ZD-985 desoldering station Power supply failure

[sam_sam_sam]

sam_sam_sam What about the 5.1 ohm resistor?did you check it?

No I have not checked 5.1 ohm resistor yet I did manage to put back together the desoldering station that has the power saving mode feature and it seems to work okay but I think that there is something failing on the controller board because when it has been off for several hours and you turn it back on the temperature display flashing several different temperatures reading and then it settles down to the correct temperature reading it never uses to do this-this is something new

I have another controller that just like this one and I going to swap them around because this station has the hot air gun on the other side of soldering iron
which I do not use very often unless I am doing multiply layer board and I need the extra heat to unsolder a component

When you saying about using a laptop switching power supply any particular brand should I use it might be hard to find a 19 volt @ 12 amp laptop switching power supply I will look at EBay and see if I can find one and I will post the website link to it just let me know if you think it would work or not

If can not find anything wrong with the switching power supply that has the cycling power issue would you be willing to take a look at it and see if you can figure out what is wrong with it

I found this one do you think that it would have enough current capacity for the the soldering iron side of the station
do you think that it would have enough current capacity for the heater element and the vacuum pump plus the cooling

https://www.ebay.com/itm/25636685625...Bk9SR_bQ8aezYw

[CapLeaker]

sam_sam_sam
No I haven't tried this modification, but usually the PSU designs using that type of switcher in that package is garbage to me. But instead of using you MeanWell 24V power supply, I would hack in a 19V laptop PSU first and see how that works out. I am not sure why the low side MOSFET configured as a switch would blow feeding straight DC into it, because you see a lot of it in automotive doing the same thing and they don't blow that easily. So I am thinking the must be too much current drawn for that to happen. I think the next size up cap mod is fine, using 3330uF instead of 2200uF. 35V vs 25V wouldn't make any difference on the 18V rail, as long as you used quality caps. Some times using too low ESR caps may not be good either, but it should work here. What about the 5.1 ohm resistor?did you check it?

[stj]

for 35v caps i think panasonic FS series may fit

[sam_sam_sam]

[USER="38202"]Back to topic: Dod you try to compare the resistance of the primary winding between the good transformer and the bad one?

I did and it was not enough of a difference to make me think that this was the issue with it I even did it with the blue ESR capacitor tester which did not show any reals significant difference to make me think that this was the issue either now it does have a voltage reference ic chip that has several resistors around it

Now here is the weird thing about the soldering iron controller when I first got it it would somewhat overshoot the set point for the temperature that was set for and time when by it barely did enough to notice this after it has many hours of use which I probably have had it for at a couple of years by now / now that I recapped the switching power supply it back to overshooting the set point by +5*F and it undershooting it by 7*F after it has been on for a while it settles down little bit and the temperature swings are not as noticeable but even with it doing this you really don't it when soldering something with it

I did use 3300uf @ 25 volts capacitors instead of the 2200 @ 25 volt capacitors because I found when I did this on one of them that it worked better

I would have rather used 35 volt capacitors but the problem is the diameter of the 35 volt ones are too big to fit in the space that is a lotted between the switching transformer and the other components around the area because I tried to this once before

Yes you can cram them in into the space but then either the capacitor leads a lot longer than they need to be or the capacitors are too tall and the metal enclosure does not fit on it correctly

I figure that if it goes beyond 19 volts it probably going to fry the controller board anyway so what difference does that make when this happens it time for a new one

If I have some time later on today I will see if I can find the 24 volt switching power supply and do the major surgery and see if I can get it to work the way I describe earlier in this post this is going to be a proof of concept

I am not quite sure if this is going to work or not I am going to have to pay close attention to the temperature of the soldering iron when set to 390* F if stops at that temperature and it controlling it self with this modification of the power supply configuration

I am curious if you have tried this modification to a switching power supply device that have some type of issue with either the switcher or a switching power supply transformer that over heating because of a poor design I have tried once before and it would have worked if the battery charging controller was not so pick-e it would have worked just using the secondary side of the power supply so you can use the original controller portion of the device

But the brand of power tool that Harbor Freight has one of there brands has this issue with the switching power supply transformer overheating but when they made the dual battery pack charger with two USB charging ports I just add two small cooling fans and that solved this problem with the switching power supply transformer overheating and it charges the battery packs fairly fast

[CapLeaker]

sam_sam_sam
I did notice in that schematic that there are two 360 Ohms 2W loading resistors in parallel. Maybe one or both of these went bad? What happens if you put a little more load on the 18v supply by let's say using 150Ohms is parallel with a higher wattage reading?
I find I have a harder time replicating issues like this instance when something isn't working only when cold, I've got like at least 23C in my room. So if it doesn't clunk out at 23C, I'd have to freeze it or cool it down somehow. I've seen switchers go “lazy” after many hours of operation and turn intermittent, specially this style. Not sure what it is with this package this switcher is in, but I hate these with a passion. I also recall one instance that drove me crazy for a while on a specific PSU for a Nortel phone system. It turned on, worked for like 10 seconds and then dead. It used an UC3844 and to my amusement, it turned the problem being the PWM at the end. Usually they either work or don't work, but there is the chance of an odd ball and so far I only seen it once on the UC38xx family.
Back to topic: Dod you try to compare the resistance of the primary winding between the good transformer and the bad one?

[sam_sam_sam]

sam_sam_sam
Aah! There is a story behind all this! Guess what?! Out of all the tools and toys I got, I don't have a ring tester either! So far I've always done without, but I do have an oscilloscope. There are quite a few power supplies or other devices that do that cycling action after a lot of hours the item has been run, I haven't been always successful with repairing it either, but I did repair a few. Before you send it up here, that schematic on the first page is correct? This cycling problem is due to aged components? So when this thing is new it works perfectly, right?

Exactly this is the case and like you I have not figured out what is failing on these switching power supplies but on one of them that I do not have a switching power supply that works for I going to do major surgery on with a 24 volt switching power supply that is a Meanwell brand switching power supply with the voltage set to as close 18 volts that I can get and power applied to the secondary side of soldering switching supply board and see if I can get it working correctly or not to me there is a 50/50 percent chance that it will work perfectly fine doing this but I going to use an incandescent light bulb on the secondary side of the Meanwel switching power to the secondary side of switching secondary side of the soldering iron switching power supply board because I am really getting tired of these switching power supply failure and the way they fail if I can not figure out how to repair them or you are not able to figure out what is failing on these switching power supplies I going to do major surgery on the failing switching power supply boards

One note I do have a ring tester and it has helped in the past with some transformer but not all types of transformers so just because it shows that it is showing a short dose not necessarily a bad transformer but I have not figured out how you can tell if it is showing a short it is actually a short transformer that could explain why it either blowing fuses or just dose not function at all because the winding is open circuit

Do not get me wrong a ring tester is a very useful tool but it has its limitations and you have understand it limitations and what it is telling you about the transformer that you are trying to determine what is the issue with the device that you are trying to repair

I did this type of surgery on a battery charger that has issues with the switching transformer over heating in a switching power supply and it was successful the issue with it was that the controller is very picky about the voltage on the input voltage to the controller circuit and was not reliable enough for me to use it without watching the hole time it was changing a battery pack and this why I made the comment that there is a 50/50 percent chance that it would work correctly

I have made these soldering desoldering stations work on dc voltage the issue you have is that the mosfet does not like straight dc voltage because it blew mosfet but if I have a work around for that it is to use a mosfet board made for 3D printing heater elements which works but it somewhat over shoot the temperature setting but if you use PWM controller with the 3D mosfet board it works very well but it is a lot more hardware that is needed to make it work correctly

[CapLeaker]

sam_sam_sam
Aah! There is a story behind all this! Guess what?! Out of all the tools and toys I got, I don't have a ring tester either! So far I've always done without, but I do have an oscilloscope. There are quite a few power supplies or other devices that do that cycling action after a lot of hours the item has been run, I haven't been always successful with repairing it either, but I did repair a few. Before you send it up here, that schematic on the first page is correct? This cycling problem is due to aged components? So when this thing is new it works perfectly, right?

[sam_sam_sam]

sam_sam_sam
Sorry Sam, but I just couldn't resist posting it... I tried…
The switcher either works or it doesn't. So either it's a cap issue, a bad solder joint, something wrong with the feedback. When that iron clunks out, does the display go out too?

Yes it does for about a second and then restarts again for about a second and just keeps restarting but if it a lot warmer like in the afternoon it will start normally I change the two 10uf@50 volt capacitors which did not change anything that it was doing so I am confused about about exactly what wrong with this switching power supply and yes the new capacitors were checked with a ESR meter before they were installed

When I had another one of these switching power supply for the desoldering gun station did kind-a nonsense I first replaced the two @10uf@50 volt capacitors and the same thing when it was cooler weather it did the same thing so I replaced the switcher and it was better but when it got cooler it would do the same thing but when it got warmer it would not power cycling anymore so you when someone on the forum had there ZD-915 desoldering station switching power supply the switcher blew up he sent it to me I tried to to repair his switching power supply board so I removed his switching power supply transformer and installed the one I from a switching power supply for a ZD-915 desoldering station power supply that had the cycling issue when it was cooler weather and when I powered it on it blew the switcher so I installed another one and this time it kept blowing the fuse when powering the screen would briefly come on and would right back off and blow the fuse again now with the light bulb trick it would power on and stay on with out the gun hooked up it did not make a difference weather or not the gun was hooked up or not it would blow the fuse

That is the reason I have come to the conclusion that there must be some kind-a issue with the switching transformer you can not accurately determine whether or not a switching transformer is shorted with a ring tester because I did on a good switching transformer and got the same exact results so I do not trust the ring tester to tell me the hole story about weather or not a switching transformer is good or not

So if you can shed some light on what you think about what could be going I would really appreciate any suggestions you have

I do not own or have access to a scope so I can not troubleshoot it the way that it needs to be done

If you are interested in figuring out exactly what going on with this switching power supply I can ship you the hole unit
It would have a normal controller board that does not have the sleep feature on it because they are harder to get because they are only in a certain versions that they made and I prefer this version because I like I mentioned earlier I do not continuity use the hole time that I have it turned on

On this desoldering iron the switcher has not been replaced yet I only have changed the two 10uf@50 volt capacitors near the switcher and one other capacitor that if I remember correctly is a 100uf@35 volt capacitor that did not test bad but I changed it because I have one to replace it with

If you are interested in doing this please just PM me and we can discuss the details about you trying to figure out what is going on with this switching power supply because I would really like to know exactly what is going on with this switching power supply because after they have a lot of running hours on them they start having these issues with the cycling power supply on and off usually just recapping the switching power supply board solves the issue but not always

I am in the process of reconditioning this desoldering gun / soldering iron station with a vacuum pump that does not have very many hours on it including both switching power supplies so it will be almost new again these two switching power supplies are getting a full recapping except the main filtering capacitor which I do have one in my part bin and do not want to order anything at this time

One note on this switching power supply board there are no capacitors near the optic sensor so unless something changes value which I can check on the newer board but I have to do this when the switching power supply board is acting up because this is the only way to figure out exactly what going on with it

[CapLeaker]

sam_sam_sam
Sorry Sam, but I just couldn't resist posting it... I tried…
The switcher either works or it doesn't. So either it's a cap issue, a bad solder joint, something wrong with the feedback. When that iron clunks out, does the display go out too?

[sam_sam_sam]

Ouch! That sux balls!
https://www.youtube.com/watch?v=4a-ohLwa6cs

This was hilarious funny but doses not have anything to do with issue at to why this switching power is cycling when it is cooler weather in the morning unless the switcher has gremlin in and they can not figure the way out to let the factory smoke out

[CapLeaker]

Ouch! That sux balls!
https://www.youtube.com/watch?v=4a-ohLwa6cs

[sam_sam_sam]

It's good you caught the 10uF cap dying before the IC blows. That ESR was really bad.
Is this the fish tank pump they use, AC solenoid with magnet flipping the diaphragm?
I would lube the cooling fan, I use a tiny bit of 10W20.

Unfortunately I might not have caught it earlier enough because this morning it rather cool and it is power cycling again so it might have damaged the switcher so I have to order some and replace it and see if this fixes the issue with it cycling I had one that was doing and after replacing the switcher it keep doing it and I came to the conclusion that it was the switching transformer because when I transplanted the switching transformer it blew the switcher which I was not expecting that to happen

[stj]

maybe this is a good time to remind people to fit an extra inline filter

[sam_sam_sam]

It's good you caught the 10uF cap dying before the IC blows. That ESR was really bad.
Is this the fish tank pump they use, AC solenoid with magnet flipping the diaphragm?
I would lube the cooling fan, I use a tiny bit of 10W20.

No the cooling fan is going to be replaced with a 24 volt version instead of the 12 volt one that is in there now and the resistors remove
The Vacuum pump is a 12 or 18 volt pump motor the issue with the pump is the residue that builds up because of use you basically carefully removing the pump cylinder rubber cups and clean the metal disc and lightly re-oil the cylinder and carefully reinstall the rubber cups with the retaining clip and then the pump has more suction but I going to instead reconditioned the pump and put in my other desoldering station that I do not use very much because it does not have the tilt switch function on it which is very important thing to have when you use it for a few minutes and then you are getting other things ready to be repaired so you do not prematurely wear out the tip of the soldering iron

Plus there seems to be a slight issue with the switching power supply when I partially recap it power cycle once but it also seems to have a slight issue with the temperature sensor causing it to flicker the temperature reading when you first turn it on I have not seen this issue before I am not sure what this is all about so I have another controller board that has this function that I do not use very often because it has the heat gun feature on the other side of the soldering iron so only when I have to use the hot air gun is when I use this version one I can deal with when I need use it off and on I did do a modification to this soldering iron / hot air gun because I do not understand why when they made this hot air gun that they did not have a cool down mode on it I add this feature to it with a light above the switch that the LED light comes on when it is the cool down mode I will post a picture of it when I finish restoring it back to it original functionality and can use it without being aggregated using it because of very low suction and power cycling and just misbehaving and throwing a temper tandem because it tired of being used

I guess I need to recap the other switching power supplies that are for these desoldering / iron / hot air gun systems before I have a major meltdown because of bad capacitors unfortunately these switching power supplies are not very easily done because of all of the metal enclosure covers that you have to remove and reinstall and all of the screws that hold these things together

[redwire]

It's good you caught the 10uF cap dying before the IC blows. That ESR was really bad.
Is this the fish tank pump they use, AC solenoid with magnet flipping the diaphragm?
I would lube the cooling fan, I use a tiny bit of 10W20.

[sam_sam_sam]

So far I have gotten many hours of use before I start having issues with the switching power supply but I have recap the one I am currently using because I have seen it power cycle a few times when it is cooler outside which it has not done this before

This might happen this weekend if I find some spare time to get this done

Well I took apart the desoldering station the soldering iron side which was the side that was cycling a few times before it stay on the two 10uf@50 volt capacitors extremely bad ESR reading was 5.50 this is not a misprint a new one is 0.48 to 0.51 so way off I am surprised that it was turning on and running when it did run

But unfortunately this not the only issue the vacuum pump has some issues because it does not have very much suction like it did new the cooling fan sounds like shit when you first turn it on it might get some newer parts from one that dose not go to sleep after a certain period of time has passed which is the version that I use the most

I might have some time to tomorrow to work on it and get it up and running again in better condition than what it is currently

[redwire]

There's a chance the power supply is not a great design. It's a current-mode controller which shouldn't care if the output is overloaded or not. Abnormal overcurrent protection- the IC shuts off and stays off.

The tuning cap across the mosfet D-S, the SYNC pin resistor/capacitor values might not be correct for the quasi-resonant mode it is supposed to run in.
A ferrite bead is used on IC pin 1 but not sure if the ZD-985 has that.
The IC is good for 200W but it's either counterfeit IC's or the circuit design might be a bit off.

Fairchild FSCQ1565RT
There was a lot of patent litigation between Fairchild and Power Integrations so they had to make IC's a bit weird and complicated, and designing them in is difficult.

[sam_sam_sam]

When a switcher IC blows, it is common for other parts connected to it to get damaged. They can see DC bus voltage until kabang. Check all the resistors, the SYNC pin parts etc.
The 10uF 50V cap is critical and will cause the IC to blow up under heavy load, if the cap goes low value/high ESR.

So should the start capacitor or the main filtering capacitor be a slight higher value or what is the solution for this issue if the switcher is that sensitive voltage spikes or heavy loads because when you run the vacuum pump you are current surging every time you turn on and off the pump

The only other solution is get a Mean-well switching power supply or a Delta switching power supply and modify it for this desoldering station which could be done the only issue is the -5.00 volt power rail which is kind-a weird the way this power rail is done in this device and you would have to carefully remove the control circuit to control the heating element for the gun and if I remember correctly it also has the control circuit for vacuum pump as well which could be done but not very easily

So far I have gotten many hours of use before I start having issues with the switching power supply but I have recap the one I am currently using because I have seen it power cycle a few times when it is cooler outside which it has not done this before

This might happen this weekend if I find some spare time to get this done

[CapLeaker]

When a switcher IC blows, it is common for other parts connected to it to get damaged. They can see DC bus voltage until kabang. Check all the resistors, the SYNC pin parts etc.
The 10uF 50V cap is critical and will cause the IC to blow up under heavy load, if the cap goes low value/high ESR.

Agreed, but this package is very sensitive to dirt, residue, moisture etc. It's literally the worst package I've seen for a switcher to be in. The pins are just too close together. stj comment using some RTV that doesn't smell like vinegar, is a good idea as well. These type of switcher package likes either to blow up or play dead. Waaay more so than any other package.

[redwire]

When a switcher IC blows, it is common for other parts connected to it to get damaged. They can see DC bus voltage until kabang. Check all the resistors, the SYNC pin parts etc.
The 10uF 50V cap is critical and will cause the IC to blow up under heavy load, if the cap goes low value/high ESR.