Reparare osciloscop KIKUSUI 555 ;tilt of the trace

[bogdyR]

Hi!
First of all, I want to apologize for my English, mostly through google translate.
I have no experience at all in repairing oscilloscopes, so I have a lot of experience in the opinion of some specialists.
It is about an old oscilloscope, KIKUSUI 555, hybrid, transistors-lamps, which I received and which I managed to put into operation with the help of clay1905 who is active on this forum and who put me at he provided the electrical diagrams, for which I thank him very much once again.
There is still one problem to be solved. The signal trace is inclined to the horizontal and does not line up with the measurement grid. I am adding a picture.
The trace remains in a straight line in any position, up, center or down, but inclined at about 10 degrees. The CTR is 5UP1F or 5UP7F (from the operating manual). I did not remove the tube from its support to rotate it until I run out all electrical trace rotation attempts.
I really need a professional advice on what I could do to align the trace horizontally with the measuring grid.
Please, can someone help me?
Thank you in advance
PS
If you need the electrical diagrams, please let me know!

[Grandchuck]

CRT clamp can be adjusted and tube rotated in most scopes like this

[Zenith]

With those older scopes, you can often turn the graticule by a few degrees to be in line with the trace, but as Grandchuck says, you may have to loosen the CRT clamp, turn the CRT so the trace is horizontal, and then tighten the clamp. Be careful.

More modern scopes have a trace rotate control, so you can adjust the trace from the front panel with a screwdriver.

[coromonadalix]

yep  rotate the tube to fit the graticule,  unless   if you have the service manual,  you do have an rotate  adjustment

[CaptDon]

Find out if the scope has an electrical adjustment called TRACE ROTATION. If so, try adjusting it. The associated circuit may have a bad resistor. If there is no electrical rotation adjustment you will need to physically rotate the C.R.T. by loosening one or more clamps. Be careful since the C.R.T. has high voltage on several of its connections. By all means DO NOT break the glass C.R.T. when physically adjusting it.

[bogdyR]

Thank you for your opinions.
The tube does not have the possibility of electric rotation adjustment. This is precisely the problem. I would like to avoid the mechanical rotation of the tube precisely because I am afraid of somehow breaking the tube. I understood that with an old tube it can stick to the sleeve rubber. In addition to that, I should open the electrical board behind the tube. Obviously, if there is no other solution, I will do it. But I can't figure out how it could have ended up in this situation. I think it's either a malfunction electrical somewhere on the tension plate of the horizontal deflection plates or the horizontal deflection plates or somehow moved inside the tube. If the first case were valid, it could be adjusted or repaired by adjusting/replacing electrical parts, in the second case but the mechanical rotation of the tube is mandatory. I have also heard the options for magnetizing the external protection of the tube, but it is not magnetized at the moment, and the option for the power supply voltage to ripple. I can't figure out if these reasons are true real, in the present case.
I'm going to post some pictures of how to fix the tube neck. Maybe someone can tell me what the dangerous maneuvers are when removing it.
Thank you

[bogdyR]

Aste ar fi pozele cu fixarea tubului de sasiu.

[Zenith]

The pictures are good, but it's hard to know what it's like without being able to actually examine it.

It looks to me as if the metal cover around the CRT is fixed to the front panel and can't be rotated. The CRT appears to be fixed at the rear with a clamp. I assume the tube was supposed to be able to be rotated inside the cover.

I'd remove the bezel at the front to see how the CRT is fixed there, and have a look around the sides of the tube with a torch. I guess there are rubber mountings between the tube and the metal cover. Then it's a matter of loosening the rear clamp and turning the tube by the end. If you have good luck it will turn easily. If you don't have good luck, the rubber mountings will have decayed and will be stuck to the CRT and the metal cover, and you would have to remove the CRT and replace the mountings. That's a much harder and more dangerous job.

As for precautions, you need eye protection at least. Be wary if using more than gentle force, and of course, you need to be sure everything is discharged.

I'm not sure about the metal CRT cover. They are usually mu-metal which is a special alloy used to shield from magnetic fields. It doesn't look like mu-metal shields I've seen and this was a low cost scope. It may be that it's become magnetised.

It's unfortunate that there's no maintenance manual available.

[wasedadoc]

Those two components soldered between tube base socket and surrounding PCB hint that needing to rotate the tube was not envisaged.

[Zenith]

They are not completely rigid connections and he'd only have to rotate the tube through two or three degrees, judging from the pictures.

When I use the trace rotate on a scope, it's because the trace isn't completely in line with the horizontal axis, so less than a degree out. With older scopes you could often turn the graticule to align with the trace, but this seems too far out for that.

[George Edmonds]

Hi

Please make the schematic diagram available as I cannot find a copy.

I seriously doubt that the problem is caused by tube rotation unless it was manufactured that way or unless the tube has been deliberated rotated at some time in the past.

ALL the scopes I have seen that use semiconductors use a trace rotation coil around the tube neck.  This rotation coil maybe controlled by an internal adjustment which is not marked

Good rule, do NOT buy Japanese T and M kit as service  manuals are not normally available

G Edmonds

[Wallace Gasiewicz]

George is correct, of course. 


Here is a quote:   

https://w140.com/tekwiki/wiki/Trace_rotation     

When there is no vertical deflection, the beam in an oscilloscope should trace a horizontal line that is parallel with the horizontal lines of the CRT graticule.
The magnetic field present in the environment of the CRT can cause the trace to be twisted.
There are two schemes for correcting this misalignment:

• Mechanical trace rotation: The CRT is rotated a few degrees in its mounting clamps.  This only works if the CRT has an external graticule.  The 545A uses this technique.
• Electromagnetic trace rotation: Current is passed through a coil near CRT, creating a magnetic field that counterbalances the magnetic field in the environment.  The 647 and most more recent Tek scopes uses this technique.   
  

Here is a nice picture of the board (you have to look for it int the link)   
https://www.elforum.info/topic/159463-osciloscop-pe-tuburi-kikusui-electronics-japan/#comments   

There is a Horizontal sweep balance adjust in the bottom Left corner of the board, this is the view of the back of the board, around the neck of the tube. Perhaps this is the adjust that will correct rotation?  George, please comment.

[sharow]

The 555 manual doesn't mention trace rotation, but the 558 did.


https://manual.kikusui.co.jp/NUMERIC/555_E.pdf
https://manual.kikusui.co.jp/NUMERIC/558_E.pdf

[Zenith]

The 538 manual also mentions trace rotation. It calls it Adjustment of Trace Alignment.

https://manual.kikusui.co.jp/NUMERIC/538_E.pdf

It describes the procedure and gives diagrams. There are two clamps to loosen. I don't recall a forward clamp in the pictures of this scope.

There's an easy way to find out whether this has an electronic trace rotate control, which is to look at the circuit diagram. The trace rotation is usually very simple, and consists of a pot which controls the current through a coil which fits around the neck of the CRT.

[BrokenYugo]

Be very careful moving the CRT, the glue joint that holds the base to the glass is not very strong and it will be stuck in that clamp. You may find it failed already, this can be fixed. On a scope this old I would remove the CRT to check condition of the front supports, the tube needs to be held snugly at the front and the rubber whose job that is often shrinks and requires attention. If you do remove the CRT have a suitable cardboard box prepared to safely store it in before you begin removal, do not invite a situation for it to fall over or roll off the desk, wear eye protection.

[bogdyR]

Hi!
This oscilloscope was built around 1968. It does not have a magnetic yoke for the electrical rotation of the track.
However, I solved this problem. I was worried, but things went much better than I expected.
I was encouraged by the 558 oscilloscope adjustment scheme that sharow posted. It looks very similar to the 555 adjustment.
I put some pictures where I marked the places of action.
I loosened the screw that tightens the clamp around the neck of the tube.
I turned, very easily, the base of the tube with the help of a special tool with two pins, which I made. These two pins go into the two holes of the ears of the base (indicated). At first I didn't realize what they were for these holes. The rotation was extremely easy. I did not loosen or weaken any other part.
Thank you all.

[bogdyR]

Aceste sunt pozele

[jdragoset]

Those oval shaped holes in the shield behind the front panel are finger holes for rotating.
As long as the base to neck glue held, no problem.
be careful retightening the clamp screw.
Good fix

[Zenith]

I turned, very easily, the base of the tube with the help of a special tool with two pins, which I made. These two pins go into the two holes of the ears of the base (indicated). At first I didn't realize what they were for these holes. The rotation was extremely easy. I did not loosen or weaken any other part.
Thank you all.

I suspect the holes in the base were a hangover from the days of valve bases to be riveted to a chassis. I recall one of the (very inadequate)  Kikusui manuals said the CRT should not be turned by the base. I think you've had some luck in that nothing was stuck by being degraded by age

Making a special tool is the mark of a proper engineer. All credit to you!

Anyway, a success story, which is a thing to be rejoiced in. I hope our various contributions helped.

[bogdyR]

Hi!
It was just the very, very great ease with which the tube was rotated that surprised me too. I am sure that the holes in the ear are made precisely to put a special tool with two pins in them to create a torsional moment and to be able to rotate the tube more easily .There are also 2 rivets that Zenith talks about and which can be seen at the bottom of a picture I posted.
In the front part, after removing the cover attached with the 4 nuts and removing the grid and the green filter, you can see between the edge of the tube and the metal case, a kind of plush material that helps it slide more easily. I think that this material, like a sleeve, also has the role of protecting the tube from mechanical shocks.
I give these explanations to help those who have such a problem with such an oscilloscope.
Thank you once again for the ideas you gave me.
I still think that I still have some adjustments to make to this oscilloscope and I might call on your knowledge.