What are the parts on this 2-component board?

Thread Starter


Joined Dec 1, 2018

My background - auto-didatic computer twit, very tech inclined, hobbyist solderer/fixer/builder but no EE : (

I have a *flexible*, 50W solar panel; at top it has elec junction (board), for tabs of the panel's cells to meetup. This junction has 3 inputs, 2 outputs, and two components. The components are flat, almost-square, 2-pin, the size of your fingernail, and labelled Line1:"PJ357SVM" Line2:"1045V2". What are these 2, identical components? (I presume blocking diodes but the partnums google up with no matches). Ultimately I want the basic V & I specs for these (presumed diodes).

The Verbose:

The 3 attached pics show:
1) Panel, showing placement of board and still soldered in place (tabs protrude up, into slots)

2) Closeup of board:
- The 3 inputs are the 3 slots (center, left, right)
- the 2 outputs are at right- and left-most circular holes
- Electrically, the two components are arranged serially

3) A schematic; BlackBlob is the board; X & Z are the 2 components; Red/Blue/Yellow show the 3 inputs

The Backstory:
- Panel's Vopen would drop 50%, depending on how I held the panel - broken main-tab/trace?
- Started surgery at junction
- Want to know specs of diode - might want to replace them since I was overheating the board to free it from the tabs - hence the curvature in the removed-from-panel board : (
- FWIW panel still puts out its labelled Vopen (+/- 1V) and still blocks reverse voltage at dark

The Questionnaire:
Q1) Are the two components in fact diodes? If not, what?
Q2) How'dyaknow?
Q3) Might you know where I can find specsheet, or what are the specs of these critters?

Q4) Why does there exist the center-tab input to the circuit - I'd have thought that simply having the diodes inline with the + or - output from the panel, would suffice? Or maybe I'm just being confused by the layout, and a simple schematic depicting differently would elucidate?

Q5) Is there a way to test the (relevant-to-me) functioning of the diodes, esp as it might relate to power losses (i.e. am I losing more than before I over-heated the critters?)

BTW, I love the panel - took a beating for 5 yrs before I had this prob - found the problematic trace, resoldered, and it's back to new - a second honeymoon ; )

Full specs are:



Joined Feb 8, 2018
They are most likely Schottky diodes, but both photos obscure helpful clues. The resolution of the first is too low and the burned out highlights of the second make it impossible to get an idea of how the parts are mounted to the PCB. They sort of look like they are a special very low profile package with metalization on the bottom rather than flat formed "leads" found on most diode packages. There really isn't anything else they could reasonably be. PV modules with withstand short circuiting, so there is no reason to use a self-resetting fuse device. Resistors would have no use. There are many Schottky diodes around rated at 10 amperes and 45 peak inverse volts, which fits with part of the markings.

Most modern digital multimeters have a diode testing function. With the board out of circuit, it is easy. Depending on test current used by the meter, the forward voltage would likely be in the range of 0.2 to 0.3 volts, but might be a bit higher. In circuit, with a load and illumination, simply measure the voltage across them. In this case the voltage is likely to be at least half a volt but likely less than 0.8 V if they are Schottky, perhaps a bit higher if they are conventional PN junction diodes. The array ends will be the anodes, the output ends the cathodes.

EDIT: the drop of open circuit voltage is weird. It may be that these each of these diodes bypasses half of the cells in the array rather than being in series.

EDIT2: looks like they might be in TO-277 which is about 4.5 x 6.5 mm overall.
Possible direct equivalent:
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