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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

CLA pot?
check if defective and replace pot?

J

Hi, I own a TDS694C which has a similar power supply. Worked fine but after
sitting on the shelf for a long time died on the first power up.It produced
modulated high pitch sound on standby power, and died completely on
attempt to turn main power on by the front button.

The first thing I found was a dried and blown 1000uf EC in the power
supply, s main line, C124 in TDS520B schematics. After replacement nothing
good - no standby power. Measured conductivity of integrated PWM (U12)
output transistor - open in both source-drain directions, not good. It was
TOP200YAI Replaced with a newer and more powerful TOP204YAI. Still nothing,
no input voltage on standby PWM. High voltage Zeners were ok (tested with
curve tracer, you can also do that with auto transformer and rectifier on a
breadboard, but be careful with high voltage!).
Walking along the supply line I have found a non-conducting current
limiting 1W resistor, R176. It was 2.4Ohm in my PS and *fused* 27Ohm in
TDS520B. It just cracked when the integrated PWM was blown by the voltage
spikes. Very thin crack, visible under microscope only. So it is fused in
TDS520 for a reason. Replaced with a new one and the problem was solved - I
immediately got standby power and good main power after.

Best,
-Andrei

Hey everyone, I’ve got a Tek 7704a where the readout that SHOULD be at the top and bottom is offset and near the center.

Adjusting the vertical separation pot didn’t fix it, it won’t adjust enough

Any tips?

FS: Tektronix Type 1101 accessory power supply
LEMO connectors (4) on front panel.
+15VDC -15VDC +5VDC
TESTED, Works as it should.
Serial # B042132
$150 by PayPal or Zelle
Ships from Dallas, USA
Free shipping for US 48 states, other please ask for quote.
PM me off list with inquiries.

Ron

Those work well and I've used them in a couple of Tek scope power supplies. The thing I don't much like about them, at least for this application, is once you solder them in place, then if you ever had to replace the cap, it's necessary to remove the adapter which is more risk of heat damage to the circuit board. If, though, you have really nice desoldering tools then that might not be as much of a concern.

Thanks,
Barry - N4BUQ

Strange, I emailed a reply and it never showed up.

On Ebay, search for Tektronix capacitor adapter. Somebody is selling a set for the 465 for $10 or best offer. I don't know the seller but they've sold a couple hundred.

Hi George,
I just bought a Tek 2232 with GPIB option. I see that you intentionally installed this option on your 2232 a couple years ago. Maybe for transferring data to a computer? It seems the original plot options require vintage plotters. Do you know of any modern scheme to emulate such a device and generate a bitmap or jpg file of the CRT display? Or should I rig up a cellphone holder in front of the CRT for this?
Cheers
Halden

On Fri, Nov 15, 2024 at 1:04?PM rafael suarez via groups.io <rafik69pe=
[email protected]> wrote:

I’m afraid I don’t have a curve tracer. Perhaps there’s another way to
test them?

The TVSes should measure open in both directions, until you reach somewhere
beyond their threshold voltage. This is 220/250V respectively, which is why
they're challenging to test. If you can somehow provide a current limited
(1mA will do) ~300V DC, you can simply measure the voltage drop across them
in both directions. It should be roughly 250/220V respectively.
If you can't, perhaps best to leave them alone.
If they've failed open, your switching transistor will fail, though it may
take it a while. If it comes to that you'll want to change both TVSen and
the transistor. I seem to remember replacing a BU508, which is easy enough
to source.

On another note, I’ve found a few solid SMD capacitors in bad condition on
the large board visible as soon as you open the scope.

That would be the CPU board. Also look at the acquisition board, the front
panel board and whichever other boards you have in the scope. If the
electrolytic caps are the same make and vintage, the odds are that they've
failed or are going to fail.
There are many threads in this forum about how to clean boards that have
suffered electrolyte leakage. The problem is that traces may have rotted
away, and if they haven't yet, they may still rot away if the electrolyte
isn't cleaned and/or neutralized.
I believe in North America the recommendation used to be to wash thoroughly
with; Simple Green, distilled water, IPA and then leave the boards to dry,
or "bake" them at a very low temperature. Getting under components where
electrolyte may have pooled can be difficult.
There are many stories of people who managed to find and repair broken
traces and probably as many, of people who gave up. My TDS684B(? I forget)
has never yet worked, even though I cleaned it and changed the
electrolytics :/.

Good luck,
these are very capable scopes and well worth putting some time into.