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On Sat, Apr 5, 2025 at 05:21 AM, Jay Czaja wrote:

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.

No need to use an isolation transformer to float the scope for this measurement. The chassis of the scope is grounded normally, not like old CRT TVs or monitors that mostly had a "hot" chassis.
Just use your other scope, set it to AC coupling and go as low in attenuation to get a readable signal across the power rail being tested. Connect the probe to ground and the tip to the power rail and see how much noise level you measure. You might also want to switch in the 20MHz bandwidth limiter so as to possibly get a more cleaner and relevant display. Ideally use a X10 probe, but X1 should be ok.

On Fri, Apr 4, 2025 at 03:23 PM, Jay Czaja wrote:

I found also this part number 160-2393-00 on the following 2245A "TekWiki"page
and there appears to be a ROM image. Is this something that would be abled to
be downloaded and programed?

You could download that BIN file and program it into a new prom chip. Perhaps the existing one is flaky, hence the come and go error?

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.

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.

Would it be more accurate to connect the probe ground to the ground on the LV test header (J1204) instead of the chassis?

Hi Alberto!

Your scope powers up correctly. The SRQ light stays on because a power cycle was detected. This can be cleared via GPIB or the Keyboard (see manual).
You can ignore this.

As far as I can see there a two errors:

1: ? think the trouble with the jumping/collapsing display is an analog problem - most likely a very simple fault like a dirty/defective potentiometer.

2: The keyboard section is not that complicated. It's descripbed in the "Theory of Operation" section of the service manual.
You should be able to diagnose it without the signature analyzer. Check the wiring to the front panel first.

Holger

Tnx Holger (and others)!

I will study more deeply the service documentation, because I didn’t note an easier troubleshooting approach to the digital section. I am just equipped with the signature analyzer, but I understood that it was not the only tool…

If you are curious about the issue that I need to fix, you can visit my Webpage that I’m dedicating to my 7854:

Alberto

The simple solution is just boycott the USA.

Dear Barry

Suggest you read the excellent Tektronix Circuit Concept book on oscilloscope CRTs, and learn about the development and characteristics of mesh dome CRT.

Then follow the service manual on calibration for the CRT, and HV circuits

Jon

I have a bit more info. I started the scope up again and I got the initial interrupt error that I posted in the beginning of this thread.

When I shut it off and started it back up, I was able to read the error message on the screen. It read "PART NUMBER 160-3493-00"

I was able to find this in the service manual and it appears to be a microcontroller. "MICROCKT, DGTL:8 BIT MICROCOMPUTER, MASKED FOR READOUT SYSTEM"

Is this a part I would need to find a donor scope to scavenge from?

I found also this part number 160-2393-00 on the following 2245A "TekWiki"page and there appears to be a ROM image. Is this something that would be abled to be downloaded and programed?

Jean-Paul and Raymond,

Is there anything that can be done to improve this behavior? I was thinking that reducing the sensitivity of the intensity adjustment might help.

Thoughts?

Barry

Hello,
For all those of you new to customs - in Europe we had it for 20 years.

Small video is at <> which should answer some questions.

Tam

--
With best regards
Tam HANNA (emailing on a keyboardless handset....again)

Enjoy electronics? Join 21k4 other followers by visiting the Crazy Electronics Lab at

Noise may be HV corona

j

Dear Menecham:

Very timely note, suggest to repost on Tekscopes2 and BUY/SELL forums. Perhaps also EEVblog?

We have seen congress in US proposing removing the deminimus exemption. The entire customs/tarrifs is in flux.

Chel the CBP/USPS/Fed Ex for latest info.

Our personal and corporate inports/shipping expericance

1/ The declaration of CoE, Harm # and exact descr is critial to get fast and correct clearance.

2/ Imports of USA CoE are NOT tarriffed by USA regardlss fo the export country,

3/ The reciever in USA may have a tax/tarriff levied by the shipper/US CBP, wheri must be paid before seivery.

4/ The amount is ENTIRELY at the descretion of the government office/worker that clear the shipment, and varies randomly......

High value shipments arealways examined , small packages and lw value MAY be taxed.

Best plan: Fill exact customs decalr with carefully choosen HARM number and country of origin with descr matche HARM # exactly.

Just my experince since 1970s of internation shipping


SHALOM!

Jon

Alright, so I'm not in the clear with this 2247A. I've been busy with other things and had the scope off for about 3 days. Turned it on this morning and noticed the trace was a little noisy without a probe connected and I also noticed a very faint high pitch noise that I haven't heard before. I didn't think much of it but after being on for about 5 minutes, the scope locked up and all of the LEDs in the horizontal section were off and all controls were unresponsive. When I turned the scope off, I noticed the screen displayed a little square that disappears, almost as if something was being discharged. I really don't know how I can explain it but usually when I turn the scope off, the display just turns off. I noticed this screen aberration when turning the scope off when I initially observed the lockup/error problem.

When I turned it back on, the high pitched noise was no longer present and it hasn't locked up again. The high pitched noise would point to something in SMPS, or at least I would think. Any idea how I can troubleshoot this further? My though was to leave the scope off for another few days , take the chassis out before restarting it and then if I get it to fail, check the voltages and see if anything looks to be out of spec. It seems like the scope doesn't like a cold, cold start and the failure disappears after the scope stays on for a bit. Almost seems like one (or more) of the caps are borderline.

Thoughts?

I have a sleepy-eye assembly, switch attached to cable, if interested. I got it from the Tek Country Store (Tek salvage and surplus). It appears to be unused.
Photographs at

/g/TekScopes/album?id=301673

Clark

Raymond! YES I mewant CRT expansion mesh, the SC504 have it bad, due to CRT geom, the SC501/2/3 do NOT

Cheers


Jon

I've had a couple of enquiries from US members here, requesting clarity on the new Customs Duties - which may or may not be applicable on my 24xx series Tekscope kits, which are shipped from here in Jerusalem, Israel.

For PERSONAL imports, which is EXACTLY what these are, when you buy the kits from me, there is what's called in Government language, a "De Minimus" level of US$800.

That means that any PERSONAL import (in this case, up to 3 kits) from Israel to the USA is EXEMPT from US Customs Duties, when the value is less than US$800, and 17% when the value is more than US$800.

Commercial imports (which these kits are not, unless you buy a number of kits for a commercial enterprise) from Israel are taxed at 17% from the first Dollar, irrespective of the value.

So, the bottom line is that if you (a US Resident) buy 1 or 2 kits from me, valued at about $70 each, then you are exempt from the new US Customs Duties.

I hope this helps to clarify the issue!

Regards

Menahem Yachad
www.condoraudio.com

According to Findchips.com, Quest Components has VN1316

Thanks to all that have posted - it looks like I'm just going to find the time to open it up and start diagnosing. My feeling, and that that seems to be the opinion here as well, is that the fault should be fairly easy to narrow down as all is working *except* for the display. Of course, finding the time is where the *real* work lies...

These parts are being operated in their linear region, so Rds(on) isn't relevant. As long as they can take the heat, what we need is agility, that is, minimal Ciss/Coss/Crss.
________________________________
From: [email protected] <[email protected]> on behalf of Chris Elmquist via groups.io <chrise@...>
Sent: Wednesday, April 2, 2025 11:18 AM
To: [email protected] <[email protected]>
Subject: Re: [TekScopes] horz output FETs in 2245?

On Wednesday (04/02/2025 at 05:47PM +0000), Dave Wise via groups.io wrote:

If I had a 2245 with your problem I'd be looking for... Hmm. Your parts are running naked, right - no heat sink? That's maybe 1W.

Yes-- they have no heatsinks and are spec'd at 3W max in the TO-39 can.

The left plate pair gets so hot I can't touch it but I realize that's not a
calibrated measurement.

An eBay seller has TO-92 VP0116 $15 for 10, glue on a copper fin. But nobody is selling VN1316 AFAICT.

There are also VP0120 and VN1320 which are similar devices with a higher
Vdgs (200V). These would likely work just fine too if they could be found.

Look at Mouser.com . They don't have any 160V P-channel RF MOSFETs so how about the regular ones? In 150V-300V select the lowest Ciss proxied as gate charge, that's Diodes Inc ZVP2545 in the SOT26-6 package. Put a copper fin on the drain pins and you should be okay.
For N-channel try Vishay SI3440 in TSOP-6. Second lowest gate charge and lowest Ciss.

Right. OK. Thanks. Ciss is the critical parameter then for performance
here? Was also wondering how critical the Rds (on resistance) would be
in this type of circuit? Modern FETs measure that in tenths of ohms
while these golden oldies measure it in 10s of ohms... eg, VN1316 is
at 40 ohm and VP0116 is at 25 ohm.

There's not a lot of clearance between the tops of these TO-39 and the
scope's enclosure though so some challenges with fitting new/different
stuff.

Could envision a little PCB that carries the SMT parts but has "leads"
coming out the bottom to mate up to the scope's PCB.

Chris

________________________________
From: [email protected] <[email protected]> on behalf of Chris Elmquist via groups.io <chrise@...>
Sent: Wednesday, April 2, 2025 9:28 AM
To: [email protected] <[email protected]>
Subject: [TekScopes] horz output FETs in 2245?


I was given a 2245 recently which of course doesn't work too well.

Investigation reveals that Q805 and Q806, in the horizontal right plate
output stage, are cold to the touch.

The service manual, section 6.2 (page 6-19) says,

The MOSFET output transistors (Q801 and Q802 left plate-- Q805 and
Q806 right plate) run hot. If either side is cold, it is defective.

So, that's me and now I need to find a couple of these VDMOS FETs, which
seem to have become quite rare.

They are Tek P/N,

151-1211 VN1316N2 N-Channel VDMOS FET, 160V, 250mA, 40 ohm
151-1212 VP0116N2 P-Channel VDMOS FET, 160V, 250mA, 25 ohm

Has anyone solved this problem with a modern replacement pair? and have
suggested substitutes? These are in TO-39 package which adds additional
challenge but I suppose TO-220 or equiv could be made to fit. Of course,
the real thing would be great too if there is a source.

Thanks for any leads!

Chris
--
Chris Elmquist

--
Chris Elmquist

internal CRT phosphor beam reflection ?

My money’s on scan expansion mesh (to increase deflection sensitivity) artefacts.

Raymond