开云体育

I have used a flatbed scanner to scan small parts, by adding a backlight. For some things I simply laid a clean, white teeshirt over the item, and pulled my magnifying florescent ringlight down to eliminate shadows on the edges. It proveded a lot more detail than my digital camera. One thing that I learned scanning printed material was to angle it slightly, then use software to straighten it rather than to attempt to align each page by hand. About 15 degrees gave good results. I got a lot loer error rate when doing scan to OCR with this method.

The white light spreader from an LCD monitor and the CFL or white LEDs should make a nice backlight to scan entire sheets of Microfiche. I have a pile of old USB flatbed scanners, (~25) and several came with an adapter to scan 35mm film or slides. Each of them came with a backlight module that plugs into the base for power.

Good day to all.

My trusty P6042 current probe died several years ago and I've not yet taken the time to repair (replace) the probe cable. This cable has died on me several times in the past and it's now too short to be useable.

Searching past messages suggested that I might be able to use a HDMI cable as a suitable replacement. I had originally thought of using a standard VGA cable - I will cut open as many samples of these and HDMI cables as I can lay my hands on and see if one is more suitable than the others. Guidance appreciated.

However, the reason for this post is to ask about replacing the electrolytic caps. I see that I did replace the original power supply reservoir caps quite some time ago - I haven't used Rubycon capacitors in more than a decade or two. I'll replace them again.

But I haven't looked closely at the other large capacitors on the board yet. If they are wet-slug tantalum, I'm tempted to leave them alone. If they are indeed simple electrolytic caps, I had better plan on replacing them as well.

My question to the group is this: what else should I be looking at when working on this instrument? It has worked fabulously for me for many years and I keep needing to use it - but just haven't made the time to repair it. That time is now, I guess.

Again - guidance is greatly appreciated.

Many thanks!

dwayne

--
Dwayne Reid <dwayner@...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
780-489-3199 voice 780-487-6397 fax 888-489-3199 Toll Free
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

On 3/29/2018 12:31 PM, cnc_joker wrote:

I had a look for any old microfiche but did not find any. <snip>

Hello--

Back in the day, two users of fiche archives were libraries and newspapers. It
might be worthwhile contacting either or both institutions in the Tek Museum area
to see whether either could provide machine time on a pro bono basis.

It's a long shot.

I unfondly recall viewing microfilm for a research project and getting
a headache and nausea due to the motion of the film in fast-forward mode.

Manual calls Y160 a 1Mhz quartz crystal. I ordered this

Roger,
Well... I can't tell I`m 100% sure.
I can tap with a x10 oscilloscope probe onto the 11A and 11B signals coming out of the 7A26 Vertical plugin, and the waveform, although not perfectly square (it's a little roundy in the corner), it doesn't show that slowly flattening voltage over this long 3us time period...
I assume the non-perfect corner I see (while probing the plugin output) is because I cannot properly reference the probe with a short ground lead so, I cannot take seriously anything immediately following the sharp edge. but the passive probing + long ground lead could not be concealing this 3us long voltage lagging.
If the problem I would be having would be in the first 100ns or so, I reckon that any artifacts I see could be coming either from the plugin or from the mainframe misalignment (or a combination of both), but 3us is just too much.
For a circuitry of that grade... anything slower than 1us is almost the same as DC... lol.
I also reckon that in the 10s or 100s of milliseconds, there can be other disturbances at play, like thermal imbalance (between different sides of complementary designs) or power supply mains ripple... but that's not the case here.
Yesterday, while I still didn't have chance to probe the P.S. voltages (inside the board, after decoupled), I was really convinced there was a decoupling issue... that right after the fast corner which consumes a lot of current... the available voltage was depleting and the output would be - then - being limited by the available supply, until the - lacking - decoupling would have time to recover.
But yesterday evening I probed all the important voltage supplies and bias points, and they're pretty much rock steady.
Not happy, I added additional decoupling in parallel, to each of those voltages... and neither made any difference to the displayed waveform so, I think it's safe to conclude that there's no decoupling issue (at least not on the Vertical Amplifier board).
I still need to find ways to rule-out a possible decoupling issue on the Vertical Channel switching board, that's difficult to reach and to probe at.

Happy easter to you all.

FT

Friend of mine has a 2215 and a 2225 I think. One of them is pretty much parts for some reason and we took the knobs for the other one. If the CRT will fit I can ask if he is willing to part with it.

But then you might find one elsewhere anyway with all that unobtaimium in there.

Bad news, I took out the CRT and has chips of glass inside , no plated. I did not make short measurements between electrodes. It must be kicked.. I ll try to get a donor CRT scope . Thanks All for the suggestions. Carlos.

I'm sending several photos, feel free to take your pick.

Thanks,
Bert

What does the manual say should be in that location? What frequency oscillator does this plugin use? It is going to be either 10MHz or 5MHz.

The two pins I can see may be for the oscillator. The oscillator needs a total of 4 pins: Vcc, ground, output, and a 4th pin which is unused but it supports that corner of the module.

To save space they sometimes mount the oscillator on the back side of the PC Board as long as you can still get to the frequency adjustment hole in the top of the oscillator.

Dennis Tillman W7PF

There are different options for the oscillator xtal IIRC, 'ovenised' (opt 1?) or not and either 5 or 10MHz - so one empty socket may be ok if there is a crystal somewhere else I guess!

Good hunting!

Adrian

Hi Fabio,

Are you sure this problem is in the mainframe Y amplifier and not the vertical plugin? I assume that if you don't have a standardizer you have to go via a normal Y amplifier. What are you using?

Regards,

Roger

Good thought. If Bert doesn't do that, I will when I get the photos.


________________________________
From: [email protected] <[email protected]> on behalf of toby@... <toby@...>
Sent: Thursday, March 29, 2018 1:31 PM
To: [email protected]
Subject: Re: [TekScopes] Back feet for 335 scope

On 2018-03-29 3:19 PM, Jeff Davis wrote:

Hi Bert,


I think you want to send the photos to me, not Lee (Lee was test fitting the feet on his 335). I was the one who
sent you the samples. You can send the photos to me at n0dyjeff@... or jeff@....


Thanks!

Jeff

It might be good to post pics to the gallery here, for other people
contemplating ordering replacement feet?

--T

On 2018-03-29 3:19 PM, Jeff Davis wrote:

Hi Bert,


I think you want to send the photos to me, not Lee (Lee was test fitting the feet on his 335). I was the one who
sent you the samples. You can send the photos to me at n0dyjeff@... or jeff@....


Thanks!

Jeff

It might be good to post pics to the gallery here, for other people
contemplating ordering replacement feet?

--T

Hello All,
Following the restoration of my last acquisition, a Tek 7623A, after fixing a few minor issues (Fan, Compressed & Inverted Horizontal sweep, MIX time base switch broken, etc...), and after consulting with the group on best approaches to calibrating the Vertical Amplifier without having a Signal Standardizer plugin, I came to the point of calibrating the Vertical Amplifier of this lovely beast.
Following some of the group's advice, I already manage to get the DC calibration department right (Gain - R2446), and also, the Thermal Balance calibration (R2527).
Getting to get a decent square wave displayed on-screen, however, always puts up some challenge and, as frightened as I always am about the highest frequency performance, it seems that this chapter is (has been) much more a challenge for the designers than it actually is to the person (me) doing the calibration...In other words... Clean fast edges and sharp flat-corners around the very first few nanoseconds always seem to be more easily obtained that I anticipate.
However, I always seem to have problems to get those damn medium to long-term flat-tops, flat.
Therefore, the main issue of this topic.
After the initial fast edge reach 96% of the full DC level (4% lacking), the square wave top takes about 3us to reach 100%.
I made 2 YT videos showing the present situation and the insufficient effect of the only two adjustments that have some influence, R2409 (1st microsecond or so) and R2509 (1st 500ns or so).]




I checked already.
1. Power Supplies Voltage and Ripple / Spike OK: +50V, +50 DCPL, +15V, +15V DCPL, -15V and -12.5V.
2. Decoupling capacitors OK: +50V DCPL (C2593 0.1u), +15 DCPL (C2595 15u), -12.5V (C2597 15u), 2nd Stage / Thermal Balance Bias (C2524 1nF), 1st stage / Dly Line Bias (C2403 10nF)
3. Voltages and waveforms at amplifier's output on the right P-P range (for the displayed waveform) and DC levels (about +25V).
4. DC Voltages at different biasing points OK.
5. Plugin output waveform (at pins A11 and B11 of backplane connectors) don't display this 4% lacking during the first 3us.

6. Maybe a problem here... Signal coming out of delay line, entering at J2401 / J2501, seem to show more or less the same 4% lacking, slowly getting to 100% in about the same time... but it's more like a normal, rounded square wave.
It doesn't display a clear knee at about 96%, and it looks more like a square wave lightly integrated (i.e.: asking for some HF boost).

7. I fully removed the Vertical Channel Switch Board, cleaned contacts, removed and reseated the Tek custom vertical switch (U2340) and it didn't show any improvement.

8. Last, but not least, while checking the waveforms at the bases and emitters of Q2441 and Q2541, the looked rather different (the peak-peak amplitude at one of them was much bigger than the other (about double)...
However, there's no distinguishable difference of the waveforms at their collectors (maybe because they are balancing out?)
Taking both transistors out, and testing them on my AVR transistor tester, one showed distinctively different than the other, more than I would consider normal for 2 transistors being used on a complementary stage like this.
A difference of almost 20mV in Vbe (one have 700mV the other 720mV), and a difference of about 30% of hFE (one have 35, the other almost 50).

Questions:
A. Any ideas... suggestions on further checks / tests to do?
B. Can those transistors be causing the problem? What would be a modern, currently available equivalent to an A5T4261 transistor?
It's a 2GHz fT; 2.5pF Ccb; >30hFE; 12V VCEmax, 80mA Icmax

Thank you all,
Rgrds,
Fabio

There won't be any signal until you install the crystal.

Yep. I hooked up a probe to the 1mhz TP and nothing but DC. I think I figured out one thing anyway.

Hi Bert,


I think you want to send the photos to me, not Lee (Lee was test fitting the feet on his 335). I was the one who
sent you the samples. You can send the photos to me at n0dyjeff@... or jeff@....


Thanks!

Jeff



________________________________
From: [email protected] <[email protected]> on behalf of Bert Haskins <bhaskins@...>
Sent: Thursday, March 29, 2018 12:14 PM
To: [email protected]
Subject: Re: [TekScopes] Back feet for 335 scope

Lee, I received the new feet late today and they look very nice.
I should probably send you the pictures off list so please let me know
where to send them.
Many thanks,
Bert

On 3/1/2018 7:05 PM, Lee Houde wrote:

Jeff, the foot is packaged up in a USPS Small Flat Rate box. Hopefully I will remember to mail it tomorrow and you will likely have it Monday. You should have received an email from the USPS with the tracking number; if not yet then you should when they have the package. Just remember to save my shipping label for the return address.

Now to find a source for 2445 and 2430A feet....

Looks like a crystal socket to the right of the variable capacitor. Maybe a 1 MHz reference crystal?

Lee, I received the new feet late today and they look very nice.
I should probably send you the pictures off list so please let me know where to send them.
Many thanks,
Bert

I have 2 DSA601/602's that used to work. One still works but with problems. This is probably power supply problems but I thought I'd collect a few other possibilities before I dig in. Someone may have seen this before.The 2 pictures display the problem with the vertical part of the trace. Signal source is the Tek pocket generator.

/g/TekScopes/album?id=41301