thoughts on Digitech Space Station eprom copying?

[qwerty8787]

I'm back home and I made some experiments:

I burned on a 27C256-15 the XP300 code. Burning went fine (double checked checksum when burned), and if I put it instead of XP200's eprom, I get the right number of programs (40).
But the sound works only in bypass, because there's only 1 RAM IC. If I throw in the other IC, same old story. It doesn't boots.

I checked the connection on every pin of the new RAM sockets. everything's fine. Also dc voltage appears correctly on the right pins.

Tried to look at some other pins with the oscilloscope, but the only thing I get is digital crap (oh..really?  )

Diggin with the oscilloscope I found that on Vdd I have a strong ripple. about 400mVac (RMS) measured with the multimeter. This ripple is also visible on the "digital crap", and I don't think it is a good thing.... Anyone ever tried to measure ripple on DC rails?

Tantalum caps installed. C61, C65, C60. C64 was already there.

I also installed also the MC34064P that arrived this week, and with this I get pedal stuck at boot, with a double zero on the screen.

It's getting really frustrating....

[Govmnt_Lacky]

@qwerty

This is my recommendation....

- Install the ORIGINAL xp200 EPROM chip into U9
- Install the ORIGINAL D41464-10 RAM chip into U19 (Leave all other RAM chips out)

Power up the pedal and see if it works. If it does not... try a new EPROM in U9 and retest. If it still does not work.... put original EPROM back into U9 and try different RAM in U19. If it still does not work, then there MUST be something wrong with your mod work.

If the pedal DOES work when you do the above, then you may have a BAD set of RAM chips that are causing issues when you install them. Or, your newly burned EPROM chip(s) are bad or not burned correctly.

The XP300 will ONLY work properly if ALL 4 RAM chips are installed and working. Refer to my previous post about this.

Perhaps you could post a picture of your pedal's PCB and we might be able to spot something 

[qwerty8787]

original XP200 EPROM + original RAM ----> OK
original XP200 EPROM + new RAM --------> OK
original XP200 EPROM + original RAM + new RAMs in other sockets ----> doesn't boot (random segments on screen)
burned XP300 EPROM + original RAM ----> Boot ok BUT sound only in bypass mode. when not bypass I get different distorted sound depending on program selected (That's right, not enough RAM...)
burned XP300 EPROM + 1 new RAM ----> same as before
burned XP300 EPROM + original RAM + new RAMs in other sockets ----> doesn't boot (random screen)

I can see about 400mVrms of ripple on digital +5V rail. then:

whatever combination + MC34064P -------> Pedals restarts over and over again

whatever combination + MC34064P + 10000uF cap on digital +5V rail ------> less ripple on rail (about 100mVrms), pedal restarts over and over but from one boot to another there's more time.


I can manage to make some photos soon

[qwerty8787]

found the problem: PSU. 
That crappy power adaptor (that came with the pedal, bought used) had a loose connector, that caused some voltage loss or other strange artifacts.
Tried to power the whole thing with another trusty PSU: everything's just fine 

with XP300 eprom (and all 4 RAM in) is just perfect!

Now I have to troubleshoot my XP-ALL+ board, but I feel much better now 

Thanks Govmnt_Lacky and digi2t for helping me!

[digi2t]

No problem man. Glad you figured it out. I would have never guessed the PS. Way to stick with it.

Let us know how your conversion goes, and if the build doc needs to be edited.

Cheers,
Dino

[DJGlukBH]

Just to continue - I had success using 27C512 instead of 27C256. Just wrote the bin starting from 8000 in programmer's utility. One memory chip worked fine.

But stacking two 27c512 with such programming approach lead to chip's death. I think only 27c256 could be stacked one on top of another.

[Govmnt_Lacky]

@DJ

I think the 512 chip is a good way to go if you ONLY want to have a 2 program pedal (i.e. XP100/300, XP200/300, etc)

If you want all 4, then stacking the 256 chips -OR- using the 27C1001 is the way to go 

BTW.... Just to share a bit of good info, I recently picked up a programmer off eBay that works GREAT. It is the TL866CS and it works just fine on the 27C256 chips and many more. Plus, it is only about $30-40 from China 

[qwerty8787]

Hi again everyone,

anyone experiencing power issues with the XP-ALL+ mod?
Recently modded an XP100 and seems like the regulators are getting pretty hot. After some minutes on, it will occasionally gets crazy in the screen and stops responding to footswitches.
letting it off to cool down for a while will let the unit come back again, but it will eventually fail again.
Any hints?

[Govmnt_Lacky]

Hi again everyone,

anyone experiencing power issues with the XP-ALL+ mod?
Recently modded an XP100 and seems like the regulators are getting pretty hot. After some minutes on, it will occasionally gets crazy in the screen and stops responding to footswitches.
letting it off to cool down for a while will let the unit come back again, but it will eventually fail again.
Any hints?

Can you possibly post a picture of the modded board? I think I may know what your problem is 

[qwerty8787]

I'm without camera right now, I will try soon.
What are you thinkin about?

[Govmnt_Lacky]

What are you thinkin about?

Where you picked up your Ground to switch in and out of the XP100 program that is located within the CPU mask.

[qwerty8787]

I made the XP-ALL+, the one with 27c1001. No switch, only 4-pos rotary switch. And GND for it is taken from the Vss pin of the 27c1001.

[qwerty8787]

measuring temperature on U11 heatsink: 72 °C 

[Govmnt_Lacky]

Pictures would help a lot. 

[qwerty8787]

What's the temperature on your regulators?

Anyway, no matter what's the cause of this high temperature, I just solved it moving the regulators on the chassis via cables, attached with screws (with thermal grease between chassis and regulators). Now temperature hardly goes over 35 °C 

This helped me a lot with stability. Heat brought strange artifacts after the mod. Recommended 

[digi2t]

What's the temperature on your regulators?

Anyway, no matter what's the cause of this high temperature, I just solved it moving the regulators on the chassis via cables, attached with screws (with thermal grease between chassis and regulators). Now temperature hardly goes over 35 °C 

This helped me a lot with stability. Heat brought strange artifacts after the mod. Recommended 

Never had a problem with this. We're not adding any significant load here, other than LED's, if used. Even then, the regulator is more than capable than handling this.  I would back trace to see if something is drawing too much current. Solder bridge jumps to mind.

[digi2t]

Well, just for kicks, I plugged in my XP-ALL+ today, and left it on for almost 6 hours. It never glitched once.

I believe that maybe the regulator might be on it's way out, since you previously had a power supply problem, or there must be a grounding problem somewhere in your unit.

If need be, look in my information folder in the gallery (under Dino's Stuff), and you'll find the schematics for all the XP units. It will help you troubleshoot your power problem.

In my experience, I've never had a regulator over heat due to the conversion, and to my knowledge, neither has G_L. After all, we're not making any big demands on the regulator, other than powering LED's, if installed. One of the reasons that I went with 3mm LED's as well. If no LED's are installed, the regulator should be loaded the same as it was before the conversion.

[digi2t]

Edit post above... I forgot it plugged in.

It's been two days now. 

Still works fine, no glitching. 

[Govmnt_Lacky]

I agree with Digi2t...

If you performed the mod correctly, the regulator should NOT be getting hot at all!

[digi2t]

I errored when I said;

After all, we're not making any big demands on the regulator, other than powering LED's, if installed.

I forgot about the relay for the stereo switching in 100 mode.

Even though, I've left my unit on, in 100 mode, for the day. So far, no glitch.

FWIW, I used the Omron G5V-1 (5VDC) micro relay. The coil only pulls 30mA at 5vdc, the regulator should handle the added load fine. It has in mine. If you're using the stereo mod, maybe look at the relay you've chosen (if it isn't the above stated), that might be your problem. Another good choice would be the Nais TK1-5V. PCB mount pins, like the Omron, much lower physical profile, and the coil only pulls 28mA.