mission 774 tonearm restoration

[Ant]

Ordered some brass rod of the correct diameters for the damping paddles, found the correct dimensions for them on line. Also ordered some 50000cst silicone fluid from a radio control car place. Apparently its sold as diff oil.
Also fixed the arm lift bar

I also ordered an elipson test record off analogue seduction because i was curious about the resonances in the arm and what the damping does to them. I found out that the external sound card i bought for the kids pc has a phono stage built into it, so im wondering wether audacity or rew would see it and i could use it to see what effect the damping has on the signal using a sweep and/or pink noise off the test disc. We shall see.

[IslandPink]

I can't see where the pivot is, in relation to the counterweight centre.
I wonder why the damping and paddles are required. I have a theory, but will let you answer !

[vinylnvalves]

People cut up the wire off big bulldog paper clips to make the paddles, for the missions. The ends where they go into the spring steel bit are bent to the right shape. Think it I read it in an article on vinyl engine.

[Ant]

Got the paddles made this morning, the brass rod I ordered took forever to get here for some reason. Paddles are different measurements, which I got off vinyl engine. The first for high compliance is 1mm diameter, 15mm long, 12mm deep, by 2.5mm for the bit that sticks to the right in the bath. The medium one is 1mm diameter, 15mm long, 15mm deep, by 5mm sticking off to the right. The big one for low compliance carts is 2mm diameter, 15mm long, 15mm deep and 5mm sticking off to the right.

Mission 774 tonearm restoration by anthony cresswell, on Flickr

So it would appear that the fluid level is meant to be deep enough that the chosen paddle has the same length of paddle sticking down into the fluid as it has sticking to the right to give equal damping in the vertical and horizontal planes. On a flat record.

The high compliance paddle has 2.5mm into the fluid and to the right, the medium 5mm in and to the right, and the low compliance one 5mm and 5mm but the diameter is doubled.

faffing with the fluid level will alter the damping ratio between the vertical and horizontal, and its difficult to gauge how far into the fluid the paddle is. perhaps I should have marked the paddles with a line so I could tell when it drops in to the same depth as the bit that sticks out to the right. Although as the arm rides warps the damping level will change in the lateral plane because the paddle depth changes. Not by much because of how close to the pivot the trough is, so maybe that's largely irrelevant

Mission 774 tonearm restoration by anthony cresswell, on Flickr

Haven't listened to it yet, I've put the high compliance paddle in it for the empire cart, we will see if there is any difference. I also got the test record so I will see if there is anything I can see when I have a play with the external soundcard. If I can get it to work with rew. Still can't get the mass ring off the counterweight, more thought required..

Onwards!

[Ant]

Interesting.
The damping appears to remove some crap and hash from the top making things more defined, and remove some overhang from bass drums, but also leave things abit one note and thuddy. The balance has shifted from a little bit of bloom in the lower end, probably about 500 to 1k ish, fairly open and pretty neutral without damping, and gone to an odd mix of slightly thuddy bass, thick mid but with defined treble. In a few words, it sounds odd.

Practically exactly the same sound that perplexed me so much with the unipivot. This time though i can alter the fluid level in the trough to tweak the lateral damping, the vertical is what it is. The unipivot was a different story.

It will take some perseverance to get the level right.

Last thing that i need to do to complete the restoration is to see if i can get either a reproduction of the sticker thing that says mission on it to go on the end of the arm, or fit some kind of cover over the hole in the end of the arm wand

[Ant]

Finally got the mass ring off the decoupled counterweight.
Tried penetrating oil, nope. tried putting it in the freezer to get it to free up because i couldnt apply heat to it as i didnt want to damage the rubbery decoupling material, nope. tried bashing a sharpened jewellers screwdriver into the top of the grub screw to create a slot in it to enable the use of a screwdriver to get it out.. nope.

So had to get abit brutal with it and use a puller to brute force it off. Had to put a coin over the centre of the counterweight for the puller to bear against and then just rag it off. Someone had really heaved on the setscrew

It did mar the finish on the counterweight a bit but nothing a lick of paint wont fix.

I then had to drill the grub screw out and re tap it for m3 as it still wouldn't come out.

Id have preferred not to have to do all of this, but it was either that or it stayed where it was.

So i have some 3mm black m3 grub screws on order, nobody will ever know...

Last job is the replacement of the 774 sticker thing....

[Ant]

More interesting.

Changed the counterweight from the rubbery damped one to the solid one and its much more preferrable to me. Its removed alot of the vagueness from the bass end and sharpened it up considerably. Still not exactly what i aimed for with the unipivot but not that far off.

Its still quite expressive, im beginning to see what shane and ali are on about, just been listening to a frankie compilation and now elkie brooks album pearls, and frankie sounded like liquid gold. The compilation is 20 tracks rammed onto one lp so isnt the best quality, but the voice was fabulous. As it should be. Elkie brooks voice is the same, very well rendered indeed. Top end is really clean, its mid are very very good, its the bass control where its, for me, performance is not quite there. Its slight lack thereof, bit of bloom, bit of overhang, a lack of precision, is where i put a load of work into the unipivot because i was obsessed with getting it to sound how i wanted

With some more work on the damping levels im sure i could dial more of this out, there is a heck of alot to like about this arm, it is mostly very cohesive, and i am nit picking based on my own personal preference.
And it is stock geometry, all its bits are stock, the wiring is the only bit that isnt.
I also found something to make a cover for the end of the arm wand, getting a new mission sticker is probably not going to happen, so i cut a piece from an old stick on aluminium badge to fit in the end.
Only added 0.2g so the arm is now finished.

Onwards!

[IslandPink]

Could you hear more tonal colour without the rubber ?

[Ant]

Im still not entirely sure what tonal colour is, but to try to explain what i mean, with the solid counterweight the nuances and subtleties are easier to hear, the start and stop of notes/hits ect is more defined. Parts bleed into each other less.

I keep saying the solid counterweight, but it isnt actually solid, it still has some damping properties because it isnt one piece, its a metal ring with a what looks like acetal inside it where the rubber is on the other one. It isnt a great deal heavier.

I found that acetal parts were quite damped compared to metal when building the unipivot, so that counterweight will probably still have damping properties, just different ones.

I might turn up a brass one just to see. I note that audio origami can supply a heavier brass counterweight so it might be worth trying one.
Depends what the thread pitch is on the stub though because i only have metric taps and all the fixings appear to be imperial. Shall have to check it

[Ali Tait]

More interesting.

Changed the counterweight from the rubbery damped one to the solid one and its much more preferrable to me. Its removed alot of the vagueness from the bass end and sharpened it up considerably. Still not exactly what i aimed for with the unipivot but not that far off.

Its still quite expressive, im beginning to see what shane and ali are on about, just been listening to a frankie compilation and now elkie brooks album pearls, and frankie sounded like liquid gold. The compilation is 20 tracks rammed onto one lp so isnt the best quality, but the voice was fabulous. As it should be. Elkie brooks voice is the same, very well rendered indeed. Top end is really clean, its mid are very very good, its the bass control where its, for me, performance is not quite there. Its slight lack thereof, bit of bloom, bit of overhang, a lack of precision, is where i put a load of work into the unipivot because i was obsessed with getting it to sound how i wanted

With some more work on the damping levels im sure i could dial more of this out, there is a heck of alot to like about this arm, it is mostly very cohesive, and i am nit picking based on my own personal preference.
And it is stock geometry, all its bits are stock, the wiring is the only bit that isnt.
I also found something to make a cover for the end of the arm wand, getting a new mission sticker is probably not going to happen, so i cut a piece from an old stick on aluminium badge to fit in the end.
Only added 0.2g so the arm is now finished.

Onwards!

Did a fair bit of research on these Ant, and the solid counterweight versions (which are rarer) are considered superior from what I read. Haven’t tried the compliant ones as both the ones I have are solid.

As for damping, what you say makes sense, however one article I read says the best sound is with the paddle just touching the top level of the silicon, which is how I have mine. Try it and see what you think