Mission 774 Arm; can it run a moving coil cartridge.

[Jac Hawk]

I’m just about ready to do the rewire, but instead of tagging the ground wire to on of the negative cartridge wires I want to run a separate cable to earth the tonearm, my idea would be to replace one of the hex screws holding the cable connector in place with one about 5mm longer, run the earth cable from the arm to it and mount the screw upside down, on the other side attach the outgoing earth to the same longer screw holding it in place with a nut and washer, my question is does anyone know the origin screw size?

[worrasf]

I’m just about ready to do the rewire, but instead of tagging the ground wire to on of the negative cartridge wires I want to run a separate cable to earth the tonearm, my idea would be to replace one of the hex screws holding the cable connector in place with one about 5mm longer, run the earth cable from the arm to it and mount the screw upside down, on the other side attach the outgoing earth to the same longer screw holding it in place with a nut and washer, my question is does anyone know the origin screw size?

I've rewired four 774's. It's pretty straight forward as long as you use a "pull through" on the existing cables. I've found Cardas to be very forgiving and it takes up the requisite bend from tonearm to red plug nicely without interfering with the bias. I've always used the existing tag at the front of the arm for grounding and never had any issues - even my Decca Supergold is hum free. The original grounding works very well especially if you remove a small area of black paint on the undersurface of the arm tube where it's clamped to the pillar/bearing assembly.

I'd be a little wary of adding a separate earth wire from the arm to that hex bolt in case it interferes with the bias. The tonearm wires need to be totally passive between arm tube and red connector. Just my two penneth of course.


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[Enossification]

It certainly used to back in the early eighties. I remember it being a first class arm.

[Jac Hawk]

I'd be a little wary of adding a separate earth wire from the arm to that hex bolt in case it interferes with the bias. The tonearm wires need to be totally passive between arm tube and red connector. Just my two penneth of course.


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I thought about that too, however I’m using a piece of the old loom as the earth it’s very thin and if I loosely coil it around the 4 cartridge wires it shouldn’t cause a problem

[Qwin]

Hi Mike
The arm tube does not have a good ground path to the base plate.
Painted tube/clamp and greased bearings don't help.

What I did........
The alloy cartridge mounting block has a ground wire attached to it. This wire attaches to one of the cartridge tags/pins then on through the arm.
I disconnected the grounds from the tag/pin and soldered a new length of wire to the short length from the mounting block, adding fine heat shrink sleeving to the joint.
I then used the old leads, to pull this and the new signal wires through the arm, connecting the ground to a banana grounding post I attached to the rear of my TT.
If you wanted to, you could also fix a wire from the base plate to the grounding post, to fully ground all the metalwork.
To be honest, I've never had to use the grounding post, my decks plinth is Bamboo, with no electrical connection between the arm and anything else.
And as you have heard, using several Phono stages, its silent.

What cartridge are you thinking of using?

[shane]

I bought one of these kits which replaces the red plug and socket with a dual in-line 10 pin plug and socket. I paralleled adjacent pins to halve the contact resistance which gave me a five way plug, one for each cartridge pin and one for the extended arm tube earth wire from the head block. I rewired the whole thing with Satcure litz wire which sadly seems to be no longer available.

https://www.ebay.co.uk/itm/114890920...mis&media=COPY


Having the five way plug means I can wire the arm to my step-up tx for the Denon 103 fully balanced. I’ve tried to get the bugger to hum but it absolutely refuses!

[Jac Hawk]

Hi Mike
The arm tube does not have a good ground path to the base plate.
Painted tube/clamp and greased bearings don't help.

What I did........
The alloy cartridge mounting block has a ground wire attached to it. This wire attaches to one of the cartridge tags/pins then on through the arm.
I disconnected the grounds from the tag/pin and soldered a new length of wire to the short length from the mounting block, adding fine heat shrink sleeving to the joint.
I then used the old leads, to pull this and the new signal wires through the arm, connecting the ground to a banana grounding post I attached to the rear of my TT.
If you wanted to, you could also fix a wire from the base plate to the grounding post, to fully ground all the metalwork.
To be honest, I've never had to use the grounding post, my decks plinth is Bamboo, with no electrical connection between the arm and anything else.
And as you have heard, using several Phono stages, its silent.

What cartridge are you thinking of using?

Hi Ken,

What i've done is solder a cable to the earth tag in the head of the arm tube, run it through and out following the same route as the cartridge wiring, drilled the thread out of one of the cable block screw holes, crimped and soldered small circular connector to the end of the earth wire, then attach the cable with a cartridge screw and nut to the base plate with the reverse of the wiring on the other side terminating at 2 x female RCA's and an earth terminal, it works a treat. I've got my Dynavector 10x5 on it at the moment.

[Qwin]

Hi Ken,

What i've done is solder a cable to the earth tag in the head of the arm tube, run it through and out following the same route as the cartridge wiring, drilled the thread out of one of the cable block screw holes, crimped and soldered small circular connector to the end of the earth wire, then attach the cable with a cartridge screw and nut to the base plate with the reverse of the wiring on the other side terminating at 2 x female RCA's and an earth terminal, it works a treat. I've got my Dynavector 10x5 on it at the moment.

Great news, electrically what you did is the same as what I did, I just tried to use some of the original wire and reduce soldering in tight spots, but good you managed it ok.
Looking forward to hearing it.

[Jac Hawk]

Well the next NEBO isn't a million miles away, i'll be bringing this deck with the Mission arm on it and the Pioneer SA7800 amp that I got for free, which has really surprised me at how good it is, so I'm hoping it works well with the gear available on the day and it shines as well as it's done in my set ups, I'll fill the boot of the car so probably bring some other stuff too.

[Qwin]

I'm looking forward to it already Mike.
I'll bring my new LDA phono stage and the Freya+ Pre Amp, which I recently treated to some fancy output caps.
Will work out what else closer to the time.
Going to stay over this time, got a motorhome now, so will be sleeping in that.
Ha ha, just realized this isn't the NEBO thread.