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Black and Decker Toaster oven Toast Switch Repair TRO360 / TRO200

Discussion in 'Troubleshooting and Repair' started by gromittoo, Jan 2, 2011.

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  1. gromittoo


    Jan 2, 2011
    I am reposting this as it really helped me, and I wanted to add an update:

    Originally posted by guest on 12-03-2004, 10:53 AM
    Posting this for the benefit of others ( Google Groups search etc.)

    We purchased a Black and Decker TRO-360 Toaster Oven about 4 months
    ago and recently the toast switch failed. The switch does not stay
    down. According to the reviews at Amazon this is a common problem.
    Many people in the reveiw section for this item are complaining of the
    same problem. I decided to try and repair the oven as I have an
    under counter bracket and heat shield for it which is very handy.

    The switch is held down by an electromagnet that is driven by a small
    timer board inside the oven. The timer board converts the setting of
    the toast setting pot to a digital value and then uses a 'count-down'
    type digital timer to control the toasting time. The part that
    failed on the timer board in ours was a 6.2V Zener Diode part number
    1N4735A that provides power to the CD4060 CMOS counter chip used as a
    timer. The zener failed open and was only providing only about 1V to
    the circut instead of the 6.2V required. It was an easy fix and now
    it works like brand new again. Because of the nature of the circuit,
    it was hard for me to trace the problem to this little guy. It is
    the only zener on the little circuit board. I had a 6.8V 1W Zener in
    my junkbox and because the CMOS chip is tolerant of a wide range of V
    I used that instead of the factory part. It seems that the timer
    maybe runs a bit faster now but it works just fine. Just need to set
    the toast setting knob a bit lower.

    I am posting this because I searched the Internet expecting to find a
    technical note or release from B&D about this problem or maybe a post
    from someone else. No luck! I suspect that this is probably what is
    failing on all of them and a defect from the factory. Would be
    curious if you own one of these ovens with this problem, please email

    Have yet to have it make any toast that is worth selling on Ebay but
    still hoping.​

    I found this expired post via an online search. This Zener diode fix applied to mTRO200 toaster as well. Radio Shack only stocks two Zener Diodes: 12 volt and 5.1 volt. The 5.1 volt works fine as a replacement for the 6.2 volt part. [1N4733A | Radio Shack #: 276-565 ]

    The circuit is your basic Bridge rectifier of line voltage, a 520k resisitor, and Zener to bring the DC voltage down to something the CMOS counter can work with. The circuit is only gets power when the toaster switch is held in by your finger, or the solenoid. The knob on the front is a pot, that varies how long the countdown timer will last. At the end of the timer, the transistor that energized the solenoid holding the toast switch in, no longer gets current, so the button pops out.

    I would recommend anyone attempting this repair to buy a Surge suppressor part (a MOV?) and solder it in parallel with the Zener. I traced the circuit, and there is only a tiny ceramic capacitor and a larger Mylar capacitor protecting this circuit board. The spark from the toaster switch, or the back EMF from the solenoid might be overloading the Zener, causing it to short out. Radio shack sells the Zener diodes in pairs, and I was tempted to use them both in parallel.

    To all those who will poo-poo me for wasting time on a toaster oven, I say they never had one of these older units. The electronic toaster timer is 100% consistent, unlike toaster ovens with mechanical or thermal delays. Additionally, I bought the under counter hood for this unit, which can only be used on B&D toaster ovens made in the early 2000's (mine has a date code of 4403). This hood is a clever design, which holds the oven firmly in place, yet makes it easy to remove for cleaning, or for quick transfer to the sink if hot dog grease catches fire.

    I cannot find any TRO200 / TRO360 models on eBay or crag's list anymore, so I decided to fix this one. Took less than hour.
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