EEVblog #536 - HP35670A DSA Repair

Dave repairs a HP 35670A Dynamic Signal Analyser. Well, kinda...

EEVblog Main Web Site:
EEVblog Amazon Store:
Donations:
Projects:
Electronics Info Wiki:

[AspectOfTheStorm]

I love these repair videos, it's really encouraging to see you analyze and troubleshoot electronics that 99.99% of people would just pitch. If your electronics don't work, it's not like 45 parts went out in it, it's probably 1 or 2 that failed. If you can hunt them down, you have a good chance of repairing it.

[HZL_AD]

Hi EEVBlog, I was the one, person in charge on the DSA PCB repairing and calibration.You can ask me
on the hardware thing.

[davecc]

Before you cleaned it up I thought that the goo might have capacitively loaded down the oscillator circuit...

These repairs that end "not fully functional" are great! This is how many of us end up! And its great to see your process and choices you make.

The end result is really secondary...

[PicaDelphon]

Well that Goop use to be a Gray Rubber Foot that Melted..

[OverKillPlusOne]

That Greg too is what's left of that foot after something like WD40 or some other solvent attacked it! Not heat! I have seen it happen before.

[fluffyvillain]

I love how you include debugging steps even if they didn't work.. super helpful.

[EEVblog]

Yes, it's an inductor, but is in parallel with the xtal only.

[mashed]

Dave-- Should see what the same -18V rail connects to physically, because that likely went out of range high and damaged the -12V regulator. Maybe it took out some dual-supply opamps, as your problem seems now analog in nature. Love these repair videos btw :)

[nicksokolov]

I own one of those - fully loaded with options 4Ch - sweep is great for diagnostic. Basic is more like HP version of Pascal. East to repair, I am getting an external microphone module. Those units fully optioned are like swiss pocket knife - your unit is more like a cheap version of an oscilloscope. To option it up - some is software but you will need a chip burner. Loads of statistical and system goodies but only if it is optioned up. Keep up the good work

[WorldwideSocialGamer]

When I was in the Navy I got my hands on a 35Ghz Spectrum Analyzer. I had no idea what the test equipment cost at the time. But I kicked the shit out of it dragging it all over the ship.

[ThisDoesNotCompute]

That goo on the top board looks to me like it's a melted bumper, like the other two nearby. Similar color and placement.

[shamanjoe]

I really liked this video. If you do more troubleshooting on the unit, I hope you make more videos. It's super interesting to me tracking down faults and problems like this. Keep up the good work Dave!

[EEVblog]

Nothing changed. Because this thing is so big I had to troubleshoot on my teardown bench instead of my main bench, hence the different camera angle.

[tubical]

pvc, rubber and things like that can do "funny" things over time, while repairing old reel2reel machines some of its rubber belts been melting away, some becomes sticky glue and others turn into hard plastic. it all depends in the chemical looks of the used material.

[BalticLab]

Yep, it's making up for stray capacitance in parallel with the xtal and it also affects the pullability of the xtal through the trim cap.

[peterpv]

Most of the time they're not chips but resistor arrays (like 16 resistors to supply) these are used to load the open collector outputs of the other ICs.

[Dishmopo]

Wow! A Trident Video Card! I haven't seen one of those since I had a 486.

[bfriesen]

Great video. I hope you take the time to continue repairing it.

[skonkfactory]

I'd bet that the reason the ADC gate array is failing is that the i2c bus isn't coming up. this often happens if an RTC clock's battery has died- i2c is open collector signalled, so a chip that expects to have a battery on it will tend to load the lines through its input protection diodes, crowbarring the bus.

[mikeselectricstuff]

I've seen those grey PVC feet go melty - it isn't due to heat - it's a chemical thing, takes many years & makes a really sticky mess - probably something to do with plasticisers.