NEO AES 3-5 power issue (pics added)

I've got a NEO AES 3-5 board power issue. It's issue is that it does not power on. No internal LED, nothing, and Yes, I am using a known working, compatible power supply.

Chips seem to be getting power. 0.8v of power to be exact. I realize they should be getting 5v, and they are not. Therefore, that is likely the *problem*.

I swapped out the A1442 with another used A1442 (no new ones kicking around). Testing it seems to indicate the same 0.8v power output.

Does that mean the failure is likely before the A1442? What should I test next? Nothing is obviously burned, or anything like that.

I'm perfectly willing to get some new replacements for the A1442, but before I go buy a batch, I'd like to gauge the likelihood of it being the culprit.

Another *odd* thing. There is a spot for a LM2576 voltage regulator, but there is not one there. It does not really look like one was ever there either. On this version, is that normal? At first I thought the part was missing (this board was tampered with before I got it), but I'm not so sure.

If more info is needed to give me a useful tip on what to test, fire away. I'd like to get this Neo working again. If not, I'd like to learn something at least.

The 3-5 revision has mounting locations for both pro-pow and pro-pow 3 components. If the LM2476 is not there it means the board is set for a pro-pow DC input. Are you using a 5v PSU? Is the whole pro-pow componentry present? A pic of the area would help.

Pics

general board-



closeup-

As MKL said, a 5V board.

Have you tried a 5V adapter? If you have, check the diode.

Jeff

Yup. I tested it with a 5v ac adapter.

On to the diode.

0.586V on both diodes next to the reset switch.

0.791V on the diode on the far left between the B and C markings (RD5 .6A)

That's acceptable is it not (the 0.586v)? I understand that 600mV is normal, and that is damned close.

I haven't compared these ratings to a similar board yet.

The 470uF electrolytic capacitor near the hole shouldn't be there as it's part of the pro-pow 3 circuitry.

What does that extra cap mean??

Are those diode test results normal?

bumpage

Any opinions on my diode test results? Other ideas? What is the significance of 470uF cap MKL mentioned?

Apparently this board did work at one time.

arent 3-5 boards pro-pow3?
ive got a 3-5 board neo, i use a generic internation multi voltage and polarity and plug selector.

are you using the right PSU?

if ur board needs a pro-pow3 psu try a generic psu with

100v-240v AC
9v DC
negative tip.

is the pro-pow different from this by just the amount of voltage it can take? eg 5v instead of 9v for the pro-pow?

That's what I thought lachlan.

For the record, I've tested it with both Pro pow and pro pow 3 (verified working AC's), with the same results.

This board gives me mixed signals too. I thought only the early AES boards were pro pow.

whats the serial number?
its weird how a 3-5 board doesnt have the LM2476 there...
and its weird how a 3-5 board has the pro-pow socket.
im no expert of electronics but what you happen if you took the pro-pow socket out and put in the LM2476 pro-pow3 socket where it should be and then test it.
is that a bad idea?
correct me if im wrong.

The chips are getting power (0.8v) so don't think it's a connector issue.

It's been quite some time since I've last seen a 5v system but I only remember one zener diode which should correspond to the RD5.6A of your system. If I'm not mistaken that should be 5.6v which is a typical zener value so that's probably your problem.

So, the RD5.6A diode should test at 5.6V, and thats with diode test on the meter, with power off? I was under the assumption diode testing is done with power off correct?

Sorry about the basic questions.

You should test the diode out of circuit so you should probably desolder one end (with power disconnected)...

If your multimeter has a diode setting, switch to that, if not, just use your standard Ohm testing (around 2k). Test both ways (multimeter leads on both ends of the diode) to determine if the diode is open or closed. One way should give you an open circuit and the other will give you a resistance rating. If it measures open or closed both ways, it's shot. A diode it a one-way device.

Jeff

omnedon said:

So, the RD5.6A diode should test at 5.6V, and thats with diode test on the meter, with power off? I was under the assumption diode testing is done with power off correct?

Sorry about the basic questions.

Click to expand...

To confirm a zener diode is OK measure the voltage at the cathode. (meter on DC volts with the unit powered up)

If you have 5.6 (or whatever) its OK

To cold test there should be about 0.6 volts drop one way on the diode test on your meter, vertually open circuit the other way as Jeff points out.

Thanks so much. Even if this board becomes parts, this generous help is teaching me a great deal.

I will report back hopefully with some results.