My 1991 SSII picking up mad RF signals...

Hungarian_G

Hungarian_G

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Hey everyone...

I am having an issue with my '91 SSII. When I plug in and play, I seem to be picking up pretty audible RF signals (depending on my EQ, to the point where I can make out the words of the songs!). Passive mode is fine though.

I've put in a fresh battery, tried multiple A/C outlets, and even different amps (just in case), but it seems that the bass is the issue... and I can't recall having this issue until recently (I was out of town for over a month and didn't play for a while).

The cavity looks well shielded, my amp (Markbass LMII) and cab (Eden XLT) are doing fine, and when I unplug the bass it goes away... what am I missing?

Any advice would be greatly appreciated.
 
could be grounding in the amp/building/guitar... faulty power cable or plug board .. have you tried a different bass in your amp or your bass in another amp..just to rule out as many things the simple way....
dry solder joint on the ground wire in the bass??
 
Something has changed to make this start happening. Maybe the radio station has beefed up it's broadcast power. Try to find the station on your radio(Start on the Am stations). Try reversing the ground switch on your amp or moving the amp to a different room or even a different house. The fact is that you now have a radio receiver. Or maybe a neighbor has one of those fm transmitters hooked up to an Ipod. These transmitters are available with insanely high power. I have also seen where a pickup has started to go bad and causes this type of problem but usually the bass sounds weird at that point. Remember when Gilligan's head became a radio station because of his fillings??
 
Thanks for the advice everyone! I will try to reverse the ground switch and see what happens. I've tried other A/C outlets in the apartment and it still happens... maybe I need one of those "clean" A/C power bars? It only happens with this bass... so maybe I will get the cavity shielded with copper foil (as it seams to only really happen in "active" mode). I'll keep you posted. Thanks again!
 
Here is the answer I got from mr Vlado Hansal for you:
Dear Florin,

Problem he has, is RFI (Radio Frequency interference).

RF (Radio Frequency) is very high, above human hearing, electromagnetic signal. It´s not sound we here. Its only signal which carries the sound signal we hear on AM and FM as radio sound , or we see as picture on TV. Normally this is no problem. But sometimes it is possible, that bass or guitar pickups, passive as active, or Guitar EQ , pick up this signal, and decode the sound info, carried by electromagnetic waves. When this happens, Instrument work like radio receiver. This can happen , if you play near transmitting tower of radio station, because near the tower this signal is very strong. It is called RFI - Radio Frequency Interference. It is normally, that some instruments have this problem, and another one don´t. That are a lot of causes responsible for this effect.

Help for active Instruments:

1 ) Move the wire of electronic ,in another position, and check if the radio signal go off. If this don´t help, go on with 2. For this He must be fit in HF Electronic.

2) He need:

a) one FM ferrite bead over 100MHz or wideband ferrite bad with 1,5 mm (.59”) hole.
b) one AM ferrite bead about 1MHz, with 1,5 mm (.059”) hole.
c) one 47 pF capacitor
You can get this over electronic parts shops.

PROCEDURE

1) Cut the input lead (gray lead) that goes from Volume/balance /pull-push Pot ,to the EQ PCB, about 20 mm ( ¾”) from the point, at which it enters into the EQ PCB connector.
2) Strip about 1,5 mm (1/16”) (very short) insulation from both cut ends.
3) Thread FM ferrite bead on the wire stub coming from PCB, and push it to PCB connector. It should touch the connector.
4) Now thread AM ferrite bead on the wire stub coming from PCB, and push it to the first bead. It should touch the first ferrite bead.
5) Fix them with drop of glue, so that they can´t mowed on the lead.
6) Now solder the two cut ends of gray lead back together.
7) Solder a 47 pF capacitor from this rejoining point to the ground (bottom plate of potentiometer).Take care that the capacitor leads are extremely short. (less than 1,5 mm (1/16”), and the solder point (leads and capacitor) are small as possible.

It´s very difficult to solve this problem. If he is not fit in electronic, the best way would be ,to go to guy with experience with this problem, because also local conditions, has influence to this. Radio ham guy ,from his district, would be the best solution.

Best regards
Click to expand...
 
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