I have a device that is missing the original power adapter: a NEC TurboGrafx-CD dock. The original specs: 5.5x2.5mm, center negative, 11v, 1.53A. It’s ‘80s tech so the adapter was linear. The dock is internally regulated to 5v but I have reason to believe that even the specified 11v is pushing things, temperature-wise, and that anything down to 9v would be appropriate.
The commonly-recommended Radio Shack replacement is no longer available, but it was apparently 9v. The Japanese version of this dock (“IFU30 Interface Unit”) uses the same internal hardware as the US device but specifies 9v, 1.45A with the same polarity and plug dimensions. They are interchangeable between regions, which tells me that a replacement within the 9v, 1.45A+ and 11v range should be acceptable. In fact, it sounds an awful lot like the exact same adapter with the 10-20% greater input voltage creating a proportionally higher output voltage (US 110-120v compared to JPN 100v).
I went to a thrift store and test-fit various loose plugs until I found one that fits: a modern Hyundai-branded 12v, 5A switching PSU brick that looks like it’s for an LCD monitor or something. I reversed the polarity and tested it and it works great, but these old CD docks are known for failing caps and we all know that electrolytic caps aren’t going to like the extra heat over the long-term.
IIRC, internal regulation is handled by two 7805s. Based on the Japanese spec, it seems that the US version is already running them hotter than their Japanese counterpart by feeding a higher voltage. I’d like to drop that voltage closer to the Japanese spec for increased reliability... anywhere in between 9v and 11v. I know I could just splice the end onto a 9v 1.45A+ plug, but I can actually use the extra amps here for some other projects and I want to be able to move the PSU between them.
I’ve never done anything like this but I assume it can be done with a couple diodes and a resistor, so here come the questions:
How do I know what specs to order?
Could I just salvage a couple of them from the rectifier of an old device that takes 12v AC?
Will this 5A diode from Mouser be ideal?
https://www.mouser.com/productdetail/vishay-semiconductors/egp51g-e3-c?qs=sGAEpiMZZMtbRapU8LlZDxCc6FzR8ItptId7%252bqIFh04e8bI1655czg%3D%3DHow do I determine the value of the resistor I should pair with it (assuming that’s what I’m supposed to do)?
Thanks in advance.