Vintage Synth Explorer Forums

Hey VSE,


I've recently acquired a used JP8K from guitar center, with minor cosmetic wear and the "low battery" message appearing when starting up.

The problem that I've noticed is under the bank "KEY & PANEL", the three indicator lights for the key mode settings seem to constantly be on, and not responding to the corresponding button. One thing I've noticed is that when powering up, all the other LED's on the board remain dim while the Roland logo flashes on the display, save for those 3 lights.

I HAVE reset to factory settings, and to no effect.

What do you think the best course of action is?

Have you changed the battery?

No, I've not had the chance to replace the battery. I've had this synth for all of two days.

Then I suggest you do that, just to make sure it doesn't impair the factory reset. At least you'll be able to rule it out!

Alright, status update.

I've replaced the internal battery, which was really a doozy to replace. I no longer get the "BATTERY LOW" message upon start-up and the memory functions seem to be working well. However, the problem LED's have not changed at all.

Do you have any idea what might be causing this? Any advice would be appreciated, I can still return the unit for another 20 days or so.

I'm guessing that the buttons for the key modes are broken or short-circuited.

I suppose I should mention that the Key Mode button functionally seems to work fine, however the LED's do not change when the button is pressed.

If there is a short in the wiring, is that something that is fixable?

My remote diagnostic skills are fading with age, so take this for what it's worth:

May I assume you mean the "SINGLE, DUAL, SPLIT" button lights?

Looking at the schematic, those three LEDS are controlled by
Q12 - 2SC1815GR transistor (column driver)
and
!C15 - 74HC273AP (latch)

First thing I'd do is scope pin 18 of IC5 (on the panel board with the wonky lights)
should see pulses
Then pin 19 of IC5 - should see longer slower pulses. If this pin is DC, the IC is bad.

If ok, then test pin 2 of Q12
(you should see the same kind of pulses as on pin 19 above.
If DC, then the xsistor has shorted

as always use a magnifying glass to check for solder bridges, etc.

If you can still return for a full refund, maybe a good idea.

Depends on the price you paid for it. $250 or less, I'd keep it! After all, if the function is there, and it's only a light problem... Get it fixed by a tech later.

rhino wrote:My remote diagnostic skills are fading with age, so take this for what it's worth:

May I assume you mean the "SINGLE, DUAL, SPLIT" button lights?

Looking at the schematic, those three LEDS are controlled by
Q12 - 2SC1815GR transistor (column driver)
and
!C15 - 74HC273AP (latch)

First thing I'd do is scope pin 18 of IC5 (on the panel board with the wonky lights)
should see pulses
Then pin 19 of IC5 - should see longer slower pulses. If this pin is DC, the IC is bad.

If ok, then test pin 2 of Q12
(you should see the same kind of pulses as on pin 19 above.
If DC, then the xsistor has shorted

as always use a magnifying glass to check for solder bridges, etc.

If you can still return for a full refund, maybe a good idea.

Yes, the SINGLE, DUAL, and SPLIT lights are the problem. I greatly appreciate your response, as you have in a single post given me more detail than several emails with Roland US. You seem to really know what you are talking about here, but I'm afraid a lot of this is greek to me.

fh991586 wrote:Depends on the price you paid for it. $250 or less, I'd keep it! After all, if the function is there, and it's only a light problem... Get it fixed by a tech later.

I've paid $500 for it, plus an additional ~$50 for tax/shipping.

I'm thinking it might be in my best interest to look into returning the board, however GC doesn't seem to want to respond to my emails anymore. Roland directed me to take it into a local repair center to have them take a look at it, but I'm kind of hesitant to sink any more money into this synth.

Tell us (if you will) where you are located. Maybe a member near you can recommend a good tech.
My dealings with Roland point to them wanting to swap in a new mainboard for any little problem rather than spending any time diagnosing.

I am in the Metro-Detroit area, Oakland county to be specific.

According to Roland's website, there's a licensed repair place (whom I have yet to contact) a stone's throw from me. However if you guys think that there is a better, perhaps more cost-effective alternative anywhere in the Detroit area I'm all ears!

I'd love to hang on to this JP8K, as I've already grown quite fond of it's snappy-sounding envelopes and intuitive layout. But right now it's just a question of whether or not I can have this repaired in a safe and reasonably-affordable manner.

And worst-case scenario, I send it back to GC and get most of my money back. I greatly appreciate all the advice/help you guys have given me so far!

Here's one:

In the Detroit, MI area the best place to take a synth is Electronic Innovations St. Clair Shores, MI 586-443-4121 They do exceptional work on both vintage and newer synthesizers. They also repair tape recorders, mixers, ect. ...

This weekend I'm going to call around and try and figure out a course of action here. I'll make extra sure to look up the place in St. Clair Shores.