Valve FX preamp mishap: Damaged memory DIP chip?

[Janus Alfador]

I was backing up the firmware for my rack devices, and after backing up my VFX FX firmware, turning on the device again it emitted a loud buzz noise and not normal sound.

I have two Valve FX', so I tried swapping the firmware chips from one to another to see if I had damaged that chip. The other VFX worked normally with either firmware chip in it, and the first VFX had the same issue with either firmware chip in it. Also, both firmware chips read just fine in my EPROM reader. So, I concluded that the firmware chip wasn't damaged and that it must be something else.

By the way, I used chip pullers to remove the chip and touched ground with my fingers before working inside the preamp.

So, I looked around the area where I was working to see what else might be culprit. The most likely chip to have come in contact with my fingers while re-installing the firmware chip is a, SEC-brand 32-pin memory chip right next to the firmware chip.




The memory chip is KM681000BLP-7L in one VFX and is KM681000CLP-7L in the other. I'm guessing the B vs C only means the C is a newer version and either B or C should work in either preamp.

Looking it up, the chip is 128K x8 bit Low Power CMOS Static RAM, and is made by Samsung. The chip is readily available for purchase and is inexpensive:

https://www.utsource.net/itm/p/1710803.html?digipart=1

However, I'd like to get opinions on whether it would be the extent of the issue.


I also noticed that the LCD present names for the VFX which wasn't working properly had some garbled characters in them.

After thinking that memory chip could be the issue, I decided to try swapping them between my VFXs. Fortunately, it is socketed and not soldered. So, I pulled them, and swapped them. When I swapped them, the VFX that had been still working normally had a very faded LCD screen that didn't load up properly. It just went through a semi loading process and then said Valve FX on it. The other FVX also didn't load properly, though.

So, I swapped the chips back, and now the VFX that had been working properly also doesn't pass sound but emits a loud buzzing noise and doesn't show anything on its screen at all, it's just blank. And the VFX that was the first to not work properly shows what the other VFX did with the same chip in it - a very faded screen that doesn't load-up properly, and just says Valve FX on it.


So, my impression here is that the memory chip from the first VFX to not work properly could have received slight static damage from my touching it while pressing the firmware chip back in after copying it. And that when I pulled the memory chip to swap it with the other VFX' memory chip, that it received further static damage (which is why it first produced bad noise and some garbled characters, but then wouldn't load at all and had a very faded screen). And that the memory chip for the VFX that was still working properly while the other wasn't also got damaged while I was swapping them.

I touched ground between each chip swap that I did, thinking that would discharge any static in my fingers and make it safe to handle these chips. I now think I should wear rubber gloves when handling them. The chips are labelled "low power", so I wonder if that means they are especially sensitive to any amount of electricity that might pass through fingers.

What do you think?



Update:

I've looked closely at the area where I removed the firmware and memory chips, and I don't see anything else that could have plausibly been touched. The smaller soldered chip below the firmware chip in the photo is a lot lower profile and its leads would not be easy to touch even if trying to. And the square chips in brown sockets to the left of the firmware chip are recessed and their leads protected from contact even if a finger is pressing down on them. And since swapping the memory chips seems to cause the particular LCD screen behaviour to follow the chips, I hope replacing them fixes the problem.

I've ordered 4 replacement KM681000CLP-7L chips for around $13.50 shipped.

[Enzo]

Before anything, do a reintitialization. A "restore factory settings" or equivalent.

[Janus Alfador]

I actually wanted to leave that as a last resort because I have lots of presets I really like on those preamps and I haven't backed them up.

Also, I looked up how to do a factory reset for the VFX, and the instructions I found required using the on-screen menus for it. I don't know if there's another way to do it that doesn't depend on having usage of the LCD.

Here's the reinitialization instructions: https://www.manualslib.com/manual/38...page=67#manual

I wonder if removing the battery for some time will also reinitialize it.

[Enzo]

Usually removing the battery blanks memory causing the need to reinit.

[Janus Alfador]

I've just re-seated the firmware and memory chips on the VFX' many times. After re-seating the firmware chip on one of them, the screen came on with full text brightness like it's supposed to. However, the preamp didn't work properly. But, I was able to get a bunch of seemingly error messages off of the screen.

After I copied those messages down, I tried re-seating the memory chip, and after that the screen went back to being very faded. That doesn't make a lot of sense: re-seating the firmware chip made the screen appear normal again, and then re-seating the memory chip made it faded like it was before.


Anyway, here are the messages I got from the screen:


1 Unkn cmd 59 cnt=246 pi=9d8d

1 Unkn cmd fb cnt=213 pi=9eae

1 Unkn cmd dd cnt=212 pi=9eaf

1 Unkn cmd 5e cnt=211 pi=9eb0



pip=ba00



p=0
fi=22
0 01:9d88

p=0
fi=22
p=03:9d88



Too many DRAM offset lines



All of the "1 Unkn cmd 5e cnt=211 pi=9eb0" type commands I got on separate power-downs and power-ups. Each time I would power it down and then power it up again I got a different one of the 4 I've listed above. The other messages I got while pressing the Exit button or scrolling the parameter wheel. The LCD would cycle through, I think, 3 messages while either repeatedly pressing the Exit button or scrolling with the parameter wheel.

The two messages in this format:

p=0
fi=22
p=03:9d88

I think they were from different power-on cycles, too.

I'm concerned about continuing to re-seat the memory chip because some of its leads are getting pretty soft and have been bent and needed to be bent back into place multiple times. If I keep doing it, they might break off. Those are the chips I've ordered 4 replacements of.

[The Dude]

Check the socket, also. I've had to clean and rework the socket pins on those in the past. I've used contact cleaner and a dental pick to carefully bend them out. It's possible that they are no longer making good contact with the chip.

[drewl]

Check your low voltage power supplies for the heck of it.

I know the screen on these can have problems over the years, but it wouldn't throw error codes.

[Philington]

I know the last post on this thread is almost a year old, but I am looking for some help with my Valve FX.
I get the debug characters, including the "Too many DRAM offset lines" almost every time I turn on the unit (just like Janus reported in the earlier post). I've seen this reported in other forums also. If I reset the Valve FX (hold down "Store" button while powering on, then pressing the "Up" arrow) and then reinitializing, the unit works perfectly. I, of course, don't want to do this each time I turn on the unit - I lose any presets I have created.

I purchased new in the late 80's I think - it is version 1.03. I also have the Control One foot controller, by the way. I hadn't used the Valve FX in a while, so the internal battery was completely dead - I successfully replaced, and I was hoping it would address my issue, but it did not. I contacted Harman/Digitech - their repair centers tell me they are all out of the v1.04 EProms.

Janus - did you ever install the new memory chip you ordered, and did it solve your issue(s)?

Does anyone else have any ideas? I have rediscovered this amp and I am loving the sounds.

[g1]

The battery may be new, but that doesn't necessarily mean it's voltage is getting where it's supposed to. Did you check? Is there a schematic available?

[Philington]

Here is part of the schematic. See 3V - the battery is just a coin-sized CR2032. The connection makes its way up to the memory chip, which could be bad. in any case, I'm not sure where or how to check the voltage.

[Enzo]

Not difficult. Check for 3v on top of the coin, then at the cathode of D2 WITH THE POWER OFF. And ultimately at pn 32 of the IC.

[Philington]

Hey g1 and Enzo -
I never checked the voltage. Instead, I went ahead and ordered a replacement SRAM chip - Samsung KM681000CLP-7L. I got it from a place called Jameco, which is 10 miles away from me (SF Bay Area - not far from the SF Airport). Well, the SRAM was the issue - it was either bad or seated badly (although it looked like it was seated well). I haven't tested the original.

So - it works great now!!! No issues at all anymore - very happy.
Janus (OP) was a huge help with his posts here and on another forum. Thank You!

So, I also purchased a new EPROM from Jameco and programmed firmware 1.04 onto it. Does anyone have any idea what the difference is between v1.03 and v1.04? I don't want to stick the new 1.04 EPROM in the unit if the risk isn't worth it.

[Jazz P Bass]

" Does anyone have any idea what the difference is between v1.03 and v1.04?'
I would think a call to Digitech should answer that for you.

[Out2Lunch]

Hey g1 and Enzo -
I never checked the voltage. Instead, I went ahead and ordered a replacement SRAM chip - Samsung KM681000CLP-7L. I got it from a place called Jameco, which is 10 miles away from me (SF Bay Area - not far from the SF Airport). Well, the SRAM was the issue - it was either bad or seated badly (although it looked like it was seated well). I haven't tested the original.

So - it works great now!!! No issues at all anymore - very happy.
Janus (OP) was a huge help with his posts here and on another forum. Thank You!

So, I also purchased a new EPROM from Jameco and programmed firmware 1.04 onto it. Does anyone have any idea what the difference is between v1.03 and v1.04? I don't want to stick the new 1.04 EPROM in the unit if the risk isn't worth it.

Hey Philington, I'm late to the party but I am hoping you (or others here) might be able to help me. I too am having the same issue with my unit as you described (or the same symptoms at least). Was it difficult to install the sram chip? Of course I am not certain this would solve things but I am not sure what else to do (besides take it to the local vintage repair shop)

Thx!

[g1]

Was it difficult to install the sram chip? Of course I am not certain this would solve things but I am not sure what else to do (besides take it to the local vintage repair shop)

Philington referred to the 'seating' of the chip, which means it is socketed and no soldering is required. You remove the old one and insert the new one into the socket, being careful not to bend any of the pins.
They are also very static sensitive, you you need to follow standard CMOS safety precautions (google it).
Jameco still has the chips and they are fairly cheap: https://www.jameco.com/z/KM681000CLP...2_2302615.html