well, it might need some more time because, just this evening, i've finally found how to boost maximum bias current the deck could deliver... something i was hoping to find for quite some time.
These AX heads, in general, need more bias than original ones and my internal bias trimmers were just pushed to the max without being able to properly bias certain brands/models of metal tapes.
(i could still bias any type1 and type2 properly, though)
Well, after experimenting some more modifies, which I guessed they were THE way to raise maximum bias current, it seems they are not... but, on the contrary, even if i gained quite some available range at the bias trimpots (they give me the previous max bias levels when they are tuned half way, at now) , it seems I am putting the circuit sort of out of its own specs or something like that.
So, unless someone truly expert will give me a hint about how to do that in this deck, it seems I cannot nicely exploit the metal tapes with the highest bias point I own here (i.e. TDK MA and That's MR-X PRO) and I'd need to stick only to the Sony Metals which work well with some less bias current.
And, of course, I can nicely bias all type1 and type2 tapes which need less bias current than any metals.
On the other deck I had modified with amorphous heads, my Technics RS-M260, I was able to raise the maximum bias but, differently than the RS-M260, this AIWA has also HX-PRO handling the bias levels then it's a more complex circuit and, of course, there is something I am failing to get about it... we'll see... I know that if I go and ask Alex/A.N.T. about how to get more bias on the AD-F880, he will likely be able to tell me the solution in a matter of 5 minutes but I don't want to "disturb" him with such questions... also, if I'll ever happen to find the solution by myself, it would be nice but, keeping experimenting without finding the actual solution risks to be frustrating.
So, for now, I will revert the deck to how it was before this latest attempt to raise the bias current and will record the metal tapes with highest bias point on some of my other decks here, which can do that.
Why not make a nice new machined and engraved aluminum face plate? Then add whatever features you want and arrange switches as desired. Replace crap switches with good ones etc.
Nice, but it would be a hard work and I don't know anybody here who might make a suitable face plate.
Also, it's not possible to alter the actual layout of the front panel controls, since there is a PCB behind the face plate, and a long row of pins on the main board which insert there in the PCB behind the face plate in a very precise way.
About the selector switches, there are only the timer and memory ones which I repurposed as bias ranges and they are of good quality... of course, i opened and cleaned them inside.
The source/tape and "Rec 120us EQ mode" (previously MPX) button switches, they are not really at the front panel but those are buttons with long plastic pieces behind which go to the main board, where the actual switches are located, so they cannot be replaced.
The remaining switches are all button microswitches which are soldered on the front panel's PCB, then they must also stay as they are.
Last, there is the power on/off switch and the Eject button is totally mechanical and it must stay just as is.
Let's say that some properly printed adhesive labels with a truly black background would look a lot better than what I did here... and this is just something I'll do when the deck will be totally ready.