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Search found 20 matches

by Gorgon
December 15th, 2011, 1:46 pm
Forum: Other or Discontinued Oscilloscopes
Topic: TDS 640 repair
Replies: 9
Views: 31788

Re: TDS 640 repair

Make sure you also change the caps on the front panel :-) , and also the Serial/Parallel board.

( The front panel caps cleared up that last bit of channel noise for me. )
by Gorgon
December 7th, 2011, 6:16 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS644A NVram / Serial Parallel
Replies: 11
Views: 36942

Re: TDS644A NVram / Serial Parallel

The first I knew of a problem was the scope not booting. No display and all leds on the front panel illuminated. The 7 seg display would flicker between a couple of numbers ( I think 8+9 , but could be something else ). After lot's of trial and error I eventual found that the scope would boot correc...
by Gorgon
December 6th, 2011, 2:02 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS644A NVram / Serial Parallel
Replies: 11
Views: 36942

Re: TDS644A NVram / Serial Parallel

The serial / parallel board is now also fixed. For those interested it appears as though capacitor leakage had caused eventual failure of U8 - a dual 2 to 4 line decoder (74F139) The IC was replaced - the board thoroughly cleaned - and functionality restored. For those of interest I started to draw ...
by Gorgon
November 17th, 2011, 6:16 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS644A NVRAM Via GPIB
Replies: 1
Views: 9260

TDS644A NVRAM Via GPIB

What would be the official Tek response if I were to release the method to read NVRAM over GPIB for the TDS5xx/TDS6xx scopes ? The reason for doing so would be to help others when their NVRAM eventually dies. I need to ask Tek - as the method would reveal information which they may have used in othe...
by Gorgon
November 15th, 2011, 10:45 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS644A NVram / Serial Parallel
Replies: 11
Views: 36942

Re: TDS644A NVram / Serial Parallel

Many thanks to a kind forum member - I have restored my nvram - although the calibration will be out - i can perform SPC and get useful waveforms :-) again. I'm still looking for the TDS600 field adjustment tool if possible. Alternatively if someone knows the memory locations where the calibration d...
by Gorgon
November 14th, 2011, 8:34 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS644A NVram / Serial Parallel
Replies: 11
Views: 36942

TDS644A NVram / Serial Parallel

Sad news - my lovely TDS644A has lost it's memory :-(. It appears as though the Serial / Parallel board has gone faulty and somehow caused corruption of the NVRAM. The scope will not boot at all with the Serial/Parallel card installed , and although without it - it does boot , but the NVRAM is obvio...
by Gorgon
April 13th, 2011, 7:04 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

The PSU doesn't appear to have any of the 'troublesome' ones either. The only slight concern I have ( and this *is* indicative of aged caps ) is that it only appears to be an issue if the scope has been on a while and THEN put into standby. From cold - if I turn on the scope - then wait 10 seconds -...
by Gorgon
April 12th, 2011, 4:52 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

So - why would the display cause 'ticking' when the machine is in standby ? The caps on my PSU look unharmed. I have no ticking when the TDS644A is out of standby. So I don't really see why it would be an excessive load issue ? Low Volts all appear fine when scope running. Sure - it's an easy thing ...
by Gorgon
April 6th, 2011, 12:48 am
Forum: Programming Support
Topic: Adding a GPS receiver to your counters
Replies: 10
Views: 37267

Re: Adding a GPS receiver to your counters

I'm also not sure it's a good selling point :-) Sure - if you only need one instrument with 'perfect' accuracy then it's probably fine - but then you're only buying one instrument. In a lab setup - you are much more likely want everyone using the same reference. Give a man a clock and he 'KNOWS' wha...
by Gorgon
April 6th, 2011, 12:45 am
Forum: Programming Support
Topic: Micropolis HD wont spin up
Replies: 4
Views: 18604

Re: Micropolis HD wont spin up

Read head failure can also cause this.
The firmware will try and start the drive - then try a read - if this fails - you'll often hear a few attempts at moving the head - then the drive will spin down.
by Gorgon
April 6th, 2011, 12:40 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

As far as the 'ticking' I think this may be normal when in standby. Reviewing the TDS520CM manual ( which as far as I can see the description of the circuit operation was written from a different schematic :-) ) the standby power is generated from a flyback circuit. It appears to DC rectify the inco...
by Gorgon
April 6th, 2011, 12:14 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

The scope is still well - there is only one outstanding issue I've noticed. If the scope has been on for a few minutes - and then is switched off using the on/stby button - there is a faint ticking from the power supply (1-2hz) There are no obvious visible problems with the (few) capacitors on the s...
by Gorgon
April 1st, 2011, 9:07 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

SPC worked fine. Scope good even after a few hours. Approximately 6mV p-p noise noted at full bandwidth looking at the cal/comp signal. ( in sample mode ) 2.8mV p-p at 20Mhz bandwidth ( sample mode ) 2.2mV with averaging of 4 i full bandwidth. (10:1 500Mhz 10M probe ) Noise now seems symmetrical (+v...
by Gorgon
April 1st, 2011, 4:06 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

Replaced the two caps - and the scope is *really* nice now - I almost can't tell the difference between 20/100/Full bandwidth options on the cal signal.

I'll let it run for an hour or so and run SPC and see if all remains well.

Thanks for a great forum - it has really helped.
by Gorgon
April 1st, 2011, 3:49 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

Turns out that the A10 Acquisition board did have a couple of rogue under rated caps. c1693/c1603 were both 33uf 10V - but had 15v across them. I'll replace these :-) with a correctly rated part. I didn't find any others - but I only checked the 10v caps ( And yes - they were definitely installed as...
by Gorgon
April 1st, 2011, 3:15 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS460 Alarm Tone
Replies: 4
Views: 116358

Re: TDS460 Alarm Tone

Replace caps on front panel - clean up any residue - watch out for C22/C23 being under specced in voltage ( based on my investigation of a TDS644A )

I had the beeper issue - gone now.
by Gorgon
April 1st, 2011, 3:13 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

Cleaned up / replaced al caps on Front Panel - and used 47uF/25v for C22/C23. Every other cap was replaced with 33uF 10V 105C. Ripple on test signal gone. Also - I started to get a continuous beep from the beeper - this has now gone. ( Touched up / cleaned all joints around the beeper section ). Mor...
by Gorgon
April 1st, 2011, 2:02 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

I've started looking at the front panel for leaky caps. I've noticed something rather disturbing ..... On the TDS520CM component manual - C22/C23 appear to be across the +/- 15V supply. The capacitors are marked 33uF on the schematic ( no voltage specified ) - yet on my front panel they are clearly ...
by Gorgon
March 31st, 2011, 12:25 pm
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

A little update. I did some more touching up of 'dull' resistor / capacitor joints ( a little fluxpen followed by re-heating ). The AC calibration error appears to be banished - even on starting from cold. ( My offsets are around 10-120uV across all channels - I assume from what I've read that this ...
by Gorgon
March 31st, 2011, 6:11 am
Forum: Other or Discontinued Oscilloscopes
Topic: TDS540 fault code
Replies: 24
Views: 227460

Re: TDS540 fault code

Tech8 - thanks for your information - it has helped move my TDS644A repair along. I obtained aTDS644A from EBay - the usual problems of leaky capacitors - and reports of acquisition failure. ( Acq fail / Atten fail / Cal fail ) Quick Summary I replaced all caps on Acq and Processor boards. And clean...

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