73-75 Serge panels from Zthee

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finlayshakespeare
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Re: 73-75 Serge panels from Zthee

Post by finlayshakespeare » Sun Mar 08, 2020 8:08 am

elmegil wrote:
Sat Mar 07, 2020 11:28 pm
2) Notes on that site say it's supposed to be horizontal mount, open side down. The intent is for these to be mounted vertically in a 19" rack or perhaps in one of those pop-up racks, so maybe more at a 60 degree angle. How important is this for a reverb? I've only ever dealt with the TTSH reverb in the past. There's not really any option as far as I can see to mount it on the "side" of the boat, because it's wider than the side is tall.



With regard to the R*S boats, I understand I'm going to have to do some modification to make the panels & boats work together; has anyone done this and have any particular advice?
In terms of reverb tank mounting, I’ve never experienced it make a difference which orientation the tank is in. For my own 73-75 builds, I’ve mounted the tank with the open side facing the back of the BUD boat which has been absolute fine reverb wise. It also makes mounting the tank relatively easy - screws/bolts through the back of the boat then nuts securing the tank to the boat.

I’ll have a look later as to what tanks we opted for and how they worked depth wise - it was definitely tight!

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Re: 73-75 Serge panels from Zthee

Post by elmegil » Sat Mar 14, 2020 3:43 am

Next question for this build has to do with jacks

The bananas appear to follow the Elby color scheme (I have 8 colors, just missing Orange, which as a special, probably doesn't apply), but I have nothing that I've been able to find that maps the Elby scheme to the specific positions on these panels.

Anybody have a pointer?

I did spend some time poking at what the jacks *did* and how they were colored originally (to get a sense of AC/bipolar, DC/unipolar, and pulse) and they don't match the quantities of bananas for blue, green and yellow. The other colors make sense. I have too many blue, a couple too few yellow, and a lot too few green. See the attachment. (I have 58 blue instead of 48, 17 green instead of 25, and 15 yellow instead of 17).
Serge-73-75-DIY-recolored.jpg
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Re: 73-75 Serge panels from Zthee

Post by tele_player » Mon Mar 30, 2020 9:21 am

xonetacular wrote:
Tue Jan 14, 2020 12:33 am
My build is finally complete.

Image

Image

Image

Image

Image

Managed to squeeze everything including the large accutronics tank and full sized power module into 2" shallow boats. Took some work and creativity to get it all to fit- it's one unit riveted together. Decided against LED mods as I think it looks cleaner without and this project was already a pain. Went with a Random*Source inspired color scheme and am happy with how it turned out.
My Homebuilt is ready for boxes, still undecided on depth.

How did @xonetacular get the reverb to fit in a 2" boat? Was the reverb removed from its enclosing case?

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Re: 73-75 Serge panels from Zthee

Post by goyousalukis » Tue Mar 31, 2020 10:11 pm

Hey guys, finishing up a 73-75 panel set. I am calibrating the envelopes. What is the slowest frequency they should self oscillate at? I have pin 10 at 4 volts when end is connected to cycle. I am getting around 250hz for each of the envelopes - is this correct? I am not having any luck calibrating the hold function. I have set the positive slew to cycle and connected the pulse out to the hold of the envelopes, but it doesn't seem to do anything, and adjusting trimmer 2 doesn't seem to do anything. I have verified all the correct components across the three envelopes, but I am new to Serge, so I don't know what the hold should do. Thanks for any help!
EnvelopeTrace.png
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Re:

Post by elmegil » Tue Mar 31, 2020 10:40 pm

nateflanigan wrote:
Sun Dec 01, 2019 1:43 pm
- Calibrating the envelope generators: The elby instructions feel convoluted to me and the 73-75 is a little vague. It helps to read up on how these work, they're kind of counter intuitive, so just having a better understanding of how it's supposed to function is a good thing.
Turn the rise and fall knobs all the way up/fully CW looking at the component side of the board (I did this backwards first go). Follow instructions.
To set the HOLD trim pot, patch according to instructions. I used a 4x AAA battery pack to supply a constant "gate" signal but there are lots of ways you can rig this up. Set the trimpot to center. I found it easiest to monitor the output of the module with a DMM set to VDC, you're not looking for a specific voltage but you're adjusting the trimmer for the least amount of fluctuation.
This is from earlier in this thread (the new forum's "search this thread" function is very useful -- not trying to scold you but I do want to point it out, it has made a HUGE difference in finding info like this).

This is what I used to help me calibrate them. When it says a "gate" it means a steady high voltage. I used a scope to find minimum fluctuation.

This is the old CGS info on the R7 EG: https://www.elby-designs.com/webtek/cgs ... 6_env.html

And here's the elby page with their version, with its own calibration notes: https://www.elby-designs.com/webtek/eur ... r/es06.htm

Between these two docs and ZThee's build docs, and the comment above I was able to do it.


The hold is *kinda* like a sample & hold's hold, except that you are holding whatever voltage the envelope is at that moment rather than some other input signal.

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Re: 73-75 Serge panels from Zthee

Post by goyousalukis » Wed Apr 01, 2020 7:25 am

Thanks, I should have mentioned that I did try that procedure. I have also gone through the two other links you posted. Instead of using a 6v battery, i connected the hold to the 6V rail. I am still getting no change when I adjust the hold trim pot. That is why I was asking about the speed of the envelope generator. I wonder if there is a problem with mine. Some of the literature mentions that the envelope generator is more like an LFO that can go into audible ranges, but 250 hz minimum seems pretty high for that.
Thanks for your response.

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Re: 73-75 Serge panels from Zthee

Post by elmegil » Wed Apr 01, 2020 8:39 am

Oh, 250Hz minimum? Yeah that's definitely too fast. All three do the same? I'd double check the caps for value and shorts.

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Re: 73-75 Serge panels from Zthee

Post by goyousalukis » Wed Apr 01, 2020 8:56 am

Thanks - I'll unsolder one set of caps and verify the values.

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Re: 73-75 Serge panels from Zthee

Post by tele_player » Wed Apr 01, 2020 11:20 pm

Just as a point of reference. I just timed the Envelope on my Voice. It works well, but I doubt it’s well trimmed. I’ll revisit it when I power up my lower Homebuilt panel in a few days.

Anyway, at the high end, I get about 200Hz. At the low end, a single cycle took about 130 seconds.

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Re: 73-75 Serge panels from Zthee

Post by goyousalukis » Thu Apr 02, 2020 9:35 am

Thanks - I got it sorted last night. I read through all the different versions of the calibration instructions a bunch of times, but for some reason, I was stuck on the original incorrect instructions from the website that say turn the pot counter clockwise, so I was calibrating the max rate at the slowest pot setting. I think I have the hold calibrated as well as I can. If I send the envelope to the VCO CV, and I have it set for medium frequency range it is pretty solid when I apply the 6V. If I have it set to max frequency range, it does still drift, but I think that is about as good as I can get it.

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Re: 73-75 Serge panels from Zthee

Post by goyousalukis » Thu Apr 02, 2020 12:54 pm

Cherry laser engraved side cheeks...
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Re: 73-75 Serge panels from Zthee

Post by tele_player » Thu Apr 02, 2020 2:09 pm

Beautiful!

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Re: 73-75 Serge panels from Zthee

Post by kevin0 » Sat May 02, 2020 3:38 am

How useful are the DC coupled outs on the vcos? What have people been doing with them?

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Re: 73-75 Serge panels from Zthee

Post by PacificState » Sat May 09, 2020 11:47 am

OK, I've misunderstood something here, and it's probably very dumb.

Having finally got the power supply and the boards into the same boats, I decided I'd probe out the PCB with my scope before wiring it, to see that everything looked vaguely functional.

What I don't understand here is that, although the voltages from the PSU are perfect when referenced to the post DC-DC converter ground, this and the chassis / pre converter ground are not tied together. Furthermore, grounding my scope's probe to the post converter ground appears to short out the supply.

What did I miss here? I clearly need a reference ground for interfacing, but I'm not sure how to resolve this.

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Re: 73-75 Serge panels from Zthee

Post by tele_player » Sat May 09, 2020 12:28 pm

Exactly which PSU board are you using? Is it powered by a DC wall wart?

I may be misunderstanding your description, but assuming you’re using the PSU which was provided with the Homebuilt, the input side of the DC-DC converter isn’t grounded at all. Two wires connect from the wall wart to the converter, via a LC filter. The case gets grounded with the same ground as goes to the boards. All measurements are taken relative to that ground.

At least, that’s what I see in the build manual - I built mine using a different power supply (FC Power.)

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Re: 73-75 Serge panels from Zthee

Post by PacificState » Sat May 09, 2020 12:51 pm

That's it, thanks - the input jack is metal, and everything works if I pull it from the case temporarily and avoid that connection.

I guess I now have to either figure out a new jack, or a way to insulate the existing one ;-)

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Re: 73-75 Serge panels from Zthee

Post by elmegil » Sat May 09, 2020 1:11 pm

PacificState wrote:
Sat May 09, 2020 12:51 pm
That's it, thanks - the input jack is metal, and everything works if I pull it from the case temporarily and avoid that connection.

I guess I now have to either figure out a new jack, or a way to insulate the existing one ;-)
I've run into this on occasion too. With a wall wart supply like the FC (with AC input), if you're using a metal jack in a metal boat you need to make sure that the sleeve connection is what goes to ground, or you get weird problems too. I've taken to using plastic power jacks like this one

http://smallbear-electronics.mybigcomme ... tic-round/

Or this one

http://smallbear-electronics.mybigcomme ... ed-2-1-mm/

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Re: 73-75 Serge panels from Zthee

Post by finlayshakespeare » Fri May 15, 2020 3:25 am

Seconding the above - you should use an insulated DC inlet to power up the +12/+6/-12V PSU so that it remains isolated. When probing the boards, refer your scope or meter back to the 0V from the PSU, not the DC inlet.

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Re: 73-75 Serge panels from Zthee

Post by nateflanigan » Thu Jun 11, 2020 6:27 pm

Hey, I just wanted to add to the errata that I've finished a second build that I'm powering with this meanwell desktop psu.

https://www.mouser.com/ProductDetail/709-GP25A14E-R1B

Also, for this one I used the standard budd boats and larger reverb tank. To deal with the issue of fitting the reverb tank into the boat I just mounted it to the back of the boat.

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Re: 73-75 Serge panels from Zthee

Post by Lostcity » Sun Aug 16, 2020 7:15 am

Hi, a good friend of mine lent me his 73-75 for me to try to repair it.
I'm not very familiar with the Serge but after a few hours of patching, i'm pretty sure of the two below issues (probably) :

1. Low amplitude of the OSC.
The whole Oscillator functions seems working very fine aside the amplitude is very low.
I need to patch it through the preamp to have it usable into a patch. Definitely not normal to me. How it is on yours ?

On the build note, the three trimmers are related to: initial offset, range & sine to saw adjustment.
So no trimmer for amplitude...

2. Triple WaveShaper is a bit odd.
The waves are well folded/shaped under CV control but it's way more drastic when i turn the control knobs.
Quite hard to explain.

I checked the PSU in the first place and the voltages are good.

Everything else is ok.
(not sure what the Peak & Through is supposed to do but checking by the schematic it seems like a mixer/or thing ?)

Very nice double panels anyway !
Thanks for your input in advance.

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Re: 73-75 Serge panels from Zthee

Post by tele_player » Sun Aug 16, 2020 7:38 am

If you have a scope, it’s easier to discuss oscillator output with some real measurements.

On the wave shaped OSC output, I get about 2v p-p.
On the sawtooth (or is it ramp?), I get about 4-5v p-p.

The TWS is best viewed with a scope, and most effective when two or three are chained.

Peak and Trough:
Peak - output is the voltage of the highest input . With no input, output is LOW
Trough - output is the voltage of the lowest input. With no input, output is HIGH

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Re: 73-75 Serge panels from Zthee

Post by Lostcity » Sun Aug 16, 2020 8:39 am

thank you tele_player.
Regarding the OSC output, i have only a Motu Osciloscope here to check.
I took some screen shot and comparisons between OSC and POS SLEW

OSC :
Sine OUT waveform
Image

Ramp OUT waveform
Image

POS SLEW :
Grey (bipolar) OUT waveform
Image

I'll had another check on the peak & through.

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Re: 73-75 Serge panels from Zthee

Post by tele_player » Sun Aug 16, 2020 10:49 am

I see about 4V p-p on Positive Slew with my system.
Assuming the voltage scale is the same in all your screen shots, yes, it looks like your Oscillator is weak.

I don't have a speciic suggestion, except normal trouble shooting. Verify all the chips are getting correct voltages, visual check for problems, work back from output towards input to locate the problem.

Verify correct type and orientation for the 2N3904 transistors.

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Re: 73-75 Serge panels from Zthee

Post by thombet » Sun Sep 06, 2020 5:08 pm

hi everyone

love the build of these panels and the calibration is going smooth but i came across some issues.

1) in the reverb preamp section there are 2 22uF caps between the preamp pot and the mix pot. is the silckscreen print and grounpath wrong or is the example pic wrong ==> http://www.73-75.com/wp-content/upload ... _0576.jpg ?

2) is there no ground (W path)for the adapter? but my guess is that you need a ground in order to proces any signal out or in?

anyone had these same issues?

cheers

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Re: 73-75 Serge panels from Zthee

Post by tele_player » Sun Sep 06, 2020 6:58 pm

I built a Homebuilt earlier this year, and have another set of boards completely unstuffed.

1) I'm sure I stuffed those 22uF caps as marked on the silkscreen, though I'm not going to open it up to check. I think the photo is in error.
Anyway, mine works fine, though, depending on the actual voltages, and the voltage rating of the caps, they would probably work either way.
(It took me a while to figure out what problem you saw , then I finally noticed the polarity marker on the caps in the photos.)

2) The Adapter section doesn't really need to be on the board at all. I ran a bare wire along the three 3.5mm jacks sleeve connections, and wired that to the ground (W). I wired directly from each banana to the adjacent 3.5mm tip. If I recall correctly, the Adapter on the Voice panel doesn't even have a section on the board.

One tip, before you try to close it up. Observe, in the photo, under the reverb pot, a flat cap is bent over. This area is a little tight, and that cap (and the nearby 3906, IIRC), can interfere with the nut on the nearby banana plug. That cap needs to be mounted as shown in photo.

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