Roland JX8P no sound

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radek tymecki
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Roland JX8P no sound

Post by radek tymecki » Sat Nov 05, 2016 1:23 pm

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?

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Re: Roland JX8P no sound

Post by Rasputin » Sat Nov 05, 2016 1:36 pm

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.
Last edited by Rasputin on Sat Nov 05, 2016 2:08 pm, edited 1 time in total.

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Re: Roland JX8P no sound

Post by radek tymecki » Sat Nov 05, 2016 1:58 pm

thanks :) i'll check tp5

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Re: Roland JX8P no sound

Post by radek tymecki » Sun Nov 06, 2016 8:34 pm

checked. no sound. just buzz

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Re: Roland JX8P no sound

Post by Rasputin » Sun Nov 06, 2016 10:47 pm

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

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Re: Roland JX8P no sound

Post by radek tymecki » Mon Nov 07, 2016 2:27 pm

will have a closer look into this. thank You :)

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Re: Roland JX8P no sound

Post by radek tymecki » Tue Nov 08, 2016 3:36 pm

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

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Re: Roland JX8P no sound

Post by radek tymecki » Mon Dec 05, 2016 3:55 pm

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

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Re: Roland JX8P no sound

Post by synthRodriguez » Sat Dec 17, 2016 3:01 pm

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.
Last edited by synthRodriguez on Mon Dec 19, 2016 11:15 pm, edited 1 time in total.

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Re: Roland JX8P no sound

Post by radek tymecki » Mon Dec 19, 2016 8:47 pm

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?

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Re: Roland JX8P no sound

Post by synthRodriguez » Mon Dec 19, 2016 11:21 pm

Check the rest of the 4051's if you haven't already, IC 44, 49, 48, 46, 47.

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Re: Roland JX8P no sound

Post by radek tymecki » Tue Dec 20, 2016 4:42 pm

all checked, also exchanged to new ones. still same issue

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Re: Roland JX8P no sound

Post by radek tymecki » Tue Jan 31, 2017 7:56 pm

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?

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Re: Roland JX8P no sound

Post by jxalex » Fri Feb 03, 2017 1:09 pm

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?

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Re: Roland JX8P no sound

Post by radek tymecki » Fri Feb 03, 2017 2:33 pm

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

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