dark lcd display

Peter,

I don't buy microwave ovens, I just fix them.

This model of microwave R21LV has a few variants which have been mfred since before Y2K. It's service manual illustrates a panel with a completely different display on the control board, possibly even LED, vs the LCD variety present here.

I've got nothing but respect for Sharp stuff. My pocket calculator from the 90s has been through the laundry twice, without permanent damage. It has an early type of LCD display.

I've seen LCDs that have obvious damage/discoloration and flakey elements before, but never something that was permanently, uniformly dark.

There's no carbon press strip to degrade, just 15 solderable in-line pins.

I would suspect the controller chip, or its ceramic resonator, but the chip seems to be performing normally. The unit runs.

RL

dream on

Service manual shows 4x9 connections more suited to an LED display coming from a 64pin micro through a quad buffer and nine unbuffered lines from paralleled ports with 100R series limiters.

The current rev board is a 56pin QFN package driving the 15 pins of the display directly.

3 of the 15 pins generate quad-state ~ramps between 0 and 5V. Pins 1 , 2 and 10. The rest just clock (150Hz) between the two mid-state levels, in sync with the ~ramping steps.

This controls segments of 4 digit clock, its middle colon and

5 symbols for mode of operation, spaced ~ equally below the digits and mid-colon.

I've searched all over for a more accurate service manual, or a revision that includes the change to micro and display, but this is only reflected in purchasing spares. The old control panel assy number is retired to be replaced by . . .

A custom LCD-only part for the control board assembly isn't a likely after-market item. The whole panel is available for $$$.

This one is from 2012, about half way through the product's history.

RL

This thing is in working order and programmes.

It had some gunk penetrating the stiring motor couplig shaft area that had carbonized and would cause visible arcing, until the polyproplylene components were scraped completely clean.

It's just inconvenient and unsafe to run without confirmation of an obvious countdown in the run time.

If I brush my thumb across the display the major ' 1 ' and 'ON' segments display, regardless of operating state or cooking time. These fade gradually.

RL

Was the product sitting around a long time unused?

It was brought in producing sparks, with a burnt stirring motor, burnt lamps. Don't know when the display stopped working.

In perfect working order, now, but dangerous without feedback to end user.

RL