Furman conditioners wrong voltage display problems (solved)

[ACalbass]

I recently started playing again after many years.
I am acquiring gear and one of those things was a used FURMAN PL-PLUSDM power conditioner,from GC.
The device works well,and it has a digital display for voltage and/or amperage.
The point is that after couple hours of being plugged,the voltage reading starts to fluctuate and drops into the 80's 70's (normal should be around 120).
Is not true that the voltage is dropping,the truth is the reading gets completely screwed up,gives a false reading.
I tried to search for reports of this problems in the net,found some several people have/had this problem with not only digital displays,but also with LED based meters.
I have some background in electronics so a decided to take a look at the cause of this problem,I attributed the problem initially to a component that was going out of specs under stress,like a bad cap or a resistor.
It wasn't the case at all.
I found out that the meter board had couple of problems together,that need to be addressed individually.
The first component that is causing the bad readings is a TRIM POT of 5 Kohms that is located in the middle of the board in my unit,it wasn't able to keep a set value,instead it was variable to the simple touch.
So,what I did is to lift it from the board and was going to replace it,but first a decided to clean it well and see if it was only that needed.
Put it back in,then found some other cold solders (second problem) in the board,and solder them well again.
Placed the board back up into the enclosure,and is running without problems for half a day,the display is constant 120 volts,fluctuates only one digit up or down but that is normal.
I assume not everyone has the knowledge to do such work,but I post this in case people has similar problems and change the unit thinking is not doing what it suppose to do that is protect your gear,which it does,in my case.

The problem of this bad readings is that the unit is registering the reported values of the meter,and can act upon them,like when it reads over a certain limit,it can shut down the unit for overvoltage that is not happening.
Same goes for under voltage,it might shut down.
Of course ,if your unit is on warranty,you should never attempt to fix it.
But for those that have this problem and is not on warranty,I would say it is very simple to fix,shouldn't cost much if taken to a repair shop.
I wonder how many in TB have/had this problem and what did you guys do.

(MODSlease move to the appropriate section if this is not the correct one.)

[BassmanPaul]

If your problem has been solved post what the resolution was. That way we all learn a little something new.

[gregbackstrom]

Originally Posted by BassmanPaul

If your problem has been solved post what the resolution was. That way we all learn a little something new.

I think he did.

[WingKL]

Cold solder joints are a bitch. I think a lot of it happened when manufacturers switched to lead free solder and did not have the correct process/solder figured out. A lot of the lead free solders did not flow very well compared to bad old leaded stuff.

[ACalbass]

Originally Posted by BassmanPaul

If your problem has been solved post what the resolution was. That way we all learn a little something new.

I think this belongs to the thread "things your bandmates said" in the jokes section,right?

Juts messing with you.
I did what I wrote in the first post and the device is working fine now.
In any case,the trimpot should be changed for a new one,to avoid future problems.

[BassmanPaul]

Sorry - Just got out of bed and the ol' brain ain't awake fully!

[walterw]

nice!

it just shows again that many problems with electronics are actually mechanical, like the aforementioned dirty contact in the trim pot and cracked solder joints.

[BassmanPaul]

What I find interesting is the 120V reading. in my area it's usually closer to 126V. As I am now retired from the generating company there's nothing much I can do about it!!!!

[Pilgrim]

Originally Posted by ACalbass

In any case,the trimpot should be changed for a new one,to avoid future problems.

I am unable to come up with any reason to buy a new piece of equipment that requires me to open it up, partly dismantle it (voiding any warranty) and replace a part. I can do it, but it's pointless and a waste of money.

My advice: avoid this device if it doesn't work.

[will33]

Originally Posted by BassmanPaul

What I find interesting is the 120V reading. in my area it's usually closer to 126V. As I am now retired from the generating company there's nothing much I can do about it!!!!

My place runs around 117-118. Other places I've worked on maybe 123 or so. Who knows what's up?

[ACalbass]

Originally Posted by Pilgrim

I am unable to come up with any reason to buy a new piece of equipment that requires me to open it up, partly dismantle it (voiding any warranty) and replace a part. I can do it, but it's pointless and a waste of money.

My advice: avoid this device if it doesn't work.

Please read the first post,is not a new unit,is used.
I assume you would do it if you consider it worth it,as I did.
Also,there is no money lost as it didn;t cost me anything,and if at all, a new trimpot cost couple dollars.

It does raise a point,though : many people having the exact same problem,with units our of warranty ,finding no help in the internet about it,and now with a viable way to fix it on their own,or with a help of some friend that knows about soldering electronics.

I believe the worthiness of my experience is that I shared my findings for others to take advantage of,the very reason you signed up in this forum.
I was reading this forum for a long while without registering,this is a way to somehow repay important information I gathered from here,at many levels.
Is my way to say thank you.

(there must be something there that people is not reading this thread well and missing the message? LOL)

[Pilgrim]

I agree - it's worth noting and reporting! No disagreement there. And I appreciate your doing so. Not everyone is willing to go to the trouble.

And as for reading your original post, it's rather difficult. All the lines run together, and I had trouble visually separating the points. When that happens I (and many others) simply refuse to read the post closely. It's too much work.

Nothing personal - your post had good info. But I didn't get the info until I went back and extracted it, line by line.

I hope you do well here and enjoy the forum!

[Sneakypete]

Internal trimpots that are adjusted at the factory and never moved afterwards are a common source of intermittent symptoms in domestic and industrial electronics. It's usually just a little oxidization of the contact between the wiper and the track. At the factory somebody probably set the pot while looking at a meter or scope but usually it's close enough to just mark the wiper position on the circuit board with a fine-tip pen and make sure it goes back to that point. I'd be interested to know what voltage you have at either end of the pot with respect to the ground of the DC supply. IME higher voltages mean more oxidization. I work a lot with 5V logic circuits and the trimpots there almost never give a problem. Well done for persevering with it!