VG-88 - Hum in vg88

Started by yngwie_m, November 29, 2012, 07:11:38 PM

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yngwie_m

Hello everyone! New one here with some questions.

First of all: In high gain presets like the slo, there is a hiss that I can't get past but with high settings on the noise reduction which compromises the sustain of the sound. The hiss is there even with use of the magnetic pickups of the guitar.

Secondly, when using the gk3 there is a hum in acoustic or nylon or sitar patches that goes away with the nr set at 90!!! But then when I play a note the hum comes up only to be lost quickly when I stop playing. I have no effects on in these patches. Just the acoustic amp and the noise reduction. Again the noise reduction setting is a no no for playing.

Sometimes when I touch the strings in patches that the gk3 is on I get a ground hum. When I leave them the hum goes away. The pickup and the cable are new.
Is there a ground needed for the gk3 pickup itself?
The guitar is an Ibanez rg548, vg88 and from there to the di box. The ground lift switch on the di box changes nothing.
We use in ear monitors for monitoring.
The thing is that the hiss on high gain and the hum on acoustic patches persists even in the house with the in ear monitors directly on the vg88.

What do you think is the reason for these two problems? And most of all what could be the cure?

Thanks everyone in advance and greetings!!!
I am a bomb tech.If you see me run,try and keep up

Kevin M

External GK3, right?  What are your sensitivity settings?  Do you use the short 1/4" cable from guitar out to GK guitar in (assuming it's an external)?

yngwie_m

Yes it's an external kit. The sensitivity is set around 30. I use the gk only in acoustic patches and use the magnetic pickups for electric guitar patches. So yes to the second question, the quarter inch cable is plugged in.

Another thing I 'd like to ask is: When I flick the switch on the gk3 or press the s1 and s2 buttons, I get a noise like "boom" coming out of the amp or the in ear or the P.A. What is this one?

All this add to the problem of carefree use of the unit.
I am a bomb tech.If you see me run,try and keep up

billbax

Hi Yngwie m,

Sorry to hear of your GK3 troubles.  Kmaus10 is right about the 1/4" jack being connected to your GK3, as it provides an audio ground to the metal parts on the guitar.

The "boom" sound could be the GK3 sensor connector to the pcb. I think you will have to take apart the GK3 and check. Probably a good idea to carefully lift off the connector and closely inspect with a magnifying glass....be careful or you will cursing me!  While you at it, try air-dusting the GK3 13pin socket and do your 13pin cables as well.

This sounds like a simple problem, and can't imagine its your VG-88.

Bill

yngwie_m

Thank you billbax. The boom noise is there with an older gk3 I have on my other guitar. So when I do open the gk3 to inspect it, what am I searching for? Dust? Bad wiring? Thank you again. What about the other two problems? I must add that my guitars are completely shielded and grounded. When I just plug the guitars in the quarter inch guitar in jack I have no problems, hissing, humming, booming and so on. As long as the 13-pin is connected with the quarter inch also in noises aappear. In the club we play the instruments are on o power line dedicated to them and them alone. So no interference from lighting, freezers from the club's kitchen and so on. But the problems persist in the house also.

I repeat that one of the gk3's is brand new, two months old and so is the gkc5 cable I am using at the moment.
I am a bomb tech.If you see me run,try and keep up

billbax

Hi yngwie m,

If the problem is the same with your other GK3, then I can only assume the problem is coming from the 13pin cable or VG-88.  The VG-88 13pin connector's power pins 12 & 13 and ground shield might be intermittent.  If a any of these pins connections are just slightly connected, there might well be a boom.

If you have a multi-meter you could solder a wire to both probes and check VG-88 voltages.  Black probe to ground or VG-88 case/mono guitar out socket, and the red probe into VG-88 13pin socket pin 12.  Pin 12 is +7vdc and Pin 13 is -7vdc.  Whatever you do, please don't let either of the pins connect with each other or to ground!!!

Air dust the VG-88 socket and if necessary open up the VG-88 and check the socket pcb track connections  (all of them) and look out for small cracks in the pcb tracks - magnifying glass again. May as well check the power supply at the same time.  Look out for bulging capacitors.

That's my lot for now, and be very careful and patient.

Bill

yngwie_m

Ok billbax, I will look into it and get back to you. Thank you again.
I am a bomb tech.If you see me run,try and keep up

billbax

Hi Yngwie,

Just to refine things a little.  An intermittent break-make with contact pins 1 - 7 will produce a clicking or scratching sound.  Pins 1 - 7 are analog guitar signals.

Pins 8 - 13 and ground/screen. Intermittent break-make with these contacts will generally cause loud sounds, possibly the sound you have already explained.  Pins 8 - 13 are for switching and power supply etc. Any break-make with these signals will definitely make loud noises.

You could try removing the GK3 pcb and pickup sensor from its case, placing it on a non-conductive surface. Then try tapping the pcb and sensor, if the problem still exists, you can then try a wiggling the sensor connector, 13 pin cable/socket, 3-way selector and the volume pot. It's possible a few wiggles might find the problem. Also check the GK3 socket's pcb tracks for small or tiny breaks (magnifying glass required). Finally, and bleeding obviously, check your 13-pin cable.

If any of the above doesn't show up the problem, it's time to move onto testing your VG-88.  Do you have another v-synth to try out?

Regards,

Bill