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The 7800 Mod Mess Mixup Fixup - pt. 1


Nathan Strum

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The 7800 really needs a nickname. The 2600 has several: Heavy Sixer, Vader, Jr., etc.

 

The 5200 is... uh... the Boat Anchor? Well, we'll go with that for now. But the 7800? As far as I know, it never got a nickname.

 

So I'm going to bestow one upon it: The Wedge.

 

It's cool. It's hip. It's trendy. And I'm sure that nothing ever nicknamed The Wedge ever had any bad connotations whatsoever. :ponder: 

 

Anyway, it's time to 7800-up my blog with my next fixit project: repairing a 7800. My first!

 

Not my first 7800. My first attempt at repairing a 7800. This is someone else's 7800.

 

Now then, some time ago, someone sent me a pile of consoles to fix. I just wish I could remember who that was... ?

01-whose_7800.jpg

 

Guess I'll never know. But I do remember what's wrong: after a lightning storm (which took out two 2600s which I previously fixed here and here), the joystick buttons on the left port didn't work, and the right port didn't respond at all. So the first suspect is the RIOT. Also, there was a mod installed (by some random person on eBay apparently) that had composite and HDMI that...

 

Wait.

 

An HDMI mod?

 

That can't be right. There are no HDMI mods. There are HDMI scalers, adapters, converters and transcoders... but not "mods".

 

Huh.

 

Anyway, the owner, let's call him "John", didn't like the dull (aka "normal" on a 7800) colors of the composite video, and said the HDMI looked terrible. So he was interested in having that improved, in addition to fixing the other problems.

 

Anyway... let's take a look-see underneath. Video/audio mod jacks on the left. Magic "turn on the HDMI mod" switch on the right.

02-mystery_switch.jpg

 

And a close-up of the HDMI port. Yep. There's an HDMI port there. Weird. And extra holes for... ventilation?

03-hdmi-yi-yi.jpg

 

Well, let's see if it works. First - checking my monitor's composite input with color bars:
04-ntsc_composite.jpg

 

Annnnnnd... nothing from the 7800. But man... that is one BRIGHT LED. Obnoxiously so. But at least it's getting power.
05-nada.jpg

 

Next, I'll try HDMI. To set up my LG 4K monitor, I'm first sending my color bars through a Gefen scaler. Besides scaling S-Video video very cleanly, you can also make sure you're keeping the proper, original aspect ratio. Very robust options menu with lots of adjustments too.
06-ntsc_through_gefen.jpg

 

It's a bit bulky, runs quite warm, and tends to be kind-of expensive. But I've used these at work for years, and never found a better, more full-featured scaler (outside of professional broadcast gear). And presently, Amazon has used ones for around $100. Dirt cheap!

09-gefen_front.jpg
10-gefen_back.jpg

 

So the HDMI into my monitor is properly set up, but no love from the 7800's HDMI output:
07-nada_hdmi.jpg

 

Did I mention how obnoxiously bright the LED is? And it color-cycles, too. That may need to get replaced.
08-stupid_bright_led.jpg

 

Well, it ain't gonna fix itself. Let's open 'er up and see what's what.
11-time_to_open.jpg

 

Umm... okay. That's a thing. I guess.
12-what_lurks_inside.jpg

 

It's a bit of a hodge-podge. Like a leftover wire bin at an electronics flea market. The soldering is... amazing.
13-scrap_wire_bin.jpg

 

Well, there's your problem!™ At least one of them. That wire will need to go back.
14-well_theres_your_problem.jpg

 

Let's look under the hood... if we dare.

15-the_horror_beneath.jpg

 

The HDMI "mod" is actually a cheap AV to HDMI converter from Gearbest. The product page is no longer there, but you can find it on Wayback. (If you Google "AY29J Mini AV to HDMI Converter" it will still return a picture of it. Basically, it's one of these.) Basically, they removed the board from the converter, desoldered all of the jacks (except HDMI) and grafted the output from the composite mod to it. And pulled power from somewhere.
16-the_mawed.jpg

Small wonder the thing worked in the first place. The wiring is... amazing.

 

The rest of the AV mod looks like a mix of this and this. And hot glue. Lots of hot glue. I mourn the poor RF modulator that died a horrible death for this.
17-never_too_much_hot_glue.jpg

 

But wait! Another loose wire. What might this have been haphazardly attached to?
18-well_theres_your_other_problem.jpg

 

Looks like the center pin of the video jack. Well, that would explain the complete lack of picture everywhere.
19-probably_there.jpg

 

It's not long enough to easily reattach, so I grafted a wire onto the end of it, and heat-shrunk some tubing onto it using my new toy, which I'm totally digging. Fast, quiet (for a heat gun), and precise. And less fussy than using the soldering iron for heat-shrink tubing.
20-video_fix.jpg

 

Then I soldered the other broken wire back onto the switch of destiny. It magically enables HDMI somehow. Maybe it supplies power to the converter?
21-switch_fix.jpg

 

Would it work? Much to my surprise, it fired right up. The composite picture isn't awful. Or rather, it's not any worse than my RF 7800.
22-ta-dah.jpg

 

Color looks pretty-good. A touch brighter than my RF 7800.
23-color_chart_composite.jpg

 

Did I mention how bright that LED is? And so... many... fingerprints.
24-whats_with_all_the_fingerprints.jpg

 

Well, let's take a look at the HDMI output. It works... but it's pretty awful. It just stretches everything out to 16:9, and there's a ton of artifacts from over-sharpening.
25-color_chart_mod.jpg

 

Ugh.
26-color_chart_mod_closeup_1.jpg

 

Ick. But then, this is composite video, being barfed through an $11 converter.
27-color_chart_mod_closeup_2.jpg

 

Here's the 7800's composite scaled through the Gefen. Notice the appropriate aspect ratio:
28-color_chart_gefen.jpg

 

But blowing up composite is never pretty. The Gefen makes no attempts to hide anything.
29-color_chart_gefen_closeup_1.jpg

 

Lots of fun bleeding from the composite out.
30-color_chart_gefen_closeup_2.jpg

 

And for comparison's sake, here's the same composite out through a RetroTink 2X-Mini:
31-color_chart_tink.jpg

 

It sharpens the video a bit more than the Gefen, but it's also stretching it - something you can't alter with the 2X-Mini. Maybe the 5X-Pro is better. One of these days I should order one, and do a shoot-out with the Gefen.
32-color_chart_tink_closeup_1.jpg

 

Tons of bleed. Garbage-in, garbage-out. Yeah... we can do better than this.
33-color_chart_tink_closeup_2.jpg

I haven't checked the audio. I probably should before I get any further into this.

 

So, what's up next for this 7800? Well... here's a peek:
34-next_up.jpg

 

Stay tuned, as we rip this thing's guts apart, and put it back together. Properly.

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Wow, great write up Nathan!  I feel bad for the poor sap who owns that 7800 and actually *paid* for that HDMI 'mod'. :roll:  Great breakdown of the poor quality of the changes; maybe we can use one of those fingerprints to track down the culprit? :idea:;) 

 

Looking forward to seeing what it looks like with the UAV mod.  Hopefully it includes a different LED. 👁️ 🚨;) 

 

PS I'm pretty sure the nickname for the 5200 is "Big Sexy", or at least that's what I've always called her.. uh, I mean 'it'. :P  

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Hehe...(Not even kidding) Ya know my second car was a '76 Triumph TR-7.  Once I was shooting an arrow at my friend,..I mean he was supposed to deflect it or catch it, (we used to play our ninja games back then), but he sidestepped it and it stuck in the fender of my TR-7.  So I guess I mainly remember it as the second car I shot an arrow into...and the nickname this mechanic gave it;  The "Rolling Coffin",  Because of issues and frame damage he said it wasn't safe...But then it got stolen,  Well sold (by a dealer) to a guy who wrote a bad check...the dealer then went bankrupt, so yeah it wasn't exactly the luckiest car.  

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