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Grand Master
Jul 10, 2018
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Sydney, Australia
Joey's analysis of my 2931

Well turns out mate that it's the tripler inside the flyback that has failed, it had damaged an SMD IC in the regulation section plus the 5 pin regulator and zener protection diode, H-Drive transistors and vertical IC, this is supposed to shut the chassis down but as the IC was shorted it kept driving.
I replaced the blown bits and within a few seconds it blew everything again, so I took your flyback out and put it in another old one of these chassis that's in real bad shape I only use for testing flybacks, anyway within seconds it shutdown like it was supposed to.

I don't have a good flyback spare and the after market ones just aren't any good, also the SMD IC that blew on yours isn't readily available I only found them parts on an old parts chassis, so many hours later ( over 5 today ) still no working chassis !! damn frustrating these things, every time I work on one it only cements why I don't do the MS293xx series anymore.

I do have a nice fully working spare that I wasn't planning on parting with if you want to go that way.

So essentially I FUBAR'd my 2931 - note to self, never turn on a chassis ever again without the H/V connectors from the yoke connected.

I received the working spare chassis on Thursday and to say I was careful when putting on the chassis is an understatement! :D :D

Turned her on... and BEAUTY! SHE WORKS!!! :D :D

After the excitement of seeing it alive again, reality came back down when I couldn't stretch the image wide enough


See how I was on HSIZE MAX but I'm still missing a big chunk on the right and a little on the left?

On a good note, the video clearly shows that the wavy corners are no longer present. So it must've been the chassis all along and not the yoke!

I guess as a bonus, I have an impregnated yoke. There's still some buzz that occurs when you start up the cab, but seems to disappear after a while.

So after searching for information all over the place, I couldn't for the life of me figure out why I couldn't get the image to expand. I tried the H-Drive pot (didn't change it too much). I tried the "extension" menu with additional settings (hold down a button for 3 seconds) but there was no setting. I know on the 2930 there was a pot HSL for horizontal size limit, but I couldn't find anything for this chassis.

When in doubt, what do you do? RTFM :D :D. I found the service manual of the 2931 - low and behold there's commentary there talking about entering a "factory adjustment mode" which is different to the "extension" mode


So I did exactly as the manual said to, hold down all three buttons for 3 seconds and VOILA! Factory Mode


Scrolled through the menus and what do you know, I came across a H-LIMIT option :D (I went from 18 max to 34).


What did increasing it from 18 to 34 do? Edge to edge image!


Spent another hour or so trying to get the colour right and this was as good as I could get it


And of course, it wouldn't be my cab without this game on the test bed :D



This was a very good weekend for the cab - unlike a few weeks ago :D

Next to do is fix the corners properly and then do this exercise all again for "31khz".


Grand Master
Jul 10, 2018
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Sydney, Australia
Spent some time on the public holiday to configure the monitor.

Here's the cross stitch of the monitor before any convergence work..


After about two hours worth of mucking around and me $h**ting myself, this was the best I could do (also ran out of convergence strips)


The bottom left could probably use another one or two strip, but there's definitely a difference on all corners, especially the top left! In game, it's a lot more forgivable and nowhere near as noticeable as it used to be.

Of course, the back view :) - yep, I got happy with silicone. I really don't want to be taking this monitor out anytime soon


She's finally back in the cab and I had a good gaming session on Wednesday night.

Was about to drop a few coins on it yesterday until this happened.....

Turned the cab on, noticed something was off when I saw the monitor and upon checking the colour chart... blue channel is missing!! FMD it just doesn't stop! This cab really hates me! hahah


At this point in time, given the history of this cab, I almost rage quit and threw in the towel, but I stepped away for 10 mins, regathered as I knew I had a spare neck board for this chassis - I already came across this issue with the other blast city and I replaced the neck board.

Back on the "workbench" (aka floor :D), I desoldered the two wires on the neck board and swapped them around. Turned it on and voila! I got blue but no red! ARRRGGGHHHHH


My last resort before emailing Joey was to reflow the 3 transistors responsible for the 3 rgb channels on the neck board.

Turned the cab back on with the reflowed neck board and bob's your uncle! Everything is back to normal! Thank f**k for that!


Got her installed again (back didn't like it) and dumped a few credits on DOJ!


For now, arcade universe is balanced again and I really hope there's no more challenges for this blast city ever. I've been told by a few people to sell it off, but given the amount of work I've put in, it'll most likely be sticking around for a few years :D


Grand Master
Jul 10, 2018
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Sydney, Australia
Because working on two blast cities over the last year with a lot of tears is never enough.... guess what I picked up last night??? :D :D


Yep! I'm back for one more go! hahaha

The Honda HRV is surprisingly large inside! I've now done two cab trips with my Dad's little hatch back (Astro city and now Blast City).



I haven't turned the cab on just yet to see what's wrong with it, but I was told no image - so I'm assuming another dead 2931.

Overall, the condition is much better than I thought (apart from the little tiny rust area on the coin chute door), but it's definitely MUCH better than the two I got at the beginning of the thread and won't be needing a repaint (thank f**k for that! :D)

Got her lined up next to her older sibling and the path to my OCD pair collection continues (2x chewlix cabs, 2x noirs, 2x astro cities, 2x blasts and 2x new net cities - still need to get my 2nd one)


Like the other blast, this will most likely be another shmup cab - but I am yet to decide.


Grand Master
Jul 10, 2018
Reaction score
Sydney, Australia
Another update on my wonderful adventures with the Blast City! :D :D

I ended up getting some repro artwork - mostly for the blast, but a few random bits and bobs


The repro blast cp artwork is ok, but not 100% perfect, it will do the job for my purposes


Another artwork I got made up was the little red decal on the bottom right hand side of the blast city - it's the little touches that bring the cab back to life :)



Lastly, the one outstanding thing on the blast the I painted was the side decal, like the CP repro decal, it's not 100%, but for the purpose of completion, it's perfectly fine.


Outside of the Sega stickers behind the blast, the shmup blast city is now pretty much complete. I won't be touching that any more - no more screen removal, screen rotating etc.... so I thought :D :D

Now onto where the fun begins :D

I sent off the chassis for repair and came back nice and fresh - Joey's exact words were "I think you will be happy with this one". So of course I was pumped! New caps were of course installed which is always a good thing.


I decided to record the first power up and I'm glad I did as everything was captured haha

*may contain some offensive language - viewer discretion advised* :D

View: https://www.youtube.com/watch?v=DMS4w84LHnQ

As you see, I got a nice little zap and the monitor did not show any picture :( so back to square 1. When the OSD was pressed, there was also no image. When I turned the screen pot to 3/4 of the max I got a very feint image with raster lines visible and the image was washed out started to look grey. The neck glow is a nice bright orange.

I needed to confirm if the chassis was faulty or it was something else.

Remember the part where I said I never had to take off the shmup monitor out again... well of course I was wrong! :D


I completed a number of tests to tr and determine where the fault was. My baseline is my vertical Blast as that's working perfectly.

  1. Wired the Horizontal monitor/chassis on a working Vertical Blast - still the same black, completely dark with image only visible when you increase the screen pot from 3/4 and above
  2. Wired the Vertical monitor/chassis on the Horizontal Blast - works fine displays the image as normal
  3. Swapped the Vertical chassis onto the Horizontal monitor, tested on the Vertical Blast - same symptoms, completely dark. Didn't increase the screen pot as I didn't want to screw up the settings on this chassis as it's already configured and working
  4. Swapped the Horizontal chassis onto the Vertical monitor, tested on the Vertical Blast - chassis works, it was extra bright screen pot due to turning it up on the other Horizontal monitor to get the raster lines
I was then led to this post on Arcade Otaku (https://forum.arcadeotaku.com/viewtopic.php?p=523900#p523900) so I inspected the R732 of both chassis

  1. 2931 originally paired with A68KZN696X (labeled 2930 on the sticker - originally the "Tate)) has Orange, White, Gold, Gold = 3.9 Ohms and works fine on my Tate cab
  2. 2931 paired with A68LBT696X (labeled 2931 on the sticker - originally the "Yoko") has Brown, Black, Gold, Gold = 1 Ohm and is very dim on the Yoko cab.

At this point in time, I think I've come to the conclusion that my tube is shot and the absolute last thing I can do is to try and rejuvenate the tube. Fortunately, I might have a lead on someone that can lend me a rejuvenator and I'm hoping we have the right connections - will update once it happens.

Lastly the zap! When I first received the zap, I initially thought it was because the metal plate wasn't earthed. I looked at the other blast and there was no earth connector on any part of the metal plate, so the only thing I could think of is the switch itself is no longer insulated or it's broken for the AC line to get to me. I inspected the switch and this is what I found


Hit up Mouser to find the closest thing to the model number and what was a 10 dollar switch because a 60 dollar order because I refused to pay 24 dollars for shipping LOL

Brand new switch was just dropped off by the UPS man.


I'm hoping I can work something out with the rejuvenation this week, we'll see how we go. However, I'm also hoping I might have a lead for a spare tube as a worst case scenario.


Grand Master
Jul 10, 2018
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Sydney, Australia
Got my hands on a CRT tester on Wednesday night to try out thanks to hwaygo on discord - it's the BK Precision 490 and fortunately for me, it had the correct CR23 connector :)

Never having done any of this stuff before, I watched multiple videos of what we needed to do, but at the highest level, we needed to set up the heater voltage, the G1 and then RGB cut offs.

There's a website called http://tubular.atomized.org/ which provides the values for a significant number of tubes - of course it doesn't explicitly state my tube. My tube is an A68LBT696X, this only site only has an LBS, so I thought one letter wouldn't be too bad. I base lined the G1 on 70v.


Got everything all wired up, triple checked, it was time to give it a go and see what happens


Had a very nice orange neck glow which mean the tube was physically still OK and the vacuum on the neck was still good - not the dreaded blue glow which meant oxygen has gone into the neck.


According to what we were testing, all three guns were clearly "bad"


So hwaygo and I went through the process of "clean and balance", re-testing and eventually hit the "rejuvenate" function. We did this a number of times until it finally tested in the "good" region


At this point, we decided, all we could do was "test" and see what happens. Wired up the chassis, turned her on and VOILA! We have picture!


It needed calibration, but it was great to see an image on this tube considering when I got it, it was so dim that it was black.

That's where the excitement finished - I got called for a Major incident at work so we had to stop our testing, but thankfully hwaygo left the tester at my place to allow me to do some further testing/rejuving. I left the game running but by the time I checked in (must've been an hour or so later), the green and blue guns significantly faded :(


I then had the opportunity to test a little further last night and one thing I noticed when I set the G1 to 70v was when I was trying to adjust the RGB cut off in the setup, it wouldn't move no matter how far right I increased the dial, even maxing it out. So this time, I set the G1 to 50v like most of the other tubes. I redid the whole process multiple times blasting the tube - at this point I really had nothing to lose, so I blasted and blasted :D

After all that zapping, I finally managed to wire it all back up and I've got picture again! This time, I'm very apprehensive as I didn't have much luck the previous time, so all I could do was sit and wait to see what happens...

Colour charts look good



In game looks good too


It's definitely on the "dim" side, but I'll take "dim" over no picture any day of the week :)

I had it on for about 4 hours last night just looping through the attract mode of the game and it seemed to hold up

View: https://www.youtube.com/watch?v=aGOBRT-tEt4

I've turned the cab on this morning from 7:30 and will leave it on running just before I go to sleep and see how it holds up before putting it back in the cab. If it holds up, then safe to say it won't do what it did the first time around and I can use it until I find a replacement tube. If it fades, then I need a replacement tube quicker as I can't do a rejuve process each time I turn the cab on.


Grand Master
Jul 10, 2018
Reaction score
Sydney, Australia
Sad day unfortunately... the tube gets dimmer and dimmer by the day :(

Here you can see just how dim the tube is compared to my other blast. I had to turn off the light on the top left (tired tube side) as you wouldn't have been able to see any image on screen :(


Now I'm on the hunt for a replacement tube - Joey said he's got a couple of tubes that are 100% on the crt tester, but it's getting it from Perth to Sydney that would pose the biggest challenge. The eastern states, I can organise Bill, but from Perth is a little more challenging.

My options are:
  1. Find a proper blast city tube A68LBT696X (2931 tube) or A68KZN696X (2930 tube)
  2. Find a donor tube in one of the following consumer tvs and do a yoke swap
    1. Toshiba super crystal 2988UE
    2. NEC SF-6804
    3. Symphonic model ST427F (don't think this is found in Australia,think this is an American only brand)
  3. Find an NEC XM29 PVM which is apparently a direct swap - yoke and all! But doing this would probably cost way more than the price of the cab :D
Somehow, I think it might be a while before I get this cab back to 100%

Another alternative could be install an MS9 (back mounted) and live with the bezel gap, or if I find a flat screen, install that. Either way, it's going to take some patience (which I'm not normally good with :D)