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Old 06-14-2020, 03:08 AM   #1
HellasTechn1
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Default ZD-985 desoldering station Power supply failure

Good day to all !

I have a ZD-985 station. It suddenly went dead during normal use. I opened it up and found the PSU has died.
The PSU is exactly the same as the one on the ZD-915 station mentioned and pictured here:
https://www.badcaps.net/forum/showthread.php?t=78148
and here :
https://badcaps.net/forum/showthread.php?t=39651
I checked all the components that I could including the mosfet, rectifier , capacitors, optocouplers, diodes, fuse and all appear in good condition. So I ordered and replaced the switching IC (CQ1565RT). The (2200uf 25V) capacitors measured about 2100 uf capacitance and 0.something ohms ESR.
When I put in the new one the PSU came to life and so did the station but after a few seconds it died again with exact same symptoms.
I suspected the heating element which appears to be about 110Watt not 80 because at 18Vt it draws 6A. So I thought that maybe the heating element and pump drive the PSU too hard.
I again changed the switcher and again it came back to life. This time I disconnected the heating element and placed a 5A fuse between the +18V output and the vacuum pump. This time I noticed that after three short trigger pushes with the pump going on and off the PSU died again…
I have no idea what causes the IC to die like that. Also I have trouble finding a 18V PSU with enough current capacity (more than 8A) For the time being I have removed its transformer and feed 18V DC directly between the transformers grounded pin and the one going to the rectifier from my bench PSU and current consumption varies from 9A when the heating element and pump are on to 2A when heating element is in idle and pump is off.

Any ideas or suggestions ? THANK YOU !
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Old 06-14-2020, 03:29 AM   #2
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Default Re: ZD-985 desoldering station Power supply failure

2A, you should see the load pulsing with the element
2A sounds low for heating, but far too high for just running the mcu, lcd etc.

Last edited by stj; 06-14-2020 at 03:58 AM..
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Old 06-14-2020, 03:55 AM   #3
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Default Re: ZD-985 desoldering station Power supply failure

Quote:
Originally Posted by stj View Post
2A, you sould see the load pulsing with the element
2A sounds low for heating, but far too high for just running the mcu, lcd etc.
The current is not stable. It varies as the heting element comes closer to the pre set temp. when it reaches that temp then current falls down to 2A. I suppose that the mosfet is never turned fully off. It supplies the 2A to maintain the temprature reached. It makes sense to me. However 2A is not nearly enough current to cause damage to the switching IC. Note that when it blew my last IC i only had the vacuum pump connected while the heating element disconnected.
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Old 06-14-2020, 03:59 AM   #4
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Default Re: ZD-985 desoldering station Power supply failure

i need to open mine soon, the fan needs replacing.
i suppose while i'm in it i should check or recap the psu!
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Old 06-14-2020, 04:10 AM   #5
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Default Re: ZD-985 desoldering station Power supply failure

At work i have a ZD-987 station that i opened out of curriosity and expected to see the same PSU. To my surprise the 987 uses linear trensformers. Far better solution if you ask me. Though it only had one 100uf 25V smoothing cap . I would definetly be interested to replace the SMPS with that transformer. The secondary side of my SMPS can be cut off and connected to the 18V supply line of the transformer or even beter i can replicate the ZD987's power supply boards and use them with larger and better capacitors ofcource.
How can i get one of these transformers ? I googled the numbers on it and came up empty. The transformer was marked ZDT-80-3, it gives a wiring diagram but no wattage or amperage rating. I wonder if i could use some other 18V linear transformer but what wattage rating ?

Last edited by HellasTechn1; 06-14-2020 at 04:12 AM..
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Old 06-14-2020, 04:12 AM   #6
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Default Re: ZD-985 desoldering station Power supply failure

Quote:
Originally Posted by stj View Post
i need to open mine soon, the fan needs replacing.
i suppose while i'm in it i should check or recap the psu!
Is it a 985 station ? i dont think the 985's come with a fan but you should definetly change the caps with 3300uf 35V

Last edited by HellasTechn1; 06-14-2020 at 04:22 AM..
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Old 06-14-2020, 06:01 AM   #7
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Default Re: ZD-985 desoldering station Power supply failure

Do you have a power supply to run the heater unit by it self and set the current to 1.5 amps

I can probably tell you why the switching power supply has this failure there is a heater mosfet that has shorted in the ON position replace it

When you put in the next switching power supply regulator unhook the heater pins from the connector and see if you can run it that way if you can then the heater mosfet is bad

One thing to make sure of is that you have a temperature reading on the display if not you will have the controller at full power output and not controlling the temperature and the heater will self destruct you always need to check that you have a temperature reading when you first power up ( this is a poor design)

There are two different software versions of this Desoldering Gun station one version powers up the heater when power is applied ( if you see this “——— “ or see this ERR ) at power up then the “ temperature sensor has failed” the other version applies power when the controller has powered up this the better version of the two

If you have the first version this is part of the problem the switching power regulator has not stabilized and causes the switching power supply regulator to shutdown and restart ( one note is this switching power supply board is not the best design and it some what is under rated for this application

You could use a different switching power supply design but here is a word of advice you have a couple of problem to work out you have a +10 volt and a -5 volt power rail for the controller now you can take the part of the controller board off of power supply board and use it to power up the controller board BUT you must make sure that you have the +10 volts and the -5 volts that works correctly before you put power to the controller board because if the -5 volts rail is not working correctly then the temperature sensor circuit will not work correctly and you might not notice that the temperature is climbing as it should and destroy the heater

The part of +10 volts and the -5 volts power rail has the following parts ( + side one of this circuit 1 watt resistor a 5 volt Zener diode and another resistor - side of the power supply ) I post a picture of this circuit because I made one so I could make it run off of battery power ( it does need a PWM controller for it to work correctly for the heater circuit )

The last picture is the version that uses a transformer

If you decide to use two transformers for the 10 volts and - 5 volts you could use a 9 volt transformer because the controller board has another 5 volt Zener diode for the +5 volts so be to concert about it being 10 volts but do not be tempted to use a 12 volt transformer for this I have not tried this so I do not know if there would any issues or not


I have both versions I replaced them with version two which works a lot better
Attached Images
File Type: jpeg B097758D-6E27-4599-B692-1F6028B78C20.jpeg (886.4 KB, 13 views)
File Type: jpg 8AE1A326-84DC-413F-9B1F-3EC9E7C42114.jpg (189.9 KB, 10 views)
File Type: jpg 39F5C0AF-4552-4AD7-A9A1-FBCE3830C7E8.jpg (235.1 KB, 9 views)
__________________
9 PC LCD Monitor
6 LCD Flat Screen TV
30 Desk Top Switching Power Supply
10 Battery Charger Switching Power Supply for Power Tool
6 18v Lithium Battery Power Boards for Tool Battery Packs
1 XBox 360 Switching Power Supply and M Board
25 Servo Drives 220/460 3 Phase
6 De-soldering Station Switching Power Supply 1 Power Supply
1 Dell Mother Board
15 Computer Power Supply
1 HP Printer Supply & Control Board * lighting finished it *


These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
2 Hem Saw Computer Stack Board

All of these had CAPs POOF
All of the mosfet that are taken out by bad caps

Last edited by sam_sam_sam; 06-14-2020 at 07:31 AM..
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Old 06-14-2020, 06:36 AM   #8
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Default Re: ZD-985 desoldering station Power supply failure

Quote:
Originally Posted by HellasTechn1 View Post
Is it a 985 station ? i dont think the 985's come with a fan but you should definetly change the caps with 3300uf 35V
There also two capacitors on the controller board that needs to be replaced as well but be very careful with this controller board it is easily damaged if you are ruff with it

I hope that the information that I provided you will help you fix and figure out how to fix your Desoldering station

Last edited by sam_sam_sam; 06-14-2020 at 07:34 AM..
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Old 06-14-2020, 08:27 AM   #9
stj
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Default Re: ZD-985 desoldering station Power supply failure

so a question,
how is the fan powered?
is it 12v or higher?
is it regulated?

i want to put a SUNON fan in it - but i dont want it to fail.
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Old 06-14-2020, 08:49 AM   #10
HellasTechn1
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Default Re: ZD-985 desoldering station Power supply failure

Quote:
Originally Posted by sam_sam_sam View Post
Do you have a power supply to run the heater unit by it self and set the current to 1.5 amps

I can probably tell you why the switching power supply has this failure there is a heater mosfet that has shorted in the ON position replace it

When you put in the next switching power supply regulator unhook the heater pins from the connector and see if you can run it that way if you can then the heater mosfet is bad

One thing to make sure of is that you have a temperature reading on the display if not you will have the controller at full power output and not controlling the temperature and the heater will self destruct you always need to check that you have a temperature reading when you first power up ( this is a poor design)

There are two different software versions of this Desoldering Gun station one version powers up the heater when power is applied ( if you see this “——— “ or see this ERR ) at power up then the “ temperature sensor has failed” the other version applies power when the controller has powered up this the better version of the two

If you have the first version this is part of the problem the switching power regulator has not stabilized and causes the switching power supply regulator to shutdown and restart ( one note is this switching power supply board is not the best design and it some what is under rated for this application

You could use a different switching power supply design but here is a word of advice you have a couple of problem to work out you have a +10 volt and a -5 volt power rail for the controller now you can take the part of the controller board off of power supply board and use it to power up the controller board BUT you must make sure that you have the +10 volts and the -5 volts that works correctly before you put power to the controller board because if the -5 volts rail is not working correctly then the temperature sensor circuit will not work correctly and you might not notice that the temperature is climbing as it should and destroy the heater

The part of +10 volts and the -5 volts power rail has the following parts ( + side one of this circuit 1 watt resistor a 5 volt Zener diode and another resistor - side of the power supply ) I post a picture of this circuit because I made one so I could make it run off of battery power ( it does need a PWM controller for it to work correctly for the heater circuit )

The last picture is the version that uses a transformer

If you decide to use two transformers for the 10 volts and - 5 volts you could use a 9 volt transformer because the controller board has another 5 volt Zener diode for the +5 volts so be to concert about it being 10 volts but do not be tempted to use a 12 volt transformer for this I have not tried this so I do not know if there would any issues or not


I have both versions I replaced them with version two which works a lot better
The Mosfet is okay. I have also tested it outside the PSU. My unit i think has te 1st software version since i can see the error message if the gun is not hooked up.

Like mentioned in my 1st post, the second time i replaced the switching IC i tried running the station without the heating element connected (the PTC was connected as well as all the other components).

So i try to figure out what causes the switching IC to fail that easily.

Also i want to use transformer but i do not know its characteristics...

Last thing is that there is a way to run the whole station from a single 18V power supply if you use the secondary part of the original PSU.
I Should have taken photos bit now i have it all assembled...

If you remove the transformer from the original smps, then you will notice that on the secondary side it only uses two pads. One is connected to the negative side of the capacitors and the other goes to the + of the rectifier (far left and far right sides of it) then from the middle of the rectifier it goes to the positive of the capacitors and the rest of the circuit. Now if you have the transformer removed you put the negative lead to the pad that goes to the negative of the caps and the positive lead to the pad that goes to the rectifier. That way the station works all right with just a 18V 10A or more PSU.

So like i said before i do want to use a linear transformer but with what specs ?
I do need a 18V but how many watts ?
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Old 06-14-2020, 08:51 AM   #11
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Default Re: ZD-985 desoldering station Power supply failure

Quote:
Originally Posted by sam_sam_sam View Post
There also two capacitors on the controller board that needs to be replaced as well but be very careful with this controller board it is easily damaged if you are ruff with it

I hope that the information that I provided you will help you fix and figure out how to fix your Desoldering station
I have noticed only one 330uf electrolytic on the controller board but didnt change it since its esr and capacitance is still good. Plus where i live, is hard to source good quality caps.
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Old 06-14-2020, 11:05 AM   #12
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Default Re: ZD-985 desoldering station Power supply failure

Quote:
Originally Posted by HellasTechn1 View Post
That way the station works all right with just a 18V 10A or more PSU.

So like i said before i do want to use a linear transformer but with what specs ?
I do need a 18V but how many watts ?
Probably can use a 10 amp transformer if you can find one 24 volt versions are more common at 10 amp

Now you could use a 24 volt transformer and remove some raps of winding until you get 16 to 18 volts and everything should work

Now if you see that your voltage drops more than a volt or more you be better off using a 9 volt transformer to just power the controller board and could use a 500 to 800 milliamperes transformer for this part
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Old 07-05-2020, 08:35 AM   #13
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Default Re: ZD-985 desoldering station Power supply failure

Any idea what the wattage would be for the 10A AC transformer ?

I know wattage is measured different in AC than in DC.

Last edited by HellasTechn1; 07-05-2020 at 08:37 AM..
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Old 07-05-2020, 01:46 PM   #14
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Default Re: ZD-985 desoldering station Power supply failure

Quote:
Originally Posted by HellasTechn1 View Post
Any idea what the wattage would be for the 10A AC transformer ?

I know wattage is measured different in AC than in DC.
The only you need to concern your self about is dose your rectifier is rated for 25 amps or better

Now like I said earlier you have a -5 volt and +10 volt power supply rail you have to concern your self with

Now you can use the part of this circuit board that has these parts

One word of caution when you first hook up power ( but before you hook up the Desoldering Gun set the temperature as low as you can set it make sure that you have control of the temperature to the gun this very important because if you do not have control of it ( it will destroy the gun heater or the mosfet controlling it )

Here is where you can find one

https://www.mpja.com/24V-10A-Center-...info/27846+TR/

Last edited by sam_sam_sam; 07-05-2020 at 01:56 PM..
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Old 05-04-2021, 06:02 AM   #15
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Default Re: ZD-985 desoldering station Power supply failure

Hi, here is a squematic of the P.S. that I draw with patience. That will help to understand an fix the ZD 985.
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