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Electronpusher0 · 19th Feb 2021, 6:16 pm

I purchased a Weller EC2002DA base unit from Julesomega, the left hand one here:
https://www.vintage-radio.net/forum/...43&postcount=8

The fault was described as "briefly flicks up a display before going blank"

The EC2002DA base unit takes the EC1201P iron and makes the Weller EC2000D.

When it arrived I stripped it down and cleaned up the case. I then reassembled and started testing.
The EC2002DA base is easy to work on as the two modules, the control board and the display board are independent and can be tested separately.

I tested the control board by connecting a 24V bulb to replicate the iron element and a 51ohm resistor to replicate the sensor.
On testing the bulb was on continuously at all settings of the pot. It turned out the Triac was short circuit.
I replaced this with a BT136, same pinout. - That got the Control board working.

The display board fault was exactly as described. The circuitry mainly consists of a pair of chips that form a DVM. The chips are now obsolete and replacements are expensive and of suspect provenance.
I decided to go back to basics and see what the display actually did.

The Display board takes a voltage from either the temperature set pot or (after amplification) the sensor as selected by a “SET / READ” switch. The sensitivity is set by a pair of pots and displays 400 for an input of just over 5V.

I decided to make a new display board using a 3 digit Chinese DVM module. These are 3 wire, Red is the supply, Black the common 0V and Yellow the input to the DVM.
The sensitivity as supplied is 0 to 100V auto ranging. The lowest range being 0 to 9.99V

Testing this on the bench I discovered that putting a 50K pot in series with the input allowed me to set the sensitivity to the same as the Weller display board.

The replacement display board consists of a half wave rectifier and capacitor for the supply to the DVM module, using the same ac input the original board used, a switch and two 50k pots, could not be more simple.
I did however put a drop of black paint on the decimal point to blank it out.

I then calibrated the control board and new display board according to the procedure in the manual (slightly modified in the case of the display).
The Base unit was then fully working and calibrated.

The pictures show before and after.

Peter

19th Feb 2021, 6:16 pm	#1
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,300	Weller EC2000D repair I purchased a Weller EC2002DA base unit from Julesomega, the left hand one here: https://www.vintage-radio.net/forum/...43&postcount=8 The fault was described as "briefly flicks up a display before going blank" The EC2002DA base unit takes the EC1201P iron and makes the Weller EC2000D. When it arrived I stripped it down and cleaned up the case. I then reassembled and started testing. The EC2002DA base is easy to work on as the two modules, the control board and the display board are independent and can be tested separately. I tested the control board by connecting a 24V bulb to replicate the iron element and a 51ohm resistor to replicate the sensor. On testing the bulb was on continuously at all settings of the pot. It turned out the Triac was short circuit. I replaced this with a BT136, same pinout. - That got the Control board working. The display board fault was exactly as described. The circuitry mainly consists of a pair of chips that form a DVM. The chips are now obsolete and replacements are expensive and of suspect provenance. I decided to go back to basics and see what the display actually did. The Display board takes a voltage from either the temperature set pot or (after amplification) the sensor as selected by a “SET / READ” switch. The sensitivity is set by a pair of pots and displays 400 for an input of just over 5V. I decided to make a new display board using a 3 digit Chinese DVM module. These are 3 wire, Red is the supply, Black the common 0V and Yellow the input to the DVM. The sensitivity as supplied is 0 to 100V auto ranging. The lowest range being 0 to 9.99V Testing this on the bench I discovered that putting a 50K pot in series with the input allowed me to set the sensitivity to the same as the Weller display board. The replacement display board consists of a half wave rectifier and capacitor for the supply to the DVM module, using the same ac input the original board used, a switch and two 50k pots, could not be more simple. I did however put a drop of black paint on the decimal point to blank it out. I then calibrated the control board and new display board according to the procedure in the manual (slightly modified in the case of the display). The Base unit was then fully working and calibrated. The pictures show before and after. Peter Attached Thumbnails