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On Mon, Nov 18, 2024 at 01:19 AM, rafael suarez wrote:

Hello,

I’m truly grateful for your willingness to help and for all the suggestions
regarding the repair of my TDS. I don’t want to be intrusive or take
advantage of your kindness, but there’s something I can’t figure out.
It’s about the solid aluminum caps of 33 ?F 10V and 10 ?F 10V. There are
several series available, and I’m not sure which ones would be appropriate
for the scope.

Could you please suggest one? Thank you in advance. I hope this scope comes
back to life soon.

Best regards,
Rafael

When you say Tantalum, are you talking about the small metal can capacitors with the tiny black plastic base? They are standard SMD type aluminium electrolytic.
They should all be replaced with equivalent types in any TDS500/600/700 series scope. IIRC only the C and D models had the electrolytic capacitors removed from the design.

I usually measure the size, then select a part that has low ESR and high ripple current rating, and also I try to go up a voltage rating or two if I can.
(For example, there is a cap on the front panel that is actually underrated from factory, but that's not as good as the one cap on the -ve voltage rail on the Option 05 TV Trigger board that is mounted backwards to the (incorrect) marking on the PCB!)


Jared

If you swap the cables coming from the readout to the vertical and horizontal boards, what does that show?

Thanks,
Barry

OP save time, avoid many more text notes
PLEASE take clear pix the 7704A problem, go to this group Photos section, start new album, name like like "7704ARO"

Upload the pix to FULLY AND CLEARLY describe the exact issue,

Then post the link to the photos in a message.

Amicalement

J

top is now at center, bottom is below the bottom of the screen but still there. when I use the beam finder button I can see that all is displaying well, and readout value changes when i change volts per division, it"s just in the wrong location

By this, do you mean what should be at the top is now at the center and, possibly, what should be at the bottom is not there at all?

Thanks,
Barry - N4BUQ

Thank you. I'm new to groups.io so I'll look at getting some pictures posted of the unit.

I'll give it a go reseating what I can on the readout board, hopefully it helps!

Both traces will display fine at the moment, just the readout issue

Correct yea, it appears its all there! just in the wrong position shifted down!

Rafael,

The solid Al condensers can be replaced with tantalum, surface mount or radial. Go to 16V if you use tantalum as a precaution. Tantalums will have very low ESR. If these are decoupling, the same or higher capacitance values can be used.

Mark

P.D. There’s something I forgot to mention, perhaps I didn’t make it clear earlier. I’m located in Lima, Peru.
Greetings from this part of the world.
Rafael

Hello,

I’m truly grateful for your willingness to help and for all the suggestions regarding the repair of my TDS. I don’t want to be intrusive or take advantage of your kindness, but there’s something I can’t figure out. It’s about the solid aluminum caps of 33 ?F 10V and 10 ?F 10V. There are several series available, and I’m not sure which ones would be appropriate for the scope.

Could you please suggest one? Thank you in advance. I hope this scope comes back to life soon.

Best regards,
Rafael

This would be a good choice for C17 from Digikey:
It has high ripple current capacity and very low ESR and ESL for its capacitance and voltage rating.
Lifetime is stated at 4000 hours, but that is at 105 degrees C. At a more realistic ballpark of 40-ish degrees C, you'd be looking at around maybe 200,000 hours according to the datasheet...

A moment please...is it a stable or intermittent, moving vertical position?

1/ A photo is worth 1M words , post images to photos, create an album

2/ Tek 7000 circa 1970s..1980s boards are interconnected with ribbon cables and harmonica plastic IDC connectors subject to corrosion or deteriorating plastic. Please check all connectors on the readout system

3/ on boards, the ICs and BJT are on Berg Griplet PCB inserts or TI IC sockets that also fail.
Suggest inspecting and wiggling every transistor on the readout and other related PCB

Just my experience since 1970s.(7104, 7904, 7703)
Bon chance,
Have an absolutely fantastic day

Jon

Rafel,

Mouser has the 47mfd in stock in two versions, 647-UCY2C470MPD (12,000 hour 160V) and 647-UHE2A470MPD (7000 hour). Digikey has a 56mfd UHE UHE2A560MPD (7000 hour). The UHEs are 100V. I do not know if the capacitance value is critical not seeing the power supply schematic. Even though the original checks alright, being the age it is, replacing would be best. For filtering of the B+ supplies, a higher capacitance can be used. Going up in voltage can be done.

Mark

Good evening,

I disassembled the PSU again and checked capacitor C17, which has an ESR of 0.5 ohms—I think it’s fine. Then I tested transistor Q9, and it doesn’t show any unusual readings. Diodes VR4 and VR5 measure open in both directions, so everything seems to be fine there.

On the other hand, I rechecked the caps on the CPU board and the acquisition board and found some caps that don’t give any ESR value and others that measure out of the desired range. I tested them with my B&K 881.

I’ve made a decision to place an order with Digikey for the components in question and the solid caps. I’ll replace all the solid caps first.

Thank you very much for your advice; I’m truly grateful. I’ll update you on my progress as soon as I receive and replace the solid caps.

By the way, what would be a suitable replacement for C17? I haven’t been able to find anything similar on Digikey.

Thanks again, and good night.

Is the trace also compressed? If so, look at the vertical board. The output IC could be bad or dirty contacts in the socket.

Mark

There was an extended discussion including /g/TekScopes/message/132588
that might add usefully to the responses you've received here.

Best,
George.

I opened the TDS380 up yesterday and didn't find anything obvious with a visual inspection. I powered it up to start checking voltages on the LVPS and it booted normally . . . all voltages were in spec. I disconnected and reconnected all the power connectors to make sure nothing was loose, but i'm at a loss now. Could still be a capacitor starting to degrade but for now, it's back together and running fine. If it happens again, I'll pull the PS and test all the caps, transistors, diodes and anything else I can think of.

Just to clarify, the text is readable and is normal height, they're just at/near the center. Is that correct?

Maybe for extra clarity: “They’re *both* at/near center?

Raymond

Just to clarify, the text is readable and is normal height, they're just at/near the center. Is that correct?

Thanks,
Barry - N4BUQ