P9300W fault

[Skelton Junction]

Hoping it’s a simple fix from the forum’s experts. 
HMDCC powered by the above 4 amp brick through bus and wired fishplates. There are half a dozen LEDs illuminating the buffers on the bus too. I’m using the HM7000 app. 
Suddenly the layout track went dead apart from a weakish pulse every second. The buffer lights are the giveaway. 
 

Any clues as to what has happened would be gratefully received. 
 

[dBerriff]

To try to understand the circumstances:

What was the loading at the time in terms of locomotives? The LEDs will/should draw very little current.

The pulsing suggests a system trying to reset itself, finding a short / current overload, and shutting down again. This sequence repeats every second.

This is where a multimeter would come in useful to measure the track resistance.

Edited September 22 by dBerriff

[Skelton Junction]

Four locos were active (5 decoders as two are in the HST). All have been removed from the track. There are three 6010s powered by the bus too (forgot to mention those). Buffers still blinking. 
 

[dBerriff]

What I would do is:

a: I assume you have done this but for completeness: check that nothing has fallen on the track to bridge the rails. 

b: disconnect components one at a time to try to find out what is causing the problem. I would start with the 6010s as the active components. The LEDs should be trouble free but check the wiring. The soldered connections can be unprotected (I have blown a transistor when LEDs accidentally touched during a demo).

Edited September 22 by dBerriff

[Skelton Junction]

Much appreciated @dBerriff

Did as you suggested using a £10 track tester, one of those little led ones that light up according to current. Narrowed it down to one of the red dropper wires becoming loose and shorting to its black counterpart. Big sighs of relief all round and I think a graphic demonstration of Occam’s Razor.  

[dBerriff]

Good, in that it is nothing expensive that has changed or failed. Those little track testers are really useful and easier to use than a multimeter.

[dBerriff]

Insulating tape could be helpful to avoid a repeat? You only need to insulate one polarity. There a few types of wire-tap connectors that can be used and these will insulate the joints. Example:

https://www.amazon.co.uk/gp/aw/d/B07F3SGJXR

It is essential that they match the wire gauge otherwise connections can fail. 

[ntpntpntp]

1 hour ago, dBerriff said:

Good, in that it is nothing expensive that has changed or failed. Those little track testers are really useful and easier to use than a multimeter.

Definitely useful, I have an ancient Minitrix track tester (bulb rather than LED).    It's still useful to have and use a multimeter though.  The track tester is great for simple presence / absence of track power but doesn't indicate high resistance (eg. a bad track joint) which only manifests itself under a load such as a running loco. 

[96RAF]

Looking at my files I see this. You were fortunate nothing went sparky:

P9300W 4A PSU - Broadly works on a constant power basis… i.e. as the load increases above the rated power level, the voltage drops thus maintaining constant power while increasing amps. Protection starts at 4.5A (14.5V) and shuts down at 8A (7.5v) to pulse mode. Power Rated = 60W   Power Max = 80W

 

[Fishmanoz]

Apologies Skelton but why do so many people starting topics include a proxy for what their problems are rather than detailing them specifically.

In this instance, the specific title is “P9300W 4 Amp PSU Resetting Repeatedly” 

And I add the “4 Amp PSU” so people don’t have to guess/remember what a P9300 is.

Good titles help in 2 ways:

• people who know how to fix a problem are more likely to open a thread when it’s clear what the problem is
• its easier to search for when someone else has the same problem later

With that, soap box dismount performed, normal transmission resumed.

[Skelton Junction]

Agree with requirement for clarity but I did not know that the psu was resetting, just that it was on the blink 😊 

 

[dBerriff]

I assume that if anyone asks for help then they don't know the answer, so I am happy to ask a few questions to try to elicit a better description of what has happened and what is still happening. By the time you have the experience and knowledge to frame the perfect heading, you probably have the experience, knowledge and skills to complete your own fault finding. 😁

[96RAF]

1 hour ago, Skelton Junction said:

Agree with requirement for clarity but I did not know that the psu was resetting, just that it was on the blink 😊 

 

Not on the blink at all, in fact performing as designed to cope with an external fault condition.

[Skelton Junction]

Yes, as the archive files you mentioned described. Apologies, my “on the blink” comment referred to the aforementioned flashing lights on the buffers as much as the old school terminology for something not working. The psu was working perfectly which is more than be said for my wiring faux pas. 

[What About The Bee]

2 hours ago, Fishmanoz said:

easier to search for when someone else has the same problem later

No problem finding the post Fishy.  I do understand the urge to categorize posts and sort them into the appropriate bins.  It does make for an orderly appearance.  I'm just not sure it is useful as a search function, when other far more powerful tools are available.

@Skelton JunctionGot the pun before the explanation!  😁  Well played!

Bee

[Fishmanoz]

Fair criticism for using “Resetting” but “Flashing On and Off” might have been available?