Tek CSA7404/TDS7000 repair project (Upgraded memory/CPU)

[Jwalling]

Hello all
I have 2 TDS8000B, also failed in PPC board, about debug LED, one board stopped in".8",and nothing output from serial port,maybe PPC CPU failured,I just want to give up, the other LED stopped in "A",and serial port message also shows "NVRAM test failed".I just replaced failure backup battery on NVRAM chip,but it still failed on same position.
Who can tell me how to do next?

Post the exact failure/data from the console port. I've had to replace several of those Dallas/Maxim chips that failed.

Jay

[TiN]

Well, you replaced NVRAMs, that's good. But there are one more  step to do, covered in article. Try it and let us know.

[Jwalling]

Well, you replaced NVRAMs, that's good. But there are one more  step to do, covered in article. Try it and let us know.

I think he only repaced the battery, TiN. At least that what is sounds like...

Jay

[mrf245]

Hello all
I have 2 TDS8000B, also failed in PPC board, about debug LED, one board stopped in".8",and nothing output from serial port,maybe PPC CPU failured,I just want to give up, the other LED stopped in "A",and serial port message also shows "NVRAM test failed".I just replaced failure backup battery on NVRAM chip,but it still failed on same position.
Who can tell me how to do next?

Post the exact failure/data from the console port. I've had to replace several of those Dallas/Maxim chips that failed.

Jay

Thank you,you means I need replace whole NVRAM chip no only battery on it?Is it damaged?

[mrf245]

Well, you replaced NVRAMs, that's good. But there are one more  step to do, covered in article. Try it and let us know.

Thanks answer from Taiwan, I can't open you link,maybe should use VPN here (you know in mainland)? Could you introduce your link general?

[TiN]

Well, you can reference first post in this thread, which covers all required details as well.

[mrf245]

Well, you can reference first post in this thread, which covers all required details as well.

You first post no referenced to replace NVRAM chip.My serial messages show below. Should I replace whole chip?

[TiN]

Seems so.
Then you have to write configuration to NVRAM via console.

[Jwalling]

Thank you,you means I need replace whole NVRAM chip no only battery on it?Is it damaged?

Damaged, no. But it appears to be defective after seeing your console port output. Looks to have a stuck data bit. The ones I've to replace were surface mount parts. I'd be curious if yours is too.

Jay

[mrf245]

Thank you,you means I need replace whole NVRAM chip no only battery on it?Is it damaged?

Damaged, no. But it appears to be defective after seeing your console port output. Looks to have a stuck data bit. The ones I've to replace were surface mount parts. I'd be curious if yours is too.

Jay

I guess its same as you. You have replaced whole SMD part? This one is not easy to order.

[TheSteve]

I bought my replacement nvram from eBay, it was older stock but was new and has been working great. It was also pretty cheap.

[Jwalling]

Thank you,you means I need replace whole NVRAM chip no only battery on it?Is it damaged?

Damaged, no. But it appears to be defective after seeing your console port output. Looks to have a stuck data bit. The ones I've to replace were surface mount parts. I'd be curious if yours is too.

Jay

I guess its same as you. You have replaced whole SMD part? This one is not easy to order.

Yes, but a hot air rework station helped me.  Why is it not easy to order? They seem to be readily available...

I have several bad ones with stuck bits. The next time I need one, I'm going to try and replace the TSOP SRAM on the underside of the board and save some money. I think they're only a couple of bucks versus $39 for the module from Digikey. You could try and do the same. I'll take a look this morning at one and let you know what the device is.

EDIT: the device is Cypress CY62128LL-70ZC. Cypress doesn't make that part anymore, but this one should be a suitable replacement: http://www.digikey.com/product-detail/en/cypress-semiconductor-corp/CY62128ELL-45ZXI/428-2040-ND/1205235


Jay

[TiN]

I used regular iron with wide tip to remove chip. No hotair craze

[Jwalling]

I used regular iron with wide tip to remove chip. No hotair craze

Holy crap, you work fast! I couldn't even see the tip on your iron to comment!
Jay

[mrf245]

Yes, but a hot air rework station helped me.  Why is it not easy to order? They seem to be readily available...

I have several bad ones with stuck bits. The next time I need one, I'm going to try and replace the TSOP SRAM on the underside of the board and save some money. I think they're only a couple of bucks versus $39 for the module from Digikey. You could try and do the same. I'll take a look this morning at one and let you know what the device is.

EDIT: the device is Cypress CY62128LL-70ZC. Cypress doesn't make that part anymore, but this one should be a suitable replacement: http://www.digikey.com/product-detail/en/cypress-semiconductor-corp/CY62128ELL-45ZXI/428-2040-ND/1205235


Jay

OK, I also find this RAM chip on local Taobao shop, the oscilloscope now store in my friend house,next time I will deal with it again.
And I also think remove this Dallas chip, best choose is iron with more tin on a side of pin, hot air sometimes will damage other components around (some net problem,I cant see TIN's video,I guess we use the same method)

[TheSteve]

I also prefer to use a large tip to remove parts like the nvram. Add a little extra solder and then heat all of the pins and lift one side up carefully. Remove the excess solder so that side is now free. You can then heat all of the pins on the second side and lift it off. It is pretty easy with a little practice.

BH7JUO - nice to meet you here, 73 de VE7FM

[Jwalling]

I also prefer to use a large tip to remove parts like the nvram. Add a little extra solder and then heat all of the pins and lift one side up carefully. Remove the excess solder so that side is now free. You can then heat all of the pins on the second side and lift it off. It is pretty easy with a little practice.

BH7JUO - nice to meet you here, 73 de VE7FM

Never tried this. Got a picture of the tip you use? TiN's video was way too fast to see what he uses. The length down one side of this particular device is almost 1" !
Jay

[TiN]

You can hit magic button pause. I used ERSA 4.2mm chisel to remove chip and ERSA 102PDLF0.4 to solder pins on new one.

[Jwalling]

You can hit magic button pause.

It was too fast to even pause! I think it needs a frame-by-frame button 

I used ERSA 4.2mm chisel to remove chip and ERSA 102PDLF0.4 to solder pins on new one.

4.2mm would only do 5 pins or so at a time. I was thinking you heated the whole side at a time. Am I being thick? 

Jay

[TheSteve]

You can hit magic button pause.

It was too fast to even pause! I think it needs a frame-by-frame button 

I used ERSA 4.2mm chisel to remove chip and ERSA 102PDLF0.4 to solder pins on new one.

4.2mm would only do 5 pins or so at a time. I was thinking you heated the whole side at a time. Am I being thick? 

Jay

4.2mm sounds about right. I can post a picture of my tip tonight. In my case I lay a bead of solder along all of the pins to help hold some heat. I then just run the iron back and forth to flow all of the solder and then lift it up about 1mm. It probably sounds a little scary but it really works great and just needs a little practice. I have hot air equipment as well but in the case of the nvram I prefer the soldering iron method.

[TiN]

Put big solder blob on a side and toss it with tip from corner to corner to melt all pins side. Carefully lift released side bit up. Switch other side, do same. After few iterations, chip pins will be free from PCB. Important not to apply any force, that will rip pads apart from PCB.

After some practice, you can remove chips in seconds. Use wide chisel tip is to maximize heat transfer from iron. It's all about thermal transfer and surface area. Seeing iron settings any higher than 300? always make me cry.

[mrf245]

I also prefer to use a large tip to remove parts like the nvram. Add a little extra solder and then heat all of the pins and lift one side up carefully. Remove the excess solder so that side is now free. You can then heat all of the pins on the second side and lift it off. It is pretty easy with a little practice.

BH7JUO - nice to meet you here, 73 de VE7FM

Nice to meet you too, VE7FM.This desoldering method also apply to some TQFP chips(not too much pins),I tried to dismantle some chips (like STM32 MCU)success with it

[RichardGV]

Hi,

My TDS7404 (Win98) booted up fine several weeks ago.  It has always been plugged in.  Well, it was unplugged for a couple weeks and now it won't boot.  The screen is completely blank with all the front panel buttons and such lit up. The floppy whirs a bit, then there are 2 beeps, then nothing.  I plugged in a keyboard to see if some key combos would at least get the display to do something, but nothing has worked.

Any ideas what the problem could be?  Again, it booted up fine a couple of weeks ago, and the only thing that has changed is that it was unplugged from the wall.  I can imagine that the NVRAM battery could be dead, but would that cause the display to be completely blank?

Do any of you know of some troubleshooting procedures?

Thanks!!

Richard

[TiN]

Your x86 PC took a sick pill. I'd take the covers off, search for any bad parts, replace CMOS 3V battery cell and replace electrolytic caps around CPU socket. Then power it back on and check if it boots. If not check voltages from PSU. X86 pc and OS must be bootable even without correct NVRAM on PPC board.

[Jwalling]

Hi,

My TDS7404 (Win98) booted up fine several weeks ago.  It has always been plugged in.  Well, it was unplugged for a couple weeks and now it won't boot.  The screen is completely blank with all the front panel buttons and such lit up. The floppy whirs a bit, then there are 2 beeps, then nothing.  I plugged in a keyboard to see if some key combos would at least get the display to do something, but nothing has worked.

Any ideas what the problem could be?  Again, it booted up fine a couple of weeks ago, and the only thing that has changed is that it was unplugged from the wall.  I can imagine that the NVRAM battery could be dead, but would that cause the display to be completely blank?

Do any of you know of some troubleshooting procedures?

Thanks!!

Richard

Hook a monitor up to the SVGA port. Do you get video there? I suspect that you will, and see that the MB is reporting a CMOS checksum error.

Jay