KIKUSUI 5060A Scope Issue (AKA: Beckman Industrial 9060)

[soldersmoke]

I have a kikusui 5060A that previously had power issues related to what turned out to be bad filter caps and a corroded fuse holder.

The same unit is displaying new issues related to its second channel.

Channel 1 will trigger when dc coupling is selected however is tracks continuously to the right, unless holdoff is turned 100% in the + direction (clockwise), and of course when this is done, changing to ac coupling then tracks incorrectly.

Channel 2 has none of these problems and behaves completely normally in both ac and dc coupling with holoff being set to the center and not used at all.

Any ideas what could be causing this?

So far I've recapped most of the unit, cleaned the pots thoroughly (could one be bad?) and of course made other fixes previously mentioned.

Any help is greatly appreciated.

Thank you all in advance.

[bdunham7]

I'm not sure what you mean by "tracks continuously to the right", can  you try a better description?  What settings are you using and what signal source?  And are you using ALT triggering to display both channels, or just one channel at a time, or ?  And as for holdoff, there is no 'center' AFAIK, it is minimum to maximum.  Normal, if there is a normal, is minimum.

[soldersmoke]

It doesn't matter the type of triggering, every type of triggering and every source causes the signal to appear to sweep to the right/track to the right, there is no ability to obtain a stationary trace and or signal. holdoff on the kik has a specific holdoff knob on it with two separate settings and with holdoff activated and set all the way to the right (maximum) the scope will maintain a stationary signal with dc coupling, however switching to ac coupling causes the scope to once again, sweep/track to the right on that channel, however if coupling is set to AC, holdoff can be turned completely off and set to neutral (center) and has no problem. It is a specific problem with dc coupling and any type of trigger settings.

I did however notice that with alt triggering enabled the display jitters and seems unstable on that channel.

I hope this helps to explain whats going on, been trying to fix this shotgun repairing components as I still have been unable to find a definitive service manual or schematic for these. Someone here posted a schematic for another closely related model of scope but I noticed a bunch of differences under close examination. Kikusui the company has been unresponsive and I haven't been able to find an old manual on ebay or anywhere.

[bdunham7]

Hmmm.

I have a very similar scope.  If yours is like mine, there is a set of concentric controls with the markings "Holdoff" and "Level", with "Lock" and "Norm" on the lower left.  Refer to photo and tell me if yours is the same or similar.  The holdoff, lock and norm words refer to the inner control (furthest from the panel, smallest, top, whatever), the holdoff, which should be turned counterclockwise until in locks in the norm position which is minimum holdoff.  Then you should forget about it.

The "Level" refers to the outer control (closest to the panel, largest, bottom) and is the trigger level.  The normal position, if there is one, is centered, which represents a zero crossing trigger.  Immediately above it is the slope switch, which determines whether the trigger happens on the way up or the way down.

Let me know what other equipment you have (sig gen, etc) and I can suggest some ways to track down the problem.  A photo of  your panel and how it is set might be helpful.  I'm still not clear on "the signal tracking right" but for now I'll assume you are in the AUTO sweep mode and the trace is not steady in one spot but is "walking" (or running) one way or the other.  If you really tried a lot of signals, I'd expect it to occasionally walk either way but mostly just be blurry.

[bdunham7]

So I just fired up my version of the Kikusui scope (it has been a while) and I was wrong about how those two controls work!  Here is the revised version:

The outer control (closest to panel) is the holdoff and should be rotated fully counterclockwise to the "normal" position for everyday use. 

The inner control  (smaller, further from the panel) is the trigger level, and when rotated fully counterclockwise it engages a switch that seems to be an auto level trigger, sort of like the the Auto P-P function on Tek scopes.  I haven't looked into it's exact feature set yet...

Let me know if you can get a sig gen and connectors so that you have a 1.2 kHz triangle wave 5Vp-p into both channels.  If not, let me know what you do have.

[soldersmoke]

Hi,

Thanks for your replies it's much appreciated and yes your scope looks exactly like mine. What I meant by sweep is basically that any signal fed into the device - all sources, 2 diff function gens + square output on scope, all track or 'move' continuously - but not b/c the signal is moving, but for some other reason. I have two identical scopes and they behave very differently and I am sure this is the one with issues.

I turn the holdoff knobs the way you've said on my other one and its fine for everyday use, I do it with this one (the one having problems) and unless it is both engaged and turned all the way clockwise it causes this jittering/shifting/tracking (whatever term you want to use) where the signal is in motion to the right - while in DC mode only.

It's a weird problem.

[bdunham7]

Two identical scopes?  Well then one is a parts scope, problem solved! 

Seriously, I'm not doubting you have a problem--especially if you have another to compare--but before you go disassembling, it would be good to know the nature of the problem as best you can beforehand.  It does sound like you may have a DC offset problem somewhere near, but before, the trigger circuit.

Can you provide the 5Vp-p triangle signal identically into both channels?  If so, I can probably figure out where the problem is with about 5 minutes of knob twisting.

[soldersmoke]

Thanks for your help with this, I had the same identical thought and since I just got a tek 2440 I decided I would shelf this thing or else use it's good channel for a monitoring tool on the audio rack, its not a bad scope at all nor is it's twin, the build quality is there, but I can only use one scope at a time and vintage tek's cry out to me - buy us! more than these. I picked up the pair of them for 50.00 each because they had really good displays and were in clean shape - nothing broken except missing the feet on one of them, the guy also threw in a pile of probes, so, no regrets.

I tried inputting the identical signal in both early on and it was how I found a whole bunch of problems I've managed to fix, recapping the units helped a lot. My guess is there is something going on with the pot or switch. When I got inside this unit I found it had a dark crud on a lot of components, I had cleaned it off, it was like hardened grease and it was really difficult to remove, maybe it did it? I don't know, it certainly didn't help.

Anyway, thank you once again for your help, I sincerely appreciate it bdunham7.