Using an old signal generator with the modular

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Kent, luketeaford, lisa, Joe.

Post Reply
kdjupdal
Common Wiggler
Posts: 222
Joined: Mon Jan 26, 2009 11:44 am
Location: Norway

Using an old signal generator with the modular

Post by kdjupdal » Wed Sep 02, 2020 10:47 am

Hi.

I got this old signal generator for free, and want to try to use it as an oscillator and maybe plug it into my modular synth.

Anything I should think about? I'm thinking about making a cable that goes from two banana plugs to one jack plug. One banana connects to ground, and the other to either 6ohm or 5Kohm. Is this the way to do it? Maybe try it first with a cheap speaker?

20200901_165702.jpg
You do not have the required permissions to view the files attached to this post.

User avatar
MikeDB
Common Wiggler
Posts: 130
Joined: Fri Feb 08, 2019 8:28 am
Location: UK

Re: Using an old signal generator with the modular

Post by MikeDB » Wed Sep 02, 2020 11:53 am

The 5k output should be fine. I imitated the Hawkwind Silver Machine startup using one similar to this driving a simple VCO back in 1972.
Personally I hate cats !

User avatar
EATyourGUITAR
has no life
Posts: 5786
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Using an old signal generator with the modular

Post by EATyourGUITAR » Wed Sep 02, 2020 12:38 pm

Is this square wave or sine? You don't need to test with a cheap speaker. You test it with an oscilloscope. You can patch to a passive attenuator and bring it up slowly to %100 while you watch the levels on your meters if you do not have an oscilloscope.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

User avatar
MikeDB
Common Wiggler
Posts: 130
Joined: Fri Feb 08, 2019 8:28 am
Location: UK

Re: Using an old signal generator with the modular

Post by MikeDB » Wed Sep 02, 2020 2:52 pm

EATyourGUITAR wrote:
Wed Sep 02, 2020 12:38 pm
Is this square wave or sine?
I would assume the logo in the corner indicates a sinewave. It will be a standard Wein bridge oscillator with a thermister or low voltage bulb to stabilise the gain
Personally I hate cats !

jorg
Ultra Wiggler
Posts: 791
Joined: Fri Apr 03, 2015 9:38 am
Location: East Coast USA

Re: Using an old signal generator with the modular

Post by jorg » Thu Sep 03, 2020 9:42 am

It almost looks like it's 3U! Maybe you can screw it right into your rack?

Main thing to watch for is keep the signal level low enough not to hurt your modules (under 10Vpp will be perfectly safe), and yes - use the 5k output. There's also a 4 ohm output you could drive a speaker with for fun.

kdjupdal
Common Wiggler
Posts: 222
Joined: Mon Jan 26, 2009 11:44 am
Location: Norway

Re: Using an old signal generator with the modular

Post by kdjupdal » Thu Sep 10, 2020 2:12 pm

It is a sine wave. I just tried it with a small speaker.
There seems to be some bad contact because the output level knob doesn't work, it just makes the signal sometimes disappear and sometimes become suddenly stronger.

jorg
Ultra Wiggler
Posts: 791
Joined: Fri Apr 03, 2015 9:38 am
Location: East Coast USA

Re: Using an old signal generator with the modular

Post by jorg » Thu Sep 10, 2020 2:26 pm

Your level pot is either dirty or worn out.
If it was mine, I'd spray in some Deoxit. I will get :foul: :mad: :sstorm: :bang: for saying that. But the worst case (assuming you don't dribble the stuff around inside your equipment) is you end up replacing a pot that's already bad. Best case, you eke out a bit more life from it.

User avatar
EATyourGUITAR
has no life
Posts: 5786
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Using an old signal generator with the modular

Post by EATyourGUITAR » Sun Sep 13, 2020 7:11 am

jorg wrote:
Thu Sep 10, 2020 2:26 pm
Your level pot is either dirty or worn out.
If it was mine, I'd spray in some Deoxit. I will get :foul: :mad: :sstorm: :bang: for saying that. But the worst case (assuming you don't dribble the stuff around inside your equipment) is you end up replacing a pot that's already bad. Best case, you eke out a bit more life from it.
my problem is that you did not say what deoxit product to use. if you want to say F5 then someone uses D5 bye bye potentiometer. my strategy is ALWAYS use F5 first. if that does not fix it, D5. then if that does not fix it. replace the part. :party:
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

User avatar
Bartimaeus
Veteran Wiggler
Posts: 559
Joined: Sat Jun 22, 2013 4:05 pm
Location: Well that isn't very punk, is it?

Re: Using an old signal generator with the modular

Post by Bartimaeus » Sun Sep 13, 2020 11:51 am

for something like this (i.e. cool old device), wouldn't it be better to just disassemble the pot and scrub the washer with a little isopropyl alcohol and/or contact cleaner?

jorg
Ultra Wiggler
Posts: 791
Joined: Fri Apr 03, 2015 9:38 am
Location: East Coast USA

Re: Using an old signal generator with the modular

Post by jorg » Mon Sep 14, 2020 10:29 am

EATyourGUITAR wrote:
Sun Sep 13, 2020 7:11 am
jorg wrote:
Thu Sep 10, 2020 2:26 pm
Your level pot is either dirty or worn out.
If it was mine, I'd spray in some Deoxit. I will get :foul: :mad: :sstorm: :bang: for saying that. But the worst case (assuming you don't dribble the stuff around inside your equipment) is you end up replacing a pot that's already bad. Best case, you eke out a bit more life from it.
my problem is that you did not say what deoxit product to use. if you want to say F5 then someone uses D5 bye bye potentiometer. my strategy is ALWAYS use F5 first. if that does not fix it, D5. then if that does not fix it. replace the part. :party:
Thanks for the nuanced answer; that's helpful to me and the OP.

User avatar
EATyourGUITAR
has no life
Posts: 5786
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Using an old signal generator with the modular

Post by EATyourGUITAR » Mon Sep 14, 2020 12:33 pm

Bartimaeus wrote:
Sun Sep 13, 2020 11:51 am
for something like this (i.e. cool old device), wouldn't it be better to just disassemble the pot and scrub the washer with a little isopropyl alcohol and/or contact cleaner?
If you want to disassemble and clean with distilled or deionized water then that would be the best way. Isopropanol is a solvent. I am not an expert in old potentiometers but I know I want to use distilled water only if that will fix the problem. Solvents are what you use after you tried something that does not ever do damage. F5 is the same as calilube mcl faderlube etc. The big company buys the little company. It is a lubricant that is safe to use on exposed resistive traces. The instructions say to get it inside the potentiometer then turn fully CCW then CW 10 times very fast. This is like the windshield wiper on a car. You end up with a pile of dirt at each extreme of the potentiometer. Sometimes it all gets washed out if you get lucky. Lubricants like this are exactly as safe as water. Isopropanol is safer than D5 which is an oxidization remover. It reacts with oxides. If it can eat rust maybe it can eat other things as well. Isopropanol is probably safe on everything. I use %70 to be sure there is no damage on the first attempt to repair. The other %30 is distilled water. This will dissolve lipids (oil) that are already hydrophobic. It also reduces surface tension because of the properties of isopropanol. This is done without surfactants so it means you don't have to worry about adding dish soap and then washing it all away. Isopropanol with water will air dry everytime even inside a potentiometer where you can't see.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

Post Reply

Return to “Music Tech DIY”