Greetings,
To contribute back to the community I'm publishing results of a successful repair of this 7 year old UPS (CyberPower CP1500AVRLCD).
Background: This UPS unit was used for the last 7 years to support the network stack in my home lab, i.e. small load <100W, fairly long runtime possible (but very rarely happens in reality). The unit is on its second set of batteries.
Symptoms: 6:30am on Sunday morning (Murphy's Law in action!) I got an audio jolt from it - continuous beep, LCD screen shows E21 fault, load dropped. Power it down (power button hold for few seconds), power up again - works like nothing happened. about an hour later - same scream, E21, load dropped. BTW, judging by other UPSes in use here - there were no power surges at that time. This unit was taken out of service and checked. Batteries are on their 3rd year, but both hold load (about 3A) without issues. Case opened and the problem became obvious: several visibly blown/charred MOSFETs, after desoldering - 4 out of total 8 are done. So are the 3 of their gate resistors (22R 0603). The E21 error, in various CyberPower docs, is indicated as "battery output short" - but there were no shorts anywhere other than the obvious MOSFETs themselves. High current fuses are not blown. PCB material is not charred, traces are not blown, but some of MOSFETs had their leads auto-desoldered during the incident :-). Oh well, less solder to suck off during desoldering :-).
Resolution:
1. Check what else is dead: BJTs and optocouplers driving MOSFETs, as indicated in the photo (see red Sharpie writing on PCB) - no issues; battery charging PSU (VIPer22A based) - functional, DC-DC converter (voltage-inverting, MC34063 based) - functional;
2. Check if relays (4 pcs) are stuck by any chance - temporarily desoldered one side of the coil on each, gave them 24VDC repeatedly, observed SPDT contacts resistance changing repeatedly - no issues; don't forget to resolder the coil!
3. Check the main transformer for shorts - all wires in air, high side to 120VAC (via dim bulb first), no issues, idle power consumption is few watts, no heat up, no galvanic connection between high/low windings;
4. Order parts:
- MOSFETs: original are SinoPower SM6002N, closest (slightly better) reasonably priced Western analog is STMicro's STP130N6F7 (both datasheets are attached), ordered 10pcs to replace all 8, about $1.60CAD a piece
- as capacitors are all Su'scon and they are 7 years old - replaced all of them with Rubycon/Chemicon/Panasonic, 10,000 or 12,000 hours life, below are my choices, but availability will obviously change over time;
- as MOVs are also 7 year old - ordered them as well, if you are following my steps - check what voltage ratings MOVs are in your unit, order the same voltage, 20mm size 10kA capability MOVs - in my unit two were 20mm and two - 14mm, even though space is available for 20mm for all 4 pieces; go with Littelfuse or TDK or other known brand, do not rely on AliExpress for fire-prone parts...
5. Install everything, test run - all good. Added a tiny heatsink to VIPer22A PSU chip - makes is a bit easier for it when batteries need a full charge...
Final warnings: DO NOT DO this repair if not experienced with work on the mains-level circuits (!)... functional inverter produces the same 120VAC even when the unit is unplugged from the wall! At least do not work on it ALONE; when opening the case - be aware that it's a clamshell design and NOTHING holds down the transformer - the moment clamshell opens - it will want to go to the center of the Earth... if your foot or other parts are on that path... you've been warned!
I hope this little write-up will help someone. All the best!
PARTS:
DigiKey Part # Manufacturer Part Number Description Customer Reference Quantity
497-15889-5-ND STP130N6F7 MOSFET N-CH 60V 80A TO220AB 10 <-- replacement MOSFETs
565-EKXJ251ELL470MJ25S-ND EKXJ251ELL470MJ25S CAP ALUM 47UF 20% 250V RADIAL TH 2 <-- originals are 33uF
1189-50YXM22MEFRT15X11CT-ND 50YXM22MEFRT15X11 CAP ALUM 22UF 20% 50V RADIAL TH 10
1189-50YXM47MEFR6.3X11-ND 50YXM47MEFR6.3X11 CAP ALUM 47UF 20% 50V RADIAL TH 1
1189-25YXM100MEFR6.3X11-ND 25YXM100MEFR6.3X11 CAP ALUM 100UF 20% 25V RADIAL TH 1
1189-1759-ND 50ZLH220MEFC10X16 CAP ALUM 220UF 20% 50V RADIAL TH 1
1189-1890-ND 35ZLH470MEFC10X16 CAP ALUM 470UF 20% 35V RADIAL TH 1
565-ELE-500ELL4R7ME11D-ND ELE-500ELL4R7ME11D CAP ALUM 4.7UF 20% 50V RADIAL TH 1
565-ELE-101ELL4R7ME11D-ND ELE-101ELL4R7ME11D CAP ALUM 4.7UF 20% 100V RADIAL 1 <-- original is 63V
13-RT0805FRE0722RLCT-ND RT0805FRE0722RL RES SMD 22 OHM 1% 1/8W 0805 10 <-- gate resistors, one size up - easier to handle, still land fine
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