Early 70s Japanese hollow body truss rod

[Dazed]

I’ve recently picked a lovely old original 70s Japanese (Matsumoko) hollow body bass. The neck has a significant up bow. I was told it’s been in its case (a simple unpadded cover) stored and unplayed for over 40 years. It doesn’t look to have any damage or been damp etc. 

 

Before I do anything to it, did I once read that older Japanese basses had reverse thread truss rods?

[Dazed]

I’ll add some pictures in a bit to add some clarity and we all like a pic or two.
Looked at the neck further and it appears fairly flat but the action is crazy high. 
Its similar to an acoustic bridge, floating wooden job but with a fairly basic steel adjustable bridge sitting on top. 
Everything seems original but to me it looks like the bridge is way too tall or the neck to body fit or angle is all wrong. 

Edited Wednesday at 13:20 by Dazed

[James Nada]

If the neck is straight, it might need a shim to ensure the angle of the neck is optimised for the bridge position.

 

[Geek99]

Looking forward to the pictures 

[Dazed]

As usual I’ve jumped in probably over my safe depth… and didn’t stop to take photos to show the offensive string height.
I’ve now removed the bridge and neck to investigate. 
 

Here’s the bridge removed. 
 

 

 

And then separated. It has thumbwheels to raise or lower the steel part. 
 

 

I wound the thumbwheels as low as possible and even removed them so the steel part sat on the wooden part and I could still easily slide a finger between the fretboard and strings. 
 

The lever part on the end of the bridge is a built in mute. Really good idea and very simple, surprised no one has continued with that design, it isn’t something I’d seen before. 

 

 

Onto the neck now. It looks as though it may have been removed in its past. 
The heel end has a square hole, no idea if the factory did this or someone after. Not sure what it’s purpose is as the adjuster is at the headstock end. 
 

 

The neck pocket is already shimmed, it’s at least twice the thickness of a business card and is plastic or

aluminium. 

 

 

 

 

So as the string height around the 15/17th fret is about a centimetre, would another shim resolve that?

Edited Wednesday at 18:01 by Dazed

[Geek99]

@Bassassin

 

[Hellzero]

You could try those shims dedicated to 4 strings basses, Darren.

 

https://www.amazon.co.uk/Electric-Ensures-Proper-Contact-Eliminates/dp/B0F62G3F3C/

 

The 1° shim should be good, but you can stack them, just in case.

[Dazed]

Thanks Tony. I’ve seen shims in the past on other basses I’ve had. Would they make that much of a difference to the string height though?

 

Tomorrow I’ll put it back together and add some pics of it with the strings

upto tension and roughly tuned. 

[Hellzero]

Yes, they will Darren.

 

With a 1 degree shim, you'll have to raise the bridge around 1 centimeter, so around what you need. 😉

[Hellzero]

The formula is very simple: length x sin(degree), so assuming the length from the nut to the end of the neck is 59 centimetres, you'll get an elevation of 1.03 centimetres at its end with a 1 degree shim.

[Dazed]

I’ll look at getting some of those hopefully resolve the issue. 
 

Ive been researching the strings it came with. I think they are Roto Trubass? Black possibly nylon with gold silks. Online spec says they are low tension but really don’t feel it - 65-115 gauge! Could they have pulled the neck? It’s a really light hollow bass. 

[Hellzero]

The Sean Hurley Fender mute is quite similar...