Welcome to the first (of maybe many) repair advice post!
Just to touch on what these posts will be all about… put simply, there are plenty of repair processes I keep close to the vest and thats unlikely to change until I retire.
However, there are plenty of issues I come across that I may feel I never want to fix again and therefor feel the information should be easily available so people can repair (or blow up) their own stuff and avoid bringing it here where they’re likely to wait 100 years for us to do anything.
Having said that, I take no responsibility for you blowing up or otherwise damaging your gear. I also don’t guarantee this will work exactly for *your* unit and genuinely don’t want to answer any questions. What you see if what you get here.
If you are knowledgeable and feel that I have made an error in judgement and would like to correct anything written here, I welcome that and will credit you for your advice and of course update this post.
Anyway, on to the subject. In 2017 I purchased a TX-816 from a guy and it was one of the weirdest gear purchase scenarios of my career but that is another story for another time (never).
It worked just long enough for me to buy it for a decent price and as soon as they guy walked out with the check it shut off on its own. Since then, it has worked for less and less time per use session.
I figured it must be the power supply, as it stays on for a while if I take out most of the TF-1 modules (mine has all 8 modules). So I took it apart and decided a classic recap should to the trick. I changed whatever I had stock of but didn’t change all the caps. It did work a bit longer than usual, but died again. It also started to whine, even when “dead”.
So it sat on a shelf with the idea that one day I’d recap it the next time I’m working on one for a customer.
That day never came and finally my right hand mans TX816’s PSU bit the dust so now the pressure is on. We can’t both have dead TX-816’s…
A few months prior, I fit a studio electronics rack mounted Prophet-5 with a new switching PSU. It was appropriate since they added their own power detect/reset circuitry alongside an off-the-shelf switcher that had failed. It worked strikingly perfect.
I thought this same PSU could work well for the TX-816 since it provides the 3 standard voltages, +15, -15, and +5. The supply is rated quite robustly all things considered. Really goes to show where we are technologically at this time.
It’s important to understand why I added the above about the rack mount Prophet… you really can’t just go willy nilly replacing supplies. Many supplies do have some functions the connected circuits rely on. Things like resets, power detects, unregulated voltages for some oscillator and other circuits, etc. The reason this works well is because Yamaha, too, stuck what is essentially an off-the-shelf switcher into these units. Therefor, another off-the-shelf switcher should do.
So, I finally ripped apart my TX-816 (oh my god, so many screws….) again and removed the cruddy supply and started preparing for my science experiment. I didn’t take many photos because this isn’t for a client or something I plan to do often, so the one photo below and my directions and description will have to suffice.
The TX has a board mounted upside down for the incoming AC… this board can remain as it does make connecting the new supply very easy.
– Open unit and remove PSU.
– Disconnect PSU molex header from the power rail distribution board
– Cut the wires from that molex connector on the PSU side as they will be connected to the new switcher. The molex will reconnect once we’re done wiring the switcher. Note that I chose to snip the wires as close to the PCB as possible. I believe snipping them from the outside of the case is good enough, but I’m unsure.
– The white/black wires coming from the upside down AC board are the post-switch and fuse AC wires. They make it much easier to install this supply as all you need to do is cut them off the old supply and hook up those wires to the new switchers L/N terminals
– Connect all orange wires to the +5V terminal
– Connect brown wire to +15v temrinal
– Connect yellow wire to -15v terminal
– Connect all gray wires to COM (gnd) terminal
– Connect black wire to earth ground terminal
– Reconnect molex to the power rail distribution bus board.
Before powering it up, you could disconnect the molex and test the v’s and make sure its all good. These mean well switchers have a lot of built in protection, so I risked it all and just powered up. I was not shocked to see it worked perfectly and survived a long burn in. We did not burn it in in a rack of other hot devices, so YMMV (and ours) of course.
As for mounting it, there are a few ways to go I’m sure. The threading on the side of the supply are M3, which are the same as some of the extra screws you will have from removing the old supply.
Since I’m lazy and unlikely to ever sell this unit, I mounted it through the vent slits on the bottom with the supply on its side. Im sure it can be done more elegantly. If you send me photos of your install I’ll be happy to post and credit them here!
Oh, and you’ll need a supply. The part number is RT-65C and can be had from Jameco here.