Gigrig Voltage Doubler Mystery

[lars-musik]

Dear fellows,
An acquaintance of mine demolished his Gigrig voltage doubler by applying 18V to the 9V input. After the smoke settled, he sent it to me. Now I am wondering whether you could help me de-mystify that thing.

First: What are four (4!) 9V-9V regulators (Recom RN-0909S) are doing in there? Wouldn't one suffice to regulate whatever goes in?

Second: What is this silvery part with the marking 050 BL5? I've never seen that before. And if yes, could this thing be damaged?

Thanks again!

[Rob Strand]

They are probably wired 2x9V in parallel then put those two 9V in series to get 18V.
If you look on the board you can see 4x2R2 resistors which help current sharing for the parallel connection.
The Gigrig voltage doubler is rated at 300mA and the Recom RN-0909S is 140mA  so the parallel connection gives 2x140mA = 280mA.

The 050 BL5 is some sort of fuse or PTC.  I haven't check.  My guess is it's 500mA.  Maybe Belling Lee?

A fuse is very likely to pop with such abuse!

[lars-musik]

Thanks Rob! I just tested the DC/DC isolators with my DMM and realised that they all seem to be damaged - there's continuity betwenn V+ (in) and V+(out) and V-(out).... That can't be good, so I guess we'll ditch the whole thing.

[Rob Strand]

I just tested the DC/DC isolators with my DMM and realised that they all seem to be damaged - there's continuity betwenn V+ (in) and V+(out) and V-(out).... That can't be good, so I guess we'll ditch the whole thing.

The device might wire the ground through even though the modules are isolated.

I'd buzz out the fuse and the 0R resistor.   If they are blown try replacing them and power it up.  You never know it could still work.

[lars-musik]

Hi Rob, the fuse is all right, so is the resistor. I replaced the obviously blown cap, hooked it up and got an immediate distress signal from the PSU.

I beeped through the DC/DC isolators again and all four of them have continuity on between both INs and (+ and -) and the + OUT. I guess this is really a lost cause. Smelly, too.

[Rob Strand]

I guess this is really a lost cause. Smelly, too.

Time to bail-out  .