Tektronix TDS754D Repair - Acquisition Board Self-Test Failure & Funky Channel 2

[james_s]

Well I fixed mine, I did not find it especially difficult, but I paid my dues years ago by making mistakes and ruining stuff I was trying to fix and now I'm quite adept at hand soldering large ICs. I'm certainly not the only one who can do that.

[Snekers]

Well... I did it! Passes all self tests and channel 2 is perfect now. Thanks for the help, everyone!

[Johnny10]

You didn't explain how?

[Snekers]

As was talked about above, there were some broken solder joints on U400 that were not making proper contact, so I reflowed them. Not sure if it’s a common location, but here is where the damaged solder joints were.

[james_s]

Nice job. That's exactly what was wrong with mine too. I don't know which specific pins it was because I reflowed them all. Does SPC pass when you run that? I had to replace the attenuator relays in mine, that was a tedious job. It's been a rock solid instrument since then though. A bit bulky by modern standards but a joy to use.

Now you need to put together a GPIB interface so you can clear the error log, there's a thread on this forum that covers building one, all you need is an arduino nano or similar board and the appropriate connector.

[Johnny10]

I repaired a 784D a couple of years back and sold it but I have the parts to make another one.
Following this thread made me get it out and look through the parts again.

Glad we could help.

I bought a Tek 2465A that was sent in a box the same as yours.
After some cosmetic help all is well with it but I always worry there will be underlying problems later with so many shocks to the unit.

Good luck with yours, Good job!

[Snekers]

Yep, SPC and all other tests pass. I might be on the lookout for a later model of acquisition board so I can upgrade it to a 784D by removing a few components, but they pretty much never go on sale by themselves. One final thing I need are a replacement for the Dallas chips.

[james_s]

Aren't all of the boards upgradeable by changing some soldered jumpers? You need to have the scope calibrated after doing that though which IIRC costs a few hundred bucks.

I built replacement Dallas chips for mine using board files somebody posted on this forum, they've been working perfectly so far. You have to use low profile IC sockets and low profile pins to clear the video trigger board which I think I saw that your scope has so keep that in mind when doing that.

[charlyd]

Those ACQ baords are not interchangable from later models. you can see it at the fw number.  6.x cannot be upgraded to 7.x (newer version) and the hardware is also not interchangble

[james_s]

Those ACQ baords are not interchangable from later models. you can see it at the fw number.  6.x cannot be upgraded to 7.x (newer version) and the hardware is also not interchangble

So you can't upgrade the bandwidth? Mine is a TDS784C so it's an older version than the one in this thread and it's already the top of the line model so there was nothing to upgrade. I remember reading that the TDS754C could be upgraded to the 784C though by changing some jumpers and recalibrating.

Not that it really matters too much for most things though, to really go above 500MHz usually requires a probe costing more than the scope.