开云体育

On Sun, Apr 6, 2025 at 10:31 AM, Steve Hendrix wrote:

Some meters give you only the ripple when on AC, but some also include the DC
measurement (true RMS includes DC).

Hmmm, I didn't know this was ever a possibility. Can you give some examples of DVMs that have this "feature", where there's no blocking capacitor on the AC input?

This makes me wonder which reading, AC, DC, or both, would be the True RMS reading on a TRMS meter. I only have one TRMS meter and that's a Fluke 27/FM I bought from Walter at Sphere. I've probably never tried to use it to measure ripple; my default is my non-TRMS Fluke 23. I'll have to try the 27/FM next time.

--
Jim Adney
Madison, WI USA

Hello guys!

Does anyone know of any 205 carts anywhere? I would really love one for my 556.

Best regards,
Alex

Tnx Holger for your tips!
I will look into those directions (I was examining the schematic diagram of the horizontal readout amplifier…).
It seems that you watched at my YouTube channel or at my website, where I started describing the troubleshooting of my 7854…
As soon as I will test what you suggested me, I will be back with my updates.
Alberto

Thanks to all. This is currently being investigated.

David

Hello,

You can use SHIPITO ( )

They will provide to you an US adress for Ebay and they can ship to you in UK with UPS or FEDEX

Best regards
Eric

On Sat, Apr 5, 2025 at 8:21?AM Jay Czaja via groups.io <jmczaja=
[email protected]> wrote:

This scope has me scratching my head. I had it running all night without
any problem, I doubt part number 160-2393-00 is actually the culprit
despite the occasional startup error. I suppose I should scrutinize the PSU
more.

Yeah, until you've eliminated PSU problems, there's no point in
troubleshooting anything else.

I have a question. What is the best way to measure ripple on the LV supply.

When I checked it the first time, I had the 2247A on an isolation
transformer with my 2245A connected directly to mains AC. I used a x1 probe
on my 2245A to check for ripple and clipped the ground lead of the probe to
the chassis of the 2247A.

I don't know that an isolation transformer helps, but maybe you want the
two scopes plugged into the same outlet. It can't hurt to connect the
ground clip close to the power rail. Tek always specifies PSU ripple at
20MHz bandwidth, so you want the 20MHz bandwidth limiter on. I don't think
most 1X probes have 20MHz bandwidth, so you might want to just use flying
leads or a coax with clip leads to hook up.
Note that you can measure your noise pickup by turning the instrument under
test off with your leads hooked up.

For the components (sidestepping political comments), it's the same reason why people buy pre-packaged meals.? It's more convenient for one.? The other is that you know what you're getting, and the cost is acceptable, saves you a lot of preparation, and it devolves to a "just do it".

It does save all the diagnostic steps, and it does start the instrument from a known state.? You can argue both ways.

Harvey

On 2025-04-06 11:25 AM, Jim Adney wrote:

It may not be the BEST way, but the quick and simple way is to use the same handheld DVM that you use to measure the DC voltage.

Be a little cautious with this. Some meters give you only the ripple when on AC, but some also include the DC measurement (true RMS includes DC). So if the reading doesn't change much when you switch from DC to AC, it's not telling you what you want to know. You could of course connect thru a capacitor; it takes only a little calculation to determine an appropriate cutoff frequency based on the meter's input impedance and the capacitor value.

Steve Hendrix

On Sat, Apr 5, 2025 at 07:21 AM, Jay Czaja wrote:

What is the best way to measure ripple on the LV supply.

It may not be the BEST way, but the quick and simple way is to use the same handheld DVM that you use to measure the DC voltage. Just switch your DVM from DC to AC and you will get a very good idea of the ripple. In most cases, you're not looking for the difference between 2 mV and 5 mV; you're looking for the difference between 2 mv and 2 V.

This is probably not useful for most switching supplies, since most DVMs don't go much above a few kHz on AC, but it has the advantage that you're already connected to the test points you're interested in, you automatically get a floating measurement, and it tells you whether you need to look into this more carefully or not.

--
Jim Adney
Madison, WI USA

There's an item on US eBay that I can't purchase because the vendor blocks
non-US buyers.



Is there someone who's willing to purchase it for me ($200), and ship to
the UK using a reputable courier (UPS/Fedex/???)



If yes, please contact me off list... The item should fit in a package
about 8" x 6" x 4" and weigh about 1lb. or less.



I'd like to keep shipping cost down, so if you have a contract with a
shipper that would be even better.



If the option to pay UK tax and duty at shipping end is available that might
be good (depending on costs).



Please contact me off list to arrange mailto:david.partridge@...




Cheers, David

Typo - sorry about this
Should be:

Where would you want a thick film, or a Ceramic, or a carbon film resistor?

Jon,

Thanks for the recommendation! I found it and looking at it now.

Barry

Roy,

I'm not going to blow my own horn here, as I do this primarily as a service to fellow Tek owners.
There are hundreds of members here who have bought my kits, who can speak for me if they wish.

Sure you can spend hours of your own time, poring through pages of Digikey and Mouser parts, and make up your own selection.
That's your privilege, and nobody can take that from you.
But do you really know your scope's circuits and functions so intimately, that you can easily select which components out of a vast pool of available components is really the most suitable, most reliable or longest-lasting one?
Where would you install a super-low ESR capacitor, and where would you install a Low-Dissipation capacitor in the scope?
Where would you want a thick film, or a Ceramic, or a carbon film capacitor?
Do you really want to open up your scope time and again, because your choice of component may not have been the optimal one, even though all on paper, all the numbers matched up?
Do you want a fully-working scope in the minimum possible time, at a fair and reasonably low price, or do you want to troubleshoot part-by-part, hour after hour?

The time which I spend evaluating the photos of the Scope's PCB's including close-up inspection to determine whether additional components are defective, and answering the customers' questions during installation, is certainly not reimbursed in the kit price.

My experienced eye can identify problem components which the owner doesn't even know about.

Some of the components in my kit are not available from Mouser or Digikey, and I source them directly from Vishay's warehouse in Israel, not because it's convenient, but because it's the most optimal part for that circuit.

The bottom line is that it boils down to trust.
My customers trust me that I will deliver the optimal products for a fair price, about which they need have no concerns as to whether the product will provide a successful overhaul, and reliability for decades ahead.

Let me put it this way - if I was in the market for a used scope, and I had to choose between an unknown overhauled scope for which the owner used my kit, versus one which the owner sourced his own parts, there is no doubt that I would want the one which has my components installed. Not because my parts are optimal or better, but because I have no idea what the knowledge level of the other owner is, and what criteria he used to make his selection of components.

This statement is not intended at all to denigrate the abilities of the highly knowledgeable and competent techs on this and other forums, who likely have much more knowledge and experience than me, but only to suggest that it's a good idea to assimilate the experience of "those who have come before you", and not to focus on saving a few pennies here or there.

In 2009, I overhauled my own 2465B with exactly the same components in my kit. It now 16 years later. The scope is on 10-12 hours a day, 6 days a week. That's an easy 50,000 hours. I have had 3 failures in that time, all unrelated to the circuits in which my kit components were installed. They were: the A2 ON-Off switch burnt out - replaced; a diode on the A3 shorted after a power failure - replaced; and the A5 failed (corrosion), with a whole bunch of the SMD ladder resistors and a couple of semiconductors needing replacement - thanks to Siggy for his diagnostic help with that. I expect trouble-free performance for at least another 50,000 hours.

Menahem

For convenience:

/g/TekScopes/photosearch?p=created%2C%2C%2C50%2C1%2C0%2C0&q=tek%20user%20comments

Raymond

Hello Trevor,
Sorry for the late reply.
I would first start with allignment of the 3kHz, 30kHz and 300kHz filters in the VR Module explained in the Service Manual. The trim capacitors get bad contact over time. I've written earlier on this issue. Left click on my name above this message and search for 2712. You will find more info there.
Good luck.
I will be glad helping you futher for as far as I can.
Jaap PA0JRK

I just deleted a message on this thread. If any more divisive messages appear, they will be deleted and the thread will be locked.

David

On Sat, Apr 5, 2025 at 01:33 PM, Jim Ford wrote:

Nope, David, at the risk of getting political
:

IMO... I'm not sure... at this time... expressing political opinions... in the forum... is a good thing.... I mean good for the forum.
I'd like to here more about why people use 'capacitor kits' ... to fix 24XX series scopes, rather than sourcing the parts themselves.
I don't usually replace a component, unless I know it's bad.



--
Roy Thistle

I had always heard that Sony was exceptionally nasty about keeping people from rebuilding their jugs. Either this was not true or there were cracks in the system that allowed some to slip through.

Brenda

Ask ETF, the Early TV Foundation.

The the Trinitron gun was probably old stock horded by someone like me...

Ha!

Frank DuVal

You may have no choice...is you iphone or android containg china components?