Tektronix TDS540 Repair - New VCO board!

Your First Order Free at PCBWay: www.pcbway.com/setinvite.aspx...
In this video I build a replacement Voltage Controlled Oscillator board to replace the corroded one from leaky capacitors to get my TDS540 oscilloscope working again.
UPDATE: The Infinion BB535 (BB535E7904HTSA1) looks like a close match for the obsolete MMBV105 diode.
You should be able to mount it across the top left and right CR101 pads.
(I haven't tried it but let me know how you go if you do!)
Link to project:
www.pcbway.com/project/sharep...
Link to gerber file etc:
drive.google.com/drive/folder...
Link to TDS540 page on Tekwiki:
w140.com/tekwiki/wiki/TDS540

[@visitslovenija]

Terrific. Thanks for sharing. Have ordered some boards. And, yes Farnell do stock the MMBV105G, but (here in Ireland at least) have a minimum order quantity of 3000. ;)

[@NearFarMedia]

Cool, let us know how you go with your board! And yeah, I doubt I'd use a fraction of that 3000 in my lifetime... haha.

[@swp466]

Always love when a new NFM video pops up! I routinely wash PCBs in an ultrasonic cleaner. Quite a bit faster than the dishwasher, but if you want to save some dry time, here's what I do after the wash -- give the board a dip in 99% IPA for a minute (this drives out any remaining water from even the smallest nook and cranny), then pop it into an oven at 250*F (120*C) for an hour. Works a charm.

[@NearFarMedia]

Yeah, the IPA is a good idea. I usually do so with smaller PCB's, but I need to get a bigger tray for these TDS scope PCB's, they are quite large..

[@swp466]

@@NearFarMedia I've done lager PCBs in either a cookie sheet or a large glass baking pan (don't tell my wife).

[@Rhine_Labs]

Great Job. I parted out and scrapped 2 of them a while back one had a plaque for an design engineer / patent holder no one wanted it or the cover it not even the tek Museum.

[@fliptrontube]

an eBay search shows multiple sellers with new old stock of the CR101 part

[@tedmoss]

I've been working on these for a while, interesting scopes.410, 640, 754.

[@nrcha]

Can you elaborate on the dishwasher part? Just regular cycle with, preferably, no dishes and no detergent? Sounds scary. Can I just clean it with lots of IPA instead?

[@DarianCabot]

Nice! The 90˚ trace routing always looks weird to me, but nice to see you copied that in your replica 👍 Also, Farnell shows stock for that MMBV105G (however Element14 doesn't?) Also a comment on Mouser and shipping batteries - Here in oz many couriers flat-out refuse to ship any batteries. I've had the phone calls with them trying to explain that Alkaline AAs are not dangerous, etc, etc... In the end we had to ship our product without batteries. So I can see why Mouser has this rule. Probably many shipments bounced at customs or international couriers. It sucks for everyone.

[@NearFarMedia]

Yeah, I thought of using 45˚ corners, but figured I'd keep it true to the original. It's always a pain shipping batteries, especially when the couriers default to 'no', even for battery chemistry that has been shipped just fine for decades before lithium came around...

[@stevent3450]

can you tell us what type of soap if any or type of water and temp the dishwasher had? I had never thought of this idea for boards with SMD cap leakage but sounds great ! :) and if your ever in Madison wi USA let me know and lets go for pizza

[@NearFarMedia]

I just used the usual 'Finish' brand dishwasher powder, any normal dishwasher soap will work fine.

[@mirkobruhn9841]

Would 70 degree Celsius be too much?

[@NearFarMedia]

Nope, it's fine. Even electrolytic caps are rated to 85 degrees C at the lower rating. And the components withstand much higher temperatures during assembly too.

[@jk-em9wk]

Try NXP BBY40

[@NearFarMedia]

Thanks! I'll check it out. :)

[@Runco990]

"But if we released schematics, we couldn't strong-arm you into buying our latest $20,000 scope!" Said every corp ever. I have stayed away from these series scopes. The caps, and it's questionable how good they are compared to a modern scope. I did work on a few and just the massive power consumption is a no-go for me. Not a value proposition any more unless you find one for 1/4 of ebay prices. Then, maybe.

[@NearFarMedia]

I have a rule not to pay more than 10,000 yen (approx US$80) for a TDS500/600/700 series scope. Means I get to have fun fixing them as they are usually faulty in this price bracket, and I don't spend too much adding to my collection. Also, it seems I am still able to get them at this price, so I fix them and sell them for a small bit of extra pocket money (well, I plan to sell them, one day.... hahaha). My daily TDS scope (besides my good ol' TDS220) is a TDS784D with HDD option and some software, so the features and performance are worth it. I also have a TDS794D too for when I need a little more bandwidth.

[@Runco990]

@@NearFarMedia Yes, well.... if I could get one for THAT price that isn't complete scrap, crushed, missing parts, I'd put in the effort as well. 👍

[@aurthorthing7403]

You should rename you channel to Tektronix fanboy or something like that.....

[@NearFarMedia]

Yeah, I seem to have too much Tek gear... 😅 I do have an Agilent bit of gear coming up though. 🙂