P140 turns off at random

[deSitter]

This has been a very reliable keyboard like the P120 before it. But recently it started simply shutting down.

I changed out the power adapter and will see how that goes.

Anyway I did all the internal long tests P41, P42, P43, and P45, it's all fine, the tone generators all PASS, all onboard tests pass. Everything works. Could this just be oxidation on the power jack?

Thanks for any advice from similar experience.

-drl

 

[delaware dave]

Possible causes:

overheating due to blocked vents

is it near a heating source

are you using the Pa-5d or PA-150 power adapter

is the adapter near a heat source

faulty standby/on switch

some keyboards now have an auto off function, when the keyboard is inactive for a period of time the keyboard shuts off. Some models that have this feature also have the ability to turn this feature on an off. Check for this.

 

[deSitter]

Possible causes:

overheating due to blocked vents

is it near a heating source

are you using the Pa-5d or PA-150 power adapter

is the adapter near a heat source

faulty standby/on switch

some keyboards now have an auto off function, when the keyboard is inactive for a period of time the keyboard shuts off. Some models that have this feature also have the ability to turn this feature on an off. Check for this.

Hi, I was using the PA-5D that came with the keyboard and first suspected that, so it's running on a known-good 12v 2A supply. It is not near a heat source. Everything works perfectly while it is running. Thanks for the response.

-drl

 

[happyrat1]

How long on average does it run before it shuts itself down? Are there any error messages coming up when it happens?

Also are you located in a rural area that's known for noisy power lines or frequent brownouts?

Gary

 

[deSitter]

How long on average does it run before it shuts itself down? Are there any error messages coming up when it happens?

Also are you located in a rural area that's known for noisy power lines or frequent brownouts?

Gary

It is random. I played for hours yesterday and left it on. This morning it was off. I turned it on and it went off immediately. Then it stayed on for 10 minutes. Etc. I strongly suspect that an electrolytic capacitor has gone south on me, and will be disassembling the keyboard as a next step if someone here doesn't have direct advice. The P140 does not have auto off, in fact it has been on for years until this problem developed. I do know that all the ROMs and RAM are fine, I have tested them several times. My first suspect is a large capacitor on the AMP board right after the 12V DC input board. I know from telescopes and computers that the recent generation of Chinese capacitors is the bane of everyone's electronic existence

-drl

 

[happyrat1]

Electrolytic caps are a good place to start.

Easiest way to check a cap without desoldering is to use an ESR meter. (Equivalent Series Resistance)

They can be bought for around $50-$60 USD these days and are very useful for diagnosing in circuit problems.

https://www.amazon.com/Signstek-MESR-100-Ranging-Circuit-Capacitor/dp/B00GYSFOM6/

https://www.youtube.com/results?search_query=using+an+ESR+meter

Much more effective than randomly swapping caps or eyeballing for leaks and bulges.

Gary

 

[deSitter]

Electrolytic caps are a good place to start.

Easiest way to check a cap without desoldering is to use an ESR meter. (Equivalent Series Resistance)

They can be bought for around $50-$60 USD these days and are very useful for diagnosing in circuit problems.

https://www.amazon.com/Signstek-MESR-100-Ranging-Circuit-Capacitor/dp/B00GYSFOM6/

https://www.youtube.com/results?search_query=using+an+ESR+meter

Much more effective than randomly swapping caps or eyeballing for leaks and bulges.

Gary

Thanks for that!

-drl

 

[deSitter]

OK I have a suspect. The capacitors all look great, no shorts, no leaks, no domes, the electolytics ramp up correctly as they charge. The marked capacitors are by Sanyo. Looks like typically excellent Japanese choice of materials and components.

I see there is a current-dependent resettable fuse in the DC-in circuit. I had never seen one of these - it looks like a large, square capacitor and that's what I thought it was. It has a resistance of about 7 ohms and according to the data sheet, should be near zero. I am planning to short this fuse for the time being and see if that cures the problem. If it does I will install a replacement. Comments?

-drl

 

[happyrat1]

No comment. I'm not even familiar with this current activated circuit breaker/fuse. I have no idea how it functions or how to diagnose if defective. Do you have a link to a data sheet?

Gary

 

[happyrat1]

BTW, are there any tantalum electrolytics on the board? Those might be worth testing as well.

Gary

 

[deSitter]

No comment. I'm not even familiar with this current activated circuit breaker/fuse. I have no idea how it functions or how to diagnose if defective. Do you have a link to a data sheet?

Gary

Bourns MF-R250-0-10

MF-R250-0-10 Bourns | Mouser

MF-R250-0-10 Bourns Resettable Fuses - PPTC 2.5A 30V 0.025ohm Hold 2.5 Trip 5.00 datasheet, inventory, & pricing.

www.mouser.com

-drl

 

[deSitter]

BTW, are there any tantalum electrolytics on the board? Those might be worth testing as well.

Gary

Yes they are all OK, none shorted. Those are very touchy to over-voltage but tend to fail spectacularly so they are easy to diagnose.

-drl

 

[happyrat1]

There's no internal schematic on the data sheet so I still have no idea how it works, but, there are test conditions listed. I would try measuring current flow thru a series resistor if there is one in circuit, else desolder a leg and measure current directly.

Agreed internal resistance should be significantly less than 1 ohm. But that could just be your multimeter if it's a cheapo and not a Fluke.

Milliohms can be tough to measure with consumer grade equipment. Your test leads might even be adding the 7 ohms.

Gary

 

[happyrat1]

If you own an infrared thermometer check to see if the operating temp is nominal as well.

Try heating it up a bit and see if it trips.

EDIT >>> Use a hairdryer, not a heat gun.

Gary

 

[deSitter]

So far so good. In the service manual parts list, I noticed that ONLY the AC adaptor (all varieties), the resettable fuse, and the DC-in jack are marked with an exclamation point as critical parts. There must be very strict rules in Japan regarding DC-input power and its handling.

-drl