# Panasonic PBX Troubleshooting



## wrbrb (Aug 18, 2020)

Sorry if this is the wrong forum, but I'm trying to get some help with a Panasonic 616 PBX (KX-T61610) I just bought. I plug it in and turn it on, and the power light doesn't turn on, and when I connect a Panasonic KX-T7030 phone to any of the 16 internal ext jacks, I don't get a dial tone on the handset but I am able to hear the tones of the keypad if I press the number pad buttons. I tried disconnecting the battery and pressing the reset button, also tried moving the system switch between program and set, but no change. All the fuses look fine. Any ideas to troubleshoot this would be greatly appreciated.


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## supers05 (May 23, 2015)

Deleted....
I just realized that this is an old PBX. You'll have to figure out if your power supply is working.


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## wrbrb (Aug 18, 2020)

supers05 said:


> Deleted....
> I just realized that this is an old PBX. You'll have to figure out if your power supply is working.


Thanks for reading the post. Do you know if there's anything shown here I could test with a multimeter that would be worth my time attempting? I wasn't sure if that was one or more transformers near the power cord.


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## supers05 (May 23, 2015)

wrbrb said:


> Thanks for reading the post. Do you know if there's anything shown here I could test with a multimeter that would be worth my time attempting? I wasn't sure if that was one or more transformers near the power cord.
> 
> View attachment 682877


Looks like a fuse holder in the top right corner. Unfortunately I don't have a schematic of that device so I'm only guessing. The yellow /brown board looks like the power adapter board. It'll be supplying both AC and DC. It looks like there are at least 3 separate buses.

Top green board looks like the interface board and the bottom green will be the control logic and mux board.


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## wrbrb (Aug 18, 2020)

Thank you. I thought this would be a fun project, but received it damaged in the way described via shipping (at least it was advertised as fully functional and fully tested, which I believe). 

I know it's old, but am leaning toward something having been knocked loose or physically damaged in shipping vs worn out. I'll take it apart further and look for damage, maybe will revisit the circuit/power troubleshooting if I come up empty on the damage inspection. I appreciate your help. This might be a good electronics diagnosis learning opportunity.


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## supers05 (May 23, 2015)

wrbrb said:


> Thank you. I thought this would be a fun project, but received it damaged in the way described via shipping (at least it was advertised as fully functional and fully tested, which I believe).
> 
> I know it's old, but am leaning toward something having been knocked loose or physically damaged in shipping vs worn out. I'll take it apart further and look for damage, maybe will revisit the circuit/power troubleshooting if I come up empty on the damage inspection. I appreciate your help. This might be a good electronics diagnosis learning opportunity.


Check that fuse before doing anything. It could even be knocked loose.


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## wrbrb (Aug 18, 2020)

I pretty much completely disassembled the whole thing looking for damage, burns, anything loose, and couldn't find anything. I consider it an accomplishment that I got it all back together without any left over screws. 

The fuses were all secure, nothing looked burned or damaged on either side of the boards, nothing loose. 

The only thing potentially slightly off was the bottom of the board under where the power switch is, looked like there was some orange discoloration. I didn't think that was enough to cause a problem - maybe just messy flux?

I also didn't do anything to disassemble or remove the two silver cubes at the bottom (both transformers of some kind?).

Is there any basic testing I could try with a multimeter to see that power is or isn't getting to the various boards or components, or would that require a wiring diagram?


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## wrbrb (Aug 18, 2020)

I apparently found a wiring diagram that is over my head but maybe useful to someone in the future who comes across this.


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## supers05 (May 23, 2015)

wrbrb said:


> View attachment 682931
> 
> View attachment 682935


Start with checking that your indeed have 120v at the fuse, and work your way down these connectors checking for the respective voltages

PS. Yes those are transformers. One has multiple secondaries. Fairly hard to get your hands on. 

















PS. There are 4 fuses and they all have to be good. Double check the switch.

PPS. Hopefully I've referenced the correct pictures in the quote. I can't see them.


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## wrbrb (Aug 18, 2020)

That's great, thank you. I appreciate your help and that you're steering me in the right direction. The fact that when a phone is connected you can at least hear the keypad tones in the earpiece leads me to believe the unit is partially working. I'll try to test the voltages at those different points and report what I find (it might take me some time to get to this). Thank you!


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## supers05 (May 23, 2015)

wrbrb said:


> That's great, thank you. I appreciate your help and that you're steering me in the right direction. The fact that when a phone is connected you can at least hear the keypad tones in the earpiece leads me to believe the unit is partially working. I'll try to test the voltages at those different points and report what I find (it might take me some time to get to this). Thank you!


If it's multiple extensions (ports) all doing the same, it's telling me that it's either the off hook detection, or the tone generator is having issues. For both, most likely low power. Check for voltage across the power LED. since you it's not lit, I'm thinking early up steam, somewhere with the incoming power or the power supply board.


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## GrayHair (Apr 9, 2015)

As I think I said in the other thread, electrolytic capacitors in particular don't age well. That's why standbys need to be powered up at least once a year. In many electronics shops the new guy forms the electrolytics get formed every 6-12 months. Many years ago I was that new guy.
The system may have tested functional, but we don't know when. However, if none of them popped when you powered it up, they are probably OK for now.


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## wrbrb (Aug 18, 2020)

This evening I started small and used my multimeter with the power off to do the following: 

Tested resistance across all four fuse holders with fuses installed and power off: 0 ohms
Tested resistance across power switch in off position with power off, OL. In on position with power off, 0 ohms.
Tested power, day mode, and night mode LEDs with LED board disconnected from device, with multimeter in diode/resistance mode (same thing?), touching tester to leads just under the colored lenses, OL regardless of which test lead was on which LED lead (positive/negative). 
Tomorrow I was planning on turning the power on and measuring voltages at the various connectors to see if they match the schematic. Anything I should do before that, or cautions I should take while working with this with the power on and cover off and various components electrified?


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## wrbrb (Aug 18, 2020)

Did some more testing with the power on (see photo). Unless I'm doing something wrong with the multimeter, I think I'm onto something, just don't know how to trace from these readings to the next component that might be suspect - I suppose further back toward the power source?


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## wrbrb (Aug 18, 2020)

Added some J10 readings:


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## wrbrb (Aug 18, 2020)

I think I'm seeing that some voltages are definitely out of range, but I'm not exactly sure how to safely test the rest of the power board area:


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## wrbrb (Aug 18, 2020)

With J10 readings out of spec, I'm now thinking maybe I should focus on the power switch/cord board. Just not exactly sure how to test this part. I guess I'll start reading up on electronic component testing!


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## GrayHair (Apr 9, 2015)

All I see is capacitors, a couple of inductors and a varistor. The battery may act as a filter and might be required for proper operation (and to get the readings listed on J10).


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## wrbrb (Aug 18, 2020)

Thanks for your comment as I'm a little lost at the moment. I do think the battery is optional, however - it is there to store the programming settings.


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## supers05 (May 23, 2015)

wrbrb said:


> With J10 readings out of spec, I'm now thinking maybe I should focus on the power switch/cord board. Just not exactly sure how to test this part. I guess I'll start reading up on electronic component testing!
> 
> View attachment 683245


What voltages are you getting?


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## wrbrb (Aug 18, 2020)

supers05 said:


> What voltages are you getting?


If I'm reading the diagram correctly, at J10 I'm supposed to be getting +9V, +12V, -12V, RLYG (?), RLYB (?), -24V, and GND. Across those to the ground pin I'm getting: 

a few negative mV for the +9V,
13.37V for the +12V,
a few negative mV for the -12V,
a few mV on the two RLYG/RLYB or whatever they say,
and -26V on the -24V.

Post #15 also has some other readings - image of notes I took while testing:



wrbrb said:


> Added some J10 readings:
> 
> View attachment 683127


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## supers05 (May 23, 2015)

wrbrb said:


> If I'm reading the diagram correctly, at J10 I'm supposed to be getting +9V, +12V, -12V, RLYG (?), RLYB (?), -24V, and GND. Across those to the ground pin I'm getting:
> 
> a few negative mV for the +9V,
> 13.37V for the +12V,
> ...


I didn't see that post earlier. 

Your 5V rails are broke. You'll have to trace that down.

Did you check fuse f3?

What is the ac voltage on pin /wire 4/5 on CN14?


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## wrbrb (Aug 18, 2020)

I had checked all the fuses for continuity across the fuse holders and none of them had any resistance. Is there a voltage check to perform also? 

And regarding testing AC on CN14, what would my ground point be for each of the pins - just one of the screws attaching that board to the case? I see the CN14 called out at the top part of the gray area in the schematic shown below but it doesn't look like it's drawn in the same simple way as the other cables.


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## supers05 (May 23, 2015)

wrbrb said:


> And regarding testing AC on CN14, what would my ground point be for each of the pins - just one of the screws attaching that board to the case? I see the CN14 called out at the top part of the gray area in the schematic shown below but it doesn't look like it's drawn in the same simple way as the other cables.


I need the voltage between them, not to ground, it chasis.

Is the cable coming directly off of the transformer when you have it assembled. They are both gray.

PS. The fuses in this case will show continuity even when open. You have to remove them from the board to test them.


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## wrbrb (Aug 18, 2020)

supers05 said:


> I didn't see that post earlier.
> 
> Your 5V rails are broke. You'll have to trace that down.
> 
> ...


8.8V across pins 4/5 on CN14.
0 ohms each across the ends of F1, F2, and F3 when removed from the board.


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## wrbrb (Aug 18, 2020)

8.8V across pins 4/5 on CN14.
0 ohms each across the ends of F1, F2, and F3 when removed from the board.

And here are the transformer cables:


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## supers05 (May 23, 2015)

8.8v AC looks good from the schematic. You should have ~5v DC across C11 and across D19. 8.8v DC should be across C8.


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## wrbrb (Aug 18, 2020)

supers05 said:


> 8.8v AC looks good from the schematic. You should have ~5v DC across C11 and across D19. 8.8v DC should be across C8.


I only got around 8 mV ("m V" on the multimeter display) across D19 and couldn't reach the two capacitors with my test leads so will have to try unscrewing the board and flipping it over later to get readings on those. I really appreciate all the help with this, it's a good learning experience.


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## supers05 (May 23, 2015)

wrbrb said:


> I only got around 8 mV ("m V" on the multimeter display) across D19 and couldn't reach the two capacitors with my test leads so will have to try unscrewing the board and flipping it over later to get readings on those. I really appreciate all the help with this, it's a good learning experience.


You're closing in on the problem.


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## wrbrb (Aug 18, 2020)

supers05 said:


> You're closing in on the problem.


Okay, just tested again with the board removed and got the following:

D19: 8.9 mV DC
C8: 10.41 V DC
C11: started out in the mV, slowly climbed and a couple minutes later tested 1.1V DC and was climbing about 0.1V DC every second or so.


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## supers05 (May 23, 2015)

C10? C9?


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## wrbrb (Aug 18, 2020)

supers05 said:


> C10? C9?


C10: 10.31 V DC
C9: 8.4 mV DC
C5: 13.38 V DC
C4: 19.10 V DC
D12: 5.74 V DC
D20: 250 mV DC

C11: seems to be stopped climbing at around 1.175 V DC, or has slowed way down


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## supers05 (May 23, 2015)

wrbrb said:


> C11: seems to be stopped climbing at around 1.175 V DC, or has slowed way down


That is your meter charging it. There's a wire break somewhere there.

Check the resistance of R14100


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## wrbrb (Aug 18, 2020)

supers05 said:


> That is your meter charging it. There's a wire break somewhere there.
> 
> Check the resistance of R14100


With the power on, across R14 I'm getting 0 ohms. Testing the contacts on the underside, it's flashing between 0 ohm and 0 Kohm but always 0.000 when it flashes. On the top side pins coming out of the resistor it's flashing between 0.000 and O.L. ...But with the power off it's 99.6 ohms.


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## supers05 (May 23, 2015)

wrbrb said:


> With the power on, across R14 I'm getting 0 ohms. Testing the contacts on the underside, it's flashing between 0 ohm and 0 Kohm but always 0.000 when it flashes. On the top side pins coming out of the resistor it's flashing between 0.000 and O.L. ...But with the power off it's 99.6 ohms.


You always test resistance with the power off.

Does your meter have a diode or transistor test mode?

I want to test Q3. If you only have a diode test mode, test from the collector to the emitter, and then reverse. Then from the emitter to the base.


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## wrbrb (Aug 18, 2020)

supers05 said:


> You always test resistance with the power off.
> 
> Does your meter have a diode or transistor test mode?
> 
> I want to test Q3. If you only have a diode test mode, test from the collector to the emitter, and then reverse. Then from the emitter to the base.


Hopefully I didn't damage anything else by testing resistance for so long with power on. 

For this, I tried with power off and power on in diode mode.

From red to black, with power off:
C to E, 0.65V
E to C, 0.475V
E to B, 0.459V

From red to black, with power on:
C to E, OL
E to C, 0V
E to B, -0.750 V

Used the mode two turns to the left, pressed FUNC until I saw an image of a diode:


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## wrbrb (Aug 18, 2020)

Would you have any idea what to test next from here?


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## supers05 (May 23, 2015)

Talked to a friend about it. We think there's possibly a broken solder joint somewhere around the zenier diode. Take a real close look at the bottom traces and solder joints.


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## supers05 (May 23, 2015)

In diode test mode, check across the zenier (D19) in both directions. (power off)


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## wrbrb (Aug 18, 2020)

supers05 said:


> Talked to a friend about it. We think there's possibly a broken solder joint somewhere around the zenier diode. Take a real close look at the bottom traces and solder joints.


I removed the board and examined it in bright light and couldn't find anything wrong. All the solder points on the bottom looked fine, and everything on the top side looked connected, with the exception of a couple components that were kind of squashed down a little bit. I used a toothpick to check that everything seemed to be connected. In the process of removing the board, I broke the solder point on the ground wire on the opposite end of the board (pulled the socket right off the board when trying to pull it off). I soldered that back on, and when I connected everything back together, I somehow now have a power LED, day mode LED, and dial tones!

I'm guessing you were right and there was a break somewhere on this board, and either I moved something back into place with the toothpick or the ground wire had been loose the whole time?


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## supers05 (May 23, 2015)

It could very easily been that ground, as it uses it as a reference. Either that ground or another connection that's potentially still broken would have easily shaken loose during transit. Measure your voltages across everything you've measured so far so you have a baseline.


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## supers05 (May 23, 2015)

It was fun, we don't get to troubleshoot electronics at this level much these days. It's usually just replace the whole board, or appliance. Just getting the schematic really is hard, I wish they provided that on today's stuff.


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## wrbrb (Aug 18, 2020)

supers05 said:


> It was fun, we don't get to troubleshoot electronics at this level much these days. It's usually just replace the whole board, or appliance. Just getting the schematic really is hard, I wish they provided that on today's stuff.


It was actually pretty fun, you're right - even with limited equipment and even more limited knowledge of testing. 

When taking measurements for the future, is there a good reference I could use to know what components are tested with power off vs power on? I think that was one of my bigger issues. 

At this time I'm not exactly ready to take a deep dive into electronics repair, but I would like to know enough to be able to trace issues and test against schematics, and keep this PBX alive.


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## supers05 (May 23, 2015)

wrbrb said:


> It was actually pretty fun, you're right - even with limited equipment and even more limited knowledge of testing.
> 
> When taking measurements for the future, is there a good reference I could use to know what components are tested with power off vs power on? I think that was one of my bigger issues.
> 
> At this time I'm not exactly ready to take a deep dive into electronics repair, but I would like to know enough to be able to trace issues and test against schematics, and keep this PBX alive.


Resistance and diode testing is always done with the power off. Voltage testing is with the power on. Sometimes you'll use ground as a reference, sometimes you'll be measuring across components for voltage. Once in a while you'll be verifying current flow in series with some section.


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## wrbrb (Aug 18, 2020)

supers05 said:


> Resistance and diode testing is always done with the power off. Voltage testing is with the power on. Sometimes you'll use ground as a reference, sometimes you'll be measuring across components for voltage. Once in a while you'll be verifying current flow in series with some section.


Thank you very much for your help with this and all the HVAC and other issues I and other people post about. Really appreciated.


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