replacing tonearm question?

Simao, it all depends on the geometry of the tonearm's and their base configuration. You have to take the Sumiko off and look at the hole size in the arm board. If the Jelco requires a bigger hole or a slightly different position to get it's overhang right you will have to enlarge the hole then see if you can mount the Jelco without an ugly result. The cleanest way to do things is always by getting a new arm board which I am sure VPI can supply. You can also make one yourself by using the old board as a template. If you do not have the capability to do this any wood worker with a drill press can do it for you.

Thank you, mijostyn. My existing armboard is acrylic and there's a discussion either here or on the Hoffman forums with links to a shop that could make me a new board. Would you recommend acrylic or wood?

The pivot to spindle distance of Sumiko FT-3 is 221.7mm, and the Jelco 750 and 850 is 240mm. I think a new armboard is required unless you use a tonearm with same geometry (e.g. clearaudio) than you can use the existing armboard with some work.

https://www.vinylengine.com/tonearm_database.php

If you are going the Jelco route, get the 850. It is far better for not much more money.

@imhififan Thanks for that! That's exactly what I needed to know. And @noromance, thank you as well.

I would plan on buying a new armboard as well if you are going this route. 

The FT3's mounting distance and bolt pattern are both different from the 9 inch Jelcos, which use a Linn mount and have a 214 pivot to spindle (as opposed to the 221 for the FT3).

I've owned and used both arms, as well as a Jelco SA-250, which shares geometry with the 9 inch 750D and newer 9" Jelcos. 

the 9 inch Jelcos, which use a Linn mount and have a 214 pivot to spindle

@hdm , thanks for the clarification, 240mm pivot to spindle is for 10" jelcos!

I just ordered a Jelco 850M (10") arm, set to arrive today. Forgive my naiveté, but could I simply spin my existing armboard around so the holes for the Sumiko are now towards the front of the tt, and drill new holes on the part of the board towards the rear?

Or is that going to compromise structural integrity of the board?

Dear @simao  Ask directly to VPI.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Yes you can! No it won’t!

@yogiboy Thanks!

@simao

I don’t understand the choice to replace the Sumiko with a similar apparent tonearm always produced by Jelco.
If you need an upgrade to be such, the leap in quality and cost must be proportional and substantial, otherwise it is better to keep what you have with you.
The other way around, if you want to replace the tonearm for incompatibility with the cartridge or the cartridges that you have then the switch with the Jelco can have logic.

Hey best-groove ,
Good point there, but the FT-3 is twenty years old, is out of damping oil, and lacks the VTA adjustment. It's simply showing its age. I got the Jelco for a great price and it'll be a way for me to get some experience installing a new arm.

I run either a Hana SL or a Benz Ruby for a cartridge, depending on the record and my mood. 

@simao

20 years? Little thing, the arms are not changed for so little, everything can be repaired if you have a pinch of DIY.
See here if the lifter drops too quickly you can disassemble it and insert new silicone grease to put it back into operation.

I have tonearms of 40 years and over (Technics Epa 100/Epa 500, Denon 305/309, Sony PUA7, Acos Lustre, Victor UA 7045 and others .... but I would never dream of changing them for simple problems.
A good maintenance or a revision is sufficient and the tonearms return as new for another 40 years. LOL

@best-groove The Jelco 850 is a different design and is far better than the old Sumiko arm.

@simao Are you up and running yet? How goes it?

@noromance

The friction of the bearings, which is very important, in current Jelco has never dropped below 20/25 mg. indeed, to be precise, the tonearm 850 has even worse values than 30mg. (values equal to or similar to bearings from 30/40 years ago) while bearing technology has made great strides.

I think Jelco has lain too far and is resting on the fame it has deservedly built; the manufacturer is lazy and does not want to commit himself to making innovative arms but they always appear the same for many years identical to those built for other brands.
So why is the 850 better than the Sumiko FT3?

@noromance Not yet. It just came in today and I won't have time until this weekend. Will post an update then.
@best-groove: Thanks for the Sumiko tonearm picture - that'll help!

@simao 

the photo is of a standard lifter that I have restored (it is not a Sumiko or Jelco that is exactly the same) but they are practically all the same and simple to disassemble.

@best-groove  In much the same way a 1% THD tube amp sounds better than a 0.05% THD solid state amp, the friction measurements are so low as to not matter. What does matter is how it sounds. The Jelco 850 is radically different from the other gimbal bearing models in that it uses a hardened precision knife edge. My Jelco 750 bested the Sumiko and the 850 is far better than the 750.

@noromance 

If what you say is true, then the manufacturers could use stone bearing balls carved by Fred Flinstones himself if friction isn't important.
The friction heavily affects the suspension of the head, the cantilever, the tracking, going to compromise several elements.
Every detail of an arm is important, but the bearings and clutches they possess must be taken seriously.

That is not what I said or implied. Some false equivalence in your example. My argument is that at 25mg, the amount of friction ceases to be a primary concern. Stability and control of resonance is also important. It should also be noted that these Jelco arms are relatively inexpensive so the value-performance ratio is high.

Because the cartridge has rather extreme leverage over the bearings it would take a pretty bad bearing to dislocate the cantilever one way or the other but the "noise" from a rough bearing can be transferred down the arm to the cartridge. Tap lightly on your tonearm tube towards the bearing end. If you can hear it you can also hear your bearings if they are not absolutely smooth. 
Another fun experiment to determine how well your turntable is isolated. Keep the turntable off and place the stylus down on a stationary record. Turn the volume up and listen to what you get. It should be dead silent other than the noise from your phono amp. If the cartridge is too stiff for the tonearm it will start feeding back wildly. Too loose and the tonearm will start bouncing. All this just from the energy in the room. 

Okay. Quarantine has given me the time to finally do this -- after taking care of other pressing matters, like rearranging my home office, building the boys a pirate ship, tuning and retuning the drum kit, and other really important stuff. 

I have the Jelco schematic and template and Feickerts protractor and all the necessary tools. 

Is there a helpful, step by step video anyone knows of I can have at my side in lieu of a knowledgeable Audiogon member?