Micro (Seiki) BL-91 restoration

[J!m]

I know some of you guys find this stuff interesting, so I’m going to collect the pictures n stuff here.

First up: the arrival.


Very well packed with no “new” damage apparent. Platter was removed, as was the headshell and counterweight. Nice pack job.



It was supposed to be in its original box, which upset me, but then I noticed something:



I as not supposed to be getting an arm. Trading a ~$750 arm for an empty cardboard box seemed like a reasonable trade to me.

 

[J!m]

A closer look at what we have to work with here:





I see a bent balance weight shaft on the side of the arm. Bearing seems to be okay (but loose) so I’ll need to disassemble that and straighten the shaft.

Cartridge is sans stylus so I may get a Jilco for it. (Sure ones are $300) Let me know if you have an original for less than $300.

LOTS of cleaning and polishing to do here.

 

[J!m]

The plan is to add dropping resistors to take 20% off the incoming AC. Then I though it might be a good idea to go ahead and recap the entire board as well. (One and done).

Board looks fine after removing ten screws and a steel bottom cover…



MASSIVE main bearing housing on this. (Anyone who can read Japanese and would care to translate the red decal on the bottom of the bearing well, please do!)

I believe it is a “permanently lubricated” warning, but that was intended to be read in 1985, not 2022. I have heard they used leaded oil in here, which is difficult to replace now. But I’m sure we need to do something…

Steel plate will be blasted and repainted, even though no one will see it.

 

[George S.]

Many Japanese made 120v to 100v step down transformers on the Bay.

 

[J!m]

Yes, there are.

 

[laatsch55]

Do you have a variac Jim?

 

[NeverSatisfied]

MASSIVE main bearing housing on this. (Anyone who can read Japanese and would care to translate the red decal on the bottom of the bearing well, please do!)

It says, "you have now voided the warranty round eye !!!"

 

[J!m]

I do have a variac somewhere.

Packed away from the guitar shop daze…

It’s blue and mint condition. Haven’t seen it in years.

 

[laatsch55]

If you don't have a decent idea of the amp draw to scale your resistors, I would go through a variac and measure current, then you would have a pretty good idea of what resistors you need..

 

[8991XJ]

It's a tt so current requirements will be very low. Expect below 1A. Once it is converted to 120V a change notice on the back panel is all that's needed. No need to add a transformer when a resistor or three is all Jim is going to need

 

[J!m]

I have the schematic which indicates (from memory) 0.6A.

I have already selected the dropping resistors and they’re in my cart, but I want to add all the caps. I took a bunch of pictures so I can confirm values and voltage. I’ll go up on voltage but keep the original values.

 

[laatsch55]

Coolness..,.

 

[J!m]

Resistors, flush mount (voltage selection) switch and all but one cap are ordered. I had one cap in stock...

It's a power supply so I just went with cheap-n-cheerful Nichicon caps. Original are Rubycon but they didn't have all the values in that brand, so, whatever...

All voltages are now WAY over build (which was 25V rated- max voltage should be 12 volts on the board); the schematic specifies 50V rated for most of them- those are 100V (200V for the 22uf ones) now. 16V rated are now up to 35V. Metallized film caps are now 63V / 5%. I MAY not change them, but at least I'll have them if I decide to do so.

Should be able to rebuild this later this week...

 

[J!m]

Here's a copy of the original sales flyer, for the BL-91 and BL-91L (which accommodates longer arms)

Second page lists some of the arms that can be fit when you change the "board", which is a massive chunk of brass with nickel plating...

 

[8991XJ]

This is great. We have J!m showing off a seldom seen turntable that showed up at his place seconds before pics were taken and posted. Well done.

Now as to Nando and his super haul of a few truckloads of gear in great shape, ever since we talked about a special thread for this score he has gone off to other threads and is leaving us hanging. Last we saw was the ESP-6 cans and no listening impressions or other gear pics to make us drool.

We're counting on you Jim to keep us entertained cause I've slowed down here lately moving gear and getting pics. I have a pile of changes I need to make to the main rig I can't seem to get to. Come on Nando, we need to help Jim out and provide some eye candy of new to us gear. I'll try to do my part and get some pics of some new to me gear other than just the cans I posted about.

 

[J!m]

Well, allrighty then.

I straightened the counterbalance shaft on the arm, cleaned it up as best I could (some chromed parts have corrosion I can't clean off) and oiled the bearings. Now I want to qualify that statement, because a drop is about 8.4 times too much oil...

The shaft is still messed up. Even after ultrasonic soaking is acetone, and straightening, it is not unscrewing, and also I have near zero run-out on the cylinder (lock nut actually) as compared to the protruding plain shaft, yet, on the other side, where the bearing race is, I have run-out. What this tells me is that the shaft bend is within the lock nut (cylinder) and perhaps one of the two parts could be saved, but not both, taking it apart. So, we are going with it as-is for the rest of my lifetime...


I cleaned this all up and removd the screws but could not take it all the way off because the dynamic balance post is also attached to it... But I cleaned the old glue off and reattached the plastic washer with Barge cement.


The bearing is NOT jeweled, as I had thought, but actually a roller bearing...


Straight shaft with clean race...



Reasonably clean and back together.

Next the base...

 

[Bob Boyer]

Damn, Jim, that is just gorgeous. Especially love the anti-skate thread routing (if that is that that is).

 

[J!m]

The “tungsten wire” is both tracking force and anti-skate. You can adjust both/either on the fly.

VTA is adjustable but not really on the fly. The older version had that coarse thread on the shaft so you *could* adjust on the fly, but I certainly wouldn’t do it with a good record…

There is a spring in the stub attached to the wire. You increase tension to create downforce. The service manual details how to calibrate it so I’m going to do that with the analytical balance here. So when you dial in 1 gram you have one gram.

The colored lines are starting points- blue is for spherical and red is for elliptical (you can see the shape of the color indicators on top of the arm). Then you tweak it in from there.

Headshell is held with a multi-turn collet nut, so it’s very secure. The Kenwood is a bayonet type and not as secure. You can adjust azimuth of the headshell as well.

This old arm seems to have a cult following. I wish the 505L would fit. That’s the 12” version…

 

[8991XJ]

Damn, Jim, that is just gorgeous. Especially love the anti-skate thread routing (if that is that that is).

That is fishing tackle but I don't know what hooks would be used.

Pretty cool tonearm. No wonder they went further with the complications of multiple parts with the 507 and its separate vertically pivoted front arm on the horizontally pivoted main arm. Interesting stuff they were doing.

 

[J!m]

I don’t know the 507 but the 707 was what I was originally looking to get. That has a straight arm and effective mass is adjustable via a sliding weight on the arm.