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Old 19th Jul 2017, 9:56 am   #1
chriswood1900
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Default Weller DS801 temperature setting.

I'm looking for a bit of help with my older Weller DS801 de-soldering station, basically it works but the temperature range seems to be out.
It warms up ok but all the temperatures seems low compared with the setting. 50°C is barely warm and 400°C will just melt lead based solder, but it does seem to maintain the temperature OK. Inside there is a PCB with 2 presets which I’m assuming set the parameters of operation, before I randomly tweak does anyone know how they are set up. I assume this board was probably used on other Weller equipment dated in the mid 1980s. Also if anyone has a manual it should be useful.
The pictures show the model and the board.
Many thanks
Chris
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Old 19th Jul 2017, 10:18 am   #2
ukcol
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Default Re: Weller DS801 temperature setting.

Sorry to be negative Chris but if the station has been in your possession and working OK (that is you know the pots have not been twiddled) adjustment of the pots is unlikely to solve the problem. I think that as the temperature is out to such a large degree you must have a fault; possibly the sensor in the iron or a fault in the control circuit. You may get lucky doing a cold check of components on the control board, otherwise you will need some service documentation to go further.
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Old 19th Jul 2017, 10:38 am   #3
chriswood1900
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Default Re: Weller DS801 temperature setting.

Colin, it only recently came into my possession, I bought it whilst at the NVCF, I don't know its history but it does not appear to have been messed with. Lets hope someone has a manual.
regards
Chris
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Old 19th Jul 2017, 4:47 pm   #4
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Default Re: Weller DS801 temperature setting.

Perhaps if you don't find a manual you could reverse engineer a circuit diagram. Are those ICs marked with their type number?
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Old 19th Jul 2017, 8:29 pm   #5
chriswood1900
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Default Re: Weller DS801 temperature setting.

Well that was an interesting day, I did some Googling and found the data sheets for the ICs used, there is 78L05 5v regulator an LM358 twin op-amp and the a SL443 zero voltage switch to control the Triac which provides power to the element. The regulator provides a stable reference to do a comparison between the heat sensor and the variable resistors that set the temperature. As I said in the first post everything seemed to work it was just running at a lower than expected temperature. I noted the settings of the two pre-sets. And did some tweaking the temperature range could be widened if they were turned fully anti clockwise but as they were almost fully that way scope to improve was limited.
I had some coffee and decided to do some more searching online and eventually spotted among the images the same circuit board as mine. It appears Weller used the board in the WECP-20 and the EU version VP801, using this as the search criteria I found a section of the Weller service info which I include below as it is hard to read.
Checks to do
First on the Iron part
The sensor across pins 2 should be 22ohm
The heating element across pins 3 should be 12 ohm, both these were correct.
Next on the board using the numbers on the plug.
1. The transformer voltage across pins 1 & 3 24v AC
2. The supply voltage between G on the regulator and the output 5V
3. Range of potentiometer 2-5V DC
4. If the value of the sensor feed at pin 18 is less than 3V the op amp is probably defective.
5. The -5v pulses to fire the Triac are at pin 19 (Pin 1 of LM358) (I could not measure this pulse)
6. Pulses to the Triac measured at pin 3 1ms 1.4V on a scope. (See picture 3 below)
7. Not used on the DS801 as far as I could see.
I went through these checks and all were OK except the voltage range on the 2.5k temperature setting pot. I then removed the board and decided to check as many components as I could. The caps were crusty and I replaced the 220uf 16v and 0.47uf, the 220uf was running close to it limit with 14.5 across it, the 0.47uf looked as it may be leaking. Both were replaced with 105°C 35v parts.
This had the effect of cleaning up the trace to the Triac but nothing else. I also noted when checking the board that the resistor next to the SL443 was shown as 909R (an odd value) was in fact only 100ohm I could see no reason for the difference so I substituted a 910ohm I had in stock, this brought the range of the setting pot back to where it should be 2-5V and when I powered up I could adjust the pre-set pots P1&P2 clockwise a bit. I borrowed the cooking thermometer and wired the sensor to the tip of the iron part and adjusted P1 watching for cut out of the pulses to the Triac to get 50°C . The thermometer did not seem to be very good at higher temperatures so I adjusted P2 so that I could melt unleaded solder at a setting of 250° I then turned it up to 400°and it got nice and hot then cut out but I have no way of accurately measuring it. Any ideas?
So what can we conclude from today’s efforts the unit was EX BT did not look as though it had much use and just worked if you cranked it to maximum, so have I got a unit with a manufacturing fault from new not used much because it didn't work very well?
To assist others here are some of the links I used,
http://blog.antiguru.de/2014/06/weller-vp-801-ec.html
And some very good reverse engineering work here http://remotesmart.wikidot.com/weller-wecp-20
Chris
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Old 19th Jul 2017, 8:37 pm   #6
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Default Re: Weller DS801 temperature setting.

It might be the same as a DS80 which is available on the interweb

DS80
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Old 19th Jul 2017, 8:54 pm   #7
chriswood1900
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Default Re: Weller DS801 temperature setting.

Peter thanks, I think the DS80 is probably a bit later as the circuit shows a Mosfet in place of a Triac but the principle looks similar.
Chris
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Old 21st Jul 2017, 9:17 am   #8
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Default Re: Weller DS801 temperature setting.

Just for info- 909R isn't an odd value, it's the real E96 1% value closest to E24 910R.

Since most resistors nowadays are 1% anyway, it seems to be up to the manufacturer whether they're marked in E96 which needs the 4 band code or as E24 which only needs 3 if they're being sold in that range.
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Old 21st Jul 2017, 11:44 am   #9
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Default Re: Weller DS801 temperature setting.

Quote:
Originally Posted by chriswood1900 View Post
I had some coffee.....
Always a good idea.

Quote:
Originally Posted by chriswood1900 View Post
I then turned it up to 400°and it got nice and hot then cut out but I have no way of accurately measuring it. Any ideas?
I have a Workzone infrared thermometer that I purchased from Aldi (I think it was about £12) and it covers the temperature range you're interested in. It won't be as accurate as a Fluke of course but perfectly adequate for your purposes. If Aldi aren't doing them at the moment there are plenty of cheap infrared thermometers on ebay, just check the temperature range first, some only go up to 420 deg C.
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Old 21st Jul 2017, 12:04 pm   #10
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Default Re: Weller DS801 temperature setting.

Hi Chris,

maybe is the attached your circuit?

Regards, Karl
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Old 21st Jul 2017, 12:51 pm   #11
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Default Re: Weller DS801 temperature setting.

I have got a blue one of those work zone thermometers and it measures the average temperature of an area as apposed to a point reading of the iron tip.
One of those probes that come with DMMs would be better.
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Old 21st Jul 2017, 10:48 pm   #12
chriswood1900
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Default Re: Weller DS801 temperature setting.

Thanks for the replies, Colin I have a cheap Maplin infra red thermometer and could not get a decent reading from it, perhaps I need to buy a better one! It seems incapable of picking up a smallish point, does the Aldi one manage that?
Karl yes that is also very close but in my 2nd link someone has reverse engineered the actual circuit.
Chris
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Old 22nd Jul 2017, 12:09 am   #13
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Default Re: Weller DS801 temperature setting.

The Aldi one comes with a diagram that explains how large an area they cover relative to the distance from the surface you are measuring. They are good for the side of a water tank or a concrete surface on a sunny day.
Soldering tools need a contact type.
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Old 22nd Jul 2017, 9:27 am   #14
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Default Re: Weller DS801 temperature setting.

The Aldi thermometer has a 15mm aperture and the area it averages temperature over is cone shaped so that it will be fine measuring the temperature of a water tank from several feet away but you will need to get nearer for small areas. It won't be suitable for measuring the temperature of the tip directly but I would of thought that you could get a valid reading at the body of the iron where the tip emerges.

I have 2 contact type thermometers, a cheap DMM with a temperature probe and a dedicated R.S. digital thermometer. I'll have a go at measuring the temperature of my soldering iron and see how all 3 compare; I will report back.
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Old 22nd Jul 2017, 3:37 pm   #15
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Default Re: Weller DS801 temperature setting.

OK.

"Refugee" is correct, the IR type of thermometer is not suitable for this application.

The diameter of my Weller iron is only about 9.5mm and so will not fill the measuring cone area even at point blank range.
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Old 22nd Jul 2017, 5:04 pm   #16
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Default Re: Weller DS801 temperature setting.

A good option is to use a thermocouple as this can be held in close contact to the iron tip. The best option (but an extravagance ) is the Weller soldering iron temperature tester. These come up occasionally on eBay but are silly money. I had to get one when testing soldering irons for a cal. lab. In that case it was money well spent.

Phil
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Old 22nd Jul 2017, 5:54 pm   #17
chriswood1900
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Default Re: Weller DS801 temperature setting.

Thanks Phil
I'll have a look for a thermocouple that covers a suitable range.
Chris
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Old 22nd Jul 2017, 6:12 pm   #18
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Default Re: Weller DS801 temperature setting.

The thermocouples that come with some multimeters should be fine for the task.
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Old 23rd Jul 2017, 4:31 am   #19
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Default Re: Weller DS801 temperature setting.

Quote:
Originally Posted by ukcol View Post
"Refugee" is correct, the IR type of thermometer is not suitable for this application.
The diameter of my Weller iron is only about 9.5mm and so will not fill the measuring cone area even at point blank range.
The other problem with IR thermometers is the emissivity factor of the surface being investigated; this needs to be known and taken in to account for accurate temperature measurements. However, IR cameras are wonderful for finding abnormally warm or cold components on large circuit boards and thereby quickly finding faults.

B
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Old 23rd Jul 2017, 8:57 am   #20
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Default Re: Weller DS801 temperature setting.

Maplin have just three of these left at £1.99. (Discontinued line):

http://www.maplin.co.uk/p/740mm-k-ty...mocouple-n38cb

• A K-Type Thermocouple
• The wire is 740mm long and has a 3-inch metal type probe
• Temperature range is 0 to 800°C

They still seem to be stocking these, but they only go up to 250ºC:

http://www.maplin.co.uk/p/960mm-k-ty...mocouple-n37cb

Hope that may be of interest.
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