Took another look at the diode numbers under bright lights--marking is
2.0B1--the dot between the 2 on 0 is centered vertically like 2-0B1.
Still reviewing circuit

"electroninja" wrote in message
oups.com...
| Sam,
|
| Just reviewed your paper on "Basic Testing of Semiconductor Devices..."
| and as a result retested diode. Analog readings were 4.7K and 2.7K
| ohms--still bad I assume.
|
| Will attempt to better trace circuit--also I've noticed Radio Shack has
| really changed from the old days--where is Allied Radio when I need them

Might as well look for a Lafayette Radio store as expect help from R/S.

N

NSM--ahh my canadian friend you are so right. Also, your idea to start
substituting low and going high is starting to sound pretty darn good
about now!

Sam--I've tried to trace the circuit as you requested. The zener is
involved directly with only two 25V capacitors and one 35V. The 35V is
right at the power supply ground. Starting at the black band--the zener
is in series with a 25V 100uf cap paralleled with a 1/4 W resistor
ending on pin 32 of 38870L25. Between the cap and pin 32 a transistors
collector is attached with the base truncating on pin 5 of the L25.

Back to the diode--moving towards the power supply is a 25V cap to
ground. Between the diode and cap is a wire to pin 12 of L25. A 35V
1000uf capacitor is grounded from the same voltage bias as the 25V cap
ground point then it (35V cap) tuncates at the power supply

I'm sure this isn't much help but the circuit looks like my wife's
spagettii dinners.

In review for people seeking to help: 1. Need the voltage and power
rating for a 2-0B1 zener diode (DZ2) on a Sharp R1810 microwave control
unit printed circuit board (H6C08) or 2. Good guess on voltage rating
for a suitable zener substitution for 2-0B1.

If anyone knows the working voltage for a 38870L25 that might help
also.

Thanks

Can anyone put their hands on a "GE Tansistor Manual" published
mid-1980's to research the 2-0B1 (2-DB1?) I have a 1964 GE publicaton
that does list BD series diodes--they are called back diodes? Could
they be the old term for zener's?
Thanks.

On 10 Jan 2005 10:03:57 -0800, "electroninja"
put finger to keyboard and composed:

Took another look at the diode numbers under bright lights--marking is
2.0B1--the dot between the 2 on 0 is centered vertically like 2-0B1.
Still reviewing circuit

See the HZ2 zener diode at this URL:
http://www.has.hitachi.com.sg/databo.../Diodes/HZ.pdf

The "B1" probably refers to the voltage tolerance, in this case 1.9 -
2.1V.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

On 10 Jan 2005 09:02:14 -0800, "electroninja"
put finger to keyboard and composed:

Sam, your question was:

Q. What does the top of the zener connect to?
A. One end traces to a 25V electrolytic cap--other end traces to a 4
pronged rectangular chip (S1VB ?) and eventually to the 32 pin on a
38870L25 processor.

The S1VB is a bridge rectifier. Is it possible that the circuit looks
like this:


uP-32 0--------|
| +||
|---||----|
| || C |
| |
|-----| | \ |
o--|~ +|--- R --|--||----|
AC |S1VB | \ ZD |
o--|~ -|------------------|
|-----|

Is the 38870L25 device the uP for the LCD?


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

On 9 Jan 2005 08:36:24 -0800, "electroninja"
put finger to keyboard and composed:

Sam--the contoller board has a hardwired LC6041 chip.

Looks like a Sanyo uP. Can't find its datasheet, though. :-(
http://service.semic.sanyo.co.jp/semi/search_ds_e.htm

My spare parts
microwave has the same chip and it works. Ever tried to unsolder a 48
pin LC without damaging it thru overheating?

Many times. TV and VCR uPs are of this type. Just use a variable
temperature iron and a solder sucker with strong suction, eg a
Soldapullt. I re-tin all the pins before starting. Often you can
desolder two pins in one go if you bridge them with solder beforehand.

Harry--this unit has only one thermal cutoff switch physically mounted
on the casing surrounding the magnetron--electrically it is upstream of
all loads and were it to activate it would shutdown everything (lights,
fans, control display.. etc)--which is not the case here. Thoughts?
Thanks for all comments--


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

My plan was just to remove the old LC and solder in a chip base--then I
wouldn't have to worry about overheating the new chip. I'm assuming the
LC61401 is a standard chip with no company EPROM giz stuff internal to
it.

"electroninja" wrote in message
oups.com...
| My plan was just to remove the old LC and solder in a chip base--then I
| wouldn't have to worry about overheating the new chip. I'm assuming the
| LC61401 is a standard chip with no company EPROM giz stuff internal to
| it.


Somewhere there is a ROM with the program. It's more likely to be in the
LC61401 than elsewhere. Can you see any other chips?

N

Yes, two chips: one 38870L25 located on a smaller board between the
relay board and the control board chip 064 604101 (on largest board
nearest the time display/function switches). I have a spare 6041 in a
Sanyo microwave that works and assume the chip is the same even though
it does have the last two digits (01). I guessing its like the old 6502
chip in that reguard.

Yes, two chips: one 38870L25 located on a smaller board between the
relay board and the control board chip 064 604101 (on largest board
nearest the time display/function switches). I have a spare 6041 in a
Sanyo microwave that works and assume the chip is the same even though
it does have the last two digits (01). I guessing its like the old 6502
chip in that reguard.

Frank I think we're getting closer on the diode mystery--the incircuit
voltage was 2.3-2.4volts when operating. Your chart indicated HZ2B1
limits are 1.9-2.1----diode marks appear to be 2-0B1 printed in black
ink around the radius of the zener. I substituted the old zener with a
5.1volt and the circuit did not like that at all--monitor lights dimmed
to the point where one couldnt read them. Didn't damage
anything--replaced old zener and ops went back as they were.
Thanks for the help

Circuit board seems to have two varicaps or varistors on the largest
power board (604101). Found one supply house that sells only one
component for this board--a varistor. Seems odd. In 1986, when this
unit was made, does anyone know what designers used for timing
control--no 555 chips to be found. Any posibility of a tunnel diode
oscillator circuit for timing or temp control. The zener diode in
question appears (thanks Franc Zabkar) to be a 2 volt diode running in
the circuit at 2.23-2.24 volts. If it were intended to bias a tunnel
diode oscillator circuit, the extra .24 volts might mess everthing up.
Any ideas?

"electroninja" writes:

Circuit board seems to have two varicaps or varistors on the largest
power board (604101). Found one supply house that sells only one
component for this board--a varistor. Seems odd. In 1986, when this
unit was made, does anyone know what designers used for timing
control--no 555 chips to be found. Any posibility of a tunnel diode
oscillator circuit for timing or temp control. The zener diode in
question appears (thanks Franc Zabkar) to be a 2 volt diode running in
the circuit at 2.23-2.24 volts. If it were intended to bias a tunnel
diode oscillator circuit, the extra .24 volts might mess everthing up.
Any ideas?

There may be a 32,768 Hz crystal for the clock or the micro divides
down its clock. Forget tunnel diodes. Anyhow, if the countdown works,
the clock is working. The fact that it cuts out in 40 seconds or so
means the firmware or hardware is corrupted or being told to shut off.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

"electroninja" wrote in message
oups.com...
| Circuit board seems to have two varicaps or varistors on the largest
| power board (604101). Found one supply house that sells only one
| component for this board--a varistor. Seems odd.

That may be because they have those in stock anyway.

| In 1986, when this
| unit was made, does anyone know what designers used for timing
| control--no 555 chips to be found.

The CPU does the timing.

| Any posibility of a tunnel diode
| oscillator circuit for timing or temp control.

None at all.

| The zener diode in
| question appears (thanks Franc Zabkar) to be a 2 volt diode running in
| the circuit at 2.23-2.24 volts. If it were intended to bias a tunnel
| diode oscillator circuit, the extra .24 volts might mess everthing up.
| Any ideas?

I'm afraid at this point remote diagnosis seems unlikely to help further.

N