TDS754d not booting anymore.

[AwArD_RzD]

Just make sense to put my problem there (original post before the scope stopped working) https://www.eevblog.com/forum/testgear/hackingupgrading-old-scope-%28tds754d%29/

Replaced the nvram, everything was good, worked for an hour (power cycled 3-4 time to do some test) , powered off, took a break powered on, don't boot anymore....

(copy from the other thread)

---------
Well that didn't last long...   

Did some test worked great power off the scope, take a 1 hour eating break. Baby sleeping still have time to do more test, power the scope go to the bathroom 2 min come back, all the led still on, no screen, no response. Reboot same thing.... 

Reopen the scope led display stuck to .8, if i cycle the unit fast sometime i have a .E , or a .8 .E .8 sequence showing very fast or a weird c (a,f,g segment on).

what i did before (for anyone not following this post), Hacked the scope for the 2m 2c option, worked great for a month till today, replaced the ds1250 Nvram by a fresh one with the backup of the old one.

Troubleshooting.
2 fan blowing on the scope case open.

-Tried to cycle the scope many time.    Same thing
-Replaced the fresh nvram with the old working one.   Same thing
-All the cable are tight in the right slot.
-Waited 5 minute, same state, tried to talk via GPIB, got an error, the scope dosen't reply..

Start to read the service PDF.

-All voltage OK
-All voltage look good on my other scope.
-Frequency good at the pin 25 of the J2 connector.
-Tried the s1001 switch with the help of some other post on the Tek forum. Same thing.
-Tried many combination with other board removed. Same thing.

With all the troubleshooting and following the flow chart the only thing this manual screaming is Replace the A11 DRAM Processor/Display module.

Checked the thermal signature with my E4 and nothing weird show up... No cap leak and nothing out of place visually.

I have the impression that the cpu is stuck on reset or briked. I tried to probe the Nvram to see if the CPU toggle the CSn pin and nothing happen.....

damn.. never again ... if it ain’t broke, don’t fix it     

For now i have a 16 Kg paper weight, if someone have an idea....

------------

I see many post about the console port, but no one say what kind of rs-232 cable you need for that after connecting the opt 13 board to the edge connector, last time i used a serial port it was for my 1200 baud modem in 1989.... so not many experience with that. I searched in the manual to know if the scope is DCE or DTE for the communication but found nothing, the only thing i know it's the opt 13 rs-232 is used for the hard copy with some software.

[nctnico]

Look for the TDS520B component service manual to find the meaning of the 8. Perhaps you dropped a bit of solder somewhere which now shorts a signal somewhere.

[poot36]

Try turning the scope upside down and shaking it.  See if anything falls out.  If that does not work try blowing it out with high pressure air.  Some flux can be conductive at higher frequencys so make sure it is all cleaned off.  If all else fails attach a logic analyzer to the data and address bus and see where it is getting hung up.

[AwArD_RzD]

Look for the TDS520B component service manual to find the meaning of the 8. Perhaps you dropped a bit of solder somewhere which now shorts a signal somewhere.

.8 tell me that "Displayed at power-up or reset". the system seem to be stuck in this mode, i tested the power monitor (TL7705A) at the U1175 and i'm not sure if it work correctly, the 5V is applied the reference is 2.5V and the RESET output is at 0V but the RESETn (inverted) is at 700 mV. The reset IN (from the cpu i guess) is at 5 volt so the cpu don't reset this chip but the inverted signal seem to match the non inverted one....

Tried some dip switch combination like the running led, skip bootrom test, skip bus error timeout test, skip timer interrupt, skip all kernel ram test, skip all kernel test and nothing still the same behavior, .8 nothing change....

The TDS520B manual mention a power fail who tell the cpu to reset  but i don't know how or where to find this on the board for the tds754d, the manual for the TDS520B have many more schematic, flow chart or drawing of the board itself and even if some of the thing look the same the cpu by itself have more pin and i find nothing in the service manual.

Try turning the scope upside down and shaking it.  See if anything falls out.  If that does not work try blowing it out with high pressure air.  Some flux can be conductive at higher frequencys so make sure it is all cleaned off.  If all else fails attach a logic analyzer to the data and address bus and see where it is getting hung up.

Shaked the scope nothing fell off, i did the soldering a month ago and socketed the old nvram, the scope worked perfectly for a whole month, took my 10x glass and i don't see any pin bridged or solder.


I tested the ribbon cable and no problem there, i didn't remember but my gf told me that i have put the scope in the case before eating (i didn't remember that) but if it's true the fault maybe related with that but i don't see any pin bent or thing missing inside or found on the bench.

[AwArD_RzD]

what kind of rs-232 cable i need (null modem/normal) to use the console port like this post (http://www1.tek.com/forum/viewtopic.php?f=5&t=5526&st=0&sk=t&sd=a&start=30), i probed the address directly on the edge connector and something happening for maybe 600 ms and stop.

is the information on this post accurate ? or is there anywhere i can find the genuine console port ?


Edit:

Update :  i soldered some wire to the console port and plugged them like Garibeos said in the last page of the tek forum, i don't have a rs-232 cable so i used the scope to see if something happen and .... nothing, i see some pin stuck at -9v and +9v. Still need to find what kind of cable i need to communicate with my pc.

[AwArD_RzD]

Hoo yeah something new.

Been 3 hour since i try to get something on the terminal and playing with the dip switch something happenend and there the log

PCMCIA option board detected.
FLOPPY: Detected

Adding 7162 symbols for standalone.


CPU: 68EC040.  Processor #0.
Memory Size: 0x1000000.  BSP version 1.0.

Executing Smalltalk
-> Executing Diagnostics from Menu

  Dsp Instr mem size
  Dsp D2 mem size
  Dsp D1 mem size
  Dsy Vect0 mem size
  Dsy Vect1 mem size
  Dsy Wfm0 mem size
  Dsy Wfm1 mem size
  Dsy Text0 mem size
  Dsy Text1 mem size
  Acq number of digitizers
  Acq mem size
  Cpu timer interval uSec
  Cpu Dram size
  NvRam mem size
  Limit to 1GS/sec presence
  Opt Math Package presence
  Opt Telecom Masks presence
  Opt 3C presence
  Opt 4C presence
  Opt RS232/ Cent presence
  Opt 1M presence
  Opt 2M presence
  Acq Intlv Cal Id presence
  Opt TvTrig presence
  Opt TvTrig index
  Dsy color presence
  Opt floppy drive presence
  Opt hard drive presence
  Acq number of user channels
dspForcedBus ................... pass
cpuDiagD2MiscReg ............... pass
cpuDiagDSPIntMaskReg ........... pass
cpuDiagD1D2Access .............. pass
cpuDiagDsyAccess ............... pass
dsp68kMemTest .................. pass
cpuDiagFIFOMem ................. pass
dspRunVerify ................... pass
dspBusRequestTest .............. pass
dspImplicitBusAccess ........... pass
dspTristarMemTest .............. pass
dsyDiagPM100Reg ................ pass
dsyPM011RegMem ................. pass
dsyLCSRamdacRegMem ............. pass
dsyMonoRamdacRegMem ............ UNTESTED
dsyVGARamdacRegMem ............. pass
dsyDiagPPRegMem ................ pass
dsyDiagRasRegMem ............... pass
dsyDiagAllMem .................. ***FAIL***
..error details:
ERRORID: 163 diagnostic test failure dsyBitBltRules
** addr = 0x80207fe  exp data = 0x55  actual = 0x5555
** addr = 0x80208fe  exp data = 0x55  actual = 0x5555
** addr = 0x80209fe  exp data = 0x55  actual = 0x5555
** addr = 0x80213fe  exp data = 0x55  actual = 0x5555
** addr = 0x8021bfe  exp data = 0x55  actual = 0x5555
** addr = 0x80228fe  exp data = 0x55  actual = 0x5555
** addr = 0x80230fe  exp data = 0x55  actual = 0x5555
** addr = 0x8023afe  exp data = 0x55  actual = 0x5555
BitBlt rules failure to Text Planes

calLibrarianDefaultCk .......... pass
dspForcedBus ................... pass
acqProcThermistor .............. pass
twoGHz50OhmOvldConf ............ UNTESTED
trigGtlRegisterDiag ............ pass
trigBtlRegisterDiag ............ pass
ch1LogicTypeComp ............... pass
ch2LogicTypeComp ............... pass
ch3LogicTypeComp ............... pass
ch4LogicTypeComp ............... pass
ch1EdgeTrigDiag ................ pass
lineTrigDiag ................... pass
dlyTrigDBETrigAfter ............ pass
dlyTrigDBTRunsAfter ............ pass
slewrateTrigDiag ............... pass
trigAttenSerialReg ............. pass
trigPreampSerialReg ............ pass
trigDTCSerialReg ............... pass
trigExtlSerialReg .............. pass
trigDacSerialReg ............... pass
TICountersDiag ................. pass
gtlBigCountersDiag ............. pass
trigBtlConfidenceDiag .......... pass
trigGtlCompRamDiag ............. pass
digRegisterConf ................ pass
digDataFormatConf .............. pass
digSpeedMemConf ................ pass
digAcqSubSampleConf ............ pass
digAcqPeakDetectConf ........... pass
digAcqHiResConf ................ pass
digAcqMemDataConf .............. pass
digAcqMemAddrConf .............. pass
digInterruptConf ............... pass
digA2DConnectsConf ............. pass
digHFStepConf .................. pass
glitchTrigDiag ................. pass
pulseWidthDiag ................. pass
trigNibDiag .................... pass
digInstaVuXYConf ............... pass
fpDiagConf ..................... pass
optDiagPM110Reg ................ pass
optDiagFloppyCacheMem .......... pass
optDiagFloppyControllerIO ...... pass
optDiagFloppyDrive ............. pass
optRS232DuartIO ................ UNTESTED
optRS232DuartIntLoop ........... UNTESTED
optCentronCntrlReg ............. UNTESTED
optTv8bitRegDiag ............... UNTESTED
optTvShiftRegDiag .............. UNTESTED
optTvXparentCodes .............. UNTESTED
optTvDontCareCodes ............. UNTESTED
optTvEdgeAndLevel .............. UNTESTED
optTvSyncLevels ................ UNTESTED
hwAccountant probe routines
  Probe for unexpected pending ints
  Dsp Instr mem size
  Dsp D2 mem size
  Dsp D1 mem size
  Dsy Vect0 mem size
  Dsy Vect1 mem size
  Dsy Wfm0 mem size
  Dsy Wfm1 mem size
  Dsy Text0 mem size
  Dsy Text1 mem size
  Acq number of digitizers
  Acq mem size
  Cpu timer interval uSec
  Cpu Dram size
  NvRam mem size
  Limit to 1GS/sec presence
  Opt Math Package presence
  Opt Telecom Masks presence
  Opt 3C presence
  Opt 4C presence
  Opt RS232/ Cent presence
  Opt 1M presence
  Opt 2M presence
  Acq Intlv Cal Id presence
  Opt TvTrig presence
  Opt TvTrig index
  Dsy color presence
  Opt floppy drive presence
  Opt hard drive presence
  Acq number of user channels
can't open input 'fd0:/startup.bat'
  errno = 0x13 (S_errno_ENODEV)

Smalltalk/V Sun Version 1.12
Copyright (C) 1990 Object Technology International Inc.

Bus Error
Program Counter: 0x0534b268
Status Register: 0x3000
Access Address : 0x0c1cfff6
Special Status : 0x0105
Task: 0x53ac1d8 "V main"
504cac0 _vxTaskEntry   +10 : _shell (1, 0, 0, 0, 0, 0, 0, 0, 0, 0)
5028390 _shell         +138: 50283ae ([1, 0, 0, 50281b4, 0])
50284a2 _shell         +24a: _ledRead (5ff3df4, 5ff646e, 80)
5054564 _ledRead       +126: _read (0, 5ff62bd, 1)
50259fa _read          +10 : _iosRead ([0, 5ff62bd, 1, 5ff644c, 505456a])
502097e _iosRead       +78 : _tyCoDevCreate ([536af34, 5ff62bd, 1, 5ff6268, 5025a00])
5003398 _tyCoDevCreate +100: _semQPut ([536af34, 5ff62bd, 1, 5ff6254, 5020980])
tShell restarted.

-> PCMCIA option board detected.
Fundefined symbol: option
-> LOPPY: Detected
undefined symbol: LOPPY
->
Adding 7162 symbols for standalone.
undefined symbol: Adding

->
-> CPU: 68EC040.  Processor #0.
undefined symbol: CPU
-> emory Size: 0x1000000.  BSP version 1.0.

undefined symbol: Size
-> Executing Smalltalk
-undefined symbol: Smalltalk
-> > Executing Diagnostics from Menu
syntax error
->
->   Dsp Instr mem size
 undefined symbol: Instr
->  Dsp D2 mem size
 undefined symbol: D2
->  Dsp D1 mem size
 undefined symbol: D1
->  Dsy Vect0 mem size
 undefined symbol: Vect0
->  Dsy Vect1 mem size
 undefined symbol: Vect1
->  Dsy Wfm0 mem size
 undefined symbol: Wfm0
->  Dsy Wfm1 mem size
 undefined symbol: Wfm1
->  Dsy Text0 mem size
 undefined symbol: Text0
->  Dsy Text1 mem size
 undefined symbol: Text1
->  Acq number of digitizers
 undefined symbol: number
->  Acq mem size
 undefi Cpu imer inevaluSec
 Cpu Dram sze
  NvRmmem size
 Limit to 1S/se presnce
  OptMath Pckae presence  Opt Telom Masks pesence
  O 3C presnce
  Opt C prsence  Opt RS23/ Cent peence
  Opt1M presenc
  Ot 2Mpresence
 Acq Intlval Id presnce
  Opt vTrigpresnce
  OptTvTrig inx
  Dsy coor presenc
  Ot flopy drive pesence
 Ot hard drve presenc
  cq numer of userchanneldpForcedBus................. ass
cpuDiaD2MiscReg............. pass
cuDiagSPInMaskReg .......... ass
cpDiaD1D2Access.............pass
cuDiagDsyAces .............. ass
dsp68keTest ............... pass
cuDagFIFOem ............... ass
dspRunerify ................. pass
dpBusRequeTest ............ ass
dspImpicitBusAccss .......... pas
spTristarMmTes ............. as
dsyDiaPM100Reg ............. pass
syPM011egem ............... ass
dsyLCSamdaRegMe ............ pass
sMonoRamdcRegMem .......... NTESTED
dsVGARamdacRgMem ............ pss
dsyDiagPRegem .............. pass
dsDiagRasReem .............. pss
dsyDiagllMe ................ ***FAIL**
..err details:
RRORID: 16 diagnosti tet failre dsyBitBtRules
** ddr = 08207fe  expdata = 0x5  actual =05555
** ddr = 0x8008fe  expdata = 05  actual =0x5555
** ddr = 0x800fe  exp ata = 0x55 actual =0x5555
* ddr = 0x8013fe  exp ata = 0x55actual = x5555
** adr = 0x801bfe  xp ata = 0x55 actual = x5555
** dr = 0x8028fe  exp ata = 0x55 actul = x5555
** adr = 0x8020fe  exp dta= 0x55 actual = x5555
** adr = 0x82afe  exp dta = 0x55 actual = 0555
BitBt rules falure to Tet Planes
alLibrariaDefaultCk ......... ass
dspFcedBus ................ pass
cqProcTheristor .............pas
twoGH50OhmOvldCnf ........... UNTESED
trigGtleisterDia ........... pass
tigBtlRegiserDiag .......... pss
ch1LogiTypeComp ............. pass
c2ogicTypeomp .............. pss
ch3LogiTypeComp ............ pass
c4LogicTypeomp .............. ss
ch1EdgerigDiag .............. pass
lneTrigDig.................. pss
dlyTriDBETrigAftr .......... pass
dyTrigDBTRusAfter ........... pss
sleraeTrigDiag ............. pass
tiAttenSeralReg ............ ass
triPrampSerialRg ........... pass
tiDTCSeriaReg .............. ass
trgExlSerialReg............. pass
tigDaceriaReg .............. ass
TICounesDiag ............... pass
glBigCuntesDiag ............ ass
trigBtCofidenceiag ......... pass
tigGtlCmpRmDiag ............ ass
digRegstrConf .............. pass
dgDataFrmtConf ............. ass
digSpedMeConf .............. pass
dgAcqSubapleConf ........... ass
digAcqeaketectCnf .......... pass
dgAcqHiReonf ............... ass
digAcqemDaaConf............. pass
igAcqMemArConf ............. ass
digIntrrupConf ............. pass
igA2DConntsConf ............ ass
digHFSepCof ................ pass
litchTrigag ................ ass
pulseWdthDag ............... pass
rigNibDia................... ass
digInsaVuXConf.............. pass
pDiagConf................... ass
optDiaPM11Reg .............. pass
ptDiagFloyCacheMem ......... ass
optDiaFlopyConrollerIO ..... pass
ptDiagFloyDrive ............ ass
optRS32DuatIO .............. UNTESED
optRS2DuartIntLop .......... UNTESTD
optentrnCntrlReg ........... UNTESTEoptTv8bitRgDiag ............. UNTETED
ptTvShiftRgDiag .............NTESTED
opTvXparentodes ............ UTESTED
optvDontCareCdes ........... UNESTED
optTEdgeAndLevl ............ UNTETED
optTvSncLevels ............. UNTESED
hwAccoutant roberoutines
 Probe for nexpectedending ins
  Dsp Intr mem siz
  Ds D2 em size
  sp D1 mem ize
  Dsyect0 mem ize
  Dsy ect1 mem sze
  sy Wm0 mem siz
  Dsy Wfm mem size Dsy Text mem size
 Dsy Text1mem size Acq numberof digitiers
  Acq em size  pu timer iterval uSe
  Cpu Dra size
  Nvam mem sie
  Limit o 1GS/sec resnce
  pt Math Pakage presece
  Opt elcom Mass presence  Opt 3C pesence
  O 4C presece
  Opt R232/ Centpresence
Opt 1M preence
  Opt2M presenc
  Acq ntv Cal Id pesence
  pt TvTrig resenc
  pt TvTrig ndex
  Dsycoor presnce
  Optfloppy drie preence  Opt harddrivepresnce
  Acq umer of uer channe
can't opn input '0:/startupbat'
  ero = 0x13 (_errno_NDEV)

Smaltalk/V SunVersion 1.2
Copyigh (C) 1990 bject Techology Intrnational c.

Bus Eror
Progra Counter: x0534b28
tatus Regiter 0x300
Access Aress : 0xc1cfff6
Spcial Satu : 0x0105
ask: 0x53c1d "V man"

ned symbol: mem
->



for now i will let the scope powered on since it's the only time in the 200 power cycle where i got something. Got some stripe on the screen but now nothing, all led on but the led display flash with the upper and lower segment.

Any Scope God can tell me what happening, i see error but that tell me nothing...

Edit: Well tried to cycle the scope to see if this repeat and nop, still stuck to the .8 nothing on the console.....

[nctnico]

It shows a fail on the memory diagnostics. I'd use another scope and see what happens on the address and data lines of the CPU. If some logic levels only go half way then that is suspicious. Did you try to reflow the NVRAM socket? Add some flux and let the solder flow again.

[AwArD_RzD]

It shows a fail on the memory diagnostics. I'd use another scope and see what happens on the address and data lines of the CPU. If some logic levels only go half way then that is suspicious. Did you try to reflow the NVRAM socket? Add some flux and let the solder flow again.

Just got the datasheet and i will probe the pin this evening and will reflow the 2 side connector and the nvram to be sure it's not a cold joint somewhere.

[AwArD_RzD]

Did a reflow of the pin, did a good cleanup inspected the pin but this changed nothing.

Did some probing of the pin on the MCU, i was good the see the clock in and out, the reset is high so the thing is not stuck in reset, but i don't have steady hand and when i tried to probe some address/data i got some spark flying so i stopped doing that....

what exactly i need to see to know where/what hold the thing from booting? I did some debugging on 68000 cpu 10 year ago, but at that time i knew what the software was and what this supposed to do. I tried to cross reference the tds520 manual but even with the complete description i'm not sure where to start to see the complete picture of the failure, the dip switch code doesn't even work so the cpu stop at the very beginning i think.. i will cool my head for today and try to do a fresh start tomorow. I need to find bigger pin to see the bus.


Thanks for your advice nctnico your always there for the beginner like me !!

[poot36]

I would try testing the RAM and ROM chips if possible.  If not try resoldering the pins on the RAM and ROM chips.  I am going to suspect a bad RAM chip based on the test log that you got out of the serial port.  It could also be a bad data or address buffer chip if this scope uses them.  I would check all of the data and address bus pins to see if any are stuck high or low or are not making a full voltage transition.

[AwArD_RzD]

Did some poking this morning,

I started with the Nvram to see if there something happening and the 19 address pin are all at 5v, the data pin are a 1.9 volt (??) and no data is going in/out.

I was able to probe some data/address pin from the mcu there some data going on so the cpu do something but like i said yesterday i don't have steady hand so i limited myself with the via around to not cause some spark again.

I probed some sn74f245 around the cpu/nvram and the 15 i probed are all at the high impedance state, with the A/B side pin at 1.6 volt, the power pin is a 5v.

It's fun to probe around and look for the datasheet to understand what each chip do, but  if it's a cold solder joint somewhere (like Poot36 said) in this ocean of discrete ic, is this a better way to try to fix that by reflowing the whole board in my oven (did many video card like that) and does i need to remove all the connector, switch, 7 seg display before that or using the hot air gun will do the same thing (maybe some heat stress will occur).

And the killer question, i don't care to take time to probe and debug this thing out, it can be fun right ? but for the price i paid (around 700$) if i need it to use it one day this can cost me maybe more to pay someone with experience to do it, it is better to sell it in part to get my money back and buy another scope? the 300k waveform/sec and the 500 mhz bw was helpfull for my fpga project and my hantek ds5202b (only 2 channel) was not very good when debug in differential pair with fast data on it. I'm only an hobbyist but i like to play with professional stuff.... so i start to think i really need a good scope for that, but same spec in the keysight catalog go up to 10k if i go down to the 200mhz 4 chan range it can cost me 5k easy, is there better deal with these kind of spec ??

[nctnico]

Why not get another TDS500/TDS700 series? Maybe one with a bad display so you can make 1 working scope out of two.

Edit:
If you can figure out which device it being accessed on this address it should help to pinpoint the problem. It must be something really simple. It may be one of the address lines or a byte enable behind a buffer is stuck. Did you replace the NVRAM in an ESD safe environment?

Code: [Select]

dsyDiagAllMem .................. ***FAIL***
..error details:
ERRORID: 163 diagnostic test failure dsyBitBltRules
** addr = 0x80207fe  exp data = 0x55  actual = 0x5555
** addr = 0x80208fe  exp data = 0x55  actual = 0x5555
** addr = 0x80209fe  exp data = 0x55  actual = 0x5555
** addr = 0x80213fe  exp data = 0x55  actual = 0x5555
** addr = 0x8021bfe  exp data = 0x55  actual = 0x5555
** addr = 0x80228fe  exp data = 0x55  actual = 0x5555
** addr = 0x80230fe  exp data = 0x55  actual = 0x5555
** addr = 0x8023afe  exp data = 0x55  actual = 0x5555
BitBlt rules failure to Text Planes


[AwArD_RzD]

Why not get another TDS500/TDS700 series? Maybe one with a bad display so you can make 1 working scope out of two.

Edit:
If you can figure out which device it being accessed on this address it should help to pinpoint the problem. It must be something really simple. It may be one of the address lines or a byte enable behind a buffer is stuck. Did you replace the NVRAM in an ESD safe environment?

Code: [Select]

dsyDiagAllMem .................. ***FAIL***
..error details:
ERRORID: 163 diagnostic test failure dsyBitBltRules
** addr = 0x80207fe  exp data = 0x55  actual = 0x5555
** addr = 0x80208fe  exp data = 0x55  actual = 0x5555
** addr = 0x80209fe  exp data = 0x55  actual = 0x5555
** addr = 0x80213fe  exp data = 0x55  actual = 0x5555
** addr = 0x8021bfe  exp data = 0x55  actual = 0x5555
** addr = 0x80228fe  exp data = 0x55  actual = 0x5555
** addr = 0x80230fe  exp data = 0x55  actual = 0x5555
** addr = 0x8023afe  exp data = 0x55  actual = 0x5555
BitBlt rules failure to Text Planes


The only thing i have for the ESD is an antistatic mat on the bench and usually i always touch the casing of the scope with my arm when poking inside. Never had problem with esd (for now!!) but shit can happen... 

For the address i tried to find something on the internet with the bitblt, text planes, dsyBitBltRules, ERRORID: 163... but nothing show up. Found the address map at the page 62 of the TDS520 CM manual but it only say 0802 0000 – 0805 FFFF Text Plane so i'm not sure of what that mean but since i was good to see the console port once i assume this is a product of the failure and not the failure itself since when i repopulated the old nvram the scope still not boot. I think there 8 ram chip to the display, i need to check closer where the trace go to see if there a buffer or a bus control line where the video ram and something used at boot up cross path but without the schematic for this board i have some difficulty to cross reference even if some chip have the same pcb number on each board.

Buying another scope to make one crossed my mind but with the crappy exchange rate,the growing shipping price and the insane custom fee sometime, i'm not sure i want to take that path again well if the guy accept very low offer this can be a good choice, there some interesting one and since i'm sure the ACQ board and the 4 attenuator work this can be my part unit if i buy another one, the only thing i don't know is how the calibration suffer if i replace some part inside this one or another one...

[nctnico]

Text plane sounds like the video memory to me. Still if only the video memory would be bad it would boot so I think you are right: there is a more fundamental issue with the oscilloscope's CPU board. AFAIK the calibration is stored on the ACQ board in these scopes (TiN has more knowledge about that though) to exchanging the ACQ boards shouldn't be a problem.

[AwArD_RzD]

Text plane sounds like the video memory to me. Still if only the video memory would be bad it would boot so I think you are right: there is a more fundamental issue with the oscilloscope's CPU board. AFAIK the calibration is stored on the ACQ board in these scopes (TiN has more knowledge about that though) to exchanging the ACQ boards shouldn't be a problem.

Well nice to know i can swap these. I probably zaped a chip somewhere when i handled the thing. I started to look for a replacement this morning to feel the market and got another working Tds754d for a very good price (100$ less than my broken one) and the serial number is 2 number down from mine! Mine shipped the 31 may 2001 and the one i bought is from the 1 may 2001, what's the chance of that happening, so i hope to get the same 2m board inside, but this one will not be opened by me hahaha at least not before i equip myself with the minimum esd equipment for that. I don't take this chance anymore.

I will continue to troubleshoot this one, i'm sure one day it will work again or the part will end in the one i bought today if something happen with the attenuator or if i broke something on the run. I don't really care for the display, i use a 17 inch lcd monitor and the dpo mode is sooo beautifull to look at i can see my signal anywhere in the room.

My next step will be to look at the U2000 U2001 IC, the detailed Circuit Description in the 520 manual tell me that these chip handle interrupt/bus control and important bus logic timer (well they seem to handle everything) and it's interesting to see that the U2000 chip handle the DIP switch in the 520 so maybe this explain why i can't get the switch to work at all, strange thing there 6 of these ic (with all the same number on them) on the board in my TDS754D and 4 are near the Video part so maybe this explain why i got some error in the video memory map. It still a very fine pitch IC so i need to find where these trace go and i hope there some big pin at the end !

[poot36]

Before you go trying to re solder the chips try pressing on each one (or its pins) and powering on the scope.  I used this technique to find a intermittent pin on a RAM chip in a Super Nintendo.  If you don't want to use hot air you can use a chisel or fine conical tip on your soldering iron and heat up each pin(s) on all of the major chips on the CPU board.  Don't use any solder but flux is recommended.  Also check for chips that are getting hotter then normal they may be bad.  Alternatively I found a replacement parts scope on eBay in your province for relatively cheap http://www.ebay.ca/itm/TEKTRONIX-TDS754D-500-MHz-OSCILLOSCOPE-REF-696-/201398967029?hash=item2ee4505af5:g:JxoAAOSwLVZVqQW1#ht_2552wt_868.  Or just the CPU board (for a C version of this scope so it may not work): http://www.ebay.ca/itm/Tektronix-679-4003-00-DRAM-Processor-board-for-TDS-754C-Working-/141789258167?hash=item21034c61b7:g:0ZkAAOSwyQtVxoLZ#ht_60wt_1363.  Good luck on the repair.

[nctnico]

strange thing there 6 of these ic (with all the same number on them) on the board in my TDS754D and 4 are near the Video part so maybe this explain why i got some error in the video memory map.

If you look more closely at the schematics you'll see these chips have mode select pins. Tektronix designed a multi-function ASIC for various tasks on the processor board. Very clever because now they can order larger quantities and only have to pay for one mask set instead of 5 or 6.

[AwArD_RzD]

Before you go trying to re solder the chips try pressing on each one (or its pins) and powering on the scope.  I used this technique to find a intermittent pin on a RAM chip in a Super Nintendo.  If you don't want to use hot air you can use a chisel or fine conical tip on your soldering iron and heat up each pin(s) on all of the major chips on the CPU board.  Don't use any solder but flux is recommended.  Also check for chips that are getting hotter then normal they may be bad.  Alternatively I found a replacement parts scope on eBay in your province for relatively cheap http://www.ebay.ca/itm/TEKTRONIX-TDS754D-500-MHz-OSCILLOSCOPE-REF-696-/201398967029?hash=item2ee4505af5:g:JxoAAOSwLVZVqQW1#ht_2552wt_868.  Or just the CPU board (for a C version of this scope so it may not work): http://www.ebay.ca/itm/Tektronix-679-4003-00-DRAM-Processor-board-for-TDS-754C-Working-/141789258167?hash=item21034c61b7:g:0ZkAAOSwyQtVxoLZ#ht_60wt_1363.  Good luck on the repair.

Thanks for the link, the first one another member have send me the same link during the day, meanwhile i did an offer on a working one and got accepted (same shipping price), the second link the board is identical so now i need to ask me if i jump the gun or wait a little bit more, 2 working behemoth should save me some winter heating hahaha.

I tried to push many ic on the board and this changed nothing, even tried some gentle flex where the cable connect in case i cracked something in the reassembly but no luck, i remember to have some weird nozzle with my hot air gun this should be handy when heating the pin. 

I did some thermal imaging but found nothing weird, some chip was cooler than the other so i suspected no power but it's because they are stuck in the high impedance mode when i tested them.

[AwArD_RzD]

strange thing there 6 of these ic (with all the same number on them) on the board in my TDS754D and 4 are near the Video part so maybe this explain why i got some error in the video memory map.

If you look more closely at the schematics you'll see these chips have mode select pins. Tektronix designed a multi-function ASIC for various tasks on the processor board. Very clever because now they can order larger quantities and only have to pay for one mask set instead of 5 or 6.

Very cleaver indeed, this explain why i found nothing about these, only some aliexpress stuff where they sell them 9$ a piece.

[poot36]

If the chips that are cooler are supposed to be active when the scope is booting then that is a problem.  Try and figure out what is controlling them and work backwards from there.  If they are not supposed to be active then just ignore this comment.  If there is any standard logic chips on the board I would check the datasheets for them and probe them for correct operation.  I don't know if you want to go this far though it may not be worth your time.

[youxiaojie]

where is the console port for tds754d/784d? thanks.

[wn1fju]

Was there ever any answer to the no boot problem?

I have a TDS520 with EXACTLY the same symptoms:  Was working for a week, then no boot with the thing frozen.  Diagnostic LED = .8, although mine
got dimmer and dimmer and is currently blank (faulty LED driver chip perhaps?).  The Halt line of the 68020 uP shows that the processor halts a few
hundred milliseconds after turn-on.  Dallas DS1245Y NVRAM was replaced with a new one (from Mouser, not a Chinese counterfeit) programmed from
the old one.  Putting the old NVRAM back does not change the no boot.  Capacitors all look OK, but I replaced them all and scrubbed the board clean.

The diagnostic flow charts in the service manual suggest the first four bytes the processor reads out of the boot ROM are 00 20 7F FF.  I pulled the boot
RAM out and read it on my programmer.  I got 00 20 7F FE which disagrees.  So either the manual is wrong or my boot ROM is.  But I'm not sure whether
or not those four bytes are critical.  When I look at a few of the data lines, I see a few pulses at startup, then absolutely nothing (consistent with the
uP Halt).

It seems that as it was malfunctioning, it got worse and worse throughout the day.  It started out with the LED flashing a few characters, then it migrated
to the .8, and now blank.

Any help???

[poot36]

@wn1fju It sounds like your boot ROM is starting to corrupt itself.  Try reading it a few times and see if the content changes.  You can also try heating, cooling, and slightly changing the input voltage (if possible) it to see if that causes it to change the data in it.  Have you compared your current dump of the ROM to a known working one on the net if there is one?  I have had a UV erasable EPROM in a old 1990's serial terminal corrupt itself and even after I erased it for 20 min and then tried to reprogram the chip it did not program correctly and when I plugged it back into the terminal I watched as the terminal did boot but then the screen started to display garbage and then crashed shortly after due to the failing EPROM chip self corrupting its self.

[wn1fju]

@poot36:  I read the boot ROM on my TL866CS programmer several times in a row and got the same checksum; I didn't do a complete file compare.
The first few hundred bytes on the display didn't change, although I admit that is only a very small portion of the ROM.

I have ordered a replacement boot ROM supposedly "pulled from a working scope" (one has to wonder why someone would part out a working scope?)
from qservice in Greece who are reputable.

We will see if it makes a difference.  I'm inclined to believe Tek's manual specifying the first 4 bytes might be wrong.  Or at least, it might be right for
the boot ROM version that the manual was intended for (which Tek doesn't say, of course) and I have a different version number.

Haven't been able to locate a ROM dump on the web sadly.

[poot36]

@wn1fju I found this on the net: https://forum.tek.com/viewtopic.php?t=136381 It may help you in figuring out what is wrong with your unit.