I will look into the shielding. Think I will try copper tape.
My Rega P6 turntable do not have a separate ground wire. Rega runs the ground trough the left channel shield instead. Don't know if this is ideal but Rega have been around for a long time and this solution seem to work for most people. But perhaps, because of this, I need to wire input ground in a certain way?
There aren't any in the original 834p either, and it doesn't hum.Aha. There aren't any grid stoppers
jeff
The metal around RCA connectors and the selector switch should touch the chassis ground , no problem with a metal box but as you put them on wood ... it is not clear how you did it
I followed the build instructions on the LencoHeaven forum: https://www.lencoheaven.net/forum/index.php?topic=26658.0
On first page, fourth post, it is recommended to isolate the RCA inputs, as well as the ground connector, from chassis if chassis is made of metal. Either with plastic spacers or the type of Neutrics that I use. This to control grounding and prevent ground loops. Since I use wood they are of course isolated from chassis.
I don't know if this practice is better or worse than what you are suggesting, grounding directly to chassis, but on my commercial Vincent SA-T8 preamp, all RCA jacks have plastic spacers to isolate them from chassis so I guess it is a common practice to do so.
Ah, ok! Sorry, did understand what you meant! Yeah, maybe those metal supports acts as antennas when not grounded to chassis. I need to test that!
You STILL need to check if the arm wand is also grounded to that left channel shield. Use a continuity checker to confirm first. I had a Rega arm with the internal wire not attached securely to the metal parts. Took only two seconds to check!
Ok, so I found an Youtube video showing how to do this with a Multimeter.
This is the intructions: Set multimeter to Ohms, left channel screen goes to blue tonearm wire, left centre to white wire. Right channel screen to green wire and right centre to red wire. Resistance needs to be less the 1.0Ohm.
For both RCA centers (white and red on tonearm) shows 0.9 Ohm. Seems ok.
Right screen to green goes between 1.5-1.7 Ohms. Seems to be a bit too high according to these instructions.
Left screen to blue, numbers goes all over the place, not stabilizing at all.
So I guess it needs to see a repairman or is this an easy DIY fix?
The tonearm is made of metal when grounded it acts as a shield for the exiting wires. There's a piece of ground wire that's attached to the tonearm body in the back close to the counterweight stub. Use one of your meter probes to touch the metal stub and the other end to touch the Left RCA screen to see if there's continuity. As you said Rega (RB300?) ground is attached to the Left RCA shield so if the tonearm metal body does not have continuity with the ground then the your signal wires are not shielded by the armwand. Normal arms have a separate ground wire along with the two signal cables but in the case of Rega, they attached that wire to the RCA connector. The conductive part of the whole tonearm is the counterweight stub (unless you use RB250 that has a plastic stub) because the whole arm is coated with black paint.
"G" needs to be connected to tonearm internal metal body part.
"G" needs to be connected to tonearm internal metal body part.
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First of all, thank you for taking the time to help out. I really appreciate it.
I found that I have a continuity mode with a beep on my multimeter. Did a test with left shield on RCA and "stub". There is an unstable crackling beep. However, I instead check continuity between stub and RCA +/center pin, I have a stable distinct beep. I guess I am not supposed to get a beeb from left center+ pin?
I did another continuity test on the red, blue, green and white pins on cartridge. If I understand correctly each color should correspond to only one shield or center pin on RCA? However, from white I get a clear beep from L+ but also a crackling beep from L-. From blue, I get a crackling beep from both L+ and L- on RCA. From red I get a clear beep from both R+ and R-. Green, clear beep from both R+ and R-.
If I understand correctly, this crosstalk, cross continuity, between + and - is not a good sign?
Please don't use continuity checker with cartridge installed because you're sending DC through the cartridge coil and can potentially magnetize it. The reason you're getting beeping is because beep signal is passing through the cartridge. If you're not getting a stable continuity from metal stub to Left ground then something is not attached securely. Either that or you're not holding or touching the leads securely or firmly. You should check continuity with the cartridge disconnected.
Just checking - you have disconnected the cartridge while doing this?
If so, then you should only have continuity from each colour cartridge tag on the tonearm to either centre pin or shield on the RCA - except that I think Rega wire the tonearm ground wire to the left shield.
But... it sounds like you have RF issues. One thing you could try is adding some RF shielding caps from the RCA input grounds to chassis earth. Try 10nF from the RCA input shield (gnd on the input RCAs) to chassis earth - worth a try with 2x 10nF ceramic caps.
Oh, did not know that I had to remove the cartridge. Hopefully it is not damaged (it's quite expensive). This is my first TT since I was a kid in the eighties. I know nothing of these things but I am veery glad you guys are kind enough to help out.
However, I did the continuity check again on stub, firm hold. I have a clear signal to L- on RCA. I redid the continuity check for each channel with cartridge removed. All colors tested good except blue (which also holds the tonearm ground). First I did get a crackling beep but then nothing. Also, more and more often my right channel dies completely. If I unplug Left channel and plug it back in sound often comes back. It certainly seem like there is a wire break somewhere. If I'm lucky its in the RCA plugs and I ca fix it myself by just shortening the cable a little and resolder the plugs. Hopefully it's not the tonearm. Cable seem likely.
I had not disconnected it. I'm a novice. I have now, and blue to L- is not working. The rest are fine.
But I think I might have a problem both with the TT and the pre.
I need to get some shorting plugs first. Is it required that they have resistors in them, in that case I must order some, otherwise I can make some without.