JD990 strange noises - Phaser & Distortion

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NelsonFdT
Posts: 1
Joined: 18:24, 18 April 2014

JD990 strange noises - Phaser & Distortion

Post by NelsonFdT »

I recently bought a JD-990 and when I'm in Patch mode, when I use the Distortion, Phaser or both at same time, there are a lot of noises on the outputs.
My firmware version is 1.05. I already proceded to MSB Adjustement, used new cables and power on the unit alone, but the problem remains. I measured the voltages in power supply and they are all OK. When I test (in test mode) both effects' chips I get OK in both. I opened the unit but I didn't see anything burned.
The unit only has this noises when phaser and/or distortion are activated. If don't activate the the effects block A in the front panel I don't have this noises.
When I opened the unit I verified that both IC27 and IC28 (effects chips) are much more hotter that others IC's but none of them have a heat sink, they are really hot.
Anyone has the same problem? Can it be fixed?

Thanks in advance,
Nelson
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nukemodular
Posts: 3
Joined: 09:58, 23 June 2015

Re: JD990 strange noises - Phaser & Distortion

Post by nukemodular »

i had a similar problem with my jd-800...not in the phaser/distortion, but in reverb/delay/chorus...it sounded like an Lfo is causing noise bursts all the time...it turns out the dram chips were broken...i swapped them and now it works flawless again.

so in your case, if its the dram (im just guessing), it would be "IC-29" on the mainboard to check.
but i would do the "effects test" described in the service manual first, to be sure.

cheers, nik
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