A fix for trailing distortion after every effects based patch on JD800

This post cames from the Facebook Group Roland JD-800 / JD-990.

Our colleague Igor Kopman posted about the problem, and here what appears to be the main trouble, so he posted this first solution:

"Hi guys. Many people have Trailing distortion after every effects based patch on JD800. This is the DAC problem. Very easy to fix. Just replace the R100 resistor to another with a lower resistance on output board, and the problem will gone."

Here's the board: 

The circuit:

470k. Color code Yellow Violet Yellow Gold:

This one: 

Pay attention to this:

Our colleague Julian Camp replied:

Igor Kopman the original resistor has to be measured out of circuit. Do you still have your original and what does it measure? The schematic and colour code says it should be 470k

So after more replies from many colleagues in the group and thanks to  Igor Kopman  for presenting this need, Julian Camp posted what appears to be a more simple solution: 

Julian Camp

Replace VR1 with a high quality multi turn pot and it will fix the issue. The original VR when turned all the way counterclockwise or clockwise reads around 440ohm. The VR wasn't going low enough in resistance. Resistors R100, R101 and R102 tested within spec.

Thanks to everyone for supporting this great music machine! I love this synth and all you!

Manuals available: 

If you need the JDs Service Manuals plus all the others JD' manuals just enter at this page:

Manuals: JD800 and JD990 (Updated)

.'. 

The original topic text messages for credits, many people helped for sure!

** Igor Kopman

Hi guys.  Many people have  Trailing distortion after every effects based patch on JD800. This is the DAC problem. Very easy to fix. Just replace the R100 resistor to another with a lower resistance on output board, and the problem will gone.

** Radek Tymecki

You think that changing the resistor is the key? Caps are ok?

** Jym Mccullough

Can you be more specific on "lower resistance?" How about an exact value that works?

** Kevin Nolan

Jym Mccullough It looks like a 46 Ohm Resistor - hard to tell but I think I'm seeing Yellow-Blue

** Igor Kopman

Jym Mccullough I will open my JD800 and check it.

** Igor Kopman

Jym Mccullough Ok the resistor is 137k

** Kevin Nolan

Igor Kopman Yup - 46 Omhs - 137k - I was almost right 🥴 (ye know - on the cosmic scale of things...)

** Julian Camp

Igor Kopman the original resistor has to be measured out of circuit. Do you still have your original and what does it measure? The schematic and colour code says it should be 470k

** Igor Kopman

Julian Camp I think it was 240k or 270k

** Julian Camp

Igor Kopman that's what it would measure in circuit. Did you measure it out of circuit?

** Julian Camp

You have to take the resistor out of circuit to measure it. Mine reads 480k. The schematic and colour code shows it should be 470k. So this resistor shouldn't be the issue unless my cheap meter is correct and it is 10k out of spec. Will replace with a … Ver mais

** Julian Camp

470k. Color code Yellow Violet Yellow Gold

** Gilberto Strapazon

Thanks Igor Kopman!

Please, you or someone else with the same trouble may check about the measure out of the circuit of the probably damaged part?

This topic will be replicated at the JD800center if we have more info.

Appears the kind of problem with a easy solution and this means Gold!

I'm saving all the topic (with all replies for credits) for a post at my site.

I'm sure many people will be after this information too.

Thanks for more replies so I will soon post at the JD800Center too.

** Jym Mccullough

Gilberto Strapazon Thanks for maintaining your website. I've looked there many times for info and tell others as well.

** Julian Camp

I will replace the three resistors going to the trimmer pot and report back. Will be replacing with original values. R100 - 470k, R101-1M, R102-200k.

** Eric Vaubel

My JD-800 and my PCM-80 both do this. Will investigate!

** Julian Camp

UPDATE!

Replace VR1 with a high quality multi turn pot and it will fix the issue. The original VR when turned all the way counterclockwise or clockwise reads around 440ohm. The VR wasn't going low enough in resistance. Resistors R100, R101 and R102 tes… Ver mais

** Gilberto Strapazon

Julian Camp great! Simple and very effective!

.'. 

Another Very Nice Red Glue Repair.

Wow!

What a nice fantastic work and for sure nice photos!

Click the link or the photo bellow for the complete procedure.

Thanks Pete Sherman!

Roland JD-800 "Red Glue" repair

.'.

Great news! JD-800 flex circuit replacement!

.'.

Nice patches from the Roland JD-800 by MeX

Great selection! 

Nice patches from the Roland JD-800 by MeX.

 

 .'.

Roland JD800 SL-JD80-04 Strings Ensemble Sound Card preset patches

Strings Card!

The white head fly.

Sensational demos of the most famous Card of all for the JD-800 and JD-990.

The unanimous opinion is that you have a new synth with this card.

Our colleague Kozo Tsuji from Osaka, Japan made a series of fantastic videos about all JD cards, highly recommended and great quality material.

Here, the two videos showing why the Card Strings is something everyone wants very much.

Card: Roland JD800 SL-JD80-04 Strings Ensemble Sound Card preset.

Part 1:

Part 2:

Thanks to Kozo Tsuji from Osaka, Japan.

.'.

Sound demo! Roland JD800 SL-JD80-07 Guitar Collection preset patches

Another great demo from Kozo Tsuji.

All this cards have a lot of patches really interesting. 

Card: Roland JD800 SL-JD80-07 Guitar Collection.

Part 1:

Part 2:

Thanks to Kozo Tsuji from Osaka, Japan.

.'.

Sound demo! Roland JD800 SL-JD80-06 Grand Piano preset patches

Is not every day we find good demos, and this one is a very nice one. 

Here, you find the famous JD-800 pianos and a lot more. Fantastic sounds!

Card: Roland JD800 SL-JD80-06 Grand Piano.

Part 1:

Part 2:

Thanks to Kozo Tsuji from Osaka, Japan.

.'.

The Roland JD-990 and JD-800 together!

Another really good demo by Espen Kraft!

Here he shows the JD-990 power plus using the JD-800 as his natural controller.

.'.