APC UPS SU3000NET multi clicking noise

[Anonymous user]

Hi pals,

My APC UPS su3000net is giving multiple clicking (all) relay noise with all the leds flashing according to the clicking noise of the relays. Any info on what could be the cause and how to remedy it. Pls help out and thnx.

[Brad_C]

I'll answer here rather in the other thread. No. The Leds are driven from a shift register in the panel. The Relays are driven from dedicated outputs on the uC via transistor buffers. It sounds like the uC is going birko and flashing its output pins. An 8051 will do that when configured for external memory. Perhaps the uC has lost its mind. That one I can't help with. Is the fan turning on and off as well? I ask because on the SU series the fan control is on the same 8 bit port as the panel serial link.

Check pin 31 on the uC. It should be high (~5V). That's the external memory enable. Also check pin 9 to make sure it's not toggling (reset pin).

Grab a data sheet for a DIP40 80C52 uController and have a poke around.

Do a google search for E735Gschem.pdf. It's a different model, but it's an SU series and the schematic might help you out with your SU2200 repairs also.

[Anonymous user]

On , said:

I'll answer here rather in the other thread. No. The Leds are driven from a shift register in the panel. The Relays are driven from dedicated outputs on the uC via transistor buffers. It sounds like the uC is going birko and flashing its output pins. An 8051 will do that when configured for external memory. Perhaps the uC has lost its mind. That one I can't help with. Is the fan turning on and off as well? I ask because on the SU series the fan control is on the same 8 bit port as the panel serial link.

Check pin 31 on the uC. It should be high (~5V). That's the external memory enable. Also check pin 9 to make sure it's not toggling (reset pin).

Grab a data sheet for a DIP40 80C52 uController and have a poke around.

Do a google search for E735Gschem.pdf. It's a different model, but it's an SU series and the schematic might help you out with your SU2200 repairs also.

Yea the fan is running.

Please watch the attached video for a clearer info on the problem of the ups.

Thanks for the initial response.

[Anonymous user]

Good day, I've did a check on the system and here are my findings;

1. Pin 31 is giving 2.8v against the 5v,

2. Pins 9 & 7 being the reset pins are giving respective 1.8 and 1.9v and

3. The fan is receiving normal 24v even as the system is misbehaving.

Those are my findings, pls what do you think I should do next to get this system working.

Thanks once again.

[Brad_C · Accepted solution]

On the uC, pin 9 is the reset pin. Pin 7 is bit 2 of the 8 bit bus that generates the reference sine-wave on the DAC.

If pin 31 is 2.8V then I assume pin 40 is 2.8v (which is the primary +5V supply for the uC). Sounds like you have a power supply issue.

For giggles, check pin 12, 19 or 20 on U10 (which is the ADC0838 A/D converter), if you have less than 5V there then you have an obvious issue with the 5V logic supply. It could be the 5V reg, but more likely something is shorted (or very low impedance) on the 5V rail and pulling it down.

Make sure you are using an appropriate ground reference to make these measurements. The Tab on IC5 (the 5V Reg) is a good place to pick up a logic ground if you haven't got one already as are pins 4 & 9 on the D9 connector on the back panel.