Author Topic: quick electrical question  (Read 1739 times)

Offline Sbrem

  • Ludicrous Speed Member
  • *******
  • Posts: 6030
quick electrical question
« on: July 13, 2023, 09:01:08 AM »
On our old trusty MHM Synchro S, we are replacing a transformer which sends 24vdc to the display. The old unit and the replacement looks world's apart, but we have it figured out, mostly. On the original, the + and - output terminals have 2 wires each going to the display. The folks at SPSI told us to use an 8 amp fuse on the positive side. On the old unit, the 2 positive wires were joined together, on the positive terminal, same with the negative. On the replacement unit, there are 2 terminals for positive and 2 terminals for negative. Finally, the actual question, do we need to fuse both positives? Or can we join them together with a single fuse?
Second question, which I should know, but I'm not 100% sure; there are 3 lines going into the old transformer input, the ground, and a black, and blue. I think black is the N and the blue is the L, but I'd love someone who know better to confirm it. For some reason, we aren't getting the replies we need from folks we're dealing with, I'm sure they're busy. Thanks, all.

Steve

On second thought, I think that fuse goes on input to the transformer, the little red box is a fuse holder
« Last Edit: July 13, 2023, 09:37:57 AM by Sbrem »
I made a mistake once; I thought I was wrong about something; I wasn't


Offline Sbrem

  • Ludicrous Speed Member
  • *******
  • Posts: 6030
Re: quick electrical question
« Reply #1 on: July 13, 2023, 09:39:11 AM »
first picture, the new unit
I made a mistake once; I thought I was wrong about something; I wasn't

Offline Sbrem

  • Ludicrous Speed Member
  • *******
  • Posts: 6030
Re: quick electrical question
« Reply #2 on: July 13, 2023, 09:41:12 AM »
2nd picture, old unit
I made a mistake once; I thought I was wrong about something; I wasn't

Offline 3Deep

  • !!!
  • Ludicrous Speed Member
  • *******
  • Posts: 5232
Re: quick electrical question
« Reply #3 on: July 13, 2023, 09:56:12 AM »
Don't have any answers for you, but I know what your going through, had to replace a panel in our flash unit which cause us to reset the whole press main head what a pain.  Would really be nice to replace the part with the same part that came off plug and play, but as the press gets older the more unlikely are you going to find the exact part.
Life is like Kool-Aid, gotta add sugar/hardwork to make it sweet!!

Offline ebscreen

  • !!!
  • Gonzo Member
  • ******
  • Posts: 4215
Re: quick electrical question
« Reply #4 on: July 13, 2023, 11:47:38 AM »
Hi Steve. We have sameish press, (this particular electrical portion has a few revisions...)
if you need pics of anything let me know.

>>On the old unit, the 2 positive wires were joined together, on the positive terminal, same with the negative.
>>On the replacement unit, there are 2 terminals for positive and 2 terminals for negative.

You can use both terminals or one, doesn't matter, they are physically bonded.


>>Finally, the actual question, do we need to fuse both positives?
Current for both needs to pass through an appropriate fuse. If they were originally connected to the output of one 8 amp
fuse that is what I would do. It's a little odd (you typically want one fuse per circuit) but don't rock the boat.

MeanWell are pretty decent power supplies and usually have over-current protection as well. They'll shutoff automatically until
power cycled. Also, they are adjustable within a small range. That white potentiometer to the right is the adjustment, and it's
probably not a bad idea to check the output (under load/fully connected) at 24v with a multimeter between the V+ and V- terminals.


>>I think black is the N and the blue is the L
Likely correct, you can carefully check with a multimeter between black/blue and ground. Line will have voltage.
It's not particularly important in this regard though, the power supply will operate either way.




Lastly, how did you condemn the transformer/power supply?
Transformers themselves are pretty low on the electrical component failure chart.
The rest of the smoothing circuitry can be suspect though (those big caps in first pic)


On our sameish press we had the craziest gremlin involving the same component.
Machine would be operating fine and then contactor would start buzzing/random lights flickering.
Changed contactor didn't help. Checked incoming voltage and it was fluctuating wildly while operating, started tracing back
to panel. Before tearing conduit down I watched closely in the machine panel and noticed arcing.
Hot wire into 24v transformer had come loose (or had always been?) and was wreaking havoc.
Just a data point.

Lastly lastly S-Type manual is attached. MHM was really good about including schematiks.





Offline Sbrem

  • Ludicrous Speed Member
  • *******
  • Posts: 6030
Re: quick electrical question
« Reply #5 on: July 13, 2023, 12:45:00 PM »
We're up! MHM said to use both fuses, can't hurt. Once we had the connections correct, all was fine. Incoming 220v, blue is neutral, black is the line. The MHM guy says he calls it "bluetral" to remember it. EB, thanks so much. I should have posted yesterday, we were waiting hours and hours for some replies. I'm so glad this place was saved...

Steve

The folks at SPSI determined it was that transformer, especially since the machine had good going over pre-spring, a tech here for a couple of days, so it would have been running right for him. We left on 6/30 (we never shut it off), closed for the week of the 4th, came back Monday and it wouldn't run.
« Last Edit: July 13, 2023, 01:24:47 PM by Sbrem »
I made a mistake once; I thought I was wrong about something; I wasn't

Offline Maxie

  • !!!
  • Gonzo Member
  • ******
  • Posts: 1311
Re: quick electrical question
« Reply #6 on: July 15, 2023, 03:18:39 AM »
I've had to replace my transformers on my E and S type.      Took a while to work out what the problem was on the E Type.     The transformer read 24v standing but as we switched on heads it dropped until the machine stopped printing.
Easy to remember, Blue is the sky, neutral no life N, brown (black on old units) is the earth where there is life L.
Maxie Garb.
T Max Designs.
Silk Screen Printers
www.tmax.co.il