Crackling noises on my EMU on some keys

[andyfox]

Hello guys,
My Emulator II started to behave very strange lately. On some samples, I am hearing bad noises in -let's stay- 2-3 notes of a sample. The noise is something like crackling and it's repeating (looping) if I keep the key pressed, with long patches. Going up or down on the scale makes the crackling repeating noise to disappear. I am getting the crackling noises on many patches, on different pitches.
Emulator started to behave like this after a "stop" of about 1 year and half. I tried to keep it a cool environment during studio refurbishing but I am afraid last summer it got a some very hot days up there in the attic.
Could this be the IC or some bad chips?
I have the HxC floppy drive.
Is there a guide in order to check EII memory with HFE image?

Thanks for your help!
Andy

[Electro disco club]

Yes , there IS the memory test disc that Can detects fautly ram ic.

Maybe it IS ceramic  capacitor on output board.

Try to compare individual voice output and main output when the problem comes. Do that , you will b? able to Know if it IS analog board or digital board ( which contains ram).

[andyfox]

Hello. Thanks you for your reply!
I will do some tests and post the responses here.

Thanks! 

[who]

Based on my experience, I am fairly certain it is a bad memory chip.  Do a search hear and you'll probably find your answer.

[andyfox]

Hello guys, while trying to search for memory test disc that can detects fautly ram ic... I am attaching a sample of what I hear while playing a patch.
By the way, is there a place where I can find the aforementioned disks? I replaced the floppy drive with SDcard reader so I would need the HFE images if possible..

Thanks for your help!

[andyfox]

Hello, just updating on the topic. I used the memory test disk and found an error:

Err BnkA 1 10000
Data: 05 S/B: 01

So.
What would you do ? First trying to swap and identify the chip with the procedure, or.. just try to plug / clean / re-plug on the sockets?
I feel worried since I am not an expert, I am afraid to damage things.

Thanks for your precious help.

Andy

[andyfox]

Hello guys,
I managed to do some steps.
So I tried to identify the bad IC

Err BnkA 1 10000
Data: 05 S/B: 01

so, referring to the memory map I found here (thanks to this guy  Greg Simon
https://docs.google.com/spreadsheets/d/1dU0NTIzw6Fg_wg8bjRz3fXhCf5AssWG2_Ci6Ft7hG3w/edit#gid=0

Address Low 10000 | Address High 17FFF | Segment 2 | IC 32-39 | Digial (main) board

Now, trying to identify the correct chip from the given error:

Data: 05 S/B: 01
so:
05 (hex) is 0000 0101 (binary) ← this is what actually was read.
01 (hex) is 0000 0001 (binary) ← this is what should have been read from RAM

So, there is a difference in bit 2 (start to count from the right, 3rd position: 0, 1, 2)
So from the schema of the Emulator II, looking for MD0BN.d and replacing "n" with the bit number (page 22 of 26, "Dynamic Ram") seems: IC 37 (MD0B2.D)

Ok, I reseated and cleaned IC37: same error.
I swapped IC 36 with IC37: same error.

Do you think I have to change the whole IC segment?
Thanks for your help

Andy

[Jab7747]

Andy, I have similar crackling going on with my EII. Where did you find the Memory Test Disk you mentioned?

Any help appreciated!
Jay

[andyfox]

Hello Jab, my EII is equipped with HxC floppy drive Emulator and SD Card. So I downloaded an HFE image.
http://www.emxp.net/Additional_downloads.htm ---> Emulator II ZM325 Memory Test Disk File

But I want to advise you, the floppy/image testing program seems bugged.
In my case, testing halted as soon as scan was starting, crashing.

So I bought the EII Debug EPROM.
I changed the original boot EPROM on IC42 with the debug one.
Then I connected a serial null modem cable DB9 / DB25 from COM port on my pc to serial port on EMULATOR II.
You have to pay attention to pins wiring.

Then I ran on my terminal program in Windows, I used "Termite", and set it to:
9600 baud, 7 databits, 2 stop bits, no-parity, RTS/CTS Flow, Append CR-LF

Turning on the Emulator, you should see something like this:

Emulator 2 Main CPU Debuggin Monitor
Version 0.00 ? August 4, 1984
CRT Interface and ROM work (obviously)
Checking static RAM
Static RAM OK ? Type ?HE? for help
>

then you have to type:

T M 0 + enter

and it gave me another RAM error address.
So I investigating from there, I think the resulting error code is "true" now.

Andy
 

[Jab7747]

Hi Andy,

I really appreciate the help and details! For the DB9 Female to DB25 Male Null Modem Serial Cable will this cable and pin out work or will I need modify it?

https://www.showmecables.com/db9-female-to-db25-male-null-modem-serial-cable-6-ft?gclid=CjwKCAiA9tyQBhAIEiwA6tdCrESutRcgh6zGGHBYSWWXuMVWPnnxnwEJMW--oBA6zU0msmd3IQTP9hoCZgMQAvD_BwE

Thanks,
Jay

[andyfox]

Hello!

no I am afraid it won't work. Pins must meet specs on the following cable. This is what I bought.
https://www.amazon.it/gp/product/B08C9TXXCK/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Please have a look at specs in .PNG attached to this post.

Andy

[Jab7747]

Andy, perfect, I?ll order that cable and the debug IC and hopefully get as far as you have at least with the troubleshooting. Please let me know if you end up figuring out the root problem and I?ll do the same.

Thanks again,
J

[andyfox]

Hello Jab,
I am pretty sure an entire row of DRAM is gone.  That's why I ordered some IC replacements.
I am waiting for them to arrive, and keep you posted.

Andy

[andyfox]

Guys, I can happily say that the EII is now working again!
I was able to identify the wrong RAM chip and changed an entire row of chips of the piggy board.
I used the DEBUG ROM, the memory disk was not able to identify it correctly and was hanging while working.
Now the sound is perfect.
I also had the technician to recap the PSU with new condensers!
Had to order custom ones since they were made specifically for that PSU (taller and thinner than the ones you can find today).

Thanks to everybody who helped me and addressed me correctly since the beginning.

Andy

[Jab7747]

Hi Andy, great news! Hey can you share what chip manufacture/part number was used for the IC32-39 replacement of the original 4164 DRAM chip? And where you purchased from? Seems like there are a lot of resellers and different ICs out there and don?t want to buy the wrong ones. Also, saw you replaced some IC?s on the piggy back board, which I don?t have on my REV 1 digital board in my E2 so hopefully won?t have that to figure out.

Thanks, Jay