Kikusui 5060A (AKA: beckman industrial 9060 ) oscilloscope problems

[soldersmoke]

I have a Beckman Industrial 5060 which is a rebranded kikusui 5060A that is experiencing a weird variety of problems.

The unit powers up, gives trace, but the screen despite being bright requires the intensity set all the way up - back it off a MM and it goes black. It also varies when playing with the timebase and if I play with the trace source, there is a specific combination (I believe AC source/Ext and Ch1/Add) that will make the display very bright. It's also giving me half-faded trace, half trace missing (fades off for no apparent reason, change the volt/div and it comes back, change again and it starts moving, change back and it holds still, chaos), pushing controls sometimes makes it sputter/glitch.

Before I go and recap the PSU, I thought I would post here and see if anyone else has a Kikusui 5060 and has any schematics or ideally a service manual - I have been unable to find one online.

Any help is much appreciated and thank you in advance.

Edit: For future searchers who may find this thread who have one of these fairly rare scopes, I thought I would post the issues mine had and repairs I made.

1. Fuse holder corrosion on back side leading to poor contact and all manner of intermittant voltage related issues manifesting in random glitching, trace blurring, etc Fix: removed fuse holder, cleaned with dremel internally and replaced with proper fuse - the unit will not run correctly unless set appropriately, this is universal but some ppl dont know this.

2. Pot dirtiness - the pots on the unit needed a thorough cleaning with deoxit, I additionally cleaned with naptha based lighter fluid and small wire brush on all contact pins to ensure continuity.

3. All 3 filter caps were out of value and leaky manifesting in even more power issues. 2200uf/1000uf/47uf voltages on fuses ranging from 50v up to 200v on the 47v fuse. Fuses are AC connected off of pin 3 - 4 (I believe) of the transformer pre-rectification. I chose to replace the 47uf/200v fuse with a pair of 400v 100uf fuses and build a small pair of legs to accommodate. I did not put a balance resistor on either cap b/c this is coming off of AC, this is not the best practice, but, I did it anyway and its working fine.

There are very few resources online for these scopes, feel free to message me here I will do my best to help.

[pbarton]

There is a User Manual online https://www.kikusui.co.jp/kiku_manuals/C/COS5060A_E.pdf but no Service Manual.
However, there is a 4 page schematic for the COS5040 which probably shares a degree of commonality with the COS5060, I would give that a try.
https://elektrotanya.com/kikusui_cos5040_sch.pdf/download.html#dl
 

[soldersmoke]

Thank you pbarton I genuinely appreciate it.

After some more testing I think the root cause of the issue is really just the PSU. I was playing with it again last night and realized that turning up the reticule intensity causes the waveform to deform/go out of focus/dim/etc (go crazy) which leads me to believe its either bad (drifted) resistors in the display control block or else bad caps in the PSU leading to under/unstable voltage to the CRT. I'm going to recap the filter caps b/c its basically just a very easy job on this scope to do and see if that helps. Worst case scenario I keep it as a parts unit b/c I have another one of these thats working fine.

Sure do wish I could find a service manual with a guide to calibration and schematics. This one for the 5040 does seem very similar though and is a big leg up. Thanks again.

[pbarton]

According to the COS5040 schematic, the reticule/graticule intensity is derived from a -16V supply. The Flyback/LOPTransformer and voltage multiplier is derived from the +16V supply. The -16V and the +16V supplies come from the same bridge rectifier CR622 and the same transformer winding.
If the CRT HV generation is teetering on the point of failure, you may detect some limited interaction between the reticule/graticule intensity control and CRT trace intensity. Sounds like the HV generation circuit is close to the point of failure.

[soldersmoke]

Thanks again, I'm checking everything and will post an update if/when I get this scope sorted out.

[soldersmoke]

Changed 3 PSU filter caps 1000uf , 47uf and 2200uf and the unit came back to life perfectly. I hope this thread stays up to help anyone who finds one of these units in the future. These units were sold as Beckman Industrial 5060 's and they are in actuality Kikusui's

Very simple scopes compared to many out there, especially the tek's, solidly built and beautiful displays.