Ensoniq ESQ-1 noise

Hi all!
On my recently bought ESQ-1 there is a noise emitting in the background everytime I push a key. It is there even when I shut off all three VCAs and it is more prominent when the filter is wide open.
Is this normal? It sounds like a digital noise and it sometimes changes pitch on different keys but not always.

I have done a hard reset with no change and I also listen to the outputs directly from the output buffer TL084 and the noise is still there.

One thing I noticed is that if I shut of all VCAs the noise is there for a about halv a minute and then gradually disappear. When I turn on the VCA the noise comes back.

I would highly appreciate If any ESQ-1 owner out there could test their machine to see if you also have this noise or if you know how to fix it.



its a faulty / failing power filter capacitor. Your gonna have to look at / test the capacitors to see which one is faulty. Its probably a tantalum type as they short or go open when time expired, or over stressed.

Thanks for you input. In these cases, is it a capacitor only in the PSU or can it be anywere on the main PCB?

d like to hear how this comes out…favor us with a coda when its resolved…

I will!
I have posted on different forums and basically got two possible reasons for this problem. First is failing power capacitor, as midnightvision said. Second is a broken DAC/multiplexer.

1st congratulations on your acquiring of the esq -1 I have mine from 1988 and it is having a restoration of the 8 capacitors on the power supply. These must be replaced because they are 85 Celsius rating and they are 33 years old they will fail, go for Panasonic radial capacitors fc or FM with 105 Celsius rating with a 5000 working hours. This is those 8 capacitors you will need large psu electrolytic capacitors c1 3300 uf 25v, c8 3300 uf 25v, c17 4700 uf 16v, c18 4700 4700 uf 16v. These small psu electrolytic capacitors c10 100 uf 35v, c 11 470 uf 63v, c12 220 uf 35v, c13 470 uf 63v i ordered them from mouser electronics total price $11.58 cents. I just realized typing this that psu stands for power supply unit and the C1 is for the location on the circuit board. This keyboard was made in the good old USA in Malvern, Pennsylvania and the original components used are Panasonic and nichicon capacitors. if you are going to do a recapping job look at bradthx on you tube and check replacing capacitors for ensoniq esq 1 and the video on recapping. get a anti static bracelet a must have for this project and desoldering wick an inexpensive copper foil that protects the other components. good luck and enjoy the ensoniq esq-1

When searching the web for others with jumpy value-sliders(another fault I had on my esq-1) I found this thread:
https://forums.syntaur.com/t/ensoniq-es … und/448/13
“we_robot” suggested looking at U40 and it’s filter caps being 0.01 instead of the recommended 0.1. This is some fault from the factory, supposedly.
I replaced these caps and lo and behold, both the jumping in the value-slider and the noise are gone!

It is still gritty sounding, but when turning off the DCAs it is silent(in some patches I can still hear the filter clicking but I think that is normal).

that is excellent news! let the music play

dig hearin replies like this…Plus that the KISS principle was used. BradTHX has saved alot of boards/helped alot of folks and is a Syntaur customer. I urge everyone on here with a good command of English to subscribe to his channel. My next project with him is the Alesis Quardraverb andif anyone has a parts machine/junk let me know…

indeed Bradthx and the guys on you tube has save a lot of vintage synth owners grief and I have recommended them on my previous post. my new restoration project is a 2nd hand ensoniq sd-1.