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TDS540 vs TDS540A

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Beb's Repair Bench
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Joined: December 15th, 2018, 7:14 am
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TDS540 vs TDS540A

Post by Beb's Repair Bench » December 15th, 2018, 7:26 am

I'm looking at possibly getting a TDS540 but when I tried to research it - everything seemed to be about the TDS540A. What's the difference between the two? Is the original 540 even a good scope? I have a 465B and I love it but am looking to upgrade to something with four channels, not to mention the 500MHz bandwidth is an added bonus.

strick
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Country: United States

Re: TDS540 vs TDS540A

Post by strick » December 15th, 2018, 11:52 am

Bob,
The original 540 did not have a floppy drive and VGA output (as I recall). The case doesn't even have a hole for the floppy. Otherwise, basically the same, but don't expect it to have expanded memory capability (1M). As I recall, most already had FFT turned on. Also, pushing shift - status (help) did not have the banner option with any of the scopes I had.

I've fixed and passed on several of both 540 and 540A (and 520a). The older straight 540s tended to have the worst surface mount capacitor (SMC) problems and in several cases, I simply gave up after fixing more than a dozen traces and still had problems.

At this point (2018), I won't even look at a 540 anymore. I'm still fixing 540As as many have few, if any SMC, problems. If you get a chance to actually see the scope prior to buying, you can tell if the SMCs have been leaking by simply examining the surface mount solder joints. If they are shiny, no leakage - if dull, then there has been leakage. If fresh, you'll still be able to see the leaked electrolyte on the board...

Strick

Beb's Repair Bench
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Joined: December 15th, 2018, 7:14 am
Country: United States

Re: TDS540 vs TDS540A

Post by Beb's Repair Bench » December 16th, 2018, 2:50 pm

Ah, well the first part is reassuring, the second part about the SMCs, not so much. I didn't manage to get the 540, but did score a 640, again a straight 640 model. Unfortunately it's sight unseen and purchased as "unable to test", so I'm expecting a broken scope, but at under $100 I feel like it's worth a gamble, and at least now I'll have an idea what to check for on my initial inspection.

Not having a floppy drive bothers me not at all, a VGA output would have been cool for external displays but definitely isn't something I'd cry over not having.

Thanks for the advice, it's definitely helped.

strick
Posts: 95
Joined: March 22nd, 2016, 11:23 am
Country: United States

Re: TDS540 vs TDS540A

Post by strick » December 16th, 2018, 3:50 pm

Bob,
good luck!

Strick

Estergon
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Joined: December 18th, 2018, 6:48 am
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Re: TDS540 vs TDS540A

Post by Estergon » December 18th, 2018, 6:53 am

Sort of was eyeing the same models myself and I'm glad I got the breakdown so easily browsing through here.

No VGA for presentations and external display is a bummer though.

Beb's Repair Bench
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Joined: December 15th, 2018, 7:14 am
Country: United States

Re: TDS540 vs TDS540A

Post by Beb's Repair Bench » December 23rd, 2018, 8:30 am

Estergon,

Yeah it would have been nice to have the VGA, but I just got the TDS 640 in the other day, and after breaking the cardinal rule and powering it up before inspecting the guts of it, I'm pretty happy.

I've got all the "usual" POST fails that point to bad caps and a bad NVRAM, but my plan is to re-cap the entire scope, hopefully I won't have any bad traces or vias (or at least bad ones that are easy to deal with!) And I'm debating on whether or not to replace the NVRAM or attempt a battery transplant.

But all in all I think this is going to be a fun project and I'll hopefully end up with a scope that is WAY more than I'll ever need.

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