bosoz PSU help!?

[cowanrg]

well, i dug up 16 MUR1520's.

i desoldered the 1N4005's, and sure enough, half were 0 resistance on one board. so, they were shorting out the circuit. im going to replace all of them with the MUR1520's and hopefully that will work!

i already tested all the MUR's and they all work ok with the diode tester, so they should be ok. i have to repair the traces though too , but that wont be too hard.

[cowanrg]

sigh.

i replaced all the 1N4005's with MUR1520's and still the same problem. however, thanks to the light bulb suggestion, no more destroyed boards and diodes.

i have all the secondaries and primaries from the transformer routing through a euro style connecting block. i have triple-checked it, and it doesnt seem to be the problem. when i take the PSU boards away and just hook up the transformer (with the connecting block), everything works fine and i get the voltages i should be getting. i turn it on, get the right voltage, the LED lights up on the connecting block, and the light bulb is off.

as soon as i wire in the PSU board (just one of them), i turn it on, and a get a nice bright light bulb. very sad. i have tested all the resistors and diodes in circuit, and all seem to be ok. i dont really have a way to test the transistors, could they be causing a short? i also tested the caps, and they test great too.

any ideas? i even used nylon parts to mount the board in the case, just in case i was getting a short from the standoffs (which i wasnt). this is really really confusing. i can take pics of the setup if needed.

[kilowattski]

Do the fets share the same heatsink? Are the heatsinks grounded? Did you put insulators between the transistors and the heatsink?

[cowanrg]

they do not share the same heatsink.

the heatsink is not grounded, but it is isolated from the FET and not touching anything.

[cowanrg]

hum, well, i checked ALL the zeners, the resistors and replaced the fets with new ones.

it doesnt light the light bulb anymore, it actually runs! but, i am only getting -60. on the + side, its only giving me like 8v or something. so maybe the 9610 died? ugh, this is so annoying because it all worked just fine before i started putting it all in the case.

[jleaman]

I know how you Feel Cowanrg Just one step at a time and if you feel frustrated take a breather for the night. But always go back to the last thing you did and make sure you check it over maybe use a variac ?

[cowanrg]

well, unfortunately i dont own a variac

im actually not THAT frustrated quite yet. i have made some progress, and i suspect its the fets. i had the boards just sitting out for a month or so on a shelf, so there was a good chance they could have shorted out or something. and im not 100% sure the replacement fets i had are good either. i need to sit down and test all the fets i have to make sure they all work ok. i did notice a few bad zeners too. its just a LOT of things going wrong with those boards...

im almost tempted to just completely repopulate them (minus those MUR1520's though).

[kilowattski]

Maybe it's time to invest in an antistatic mat with the wriststrap.

http://www.electroflash.org.nz/produ...htm#Antistatic

[jleaman]

Id say invest in a variac first all your work has impressed me and i think it would be worth your whyle to buy one.. i did there not expencive either..

j'

[kilowattski]

What good is a variac if your blowing up parts with static. Remember, Jason, the horse goes before the cart. There are ways to get around not having a variac. There is no way to get around blown parts. Antistatic storage bags are a good idea for boards until they are used.