Need some assistance identifying a SMD diode. It is part of the power output circuit of a Renogy 2000w 12v DC to 230v ac inverter. Renogy have been of no assistance - they seem unable to even identify the model number!! The output circuit was damaged by supplying 230v ac to the OUTPUT plug. So far I have determined that main switch, a couple of output MOSFETs (60N60F01) and associated resistors and diodes were toasted. The SMD resistors I can read (103) but the diodes have either no markings or have been burnt beyond reading even with a magnifying glass.
What information is required to determine what the diodes are? I could supply pictures, but circuit diagram is hard to decipher - I suspect the PCB may be multilayer.

 

Welcome to AAC.

Fortunately, they were diodes. Their physical size, ampacity, and voltage they have to handle are probably enough to guess at the proper diode. If you exceed the likely ampacity and PIV whatever you put there will probably work unless they are Zeners or Schottkys they should be mostly interchangeable.

You'll have to work out what the component size is, then based in their location in the circuit what current and PIV they are likely to have encountered you should be able to stick something in there.

 

Thanks for your prompt reply Yaakov. Unfortunately I have no clues as to ampacity of voltage, although physical size is 1206 format. It would help if Renogy were forthcoming with any information on this PCB. Unfortunately their attitude seems to be "don't tell them anything except the board is non repairable. Oh dear, buy a new one". Only things I have to go on are the toasted MOSFETs (60N60F01 - 60 amp, 600V), and the components connected to MOSFET legs - one side is burnt resistor (103) and burnt diode (?), other side is good resistor (100) and good diode (again no discernible markings). And the MOSFETs appear to be on the output side. On the input side are two banks of 4x MUR166OCT switch mode power rectifiers (600V, 16A). There are 4x 60N60F01 MOSFETs handling the output - two of them are good, two blown. The inverter is rated at 2000W, 230V continuous or 4000W momentarily.

 

Probably the safest bet would be to try replacing it with the highest rated 1206 diode you can find. It might be overkill but it would also be safe.

 

Ahh, now THAT I can do! Like you say, as long as they aren't Shottky or Zenner. Any recommendations?

 

Recently reading an article about Schottky diode applications and failure. Frequently used in power rectification circuits due to low forwards voltage drop and fast switching time. Failure predominantly from electrostatic discharge, " Schottky diode failure is seldom due to wearout mechanisms. This is especially the case with schottky diodes used on the output of power supplies, where failure is normally due to a single reverse current effect." which ties in well with this failure - 230V input applied to the 230v OUTLET point. Leading me to think this may be a Schottky diode that has failed. Any issue you can see replacing what may be a std diode with a Schottky in this application?

 

Recently reading an article about Schottky diode applications and failure. Frequently used in power rectification circuits due to low forwards voltage drop and fast switching time. Failure predominantly from electrostatic discharge, " Schottky diode failure is seldom due to wearout mechanisms. This is especially the case with schottky diodes used on the output of power supplies, where failure is normally due to a single reverse current effect." which ties in well with this failure - 230V input applied to the 230v OUTLET point. Leading me to think this may be a Schottky diode that has failed. Any issue you can see replacing what may be a std diode with a Schottky in this application?

Someone might have a reason to contradict me but I don’t see any problem with it, even if you don’t need the low drop. I suppose someone could design a circuit that depends on the drop but you can confirm using the intact diode and a DMM in diode test mode that shows the forward bias voltage.

 

Someone might have a reason to contradict me but I don’t see any problem with it, even if you don’t need the low drop. I suppose someone could design a circuit that depends on the drop but you can confirm using the intact diode and a DMM in diode test mode that shows the forward bias voltage.

Woo hoooo! Took another look tonight with a magnifying glass and bright lighting. One set of diodes are T4 (300mA, 75v), the others H5 (zenner 15v, 8.5mA). Question answered! And got a response from Renogy too:
Hi，Richard.

We are sorry that the accessories information you consulted is confidential information, please forgive us that we can not provide it.

Have a nice day.
Pfft! Wankers.
Thanks for your help Yaakov. Not sure if I would have persisted without a little encouragement