Cutterhead Stylus Screw Buzz (RCA MI-4889)

[georgefero]

Hello all,

As a total novice, I realize I still need to spend a lot of time experimenting with my cutting weight, stylus rotation, angle, etc, however there is an issue that seems to be unrelated to any mechanical adjustments or EQ & compression tweaks I could make, which is that, with even the slightest increase in the signal to the cutterhead (with my compressor output limited to 0dB just before the Rek-O-Kut amp), the screw which holds the stylus in place buzzes like crazy (sounds like a cracked bassoon reed or something), which obviously creates a god-awful noise on the embossed vinyl (more like jackhammered vinyl, in these instances). I have to keep the ROK input volume at or below a 2, and, as a result, the test cuts I’m producing so far are barely audible beneath the surface noise (which, as far as I can tell, isn’t exceptional, as surface noise goes).

Anyway, it seems to me that if this vibration wasn't happening, I could be cutting *much* louder records right off the bat, surface noise notwithstanding. I’ve found that if I grip the stylus screw head really tightly, the buzzing (which is intense!) will stop, and the direct sound of music from the stylus becomes crystal clear. I should note, I don’t feel *anything* on the outer casing of the cutterhead itself when this is happening; it’s solid as a rock. It’s just the screw and stylus buzzing, and it’s tightened as much as I’m comfortable tightening it (it’s a 70-year old screw that’s kind of bent and I don’t want to break it… yet).

So, could there be some internal mechanical issue with the cutterhead, or am I just sending too much signal to it? I want to keep working on other adjustments and properly learn the craft, but I also don’t want to waste time (and blanks) on a cutterhead that’s defective or damaged.

Any advice you can offer--including correcting my terminology where it may be incorrect-- will be greatly appreciated!

Thanks in advance,

George

[markrob]

Hi,

Is it possible your head has lost its centering and needs some adjustment. Also, if the screw is bent, maybe you need to replace it. Could be its rubbing. It doesn't take much to cause buzzing. It should be a standard US thread (maybe 0-80). What happens if you remove the stylus and only install and tighten the screw? How about with no stylus and screw present? Have you tried running with the cover removed?

Mark

[sameal]

Have you looked at the internal damping material? Be careful, RCA has a weird damping material that may have " gooed " to the little cover on the back of the head.

Like mark suggests, run it without the cover. That will probably reveal a lot of the problem.

Also, watch out for the very tiny, very brittle coil wires. No sudden movements

[georgefero]

Hi,

Is it possible your head has lost its centering and needs some adjustment. Also, if the screw is bent, maybe you need to replace it. Could be its rubbing. It doesn't take much to cause buzzing. It should be a standard US thread (maybe 0-80). What happens if you remove the stylus and only install and tighten the screw? How about with no stylus and screw present? Have you tried running with the cover removed?

Mark

Hey Mark,

Sorry for the delayed reply!

So, it still buzzes without the screw and stylus present (hadn't thought to try that), and also still buzzes without the cover off. The screw is bent, but not at any point where it is in contact with anything, and it threads in and out quite smoothly, so I don't think it's the problem. I was wrong about the input volume, I do need to run the Rek-o-Kut at ~4 for this to happen with my compressor output set at about 2, but that still doesn't seem like enough to be overdriving anything. FWIW, the audio I'm testing with is just a dummy recording of some synth horns playing chords.

In the picture below, I've highlighted in green where the buzzing originates, which is (spoiler alert) the inner casing for the screw and stylus. I guess that would be the only area you'd *want* it to vibrate to actually cut a record... Everything else is solid. The thick rubber bit on the top doesn't seem too bad, honestly, I can depress it with my thumbnail and it comes back, but it is showing some signs of age (see pic 2). Who knows what's going on with the plastic inside/around the tube...

[georgefero]

Have you looked at the internal damping material? Be careful, RCA has a weird damping material that may have " gooed " to the little cover on the back of the head.

Like mark suggests, run it without the cover. That will probably reveal a lot of the problem.

Also, watch out for the very tiny, very brittle coil wires. No sudden movements

Hey there, thanks for the reply!

Yeah, if you take a look at the pics I just posted on my first reply to markrob, the rubber damping material does look a bit cracked, though it is still a somewhat pliable. BTW, thanks for the heads up on the copper wiring! It seems to have survived my meddling (see pic 3). I just hope I'm correct that this isn't my error and there is actually a mechanical problem with the head (sometimes "nothing is wrong" is the worst diagnosis...).

[markrob]

HI,

As Sameal noted and your photos show, the damping material is suspect. It does look like the armature is a bit out of center. I've never worked on this model, but you can see the armature spring is a simple wire soldered and bolted to a tap on the right. It looks like you could adjust this, but it may make a bad thing worse if you are not mechanically inclined. Given the shape of the damping material and the age of the head, it might be wise to send it out for rebuild. Not sure who is doing these heads. Maybe check with Mike Dixon.

Mark

[georgefero]

Hi Mark,

Yeah, that's my fear, that I'll loosen something and it will crack or worse. I am mechanically inclined, but this looks like a bit more delicate a job if you haven't worked with these materials before. I might try carefully tightening and loosening the nut holding the damper and adjusting that spring (I mean, it's not like there's a warranty I can void...). Good call, though, maybe I should contact Mr. Dixon (I was going to inquire about his lathe cutting camp, anyway).

A bit of random trivia I just discovered: I Googled the name on the inside of the head cover (it says "Reclamped 1-31-78 John M. Kaar") and John M. Kaar appears too have been a sort of electronics wiz kid/pioneer born in 1908 who started an electrical engineering company in Menlo Park in 1936! So I might be about to undo the handiwork of a legend...

Thanks for your advice!

[sameal]

Zooming in on your dampening material, it was changed. That is not oem RCA. So the reclamp on that note is probably also a redamp. That coil is also redone. Ill bet he rebuilt it in 1978.

If you look at your armature its tight against the right hand (looking from the front) pole piece as markrob said. I'll bet thats your problem. You basically want that armature bit "floating" in as close too exact center between those pole pieces as possible.

In my unit all the damping was oem and basically dust. Heres the rear damper from mine

[piaptk]

hi. I do repair these cutterheads.

Looks like the centering spring has broken at some point and a real messy soldering job was done to repair it. Your first thing would be to put a stylus in there to act as a lever. Then loosen that spring screw to the right just a hair, and pull the stylus to the right, until the armature fin is centered between the pole pieces. then tighten the spring screw down. But I suspect that it will still rattle on the crusty rubber. But, if it was repaired in 1978, could still be somewhat supply enough on the inside. Worth a shot. Mike

[georgefero]

Zooming in on your dampening material, it was changed. That is not oem RCA. So the reclamp on that note is probably also a redamp. That coil is also redone. Ill bet he rebuilt it in 1978.

If you look at your armature its tight against the right hand (looking from the front) pole piece as markrob said. I'll bet thats your problem. You basically want that armature bit "floating" in as close too exact center between those pole pieces as possible.

In my unit all the damping was oem and basically dust. Heres the rear damper from mine

Funny, I did read it as "redamped" but thought I was wrong, but that makes total sense... I'll add that to my glossary!

[sameal]

Take a toothpick or similar and poke at the dampening rubber. If its still plyable, its probably alright for a bit. If its rock hard, its gotta go.

But also, 1978 was awhile ago.....

If taking the cutterhead apart is out of your comfort zone, then mike is a very reasonable and professional option.

[georgefero]

hi. I do repair these cutterheads.

Looks like the centering spring has broken at some point and a real messy soldering job was done to repair it. Your first thing would be to put a stylus in there to act as a lever. Then loosen that spring screw to the right just a hair, and pull the stylus to the right, until the armature fin is centered between the pole pieces. then tighten the spring screw down. But I suspect that it will still rattle on the crusty rubber. But, if it was repaired in 1978, could still be somewhat supply enough on the inside. Worth a shot. Mike

Hey Mike, thanks for jumping in here. I tried your suggestion and the spring screw was a tad loose already, and I was able to straighten the armature fin a tad and I tightened the spring screw down, but it didn't change much. If anything it just made the buzz more constant, like a resonant, distorted version of the music rather than intermittent buzzing. If I sort of tightened and loosened it a bit while the audio played, I could find a little spot here and there that made it sound marginally better, but only momentarily (and only while holding the screwdriver in the screwhead). So, yeah, probably a combination of bad soldering and old rubber, right?

(I notice no one has said "turn it down, dummy," so I guess I'm not crazy, after all...)

[sameal]

For me anyway, I think 90% of my problem in the beginning was being scared and not hitting it with enough volume. But also I'm using a tube p.a. head, and never going past 3 on the master or channel volume.

So i went down to a webster head so i could be destructive and figure out my system with little regard.

What amp are you running and what volume are you at?

[georgefero]

If taking the cutterhead apart is out of your comfort zone, then mike is a very reasonable and professional option.

Already boxed up! I'm usually pretty good at taking things apart and putting them back together again, but I'd hate to ruin this thing because I'm not familiar with how it all fits together... maybe I'll get some junk recorder heads and practice on those for future repairs, but for now I think I'll leave it to the pros! Thanks for your advice!
-George

[georgefero]

For me anyway, I think 90% of my problem in the beginning was being scared and not hitting it with enough volume. But also I'm using a tube p.a. head, and never going past 3 on the master or channel volume.

So i went down to a webster head so i could be destructive and figure out my system with little regard.

What amp are you running and what volume are you at?

Oops, just saw this reply... the guy who sold me the setup gave me an old Yamaha compressor rack, so I'm just running my DAW into the Yamaha (threshold zero, comp ratio infinite, output up maybe to 2 or 3), and the Yamaha (which may or may not be a decent compressor, I have my doubts) into the "microphone" input of the Rek-O-Kut tube original amp (I think the tubes are fairly fresh, maybe not perfect) and that knob is around a 4 or 5. I've actually purchased some various cables, connectors and fuses to try to use the ext. cabinet output of my Orange practice amp to drive the head, only because I kind of don't trust that old ROK amp to survive forever (or sound good). The Orange is a 15 watt tube amp, and, according to an old Rek-O-Kut ad I found, the ROK amp puts out 13.5 watts, so I think I can get away with that, but I guess I'll have to wait until I get the head back to test it out. I think I'd prefer to go solid-state, but I have the Orange amp already, so why not use it? FWIW, I think that RCA head, once it's rebuilt, will actually handle a fair amount of volume. It gets hot, but I think in 5-10 minute bursts it could be ok... I hope.

[sameal]

Yamaha makes some great gear. You could do worse.

I have no experience with rek-o so i can't really say. But I'd imagine your orange amp is eq'd for guitar and the rek-o amp would be more suited for record production. Most guitar amps have a tailored eq circuit for the instrument which might not apply to information you would send a cutterhead. I do not own either however so Im just guessing.

I got a really nice sound out of these RCA heads. I've been able to get playable results, but Im not having consistency doing it. They can handle a fair amount of volume too.

You might consider getting a webster head to play with. Their dirt cheap and dead simple. After some new damping and a new magnet I got some shocking results from one. But the coils are fragile if you take it apart, and they wrapped the terminals like 6 times each making it easy to break before removing it.

[georgefero]

It's insane how much these cutter heads cost, the more I look into it, so, yeah, I'll definitely look for one of those Websters, if anything for backup (or to use while I wait for my RCA to come back).

I thought about the eq setup on the amp, but I figure I can tweak it by ear to get a nice (or something resembling nice) sound (if it works at all)... I'm really only doing it as an experiment, since I'm already pretty sure I'm going to want to replace the Rek-o-kut amp at some point. I'll let you know how it goes!

Might be waiting until August for that RCA head to come back, anyway, so in the meantime I guess all I can do is study!

[sameal]

The webster gets some pretty bad press, and it is a pretty low grade head, especially if it hasn't been worked on. BUT that's what's great about it. You can abuse it and not worry too much.

If you get one it will sound awful for sure. So it should be seen as a learning tool. You will have to take it apart and redamp it for it to start sounding ok. Then change the magnet. My magnet was so bad in both units it barely picked up hardware.

To do all that, you'll then have to desolder the coil. That's the hardest part of all of it. Those coil wires are as bad as mic cartridge wires. Very brittle and fragile.

So only look into the webster if you want to disect it and learn about the head is my advice. You could also try your hand at building a mono cutterhead for some similar experience.

I haven't met too many tube amps I didn't like. I'd bet that rek o is pretty alright after a service.

[georgefero]

I haven't met too many tube amps I didn't like. I'd bet that rek o is pretty alright after a service.

It's true, I haven't even given the Rek-O-Kut a chance yet! A bit off-topic, but when I was younger I was never really into gear, in general, and never got my hands on a decent amp (well, I had a great one in 1997 for about half a year, but it was stolen...), so for many many years I had nothing but guitars and tape decks and then demo DAWs and amp simulators, so I am just woefully lacking in general knowledge about amplification, considering how long I've been calling myself a musician! I think I've learned a quite a bit by osmosis over the years, though, so once I get more hands-on with this stuff I'll bet the pieces will fall into place pretty quickly.

[piaptk]

@Sameal what magnet did you put inside the webster? Ive got a stack of those things and none of them are even marginally loud enough to use.