Roland Juno-2 Won’t Power On – Repair Adventures

Two Roland Alpha Juno-2 Synths
Two Roland Alpha Juno-2 Synths

Hi everyone,

Recently I acquired my 3rd Roland Juno 2 synth for free because it simply wouldn’t turn on. The owner said it worked before putting it into storage, and then about a year later he turned it on and nothing happened. He gave it to me because he already had too many door stops…laugh. I thought maybe I could fix it, but it’s proven to be quite stubborn. Above is a photo of my work area where I’m currently testing the broken Juno-2 (bottom one) with a fully operational one above (top).

The Roland Juno-2 basically has never been opened. I open a lot of synths and I can tell that I’m the first one to crack it open. The Juno-2 is in excellent condition all around. When you flip the power switch it’s completely dead. No flicker, no heat, no noise, nothing. It’s like the power doesn’t even get to first base or even into the machine. I do try to repair my own synths, however I usually leave the Power supply area alone as that is not my strong point. Inside the Juno-2 seems pretty basic, so I thought I would scout around and see if I could find the problem in the hopes that it might be a simple fix.

I opened up the synth and inside everything seemed clean and connected. The power cable was fine, the switch looked good, along with everything else…BUT… the Electrolytic Capacitors looked funny to me on the Power Supply Board. Usually if they are bad I notice a bulging at the top, however the three capacitors on the power supply board look fine on top. The bottom however look like they could either be leaking or perhaps surrounded by a glue of sorts. I’m not sure which, although my guess it’s a leak. It’s kind of dull and crusty while glue is usually shiny and smooth.

My thoughts are that if the Electrolytic Capacitors are bad, that might be the reason the Juno-2 is not turning on, OR getting power to the rest of the synth from the Power Supply board. Otherwise, I have no idea why the Juno 2 will not power on.

Any ideas would be greatly appreciated.

Here are some photos.

Roland Juno-2 Electrolytic Capacitors
Roland Juno-2 Electrolytic Capacitors
Roland Juno-2 Electrolytic Capacitors
Roland Juno-2 Electrolytic Capacitors
Roland Juno-2 Electrolytic Capacitors
Roland Juno-2 Electrolytic Capacitors

UPDATE #1:

I wrote a comment below about the switch looking bad. Here is a photo. The wires are loosely soldered to the two plugs attached to the switch. The two plugs wiggle. On my other working Juno-2, the switch, plugs, and wires are rock solid with zero play.

Roland Alpha Juno-2 On/Off Switch
Roland Alpha Juno-2 On/Off Switch

UPDATE #2:

After using a Multimeter and checking for continuity all over the Juno-2, I’m finding zero problems. It really has me stumped. The only area I can seemed to properly check is the Power Transformer shown in the photo below. This sits in between the Power Supply board on the left and the Fuse board to the right. Both the Fuse and Power Supply Boards are 100%. Still when I turn on the Juno-2 below I get zero power past this Power Transformer. Could that be the cause? Not sure.

Juno-2 Transformer
Juno-2 Transformer

********** UPDATE #3 ***********

I’m getting close!!

I have discovered through swapping everything around with a working Roland Juno-2 that there is a definite problem on the MAIN BOARD. The battery has been changed and reset procedures have been done, but there is still no sign of life. There must be a broken connection somewhere and so I’m now consulting the Service Manual. Stay tuned!!

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