andrewhess wrote: > I've had mine (Modwright Transporter) for over ten years now. Would it > make sense to prophylactically replace those caps? If so, would I keep > the same values or upgrade them?
Hi Andrew, certainly makes sense to replace them. The voltage rating should be at least 10V but there is no harm done if you choose one that would tolerate 16 or even 25V. Eventually, 5V is what they constantly need to handle, but a bit more margin would not hurt. Higher voltage ratings mean bigger size though. The capacitors are connected in parallel so their combined capacity adds up to 1360µF. A discharged electrolytic capacitor has a low resistance at first which causes some load on the other components. The higher the capacity, the longer this low resistance stands (as charging it up takes longer). So don't use crazy values like 10000µF even though these are available. The circuit is just not designed for it. There's a third value to keep in mind which is the temperature rating. As far as I know there is 85°C and 105°C, that's the maximum allowable ambient temperatures they can stand. The higher the safer, but again, higher tolerance might end in a larger size. Be aware that you need to mind the correct polarity of the capacitors. Putting them in reverse might blow them up, or at least cause them to fail quickly. Choosing two new 680µF, or a single one having 10V/1500µF is reasonable. I would definitely not recommend to go beyond 2200µF, it might damage other parts of the power supply board. If you can, let the new capacitors stand further away from the board as there is a diode near their home position that gets very hot during operation, and heat has them age quicker. Here is an example of a ModWright Transporter that I did a maintenance run on recently. Not pretty but efficient: 36983 36984 This power supply will last way longer than the original setup, I'm sure. I was actually a bit disappointed by the mess they made when they modified the Transporter. The display flat flex connector on the front panel board was falling apart because it was not handled properly, and the connector for one of the main power rails (set of two purple wires between the toroid and the MW board) was burning up internally due to bad contact. The way the 5V power supply is pushed aside to make room for the overkill toroidal transformer did not appear very safe. Wiring between the MW board and the analog part of the Transporter mainboard was a mess, too. But anyway, after fixing it all, the owner confirmed the sound is positively worlds apart from the stock Transporter audio quality. So apparently it's worth it. Good success on your repair! Cheers, Joe +-------------------------------------------------------------------+ |Filename: IMG_20211019_214018 (copy).jpg | |Download: http://forums.slimdevices.com/attachment.php?attachmentid=36984| +-------------------------------------------------------------------+ PN me if your Boom / Classic / Transporter display has issues! Blog: https://www.blogger.com/blogger.g?rinli=1&pli=1&blogID=5053304027701850753#allposts ------------------------------------------------------------------------ JoeMuc2009's Profile: http://forums.slimdevices.com/member.php?userid=23131 View this thread: http://forums.slimdevices.com/showthread.php?t=100509
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