Tektronix TDS2014B repair

[TheKellerman]

Hi,

I got a TDS2014B that is not booting up. The three green LEDs light up and the frequency on the probe comp is 1.8kHz.
Initially I thought the firmware got corrupted so I desoldered the flash and reflashed it with the FW from a TDS1001C (as described here: https://www.eevblog.com/forum/testgear/tektronix-tds1000b-series-hacks/). But the scope is still not booting.

The UART near the USB controller shows this output:

Code: [Select]

dprint driver V0.a

ApLoader_Version=DevB6809

fwupdate V0.8

Firmware length = 9cf8, checksum = fd89

Calculated Checksum = 0000*****

cypRunApp received, resetting ...˜€æ€`ž�†øf憞``Æøfæ†~fž`†f�˜)û

Tektronix Nautilus Driver: Ap_Version= 1.053

Giving message to 68K = 0x000d, = runAppOK:::::::;

dprint driver V0.a

ApLoader_Version=DevB6809

fwupdate V0.8

Firmware length = 9cf8, checksum = fd89

Calculated Checksum = 0000****

cypRunApp received, resetting ...*˜€æ€`ž�†øf憞``Æøfæ†~fž`†f�˜)û

Tektronix Nautilus Driver: Ap_Version= 1.053

Giving message to 68K = 0x000d, = runAppOK:::::;*******************************

dprint off

So it tries three times and gives up. Before reflashing the main flash, the output was the same (but it was resetting forever, not only three times). It also had Firmware length = 9cf8, checksum = fd89.
It seems the "Firmware length" does not refer to the main firmware.

There is also a small i2c flash on the board. Maybe there is the problem? When the right adapter arrives I will read the i2c flash.

Could someone with a working TDS2000B/C please connect to the UART and post the output? 56000 baud, 8 data, 1 stop, no parity


Greetings

[mikehank]

Your error script looks like incompatible  or corrupt FW.

[TheKellerman]

Yes it looks like it, but replacing the original FW with the FW from a C model made no difference. So I wonder why the expected FW length and checksum is the same.

I checked the i2c EEPROM and the content is the same as here https://www.eevblog.com/forum/testgear/tektronix-tds1000b-series-hacks/msg2021134/#msg2021134

Any suggestions on what to check next?

[mikehank]

Dart boarding here but maybe the volatile memory.  These scopes are more than 15 years old and memory doesn't last forever.

[Fieroluke]

“CypRunApp” points to the Cypress USB Controller.

The way I understand it from the Cypress datasheet this is a completely autonomous processor. It seems to boot from the I2C close to it. This would allow it to take over control and possibly tri-state the 68000 (DMA) and then access the Flash directly. I would guess that it leaves at least the last 64K of the flash ($7Fxxxx) alone since this is where model code, serial number, filter coefficients, etc. are stored. If it tri-states the 68K and then crashes, the scope will appear dead.

Some people had corrosion on the USB processor and had it die. I don’t know if that’s what’s wrong with your scope…

[tautech]

Any suggestions on what to check next?

Corrosion.
I have a TDS2012B that with their convection cooling and vented upper case allowed some muck to fall into the scope and onto an IC pin where is sat for years absorbing atmospheric moisture and finally corroding through the IC pin.
Quite difficult to find as it was just a dark spot on a SMD IC lead but when cleaned with a scalpel is was evident it was corroded completely through.
I no longer have any top vented convection cooled equipment.

[mikehank]

Yes convection cooling is a bad idea.  These scope were never my favorite.  They aren't very good performance wise and are surprisingly hard to fix.

[66bono]

I've already assembled an oscilloscope like, I don't want to risk it. As I continue to experiment, I will read the memory.

[TheKellerman]

Corrosion

I found some dried goo around pins 21 and 22 on U400 (the NS chip). The Cypress looks ok so far. Cleaning everything made no difference.

Also I noticed a significant delay between the lines "Firmware length = 9cf8, checksum = fd89" and "Calculated Checksum = 0000*****" so i assume thats when the Cypress is reading some data.
And Checsum 0000 indicates that it didn't got any data, right?

[sean0118]

Are power supply voltages stable?

[TheKellerman]

Yes, I checked all the voltages according to the service manual and everything is stable.

[TheKellerman]

I think I now understand the UART log. It seems like the i2c EEPROM for the Cypress is divided into two parts, the ApLoader (at the start) and the actual Ap  (starting at 0x10004 with the length 0x9cf8).
During the delay between the lines "Firmware length = 9cf8, checksum = fd89" and "Calculated Checksum = 0000*****" the Cypress is accessing the EEPROM but there is something wrong with the SDA line as it sometimes cant reach 3.3V and goes only to about 1V (see attachments).

Any ideas on what could cause this? I cant find any other chip on the i2c that would pull the signal low. And my TL866 could read the EEPROM just fine.

[analogRF]

Hi,

I got a TDS2014B that is not booting up. The three green LEDs light up and the frequency on the probe comp is 1.8kHz.
Initially I thought the firmware got corrupted so I desoldered the flash and reflashed it with the FW from a TDS1001C (as described here: https://www.eevblog.com/forum/testgear/tektronix-tds1000b-series-hacks/). But the scope is still not booting.

The UART near the USB controller shows this output:

Code: [Select]

dprint driver V0.a

ApLoader_Version=DevB6809

fwupdate V0.8

Firmware length = 9cf8, checksum = fd89

Calculated Checksum = 0000*****

cypRunApp received, resetting ...˜€æ€`ž�†øf憞``Æøfæ†~fž`†f�˜)û

Tektronix Nautilus Driver: Ap_Version= 1.053

Giving message to 68K = 0x000d, = runAppOK:::::::;

dprint driver V0.a

ApLoader_Version=DevB6809

fwupdate V0.8

Firmware length = 9cf8, checksum = fd89

Calculated Checksum = 0000****

cypRunApp received, resetting ...*˜€æ€`ž�†øf憞``Æøfæ†~fž`†f�˜)û

Tektronix Nautilus Driver: Ap_Version= 1.053

Giving message to 68K = 0x000d, = runAppOK:::::;*******************************

dprint off

So it tries three times and gives up. Before reflashing the main flash, the output was the same (but it was resetting forever, not only three times). It also had Firmware length = 9cf8, checksum = fd89.
It seems the "Firmware length" does not refer to the main firmware.

There is also a small i2c flash on the board. Maybe there is the problem? When the right adapter arrives I will read the i2c flash.

Could someone with a working TDS2000B/C please connect to the UART and post the output? 56000 baud, 8 data, 1 stop, no parity


Greetings

I am getting a similar log on that same UART on TDS3034C but my scope boots fine and passes self test. However, it generates a "System error occured" and the USB port does not work at all (has power). But this error does not even show up in the full self test (it passes).

I am out of ideas at this point...is there another debug port that shows the log of the main scope firmware?

[analogRF]

the cypress chip in my scope is CY7C67300-100AXI and there is no I2C eeprom next to it 
I can only see an IDT71V016 (64Kx16) SRAM next to it. Unless the eeprom is on the back of the board?

[TheKellerman]

I revisited the repair and was able to get it running. The problem was indeed the main firmware. I flashed the FW from a working B model and now its booting up. So the FW from a TDS1001C-EDU will not run on a B or regular C model.

Interesting to note is that the USB is working fine but the cypress still reports "Calculated Checksum = 0000****"

[analogRF]

I revisited the repair and was able to get it running. The problem was indeed the main firmware. I flashed the FW from a working B model and now its booting up. So the FW from a TDS1001C-EDU will not run on a B or regular C model.

Interesting to note is that the USB is working fine but the cypress still reports "Calculated Checksum = 0000****"

so do you mean that earlier boot log didnt change even though the scope now works fine?

[Brandy]

My Tek 2014B didn't start either, also no LEDs during startup, but a gentle click noise from inside the scope.
On the power supply C23 was defective, should have 120uF/25V and was 55nF.
I replaced it with 220uF / 25V and the device started up normally.
In fact I've replaced all caps, just in case.