32X Squeal Fix

Backstory

Everything I do has a little story to go with it.  If you just want to know how I fixed the Squeal issue, skip to "Resolution" below.

I bought my 32X brand new when Sega had given up on the platform and the stores were liquidating them.  I think I paid about $30 for it, then took the free copy of Virtual Fighter out of the box, went across the street to a used game shop that hadn't yet caught on and sold Virtual Fighter for $35.  So essentially I got paid $5 to take the 32X off of the store's hands.

A Tale of 2 32X's

It's probably not a wonder then that I didn't have very high expectations of the 32X, and simply dismissed the video distortion and audio squeal it introduced.  I legitimately thought it worked that way.  At the time I only had a Genesis Model 1, so I misplaced the spacer that it comes with for use with the Genesis Model 2.  About 3 years ago I went to a local used game shop and bought a whole 32X for $25 just to get the stupid spacer so I could use it with a Genesis Model 2.  The newly bought 32X was scratched up and didn't look as nice as my original, so I put the newly bought one away and continued using the one I had bought new.

You Mean It's Not Supposed To Sound Like That?

Connecting the 32X to an OSSC greatly amplified and magnified the video noise and audio squeal to the point where it was damn near unplayable, so I started searching around to see if anyone knew how to improve the situation.  I found a lot of articles and a lot of supposition, but almost nothing in the way of a solution.  One thing stood out, however.  Some users were reporting that their 32X systems didn't add any audio or video noise at all.  That got me thinking, so I pulled out the 32X I had recently bought used and swapped it out for my shiny original, and I couldn't believe it.  There was no discernible audio or video noise at all!

Conjecture

So I had one "good" 32X and one "bad" 32X.  In all of my searches for a solution, three suggestions kept coming up, but there never seemed to be any followup on a solution.

1. Power

It was suggested in a couple of places that insufficient power was a possible cause.  In my case I have been using a "Trio M2" power adapter from www.retrogamecave.com.  I would expect that if the power supply was the problem, the problem would exist with both 32X modules, but it only affected the one.  I did try switching back to the original power bricks for both the Genesis 2 and the 32X, and also alternating, but there was no detectable difference.

2. Capacitors

The next thing that came up in a few places was the fact that the 32X had one particular "Low ESR" capacitor.  ESR is the resistance a capacitor has to being charged.  High ESR can cause odd failures because a capacitor may not charge up until after a delay, or the power supply may not be able to overcome the ESR to charge it at all.  At the time I didn't have an ESR meter, so I just shotgunned the whole module, replacing all of the capacitors with brand new ones, and making sure to use a "Low ESR" capacitor in the appropriate place.  This had zero effect on the squeal or the video distortion.

3. The Inductance Coil "L7".

The lengthiest discussions I came across involved this part.  The service manual hosted at Console5.com describes L7 as "CHOKE COIL 330UH LHL13TB331K".  There were a number of users reporting that they could actually hear the coil physically squeal directly from the console even with the audio output turned off.  This was not the case with me - I only heard the noise and saw the distortion through the AV output.  After reading through several discussions, and at least one user who swapped it out without any improvement, I decided to give it a shot, but also to keep my options open.

32X main board. The original L7 inductance coil circled.

The Plan

In addition to a direct replacement, I decided to try a couple of others to see if the problem was just poor component choice.

Mouser actually sells the exact part described in the service manual.

https://www.mouser.com/ProductDetail/963-LHL13NB331K

In reading its description the thing that really bugged me was that it was described as "unshielded".  It seemed reasonable to me that a shielded inductance coil might yield better results, so I looked for coils with similar attributes - focusing mainly on inductance value, max current and maximum DC resistance.

This one was pretty close:

https://www.mouser.com/ProductDetail/994-RFS1317-334KL

This one was almost exact so I decided to try it even though it was the wrong package type (surface-mount rather than through-hole):

https://www.mouser.com/ProductDetail/81-MBH12282C-331MAP3

Today I finally got around to trying them out.

The first thing I did was to replace the original with the new LHL13TB331K.  It seemed like there may have been some small improvement, but the audio and video distortion were still terrible.

The next one I tried was the 994-RFS1317-334KL.  This was the shielded coil with a slightly lower DC resistance value, but was otherwise rated the same as the original part.  The footprint was too narrow to fit directly so I had to very carefully bend the legs of the coil to fit onto the board.  There was a definite improvement with this one.  The volume of the distortion was cut about in half, but it was definitely higher-pitched.  It was better but still awful.

Resolution

By the time I got to the 81-MBH12282C-331MAP3, my hopes were not very high.  Fortunately the vias had solder pads on the top of the board as well as the bottom so I didn't have to do anything too crazy to attach it.  There's an exposed ground point directly under the spot where the coil sits. This isn't a problem for the through-hole inductors, but would have caused a short on the SMD inductor, so I covered it with a tiny corner of black electrical tape before placing the new coil on top of it. There wasn't a lot of room to maneuver but I managed to get some good solid connections.  When I fired up the 32X for the first time I couldn't believe my eyes and ears.  It was dead quiet - not even a hint of the squeal or visual distortion.  For a moment I thought I may have blown out the audio circuit, but then the game started up clear as a bell.

32X with the 81-MBH12282C-331MAP3 inductance coil installed as a replacement for L7 to fix audio squeal and video distortion.

Now I can obey Admiral Akbar, storm the imperial Death Star, and wipe out enemy fighters without distortion!

But Why?

Someone on the shmups forum challenged me to try to explain why this worked when the parts were technically the same.  My initial thought was that the new part was just "better", but the question made me consider other possibilities.  Before going into this I thought shielding might be the answer, but, then, of course 994-RFS1317-334KL did not eliminate the squeal.  Since it reduced the volume of the squeal, I'm inclined to think the shielding played a part, but it was definitely not the "smoking gun".

Possibility 1: Vibration
In my research I read that physical vibration is a factor with inductance coils.  At least one example corroborating this is the Turbo Express where the coils are covered in gray epoxy - presumably to dampen vibrations.

The shell of the LHL13TB331K and  994-RFS1317-334KL have a kind of skirt at the bottom that makes contact with the board in a circle all the way around the coil. When I first tried replacing the coil with the new LHL13TB331K, I tried to make sure to get full contact with the surface of the PCB, but in fairness, I was just eyeballing it. While it didn't appear to do much good it's possible it wasn't completely flush with the board and was allowing for vibration. With the 994-RFS1317-334KL, the legs were too far apart to fit through the vias for the original coil and putting right-angle bends in them prevented the skirt of the coil from making contact with the board at all. With the 81-MBH12282C-331MAP3 (SMD), basically the entire bottom of the coil is a conductor. I had to put a little triangle of electrical tape over an exposed ground point under the coil to keep it from shorting.  So the entire underside of the coil sits flush against the board with a piece of electrical tape serving as a cushion- it's possible that full contact and the additional cushion is allowing the PCB to absorb all of the the vibration and that's the real difference.

Possibility 2: Inductance Value
The other thing is the inductance variation between the parts. When I measured the original, and the LHL13TB331K replacement, they both registered 0.3mH. It isn't exact, but it's at the low end of tolerance. The 994-RFS1317-334KL measured 0.33mH - exactly as rated, and it _did_ seem to make an improvement. Since my component analyzer doesn't have an easy way to measure SMD parts, I used DMM probes to measure the MBH12282C-331MAP3 and got 0.36mH. I assumed the DMM probes were going to introduce a certain amount of inductance by themselves and that might be throwing the reading off so I dismissed the difference. But since the question was asked, I went back and measured the LHL13TB331K using the same probes and got 0.3mH - meaning that the probe wires weren't throwing the measurement off as I had assumed, and the SMD coil does have a significantly higher inductance value.

The LHL13TB331K is rated at 330uH with a tolerance of 10%, meaning anything from 297uH to 363uH _should_ technically be acceptable, and the MBH12282C-331MAP3 is still within this margin, but in practice at the opposite (high) end compared to the original part.  From what I've been reading about coils, this shouldn't make that big of a difference, but who knows?

So, to recap, although the MBH12282C-331MAP3 has the exact same ratings as the original coil, it's also shielded, has nearly 20% more inductance, and is almost definitely making better physical contact with the PCB.

I have no intention of fussing with that 32X any further now that it's working perfectly, but logically if you wanted to try fixing it without replacing the coil, you could try doing something to dampen the coil by fixing it to the board, like using a soft epoxy to fix the coil to the board.

3DO FZ-10 Rescue

The 3DO isn't a great platform.  It's also not a particularly bad one either.  I've only ever met one person who professed nostalgia for it (specifically the game "Twisted").  There aren't really any "killer app" games for it.  Supposedly its version of Need For Speed is superior to the Playstation version in some way (I never bothered investigating the rumor).  There are a handful of interesting games.  Star Control II, a couple of Wing Commander titles, "D", etc... Regardless it's still a great piece of gaming history and represents an alternate view of the way things may have gone.  Comparing it to the other consoles of its time, the best way I can sum it up is to say that the 3DO iterated where the Playstation and Saturn innovated.  Like the Atari Jaguar, the 3DO was more of an extension of the 16-bit arc rather than the start of a new 32-bit trajectory.

I'm in the process of getting ODE's for all of the platforms I can, and this was next on my list.  Optical Drive Emulators (ODE's) are all the rage in the retro gaming community right now.  Think of them like flash carts for your disc based systems.  The ODE either replaces or bypasses the spinning disc drive and loads games directly from solid state media like SD cards or USB drives.

Attached to every review of an ODE is usually a sage treatise on the limited lifespan of optical drives and how they're getting rarer and rarer.  These drives have moving parts and that means friction which means wear, so logically they will eventually break down, but I think the notion that all optical drives are going to suddenly die enmasse in the next 20 years is just amateurish prognostication and sensationalist tripe.  I love these things because I can have the entire library (or at least large chunks of it) on a console at once. That's pretty much it.  I'm not worried about drives dying.

Someone going by MNEMO from Russia makes and sells a 3DO USB Host Controller.  The prices vary wildly, with one of the cheaper being the version for the FZ-10.  I once passed up an opportunity to buy an FZ-10 for about $50 when Best Buy was liquidating them. _Facepalm_  At the time I already had an FZ-1, and my impression of the FZ-10 was not good - if they reduced costs by replacing the tray loader with a lid mechanism, it seemed likely they cut corners in other aspects as well and to my mind, cheaper meant less reliable. The reality seems to have turned out the opposite as the FZ-10 is now pricier than the FZ-1 on Ebay.

What I needed was a cheap FZ-10, so I watched Ebay for broken "for parts or repair", and eventually this one popped up:

The only thing the seller reported wrong with it was the missing lid latch, but of course it "wasn't tested with any discs".  I asked the seller if the machine displayed an image when plugged into a TV and turned on.  He sent me a photo of the startup screen displaying, so we haggled on price and I got a pretty decent deal (about 1/3 of the going price of one in working condition).  I figured if the drive was toast, the console would probably still work just fine with the ODE.  The visible dirt on the outside of the console was a little worrisome, but I thought "how bad could it really be?"...

When the machine arrived the first thing I did was try to turn the spindle motor by hand.  It barely turned and felt like it was grinding - probably a lost cause.   Next I opened the case up and took a look inside.  I found a couple of splashes of mud on the PCB, the lid switch was stuck, and the CD drive mechanism was stuffed full of fuzz, hair and what looked like dessicated insect parts.  I removed the CD drive mechanism, and detached the spindle motor.  After giving it a good brushing with a toothbrush, I gave it a shot of silicone lubricant on the spindle shaft and after a turn or two, it spun freely.  After looking closely at the spindle, there's some kind of tension spring pressing against the shaft and I *think* that's what was gunked up.  So with the motor turning freely I thought I might have a chance of getting it working - as long the motor hadn't been burned out when it was seized up.

Next I disassembled the rest of the CD drive mechanism, cleaned each part with a toothbrush and naptha to clear away all of the grit and fuzz.  I also used soap and water on the plastic bits.  I carefully cleaned all of the existing grease from the laser transport rails, the laser and the gear teeth using a toothbrush and q-tips, then replaced it with a fresh application of lithium grease.  Once reassembled, I made sure to turn the grooved shaft that moves the laser mechanism by hand putting it all the way through it's range of travel, and sure enough it hung up part-way through because I had missed some grit in the groove, so I took it apart again, and used a stiff piece of paper to completely clean the groove, re-lubed everything and reassembled it.  This time it went all the way through its range of travel without getting caught.

Once the CD drive was back together, I gave all of the ribbon sockets a shot of Deoxit.  I also gave the lid switch a shot of it and moved it until it stopped sticking.  I took a lint-free swab and carefully cleaned the laser lens with 91% isopropyl. With the drive plugged back in, I plugged the 3DO into my monitor, popped a game disc in, turned it on, and to my utter surprise the CD drive came to life and loaded a game without a hitch!  I listened carefully for grinding noises or any other signs or damage or remaining grit in the mechanism, but if anything it sounded quieter and smoother than my FZ-1.  Let's see a first or second generation PS1 do that!

So at this point I had a fully working console, but what I could see of the motherboard was filthy.  I've seen "dirty" consoles before, but never one with actual dirt in it.  I say "what I could see" because about 2/3 of the motherboard is covered by a large thick RF shield.  Based on what I could see, I knew I wanted to take this thing outside and give it a good blow out with my air compressor rather than getting my workspace dirty, but when I unscrewed and removed the RF shield, this is what I found:

No, it's not what you're thinking - unless you were thinking it was two lovely mud dauber nests.  Somehow the minerals in the mud weren't enough to interfere with the proper operation of the console!  These nests were so solid that a full blast from my air compressor barely knocked any of them off.  I had to carefully peck and blast at it for about 15 minutes to get most of it off.  Once it got down to the last little bit I had to turn the motherboard upside-down over a sink, and scrub it off with distilled water and a toothbrush.  Holding it upside-down helped minimize spreading mud around the board.

After getting all of the visible mud off with distilled water, I gave it a good scrub with 91% isopropyl, and then a shot of naptha.  I used q-tips to spot clean any remaining filth, then sprayed the whole board with Deoxit to clear away as much of the oxidation as possible.

The bottom half of the console had evidently been submerged in water at some point as the RF shield was covered in huge splotches of rust, and the rust had embedded itself into the plastic of the case.  I soaked the bottom half of the case, including the RF shield in CLR for about 30 minutes then gave both a good scrub with an SOS pad, and a final wipe down with naptha.

With everything cleaned, dried and reassembled, I removed the spring from the door mechanism so it would stay shut without being clasped, popped a disc in and validated that I hadn't damaged anything while cleaning it.  As before, the game loaded immediately.  I played for about 30 minutes to make sure there weren't any overheating issues.

Since it's not in my nature to leave well-enough alone, I opened it back up to perform a 240p video mod on it which also went over without a hitch.

Externally mounted DPDT (On-On) switch to select 240p/480i.  Internally, pin 52 of the video encoder has been lifted from the board.  The center pole of the switch is wired to pin 52, the top pin is wired to pin 55 (55 is connected to Vcc so this pulls pin 52 high), the bottom pin is wired to pin 52's landing on the motherboard.

I found a replacement part for the clasp:
https://kpcomponents.co/products/cd-player-door-latch

That link is not the exact one I bought - I actually found one on Ebay that arrived more quickly but since Ebay removes listings after a certain age, it seemed pointless to link to it.  These seem to be pretty standard, though.  I've found many different listings for them, but I've only found them in one size.  Just search Google Images for "cd player lid latch" and you'll see half a dozen of them. Unfortunately I wasn't able to find a consistent part number or model number.  I did, however, find two other CD players in my house that happened to use the exact same connector so these are all over the place.  If you can't find one for sale, you might have luck going to a garage sale, Goodwill or some other second hand store and picking up a cheap CD player to cannibalize for the part.

Once I popped the spring back in and inserted the new lid latch, the restoration was mostly complete.

New generic lid latch installed in the FZ-10.  Works and looks original.

The only thing still missing was the plastic lens piece that the "ready" and "access" LEDs shine through.  Unlike the lid clasp, I didn't find any remains of the piece inside the case.

The lenses that catch the light for the Ready and Access lights were missing when I bought it.

The LEDs are bright enough that edges of the holes still light up green and red.  But unlike the lid clasp, the LED lens piece is clearly purpose made for the FZ-10 so the only way to get another one would be to cannibalize another 3DO.  After thinking it over for a while I decided on a solution. There's a rectangular bracket-like structure on the underside of the case, so I cut a piece of packing foam (the soft squishy kind that some monitors and TVs ship in now - I think it's the same kind of stuff that pool noodles are made of) to fit snugly in the bracket, then I covered the top of it with silicone sealant.

Foam piece with silicone sealant pushed up through the holes

Next I gently pushed it up into the slot so the silicone barely started to squish through the top.  The surface tension resulted in the convex curve like the originals had.

Not bad for a first attempt.  If I had used crystal clear silicone it would probably have been a nearly perfect match.

I let the silicone cure, then carefully augured holes in the foam under the opening to let as much light as possible shine through.  The result was pretty decent for a first attempt.  There are two things that would have made it better.  First, I should have used a silicone that would cure crystal clear.  I just used whatever I had on hand which turned out to cure a little white and cloudy.  Second, I should have made sure the top surface of the silicone was perfectly smooth before pushing it up into the holes.  There were streaks in it which are visible up close.  Had I done those two things I think this would have been indistinguishable from the real thing from the outside.

The result is not a perfect match, but it "works" and it's a lot better than open holes IMO.

After all that, it feels more like I've rescued an abused and abandoned puppy rather than refurbished a piece of Ebay junk.  I'm still blown away by the fact that this console is still working.  These things seem to be built like tanks.

Now all that's left is to get that USB Host Controller.  I've placed my order, but these things are (apparently) hand made and there's only one guy doing it, so it may be a long wait.