Share your knowledge on these two classic MPCs
By skylab001 Sat Dec 05, 2009 9:53 pm
I just noticed today for the first time, sample retention. I had not noticed it previously, it seemed to always string samples that were in memory....or so I thought. It happened when I was sampling a bunch of keys and no percussion or drums, It faintly played back drums. The machine was just turned on and no disk had been loaded since yesterday. So this has me thinking that there is somewhere in circuit that is holding a low charge when the device is off allowing a chip to retain these samples. I also noticed a little distortion in the sounds which is something I have found in other devices that retain sound on a ram chip and the power is low. I have a couple battery powered devices that I have made in the past that will record small 8-bit phrases and when the battery begins to die the audio gets more distorted and eventually becomes noise. So either the RAM is retaining or there is another IC, maybe a sample and hold chip that has the ability to retain the samples as well.....maybe a sampling buffer......or gasp.....the DSP?? Since my knowledge of digital circuits is small and the MPC is much like an 80's computer I hope a tech with MPC60 experience who knows the circuit may lend some advice as to what chip or part of the circuit has potential to be storing these sample. That could get us closer to knowing what the problem is.
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By peterpiper Sat Dec 05, 2009 11:51 pm
skylab001 wrote:I just noticed today for the first time, sample retention. I had not noticed it previously, it seemed to always string samples that were in memory....or so I thought. It happened when I was sampling a bunch of keys and no percussion or drums, It faintly played back drums. The machine was just turned on and no disk had been loaded since yesterday. So this has me thinking that there is somewhere in circuit that is holding a low charge when the device is off allowing a chip to retain these samples.


Damn that sounds spooky. If I get you right, the samples dont really die when the machine is powered off. So there are ZOMBIE SAMPLES walking around iin your 60. Damn :shock:

peace
By Toe Sun Dec 06, 2009 9:38 am
This problem was getting on my nerves, but now I know its due Zombie samples its all good, Zombies a cool. :D

" Yo dude that beat is sick "
" of course, I got the undead living in my mpc "
By master-ceo Sun Dec 06, 2009 12:27 pm
Return of the living Sample! :evil:

I heard somebody mention the DSP before in another thread. Where is that chip located?
Left or right board?

Is that the chip that process samples?
By skylab001 Sat Dec 19, 2009 2:01 am
I've been trying to dig deeper into this issue. I actually had taken my 60II to VST in Pasadena and had them fix it (since I'm not as good with digital circuits). So I thought...... They removed my RAM expansion and told me that it was the source of my problem, noise and ghost samples. They charged me almost what I paid for the the 60II. I got it home and after about a half hour, it started doing the exact same thing again. Frustrated I contacted VST and went back and forth with their head tech until he basically told me that the 60/60II is a first gen machine with a slow processor and that they were quirky and they do strange things with no explanation. Basically to me that was a hands in the air 'don't know, don't care' and of course they already had my money.

So I feel a little ripped about that, but I've since loaned my memory to a friend for testing, and absolutely no problems in his machine, so it's not the memory. I have visually inspected my machine and found a few cracked ceramic caps that I replaced, but I don't think that was the issue. I also noticed this strange grey discoloration on a lot of the caps on the input/stereo output board.

http://www.flickr.com/photos/39482223@N ... otostream/

Not sure if those need replacing but I will be testing. I'm curious if anybody else has noticed this in a 60II. It may be normal? So let me know if you've seen this. It will save me time.

Has anybody noticed if the ram chips get warm or not after a few minutes, I did notice that they were giving off a bit of heat, but that could be normal?

Seriously I'm going to do what I can to figure this issue out, and if it's not repairable so be it, at least we'll know, so if anybody else has any info about this post it here or let me know.

And last but not least does anybody have an disc image of the diagnostic floppy I can get?
By mpc3000le Sat Dec 19, 2009 11:59 pm
skylab001 wrote:
http://www.flickr.com/photos/39482223@N ... otostream/

Not sure if those need replacing but I will be testing. I'm curious if anybody else has noticed this in a 60II. It may be normal? So let me know if you've seen this. It will save me time.


These CAPS are not related to the section of circuitry that is possibly causing the problem.

skylab001 wrote:Has anybody noticed if the ram chips get warm or not after a few minutes, I did notice that they were giving off a bit of heat, but that could be normal?


RAM of that vintage can get a bit warm.

If you feel it to be suspect then shotgun the lot with fresh chips.

skylab001 wrote:Seriously I'm going to do what I can to figure this issue out, and if it's not repairable so be it, at least we'll know, so if anybody else has any info about this post it here or let me know.


I have my suspicions that the problem is related a little bit to a code exception being triggered due to aging components.

skylab001 wrote:And last but not least does anybody have an disc image of the diagnostic floppy I can get?


Whilst the test disk image would be of general use to have around.

It is not going to help you in this instance.

The "apparent" "sample retention", "ghosts in the machine" and "zombie samples" are happening as a result of reasons the test disk will be unlikely to assist with where trouble shooting is concerned.

Rohan
By skylab001 Sun Dec 20, 2009 2:49 am
These CAPS are not related to the section of circuitry that is possibly causing the problem.


Understandable but I was curious of the discoloration, I have since checked them and they do seem ok, I was more curious if anybody else has the same discoloration. My initial thought was that they overheated due to some other faults I found, so I more or less wanted to see if anybody else has had the same discoloration. I have not seen CAPS that looked like that before.

I have found a few issues on my voice board and my stereo I/O board due to a few failing electrolytics. These were difficult to find originally due to the fact that they had pushed the whole casing up rather than just the top of the cap.

RAM of that vintage can get a bit warm.

If you feel it to be suspect then shotgun the lot with fresh chips.


I have already swapped all 6 RAM chips with new chips for good measure just to rule that one out. They are working fine, I just noticed they radiated a little heat, but I hadn't paid much attention before the swap.

I have my suspicions that the problem is related a little bit to a code exception being triggered due to aging components.


Wouldn't it be nice for all those afflicted to know which aging components are the cause and be able to swap them if possible. I have a local shop who has many of the chips or what seem to be usable replacements for the voice and cpu board. So if I can figure out the proper chips to swap I will do it. I would just prefer not to swap every chip on board.

I've been told that the voice chips or dsp could be part of the problem, and that they are not available, I was also told RAM was not available. DSP was a custom part, but the shop owner mentioned that if I could find somebody to pull the binary off of the voice eprom chips, and burn it to new chips, that he has replacements that would work.

It does seem logical that the writable chips could fail over time due to their volatile nature.


Whilst the test disk image would be of general use to have around.

It is not going to help you in this instance.

The "apparent" "sample retention", "ghosts in the machine" and "zombie samples" are happening as a result of reasons the test disk will be unlikely to assist with where trouble shooting is concerned.


While this is true, I would like to have it to do the RAM checks and for calibration purposes as well as some other troubleshooting if I need to. I will not be returning to VST.
By mpc3000le Sun Dec 20, 2009 3:32 am
EPROMS fail over time.

Their read speed can become slow, they can drop bits and a whole lot more.

Read out the VOICE CHIP EPROMS with a ROM READER.

Blow a new, pin compatibe and "faster" set.

Stick the replacment set in the machine.

Out of curiosity.

What is the marked access speed of the currently installed OS and VOICE BOARD ROMS ?

Rohan
By sequoia1232 Sun Dec 20, 2009 3:34 am
Skylab, I'd love to help you sort this, as I'm pretty frustrated with it too. Thanks for taking up the cause.

I don't have my 60 with me at the moment, are the voice chips socketed? If so, I can probably get you a binary. I'll have a look at them when I get home...
Last edited by sequoia1232 on Sun Dec 20, 2009 3:40 am, edited 1 time in total.
By skylab001 Mon Dec 21, 2009 6:07 am
Sequoia1232 do you have the capability to burn eproms as well or just read them? If the voice chips are the problem would it cause issues to read the binary from a faulty chip? Would it be better to read chips from a healthy machine? The eproms for OS and the Voice board on my 60II are all 150ns. I can get the same speed or a little faster, 120, 100, or 90ns. I'm curious if all the users with this issue have the same rev. voice chips? Mine are v1.0, but I don't know if there was a higher rev. It seems like a simple place to start before going through the other IC's in the voice circuit. After that my thought would be on one of the many demux chips in the voice circuit, does that sound off base?

I really hadn't thought it was an issue with the OS chips, but I guess it could be just as easily as anything else, but I thought I had read that somebody had this issue under the older OS as well as the new. Has anybody ever contacted roger linn about this?

I guess I was targeting the voice board first since every other part of my MPC seems solid.
By mpc3000le Mon Dec 21, 2009 2:15 pm
skylab001 wrote:Sequoia1232 do you have the capability to burn eproms as well or just read them?


Generally speaking.

If you have the ability to read a ROM then...
...you have the ability to write a ROM also.

My crystal ball tells me that Sequoia1232 has such an ability :-)

skylab001 wrote:If the voice chips are the problem would it cause issues to read the binary from a faulty chip? Would it be better to read chips from a healthy machine?


Best to take a READ from a machine in a known working state.

skylab001 wrote:The eproms for OS and the Voice board on my 60II are all 150ns. I can get the same speed or a little faster, 120, 100, or 90ns. I'm curious if all the users with this issue have the same rev. voice chips? Mine are v1.0, but I don't know if there was a higher rev.


150ns is fine and fast enough.

All MPC60 VOICE BOARD ROMS are at REV 1.0 from what I have researched.

skylab001 wrote:It seems like a simple place to start before going through the other IC's in the voice circuit. After that my thought would be on one of the many demux chips in the voice circuit, does that sound off base?


I don't think the chips you are looking at are the problem.

skylab001 wrote:I really hadn't thought it was an issue with the OS chips, but I guess it could be just as easily as anything else, but I thought I had read that somebody had this issue under the older OS as well as the new.


Don't think it is bad OS chips.

skylab001 wrote:Has anybody ever contacted roger linn about this?


Not personally although others on this forum may have in the past and kept answers to themselves.

Anyone who purchased 3.10e from him is entitled to ask a technical support question of him.

skylab001 wrote:I guess I was targeting the voice board first since every other part of my MPC seems solid.


A fair place to target too.

I have seen this problem now on MK1 an MKII machines.

Whilst I don't think the voice board EPROMS are entirely at fault, refreshing them would not be bad thing to do given their age.

More as I think of it.

Rohan.