My thanks to all for helpful comments.
Updates:
1)Triac Gate disconnected as suggested by Jamie and No heat, so confirms Triac OK.2)No S/C between heating element and earth/common. Now looking upstream from Triac.
3)I have checked the temp sensor in Iron (wand) and it's O/C ALL of the time. So, have substituted a low value Pot and can now create a variation in readout on Station display now, but still the element is ON all the time (red hot tip etc!)Richard
Triac OK.
from Triac.
time. So, have substituted a low value Pot and can now create a variation in readout on Station display now, but still the element is ON all the time (red hot tip etc!)
Have you tried forcing a change of the inputs to the op-amp? Any idea what the 8pinner is? presumably not an EEprom as nothing to store
I think the MAX406 is an op-amp.
I think the LT508 1298 might be a A-D converter but I can't find any info other than a vague reference. I was hoping this was an Opto.
There is a 93LC46 which I believe is a PROM.
Then there's the PIC16C57 28 pin device.
All seems potentially OK, ie display works, voltages appear as expected.
The fault seems to be the switching of the heating element which is locked ON all the time.
However I notice there is nothing happening and no change to MT1 on the triac during any state including forcing the temperature sensing.
I can see DC levels varying on the temp pot.
Low power precison op amp
other than a vague reference. I was hoping this was an Opto.
PWM & PFC?
all the time.
during any state including forcing the temperature sensing.
Most of these ICs are obsolete.
info other than a vague reference. I was hoping this was an Opto.
locked ON all the time.
triac during any state including forcing the temperature sensing.
Sounds like a severe case of KISS
Buy a cheap HAKKO clone for $30 on Ebay. Plenty of spare parts & tips available cheap. I just bought three replacement irons for $20, delivered and 10 tips for $8 delivered. I picked up a 5A boost converter to use one off a 12V jump (start) pack. Replace the 10K trim pot with a panel mounted control, and a socket for the iron and I'll have an adjustable iron to use away from my bench (for under $15 (US)) I'm going to stick it in a small ammo can, with the other tools needed for field work and leave it on my crash cart so I can grab it on the way out the door.
other than a vague reference. I was hoping this was an Opto.
all the time.
during any state including forcing the temperature sensing.
Says here the LT508 is a Power Factor and PWM control voltage device.
If you have a scope, probe the gate to common side and look for a pulse. If you see a pulse there like it's trying to turn off the gate, it is a good possibility the Triac could be bad.
If you can look at the triac number and see if it is a sensitive type, these types are known to have issues and they could lock on..
what I have seen happen in some cases is this, if the power supply on the control board bets a little noisy due to bad caps, a small ripple can be present at the gate and thus turning it on..
If you are not sure about this, you can disconnect the gate and then do a meter ohm check between the gate and one of the terminals.. A non-sensitive gate type will have some resistance down in the 300 or less range. Most of them are in below 100 ohms..
You many not have a opto isolator since the output voltage is most likely low to start with. One of my stations only uses 6 volts if I remember.. And a couple of others use 24 volts. Either way, the driving electronics more than likely is directly coupled to the gate. This is actually a bad idea btw. You happen to touch the tip some where in a hot spot of a piece of equipment, it can back track and take out the stations control electronics. The heater elements are suppose to be isolated, but HV tends to jump over boundaries.
Jamie
"radio10"
** So tye iron is faulty - just as you were told.** Such sensors are only a few ohms and typically drop in value as the tip heats.
FFS buy a new iron.
... Phil
info other than a vague reference. I was hoping this was an Opto.
locked ON all the time.
triac during any state including forcing the temperature sensing.
What data could the Eeprom be used for storing , in a soldering iron operation?
Calibration for the temperature display, rather than a couple pots. That allows for automated calibration on the production line. I'm doing that in a custom soldering station I'm building. It will control up to five irons, with individual settings, and one can be a desoldering iron. That will give me several types of tips, without having to constantly change them.
OK.
Triac.
So, have substituted a low value Pot and can now create a variation in readout on Station display now, but still the element is ON all the time (red hot tip etc!)
The temperature sensor shouldn't be open circuit, so you definitely need a new sensor. An open sensor results in no heat on the Weller's I've owned. It's possible that runaway heat ruined the sensor. Don't let it overheat since it will drastically reduce the life of the heater.
Have you checked for open wires in the cord?
I have seen bad electrolytic caps on control boards that caused various problems.
The EEPROM just contains calibration info, and stores some options like C/F, and control lockout. There's a device that you plug into the soldering iron connector that lets you calibrate and set the options.
If you really want to fix it, buy a new sensor, or iron, and be prepared to replace the control board if you can't fix it.
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