Twin Famicom - error 26

[oare]

I recently bought a Twin Famicom, but it has a strange problem: it keeps spitting error 26 (unable to save) with disk games. It loads them fine, though.
The drive the unit came with is a 3206. I tried swapping it with a known-working 7201, but it exhibited the same behavior.
On the contrary, when I put the 3206 drive in an fm-power-04 equipped FDS, it worked flawlessly.
So it is safe to rule out the drive (and the disks) as the culprit.

Compared to most TF I've seen pictured, mine has a couple of extra chips (d4001bc and d4013bc) on the power board, which are apparently used to control the write line. So I thought the problem might be coming from there.
Unfortunately, I could only find very little info about those. There is a page on Japanese site Bakutendo where the author reports he successfully bypassed the chips by cutting them out from the circuit, but if possible, I'd rather keep this solution as a last resort.

It is a shot in the dark, but I think I'm going to try and replace the 4001 4013 chips if I can get ahold of them.
However, I'd really appreciate any form of insight on the matter. Does anbody have an idea of something else that could be causing the issue?

Thanks in advance!

Edit: to be completely clear, the error 26s appear in a normal usage scenario, i.e. when trying to save my proression in a game. I am not attempting to copy disks.

[fredJ]

I am not an expert in these things and haven't heard of this problem before... Which version Twin Famicom do you have (turbo? red? black?)
I am thinking swapping the power board would indicate if that is the problem and would be simple.
The turbo console has a different power board than the other versions though.

It does seem that most problem with the twin are because of the power board....
But if something triggers some unknown anti-piracy protection, who knows what it could be?

[oare]

Thank you for your reply.
The TF I have is an AN-500-B (black model 1).

Unfortunately, I don't have another unit to try and swap the power board. That would definitey help.

Anti-piracy kicking in where it shouldn't is also my guess.
Cables seem in order, and I don't see any suspicious traces on the board.
So I can't think of any other potential culprits but the 4000 series chips. I've ordered replacement parts so I'll be able to try that route in a few weeks.

But I'm sure there are angles I'm missing, so any opinion is welcome!

[fredJ]

Could it be that your twin requires a specific matching disk system model, that has the same anti-piracy as the power board?
Did you buy the twin famicom with the original non-working disk drive? Or did someone fix it up.

[oare]

Thanks again for your input.

The TF appeared untouched, the drive belt it came with was there in all its molten glory when I first opened the device.

Anyways, I decided to open it again this morning in order to check for bad traces or corrosion.
One thig led to another, and I ended up removing the 4000 series chips and bridging a few points in order to re-establish a direct connection to the disk drive from the extension port. The good news is that now, it works. No more error 26. So it seems the culprits were those chips after all.
I also removed a resistor that was connected between (I think) vcc and one of the disk cables.
The reason I removed it was that it appeared to be part of the protection circuit, but I really am not sure. It's labelled r223 on the attached picture.
Would anybody by any chance know what it could be?

Another issue I was having was that sometimes, the drive would stop reading disks out of the blue, without outputting any error message. It only happened every now and then, but was annoying because the only way to get away from it was to reset the device. I initially thought the issue was related to the error 26 behavior, but it still happened after I removed the protection chips, so it was definitey something else.

I noticed some corrosion on one of the legs of the 2C33, so thinking it might be that, I replaced the chip with one I scavengend from a spare hvc-023.
The issue hasn't occurred since, but I haven't had the time to perform estensive tests so I'm not sure it is resolved yet.
One side effect if the procedure is that the TF now says "Nintendo" instead of "Famicom" when booting in disk mode.
Bah, I can live with that (although I kind of liked the font used for "Famicom").

Anyways, there still is another issue I need to solve: sound.
Sound from games that have extra hardware (such as Akumajo Densetu/Castlevania III) is really unbalanced. Some sound effecs, like the whipping soung in Akumajo Densetsu, are muffled to the point they're barely audible.
I think this is a well documented issue, however, so I'll dig into the available resource and hope for the best...

This thing didn't cost me a lot (the equivalent of usd30) but it's really turning into a time consuming endeavor.

[Pikkon]

For the muffled sound you can try removing a cap.

http://www.sega-16.com/forum/showthread.php?20737-Repair-Log-Sharp-Twin-Famicom&p=481320&viewfull=1#post481320

[fredJ]

The TF appeared untouched, the drive belt it came with was there in all its molten glory when I first opened the device.

Yes, I just tried a different disk system with a twin famicom with extra chips, and it was no problem, so that shouldn't be an issue.

Anyways, there still is another issue I need to solve: sound.
Sound from games that have extra hardware (such as Akumajo Densetu/Castlevania III) is really unbalanced. Some sound effecs, like the whipping soung in Akumajo Densetsu, are muffled to the point they're barely audible.
I think this is a well documented issue, however, so I'll dig into the available resource and hope for the best...

The few *cart* games that have extra sound have low sound on a twin.
I actually don't like the removing cap thing. I think the cap is there to give the console a smoother sound overall. The original famicom has a screetching sound that can be painful to listen to.
I don't think it is a huge deal though, I recommend to increase the volume on the TV (about half of max).

Or option 2, to use a famicom or AV famicom for that particular game. It probably sounds better anyways than a modded twin is capable of and probably much easier to mod a cheap famicom than to start messing with the audio of a twin, IMO.

This thing didn't cost me a lot (the equivalent of usd30) but it's really turning into a time consuming endeavor.

In the last couple of months I have had a bunch of twins dying... I think it is their caps...  But I don't know for sure yet.

[oare]

Thank you two fro your input.

For the muffled sound you can try removing a cap.

http://www.sega-16.com/forum/showthread.php?20737-Repair-Log-Sharp-Twin-Famicom&p=481320&viewfull=1#post481320

I gave a shot at removing the cap, but put it back afterwards. The sound did indeed become a little clearer in the highs, but I'm not settled on what I prefer.
My main problem is with sound levels being too low in general, and on cartridges with extra sound hardware in particular.

The few *cart* games that have extra sound have low sound on a twin.

Yes.
Twin Famicom itself has, in general, the lowest sound output of all Famicom variations.
There's a guy who did fairly extensive tests on a bunch of different Famicom models. The results can be seen on the following page:
http://gamers-high2.seesaa.net/article/124773283.html
Scroll down to the last picture (blue sound graphs), you'll see from left to right:
1, Unmodded Famicom through RF
2, AV modded Famicom (mono)
3, AV modded Famicom (false stereo)
4, Twin Famicom
5, New Famicom
6, Famiclone

Twin Famicom is the one that starts a little after the 1m00s line. It clearly shows how low the sound output is.

Or option 2, to use a famicom or AV famicom for that particular game. It probably sounds better anyways than a modded twin is capable of and probably much easier to mod a cheap famicom than to start messing with the audio of a twin, IMO.

The thing is, I specifically bought the TF in expectation for my recently ordered NESRGB board - and Akumajo Densetsu is one of the games I absolutely want to play in RGB!
I think I'll just give a shot at bypassing the existing amp and wire the NESRGB one, and see how it goes.

In the last couple of months I have had a bunch of twins dying... I think it is their caps...  But I don't know for sure yet.

I did a routine cap replacement when I got mine. The motherboard was quite dirty, and in overall pretty poor condition. There are only a few electrolytic caps in there, so it didn't take long.
Give it a try!

[fredJ]

I got message from the broken Twin Famicom...
Another power board problem.

Second time it happened. Previous time was a customer on this forum actually.



This part of the DC plug breaks off and stops leading current...
Is this a common problem , anyone knows? What causes it, or is it just time?

[oare]

It is a problem I've seen mentioned multiple times on Japanese sources so it seems like a widespread issue.
It can happen to the power connector, the video connector and the audio connector.
Some people recommend to systematically resolder those joints on Twin Famicoms as a precaution.
The only explanation I recall reading was that the connectors aren't held very firmly, so plugging/unplugging ends up causing cracks.

[80sFREAK]

I got message from the broken Twin Famicom...
Another power board problem.

Second time it happened. Previous time was a customer on this forum actually.



This part of the DC plug breaks off and stops leading current...
Is this a common problem , anyone knows? What causes it, or is it just time?

It's common on FR-2(paper, not fiberglass) material without vias.