DX7 test sequence - understand errors and what to do about them

Question

Just acquired a Yamaha DX7 MkI and run the test sequence:

Press FUNCTION+#16+#32

I got ERRORs on TEST 3, 4 and 6.

I am seeking pointers on what they mean and what to do?

Starting the test sequence on DX7 MkI

Are you sure? Yes

TEST 1 - OK

TEST 2 - LED CHECK - OK

TEST 3 - ERROR!

TEST 4 - KBD - Pressed middle C and got ERROR!

TEST 5 - NOT COMPLETED?!

TEST 6 - ERROR!

TEST 7 - OK (?)

TEST 8 - OK

TEST 9 - OK

TEST 10 - OK

Answer 1

There are several PDFs available on the web that explain this. It's actually fairly complicated so it's not really reasonable to explain all of these here. I'll see if I can summarize, taking the info from this PDF.

• Test 1 - 440 Hz test tone, volume control and foot pedal test.
• Test 2 - All LED and LCD segments flash on and off at 1 second intervals for visual check.
• Test 3 - Front panel switch check. Tester should press all front panel buttons in a certain order. If a button is missed (or pressing it doesn't work), the number of the missed button appears on the LED and the LCD displays "ERROR SEE LED". See the PDF for the button order.
• Test 4 - Keyboard test. Tester should play each key on the keyboard in order from lowest to highest. If a key is missed or does not register, the LCD displays "KBD ERROR".
• Test 5 - Controllers test (called "analog controllers", A/D refers to converting the analog controller settings to digital values). Controllers can be tested in any order. Moving a controller causes the display to show the name of the controller and the value it is at. Controllers should be able to show values from 1 (or 2 in some cases) to 99.
• Test 6 - ROM cartridge test. This test requires a special diagnostic ROM cartridge that may or may not have ever actually been released by Yamaha (at least that's what seems to be the case).
• Test 7 - RAM cartridge write test. Requires a RAM cartridge with memory protect turned off.
• Test 8 - RAM cartridge read/write test. Requires a RAM cartridge with memory protect turned off.
• Test 9 - Internal RAM and cartridge test. Does not require a cartridge but can do interesting things with one. This is a complicated test that may erase (user defined?) internal voices.
• Test 10 - Internal ROM test. Runs automatically and results in either "SUM CHECK OK" or "SUM CHECK ERROR", the latter indicating a ROM problem.
• Test 11 - Automatically plays a chromatic scale over and over again to use as an audio source for tracing audio problems in the unit.

For test 3, I wanted to find a clearer list of the button order, and even though I found the service manual it doesn't seem to have a clear list of the button order. You might have to experiment a little to figure it out.