OMRON E5CS heater controller Diode identification help

[lethbrp]

Hi everyone,

I have a diode that I need help identifying. I've been scouring the web (newbie) can can't seem to find anything. Perhaps I'm looking in the wrong place. Attached is an image of the diode. If you could help me it would be greatly appreciated. Also, an explanation of how to calculate the values would be great.

Thanks for your help.

Peter

[petehall347]

Re: Diode identification help

any markings on the other side ?

[lethbrp]

Re: Diode identification help

Unfortunately not. Just a violet band.

[SMDFlea]

Re: Diode identification help

Unfortunately not. Just a violet band.

What PCB has it come from,any model numbers ,is a schematic available .

.

[lethbrp]

Re: Diode identification help

It's comes from a OMRON E5CS heater controller. I haven't been successful in finding any schematics I'm afraid.

[stj]

Re: Diode identification help

does the board have markings where it was?
actually, show us the whole board - it may give a clue

[lethbrp]

Re: OMRON E5CS heater controller Diode identification help

Attached are some images of the board. This is this is the power board that converts the AC into various DC voltages for the logic board.

Running a did from a good board through a component analyser, it says it's a Diode Junction with a forward voltage of 0.672v at 5v. So I'm guessing that it's not a schottky diode or Zenner. Therefore, its it safe to assume I could replace this with even a 1n4007?

[redwire]

Re: OMRON E5CS heater controller Diode identification help

It appears to be a 3-transistor SMPS and D4 is part of the drive to TR3. I think 1N4007 is too slow, you would use a high voltage fast switching diode 1N4937, UF4004, FR107. Could even be SMT tacked on to the bottom of the board like ES1J, FR2G, RS2G (400V) etc.
Check the cap C6 is not shorted which would mislead in-circuit readings.

D1 has a black stripe and more, so it might be a zener.

[lethbrp]

Re: OMRON E5CS heater controller Diode identification help

Many thanks for your help.

I did replace the main capacitor, that had gone.

Do you know what purpose the small blue capacitors serve. In my ignorance, I thought it was these two capacitors and resistors that were creating an oscillation which was driving the main transistor to the transformer.

[stj]

Re: OMRON E5CS heater controller Diode identification help

the small ceramics are snubbers to protect the diodes and reduce rf.
it does look like a regular diode - cant tell the current.
if you want to risk it a 1n4148 can handle 250ma otherwise just use a UF4007

[lethbrp]

Re: OMRON E5CS heater controller Diode identification help

It appears to be a 3-transistor SMPS and D4 is part of the drive to TR3. I think 1N4007 is too slow, you would use a high voltage fast switching diode 1N4937, UF4004, FR107. Could even be SMT tacked on to the bottom of the board like ES1J, FR2G, RS2G (400V) etc.
Check the cap C6 is not shorted which would mislead in-circuit readings.

D1 has a black stripe and more, so it might be a zener.

Could you please explain how this works. If I were to guess, the transistors are used to create an a/c voltage to drive the transformer large enough to satisfy the out dc voltages required by the logic board. What I'm struggling with is how the transistors work to create that specific a/c voltage.

[lethbrp]

Re: OMRON E5CS heater controller Diode identification help

There are no feedback loops and no op amps. so how is the switching controlled?

[redwire]

Re: OMRON E5CS heater controller Diode identification help

It's not regulated, the sloppy output that moves around say 8-10V, can then feed voltage regulator IC's to look after that. It must have a 5V reg IC too.
Some designs try to use reflected primary voltage as a rough idea of secondary voltage, in regulating.
The module seems to output 5VDC (used by the relay as well) and another rail
output at the 5-pin header.
The PC board does need the flux cleaned off with IPA and q-tips or something.