Hitachi HT 354 tonearm grounding problem

[12xu92]

Hey there Audiokarma, first time posting, I've tried searching the previous threads and i can't find a scenario that fits my exact problem. So, here it goes. I bought this turntable off of craigslist and it is in great shape, with what appears to be a brand new ADC XLM improved MK II stylus, for $150.

The problem is, there is a very noticeable ground hum when the turntable is connected to my receiver (currently a Pioneer VSX 4800. I also tried it on my HH Scott A-457 which is getting repaired now). The hum is present when the TT is idle and when a record is playing, causing distortion of the music. The hum decreases greatly, almost to non existent, when i physically touch the tonearm with my finger.
I have tried the following fixes:
-trimming down the ground cable and connecting it to other other spots on the receiver.
-plugging the TT into a grounded power strip.
-rigging an alternate ground from the TT to the receiver
- running wire from a screw on the base of the TT to the receiver ground.
-removing the headshell and cartridge, separately ( the hum is still there even without the headshell)
-separating the TT from the speakers and receiver to the maximum distance the wires would allow
-different outlets, with and with out the power strip

My educated guess is that there is an issue with the grounding on the tone arm specifically. I'm looking for a solution of any sort that could solve this because the TT is in great shape and I think it would sound great if the issue was resolved. I'd appreciate any help or advice i could get, thanks.

 

[Balifly]

Hey there Audiokarma, first time posting, I've tried searching the previous threads and i can't find a scenario that fits my exact problem. So, here it goes. I bought this turntable off of craigslist and it is in great shape, with what appears to be a brand new ADC XLM improved MK II stylus, for $150.

My educated guess is that there is an issue with the grounding on the tone arm specifically. I'm looking for a solution of any sort that could solve this because the TT is in great shape and I think it would sound great if the issue was resolved. I'd appreciate any help or advice i could get, thanks.

Welcome to the AK turn table forum.

Four item to check - remove the headshell and look into the cavity of the tone arm.

There should be four spring loaded pins inside.

Probe them with a tooth pick or something similar.

They should be springy and protruding fully making full contact with the corresponding pins in the headshell.

If they are not, that may be what is causing the hum.

 

[12xu92]

Ok, I gave that a shot. Unfortunately/fortunately all 4 pins retract individually. It is worth mentioning as well that the humming is persistent when the headshell is removed.

 

[Balifly]

Ok, I gave that a shot. Unfortunately/fortunately all 4 pins retract individually. It is worth mentioning as well that the humming is persistent when the headshell is removed.

Next outside item to check are the RCA interconnect cable and the two RCA plugs....

Then the headhsell screws and cartridge - post some close up pictures of the headshell unit if possible.

You want to make sure that the screws are not touching the cartridge body.

You may have to go inside after that.

Best of luck!

 

[12xu92]

Here are a few closeups of the head shell. The RCA cables look fine.

 

[desertrat748]

Try changing out those headshell screws with either nylon screws or some that are smaller in diameter. With all that you have tried, I'm guessing it's in that headshell, or something internal with the cart itself. Do you have a different headshell to try?

Edit: If no luck with headshell, try opening up that turntable and looking where the ground is tied down, pcb? It may have a poor connection, solder joint?

Good luck with this!

 

[12xu92]

Thanks for the advice so far. One question, if the hum is present when the headshell is removed, is that still indicitave of a headshell issue? I'm looking into getting some smaller screws/ a separate head shell to see if that fixes it.

I'm also starting to think it is an issue with the tonearm inside the TT. Might just pop it open have a look.

 

[desertrat748]

I wondering if you should have any hum without the head shell .. I think not. But I have picked up hum when changing out shells on the fly, but only when I was handling the tonearm.

Thinking maybe you should pop it open and trace down the tonearm wires and the ground. If that’s a problem then you would have it no matter what.

 

[12xu92]

So here it is, all opened up. Anything jumping out? Everything seems to be connected.

 

[desertrat748]

I can't tell where the ground wire is connected after that board. It's good to eliminate any possible problems while you are in there. Follow the ground wire and see how well all the solder joints are with it. If it is all good, button it back up and focus on the cart.

Again, I would use nylon screws on that cart and headshell and even swap it out for a different headshell if that doesn't work. Hardware store will have them or some that you can use.

 

[desertrat748]

Thanks for the advice so far. One question, if the hum is present when the headshell is removed, is that still indicitave of a headshell issue? I'm looking into getting some smaller screws/ a separate head shell to see if that fixes it.

I'm also starting to think it is an issue with the tonearm inside the TT. Might just pop it open have a look.

I can't answer that as it all depends. Too many variables to say "yes" or "no". Smaller screws may not help at all. Need some that don't conduct, like nylon.

It could be the cart as some carts will hum if you make a "ground loop" by using metal screws and touching the cart body. I'm thinking it's a ground loop problem. Search on it and you can see what you think.

I use hum bucking carts like Empire. Grado and I think Stanton may have had hum issues on certain models, I can't remember which ones had hum problems but some did. I don't know about ADC.

 

[12xu92]

I can't tell where the ground wire is connected after that board. It's good to eliminate any possible problems while you are in there. Follow the ground wire and see how well all the solder joints are with it. If it is all good, button it back up and focus on the cart.

Again, I would use nylon screws on that cart and headshell and even swap it out for a different headshell if that doesn't work. Hardware store will have them or some that you can use.

Everything looked fine as far as grounding went. I'm going to focus on the headshell, like you said. if that doesn't work, i give up haha.

 

[desertrat748]

Everything looked fine as far as grounding went. I'm going to focus on the headshell, like you said. if that doesn't work, i give up haha.

Dont give up. You are going to solve it and then laugh once you figure it out. I can't ever make friends, but if you have one of those with a stereo system, ask them if you can try it out on their system or give you a hand with yours. Sometimes just having a 2nd person there can help with something you are overlooking.

I'm reading my new book "How to make Friends". Looking forward the 2nd book in the series, "Friends, How to keep one"

 

[12xu92]

Dont give up. You are going to solve it and then laugh once you figure it out. I can't ever make friends, but if you have one of those with a stereo system, ask them if you can try it out on their system or give you a hand with yours. Sometimes just having a 2nd person there can help with something you are overlooking.

I'm reading my new book "How to make Friends". Looking forward the 2nd book in the series, "Friends, How to keep one"

I actually have had the turntable on a friend's system, same problem... I will look into the headshell matter and see what happens. I'm sure you have plenty of friends dude, you're a friendly, helpful guy. Those are the best traits to have in a friend.

 

[desertrat748]

I actually have had the turntable on a friend's system, same problem... I will look into the headshell matter and see what happens. I'm sure you have plenty of friends dude, you're a friendly, helpful guy. Those are the best traits to have in a friend.

I've been looking around for you a bit. It could be the cart's build and how it's shielded against hum, or the lack thereof.

I do have a JVC LF-41 that hums with every cart I've tried. The only cure I've found for it was to run a ground wire straight from the tone arm ground inside to an actual ground from the wall socket.

I just wired up my own special wire for this purpose. Grounding it to my preamp, or Amp, or anything other than the wall outlet ground would not work. It hums whenever I tried grounding anywhere else. It too would stop as soon as I touched the tonearm or headshell. I think it's due to the headshell being painted in metallic paint but what do I know? All my E.E. courses were almost 40 years ago and I never used them much in real life.

 

[desertrat748]

P.S. I know it sucks if you really like that Hitachi. I love them and the JVC too. The JVC has the lowest speed fluctuation of any table I've owned. Silly low like a 1200 MK2. My Hitachi 353 is the 2nd lowest and I love the sound I can get from it. Tone arm is just right for some of the carts I like to use.

Am I correct with the fact that you tried another cart and there wasn't any hum? I'm reading too much to remember.

 

[Musicale]

It is an Hitachi turntable problem. Some bad design of the electronics board and the electronics of the motor. The only way to overcome the hum problem is to use separate single audio cables from the Turntable to your amp. Audio cables that come in pairs, like red and white, no good. The best to use is single video cables, yellow RCA connectors. Use one for the right channel and a separate one for the left. 2 cables. Video cables are better too for audio as their capacitance is much lower.

 

[RincewindTVD]

Sorry to necro this thread, but I probably know the issue, and the fix; I will put the info here in case anyone finds the same issue in the future.

I've got the same turntable, cheap from facebook marketplace. Someone had modified the wiring (unrelated to the hum, looks like they did it to run the ground through the left rca shield instead of a separate cable), so I was suspicious and wanting to get it back to factory.

Having pored over the service manual, the issue I had was that there needs to be a connection from the ground for the tonearm to the metal ground plate that the rest of the mechanism sits on.
I don't know if the foil coated cardboard shield was supposed to be this connection (it has as screw connected to the tonearm ground, and a screw connected to the ground plate), but it was not connected for me (confirmed with multimeter).

I made a short wire with connectors on the ends for the screws, put one end under the screw on the tonearm wiring board (it's connected to the tonearm ground), and the other under the screw that attaches the shield into the ground plate.

My mysterious hum vanished, and now the connections match the service manual wiring.