My Oster Toaster stopped popping up after a couple of years as well - the lever just stays down until you unplug it or the toast catches on fire.
R3 was burned and replaced per the info on these discussions to no effect.
So I mapped out a rough schematic from the board and found some interesting things. Oster seems to be directly rectifying the line voltage (dangerous but cheap) through D1-D4 into 5V through DZ4 and 32V through DZ1.
These voltages seem to be across R3, which means it has 27V on 1K or about 0.73W on it continuously! Not only is this a waste of power, but it will always burn a 1/2W resistor. I would recommend replacing it with a 1W or larger and setting it up off the board to dissipate the heat into the air.
Then when toasting, the NPN transistor Q2 pulls to GND one side of the coil that holds the lever down. R3 is used as a series current limit for the 32V supply to the other side of the coil (so it has 32V or over 1W on it when toasting).
My problem with the toast not popping up was related to Q2 being blown. I don't remember the original number since I cut it out, but they seemed to have used an audio transistor with a Vce of 20V and Ic of 20mA. No wonder it blew with 32V and 32mA on it - bad design from the start.
I replaced Q2 with a cheap, commonly available 2N2222 - it has the same pinout and is good for 1A and 50V. It's been working great for months, but sadly still burning almost 1W continuously or over 6KWh per year.
Feb 28, 2007 |
Oster 6329 2-Slice Toaster