Tonearm bearing repair

[JP]

They’re such beautifully made arms. My EPA-500 has the gummed up VTA like I’m sure most unrestored ones do. It made my other tonearns feel a bit toylike.

Later production units used silicone oil on the helicoid. As long as it's not too difficult to turn I leave it alone. Earlier ones with grease are an entirely different matter.

For this arm it was cleaning and re-lubing the AS knob, checking the bearings, and re-gluing the VTA adjustment ring. I typically always re-do that ring as the glue that was used turns to dust eventually.

They are fabulous arms. I hope to get back to my upgraded version soon.

 

[JP]

Here's something you hope you never have to do. What a bear. Got her running like new again, though.

 

[golana]

Ouch, delicate surgery.

 

[BillWojo]

As a machinist, your making me nervous JP. Was the top bearing frozen in place?

BillWojo

 

[JP]

Made me nervous too.

Pin retainer and jam nut are a bronze alloy, so rather brittle. These typically had a dot of glue used as a thread-lock. On this one the threads were drenched in glue. Combined with corrosion from being soaking wet at some point made this one hell of a job. I managed to get the vertical pivots apart with minimal marring, though that required heating the part with my soldering iron to a point where I couldn't hold it in my bare hands, backing it out around a turn, and repeating until loose.

The top wouldn't budge, and the slots broke off. The pic is me taking it down to remove the jam nut. Next was a 1/8" end-mill to drill out the retainer, which is M4, so only 0.825mm clearance on the diameter. After that I had to scrape as much of the remaining brass away as possible to get it to a point where I could chase it with a tap. Due to the glue there was no pealing out what remained.

In the end one thread turn was damaged for about 1/8 rotation, so very minor and no impact to mechanical stability. I pick up parts arms as I can, so I had a spare retainer.

 

[JP]

Technics EPA-100 in for refurbishment. This arm has bearing damage from too much torque being applied while tightening the headshell collar, which is very common for these. They are extremely fragile arms!

This one will get Si3N4 balls which exceed the performance of the originals, and makes the arm far more resilient to handling, and even (

) mishandling.

 

[JohnVF]

You’re doing a true service to humanity by restoring these EPA tonearms.

 

[JP]

One super-tiny ball bearing at a time

 

[240sx4u]

Fascinating to watch you repair these. I have to give you credit in regards to the great photos too!

 

[JP]

Top and side bearing pins. These are spring loaded with hard-chromed surfaces. These look pretty good but I see a little surface irregularity so they'll be polished before going back in.

For perspective, the thread OD is 4mm.

 

[JP]

Fascinating to watch you repair these. I have to give you credit in regards to the great photos too!

Thanks. I'm trying to up my photo game a bit. Such nice fit finish deserve better pictures than I'd been doing. The downside is that it takes a lot of time.

 

[240sx4u]

Thanks. I'm trying to up my photo game a bit. Such nice fit finish deserve better pictures than I'd been doing. The downside is that it takes a lot of time.

I bet it's really time consuming which is why I figured it was worth mentioning.

 

[JP]

All four pivots re-balled and reassembled. The antiskate spring is greased to damp vibration, and that grease turns to glue, fowling the spring. Thats gets cleaned off and replaced with silicone oil. Antiskate dial dissembled, cleaned, and greased, and legend re-glued.

Next is some pillar work.

 

[JP]

Here's a difficult-to-get top-shot of the pins. The dark spots you see around 6 o'clock are indentations from the balls. If the bearings are adjusted too tight shallow troughs will form, otherwise the damage is from force. On the far right pin you can just make out another indentation at 9 o'clock. To get proper performance from these arms the pins need to be polished out to remove these surface irregularities.

 

[JP]

Bearing pin; before and after surfacing and polishing:

 

[Wntrmute2]

Nice!

 

[JP]

Working on my photography today. As I work on rather small things I've decided I need to do better than an iPhone. Pictures sell.

The fruit of my experimentation today are some 5:1 macro shots of a 3/64" ruby ball bearing. Yes, I need to clean the camera sensor (swabs are inbound). If only to figure out how to clean the ball...

 

[240sx4u]

Dang, that's an impressive shot.

 

[JP]

When grease turns to glue things tend to break. Unfortunately the VTA adjustment lever on EPA-100 arms are one of those things. No sweat.

 

[240sx4u]

Your repair looks much stronger than the original arrangement. Bravo!