Technics 1200 tonearm troubleshooting

[tuffstuff]

After searching the internet for a while I've decided to make my own post.

I bought some used Technics 1200s, brought them to a house party in their fancy road ready cases, one fell out of my bike trailer and now the right channel is acting a little funny.

It plays fine at first but after about 4 to 5 minutes of play the right channel drops out but the left is fine. If it turn the deck on and off it usually comes back. Thanks to the low resistance in the plate spin, I can catch it, turn it on and off a couple of times while tapping the start stop button and the right will come back. This is not something I want to get used to, especially for playing gigs.

I think its the tone arm but I'm afraid that it' some kind of circuit board issue. I've already opened it up and the fine RCA cables attached to the larger output RCAs in the tone arm base are still connected, so I don't think that any of them came loose when the case fell out of the trailer. I don't know the interworking of the tone arm very well so I can't say for sure that's what the problem is nor am I willing to pay $50 for a new one on ebay only to find after hours of repair work that it's some unrepairable circuit board issue.

Also the gimbel bearing got a little damaged too but I fixed that with a fine flat head screwdriver, so I know a bit of damage happened to the tone arm already.

Thanks for your help!

[Netlist]

Make sure you clean the contacts of the headshell and arm. Use alcohol and earsticks, no abrasive tools.
Use an original headshell if possible. Many Concorde-like cartridges give problems with these contacts.
Check if the wiring around the RCA plugs isn't broken by wobbling the cables. Do this with a connected system but turn the volume down low enough not to be surprised by heavy crackle in the speakers.

Apart from that, it can be the tone arm. Replace only with a new one. Unfortunately this is not cheap and it takes a bit of a habit to do that properly.

Don't look for broken circuit boards, the wiring goes straight from the headshell to the RCA via the little board in the tone arm base, which normally never breaks.

/Hugo

[tuffstuff]

I had a look at the RCA wires yesterday inside the tone arm base and they look fine. Also, it only goes out after a bit of play time at seemingly random times. Turning the table off and on seems to fix the problem. I hear a light pop in the head phones and the right channel sound is back. Last night I mixed for about two hours with out it happening and then started out this afternoon and it happened 3 times in one hour.

I'll try to clean the contacts in the tonearm and the head shell. Nothing seems to change when I swap cartridges with the other deck. So I have a feeling it won't help, also they look pretty clean.

thanks for the help!

[tuffstuff]

Wow, well I just gave them a swab down and the contacts in the tone arm were pretty dirty. I hope this works, thanks a bunch!

[dangus]

Some kind of magic contact treatment may help, like Cramolin or Stabilant 22.

[tuffstuff]

Check if the wiring around the RCA plugs isn't broken by wobbling the cables. Do this with a connected system but turn the volume down low enough not to be surprised by heavy crackle in the speakers.

I cleaned the contacts and they were dirty, however the problem is still happening. It's weird, if I fondle the wires going to the mixer the channel comes in and out but not if I directly pull on the RCA going into the bottom of the deck. I isolated the ground wire and moved it around, nothing, I isolate the RCA hold down cables near the case so that they don't move around, but rub the remaining going to the mixer and the crackle comes in and out. Before I could find out if it was just at the plugs the channel dropped out completely. I think I'm going to wire on a new right RCA plug and see where that gets me.

Any thing I should be aware of before I go that route?

[Netlist]

Cut off the RCA plugs plus some wire. My experience learned that shortening the cable 5 to 7 cm usually got the broken part out.
You will need two good quality RCA jacks and a soldering iron.

/Hugo