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Sir donp . . . . .
Hmmmmmmmmmmmm . . . . Duratech # TS1560 . . . . being a HAKKO 936 knock off / clone ? ? ? ? ?
Look at the PCB and confirm if one end of this R2 resistor is being connected to pin #3 ( or alternatively / possibly #5) of an LM358 eight pin I.C.
And that the other end of this R2 resistor ends up at a connector pin of the cable that exits to go to the iron hand unit and its built in internal K type thermocouple- heat temp sensing function for the heating element..
Also, check to see if a small 100nf bypass capacitor also goes from that same I.C. connection to ground.
If so, its for durn shure , that units 2.2 K cal " trim resistor" was not damaged by overload,or, were you just randomly picking your " fish " out of the boards ocean of resistor possibilities ?
If the above routing disagreed, the second possibility is the IC pin 2 is connected to a junction of a 100K resistor and negative lead of a 220ufd / 16 V E-capacitor, with R2 THEN being a 100K resistor that goes to ground ( SAME-SAME as pin 1 of LM358).
If neither of these fall into place . . . you physically inspect and tell WHAT points your units " R2 " is being connected to.
73's de Edd
After all is said and done . . . . . . . . . . usually more is said than done.
Hmmmmmmmmmmmm . . . . Duratech # TS1560 . . . . being a HAKKO 936 knock off / clone ? ? ? ? ?
Look at the PCB and confirm if one end of this R2 resistor is being connected to pin #3 ( or alternatively / possibly #5) of an LM358 eight pin I.C.
And that the other end of this R2 resistor ends up at a connector pin of the cable that exits to go to the iron hand unit and its built in internal K type thermocouple- heat temp sensing function for the heating element..
Also, check to see if a small 100nf bypass capacitor also goes from that same I.C. connection to ground.
If so, its for durn shure , that units 2.2 K cal " trim resistor" was not damaged by overload,or, were you just randomly picking your " fish " out of the boards ocean of resistor possibilities ?
If the above routing disagreed, the second possibility is the IC pin 2 is connected to a junction of a 100K resistor and negative lead of a 220ufd / 16 V E-capacitor, with R2 THEN being a 100K resistor that goes to ground ( SAME-SAME as pin 1 of LM358).
If neither of these fall into place . . . you physically inspect and tell WHAT points your units " R2 " is being connected to.
73's de Edd
After all is said and done . . . . . . . . . . usually more is said than done.
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Greetings 73's de Edd and thank you for your reply. One end of R2 is going to pin 4 of LM 324N. I can't recall what problem this iron had or why I suspected the board or that particular resistor but would like to put it back in to see what I get. R1 is 150R for what it is worth. I've taken a couple of pics to try to make things clearer. it is one horrible looking board.
Attachments
Sir donp . . . . .
O.K. then, with your board using the LM324, there are variants of that, and your board suggests of a 2008 vintage .
Take note of the power transformers 24 AC coming as the paired black wires to the right top corner of the pcb.
There the "cold" side of the AC supply routes to the left to become the AC and DC ground and the peripheral foil path drops on down for one portion of the AC for the soldering irons heater. The other AC line routes around the right periphery of the pcb to the TO-220 cased Triac, to selectively pulse power to the soldering irons heater.
The "hot" 24 Vac line also feeds into D1 diode to make you DC, and that DC then feeds into the pristine 150 2W metal film dropping / filter resistor and then into the closest BLACK E-cap and then there is being your missing R2 . . . a " twin " 150 2W metal film dropping / filter resistor . . . and it feeds into the lower, and further back, BLACK E-capacitor for even more filtering.
Then that supply line drops down to pin 4 . . . Vcc for your LM324.
As frugal as they were, I am seeing not even a trace of a 3 term regulator . . .or even a Zener diode placed on that supply.
So check that D1 diode to see that its not shorted as well as those 2 E-caps . . . IF . . . . you find a shorted diode.
Since that specific situation seems to be the only reason for there being any suspicion of having problems with those two in series arranged resistors.
As per the boards appearance , the worst just seems to be the liberal use of flux on the connector and then a lack of its final clean up.
Did you check out your units heater element and the sensor . . . as I have shown on the inset, in BLUE and RED ?
PHOTO REFERENCING MARK-UP . . . . .
73's de Edd . . . . .
Almost everything in life is so much easier to get into . . . . . than to get out of.
.
O.K. then, with your board using the LM324, there are variants of that, and your board suggests of a 2008 vintage .
Take note of the power transformers 24 AC coming as the paired black wires to the right top corner of the pcb.
There the "cold" side of the AC supply routes to the left to become the AC and DC ground and the peripheral foil path drops on down for one portion of the AC for the soldering irons heater. The other AC line routes around the right periphery of the pcb to the TO-220 cased Triac, to selectively pulse power to the soldering irons heater.
The "hot" 24 Vac line also feeds into D1 diode to make you DC, and that DC then feeds into the pristine 150 2W metal film dropping / filter resistor and then into the closest BLACK E-cap and then there is being your missing R2 . . . a " twin " 150 2W metal film dropping / filter resistor . . . and it feeds into the lower, and further back, BLACK E-capacitor for even more filtering.
Then that supply line drops down to pin 4 . . . Vcc for your LM324.
As frugal as they were, I am seeing not even a trace of a 3 term regulator . . .or even a Zener diode placed on that supply.
So check that D1 diode to see that its not shorted as well as those 2 E-caps . . . IF . . . . you find a shorted diode.
Since that specific situation seems to be the only reason for there being any suspicion of having problems with those two in series arranged resistors.
As per the boards appearance , the worst just seems to be the liberal use of flux on the connector and then a lack of its final clean up.
Did you check out your units heater element and the sensor . . . as I have shown on the inset, in BLUE and RED ?
PHOTO REFERENCING MARK-UP . . . . .
73's de Edd . . . . .
Almost everything in life is so much easier to get into . . . . . than to get out of.
.
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you are a wealth of knowledge and I really appreciate you sharing it. So R2 is 150R? I wondered that but wasn't keen enough to just put one in to see if it generates the magic smoke. Thanks for the advice, I haven't checked the heater and sensor yet but I remember it wasn't heating which is why I am puzzled i was looking at this board in the first place. I'll put the resistor in, check some more and report back.
ok so I didn't have a 150R carbon in stock but had a 150R fusible resistor so used that instead. The red heater LED wasn't illuminated so I 'thought' it still wasn't working and was puzzled when I found all voltages present. After some serious head scratching it occurred to me maybe the LED had blown. It was around the same time I could smell a bit of heat coming off the iron. It turned out the LED had a dry joint and after a dab of solder it came on and all is well. R2 was the only problem but this thing got put aside and then forgotten about. I think it is a 2002 vintage from memory and has been fine overall considering it was about half the price of my Weller which is also on the blink but I know it is the heater element. Thanks again for your help 73's de EDD
