I've had similar issue (as I discovered later) with CPU NEC D70008AC-6 (Z80) in my Yamaha PSR-60 keyboard. After switching the power on, not a single button or key worked at all as well as all the LEDs (except the Power). Sometimes when I switched the power on while holding random button, some LEDs did work but it didn't change anything. So I replaced all the 66 (!) caps and 2 ROM ICs. Nothing changed. Analog and digital voltages were good. Then it came to my mind that maybe the reason was in logic. So I decided to replace the CPU (I got used one from AliExpress as it wasn't available in my country). And it really worked!
Thanks so much for these videos. Clearing the system memory was a huge help to me, and after I replaced the battery I watched your video again to remember how to do it. Thank you!
This is the kind of video repairs where a lot of things go wrong are the most interesting to watch in addition to some informational ones. Focusing on the single skill in depth would be also helpful I hope you will continue to bring good content frequently.
I'm not sure about *that* piece of tape, but mine did come, new, with a piece of tape (transparent amber mylar) in that spot. It's been a long time since I replaced the soldered-in battery with a battery holder, so I don't know if it was due to longer battery terminals, nothing else seems obvious. One note to watch out for: The factory 3300µF caps have very thick leads, a fair tight fit through the vias. And in retrospect, I can see one of the caps had the leads squashed a bit in trimming them, from the original installation, explaining why it took some work to get C143 out in particular. Even though I was careful to use reasonable and steady force, it pulled the vias out. The traces were fine, just the vias, and they were so tight on the fat leads I was lucky to notice it even happened. I thought, surely that not the only connection from between the two sides of the board for +5V and DGND, but it sure was. So after replacing C143 (I replaced all electrolytics) left, I had to drill a couple of holes and connect top and bottom for each of the paths. In my case, the unit's failure mode was the display going wild, the +5 supply showing a ton of noise...and a bloated C149, so the cause was obvious.
Hello there. Please, help me. My Yamaha SPX 900 died. I noticed there are two burnt out 11ES4 diodes in the power supply plus leaky capacitors. Can you please tell me which equivalent diode I can buy? I don't find 11ES4 diode anywhere. Thank you very much and congratulations for the wonderful channel.
Hello Brad - your video inspired me to take a stab at fixing up a PCM70 I got in pretty rough non-working condition. I found and addressed a few things wrong with the unit, and was able to get the display working, but there is still no reverb and the sound is fizzy and distorted even in self-test mode, and worse in normal/run mode. The overload indication (front panel level LEDs all on) goes active a few seconds after power up with a light sort of fizzy pop sound . I can get a clean signal through the unit only in 'bypass' mode. I am wondering how I can confirm the checksums on the three main EPROM chips. I have access to an eprom reader at work, but I do not know what the checksums are supposed to be. Could you possibly pass along or point to a source for that information?
Hi Brad. Awesome video. I am struggling with a similar issue. PCM70 with only half the chars showing on the display and no response from the keypad. I am quite sure this comes from the 74HCT273 and / or 138. It threw me a little seeing that the Z80 was also bad in your case. Any thoughts?
Hi Brad, I got a PCM70 which the z80 CPU was done, I am wondering that if I could find another same z80 CPU to replace it. Or should use the z80 CPU in the PCM 70?
Hi brad, nice vidz! I also have a pcm70 with battery low on it. I saw that the battery is a vertical mounted BR2325-1VC (3v/165mA) lithium coin cell from Panasonic. Do you know if I can put any vertical battery holder or is it a special one that is needed? I think it's better to not to solder desolder each time I change the battery. I saw you'll do a pcm60 video too? That's cool I have one and I think it's noisy, surely need some recap.
You can definitely replace it with a socket. mine wasn't dead so I didn't bother at the time. Digikey or Mouser should have one the right size, just need to measure the pin spacing. I'm wrapping up another synth repair now and have a pair of PCM60s that need repair that I'll be working on next, so that will be coming soon.
hi brad! just came across your video looking for some resolutions for my PCM 70. It's saying 'battery low' on the display, is this a problem I can fix myself? or would you recommend asking someone who knows better...
Yep, just replace the internal battery, it is soldered in but easy to replace. After that, factory reset it. You will lose any saved presets in this process.
anyone know WHAT is with those GOLD knobs??? i have an M300 that has the same - was this some weird quirk when lexicon had a particularly bad production manager or what?
So many are like that, lol. Best guess is something with the paint / powder-coating at the time fades or is worn from use and turns a slights gold color. Very odd.
