Looking for Schematic for Intermatic E1210 Countdown Timers

[kraml]

Both of the Intermatic E1210 countdown timers in our house just went bad within two weeks of each other. I suppose I installed them 15-20 years ago (for bathroom exhaust fans). They both came on without assistance and remained stuck on--no response to user controls. I reset the household circuit for the first, and then for the second, without success. Stuck on. Opened each. Both show failure in same area of board: a zener, a resistor, and two shottkes. The resistor has a pink band. I don't know if that's original or heat-generated. Anyway, it's only a guess, but if the resistor broke down that might have taken out the schottky, which shorted. I did not take any parts out yet. No need to do so if I can't spec the resistor. So, I'm looking for a schematic for this unit, if anybody has one. They're $55 each on Amazon! Might be worth repairing.

[stj]

Re: Looking for Schematic for Intermatic E1210 Countdown Timers

well, it's a capacitive dropper based around the big film cap,
then regulated by the burned resistor and the zener
and those 2 under-rated parts probably cooked the electrolytics.

check the film cap first - they do degrade.
and check the rectifier diodes.
no point going for the zener and resistor till you know the first part of the psu is good.

[redwire]

Re: Looking for Schematic for Intermatic E1210 Countdown Timers

The burned up resistor R2 is not great (carbon comp), by today's standards it is a fire hazard and they must be flameproof and fusible.
Mains-powered stuff using a capacitive divider on 24/7 does not really last forever, and less so with the heat. Many parts just get worn out and I would say 5-7 years is a lifetime limit. This one seems to be at the 15 year mark.
The problem these kind of units have is when the relay is off, the extra current is wasted as heat in the zener diode. So it has enough power for the relay when on but it's not needed 99% of the time. The zeners are a common failure, but would not burn up a resistor.

It's possible to sketch the schematic with a pic of the other side of the board. It seems to have a 24VDC rail for the relay, and a low voltage rail for the MCU and LED's.
I'd overhaul by replacing the parts that wear out - dropper and electrolytic capacitors, zener, resistor etc.

Home Depot sells the Intermatic EC201WK for $USD 24, and there's the Woods for $12 so I would go that route with something new.

[kraml]

Re: Looking for Schematic for Intermatic E1210 Countdown Timers

Thanks stj and redwire for your kind responses. I'll start with the suggestion by stj, to check the cap. I just now installed a replacement timer from Amazon in the master bath (https://www.amazon.com/dp/B00TSUJ5EU). I ordered it right away when the master bath died. I might be a little slow to respond to the thread. I had cataract surgery last May/June, and they're not finished with me yet! Anyway, that slows me down on everything. I have to work extra to make out solder joints, etc.

[stj]

Re: Looking for Schematic for Intermatic E1210 Countdown Timers

open the new one and if it's similar you can see the resistor value

[kraml]

Re: Looking for Schematic for Intermatic E1210 Countdown Timers

The cap reads a little low: 0.824μF (It's a 1.0 μF @ 10%). But it's Chinese, you know . . . . ESR is 0.58Ω.

[kraml]

Re: Looking for Schematic for Intermatic E1210 Countdown Timers

Resistor died open, as expected. Duh. Zener seems functional w/continuity test. My guess now is that the chip contains a normally closed circuit that's kept open by low power (until user selection). Maybe it's designed to go constant on if low power fails, as an alert that something's amiss.

[kraml]

Re: Looking for Schematic for Intermatic E1210 Countdown Timers

Intermatic no help on board schematic. Bought identical unit from ebay. Definitely designed to default to constant-on load when the circuit under discussion goes open. Soldered in a 2.2k resistor (original calls for 2k; did not have). Timer controls unresponsive, but resister got pretty hot in short order. Removed resister and and tested for kicks; yep, constant-on load. Resistor shows 50v (!), against leg of 1uF cap, with slight variation on either side. Need to understand how the capacitative dropper works. Also, guessing that the zener is 24v; may have to test the one on the new unit from eBay. Rectifier diodes appear OK, per beep test.

[kraml]

Re: Looking for Schematic for Intermatic E1210 Countdown Timers

Having trouble sourcing an X2 10% Cap that will fit where the original cap sits. It can be 25x11 mm at the very max. There is no extra room inside the case. Most X2's at Digikey etc., are 26.5mm--and I also need long leads to finagle a large cap in there.