7805 not working after replacing

[zmaster18]

So a Famicom board I was messing around with doesn't work anymore. I replaced the 7805 and it's not outputting power. The input and ground pins on the 7805 actually read voltage on my multimeter, but the output pin has nothing.

Any ideas?

[Pikkon]

Did you check the fuse.

[zmaster18]

There is no fuse on a HVC-CPU-07. I think this one is probably toast.

[Pikkon]

Hmm,maybe the transistor is bad.

If you want you could grab a usb cable,find the positive and negative,then solder the positive to the input and output of the 7805 then negative to the ground of the 7805 and plug into a pc or anything that takes usb and see if you get any power to the famicom.

[ericj]

Replace the 7805 with a new one, the part you used may have been bad.

[zmaster18]

I used a brand new one. I have about 5 more brand new ones as well, but i don't think the 7805 was the problem.

I actually broke the Famicom after soldering on it. I did unplug it and tried to discharge it by flipping switch on after the power cable was removed. I think I broke it by not waiting long enough after discharging it and then soldering on it.

I also replaced the big 1000uf cap and that did nothing. What could this accident have done to the famicom that won't even let a new 7805 work properly?

[ericj]

You shouldn't need to discharge it. Can you post pics of the power board? Could be a bad resistor, broken trace, etc.

[famifan]

What could this accident have done to the famicom that won't even let a new 7805 work properly?

7805 goes with built-in short circuit protection. It could effectively prevent output of power in such cases.

[ericj]

If the 7805's output pin shows no voltage, it should be replaced. Check for any shorts on the board before (and after) soldering in a new one.

[P]

Damage from a static electric discharge is possible too.

[zmaster18]

Damage from a static electric discharge is possible too.

That's what I think it is. So would this permanently damage the IC chips on the board? 

[famifan]

Damage from a static electric discharge is possible too.

almost all 7805 contains built-in ESD (electric static discharge) protection (typically that implies *human body model*: short 2kV impulse from 100pf capacitor discharged through 1.5kOhm).

not sure about ancient ICs from 70-80s.

Also, damage from improper soldering could likely occured than damaging from ESD. Say overheating ICs for few secs with 40-100W soldering iron is not the right way for soldering
Post Merge: January 14, 2016, 04:55:50 am

Damage from a static electric discharge is possible too.

That's what I think it is. So would this permanently damage the IC chips on the board? 

it can't be. Unless you intentionally discharge piezo ingniter element from typical lighter to IC outputs directly.

famicom was built from old good TTL logic ICs. They're almost immune to electrostatic discharge when compared with early CMOS logic. (Late CMOS logic always contains built-in ESD protection, but i can't vouch for ICs produced in 70-80s)

[kid8bit]

Fuse

[zmaster18]

Fuse

no fuse