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Re: Sony/Tektronix 370 : Gray Encoders unexpected value jumps

 

@ Arie de Muijnck
As bouncing is typically short (~ .5 ... 1 ms) following mechanical action we are talking about 100 pF...1 nF; under 5 V this means .5 to 5 nC which is very low.
If you read me well you'd have seen that my purpose is to parallel the resistances, not the switches.
Did you have a look at the mentionned schematic? The power induced by capacitors switching will be dissipated by the 74HC139. According to its datasheet formula (Note 1) estimated Pd will be 26 nW per coder step and per gate, worst case. Also very low.
Anyway the question is still: is there a solution to avoid or limit the value jumps?
Re: OT: The analog computer lives on

 

Yes, it is stored in mechanical form! Who said storage needed to be digital or tape (paper or mylar)?

Hidden Figures is great, even though there are some location errors in it.? Only we who grew up in Virginia would notice.?

Frank DuVal

On 2/23/2024 10:02 PM, greenboxmaven via groups.io wrote:
Is a differential analyzer a form of analog computer? There is a good scene of one operating in the beginning of the film "When Worlds Collide". Other amazing analog computers are the mechanical fire control computers for battleships and submarines, and the Norden bombsite. Despite all of these, can they correctly be called computers? The definition of a computer I was told some time ago is "A control or calculating apparatus with a stored operating system"

?? Bruce Gentry, KA2IVY

On 2/23/24 18:30, EJP via groups.io wrote:
When you think about it, the analogue computer is really a Laplace Transform.

EJP
Re: Sony/Tektronix 370 : Gray Encoders unexpected value jumps

 

On 2024-03-06 13:48, Christian F1GWR wrote:


When rotating Vert, Horiz and Step/Offset front panel knobs large
unexpected jumps in settings occur.
Gray encoders S210-220-230 are
unobtainum. Unsoldered the culprits, unmounted the sealed blue plastic
parts and drowned them into alcohol for 24 hours as they had oil stains
over them. Unfortunately this didn't help.
Now the question is: wouldn't
there instead be a contact bouncing phenomenon misleading the MC68000
processor? If this is the case would it be wise to add integrating caps in
parallel to the R130...4 pull-ups? (see Service Man p.303 here:
) Or would this mod impair other processor I/O's?
Any help appreciated.
Don;t do that. Placing a filter cap _directly_ over a contact will cause big discharge currents and will damage the contact. Always use a resistor in between to limit the current.

Arie
Re: What caused this on electrolytics in 422?

 

I also see it on some insulated wire, but not on all the wire. Since it is so selective, I still think the mold theory is best.
I looked at it on a 10x magnifier and still cant tell what the heck it is. Definitely dont want to breath it!

Grayson
KJ7UM
Check out Hollow-State Design
tinyurl.com/hollowstatedesign3 <>
My technical blog:
kj7um.wordpress.com <>
Sony/Tektronix 370 : Gray Encoders unexpected value jumps

 

When rotating Vert, Horiz and Step/Offset front panel knobs large unexpected jumps in settings occur.
Gray encoders S210-220-230 are unobtainum. Unsoldered the culprits, unmounted the sealed blue plastic parts and drowned them into alcohol for 24 hours as they had oil stains over them. Unfortunately this didn't help.
Now the question is: wouldn't there instead be a contact bouncing phenomenon misleading the MC68000 processor? If this is the case would it be wise to add integrating caps in parallel to the R130...4 pull-ups? (see Service Man p.303 here: ) Or would this mod impair other processor I/O's?
Any help appreciated.
Sony/Tektronix 370 Curve Tracer "drawer" pull-out for servicing

 

It took me some time to find out, as the service manual does not explicit what the "drawer" is. It appears this is the lower part of the tracer, under the display and upper front panel. It's a slider assembly including Lower Key panel, Bubble memory, component fixtures holder, collector supply switch. Explanation only appears in 370B Service Manual on page 4-15. You must remove two lower lateral brackets (with adjustable potentiometers markings) held each by 8 screws (four flat-head and four round-head. And then push forward the said drawer by its rear corners.
HTH.
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

RE SC502 CRT HV Blanking :
likely suspects:

High meg resistors in HV PS, Focus/inten
Scratchy pots focus, astig, inten


Easy to try that first.

Jon
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

Thank you for the informative video Bob. Efforts like that make it more practical to keep these wonderful old instruments going for a while longer. The magic smoke came out of my SC503, going to have to investigate soon.
Re: What caused this on electrolytics in 422?

 

I have seen these on my capacitors too. I do not think this is mold. I asked around on other forums, and the unanimous answer was the plastic around the cap degrading. Sort of like the fat that comes out of rotting meat.
FS: Tektronix 7613 w/Horizontal plug-in in, and vertical plug-in

 

Hi, I am selling my Tektronix 7613. The scope works perfectly fine. I have uploaded some photos to imgur.

The 7613 itself has some missing parts, which inlide the plastic bezel, and metal blue plastic filter holder. The plastic bits of the readout intensity and beam intensity is missing, but they work.

It's obvious in the images. Other than that, nothing else is missing.

The selling offer is, one fully functional 7613, a horizontal plug in of your choice, and if you pay an extra $10, you get a 7A26.

The choices for the horizontal plug-in are a 7B53A(see notes), or a TD-1085/U(fully funtional)

Notes: 7B53A is faulty, this is due to the B-Sweep cam not acruating the B-sweep shaft. This is likely due to brittle plastic that has broken down over time. A sweep still works perfectly fine.

B-sweep does work, it's just a mechanical issue. As seen in photos, mixed sweep still works.

Also the trigger source select knob on the 7A26 has broken off.

Images:

Located 95608 Carmichael CA, USA.

Hoping to sell for maybe $130? Will consider trades.
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

In trying to clean things up I delete the wrong message. Here's the correct video link:

--
Bob Haas
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

Barry,

The d-c restorer diodes are on the high voltage board, A5 page <8> in the manual. The 1mfd condensers are on boards A1 and A2. All of this is on page 156-157 when looking at the PDF of the manual. The ULD types are radial and can replace axial types. Bend the leads at the bottom so they are a a right angle to the condenser body then bend where the leads will go in the holes easily, solder then trim any extra lead off. The ULD types are designed for the high frequency filtering these see, high temp and low ESR with a long life. I see Mouser has the ULD in 400V for this replacement. This is the Mouser p/n for the 22meg resistor (R888): 594-5053DM22M00F. The bad pot can be replaced with a fixed resistor from ground to the low side and the top to the 70V with the wiper to the circuit as usual. This is when you know the bias you want and have a lower value such as 20,000 ohms. A 1/2W or so 50,000 ohm pot as the replacement is fine. It likely will be physically bigger than original. That is set and left alone being inside the unit. If you want fine control of this, a 10/20 turn type can be used. I doubt that is necessary.

Mark
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

I would like to thank Bob for the video! So, thank you Bob! Well done!

I am replacing the following on the A1/A5 board related to the HV supply:

C850, C851, C881, C882, C883, C885, C887, R888

Regards,

Barry
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

Here is the video:

--
Bob Haas
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

Bob,

Which tantalums are you having to replace under the A5 board?

Barry
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

Bob,

Looking forward to the video! Thanks!

Those capacitors are actually on the A5 Aux board. I had that board out for cleaning and inspection. I did not check the capacitor values.

I've been delayed... lost 2 transistors on the -20V supply.

Thanks!

Barry
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

The DC Restorer caps are C881, 2, 3, 5 and 7. They go between the main (A1) board and the HV auxiliary (A5) board. In my experience, they are more likely the problem than the diodes on the A5 board. But replacing the caps is a bear. By coincidence, I am doing the final edits of a video on replacing two tantalums on the main board which are under the A5 board and require removing the A5 board. I will add this intensity problem to the video, which I hope to get out today.

--
Bob Haas
Re: SC502 Trace Issues - Beginning and ending of trace connected.

 

CR884 and CR885, they are on A5 board.

Regards,

Ignacio

El 05/03/2024 a las 17:33, Barry Breaux escribió:
Mark,

Thanks for the help! Greatly appreciated!

I am thinking the Bias pot is R873, its labeled Beam. Last week I found that pot had come apart. No trace. If I pressed down on that pot the trace came alive. I ran the scope with a 20K pot and it functioned. Then I wired the circuit with fixed resistors. 25k, 25K with a center tap until the replacement pots arrive.

I checked the 1uf capacitors with my Sencore meter and do not suspect them to be the issue. I will order replacements. The ones in there are axial and the ULD you recommended is radial. Is that what you had in mind?

I have ordered the 1N4937 diodes. It was previously recommended to replace the diodes in the DC Restorer circuit. I am not sure what the DC Restorer circuit is. Can you point that out.

Thanks!

Barry

--
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www.avast.com
Re: 7704A - Readout Stretches Vertically

 

When I get the vertical amplifier's damaged IC replaced (and the problem is still there), I'll add a picture in the group page.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Ozan" <ozan_g@...>
To: "tekscopes" <[email protected]>
Sent: Tuesday, March 5, 2024 10:40:51 AM
Subject: Re: [TekScopes] 7704A - Readout Stretches Vertically
Hi Barry,
Is there a picture of how the distorted characters look like?
Ozan


On Tue, Mar 5, 2024 at 06:36 AM, n4buq wrote:


At issue is that the stretching occurs even when the trace is not extended
past the top or bottom graticule. It isn't horrible but quite noticeable. I
have another 7704A, two 7603s, and a 7514 and none of those show this problem
quite like I see it on this 7704A. Yes, with an AC signal that approaches or
passes the CRT's vertical limits, I see rippling on virtually all these scopes
and I understand that but this "stretchy, multiply-scanned image" thing is
only seen this way on this 7704A.

Again, it isn't like I can't read the characters, etc., it just seems it is
abnormal and would like to find out why.

Thanks,
Barry - N4BUQ

I looked back through this thread, and I don't know what the deal is here,
so
please forgive if I've missed something. In the OP, I think it was an issue
about the readout distorting severely when the vertical signal is
over-driven
and off-screen. This is entirely normal behavior. The Tek verticals tend to
have great dynamic range, but even they have their limits. I think that
Albert
et al have touched on this in previous messages about what it looks like at
normal levels.

If the RO works fine with signal displays on-screen, or a little beyond,
then
fine. If they don't do as well way off-screen, then you're tilting at
windmills. The RO is irrelevant if you can't see a waveform anyway. If you
see
weird non-linearities or stepped conditions on overdrive, it's likely
thermal
delays, sweep rate, and RO framing rate getting into the picture too. What
matters is how it looks when things are "normally" displayed. If OK, then
case
closed. At certain sweep rates and vertical excursion, it's quite normal to
see
the RO rippling up and down a little. The question is, what's acceptable. It
should be not obnoxious, and preferably, but not invisible.

Ed
Re: 7704A - Readout Stretches Vertically

 

Hi Barry,
Is there a picture of how the distorted characters look like?
Ozan

On Tue, Mar 5, 2024 at 06:36 AM, n4buq wrote:


At issue is that the stretching occurs even when the trace is not extended
past the top or bottom graticule. It isn't horrible but quite noticeable. I
have another 7704A, two 7603s, and a 7514 and none of those show this problem
quite like I see it on this 7704A. Yes, with an AC signal that approaches or
passes the CRT's vertical limits, I see rippling on virtually all these scopes
and I understand that but this "stretchy, multiply-scanned image" thing is
only seen this way on this 7704A.

Again, it isn't like I can't read the characters, etc., it just seems it is
abnormal and would like to find out why.

Thanks,
Barry - N4BUQ

I looked back through this thread, and I don't know what the deal is here,
so
please forgive if I've missed something. In the OP, I think it was an issue
about the readout distorting severely when the vertical signal is
over-driven
and off-screen. This is entirely normal behavior. The Tek verticals tend to
have great dynamic range, but even they have their limits. I think that
Albert
et al have touched on this in previous messages about what it looks like at
normal levels.

If the RO works fine with signal displays on-screen, or a little beyond,
then
fine. If they don't do as well way off-screen, then you're tilting at
windmills. The RO is irrelevant if you can't see a waveform anyway. If you
see
weird non-linearities or stepped conditions on overdrive, it's likely
thermal
delays, sweep rate, and RO framing rate getting into the picture too. What
matters is how it looks when things are "normally" displayed. If OK, then
case
closed. At certain sweep rates and vertical excursion, it's quite normal to
see
the RO rippling up and down a little. The question is, what's acceptable. It
should be not obnoxious, and preferably, but not invisible.

Ed
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