Page 1 of 2

Roland JX8P no sound

Posted: Sat Nov 05, 2016 1:23 pm
by radek tymecki
Hey there. I have no sound at the output only buzz. Checked the voltages and they're +/-15, +5 and 8.5V at 7V. What can be the problem?

Re: Roland JX8P no sound

Posted: Sat Nov 05, 2016 1:36 pm
by Rasputin
I'm assuming that means both headphones and 1/4" main outs. Correct?

Try hitting test point #5 and see if you have any audio there. To find TP5 on the PCB, look at the MIDI THRU jack, then go straight down until you hit IC64. You'll see TP5 just a tiny bit to the right.

P.S. I like the patches you did for the Roland D50.

Re: Roland JX8P no sound

Posted: Sat Nov 05, 2016 1:58 pm
by radek tymecki
thanks :) i'll check tp5

Re: Roland JX8P no sound

Posted: Sun Nov 06, 2016 8:34 pm
by radek tymecki
checked. no sound. just buzz

Re: Roland JX8P no sound

Posted: Sun Nov 06, 2016 10:47 pm
by Rasputin
Check IC43 which is an 8-channel HD14051 multiplexer which sends the VCA signal to IR3R05 (custom Roland VCA/VCF chip), probably pin 13 in particular.

Here's the datasheet:

Here's some info on the IR3R05 VCA/VCF chip (IC59). It's hard to find a pinout, etc. about this particular chip so:

PIN 1 - SIGNAL INPUT
PIN 2 - FREQUENCY
PIN 3 - RESONANCE
PIN 4 - LINEAR INPUT
PIN 5 - EXPONENTIAL INPUT
PIN 6 - LOAD
PIN 7 - -VEE (EMITTER SUPPLY)
PIN 8 - OUTPUT
PIN 9 - GROUND
PIN 10 - C4
PIN 11 - C3
PIN 12 - C2
PIN 13 - C1
PIN 14 - +VCC (COLLECTOR SUPPLY VOLTAGE)

Block Diagram & Info #1:
Block Diagram & Info #2:

Pin 4 should be the one that connects to IC43.

Real-life case files; maybe your problem is similar to one of these:
http://www.vintagesynth.com/forum/viewt ... =5&t=85019
http://synthpeter.blogspot.com/2012/01/ ... rking.html

Re: Roland JX8P no sound

Posted: Mon Nov 07, 2016 2:27 pm
by radek tymecki
will have a closer look into this. thank You :)

Re: Roland JX8P no sound

Posted: Tue Nov 08, 2016 3:36 pm
by radek tymecki
ok i've exchanged ic43 and almost nothing has changed. the buzz/hum is more/less intensive on different presets. still no sound on output

Re: Roland JX8P no sound

Posted: Mon Dec 05, 2016 3:55 pm
by radek tymecki
more updates - checked IC45 and this seems to work ok. IC53-54 are also ok. we've exchanged them but operation was similar so we went back to stock ones... still have no idea what can be wrong

Re: Roland JX8P no sound

Posted: Sat Dec 17, 2016 3:01 pm
by synthRodriguez
Check audio out at TP5. If it sounds fine there, it's something in the effects section, filter, limiter or output op amps.

If it sounds the same, it's in the synth engine proper.

EDIT: Oops, sorry, I see you already did that.

Re: Roland JX8P no sound

Posted: Mon Dec 19, 2016 8:47 pm
by radek tymecki
sadly the sound at TP5 is same as on the output :( I've exchanged IC50 (4052), 58/64 (4558) but this changed nothing. Went step further and changed IC70 (M5218) but still nothing. IC51/52 are fine. What can be checked now?

Re: Roland JX8P no sound

Posted: Mon Dec 19, 2016 11:21 pm
by synthRodriguez
Check the rest of the 4051's if you haven't already, IC 44, 49, 48, 46, 47.

Re: Roland JX8P no sound

Posted: Tue Dec 20, 2016 4:42 pm
by radek tymecki
all checked, also exchanged to new ones. still same issue

Re: Roland JX8P no sound

Posted: Tue Jan 31, 2017 7:56 pm
by radek tymecki
still no success with this one. cpu is not sending midi signals, quartz are ok (16 and 12mhz). i'm running out of ideas... anyone?

Re: Roland JX8P no sound

Posted: Fri Feb 03, 2017 1:09 pm
by jxalex
radek tymecki wrote:still no success with this one. cpu is not sending midi signals, quartz are ok (16 and 12mhz). i'm running out of ideas... anyone?
NOT sending MIDI signals? Are there any events occuring when sending MIDI in? Any activity between the CPU and EPROM data lines?

EPROM firmware OK?

Does the system does a proper start (so countdown from 12 to 0 and then getting preset with name on display?).
If not, does the CPU gets a RESET signal?

Re: Roland JX8P no sound

Posted: Fri Feb 03, 2017 2:33 pm
by radek tymecki
synth does proper countdown. i can access all parameters, edit them, but there is constant buzz on output. if i'm switching to sound with high resonance or sync i can hear the diffrences in that buzz/hum (eg sync with locked phase). when i've connected module to jx8p i was not able to control it via midi. i have no oscillosope so i cannot check the activity