Sorry if this message is a repeat ..I'm new
I have a home built Moog Mod 3C....from time to time I keep coming across
problems...my latest is "thumping noises" when playing sine or triangle
osc. ..i think the thumps come from the EGs....is this normal or do I need
to fine tune them ( the EGs)via the mini-pots (which i have allready tried)
moving T3 and Esus helps but does not cure...is this normal for C3's?
Modular unwanted noises
The thumps may be coming from the differential stage of your VCA. If the stage is out of balance, it will cause a thumping sound.
Do not attempt to turn trimpots unless you know what you are doing. Some trimpots interact with others and require multiple steps for a calibration. Others may affect the temperature compensation, if you mess with those then you will need laboratory references to calibrate them.
You can royally mess up other things without realizing it and make your repair bill worse because it will require a complete calibration to get everything all square again. If you are not qualified in electronics, then leave calibration to a qualified tech.
Do not attempt to turn trimpots unless you know what you are doing. Some trimpots interact with others and require multiple steps for a calibration. Others may affect the temperature compensation, if you mess with those then you will need laboratory references to calibrate them.
You can royally mess up other things without realizing it and make your repair bill worse because it will require a complete calibration to get everything all square again. If you are not qualified in electronics, then leave calibration to a qualified tech.
Many thanks for your help.......this has given me a different lead.....
as mentioned I made the modules about 5 years ago and as far as i remember i calibrated the VCA's as best as I could...but i guess I have nothing to lose to have another go..i have all the calibration tests from the
schematics so I'll see what happens..by the way do you own a modular?
best wishes
as mentioned I made the modules about 5 years ago and as far as i remember i calibrated the VCA's as best as I could...but i guess I have nothing to lose to have another go..i have all the calibration tests from the
schematics so I'll see what happens..by the way do you own a modular?
best wishes
-
Kevin Lightner
- Posts: 1587
- Joined: Sat Jan 15, 2005 5:20 pm
- Location: Wrightwood
On the 921's, there's both triangle and sine DC offset trimmers.
If you made 901's, you may have to hand bias the offset via selected resistors.
Use a DC coupled scope directly on the waveforms in order to know.
VCA pop is also common, however I'm taking your post literally as if there's no VCA in the patch. And no, I don't own one either, but I know them pretty well.
There's usually one (or more) here.
If you made 901's, you may have to hand bias the offset via selected resistors.
Use a DC coupled scope directly on the waveforms in order to know.
VCA pop is also common, however I'm taking your post literally as if there's no VCA in the patch. And no, I don't own one either, but I know them pretty well.
There's usually one (or more) here.