Doin' the Hacky POKEY
Entry posted by Nathan Strum in 7800 repair
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Some time ago, I was planning to order a Concerto cart for my 7800.
I didn't have a POKEY to install in it, but figured I'd either order one from Best, or wait until the HOKEY was available to order the Concerto.
Around that same time, James mangled the daylights out of a POKEY, trying to remove it from a poor, unsuspecting Ballblazer cart. I offered to attempt to fix it, if he wanted to send it to me. So he did, presuming it to be DOA anyway (he subsequently bought a replacement POKEY from Best).
I didn't have anything to test it in though (and I wasn't about to mangle my own Ballblazer cart for testing), so I used the excuse of sort-of now having a POKEY to order my Concerto.
A year-and-a-half later, I finally got around to attempting to fix the chip.
Now, I didn't hold out much hope for success. I figured at best, I'd have a 30% chance of this working.
Thirty. Percent.
I think that was pretty optimistic, if you look at the pictures of the aftermath linked above.
When it arrived, I didn't think it looked all that bad.
Although that was the pretty side. This side...
Yeah. Ouch. It looks like James desoldered about 2/3 of the chip successfully, then just lost patience and tried ripping it out the rest of the way. (Just speculating... I'm sure James would never get impatient. 
)
So first things first - a little desoldering wick and some tweezers to clean-up and gently unbend the pins:
So that all cleaned up pretty well, and just left me with one completely-broken-off pin, and one half broken one (third from the left):
So to fix it, I decided to graft on a donor pin from another (dead) chip. I have a pretty-good collection of them now, from fixing up a few 2600's. Here's one from one of John's consoles:
For ease-of-access sake, I picked a corner pin that looked particularly stout, and chipped away at the resin with side cutters until I got a nice amount of the leg exposed:
Then I broke off the chunk underneath. Neatness does not count here - I'm just making sure I don't damage the pin that I want.
Then a couple of quick bends and presto! Donor body part!
Now I had to expose the top of the leg on the POKEY. I carefully scored the resin with a razor saw:
I had to be careful not to cut too deep and damage the part of the leg I needed to get to:
Once scored, I figured I could just pop the piece off with a pair of side-cutters, as I'd done on the donor chip:
No such luck. I spent about 20 minutes gradually chipping and scraping my way down to metal:
Next, I cleaned and tinned the contact:
And used a spare chip socket to line up the donor. Sorry for the blurriness. iPhone 6S. (I refuse to upgrade.)
A quick touch or two with the soldering iron, and the leg was attached!
Next, I had to fix the half-broken pin (again - third from the left):
I forgot to take a picture of clipping the donor pin off, so I craftily Photoshopped one. Nobody will ever be able to tell the difference!
I then forgot to take a picture of clipping off the broken half of the POKEY pin, and again was forced to show off my mad Photoshoppery skillz:
I used the socket again to line them up, and grafted the new pin on top of the old one:
Done!
And the other side, because of course I remembered to take a picture of something I didn't need to:
So would it work? Remember - I'm giving myself a 30% chance of success, so I'm not expecting much. First though, I figured I'd better see if the Concerto cart itself actually worked. I'd never tested it, POKEY or not.
I popped it into my 7800 with a fresh SD card (since I can't find my old ones), fired up a 7800 test binary, and presto! No POKEY! Because I hadn't installed it yet. But hey - the cart works. I tried a few other binaries just to make sure, including Ballblazer (which was deafeningly, and unsurprisingly, silent).
Time to install the Hacky POKEY! Opening the shell, I somehow managed to break off a tiny little alignment pin. Bummer. But that's what screws are for.
I gently (or gingerly even) seated the POKEY in the socket, and carefully squeezed it into place:
Everything fully seated, and no bent pins! I considered throwing a little JB Weld over the corner to tidy it up, but I kind-of like the look. It has a history to it now. And also, I didn't want to spend the time on it (thirty percent chance of success and such).
Before doing anything else, I checked continuity from the chip through the board. Just to make sure that if the chip still worked (thirty percent), that the signal paths were good.
I then reassembled the cart...
And fired it up!
Would it work? Well... first I had to wade through the Concerto's startup sequence:
Looks pretty good for stock RF.
Then I loaded the test cart binary...
And... nothing! Still no POKEY.
Thirty.
Percent.
But then I thought, "What if the test binary doesn't see the POKEY because it's in the Concerto?" The Concerto isn't exactly 100% compatible. So, I fired up Ballblazer...
And was met with some reassuringly jamming tunes! The POKEY worked! Take that, other 70%!
You'll just have to pretend this is video. But the music is there.
Just to be sure, I fired up Commando:
And that worked, too! (Again, you'll have to pretend.)
So I managed to revive James' mangled POKEY! And now I have a working POKEY for my Concerto cart!
Unless he wants it back. 
That would be awkward. I'm kind-of attached to it now.
Anyway...
And yes, my 7800's video is a little bit lot on the dark side:
But my monitor is calibrated properly for NTSC:
It's hard to get a good picture with my iPhone (refuse to upgrade), but yes, the PLUGE is clearly visible in person:
Not sure if adding a UAV mod would address the brightness issue, but I'll likely try that at some point.
After I experiment practice on John's 7800, that is. You think this POKEY was a mess? Just wait.
But that's a story for another time... 
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