hifi engine

Akai X-150D - real schematics and FF/Rew cam

Does anyone have the actual electronic schematic for the boards in the Akai X-150D? I have the service manual, but there are no schematics in it, just some bad photos of the boards One channel seems to have much less gain than the other and it would be nice to have a set of schematics so I could troubleshoot.

Anyone know if there is any amplification done by the play/record switching board?

The electronics look pretty simple, but troubleshooting without a schematic will be a pain.

Also, does anyone know of a source of the diecast "cam" under the Rewind/Fast Forward knob. The one in the Akai 150D I just bought seems to have disintegrated. Really weird. It just seems to have crumbled apart. Other similar cams in the deck look perfect, but this one looks like it was hit with battery acid, roasted in a fire and exploded! Failing a replacement does anyone have an accurate drawing or good photograph of it so I'd have a chance of machining up one myself. So much has broken off this one it's hard to tell what's supposed to be there!

Akai X-150D - real schematics and FF/Rew cam

I would check the electrolytic capacitors first. If the Akai uses the C458 transistors they may be the source of the gain problem.

Failing pot metal is a real problem. About the only chance you would have is to find a junk 150 with a fairly intact cam, or possibly experiment with sheet plastic and make a prototype that a machine shop could reproduce in metal. Plexiglass might work.

Akai X-150D - real schematics and FF/Rew cam

Thanks. What I did with the cam was to build it back up with epoxy putty to what i guessed might be a suitable shape to move the various associated levers, then shave bits off until it fit back where it should and operated the levers OK. It's not going to last well and though I have FWD and REW working properly I don't quite have the braking right so it needs more shaping.

I was going to make one out of plexiglass, but thought I'd try the epoxy first. Plexiglas is a bit of a pig to machine since if you get the cutting speed wrong it just melts! If I knew what the right shape was supposed to me I might try aluminum or brass, but without an intact original that's tricky - and if I had an intact original I wouldn't need to make one!

After some basic troubleshooting (switching the preamp boards) I'm starting to think the gain difference might be on the rec/play switching board. That would be the one with the 2SC458 transistors on it according to the schematic. Looking it up I see they do have a reputation for failure. I was also amazed to see that you can still buy them - and for 8 cents each (http://www.futurlec.com/Transistors/2SC458pr.shtml). I wonder if there is a better replacement, though I assume that manufacturing now is better than it was when they were first made, so maybe they are more reliable now. I do see the 2SC2240 recommended so maybe I'll give that one a try.

Pity there are no real circuit schematics for the X-150D boards, but the circuitry is simple enough that it's not too hard to guess at things and all the components are recognizable (and large!).

reel to reel nut's picture

Akai X-150D - real schematics and FF/Rew cam

The cams on the 4000 and 17xx range are all the same so any scrap akai off ebay will do for a good supply of spares .

Akai X-150D - real schematics and FF/Rew cam

That's very useful info. I'll keep an eye open.

Sounds like an ideal 3D printer job if someone had one to measure and produce a blueprint from!