UPS high pitch whine noise

[smilem]

Hi, I have back ups pro UPS that makes this high pitch whine noise.
I have solved similar problem in another thread with my smart ups by using lacquer but it seems I can't find the component that makes this noise.


The noise is inaudible at cold start for a few minutes.
Then It is like pulsing about every 4-5 seconds no load AC power.

If I switch the ups off I get constant whine noise until I switch it back on.
Then if connect load to it I get constant whine noise too. (if there is no load then it's pulsed like I said before.)ALso somethimes it is just lower freq hiss sound.


I have used spray can Hi temp, lacquer on 2 round coils that could produce the problem. I also put some on 2 small transformers inside. And big transformer too. it made no difference at all.


I have used spray can Hi temp, laquer on 2 round coils that could produce the problem. I also put some on 2 small transformers inside. And big tranformer too. it made no difference at all.

 

[Sceadwian]

It could be a capacitor telling you it's about to fail, or a power inductor or transformer. Easy way to find the faulty component is to find the source of the sound, mind you that's not too easy. Measuring the phase difference from a pair of stereo mics would work, but more effort than most people would care to put forth. You could do it using a two channel oscilloscope and a pair of microphones at a set distance.

 

[#1supertech]

re: your UPS unit noise

Hi -

First of all - are you saying you have an APC Pro UPS unit, and if so what VA output is it rated at (Model # that is)?

Secondly - if it is indeed an APC model, and less then 1500VA in rating then chances are you have a very cheap model esp if it's using smaller AGM batts under 17.2ah in size. The 7 & 12ah model APC units are all very cheaply designed, and rely on the batts - for the most part - to act as the FILTERS in the units. Most other smaller UPS units do as well more or less.

The more expensive UPS units use better (larger) CAP filters and Inductors to smooth out the units noise transients - mostly from the switching MOSFETS and their related circuitry.

APC is by far the worst when it comes to being chinchy on good filter caps in their low-end UPS units - hence hiss & hum and yes even WHINING! You get what you pay for! What do you expect for $12-15 after a rebate as it were.

People - esp APC UPS users - that have a keen upper freq hearing range are even more susceptible to hearing all those higher pitched whining transients - lower humming and hissing sounds as well. Users that have a slight to moderate hearing loss might not even notice (hear) that higher whining and even the lower humming and hissing noise. Severe hearing loss users could no doubt care less, as they are immune to most everything - esp if they are younger and listen to a lot of LOUD damaging BASS, as by the age of 25 they will have suffered at least a 75% hearing loss.

In most smaller APC models I've found that the MOSFET heatsinks (by their poor design) tend to aid in that buzzing sound. Then add in all the other PCB circuitry, and there you have it.

Hopefully your AGM batts are in great condition, because as they lose water and deteriorate over time they will lose their filtering qualities and thus be far less effective in filtering!

Seeings that I've owned & operated (not to mention repaired) a lot of quality UPS units in my lifetime, and I've never had a single one of my DELTEC's ever WHINE before - this may sound a little too obvious here, but have you pulled the battery pack out of the unit and actually checked the batts for proper "no load" charge voltage - as well as performing a 5 amp LOAD draw test on the batts as well - not to mention checks for cracks, bulging, or signs of acid leakage?

If both batts don't read the same or very near same voltage, and one batt is significantly higher in voltage reading then the other - then that batt is definitely going bad, or else it IS ALREADY BAD - esp if the batts are over 4-5 years old. In which case both batts should be changed out at the same time. Stay away from the cheaper CSB, PORTALAC, and the B&B brands - as they are all JUNK! YUASA and MK are 2 of the best brands out there! I can get 8-9 years out of my YUASA AGM batts if treated right - in so far as the DOD & proper Charging rates goes.

Adding a larger filter cap across the batt charging circuit would help somewhat as well, but buying a bigger and better quality made UPS unit would be my first choice, and makes more sense in the long run. For my cmptrs I use all 1500VA DELTEC brand units (as they are the best), and 1 bigger APC 2200VA unit for everything else that is shared. Esp if it's being used in a more critical application such as that for a cmptr backup UPS unit. I have several smaller units online around the house to back up the cordless phones, homemade security systems, and a couple of digital clocks so I won't have to reset them should we have a brownout or two.

Also - adding some peel and stick damping material to the inside of the UPS case walls helps dampen that whining as well, as long as heat transfer isn't impeded.

If you can even find a couple of those older DELTEC 1500VA UPS units - buy them!! They are rock solid, and the PCB design features are the best as well. They are 24-volt by design, and use (2) 17.2ah AGM batts. The 100 amp fuse scheme using (4) 25 amp glass barrel fuses is a bit weird, but you can always change it over to using (2) 50 amp or (1) 100 amp automotive type flat blade fuses.

I have found some great deals on the older APC 1400VA units at my local cmptr swapmeets from time to time, and once scored big time getting (3) of them plus 2 of the older & smaller APC 500 & 700VA units all for $45! All of them worked 100%, but all the batts were shot in them. I figured that much! All the cases were very clean, and had no real external damage except for maybe a few minor scratches. I kept the best looking 1400 unit plus the single 7ah batt 500 unit as well, and sold the other 3 to a friend of mine. Oh well - can't have everything!

Those older APC units were made a lot better then the newer ones of today. Everything from China today is so cheaply made that it isn't funny anymore.

Check out your local cmptr swapmeets if you have any near you as sometimes you can really score big at them!

Hope the info helped?

Enjoy!

Frank

 

[bountyhunter]

Usually the things that whine are inductors or transformers because the wire can vibrate on the core.

 

[smilem]

I found the part that is causing the whine noise.

I did it by using low power speaker shielded magnet. I used it plastic bag. And by holding it near every coild and small transformer (there are two of them) I discovered that if I hold it by one of them the noise becomes louder.

So I found the part that makes the noise.

I de soldered it and placed in laquer for a few coats. But that did not help, It still makes the same noise.

The part is listed as 430-0269 05523 FALCO.
My usps model is: BACK UPS PRO RS 500VA
Also knows as: BR500I

The battery is new and should not be considered as a problem source.

 

[bountyhunter]

Looks like a transfomer to me. usually it's either the windings or the core vibration. It can often be fixed by dipping the whole thing in varnish or epoxy.

 

[Sceadwian]

Even then you may not be able to do anything about it, if the natural conformal coating towards the center of the coil has developed a gap coating the outside won't do a thing. You'd have to completely rewind or replace the coil.

 

[smilem]

Even then you may not be able to do anything about it, if the natural conformal coating towards the center of the coil has developed a gap coating the outside won't do a thing. You'd have to completely rewind or replace the coil.

I do want to replate the thing. Can anyone give me any idea what part do I need? I can order from farnell or other site.

 

[Sceadwian]

Not a clue.. sorry.

 

[bountyhunter]

If you don't have the mfgr part number from the transformer it's just about impossible to guess it's specs. A switcher transformer has a lot of critical specs (I have designed quite a few) like turns ratio, primary inductance, leakage inductance, core flux density, etc and you have to know the input/output voltage and current to design it as well as the operating frequency.

 

[bountyhunter]

I do want to replate the thing. Can anyone give me any idea what part do I need? I can order from farnell or other site.

It you are down to last option, you might try this:

Get some clear urethane spray coating (hardware store has it). Warm the transformer in the oven to maybe 150F (as hot as possible and still be able to hold it in your hands). Then hose the heck out of it with the urethane trying to get it to flow into the windings and core. Wipe the excess off the outside and let it dry. Might fix the noise.

 

[#1supertech]

smilem,

I kinda figured it was an APC model UPS, and a smaller single 7ah batt model as well. A somewhat newer and cheaper model as I now see online for about $100 retail. These so-so $15 units (after rebate) are after all - what you get for what you pay for them. Nothing for nothing as it were. They're all made in China today - more or less, and that's the biggest part of the problem right there!

Like I said in my prior reply - just find an older quality made model (bigger the better) that was built much better then the UPS models of today, and I'll bet your WHINING problem will go away! Your WHINING as well as the UPS unit's WHINING as well. All sarcasm aside….

Not trying to sound sarcastic here, but why the hell are you wasting so much time and energy over a little high freq whining - esp if the circuit is designed to switch faster to begin with?

In other words - faster switching - higher freq - higher whining!! Stop trying to automatically blame it on XFMR's & Inductors! You might just be chasing a GHOST you will NEVER catch. You may think you have bagged a bad part (XFMR in this case), but I'd be willing to bet that even an R&R'd exact part doesn't solve the "switching" noise problem! Remember - first and foremost - these are CHEAP UPS units to start with!

Reason I say this above is because I once had the same similar problem with an Automotive type 4-statge switching batt charger that was made by Schumacher. The first one I bought through Walmart for $42+tax and was a great model doing everything I ever wanted a batt charger to do and more. It was a fully automatic model SC-1200A, and it too was CPU "firmware chip" controlled, and made really well as far as by design and as far as the Mobo components inside went. The only thing I changed out on it after 2 years use was the cheapy 12-volt mini cooling fan (sleeve bushing btw) inside that started making noise as it howled and then squealed like a pig one day, and then finally froze up on me all together later that same day.

Spent quite a bit of time just getting the darn thing apart and back together again after the fan R&R - as the new super quiet $1 ball bearing fan I bought at the cmptr swapmeet only took 5 mins to replace.

While inside the charger I noticed how well my charger Mobo was designed and also how quiet it ran as a result. What happened next after another 3 more years of use I'm sure you'll enjoy immensely.

It ran just great for something like 5 years total charging all my AGM batts that I use day in and day out in all my apps!

Then one morning it started acting up a bit having had a few hiccups, after which it ran great again for a few more days and then one morning just died on me altogether. All flashing LED's is all it would do! Internal failure of the Firmware CPU chip no doubt.

I sent it in to Schumacher with the understanding and hoping that they could & would just swap out the bad Firmware chip if that was the case, and get the same unit back to me. Then after some 2 weeks time of not hearing back anything I was given the bad news when I called up my contact there to find out what was going on.

Guess what? They couldn't find my charger - or so they said.

Supposedly there was some Tech Dept miscommunications as to the part about me getting my original charger back (if it couldn't be fixed) - as I wanted to use that better quality AL framed case body for another multi unit float charger prototype project I was working on.

To say I was doubly bummed out at that point was an understatement! I was then told in a roundabout manner - by my inside contact there - that it couldn't be fixed and that is why it was supposedly scraped. I was bummed out to say the least! My gut feeling is that someone there repaired it successfully, and then kept it for themselves knowing of its quality Mobo inside!! I'm usually quite right on these assumptions as I have a sixth sense inside me that is so unreal at times that it even scares me at times!

To compensate me on my loss he sent me out a brand new unit (supposedly the same model) totally free, but when I got it and plugged it in - guess what?

The noise the new unit made drove me absolutely crazy - AND - my high pitch hearing in one ear isn't that great to start with, so see what I mean about people having sensitive ears or sensitive hearing problems!? There you have it.

The long and short of this charger story is that not only was the charger case now all cheapy plastic in design, but the new charger's Mobo was totally redesigned as well, and thus in turn that was what was causing all that new higher freq switching noise inside (actually the Mobo was cheapened by reducing the good filtering components is what happened).

I opened it up just to compare the 2 units (old "quality unit" vs new "cheapy unit"), and I was blown away when I saw the cheaper Mobo design! Total junk in my own mind if you ask me! Not to mention the cheapy plastic case as well - to no doubt save on the foreign Made in China production cost, and yet still try to keep profit levels high. Walmart was beating them up as well with profit levels for sure - as that is just Walmart's way of doing business period. Oh well….

To compensate for the reduction in quality filtering components on the Mobo the switching curve had to be raised (increased freq that is), and as a result - more noise as well.

I told him that I couldn't live with that horrendous buzzing/whining noise that it made, so in turn he tried to re-tweak the Firmware chip settings by sending me out 2 more exact model #'s, but to no avail. So then I had 3 more charger units that did me no good. They didn't want them back either so I just sold them at $30 a pop and pocketed the money.

Because they lost my original charger I sent in for repair and never got back, and the fact I was still out a charger to charge all my AGM batts he had to do something to make it right.

So what I got sent out FREE next was a brand new Heavy Duty Schumacher "made for Sears" batt charger - Model # Diehard 71225 - that is also a Microprocessor controlled switching type 4-stage linear taper charger selling for approx $80. After testing and using this charger extensively with small (7ah) to large (100ah) size AGM batts I like it even better then my SC-1200A charger. The Sears Diehard model 71225 is now "my personal best choice" overall, and I will now be using it as my #1 choice in all my day to day batt charging applications!! The 71225 also has a de-sulfation mode if your battery is indeed sulfated to start with. Again - Nice feature! Heavy duty as well. When I say it's a Heavy Duty charger - I mean just that. It’s Heavy Duty and great quality inside and out! Not only does the huge XFMR inside bring the unit’s weight to a nice hefty 12.5 lbs, but the Electronics inside are very well engineered as well.

With that huge XFMR inside comes a tradeoff in the word QUIET though - as we all know that bigger XMFR's make more buzzing noise the bigger they are. Nature of the beast! That's a given. The +5 volt XFMR cooling fan inside is a tad noisy as well, but because it's not really needed unless using the 30A charge setting I added an external ON/OFF cutoff switch to quiet the charger down a bit. It helps!

Anyway - I think you can now see why some things - even though they are very well designed and made from good materials - still will make a bit of noise - be it buzzing - whining or whatever.

One footnote here - Under heavy pressure I finally did get back an empty shelled (gutted) identical charger case (the good quality AL plate kind like that of what I sent in originally), so sometimes it pays to be PERSISTENT!!

BTW - That failed charger Firmware chip (mentioned earlier) - as with some UPS units as well - are A VERY COMMON PROBLEM with APC units as well - so I found out many a time - having to change them out when I could buy the Proprietary Firmware chip replacements directly from APC on the East Coast in RI for something on the average of $12 each give or take a few bucks. Was nice while it lasted!

Some 10 years ago or so APC Corp stopped doing that nice Tech Service Dept favor to us SuperTechs, and you were then left to deal with some rinky-dink outfit on the West Coast up in Wash state that would only swap you Mobo's at some ridiculous price!

That is when I stopped working on APC2200 models for the most part, and anything APC smaller as well. It was cheaper to just pitch the failed APC unit after stripping out the hopefully good batts and a few other components, and then just finding another good used replacement UPS unit of equal VA rating & value - APC brand or otherwise! Much like I stated in my prior reply - I went to cmptr swapmeets to find them cheaper by the dozen I might add.

As I'm saying here again, and what I stated before - it's just not worth the time and trouble trying to silence a little XFMR or Inductor humming / whining / buzzing when you can just put a shroud box over that smaller UPS unit and then the noise problem is solved for good! Or at least we would hope so!

I didn't want to suggest or mention that before as then we get into that issue of aesthetics, and we all know how crazy we get when something looks ugly, but yet solves the problem.

I really think that your EARS are a bit high freq over sensitive, but then again that could be from the fact that you too have a low pitch loss of hearing from possibly listening to too much LOUD BASS and thus in turn your high pitch hearing is now affected as well.

Studies have shown that kids lose up to 75% of their hearing range by the time they reach the age of 25 due in part to listening to too much LOUD BASS sounds at a younger age. This is a FACT btw!

Hope you're not one of them?

Anyway - good luck trying to find that XFMR, and if you should I really doubt it will solve your high freq whining problem there.

Do honestly let us know if it should though?

I love eating CROW! Hahahaha….

Best regards,

Frank

 

[smilem]

Here are the phtoso fo UPS PCB:


PCB top

**broken link removed**

Troublemaker (can anyone identify it)

**broken link removed**

Back PCB (so you identify in/out pairs)

**broken link removed**

 

[#1supertech]

Smilem,

After finally seeing your posted pix of that el cheapo $15 BR500i BACK UPS PRO RS 500VA unit - I only have a few parting thoughts in ending my thread posts here to your more then OBVIOUS UPS unit whining there.

It was bad enough the pix you posted took forever to upload, but after seeing them I can clearly see why the typical high freq PCB whining. That Ipix.com pix upload problem might have been because some other guy named Alek posted some HUGE Cellphone shot pix as well - only at a different thread, and those wouldn't even open up at all. Yours finally did, but it did take awhile!

Reread both my posts from OCT 17th & 20th just in case they didn't sink in yet. I added an edit update to the original 20th post as well.

Even though I never asked what you were using the UPS on - apps wise - it is of little concern to me here, and for good reason. Bottom line is - it's an el cheapo UPS unit - you get what you pay for! In other words - JUNK!! APC junk at that! They are after all the bottom of the barrel in the UPS industry, and for good reason. Just look at what you have there and is it any wonder?

If you are using it to back up your cmptr system then I feel sorry for you. Hopefully you value your cmptr system - IF you are indeed using it as a cmptr backup power source. If your cmptr system's PS can tolerate the POOR QUALITY power supplied by el cheapo UPS units such as the one you are using there - then more power to it. I would NEVER use a piece of under-designed crap such as this unit you have there. That's just me - but I value my cmptr system, and what's on my hard drives - as for work files and more!!

I don't even see a FILTER CAP on your pictured PCB there - a CAP even close to being called a FILTER CAP! In other words - THERE ARE NONE!!!!!!

Not only that - the MOSFET switching circuitry is of little worth as well. Those heat sinks don't even appear to be double board mounted either - as in they only appear to have 2 mounting pins through the PCB. If that is the case then they too are a noise (buzz) factor! In other words EL CHEAPO as well. Re-read what I posted earlier if you didn't understand that part. That Mobo you have there couldn't be anymore down and dirty cheap! Talk about high freq whine - it is any wonder!?? One pix says it all. Case closed as it were!

If I were to take my O-scope and look at the ripple across the BATT - while the UPS unit is in backup mode (no Edison AC line power that is), and then further look at the switched AC output as well - I'm pretty sure all I'm gonna see is something very close to a pure SQUARE WAVE at best, and nothing more! All excessive ripple aside that is. Who even knows how SQUARE it is either - as if it's even distorted in the least - then you have a bad (leaky) MOSFET problem there as well.

I doubt the output is anywhere near that of a better quality stepped "Quasi-waveform" AC output. How much you wanna bet? Of course I already know the answer to that so we can just move on from there - not trying to take your money as it were.

The real problems I see PCB right now - from a POOR soldering perspective - is that IC2? (can't see the actual p/n next to C41 - as it's being blocked in the pix) appears to have some POOR (cold) solder connections, as well as that R&R'd FALCO brand XFMR. You're obviously not using a good quality soldering acid flux like that of #30 by Superior Flux Mfg Co., as well as using 60/40 solder.

I also see some bad COLD solder connections under what appears to be a Toroidal Inductor coil next to IC4 just for reference. There is some board heat distortion present there as well - as noted by the PCB color (heat) distortion. It's either from natural under-designed usage, or else you are driving this UPS constantly into a backup batt mode? Anyone's guess here.

I never did ask if you were using the original 7ah 24-volt batt configuration, or if you (like so many others out there do) added bigger external capacity batts, and then thus in turn drove this underrated unit to death?

Like I've said before in posts - the only thing I'd ever use these smaller single 12-volt 7ah batt 150 to 500VA UPS units for is for a digital clock, or cordless phone back-up as for the switched square-wave AC power source. My home made house alarm system I have would be the other thing, as long as I don't have to count on a power outage any longer then say 2-3 hours tops! That is all I'd ever use my smaller $15 cmptr swapmeet bought UPS units for around the house anyway. They have NO Cold Start-up feature so that kinda settles that issue right there! That is all they are good for in my mind.

For anything else bigger like a cmptr system it has to be at least a 24-volt 1500VA better quality stepped "Quasi-waveform" AC output UPS unit like I mentioned prior. A true AC Sine-wave output UPS unit is even better, but then too so is the cost a lot higher as well.

It's true that they use (2) bigger 17.2ah AGM batts, but they also last a lot longer as well. My DELTEC's batts (MK or YUASA brand batts) have lasted me 6 years on average. They are usually still usable even after 6 years, but just not in the UPS units anymore, as they no longer will hold a 100% charge capacity at that point, and the DELTEC's circuitry senses that on the automatic self-test it performs every 30 days. The 48-volt APC2200 & 3000 models do the same thing every 30 days as well. I have 1 each and they both work great - knock on wood should one ever break! If they should then they are just scrap metal, as there is no way I'm spending $300-400 on a refurbbed Mobo!

Hope this tells you something about those smaller el cheapo UPS units like you have there. When the batt(s) do go bad on them they are usually 100% sulfated by that time, as those cheapy UPS units have no way to tell otherwise, unless that is you do a manual Power Fail test every 3-4 months on average to exercise the batt(s) in them. Price you pay for small cheapy UPS units.

Good luck on your $15 el cheapo noisy APC UPS unit there, and what you think is a noisy XFMR as well - that is - if you even wish to waste more time and money on a useless R&R of the same! As I stated before - it's not worth the waste of time and money at this point, but you're on your own there as to that part. I also really think your ears are just way too sensitive on the high-end range of hearing, and that is part of the problem as well.

Best regards,

Frank

 

[smilem]

Well this ups was not so cheap I got it back in 2005 for ~100$. Then I was in luck to trade the sucker to my friend who had a smart ups 420VA that was not enought to hold his computer so when he so that I got 500VA ups with warranty and everthing he sugested me if I would want to swap them I sure did.

Now my friend got dual core machine and obviously this UPS can't drive that. I just got my old ups back from him for no cost, so just wanted to know if it's possible to identify the cheap transformer so I could try to get another one (they are cheap right) to test if the noise will be there or not.

For my computer I use Smart UPS 1000VA that serves me well for over 10 years, no problems just replace the batteries. My other equipement is on the Smart UPS 420VA.

Mind you that the prices you pay for ups in USA are smaller compared to that in EU. So el'cheapo UPS for you might not be cheap here, crap yes, but cheap no.

 

[#1supertech]

Smilem,

I see I'm either in the wrong line of business, or else I missed my calling yet one more time in life!

I should be selling quality UPS units to people in EU for sure.

I had no idea that you too were in EU, but I'm seeing that a lot of the posts here are from over there.

And YES I do realize that electronic stuff costs up the kazoo over there, as does it too in Australia as well. I've talked to several people from there about PV related stuff, and it's very expensive over there as well! Of course living on an Island always is!!

I guess that is why we have FRYS Electronics stores here in CA, as well as other major electronics outlet stores as well, but I would have thought that being closer to China - like you are there - that you would be able to get stuff like that much cheaper then having it shipped all the way over here in the USA?? Guess not!

Try looking at their online site as maybe they would ship from CA to where you are if the price is right? Never know…

Fry's Home Electronics | Computer Parts & Accessories, Software, Games, TVs, Cameras - Frys.com

At least you have a Smart UPS 1000VA for your valued cmptr system, but that 420VA can't really be used for anything serious cmptr wise. Again - it's just low-end junk! I had several of them years ago that I got FREE after a rebate and just wound up selling them for like $25 each as no one here will pay more then that for one.

Once the economy picks back up there will be a ton of backlogged and/or surplus warehouse cheaper UPS units that will be dumped on the market because the batts inside will be of little use - esp as a store shelf sale item! Once those UPS units sit around the docks, or in warehouses for 6 to 9 months the cheaper CSB and B&B brand batts - that they always use inside - tend to start to sulfate, and that is why they rebate them out for FREE like they do. Just so you know.

Great rebate deals for FREE, but then the batts don't last but a few months and die! No recourse either because it was a FREEBIE on a rebate! See the downside? Oh well……

Regarding that XFMR you're still obsessed with changing out -

Because those APC's are so proprietary in nature unless you actually find an identical unit that is toast, and you can scrape parts off of it you aren't going to find that XFMR anywhere for a stand alone sale item. PERIOD - dead issue! I thought I all but explained that part in not so many words several times now.

Btw - you made an error in stating the p/n earlier on that FALCO XFMR.

It's not 430-0269 05523

but rather 430-0269 0523

I just happened to catch that part right now in looking at the closer up (magnified) pix version that you posted. Didn't realize those pix were SO HUGE in file size! You must have shot them in TIFF mode - no wonder they were 1.5 to 2.4 Meg in file size, and took SO LONG to upload!

I just opened up one of my older 500VA BACK UPS (the older better quality made models btw) to see if by any chance it was running that same PCB mounted XFMR that you are still looking for to change out, but just as I suspected my 500VA UPS units are running a HUGE inductive LOADS XFMR that is maybe 1/3 bigger then yours there, and a large PCB mounted power supply side XFMR that is almost as large as your 4 MOSFET heatsinks that are next to that FALCO XFMR. See what I mean about the older quality made stuff?

One other thing I might add here as well - regarding the older quality made UPS units - as they related to that HUGE LOADS XFMR I noted above. They were definitely made a hell of lot better in days gone by! By that I mean they were the kind that were bolted together core plate wise, and not just press slip fitted, and then shellacked like yours there in that BR500i. Again - see what I mean about quality made?

A couple of other nice features these older APC 500/650VA UPS units had was the re-settable circuit breakers on the back. That and the 4 trim pots on the PCB to adjust (calibrate) the UPS unit for FREQ OUT - BATT FLOAT POINT - VOLTAGE OUT - XFER VOLTAGE. I noticed on your cheaper model there that everything is FIXED, and nothing can be adjusted if say a CAP drifts out of specs and you get a shift in FREQ. Bummer!

One thing that is coming up next month in NOV is another big cmptr swapmeet near where I live in SOCAL near Disneyland, and I'm definitely going again, as I need a few cmptr parts plus some odds and ends. If you want I can poke around and look for a cheap deal on a BR500i - IF I can even find one. Even if the UPS unit looks like crap or the batts are shot I'm sure that the XFMR won't be burned up or open, as that rarely happens if at all. I'll keep my eye open for a used BR500i anyway just to see what's out there in USA land.

Just a shot in the dark here, but what do you have your OPTION SWITCHES set to? 1 thru 4 that is? I'm wondering if your friend - that had it before you got it back - if he tweaked the OPTION settings? Just a hunch?

Frank