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avatar: marchem
marchem
11 posts
Replied to marchem's post on March 8th, 2018

Trying to resurrect an LS 6500. Got the elevator working and fixed a printer problem. Now I'm getting H# Count rate too low error when counting. If I switch to just plain cpm I get a count rate of zero. Suspect power supply, but everything else seems to work. Is there a separate HV supply for the PMTs? Any way to test that? I've got lots of instrument troubleshooting/repair experience, just no schematics or service manual make it tough to proceed.

SN is 7067355.  It's got the Wyse thin client.

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on March 8th, 2018
As I explained, zero counts means something is defective from the PET's on back towards the front end board. Yes, there is a separate HV power supply assembly found in an aluminum housing that 2 of the PMT cables if in to. The only issue is that it is VERY easy to load down that power supply, even with a DVM, so getting any readings can be problematic. One thing you can do is open the chassis up and make sure that there is not an excessive amount of dirt build up inside of the chassis and on the circuit board. Your LS counter is a "coincidence counter" such that both PET's need to see the light flashes within 20ns of each other to be recognized as a valid count event so one defective tube or socket assembly will prevent it from registering any count activity. I replaced a lot of PMT socket assemblies over the 23 years that I worked on them. I also replaced quite a few front end boards as there was a known defect where one of the surface mount capacitors was installed backwards and eventually failed causing the problem you are seeing. I don't know if your counter has the Singles counting option or not because it can be useful in troubleshooting your problem, too. It is difficult to do much more without eyes on so not sure what else to tell you only that PET's and their sockets were ridiculously expensive even over 5 years ago when I retired and the entire LS product line went obsolete over 7 years ago so how much help you might still get from BCI is problematic, too. Don
avatar: marchem
marchem
11 posts
Replied to dpkleessr's post on March 9th, 2018

Thanks for the info.  System is surprisingly clean and dust free.

There are two LEDs on the HV supply.  DS1 lights when counting and DS2 flashes briefly then stays out.  If I disconnect the cables to the PMTs both LEDs stay on.  If I swap the cables DS2 lights, and DS1 does not.  So the problem seems to be on the left side: either cable, socket, or PMT.  I'm tempted to dig into the detectors and see if I can swap things there amnd/or hopefully see some obvious problem, even if there's not much I can do about it.

How can I tell if I've got the Singles option?  Would that be listed in the System Info page?

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on March 9th, 2018
Check under your special programs and also in a user program where you select your counting mode. You are already on the right track as to diagnosing which side is the problem. Just be careful as the PMT's are sensitive to physical shock and exposure to sunlight and fluorescent lighting. Light shock can literally take a day to calm down. Physical shock can and does break the PMT's. Swap out the connectors coming from the PMT sockets to the front end board and see what happens. This is easier than the next step of physically swapping out the sockets on the tubes. Let me know. Don
avatar: marchem
marchem
11 posts
Replied to dpkleessr's post on March 22nd, 2018

The HV supply is working fine now, with both LEDs on steady, and a voltage of about 1100 (measured with HV probe).  I've been watching the LEDs on the coincidence/analog board; DS4 lights when it counts, but DS2 doesn't.  After swapping things back and forth between Left and Right it sure looks like the pre amp/base is the problem.  I've got a line on a replacement, but will try cleaning the old one first.  Apparently the left side gets dirty from the fan on that side and can cause problems.

I'm not seeing a singles option anywhere, unfortunately.

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on March 22nd, 2018

I never was able to "fix" a preamp by cleaning it.  Replacement is generally what you will be looking at but definitelty give it a try and you are correct in that just about everything on the left side gets messed up because of the air flow although that fan runs so slow that it really did very little cooling and I found more than a few poorly maintained LS counters with non functional fans still functioning properly.  One thing you may find that I dealt with on a regular basis is that the closed cell foam around the PMT's has degraded to the point where it really no longer acts to support the tube within the shielding to help keep the tube centered.  If you do find that it has been squeezed flat then I recommend that you replace it as this can have an impact upon the overall counting efficiency.

Don

avatar: marchem
marchem
11 posts
Replied to dpkleessr's post on March 22nd, 2018

Thanks for the tip about the foam.  It's looking a little tired, so if I do get things working I'll be sure to replace it.

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on March 22nd, 2018

If I can think of anything else then I will let you know.  It is has been around 5 years since I actually worked on one of these so talking about it is dredging up old memories.

Don

avatar: marchem
marchem
11 posts
Replied to dpkleessr's post on March 22nd, 2018

Your advice and help is greatly appreciated.  Service engineers who are willing to share information with customers are worth their weight in gold; not all companies allow/encourage it and not all engineers are willing to do it.

Rob

 

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on March 22nd, 2018
The big difference is that I retired from Beckman Coulter over 5 years ago so I have no horse in that race anymore. Do I have issues with some party service groups? Absolutely, because way too many of them have service people that are not much more than warm bodies telling end users that they know what they are doing. I have and will continue to help those individuals that I can as long as people are courteous and show at least some thankfulness towards someone that is in essence giving them the benefit of 33 years of factory trained service. Those that don't I make note of and ignore but they are the exception. One other thing you might check is the connections on the high voltage plugs for the PMT socket. They used crimp connections on the plug and sometimes soldering them brought things back to life. Just a thought. Don
avatar: marchem
marchem
11 posts
Replied to dpkleessr's post on March 23rd, 2018

Are those the connections on the socket side of the board?  if so, it looks like a tight squeeze to get in there and solder them, but I can see how that might help.

Rob

 

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on March 23rd, 2018
No, the ones at the end of the 2 pin connector attached to the thin, black coax cable that plugs into the HV power supply. The high voltage power supplies that Beckman always used were extremely sensitive to loading so a slightly higher impedance connection could cause problems. Not saying it is the problem. Just covering all of the bases as some old brain cells start firing off again. Don
avatar: marchem
marchem
11 posts
Replied to dpkleessr's post on April 30th, 2018

Finally back to working on this.  Pulled PMT base assembly out and cleaned everything up.  Put it back together and when I power it up the system start up LEDs stop on the CRT Terminal Test.  The display on the Wyse thin client shows the full screen white/yellow Wyse logo, then v4.6, then Wyse WinTerm, ica/Citrix, and finally a long white bar at the bottom of the screen.  The printer stutters for a second at the end of all this.

I've checked to be sure I didn't knock something loose removing the PMT cables.  I do have one plug that's not connected to anything where I was removing cables; it's J515, but I can't see anywhere it night go.

There is apparently another one of these on campus being saved for parts.  I'll try to track it down and see if I can borrrow some pieces for troubleshooting.

Any reason for the Wyse to suddenly fail?

Rob

avatar: LG1
LG1
11 posts
Replied to dpkleessr's post on May 4th, 2018

Hopping over from what started as a 'WYSE Terminal' post as that problem has been resolved but current problem seems to be PMT related. 

Don, to continue where we left off, I'm comfortable with instrument repair and troubleshooting this further, especiallyif there could be simple solution. I saw previous post about a piece of debris causing something similar, I did not see anything (assuming I was looking in the right spot, I was looking at the area right where a vial gets pushed up). 

Regarding some of what was mentioned earlier in this thread, I am seeing something similar related to the DS1 and DS2 lights. Seems like DS2 is lit all or most of the time and DS1 only flickers on for split second about the time a vial is lifted. Assuming the two connectors going into this box are the PMT cables. With both of these cables disconnected, DS1 and DS2 are both lit. I did not try swapping positions as the previous poster did.

You previously mentioned 'light shock', how would this occur? I did have the front cover off yesterday prior to receiving the new terminal. Although I assume if that caused light shock it should be resolved by now? 

avatar: marchem
marchem
11 posts
Replied to LG1's post on May 4th, 2018

LG1, you[re right about those cables coming from the PMTs.  Swap them and see if the LEDs switch places.  You can also try swapping the HV connections, just to be thorough.

Funny that you're problem has gone from terminal to PMT, mine the other way (although I think I've still got a PMT problem).

Rob

avatar: LG1
LG1
11 posts
Replied to marchem's post on May 4th, 2018

Hi Rob,

Yea, funny it's reversed. I tried swapping the PMT cables and the LEDS reversed - DS1 on, DS2 off. Wasn't sure what you meant by swapping the HV connections. 

Did you ever get your issues resolved?

avatar: dpkleessr
dpkleessr
970 posts
Replied to LG1's post on May 4th, 2018

Swapping out the PMT signal cables and getting a swapped out LED response is indicating which tube/socket is likely the source of your problem and rules out the front end board as being a part of the problem.  Without having replacement parts available to you makes determining whether it is the PMT or the socket that is at fault.  PMT's by themselves were the most expensive replacement part I ever replaced in an LS counter but that was due to an internal pricing issue within Beckman Coulter that they refused to correct.  You may be able to find PMT's at a much better price point by going to someone that acts as a reseller of the PMT's.  The PMT sockets are much more problematic as they were exclusive for the LS counter and they were not cheap either.  A 3rd party service group or even Beckman may be able to help you out because neither the socket or the PMT are repairable.  As to swapping out the High Voltage connectirs on the HV Power Supply, I only replaced 1 or 2 of them in the 23 years that I worked on the LS6000/LS6500 series counters and they were for outright failures as opposed to only 1 side of the piwer supply board failing.

Don

avatar: dpkleessr
dpkleessr
970 posts
Replied to LG1's post on May 4th, 2018

Light shock takes place when the PMT's get exposed to fluorescent or sunlight and it literally can take a day for the tube(s) to calm down enough to get normal counts or even a valid calibration.  It is always best to work with the PMT's under red light conditions.  I had a headlight with red LED's on it that I used when working with the PMT's in a dark room.  Not really a part of your attempts to fux your problems but some perspective on how to safely work with PMT's.

Don

avatar: LG1
LG1
11 posts
Replied to dpkleessr's post on May 4th, 2018

Okay, so information so far is indicating 1 bad PMT/socket, other PMT and front end board likely okay? 

In your experience, more likely to be the PMT or the socket? And if I were to get my hand on a replacement, how involved is it to switch one of these out? Also, we have an old LS5801 here, any chance parts are exchangeable?

Regarding light shock, does this happen when front cover is off? And is it enough to result in 0 CPM?

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on May 4th, 2018

First, light shock only happens when the PMT's are directly exposed to light such as when you are actually working to replace them and not by just taking any of the covers off of the counter. Next, there are NO major electonic parts that are interoperable between the LS 5800 series and the LS6000/LS6500 series counters. Finally, replacing a PMT is not difgicult at all and takes very little time but it does require careful handling of the PMT itself. The PMT socket replacement is much more involved as it requires taking the center rear panel off in order to get easy access to the cabling which is zip tied along its length and there is a LOT of cabling to deal with. I would be VERY careful purchasing replacement PMT's on line UNLESS they come with some performance guarantee. You will only know that a PMT is good, assuming the PMT socket is functioning properly, when you place it into the counter and power it up and then try to count samples or calibrate the counter and you MUST recalibrate the counter whenever a tube, socket, or front end board are replaced.

Don

avatar: LG1
LG1
11 posts
Replied to dpkleessr's post on May 4th, 2018

Okay, sounds like something we'll just have Beckman do. Just wanted to make sure I wasn't missing something simple.

For estimating the repair cost, would you agree it sounds like 1 PMT and/or socket is bad but the other good? Also, just for my knowledge, am I identifying the PMTs correctly in this picture? 

https://drive.google.com/file/d/1uBFxbDP2F-Im_j6q9eEGNgTMTIF7_bAJ/view?usp=sharing

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on May 4th, 2018
No, those are the high voltage anti static probes you are seeing in the picture. The PMT's are found inside the lead shielding found inside of the top cover. Don
avatar: marchem
marchem
11 posts
Replied to dpkleessr's post on May 4th, 2018

Don, would swapping the left and right PMTs directly be worth trying?  I know it's a hassle to get them out, but that should identify if it's a PMT or socket problem.

Rob

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on May 4th, 2018

Forgot to discuss your statement about what to expect from Beckman. First, when I retired 5 1/2 years ago, a single PMT cost over $5,000 and a socket was over $1,000. Ridiculous pricing for parts whose real cost was a small fraction of that price but their pricing just the same. A 3rd party service group may be more cost effective but I have little knowledge of any reputable groups nor there actual reliabilty or capability. I wish that I could help more but I am really out of the loop beyond my own pre retirement experiences.

Don

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on May 4th, 2018

Rob, there is some benefit in trying that in that by knowing right now which side is showing activity and swapping the tubes around you can see if the activity LED's change with the swapping of the tubes, which is much easier than swapping the sockets around.

Don

avatar: LG1
LG1
11 posts
Replied to dpkleessr's post on May 4th, 2018

I still think we'll opt for service since it sounds like getting a PMT from 3rd party could be risky, as well as handling them and requiring recalibration, but for my knowledge how would I access the PMT if I wanted to swap? After removing the top cover is it pretty simple to open the lead shielding?

Also, is the DS2 light being on indicating that is the defective side? Or the side that's working? 

avatar: dpkleessr
dpkleessr
970 posts
Replied to marchem's post on May 4th, 2018

Rob, Obviously who you decide for on service is your choice. I do not even know who BCI has that can still work on them as most of the "old dogs" such as myself have retired. As long as you or anyone else takes reasonable precautions then handling of the PMT's is not that big of a deal. If you decide to go the route of replacing the PMT then we will go into more detail. Again, it is not inherently difficult. It just takes a little time and being careful with handling the PMT. In addition to the "light shock" previously talked about, PMT's are especially sensitive to "physical shock" such that they can be broken and you will have no knowledge of that fact until you try to use it. Generally this type of problem would be manifested after dropping a PMT or bumping it with a good amount of force so this falls into the category of just being careful with the handling of a PMT.

Don