Working on restoring a Sony WM-D3  Professional cassette recorder, has cracked center gear "Lever gear assy" a common problem with this series and other DD series. Figure start also doing pictures of repair progress, instead of just video

The plastic ring on the lever assy has opened up because of the plastic shrinkage. Because of the shrink, there is no way just to join the ends and glue it together. Even if you manage to pull the ends together and glue it, there would be enough stress  to again break the bond. The reason why it split in the first place. As far as reduced the diameter of the inner metal disc will requires special lathe tools. Using a hand file is also very tasking as the disc is probably steel and has some decent thickness. Maintaining a constant diameter on the disc while filing the edges is close to impossible, which may result in increased wow during playback. And inserted a small filler teeth from some other donor gear wheel and have even used epoxy based glue to recreate a teeth in the gap. While both these methods are known to work they seem they just don't hold up as well, yes I try both. This here is the best way, as I done this fix to other and still runs fine after a year.  

Now to clean and prep and glue back the center gear.

1. First have to removed the pastic ring from the disc. Be carefully in removing the outer plastic gear. It is quite flexible, but still be very careful as you don’t want the gear teeths to deform at random places.

2. Cut now opposite the already cracked side, make one more cut. The plastic material is difficult to cut and so use a very sharp/new exacto blade to cut it.  Plus, cut it in such a way that the cut is between two tooth.

3. Arrange both of them around the metal disc so that both the gaps are equal. You have to place the gear assembly back in the walkman to complete this step. Align the existing teeth to the teeth next to the vacant one. Fortunately because of the size of the adjacent gears, skipping one teeth on the center gear seems to work fine. Check for any excessive pressure, sure be nice and smooth, when you turn it in the transport. Will take around 5 minutes to get it align perfect, don't glue yet as you are just trying to set the position.

4. Now to glue, first I use plastic primer, then I used a combination of glue and epoxy to bond the gear pieces, makes for a stronger bond. After primer I use CA- rated glue, or locktite ultra, which is like a gel and take a while to set. Never use instant crazy glue!! Make sure you use a thin layer and thin it even, you just want to glue in the gap and let sit overnight. Then will apply a thin layer of epoxy resin.

5. Also have to watch out for the plastic supply reel pinion had also shrunk and cracked. This gear is supposed to be press fit on the metal spindle/rod attachment. Because of the discontinuity due to the crack, the gear would make lot of clacking noise. The only way of closing the gap is made the diameter of the inner hole on the pinion larger. I used a drill to make the inner diameter bigger. This would defeat the press fit design, but thats the intention anyways. Just glued the spindle tight to the pinion so that it doesn’t slip during rewind.

6. Take the rest of the gears and spring off the transport and clean it clean it thoroughly, remove any factory lubricate is, and reapply new lubricate, only where needed.

i used this method on my dc2. but i didn't get the best allignment with the two spaces and just ended up with two clicks instead. bother. then one day i dropped the darn thing and now it's just royally screwed. big dent in the side, which i was able to bend out. but the click is way worse and it does that thing where the power will just cut out. i haven't gathered the nerve yet to fix it again, those tiny springs, ugh, and those tiny see through retention ring things. i had begun the process one day a few weeks ago but then i remember those tiny springs and i was just kinda, reminded how much i missed my silver dd30.

but i had used your guide to help me though. thanks.

You have to be exactly dead on the alignment, one tooth space, you have to check for any excessive pressure, and have the transport completely out and also take the spring out for the "Lever gear assy" and reinstall without during the aligment process, so it stay in the down postion, then the turn the rewind takeup reel and make sure it smooth.

The DD series is not for the faint of heart and reason why I don't recommend anyone buying them.

Thought about it, but may leave the gear to small and won't hit the rewind, or forward gear right, plus may cause excessive wow and flutter.

Now to fix the broken mic input jack, you will need to removed the two screws on the top PCB by the one has the grounding claw and the other by the head preamp, they are two longer screws then you can slide cover off and desolder old jack, you need to have a replacement jack is a three pin jack. 

This is how it looked before rebuilted, how it came to me wasn't working at all no movement in the transport, had cracked center gear and various other issues.

After complete rebuilted, was a complete mess before with food crumbs and was very dirty, door won't stay shut and broken mic jack with no sign of life, now works like brandnew and with no clicking sound.

You showed it on this video:

http://www.youtube.com/watch?v=SWeaLP3PEHw

That was mines, this one for someone else. Figure this time do pictures and step by step directions

Thank you retrodos for your kindness to take time and explain the issues about this.

I have to wait a while to get money .Then i would like you to fix it, if you have time.

I forgotted to say i live in sweden.But i,m from finnland ,neighbour contry to sweden.

Here people dont even remember walkmans,atleast i have not met no one yet.

Wich is a shame on such a good machines.I,m still happy for my in mint condition mini disc sony n10 mz net md 10 years anniversary edition magnesium metal.But i want to collect walkmans its also nostalgic memories of my childhood time.