anybody ever seen these problems?

[kb]

Ok, I know this is a longshot, but I'll ask.

Over a year ago, I bought a dead Drumulator off ebay.  Basically, I wanted the case because it was in nice condition and I was 'Frankensteining' another Drumulator with perfect inner workings but a hacked case.

So I made one shiny nice Drumulator (with MIDI!) out of the parts of 2 and sold that nice one on ebay ($120, not bad back then).  I still had the dead Drumulator with the hacked case, so I thought it'd just be a parts unit.

Well, last week I thought I'd try to resurrect the dead Drumulator (continuing my Dr Frankenstein ways, I guess).  It was dead apparently because several of the IC's had significant corrosion on their pins and underneath and it just wouldn't boot up.

The pain of the Drumulator is that it was designed to be inexpensive, so all the parts are soldered in (very few sockets).  Since it wouldn't boot, I started with the corroded IC's near the microprocessor and memory, a 74ls138 and a 2114 memory chip.  I desoldered them, put in sockets, and replaced the chips with spares.  And it booted!  It now plays drum sounds, checks out with most of the button presses, but still has some weirdnesses:

- Every time it boots up, I get a 'bad' on the display.  I do the 'poof' memory clear, but everytime you cycle power it still comes back up (I checked the battery voltage On and Off and it's a solid 3V).

- I can change the Level and Accent with the slider and the display will change from 0-15, but the Tempo just will not change from 13 using the slider.  Playback of all segments and songs happens at this slowest tempo - and there's no way I can change it.

- When I press 'External Clock' it will say EC on the left display, but not '01' on the right display.

It's weird, because most everything else works as you'd expect.  I think it's a memory problem, but I've swapped out the main 6116 memory chips with good ones, as well as the 2114 chip.  I don't think it has to do with many of the other chips with corrosion, because they are involved with drum sound playback, which seems to be working great.

I'm going to keep hacking at this, but thought I'd throw this out there.

Once I get this working, there's a bunch of mods I want to try on the Drumulator to affect the sounds, but I really would like the sequencer to be working before I dive in.

Thanks!

[kb]

Never mind - found it to be a bad via in the PCB.  It was near the corroded chips that I replaced.  It ran to the chip select of one of the SRAM chips.  I ran a jumper through the bad via after I sucked out the solder, soldered the jumper to the connecting traces and now it runs quite nicely.

Off to mod!

One note:  mounting pots in the Drumulator seems not so easy, since the chassis polymer(?) is pretty thick.

[bedouin]

Congratulations.  Glad you got it working.

[rokuez]

Never mind - found it to be a bad via in the PCB.  It was near the corroded chips that I replaced.  It ran to the chip select of one of the SRAM chips.  I ran a jumper through the bad via after I sucked out the solder, soldered the jumper to the connecting traces and now it runs quite nicely.

Off to mod!

One note:  mounting pots in the Drumulator seems not so easy, since the chassis polymer(?) is pretty thick.

I had a bad via as well for my drumulator, which is why it was displaying bAD.  Even tho the correct voltage was coming from the battery

[dr.c]

A "BAD" means that the battery is dead and the backup static ram datas are corrupted. You just have to change the battery and make a reset, and here ya go !

The tempo is made out of a multivibrator wich change its frequency when you change the pot position.
Does the display indication change when you change the tempo

Why do all you people just change components around ? What's the matter with you all ?

[kb]

Um, well, in my original message I did say that I checked the battery, it was solid 3V and I did a reset and I still got the corruption.  So it _wasn't_ the battery.

and I don't understand your last statement? the pcb was corroded so swapping out the ICs fixed much of the problem...?

[rokuez]

did you check the pads to make sure they pass current.  I had a bad via (basically the solder on the pad had corroded / deteriorated and wasn't passing any current)  & I had to get the soldering iron out reheat the pad (letting the solder flow/become liquid again) so that it would reform and pass curent

if you have a multi meter perhaps check the pads / pathways across certain points to make sure the proper amount of current and voltage is passing.  if you find a pad/solder point with infinite resistance you will have a bad via like I did.

[dr.c]

Gee... sorry about that ! This message was originaly intended to an EIII user here wich started to swap components around and I don't know how this message arrived here !

I maybe did a paste without wanting, by mistake, I don't know, I just don't drink...

Regards !

[kb]

no sweat!  these are all good tips. 

sometimes I do swap chips first thing because they are socketed and it's easy to do.  when I have to pull out the iron and the multimeter and the schematics and the scope, well, that's usually the right way to to do it, but I'm lazy!

at some point, I'll get back to that Drumulator - it now works fine, but I started planning some mods to it and got sidetracked on other stuff.

will post up when those mods are done!