Hakko 470 with 809 gun de-soldering station

[smilan]

Hi, I have a Hakko 470 with 809 gun de-soldering station.
The heating element stop to heat.
I'm trying to troubleshoot this issue and to determine if the problem coming from the heating element or from the electronic circuit.
When I disconnected the heating element I measured 3.7 ACV between the wires that connecting the heater element to the gun (black to white) and 8.3ACV between the black wire to ground (green wire).
I don't sure if I should expect to measure there 24V or there's some regulation that reduce the voltage when there are no resistance between the two wires?
The DC resistance on the disconnected heating element is 3 Ohm.
 What else I can check to determine if the problem coming from the heating element or from the electronic circuit?

Also one of the wires of the heating element has disconnected, what is the way to solder it back? It seems like a normal soldering station doesn't have enough heat to solder it back.

[floobydust]

You should measure 24VAC at the heater terminals. Check the board's power supply voltages +8VDC, -9VDC are there.
The heater element's wire is kanthal or nichrome I forgot but think it can't be soldered to, have to use a crimp?

I drew a Hakko 470-2 schematic Hakko 470, 471 de-soldering station repair and schematic

[smilan]

Thanks, your schematic really helping.
I measured 20V at VD1 (this is the right voltage) and -3V instead of +12VDC.
+8 and -9 VDC measured right.
What can cause the +12V voltage to fail?

Before when I tested the ACV on the wires going to the heating element I tested the voltage in respect to chassis ground instead to COM.
Now on the black wire I measured 26 VAC and 2.5 VAC on the white wire.
* all voltages measured with no heating element connected.

[floobydust]

It's a bit of a confusing power supply.
+12VDC rail cannot go -ve unless zener TD2 is open circuit. What do you measure across the zener?
The 12V is for the vacuum pump motor triac opto and solenoid valve control and timing IC's only. I think the heater controller doesn't use the 12V rail.
But with no 12V you will not turn the pump motor on either. One of the IC's might be shorted, 555 or CD4584.

[smilan]

Thanks for your patience.
Yes, it's a bit confusing, some voltages measuring with respect to ground while others with respect to com.
I've measured 11.87 DCV across TD2 and the pump working, so the +12V rail is OK.
The only weird measuring is the 3.7 ACV between the wires that connecting the heating element to the gun (black and white on the schematic).
The voltage between the black wire to com (the side of R6 that doesn't connected to the TRIAC) is 26.5 ACV (with no load) so I guess this is the right voltage?
The voltage on the white wire with respect to com is 2.6 ACV.

[floobydust]

With your readings, you can't tell if the triac is on because it switches the low side and the uPC1701 is driving it with AC.
You can use a resistor for a dummy load, in place of the heating element. A few kohms or something that does not get too hot.
Or add the heat-on LED on the schematic.

[smilan]

I've tried it both ways, with a 15Kohns resistor across the black and white wires the voltage across the resistor is 0V and the voltage between the black wire (+24V) to com is 26.5 ACV
When the LEDs circuit added non of the LEDs turn on.
I've tested this circuit with an external DC PSU and both LEDs turning on when current passing thru.
It seems like no current flows from the triac  to R6.

 How I can test the triac and uPC1701 to find the faulty component?

[floobydust]

Check the uPC1701 control input pin 4 voltage, to see if the rest of the circuit is trying to turn it on.
It needs to go below I think -4.3V as pin 3+1 are at -4.3V and just post what you measure at all the IC's pins.
With multimeter(-) on COM, you should see around +8V pin 4, -9V at pin 11 of quad op-amp U9 LM324.
U9B pin 7 should be low -ve,  U9C pin 8 should be oscillating at 2.5Hz narrow pulse.

If you shorted the heater connections the triac might be dead or R6 open-circuit 0R15 2W?

[smilan]

Check the uPC1701 control input pin 4 voltage, to see if the rest of the circuit is trying to turn it on.
It needs to go below I think -4.3V as pin 3+1 are at -4.3V and just post what you measure at all the IC's pins.

All measurements took with the multimeter(-) on COM.
UPC1701
1+3 -4.35V
2 -5.2 to -5.8V
4 -5.9V
5 -8.93V
6 0
7 0
8 +0.545

With multimeter(-) on COM, you should see around +8V pin 4, -9V at pin 11 of quad op-amp U9 LM324.
U9B pin 7 should be low -ve,  U9C pin 8 should be oscillating at 2.5Hz narrow pulse.

C324C
1 0
2 0
3 0
4 +7.8V
5 0
6 0
7 -0.768V
8 +4.7 to 6.5V
9 0 TO +1.7V
10 +2.8 to 3.2V
11 -8.94V
12 0 to 1.4V
13 0 to 1.4V
14 -8.94V

The frequency at pin 8 is 50Hz (if I measuring right)
https://i.ibb.co/X5t3GMX/212511162-501196500937524-5088425772306245434-n.jpg

If you shorted the heater connections the triac might be dead or R6 open-circuit 0R15 2W?

R6 measured 0R22 Ohm.

Here are the measurements from all the other ICs:

UPC1555
1 -14.9V
2 -3.28V
3 -14.9V
4 -3.3V
5 -7.15V
6 -174.9V
7 -14.9
8 -3.3V

D4584C
1 -14.5V
2 -3.3V
3 -3.3V
4 -14.7V
5 -13.7V
6 -3.3V
7 -14.7V
8 -14.6V
9 -3.3V
10 -3.3V
11 -14.4V
12 -14.4V
13 -3.3V
14 -3.3V

TLP561
1 -2.2V
2 +1.6V
3 0
4 0
(5) +9V
6 0

[floobydust]

The uPC1701 appears to be off, no output at pin 6 to turn on the triac. But control input pin 4 is more negative than pin 3, which I believe requests heat. Higher+ voltage on pin 4 turns off the triac, I think there's an inverter in the IC. So the 1701 might not be doing anything?    It's difficult because the IC datasheet is in Japanese. Thanks for all the voltage readings.

A few other signals look wrong too.
The signal at U9 uPC324 pin 8 oscillator should be a nice 2.5Hz narrow pulse. No sine wave.
The signal at U9 uPC324 pin 1 should be a small sine wave, the setpoint pot is driven by 24VAC not DC.
The signal at U9 uPC324 pin 7 should be a square wave. Pin 5 should be up a bit at 0.163V not 0V.

[smilan]

The uPC1701 appears to be off, no output at pin 6 to turn on the triac. But control input pin 4 is more negative than pin 3, which I believe requests heat. Higher+ voltage on pin 4 turns off the triac, I think there's an inverter in the IC. So the 1701 might not be doing anything?    It's difficult because the IC datasheet is in Japanese. Thanks for all the voltage readings.

Pin 4 of the 1701 is connected to -9V via R16 (75k).
The voltage drop across R16 is around 3V.
If I'll increase the value of R16 to 150K the voltage drop should be around 6V so pin 4 will become more positive than pin 3.
Do you think it's worth to try this experiment?
Also when I connected the scope to pin 6 this is what I saw:


It seems like there's some pulse coming from pin 6.
This is what I want to see at pin 6?

A few other signals look wrong too.
The signal at U9 uPC324 pin 8 oscillator should be a nice 2.5Hz narrow pulse. No sine wave.
The signal at U9 uPC324 pin 1 should be a small sine wave, the setpoint pot is driven by 24VAC not DC.
The signal at U9 uPC324 pin 7 should be a square wave. Pin 5 should be up a bit at 0.163V not 0V.

At pin 1 there's a sine wave, at pin 7 there's a square wave, at pin 8 there's a 50 Hz half sine half triangle wave.
I made this short video of the waves as seen at my scope:
https://youtu.be/0O_O5lcVkOU
I took another measurement at pin 5 and indeed there's 159 mV over there.

Does those measurements pointing on the faulty IC?
I can order new 324 and new 1701 ICs and test the circuit again.
 

[floobydust]

The signals look fine  With the scope AC-coupled it can be hard to tell what the voltages are.

The heating element resistance goes up with temperature. Around 2.8R cold to over 8R hot.
With no heating element present, there is no heater current (voltage across sense resistor R6) so the controller thinks the heater is very hot, and it goes to minimum heat. This is the short 2.5Hz blip you see at uPC1701 pin 6- the triac is turned on only for a very short time. Does that make sense? I forgot it's a trap with this soldering station.

So the triac should be turning on just for a little time (few cycles at every 2.5Hz) because there is gate-drive at uPC1701 pin 6.
If you put a dummy load resistor as the heater, and scope triac MT2/the white wire, you should see something happening.
Now I would say your triac is not doing anything or there is an open-circuit in the wiring/connector/gun to the heating element, if you are getting no heat at all.

I get different scope signals at LM324 pin 8 though.

[smilan]

While looking at the triac MT2/the white wire with a 7.6 Ohm dummy load resistor I've measured a 30V / 50 Hz sine wave.
Then I replace the 7R6 resistor with a 4R2 and a 2R8 resistors and got the same reading.
https://youtu.be/3VoRiqz_03Q

With no load there's a 2.2V / 50 Hz distorted sine wave.
https://youtu.be/7tSXhUdQq3U

Is it OK that there are no changes at this point with different load resistance?
It might be a matter of  trimmers calibration?



 

[floobydust]

Did the dummy load resistors get hot? They should, especially reading 30VAC with 7R6... 75W!
The temperature dial should have an effect.

[smilan]

No, no current passing thru the 7R6 resistor.
I've measured 26 ACV between each side of the 7R6 resistor to COM, but there is no voltage drop across the resistor.
The temperature dial have no effect.
It seems like the triac doesn't allow any current to flow thru R6 to COM.

[floobydust]

I was wondering if the triac was turning on. uPC1701 pin 6 triac drive output had pulses- which should be turning it on.
Can you test the triac and check R5 300R is not open.

[smilan]

I've tested the triac by using this method (while the triac was connected to the PCB):
https://instrumentationtools.com/test-triac-multimeter/
It seems like it working good.
Maybe with higher voltages it fails?

Another test I mead was to look at each leg of the triac with a scope.
The 26V/50hz sine wave was measured only at T2. At the gate and T1 I saw this pulses:
https://youtu.be/ALQIeoXB9AI

R5 is 294R so it's good.

[perieanuo]

hi,
just some advice: with high loads (for example 60w) you gotta use powerful dummy loads - put for example a power resistor or some auto light bulb
there are control boards that cut juice when the load is not the expected one, this is the correct practice
15k as load is not what it should be
anyway, those heating elements are simple to diagnose, except some oxidised protection switch, that's why a load is recommended.