[Roland] [TB-303] – [CPU or LED Noise? Failing banks?]
Hi there. First-time poster, long-time fan of Syntar.
I have a Roland TB-303 here which I have had since 1996. I rarely use it for a number of reason but I want to put it back to work in the studio in the very near future. It has the aftermarket TT upper board Blue LED mod, which was installed professionally about 20 years ago. However, it has always been rather noisy with a high-frequency buzz regardless of the batteries being used only or PSU being used and is present no matter what the volume pot is set to. Further to that, its recently exhibited a behavior where certain pattern banks refuse to allow me to program them. I’m not sure if the SRAM is dying or the CPU is failing or what, so I’m looking for some guidance here before I find a reputable repair kat here on the western side of the US that I can send it into to get serviced.
Based on what I have wrote above, perhaps someone can let me know what the issues are?
Cheers!
Kel
aka DJ Lithium
Black Tiger Recordings - Las Vegas.
Not as of yet on the voltage checks. I have to dig my multi-meter out from storage. On the caps side, this unit is as pristine as you can possibly get and there is no visible corrosion anywhere and no leaks or swollen caps at all.
I’m not that swift when it comes to deeper electronics issues but I do have the schematics and will be going through a few things once i dig my multi-meter out. I may pull the Technology Transplant upper board off and put the original which i still have back in and see if that solves the issue. One thing I have noticed over the past couple of years is the upper board LEDs started going wonky with one of them rarely lighting. I’ve been doing some reading regarding what might cause that and it could be a resistor or diode on the upper board and its causing something somewhere else to fail. What I don’t understand it how the other pattern and track banks other than 1, are now all wonky and won’t let me edit and the unit will run in pitch mode now for some reason but the pattern is hyper blippy and in track mode it has a mind of its own with no control over it whatsoever. Any hints would be greatly appreciated.
Ok so a bit further into it this afternoon after I dug up my multi-meter and did a CLOSE examine of the upper board.
Rail power is coming in at 9.45 Volt off the rail so I would say that’s about reasonable.
Now here is the fun part…
I went and did Robin Whittle’s mod for the ground hum, soldering in a wire between the line out jack ground pin and the volume pot ground pin. No difference in the noise whatsoever. If I turn the volume down, its there, constantly. It only diminshes when notes are playing.
on close examination of the upper board, I found that suspect LED, while still finicky in terms of illumination, actually had a cold solder joint so I reflowed it and now the problem I was having with the other memory banks going nuts, has NOT entirely gone away but its better. I think I may have to replace this upper board, but its weird because the problem only exhibits itself when the track pot is turned to anything but selection 1.
I do have a replacement for that here, but I may order a new one from either Syntar (I think they have one) or else where and see if that does the trick.
I also resoldered the battery leads to the terminals just to be sure (taking off from orbit you know…).
I’m not happy about the noise problem but with the Line6 PodXT I have it running through with the gate, it cleans it up more or less, but I would like to get to the bottom of what is causing that. I’ve been looking at the other CPUs on the market now including the new one from Michigan Synth works that came out this spring but sure enough… out of stock.
If anyone has any suggestions on whatever else I can try before going down a further rabbit hole, please let me know.
Voltages seem to check out. I’m pretty sure its the SRAM as the other positions on the track/pattern knob produce the weird behavior. I may shoot a video of it later today.
I ordered a new CPU from MSW, so hopefully that will address the issue. If not I’m going to be picking up a new upper board from Syntar and keep going down the list of things that might be screwing it up.
Maybe try running something into the mix input too to make sure it’s functioning and how it affects the noise. The mix input comes after the volume pot so if something is wrong there it can cause issues unaffected by the volume pot.
Out of the headphone jack has always been much much cleaner. I would say 80% if not a little more in reduction of noise. What are you thinking that this might be connected to as far as the line being the much noisier of the two?
Re: the noise. The electrolytic capacitors are time expired. After 30 years they time expire because the corrosive electrolytic fluid eats the interior metal of the cap.
Ok so quick update. I bought and installed the MSW 303 CPU replacement and it NO LONGER MAKES THAT BAD SOUND. However, in the course of 20 years of use since I installed the TT keybed replacement, its decided to flake out and I have ordered a replacement from Syntar which shipped within hours of me placing the order! Thanks guys I hope to have it back up and running this saturday if delivery schedules hold.
Will report back.
I hope to have it back up and running this saturday if delivery schedules hold.