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Old 31st Jul 2020, 8:42 am   #1
Alan's MagicEye
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Default ZD-915 Desolder station power supplies

I have a clone ZD 915 desolder station which has suffered an explosive failure of the switch mode power supply. On examination I found that the 5 leg power switch chip had blown apart. Here is the data sheet:
https://www.mouser.com/datasheet/2/1...65RT-83559.pdf

I found a replacement from RS. Having checked all of the electrolytic capacitors and snubber caps as well as the mosfets I replaced the chip but the unit did not power up (carefully using my dim bulb tester of course) and there is no control voltage on the VCC leg of the chip although the high voltage is present on the drain leg.

I have decided to investigate the possibility of replacing the SMPS with linear transformers and rectification/ voltage regulation as I feel this would be more reliable and an experiment with a couple of bench power supplies got the unit up an running apart from the temperature control of the desoldering gun. I'm assuming that there should be some kind of PWM control for this function?

Has anyone successfully done this kind of conversion?

Alternatively has anyone successfully repaired this kind of fault on the existing power supply?


Thanks very much

Alan

Last edited by Alan's MagicEye; 31st Jul 2020 at 8:48 am.
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Old 31st Jul 2020, 9:14 am   #2
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Default Re: ZD 985 Desolder station power supplies

probably not worth building a linear supply for this, they're 80W aren't they? The parts alone would be near to the cost of a new one by the time you've put it in a suitable enclosure.

I'd treat yourself to a new one! I've had 2 over the years, the first one was replaced because the pump diaphragms tore. TBH I dont think the overall quality warrants spending much on them.

Mine both came from CPC off the special offer sheets.
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Old 31st Jul 2020, 9:22 am   #3
Alan's MagicEye
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Default Re: ZD 985 Desolder station power supplies

Thanks Kevin

I've only had mine for about 6 months and only used it for a few hours, but I take your point.

I have some spare transformers so I thought it may be worth fiddling with��

By the way, I posted this as model ZD 985 when it should have been ZD 915, I've messaged our administrator to see if the title can be amended......

All the best

Alan
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Old 31st Jul 2020, 6:24 pm   #4
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Default Re: ZD-915 Desolder station power supplies

The datasheet you provided shows that the Vcc pin needs to reach 15 volts for the chip to startup. The example circuit fig. 25 on page 13 shows the usual resistor and capacitor from the bridge. I have found that the SMPS startup capacitor is often a low value and has failed.
That should not have caused an exploded chip though - just a failed start.
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Old 31st Jul 2020, 6:45 pm   #5
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Default Re: ZD-915 Desolder station power supplies

Maybe the resistor is open circuit from the AC in to the Vcc pin?
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Old 31st Jul 2020, 10:32 pm   #6
Alan's MagicEye
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Default Re: ZD-915 Desolder station power supplies

Thank You Buggies and Wave Solder for your replies.

I will carefully check the board again, I have studied it fairly intently already but cannot find a schematic.

However, my course of action has veered off of the repair of the board; I have found that the temperature sensor in the gun is a K type thermocouple, which I feel is good news. I have ordered a PID temperature controller and SSR at a very reasonable price and fast delivery. My plan now is to utilise the desolder gun but to dispense with the controller entirely. I have some wrecked Weller soldering stations with decent transformers and although they are of a lower wattage I may be able to use two in parallel to provide heating current for the gun. I also have a more powerful vacuum pump so I plan to use this in place of the not very effective one in the old station.

All the best

Alan
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Old 14th Aug 2020, 6:12 pm   #7
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Default Re: ZD-915 Desolder station power supplies

Hi!

Hang on to the remains for a day or two longer as I have a working unit and get a circuit diagram & parts list drawn up over the weekend, as I'll want the info for my T & M book now in the course of writing !

Chris Williams
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Old 14th Aug 2020, 7:32 pm   #8
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Default Re: ZD-915 Desolder station power supplies

Hello Chris

Wow, that's very kind, even if you intend to use the info yourself!

I have kept all of the bits so maybe I'll have a new home brew desoldering rig and a backup Chinese one.

Thank you so much.

Alan
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Old 14th Aug 2020, 8:17 pm   #9
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Default Re: ZD-915 Desolder station power supplies

PS!

I have since ordered a dual 100W 5V 1A & 12V 8A power supply module to upgrade my unit to get rid of the resistor dropper box, etc., that limits the vacuum pump and fan motor performance, so if you want my original unit after I've completed my diagram, pm me a safe postal address and I'll post it to you for the cost of the postage – it is about six months old but still in working order!

(The conversion details will also be featured in the appropriate chapter of my T & M book!)

Chris Williams
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Old 14th Aug 2020, 9:06 pm   #10
Alan's MagicEye
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Default Re: ZD-915 Desolder station power supplies

Thanks Chris

PM sent......

Alan
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Old 15th Aug 2020, 9:57 am   #11
Alan's MagicEye
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Default Re: ZD-915 Desolder station power supplies

Hello again Chris

I just had another, possibility important thought after reading your post again regarding the purchase of a replacement dual power supply for your station.

I'm unsure if you checked the actual wattage of your desolder gun? Although mine was marked up at 80 Watts, when I measured the power the gun was consuming it was close to 120w (10A) at the rated voltage! It may be worth investigating if you haven't done so already as I note that the power supply which you ordered would seem a bit marginal at 96 Watts (12V, 8A) if your gun is similar.

This may also be why the original power supply does not last very long if it is only rated for 80w!

All the best

Alan

Last edited by Alan's MagicEye; 15th Aug 2020 at 9:59 am. Reason: Additional info.
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Old 15th Aug 2020, 11:08 am   #12
Alan's MagicEye
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Default Re: ZD-915 Desolder station power supplies

I have just been to my "Lab" to check things over since my last post......

The marking on the gun is "24V 80W". Since mine is drawing 120W at 12V, I'm wondering if the element is shorted...

This may be the cause of all of my problems:-(

Alan
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Old 19th Aug 2020, 9:53 pm   #13
Ted Kendall
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Default Re: ZD-915 Desolder station power supplies

Rotten things anyway. I chucked mine back for a refund. Bismuth and braid for me...
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Old 24th Aug 2020, 4:52 pm   #14
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Default Re: ZD-915 Desolder station power supplies

Hi!

I had to send for a replacement heater element for mine because it got blocked with something & I hadn't a long enough very fine drill to drill it out!

I'll test it on the large bench power supply at work and report back what the correct current drawn is!

Chris Williams
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Old 24th Aug 2020, 10:50 pm   #15
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Default Re: ZD-915 Desolder station power supplies

Mime is going strong for months. I cannot live without it. I must say it is one of the most useful tool I bought if it lasts...I hate using desoldering braids or hand pump.
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Old 24th Aug 2020, 10:59 pm   #16
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Default Re: ZD-915 Desolder station power supplies

Ouf of idle curiosity I tried mine today. When you first turn it on, the power consumption is 10W. When the heater kicks in, it ramps to 80W for about 20 seconds then ramps to 120W. Once it's up to temperature it regulates the power on approach then switches off, back to 10W indicated.
This is in the primary side, of course, simple wattmeter.
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Old 28th Sep 2020, 12:04 am   #17
Chris55000
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Default Re: ZD-915 Desolder station power supplies

Hi!

Update on my project – I've got an alternative PSU and opto–coupled thyristor AC Switch Module to see if they will replace the original failure–prone design of PSU, but I've not received the replacement heater element for the gun yet, and I can't remove some parts from my PSU to document it until my new heater arrives, unless anyone can provide a link to buy the original PSU/heater control module!

Chris Williams
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