just widen the hole with a 12mm drill.

I soldered the 2 resistors of 2KOhms from each one of the elcos to  ground, but I don't have changed the gain pots to 22K, 5k1, and 15 K resistors. What is the outcome of this change? I can use the unit (primarily for testing) and if I have time or the benefits are relevant I can change it later.

It changes the throw of the gain a bit, no big deal, just a minor adjustment (to my taste).

In the toroid wich is the positive and the negative? I soldered grey and violet and I have blue and brown cables.

The toroid puts out AC, so there is no negative or positive. You should make sure to set it up correctly, though.

Theres a wiring guide for it on the PCB Grinder page you may have missed, but building a project of this complexity, I would recommend that you take the time to read up on how it works and understand it.

Can you please say me the values of the test points?

The test points are spread through the audio path.

Gustav

 

[Industrial Waves]

http://postimage.org/index.php?lang=spanish


share image


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I'm measuring the output of the psu board (disconnected from the main board) because I don't get the output values. I started following the schematic with my multimeter, to be sure that all the connections are ok.

Thanks for the answer Gustav.

Javi Piles

 

[Gustav]

I'm measuring the output of the psu board (disconnected from the main board) because I don't get the output values. I started following the schematic with my multimeter, to be sure that all the connections are ok.

Start by checking that you are getting 15V relative to the center tap, or 30V side to side on the output from the toroid.

If that is correct,  check the output from the PSU isolated.

If you are not using the toroid mount to mount it into a modushop case, I would recommend bolting it directly though the case, and if you do keep it on the small mount, do NOT mount it to the case via the adhesive feet - secure it with screws through the case to avoid creating a death trap.

Gustav

 

[Industrial Waves]

Hi Gustav, yes I checked it. In the output of the toroid I have the right values. I will check it again this evening.

Thanks

Javi Piles

 

[Industrial Waves]

Yes I measured it again and I have 17-18 Vrms (side - center tap)  and 34 - 35 Vrms (side - side tap)


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sube fotos

 

[Industrial Waves]

The output voltages are ok. I just wasn't measuring it correctly. Today I will put the IC´s and connect it to the main board.

Thanks

Javi Piles

 

[Industrial Waves]

Ok some measurements, this is a disaster! hahaha

All the measurements are done with the BOOST or ATTENUATION control to maximum, and changing the frequency control. In L/R mode. And Bandwidth at 5 more or less.



This is ok



This is also ok




Here is something wrong

-------------------------------------------------------------------------------------------------------------------------------

CHANNEL 2









I´m going to check it point by point... I hope better news for tomorrow

 

[Gustav]

Ok some measurements, this is a disaster! hahaha

1. check one channel at a time in split mode first.

2. Describe  what you are measuring, and what you would expect to see on each measurement

(I dont know whats wrong on the "here is something wrong" captioned image, for example).

Gustav

 

[Industrial Waves]

Hi everyone and thanks for the help Gustav really apreciate it.

Ok I´m checking the only L channel, or channel 1.

- Active (not bypassed)

First filter, LOW FILTER:

- ATT: 0
- BOOST: 0
- FREQ: 20 Hz

Then I vary the output gain pot and I obtain this measurement.
The measurements of avobe are with the pot at middle (5 more or less) and gradually decreasing the level.
The lines from below are with the pot at the maximum position (all the way to the right).


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First filter, LOW FILTER:

- ATT: MAX LEVEL
- BOOST: 0
- FREQ: 20 Hz / 25 / 30 / 40 / 60 / 100


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---------------------------------------------------------------------------------------------------------------------------------
First filter, LOW FILTER:

- ATT: 0
- BOOST:  MAX LEVEL
- FREQ: 20 Hz / 25 / 30 / 40 / 60 / 100


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----------------------------------------------------------------------------------------------------------------------------------
Second filter, HIGH FILTER:

- ATT: MAX LEVEL
- BOOST:  0
- FREQ: 2,1 / 2,5 / 3,2 / 6,8 / 12 /18
- BW: 5 or 6

I expected to see a curve gradually (just like the low filter) in the higher frequencies. The LPF is set to 20 KHz. The gain to MAX.


direct upload
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Second filter, HIGH FILTER:

- ATT:  0
- BOOST:  MAX LEVEL
- FREQ: 2,1 / 2,5 / 3,2 / 6,8 / 12 /18
- BW: 5 or 6

I expected to see the boost in the high freq. but I only get more or less a flatt response (like the previous measurement)


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--------------------------------------------------------------------------------------------------------------------------------------

Third filter, LPF:

- ATT:  0
- BOOST:  0
- FREQ:  3 / 4 / 6 / 8 / 10 / 20

I expected to see the cut on each frequency.


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Second channel is more or less the same.

Javi Piles

 

[Gustav]

Javier.

EDIT:

Before doing anything else, look at the overall picture of assembly guide page 31, and filter connectors on page 33, then fix the faulty wiring.

Always check the basic signal path integrity before doing more esoteric tests like frequency sweeps! I tend to try to make sense of doing trouble shooting on frequency plots with the assumption the more basic test (signal path flow) has checked out fine.

I have scrolled through it a few times, and I still have a hard time following exactly what you are doing.

In any case, it does look odd, and since you say its on both channels, lets focus on the left channel first, and...

Of course, make sure DC voltages are correct all over, then.

1. start by checking the signal path (you have the test points) before doing sweeps.
2. Make sure you did not  reverse the filter connectors
3. Make sure you did not reverse the M/S switch, so we are sure you are sending a single sweep through the left channel only.


Then, to help me understand fully,  do a description in the form of.

1. I am sending (x)  level into the unit, and adjust for level coming back.
2. The EQ is set to flat apart from, gain on (high boost), which is set to (third step).

3. This is what I am getting when I vary the frequency.  (plot).




Gustav

 

[Industrial Waves]

Hi

Thanks Gustav to take time to see my graphics.

After changing the filter cable as Gustav said, I have also seen that an IC was wrong plugged in the socket, and 2 of the pins doesn´t make contact, then I connect it good.

I also tested the MSPA76 with values of boost and attenuation of 10 (instead of 11, that is the maximal value). Stepped to 10, the high filters do the curves properly. So to summarize, in the first channel work everything ok, I only have to see what happens with the pots that when I put it to 11, it doesn´t work well.

In the second channel I also have the same problem and few more: the high filter selector (2,1  2,5  3,2  6,8  12  18) don´t select anything.  The graph shows always the same curve


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And the LPF don´t work, simply the frequency response is flat.


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Thanks for everyone I will try to fix it and upload some images.

Javi Piles

 

[Gustav]

I would like to see a picture of the fixed wiring. It sounds like you didn't fix it.

Doing frequency sweeps  is a horrible way to do basic trouble shooting, so please stop. In fact, it would be a huge advantage if you would please jump the filter connectors so we can focus  on making sure everything is ok - but first, before doing anything, let me see a picture of the fixed wiring!

Trouble-shooting the filter itself after that is a piece of cake, if there  even are any errors.

Gustav

 

[Industrial Waves]

Hi,

I think is question of bad setting in the stepped switch, i configured it to 11steps, but It shoud be configured to 10 I´m right? The default configuration is with the pot set to 1.


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I also jumped the filters yesterday and feed the EQ with a sine wave at 1kHz, and at the output was OK, so maybe I forgott something, or is wrong placed in the filter boards. I will repeat it in a few hours.

Thanks for the help Gustav.

 

[Gustav]

I think is question of bad setting in the stepped switch, i configured it to 11steps, but It shoud be configured to 10 I´m right?

Depends on which switch you are talking about, but check the schematic. I assure you, you can read how many steps are used of a switch if you take a few seconds.

The default configuration is with the pot set to 1.

Not sure what you mean by this.

I am really confused about the status of your project. I feel like you ignore some basic requests for info to rule things out, but maybe I am asking the wrong way.

Can you verify that the signal path is working correctly now with the filter jumped? This should include the gain pot functioning.

If so, we can focus on the filters.

Gustav

 

[Industrial Waves]

I tested it again and it works fine now. Sorry if I asked for help for very basic topics, this is one of my firsts projects. I followed all your steps, the unique thing was that I was testing all the time with frequency sweeps (and that was ignoring your advice, sorry but I don´t know a better way) I tested it with an osciloscope and a sine wave following the audio path, an disconnecting the filters to check the input and output of the main board to discard fails.

Thanks for supporting me throughout the process.

Javi Piles

 

[Gustav]

Sorry if I asked for help for very basic topics,

Asking questions is great - I just want to get these things to work.

Glad that you got there

Gustav

 

[kustohm]

Hi too all DIYer's

I've just finished my own MSPQ76 but I have some issues:

All the voltage are good from toroid to main board.

I made all the mods from the "Errata" book.
But when I turn the unit on is like my gain pots are reversed... And I have a very little sound even if I push them max
In Bypass everything nice.

I changed the gain pots by 22k lin as you said, maybe I wiring them bad, could you help me please?
Thanks