I'm not a super expert tech but can solder

[rev mex]

Ok I get the "bad" message when I power on the drumulator. I put in new battery plus new electrolytic capacitors. Still "bad". I checked voltage schematic sheet (page 14) and everything seems ok. There are two problems so not sure if they're related. 1. I get the bad message. 2. When I hit record and play the drumulator locks up that I have to power off and on the unit. I'm assuming a memory device? If you can point me in the direction of troubleshooting then I can maybe figure it out.

I'm so close.


-Rev

[dr.c]

You have to erase the ram, there is a reset fonction, I forgot what it is, look in Google, its oly pressing buttons.

[rev mex]

You have to erase the ram, there is a reset fonction, I forgot what it is, look in Google, its oly pressing buttons.

It is beyond that. I am clearing the memory all the time. I believe it is a faulty memory device but it's a matter of finding where. I was hoping someone could give me insight on where to look. When I hit record and play the drumulator locks up so something is being called that is possibly faulty...I just don't know where to look in the schematics.

- Rev

[dr.c]

I would have to look at the manual but I am not home.
I will be back home saturday.

[rev mex]

DR C: 3 volts is VERY LOW, but is it the battery voltage, only ? Are you sure its the voltage given by the power supply ?
Did you reset the machine ?

voltage given by the power supply is 14 volts if I remember correctly. I'll go home and check - i wrote it down. I may upload a picture of the schematic and show what I get.

Most definitely reset it but the problem remains. I'm going to make a small video about what it does.
I actually didn't understand what part of the schematic to test when I'm checking everything concerning the record pattern function. I'm hoping I don't need an oscilloscope.
I haven't check my mosfets so that'll be the next thing.

-Rev

[dr.c]

The voltage supply must be 5.1 volts for the logic circuits !

[rev mex]

Dr. C or anyone
I'm looking at the Power Supply section of the schematics. c22 reads 11.8volts when on and .5 volts when off.
Would that be right?

Also, I'm beginning to lean to the idea that my battery is good. The reason I get "bad" is possibly because there is a power spike when I turn it on so it deletes everything. Can you tell me what is it the final destination that the 3 volts are supposed to reach when the power is off? I can track it on page 14 but seem to love se it when I start bouncing around the pages.


-Rev

[dr.c]

There are two ram circuits, 24 pin, they are the two large chips near the Eprom.
When shut down, you should read the battery voltage between pins 12 and 24.

Again, did you make the reset ? I had to dig for you :

Select SEGMENT mode
Press and HOLD ERASE
While holding ERASE, press CASS and the display should show "POOF"
STILL HOLDING ERASE, press ENTER and listen to metronome beep.

[dr.c]

when the power is ON, tyhe voltage should be +5 between the pins 12 and 24

[rev mex]

There are two ram circuits, 24 pin, they are the two large chips near the Eprom.
When shut down, you should read the battery voltage between pins 12 and 24.

Again, did you make the reset ? I had to dig for you :

Select SEGMENT mode
Press and HOLD ERASE
While holding ERASE, press CASS and the display should show "POOF"
STILL HOLDING ERASE, press ENTER and listen to metronome beep.

I can't say I heard about "still holding erase...."
I'm going to try that tomorrow. Also thanks for telling me which RAM pins to check.

I believe it's memory labeled 13k and 15k.
The memory chip has 24pins but the socket it lays on has 28 pins. Did you start counting pin 1 according the socket or the RAM chip?
Lastly, when the POWER IS OFF what should the voltage be at 14 and 28? The batteries voltage should be reaching this point, yes?

i do know that the pin count runs counter clockwise so im not that new.  

Thank you!

-Rev

[rev mex]

UPDATE:
9/13/16

I did the reset and I still have the issue. When I turn on the Drumulator I get "bad" message.

Also, I checked pin 12 and 24 on both the RAM Chips (not counting the socket that is for 28 pins). Pins 12 and 24 both come back with 5.1 volts when turned on.
I am getting 3.01 volts with the unit off which means that the battery power is reaching the RAM.

I made a little youtube video explaining problem to see if this helps paint the scenario.
In the video I am saying "pin 28" but it really pin 24" i was checking with the multimeter.
https://youtu.be/slwSDw27c9w

-Rev

[dr.c]

What did you do with this damn battery ? This battery should be in place with the old one !
Instead to knowing what does not work, see what works !

a) - the + 5 is working.
b) - the computer is working, otherways, thete would be no display, no possibility to access to anything
c) -  I/O is working, otherways, the switches wouldn't work.

Do you hear a "beep" when you reset the machine ? You did it in the video, and I didn't hear it !

Could you better what you are doing, I mean, the WHOLE front panel of the machine ?

[rev mex]

What did you do with this damn battery ? This battery should be in place with the old one !
Instead to knowing what does not work, see what works !

a) - the + 5 is working.
b) - the computer is working, otherways, thete would be no display, no possibility to access to anything
c) -  I/O is working, otherways, the switches wouldn't work.

Do you hear a "beep" when you reset the machine ? You did it in the video, and I didn't hear it !

Could you better what you are doing, I mean, the WHOLE front panel of the machine ?

yes it beeped when i reset. im wearing headphones and cannot record the sounds. I am getting drum sounds, the potentiometer responds, buttons all seem to work. I keep getting the "poof" at bootup and it locks up when I hit "rec+play." I'll setup camera better. I just got kinda excited and ahead of myself. I'm going to look for something that can produce sound from the machine so it can record.

As for the battery, that's actually not a bad idea what I did. I didn't invent this. But to preserve the board from battery corrosion etc one could set it up to be away from the board.

but "yes" it is true on all points you made. It locks up when I trigger "play and rec" so it's a matter of checking when this "command" is executed.
I'll rerecord this with sound next time.

-Rev

[dr.c]

Don't bother about sound recording, its was just to check what was working on your machine, wich allows to find what doesn't.

Take off the rams,verify if they are from the same type, and intervert them. Take off the Eprom and put it back in place.

Restart the machine and see if there is a different behaviour, not if it works or not, just if it has a different behaviour.
Where have you connected the battery ? I want to see this ! Take a pic and send it to : dr.c@noos.fr

[rev mex]

I just sent you the email with two pictures.

I swapped the RAM and the same problem. Nothing changed. I reseated the EPROM and acts the same.
Interestingly I took out the RAM and booted it. It acted the exact same. I was surprised it played any sounds with no ram in it. I hit "record and play" and it locked up the same way.
Although I am getting 5 volts to the RAM - I wonder if it's even registering it?
Any ideas on what pins I can check?

There is a guy on eBay that is selling this memory and I will buy them to see what happens. Although I think it'll be odd that both RAM chips are fried.

-Rev