TG16: Shorted wires at the voltage regulator

SmokeMonster · 02/24/2015, 04:05 AM

I made a huge mistake the other day...

I got broken's RGB amp finally working with my GBS-8200, and had it roughly hooked up for testing. I removed the test setup, organized the wiring, and set everything up for the permanent install. At this point though I swapped my +5 and negative connections to the voltage regulator without realizing it. I powered it up, which of course messed up the console (possibly the RGB amp too).

It's now outputting jarbled composite video and erratic audio, and no RGB. I can tell that it's loading games, but obviously something was damaged.

Any ideas on what may be the point/points of failure? Would this have blown the 7805?

I had just recapped her and the video and sound quality was beautiful, so I'd love it if I could it working again. Of all the cables to reverse though...

poponon · 02/24/2015, 04:33 AM

from my understanding reversing the polarity on a voltage regulator will blow it

mickcris · 02/24/2015, 05:04 AM

You possibly blew more than one thing if you sent 5v though the ground. I would assume that 5v regulator is still ok as you say it seems like its loading games. Its easy enough to check its output with a meter.
But the amp is probably blown.

pulstar · 02/24/2015, 08:28 AM

First thing to do is take the RGB amp out of the equation and see if you get a stable picture without it.

When you say you swapped the +5v and GND lines, you mean the lines going to the RGB amp, not physically switching the 7805 around so I'd say most of the damage is probably isolated to the RGB amp. Bit strange to have distorted audio though, which points to another fault as well.

The 7805 is working otherwise the console wouldn't come on at all, whether it's outputting a stable voltage is a different matter. Get a meter on the output and test it.

Edit:

It's possible you could have screwed the HuC6260 or some other components if you had the RGB lines hooked up to the EXT port. Was it a regular PC Engine or a Duo of some sort? I'm guessing a Duo.

SmokeMonster · 02/24/2015, 12:37 PM

Thanks for the help everyone.

Quote from: pulstar on 02/24/2015, 08:28 AMFirst thing to do is take the RGB amp out of the equation and see if you get a stable picture without it.

Yes, that was my first thought as well and that is how I have been testing the composite video since the accident.

Quote from: pulstar on 02/24/2015, 08:28 AMWhen you say you swapped the +5v and GND lines, you mean the lines going to the RGB amp, not physically switching the 7805 around so I'd say most of the damage is probably isolated to the RGB amp. Bit strange to have distorted audio though, which points to another fault as well.

I tapped the +5v and ground for the RGB amp straight off of the 7805 (backwards unfortunately), so it was the first point of contact.

Quote from: pulstar on 02/24/2015, 08:28 AMThe 7805 is working otherwise the console wouldn't come on at all, whether it's outputting a stable voltage is a different matter. Get a meter on the output and test it.

I'm only getting 0.4v output from the 7805, so I'll start by replacing it.

Quote from: pulstar on 02/24/2015, 08:28 AMIt's possible you could have screwed the HuC6260 or some other components if you had the RGB lines hooked up to the EXT port. Was it a regular PC Engine or a Duo of some sort? I'm guessing a Duo.

This was a US Turbografx-16. I did have the RGB amp installed with its RGB inputs coming from the ext port.

pulstar · 02/24/2015, 01:46 PM

Yeah, first thing to do then is replace that 7805 and see if that remedies the situation. I'm surprised you're getting any life out of it with only 0.4v on the output.

SmokeMonster · 02/25/2015, 02:19 PM

A replacement 7805 is on the way. Fingers crossed.

SmokeMonster · 03/17/2015, 07:21 AM

I installed the new 7805 and it did make an improvement but the audio and video are still severely distorted. I imagine that a chip is damaged. Time to start hunting down a replacement motherboard.

poponon · 03/17/2015, 10:14 AM

Sorry to hear that man. hopefully you find a new motherboard soon

pulstar · 03/17/2015, 01:59 PM

That's a shame

Personally, when I do mods I try to colour code stuff, especially power wires (Red for +5v (or whatever voltage I'm tapping), black for GND), that way it's less confusing. Hope you don't have to search too far to find another unit.

thesteve · 05/08/2015, 11:41 AM

I would suspect 6260
Wouldn't be a bit surprised if that's the only failure

SmokeMonster · 05/08/2015, 12:47 PM

Is there anyone with the skills (and a spare HU6260) that could repair it for me? I might be able to, but it would be pushing the limits of my soldering skills.

NecroPhile · 05/08/2015, 12:54 PM

I don't know if he has a spare chip, but Steve can fix anything.

thesteve · 05/08/2015, 02:35 PM

i should have the chip as well
you in the states?

SmokeMonster · 05/08/2015, 02:45 PM

Quote from: thesteve on 05/08/2015, 02:35 PMi should have the chip as well
you in the states?

Yes, I'm in the US. How much would you ask for the chip, or could I commission you to install it for me?

pnauts · 05/09/2015, 08:19 AM

Curious that the chip was damage.
I know someone who reverse 5V polarity from a PC engine to my RGB board on expansion port and it blow the fuse.
Hopefully there was no damage on the console nor the amp of the board.
did you check your 5V is correct ?

thesteve · 05/09/2015, 10:05 PM

if the chip is ok, then i wont swap it
i too am surprised it took damage
the amp i expect took damage, but i have done that to other chips (incorrect schematic) without causing any harm