Problem Toei Chassis/Tube Swap

[jerryspaghetti]

Swapped out those two caps and seen a slight increase in width but still have to push the B+ slightly to get nearer the full width.

See pics below.

Pic 1 at 76v
Pic 2 at 78v
Pic 3 at 80v
Pic 4 at 82v fills screen

It’s not perfect but you think that having that B+ between 80-82v (5-8%) will cause long term damage? Seems a very slight tweak for a perfect picture is all.

 

[gunblade]

one thing bothers me, the h.s lim and h size give a massive range yet not on this setup - something is not correct

 

[Retroman839]

Yoke magnetic field limiting
The horizontal deflection.

Incorrect yoke ?

 

[jerryspaghetti]

Those pots are nowhere near up all the way but when you increase them only the top and bottom corners stretch and you get a bow tie shaped image

 

[Retroman839]

Those pots are nowhere near up all the way but when you increase them only the top and bottom corners stretch and you get a bow tie shaped image

Can you put up a pic ?

Bow can be the magnetic field.

SanwA pfx / Toshiba pfx
Diffrent yokes. SanwA chassi
With tosh yoke Gives a spherical bowed image that can almost be corrected with the pots .. but just not enough .

 

[jerryspaghetti]

Yoke magnetic field limiting
The horizontal deflection.

Incorrect yoke ?

Pr

Yoke magnetic field limiting
The horizontal deflection.

Incorrect yoke ?

Pretty sure this is the issue. Read on previous forums that the yoke swap is the only true solution but I’m terrified to try it!

I’ve had nightmares messing with convergence before.

 

[jerryspaghetti]

Can you put up a pic ?

Bow can be the magnetic field.

SanwA pfx / Toshiba pfx
Diffrent yokes. SanwA chassi
With tosh yoke Gives a spherical bowed image that can almost be corrected with the pots .. but just not enough .

Excuse the crap Google image below but it’s this. It’s pincushion by its technical term. I’ve tried all combinations of pin cushion and Parabolic adjustment. It really it just the yoke limiting the horizontal stretch ultimately.

I really need to know if the additional 5-6 volts on the B+ is dangerous. As if it’s not it’s probably a better solution than trying a yoke swap which could end up buggering two perfectly good tubes

 

[Retroman839]

I think we need to ask

Is it not likley you have the yoke from a toei chasiss comb ?

We could Compare yokes ?

And stokes has one of these tubes also I think ?

We should try to compare our yokes

 

[jerryspaghetti]

I think we need to ask

Is it not likley you have the yoke from a toei chasiss comb ?

What’s a chassis comb?

 

[gunblade]

i doubt running the b+ at 80v would cause any problems as on 25khz it runs at 118v

 

[Retroman839]

What’s a chassis comb?

Pairing of chassis / yoke / tube.


Basically I found out that snk
Did send out mvs u4 25 with
Nanao chassis / hitachi tube

But only because toei was not avalible .

So the question is was any modification done to chasiss to match the tube yoke from the original toei set up ?

Or is it a diffrent yoke that matches the nanao ?


The hitatchi tube we both have
Is the tube that was original to the mvs u4 25 with toei.

But we have nanao .
Is the yoke the same as the yoke that’s paired with the toei ?

 

[jerryspaghetti]

i doubt running the b+ at 80v would cause any problems as on 25khz it runs at 118v

I’m weeping with joy! Thanks man. It’s so bloody close I didn’t think it would be such a big deal.

Appreciate the help massively.

 

[Retroman839]

I’m weeping with joy! Thanks man. It’s so bloody close I didn’t think it would be such a big deal.

Appreciate the help massively.

my yoke , wonder if it’s the same as yours ?

 

[jerryspaghetti]

I think we need to ask

Is it not likley you have the yoke from a toei chasiss comb ?

We could Compare yokes ?

And stokes has one of these tubes also I think ?

We should try to compare our yokes

Yeah I’ll get come close ups of my yoke but it was 100% a Toei RM251S chassis so pretty sure it’s a Toei specific yoke.

This is the Hitachi tube only. Stokes has the Toshiba Tube with Toei A252 chassis variant.

 

[jerryspaghetti]

my yoke , wonder if it’s the same as yours ?
View attachment 36183

I’ll get some close ups of mine tonight man.

 

[Retroman839]

Here is a thread with your issue ..

Arcade Otaku - アーケード オタク - Login

 

[jerryspaghetti]

Yes that’s the one I was reading for most of my info. The guaranteed solution is the yoke swap and I still might do it but prefer to source a spare yoke than pull the one off my MS9 tube.

 

[Retroman839]

I’m just curious to know if the hitatchi tubes had diffrent yokes Depending on the chassis pairing from snk when they left the factory?

If you can get a pic of your hitatchi yoke would appreciate it ..


I have wells Gardner chassis mod kits .. for pairing sega rally 3 33”.

Só modding chassis to help suit specific games screens was a thing .

It’s just weather snk we doing it when toei chassi was no longer avalible off the shelf.

 

[Retroman839]

Excuse the crap Google image below but it’s this. It’s pincushion by its technical term. I’ve tried all combinations of pin cushion and Parabolic adjustment. It really it just the yoke limiting the horizontal stretch ultimately.

I really need to know if the additional 5-6 volts on the B+ is dangerous. As if it’s not it’s probably a better solution than trying a yoke swap which could end up buggering two perfectly good tubes

Bad component in the pincushion circuit ( poss shorted mossfet )

Bad cap between mossfet and inductor ?

 

[jerryspaghetti]

Bad component in the pincushion circuit ( poss shorted mossfet )

Bad cap between mossfet and inductor ?

I’m not so sure. I think this is just the reality of using the original Toei yoke as it seems others had the same symptoms when trying this.