¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. YamahaDX
  2. Messages
Single Messages Topics Expanded Polls

Re: TX802 troubleshooting

 

Two things to avoid: dismissing input from Daniel Forro and making assumptions. This is first and foremost electronic troubleshooting.

Check all the Power Supply voltages. I have seen an increasing number of Yamaha PSU failures which are happening because a LOT of the Yamaha designs use a Switch Mode PS. I have been able to repair some of the PSUs, but not all. There are many threads online discussing this or that synth or effects unit needing PSU repairs and various successes and failures.

Look at the waveforms being discussed here with a scope. Don't have these tools? Why not? a decent DMM can be had for less than $100. A brand new excellent scope for under $400. At some point one realizes they don't have the knowledge, skills or tools. This is fine for learning, but don't expect infinite patience from online help.

I am not pro-cap replacement, but as far as the PSU is concerned this is a common problem with them. Definitely check the OS checksum, even better would be a CRC or a direct BIN file comparison.? The BIN files are everywhere.

Reseating the EPROM was a good move. Sockets get dirty. Bad connections cause a myriad of problems. Look at the schematics and Service Manual. Most of the Yamaha FM products have a huge similarity and some of the Service Manuals are very helpful, others less so.

On 2/4/2023 1:24 AM, contact@... wrote:
Op za 4 feb. 2023 om 03:44 schreef Daniel Forro <danforcz@...>:
Have your tried to replace OS Eproms?
I have re-seated them, if that is what you mean. I have an EPROM
reader so I could read their contents and compare the checksums with
those listed on .
I don't find it a promising direction though. If an EPROM was
corrupted there would be crashes, or more other things that go wrong.


Have you done diagnostics test?
Yes.


There were some reports about noise at the outputs in some series of TX802 - solved by replacing opamps.
As I mentioned in my first post, if I take an init patch and change
the algorithm to 32 then I get a perfectly clean sound. That rules out
any problems in the output stages.

Problems with sound quality can be also caused by muting transistors. Somebody deactivated them or pull out, somebody replaced them.
If the muting transistors were bad they would be bad all the time.
They don't know what FM algorithm I'm using.


Check the signal from the output to DAC, to find if the problem is in analog circuit or digital circuit.
As I wrote above, I already know the DAC is fine. It would not be able
to produce clean sine waves with algorithm 32 if it was broken.


Check all crystals, too.
If the crystals were misbehaving many other things would be wrong.
MIDI reception would be messed up. There would be weird sound
artifacts on the outputs. The outputs can produce clean sine waves
with algorithm 32 and the crystals don't know about the algorithm.
Join [email protected] to automatically receive all group messages.