So after discovering leaky capacitors in my Sega Rally twin power supplies, I decided to check my Daytona twin PSUs as well. Sure enough they were having a good leak, with corrosion building all over the copper traces on the circuit board.
Amazingly the power supplies were running okay, they were in spec as far as voltage goes and no visible ripple detected on my scope. There was definitely a discernible fishy smell emanating from the machine though.
I decided to keep the machine as original as possible and rather hack in some PC power supplies or go through the hassle of speccing new PSUs, I decided to have a go at recapping them. The supplies in question are the Sega 400-5221 series, which I believe were mostly common to Daytona machines, not sure if they were used in any others.
I checked the traces and they were still fairly solid, so I didn't have to do any repairs there, I just removed all the electrolytic caps and gave the board a good clean with isopropyl alcohol and then distilled water, using a small brush with both liquids.
Cap removing:
Always seemed to be leaking electrolyte around the negative pin:
Some of the caps had voltage ratings of 25v which were generally a little more expensive than other higher rated caps, so I picked the higher voltage rating equivalents, usually 35v. I also chose the better brands such as Nichicon, Rubycon and Panasonic, all with 105c temperature rating and around 5000 hour lifetimes minimum but some with 10000 hours.
There are two aluminium heatsinks across the board with the power transistors and diode bridges mounted to them. These needed to be removed to access the capacitors. I found it easier to unsolder the components from the board while still attached to the heatsinks, as the mounting screws were often blocked by the capacitors. A bit tricky but do-able.
Otherwise, recapping was fairly straightforward. The only extra servicing I did was put a bit of solder on the power plugs, they hadn't dry jointed but they didn't seem to have much solder on them so I thought I'de toughen them up. I also cleaned off the old dried up heat transfer paste and re-applied some new paste on the heatsinks where they are mounted to the case.
Shiny new caps fitted:
To finish off I PAT tested them and hooked them up to a dummy load to make sure the 5 volt line levels were okay before plugging them back into the Daytona twin.
I was certainly quite alarmed at how much they had leaked, and pretty much every single capacitor had started to leak, yet everything seemed normal.
Normal that is until one day the corrosion is bad enough to cause a catastrophic power supply fail and send my lovingly repaired Daytona Model 2 stacks to video game no-longer-working land. So I'm pretty happy I caught them in time.
I'm now bullet proofing all my Model 2 stacks with new caps too now.
So I'll say it again, check your power supplies and stacks for leaky caps!
Steve.
Here is a cap list of the original capacitor values:
C5: 220uF 10v
C6, C7: 470uF 200v
C20, C21, C22, C25, C26, C27, C28, C29: 4700uF 10v
C18: 1000uF 35v
C11, C19: 470uF 25v
C12, C16: 47uF 25v
C17: 10uF 25v
C24, C31: 0.47uF 50v
Best selected alternatives from RS Components:
C5:
Rubycon 220uF 35V dc Aluminium Electrolytic Capacitor, Through Hole 8 (Dia.) x 16mm +105°C 8mm 3.5mm
Stock no.:725-8919
C6, C7:
Nichicon 470uF 250V dc Aluminium Electrolytic Capacitor, Through Hole 25 (Dia.) x 35mm +105°C 25mm 10mm
Stock no.:270-256
C20, C21, C22, C25, C26, C27, C28, C29:
Panasonic 4700uF 10V dc Aluminium Electrolytic Capacitor, Through Hole 16 (Dia.) x 20mm +105°C 16mm 7.5mm
Stock no.:708-3608
C18:
Rubycon 1000uF 35V dc Aluminium Electrolytic Capacitor, Through Hole 12.5 (Dia.) x 25mm +105°C 12.5mm 5mm
Stock no.:725-8912
C11, C19:
Rubycon 470uF 35V dc Aluminium Electrolytic Capacitor, Through Hole 10 (Dia.) x 16mm +105°C 10mm 5mm
Stock no.:749-7202
C12, C16:
Rubycon 47uF 35V dc Aluminium Electrolytic Capacitor, Through Hole 6.3 (Dia.) x 11mm +105°C 6.3mm 2.5mm
Stock no.:704-8074
C17:
Rubycon 10uF 50V dc Aluminium Electrolytic Capacitor, Through Hole 5 (Dia.) x 7mm +105°C 5mm 2mm
Stock no.:704-7860
C24, C31:
Wurth Elektronik 470nF 50V dc Aluminium Electrolytic Capacitor, Through Hole 5 (Dia.) x 11mm +105°C 5mm 2mm
Stock no.:839-9358
lix2019-11-11 01:17:41
Amazingly the power supplies were running okay, they were in spec as far as voltage goes and no visible ripple detected on my scope. There was definitely a discernible fishy smell emanating from the machine though.
I decided to keep the machine as original as possible and rather hack in some PC power supplies or go through the hassle of speccing new PSUs, I decided to have a go at recapping them. The supplies in question are the Sega 400-5221 series, which I believe were mostly common to Daytona machines, not sure if they were used in any others.
I checked the traces and they were still fairly solid, so I didn't have to do any repairs there, I just removed all the electrolytic caps and gave the board a good clean with isopropyl alcohol and then distilled water, using a small brush with both liquids.
Cap removing:
Always seemed to be leaking electrolyte around the negative pin:
Some of the caps had voltage ratings of 25v which were generally a little more expensive than other higher rated caps, so I picked the higher voltage rating equivalents, usually 35v. I also chose the better brands such as Nichicon, Rubycon and Panasonic, all with 105c temperature rating and around 5000 hour lifetimes minimum but some with 10000 hours.
There are two aluminium heatsinks across the board with the power transistors and diode bridges mounted to them. These needed to be removed to access the capacitors. I found it easier to unsolder the components from the board while still attached to the heatsinks, as the mounting screws were often blocked by the capacitors. A bit tricky but do-able.
Otherwise, recapping was fairly straightforward. The only extra servicing I did was put a bit of solder on the power plugs, they hadn't dry jointed but they didn't seem to have much solder on them so I thought I'de toughen them up. I also cleaned off the old dried up heat transfer paste and re-applied some new paste on the heatsinks where they are mounted to the case.
Shiny new caps fitted:
To finish off I PAT tested them and hooked them up to a dummy load to make sure the 5 volt line levels were okay before plugging them back into the Daytona twin.
I was certainly quite alarmed at how much they had leaked, and pretty much every single capacitor had started to leak, yet everything seemed normal.
Normal that is until one day the corrosion is bad enough to cause a catastrophic power supply fail and send my lovingly repaired Daytona Model 2 stacks to video game no-longer-working land. So I'm pretty happy I caught them in time.
I'm now bullet proofing all my Model 2 stacks with new caps too now.
So I'll say it again, check your power supplies and stacks for leaky caps!
Steve.
Here is a cap list of the original capacitor values:
C5: 220uF 10v
C6, C7: 470uF 200v
C20, C21, C22, C25, C26, C27, C28, C29: 4700uF 10v
C18: 1000uF 35v
C11, C19: 470uF 25v
C12, C16: 47uF 25v
C17: 10uF 25v
C24, C31: 0.47uF 50v
Best selected alternatives from RS Components:
C5:
Rubycon 220uF 35V dc Aluminium Electrolytic Capacitor, Through Hole 8 (Dia.) x 16mm +105°C 8mm 3.5mm
Stock no.:725-8919
C6, C7:
Nichicon 470uF 250V dc Aluminium Electrolytic Capacitor, Through Hole 25 (Dia.) x 35mm +105°C 25mm 10mm
Stock no.:270-256
C20, C21, C22, C25, C26, C27, C28, C29:
Panasonic 4700uF 10V dc Aluminium Electrolytic Capacitor, Through Hole 16 (Dia.) x 20mm +105°C 16mm 7.5mm
Stock no.:708-3608
C18:
Rubycon 1000uF 35V dc Aluminium Electrolytic Capacitor, Through Hole 12.5 (Dia.) x 25mm +105°C 12.5mm 5mm
Stock no.:725-8912
C11, C19:
Rubycon 470uF 35V dc Aluminium Electrolytic Capacitor, Through Hole 10 (Dia.) x 16mm +105°C 10mm 5mm
Stock no.:749-7202
C12, C16:
Rubycon 47uF 35V dc Aluminium Electrolytic Capacitor, Through Hole 6.3 (Dia.) x 11mm +105°C 6.3mm 2.5mm
Stock no.:704-8074
C17:
Rubycon 10uF 50V dc Aluminium Electrolytic Capacitor, Through Hole 5 (Dia.) x 7mm +105°C 5mm 2mm
Stock no.:704-7860
C24, C31:
Wurth Elektronik 470nF 50V dc Aluminium Electrolytic Capacitor, Through Hole 5 (Dia.) x 11mm +105°C 5mm 2mm
Stock no.:839-9358
lix2019-11-11 01:17:41
