UYUE 8586 : Wot no hot air?

[NivagSwerdna]

About 10 years ago I watched some aussie bloke review a Rigol 1052T scope and got back into hobby electronics...

... anyway I bought a cheapo UYUE 8586 generic Hot Air and Solder Station...



Anyway... Recently I find I don't have hot air... So the obvious conclusion is that the heater element is blown...   

So I bought a replacement hot air wand... and same error...

I disassembled the original and measure 70 ohms at the element....

So this makes me think maybe my problem is in the box.

Has anyone taken one of these apart... how does the element get driven?

Not economically repairable?  Any suggestions on contempoary devices?

One thing I did like about it was the relatively small form factor to fit on my cramped desk.

Suggestions welcome.

[Chris56000]

. . .Did you get an exact replacement hot–air tool with the correct plug fitted or just the element?

. . .The indication "S–E" (it IS meant to be a capital "S", NOT the figure "5") indicates either the element is the incorrect type, or the thermocouple sensing element, which is part of the heater element itself, is faulty!

. . . Unfortunately the pinout and wiring of these hot–air stations seems to vary between one model no. and another and you would need to know where the heater element and thermocouple element connect internally to the control PCB inside the base unit, and trying to work it out is not a gratifying experience – I've had 48 years in electronics and these things are still a pain in the proverbial – I usually buy a new hot–air.tool and base together new as a pair!

Chris Williams

[Chris56000]

. .  Basically they're a microcontroller connected to the thermocouple sensing element via a simple op–amp amplifier circuit and an a/d converter, part of the main controller i.c. Itself, when then controls the heater element in the tool via an ooto–isolator, to isolate the base from the mains, and then to a triac driver that controls the conducting time of a triac connected in series with the heating element itself!

.   .There will also be a small switch–mode power supply in the base unit, providing one output for the control electronics, and another power supply feeding the air–blower in the tool via a low voltage control circuit!

. . .These units, and the wiring to the hot–air tools themselves, seem to vary from one model of unit to another as I said in my previous note, and buying them as a known working pair is the only way forward with them!

Chris Williams

[thm_w]

Sensor Error

Can be from the cable connections breaking at the handle or plug end. Measure from the plug, you said the element was 70 ohms, then the sensor pin should be <2 ohm or so, as its a thermocouple.

[stj]

the sensor feeds into an opamp inside the unit.

[NivagSwerdna]

Interesting...

When I remove the handle from the holder... the fan starts and the display changes from the set temperature to 000 and no heat is supplied.  After a while it changes to S-E and locks out.

Given that I am not at 0C maybe indeed this does suggest sensor rather than element?

When I get time I will check continuity first and compare the two devices I have

The sensor in the handset... A thermocouple?  So I could probably test that?

[Chris56000]

. . .You can test the Thermocouple Sensor element yourself with a multimeter switched to the low millivolts d.c. range and another heat–source, a soldering–iron laid on the heater barrel might work,  but the soldering iron wouldn't supply very much heat, as an alternative you can try a paint stripping hot–air gun (take care not to melt anything else doing so tho'!), whilst connecting the millivolt meter across the sensor leads – you should see a small increase in voltage as the heater barrel of the hot–air tool gets hotter!

. . .If you do get a change in voltage (it will only be very small!) then it's possible the thermocouple sensor may have been connected to the control PCB reverse polarity, not unknown in Chinese assembled units, and reversing the reads could solve the problem!

. . .If no difference, replace the sensor leads the original polarity if you tried reversing them – it might be worth repeating the thermocouple test I detailed above with your original tool that came with your station to verify both are giving a thermocouple voltage output!

. . .Another simple trick you can try is to make up a circuit consisting of a 1k 20 turn preset across a 9 V battery, connect the outer ends of the pot. to the battery and run two leads from the potentiometer wiper (middle pin) and battery negative, test with your millivoltmeter to set the pot to give 10 mV between wiper and battery negative, them connect these leads to the sensor terminals of the PCB with no hot–air tool plugged into the base OR the sensor leads from the socket disconnected (the thermocouple would short–circuit the test voltage otherwise!) – you can then turn the base station on and see if adjusting the test voltage pot. makes any difference to the display – if not you have a control fault within the PCB itself!

. . .If you find the Control PCB is not responding to a change in voltage from the tool, either by heating the hot–air tool barrel or by means of the test circuit I described above, please post good clear photos of the control PCB and we can suggest what else to check!

. . .It might also be worth using "Google Lens" with a photo of the PCB, you might find a new spare one of the same type on AliExpress or eBay!

Chris Williams

PS!

. . .Try a search for "858 Hot Air station" on Google or AliExpress – you might find that the "858" is the same base unit and hot–air tool, the Chinese sell these things under a multitude of brand–names and model numbers, and search this Forum as well – another Member might have drawn one out or posted a case history of a repaired one!

PPS!

Any help?

https://blog.enbewe.de/posts/2018-06-21-saike-858d-original-schematic/

[stj]

i have several schematics, but not for that variant.
the closest i have is a unit with 2 displays - one for the iron, and a single mcu - not just 2 indentical circuits.

[stj]

incidentally,
70ohms sounds very high for a 700w heater

[Hamelec]

No

P=U*U/R

[NivagSwerdna]

OK.. First the Handset wiring...



I think the hot air wand is probably fine...

Between 7 and 8 I get 70 ohms

The thermo-couple is between 1 and 2... Measures 0.5 Ohms... feels a bit low... almost a dead short...  But it does seem to change with me warming up the wand.

[NivagSwerdna]

PCB...



So there is a slight whiff of things that have got hot at the top left... this is a BTA12

Otherwise... it's a bit hard to see...

[NivagSwerdna]

Looking through the jungle of wires...



24C02 is an EEPROM so presumeably for settings/calibration

The more interesting device is HA17358 which I think is a LM358 equivalent... i.e dual op amp.

It's nicely socketed.

[NivagSwerdna]

Looking at the top Left..



I see a OP07CP... so another op-amp.

The device on the far left I'm going to guess is an Opto Coupler...

uP in the middle...

Plan of attack... Get the TRIAC out and test... then test the LM358...  I don't currently have spares for either of them so a quick pre-emptive order.

[Chris56000]

Thank you for the photos!

You can check on pins 4 and 8 of the HA17358/LM358 and pins 4 and 7 of the OP–07 to make sure these op–amp devices are in receipt of their power supplies –pin 4 is –ve for both devices and pin 8 of the '358 is +ve, whereas the OP–07 is a single op–amp with the power supply +ve on pin 7.

If there is no negative readings the board designer could have used a "single–supply" implementation of his circuit, in which case there will be a "mid–point" reference somewhere – I did notice "8V2" silk–screened on the PCB with an arrow pointing to a surface–mount diode –check this voltage is present and correct!

If the supplies test OK begin with pins 1 and 7 of the '358 (outputs) and see if there is a change in voltage on either of these pins when you heat the hot–air barrel – no change could indicate the '358 is not responding to the thermocouple voltage, and you would need to check all the PCB back to pins 2 and 3 of the hot–air tool socket!

(I'm afraid the writing in your sketch is almost impossible for me to read!)

It is very unlikely indeed that the microcontroller has failed – it gives "000" on the display before the "S–E" Sensor Error, and as the display is one of those 12–pin internally multiplexed silly things sold for Arduinos, etc, all the segment driver pins from the M.C. are in good order, as "000" and "S–E" tests all of them!

Chris Williams

[stj]

0.5 ohms is fine for the thermocouple,
infact it's probably lower and your seeing your cable resistance.

it generates a voltage based on temperature, set your meter to mV and meter it while you heat it up or cool it down.
it's probably a "K" type.

[stj]

*this* looks really close!

[Chris56000]

The schematic posted by Member "stj" is of very great assistance as it provides the thermoelectric voltages to expect from the hot–air tool, which you can trace thro' the OP07 to the appropriate pin of the M.C.U., however it's possible the M.C.U. used on your 878D board could be different – I can't make out any number on yours – the Chinese may have sanded it off!

The main difference between the 856D board and the 878D board in your unit is that your board combines an 936 soldering iron controller with a manually set front panel control and the 856D hot–air controller with a temperature display and up/down set buttons, no one appears to have drawn out any of the combined boards tho!

(The HA17358 will almost certainly be the amplifier for the soldering iron sensor thermocouple as this, being a simple marked front panel control, doesn't require the more accurate and expensive OP–07 device!)

You should be able to locate your fault from the thermoelectric voltage indications given on the 856D circuit diagram now!

Chris Williams

[NivagSwerdna]

Wow... I'm glad I checked back... That schematic looks good...



I was tracing SE+ which is from the Thermo-couple so this does indeed seem to go up to the OP07C, which TBH was a bit surprising since I found a different schematic that went to the LM358...

I removed both op-amps and put them in my cheapo flashing light AliExpress OpAmp tester... and the lights flash.

Could the sensing be a red herring and the heater Triac is just broken?

[floobydust]

Are you sure SE+ trace goes across the PCB like that?
I think the op-amps are mixed up? The bottom one next to trimpot is for the thermocouple and should be OP-07, I think.
The other is probably for the fan control.

[NivagSwerdna]

Pretty confident... Yellow TOP trace, BLUE under...



There is a trim pot on the underside which is accessible through the front panel. (Tripod arrangement pins below OP07C)

The trim pot at the bottom is inside the unit and not adjustable by mortals.

[stj]

is the soldering o.k.?
and the socket?

[NivagSwerdna]

The soldering works, the display works, the fan works,,,

I'm awaiting a Triac and will replace,,, probably also the opto for good measure and then will retest

[ondraN]

Also check the resistor across which the optodiack is connected in the optocoupler. This is a more likely cause of the fault than the triack (usually breaks down and is still conducting) or the optodiack.

[stj]

if you want to test if a triac is working at full voltage then just connect a neon or led with a 470k resistor across the output.