Re: Card Edge Connectors on a 7704
David,
that is EXACTLY what I need, and it may explain why one of the remaining slots (B HORIZ) is not working properly: it looks like the lower half of the A cover plate is loose, which is causing me to be unable to get a sweep.
That's actually good news. I have all the original (deteriorated) cover plates, and I have at least one parts scope that might be able to donate cover plates, so this is likely to be a fixable scope.
-- Jeff Dutky
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(2) Tektronix 475 Oscilloscopes West of Beaverton, OR
In case anyone nearby and interested. It just hit craigslist yesterday. Looks like a good buy.
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Re: Tek 453 resistor specs -- Horiz amp
Just curios why a carbon film. Wouldn't metal film be as good or, possibly, a better choice for stability, etc.?
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Mike Merigliano" <mmerig@...>
To: "tekscopes" <[email protected]>
Sent: Friday, April 1, 2022 7:58:51 AM
Subject: Re: [TekScopes] Tek 453 resistor specs -- Horiz amp Hello Mark,
Thanks for the advice -- I will try it soon. I will probably put in 1/4W
1% carbon film to replace the broken ones. That might be over-kill, but
the cost difference should be small. I usually order from Mouser.
The broken lead was on R631. Also R638 -- I should have said two
resistors in my earlier message.
In the midst of my repair, a wire came out of the intensity pot (the
wire did not look broken, looked like a cold solder), and I started
chasing down problems in the Z-axis circuit until I went back and looked
at that pot. There was a slow-blow fuse for the Z-axis (should be
fast-blow), so while checking the HV oscillator, I switched that out.
This scope did not work at all when I bought it used years ago -- just a
dot on one channel, and then only with the beam finder pressed. There's
a strange diode addition in the B-delay sweep circuit, and some other
obvious repairs, so whoever had it before me changed some things in that
circuit for some reason. Some of the transistors were plugged in the
wrong way. Broken horizontal deflection transistors were a key problem.
I will re-visit that diode addition. It looked superfluous, or maybe
helpful, but that diode could be part of the issue.
On 3/31/2022 7:34 PM, Mark Vincent wrote:
Mike,
Which resistor did the lead come out of?
As for replacing or new build, I use 1% Xicon 1/2w. I have found that the
Chinese sellers on "that auction" site have excellent 1-5W 1% types and are of
the proper physical size. The temperature drift of these is 100 ppm/deg.C while
the Xicons are 50 ppm. Using 1/4W 1%, I will use in places where the power is
low enough. I like the low drift, very low noise and accuracy of the 1% types.
This is my personal choice from using them long enough in enough things to
decide to use these. Carbons are alright in some places. Replacing a carbon
with a film type is usually better.
By the dot being off that much, it sounds like your "mag register" pot need
adjusting. That is done by putting in a signal, setting the horiz. pots to
centre, setting the sweep to 10x then getting the centre of the signal in the
centre of the screen. Using the 1kc test signal to the input will give ten
waveforms on 1ms/sec. in the normal position. You would want the centre of
waveform five in the centre at 10x setting. This should get the dot in or near
the centre when in XY mode. Moving the position knob some is likely.
Mark
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Re: 464 Working properly?
Clark - that's the one. It's a 9V AC plugged into the wall
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Re: 464 Working properly?
David - yeah, I have the ground plugged into where the tutorial shows. I've used both the 1x and 10x probe that came with the scope.
For reference, here's the tutorial: The behavior your describe where the line "bounces" up is what happens. With the variable voltage knob on the generator, the line will ease up and down as I turn it. Maybe it IS working then? I expected a sine wave based on the PDF from the tutorial. I link that here:
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Re: 464 Working properly?
The behavior your describe where the line "bounces" up is what happens. With the variable voltage knob on the generator, the line will ease up and down as I turn it. Maybe it IS working then? I expected a sine wave based on the PDF from the tutorial. I link that here:
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Re: Tek 453 resistor specs -- Horiz amp
Thanks Ozan -- I will look into R1003 and 3F? too.
The last time I checked (a while ago) all of the power supply voltages were good. But when I open it back up I will double-check.
Except for the odd shift and intensity problem in the Ext Horiz, position, everything else works fine.
My profession is plant ecology, and although there are some plant physiology parallels to circuits, fixing a scope is a bit out there for me. But it's a nice change, and I would rather do that than crossword puzzles. I also have a lot of old audio gear that needs maintenance once in a while, and I have built some things, like a preamp.
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On 3/31/2022 8:13 PM, Ozan wrote: -----
For horizontal shift Mark's reply is most likely. If it doesn't fix the shift confirm that you see 0V at connector CJ of sheet <10> with Ext Horiz grounded, and Ext Horiz mode selected.
Intensity could be because of shifted R1003 on page <14> or dirty contact 3F in the same sheet.
Are all supply voltages at their target levels?
Ozan
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Re: Tek 453 resistor specs -- Horiz amp
Hello Mark,
Thanks for the advice -- I will try it soon. I will probably put in 1/4W 1% carbon film to replace the broken ones. That might be over-kill, but the cost difference should be small. I usually order from Mouser.
The broken lead was on R631. Also R638 -- I should have said two resistors in my earlier message.
In the midst of my repair, a wire came out of the intensity pot (the wire did not look broken, looked like a cold solder), and I started chasing down problems in the Z-axis circuit until I went back and looked at that pot. There was a slow-blow fuse for the Z-axis (should be fast-blow), so while checking the HV oscillator, I switched that out. This scope did not work at all when I bought it used years ago -- just a dot on one channel, and then only with the beam finder pressed. There's a strange diode addition in the B-delay sweep circuit, and some other obvious repairs, so whoever had it before me changed some things in that circuit for some reason. Some of the transistors were plugged in the wrong way. Broken horizontal deflection transistors were a key problem.
I will re-visit that diode addition. It looked superfluous, or maybe helpful, but that diode could be part of the issue.
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Show quoted text
On 3/31/2022 7:34 PM, Mark Vincent wrote: Mike,
Which resistor did the lead come out of?
As for replacing or new build, I use 1% Xicon 1/2w. I have found that the Chinese sellers on "that auction" site have excellent 1-5W 1% types and are of the proper physical size. The temperature drift of these is 100 ppm/deg.C while the Xicons are 50 ppm. Using 1/4W 1%, I will use in places where the power is low enough. I like the low drift, very low noise and accuracy of the 1% types. This is my personal choice from using them long enough in enough things to decide to use these. Carbons are alright in some places. Replacing a carbon with a film type is usually better.
By the dot being off that much, it sounds like your "mag register" pot need adjusting. That is done by putting in a signal, setting the horiz. pots to centre, setting the sweep to 10x then getting the centre of the signal in the centre of the screen. Using the 1kc test signal to the input will give ten waveforms on 1ms/sec. in the normal position. You would want the centre of waveform five in the centre at 10x setting. This should get the dot in or near the centre when in XY mode. Moving the position knob some is likely.
Mark
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Re: Card Edge Connectors on a 7704
All you probably need is replacements for the plastic bits that clip onto the sides of the sockets. Without those the contacts won't make contact - at least not consistently.
AFAIK they are only obtainable from another 7000 series mainframe (unless someone has made replacements using 3-D printing - which I suspect may not be possible). Be warned those plastic bits need to be fitted the right way round.
D.
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Jeff Dutky Sent: 01 April 2022 09:05 To: [email protected]Subject: [TekScopes] Card Edge Connectors on a 7704 I just received a 7704 and several of the card edge connectors on the main interface board have their left and right (or A and B?) covers falling off. They are not completely disintegrated yet, though it looks like a previous owner tried to glue them back together, with limited success. Other than the deteriorating covers on the card edge connectors the scope appears to be working. I can get readout on the two bays whose connectors are intact, though I have not managed to get stable traces, and the CRT seems bright and crisp. Some of the controls are stiff or frozen, but the scope is also quite dirty so some stiff controls are to be expected. The contacts on the card edge connectors look like they are still in good condition, but I am wary of trying to insert any plug-ins for fear of damaging the contacts. The housings for the contacts do not appear to have been damaged or to have disintegrated yet, so I am wondering what my options are. Do I absolutely need to have covers in place? Will I damage the connectors if I try to insert a plug-in with the plastic covers missing? I know that replacing the connectors is a big job, but I happen to have a parts scope that I may be able to harvest connectors from. Is this reasonably doable? Has anyone tried to 3D print the cover plates? ¡ª Jeff Dutky
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Re: Card Edge Connectors on a 7704
Jeff the 1970s..1980s plastics loose plasticisers and become brittle and crumble, PCB edgemand Tektronix "harmonica" inline PCB cables.
3D printer do not give an accurate reproduction at such fine r¨¦solution and the 3D mat¨¦riel is poor characteristics.
The original PCB card edges connectors can still be found with persistent search.
We performed such a replacement of PCB edges connection on a 1973 Eventide Instant Flanger studio sound we designed....PCB edge connectors has outgassed!
Bon courage
Jon
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Card Edge Connectors on a 7704
I just received a 7704 and several of the card edge connectors on the main interface board have their left and right (or A and B?) covers falling off. They are not completely disintegrated yet, though it looks like a previous owner tried to glue them back together, with limited success.
Other than the deteriorating covers on the card edge connectors the scope appears to be working. I can get readout on the two bays whose connectors are intact, though I have not managed to get stable traces, and the CRT seems bright and crisp. Some of the controls are stiff or frozen, but the scope is also quite dirty so some stiff controls are to be expected.
The contacts on the card edge connectors look like they are still in good condition, but I am wary of trying to insert any plug-ins for fear of damaging the contacts. The housings for the contacts do not appear to have been damaged or to have disintegrated yet, so I am wondering what my options are.
Do I absolutely need to have covers in place? Will I damage the connectors if I try to insert a plug-in with the plastic covers missing?
I know that replacing the connectors is a big job, but I happen to have a parts scope that I may be able to harvest connectors from. Is this reasonably doable?
Has anyone tried to 3D print the cover plates?
¡ª Jeff Dutky
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Re: 464 Working properly?
Is it this gadget?
It requires an AC input, 9V to 12V. Is it possible that you have attached a DC source?
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Re: "Ghost" Image on CRTs with Expansion Mesh (e.g. 475, 485, etc.)
Jeff,
the assumption of a disconnect inside the CRT is likely true. Varying the mesh voltage has a visisble effect on ghosting indeed, some Volt up or down make a significant difference when the CRT is ok. Reason why I know? I recently received a hp 5420A with a broken CRT (damaged during transportation, what a bummer!) This CRT is straight away unobtainium, but I figured that the old-model hp 8566/68 CRT might fit, except that the voltages, including the mesh voltage, are different. Under the operating conditions in the 5420A, the mesh voltage should land somewhere close to 0V instead of about 42V of the original CRT. Popped in the tube, noticed HUGE amount of ghosting when powering up, re-wired the mesh wire to the wiper of a 47k trimpot connected between the mesh supply and GND, adjusted voltage, ghosting gone. Finally omitted the trimpot because the result was good enough with the mesh wire just connected to GND.
Chris
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Re: 464 Working properly?
Do you have an instruction book for it? There is some information on the web. I did not search for a free instruction book but its worth your doing so.
?? Have you much experience using a scope?
?? If you can see the calibrator using a probe the scope is working. Try another signal source, even just put your finger on the end of a probe, you should see a lot of noise and probably hum. I am not familiar with the? 464 but from what's on the web it appears to be a fairly straight forward scope.
?? Do you have any other instrument that can confirm there is anything coming out of your "tutor"?.
?? See: <>
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On 3/31/2022 12:09 PM, Pseudo wrote: I'm still very new at learning how to use a scope, but I'm getting mighty
frustrated.
I bought a used 464 and have been able to get it to display a straight line
as well as its square wave from the calibration thing on the back. But
beyond that, nothing. I have a little 9v "tutor" that is supposed to
generate different signals but I can't even get past step 1: read voltage.
I've watched tutorials online and get that there's a balance between the
delay and the volts per div knobs but no amount of adjustment will show me
anything beyond a straight line.
Maybe the generated signal is outside the range of this scope? Is there
another test I can do to see if it's even functioning?
Thanks for your help!
Rick
--
Richard Knoppow
dickburk@...
WB6KBL
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Re: -2465B - trace show gaps when turn on readout -requesting help
Hi
I solved the issue. I was not the U2890. I was a broken trace underneath U2965- probably a result of the leaky capacitor and at that time for repair I did not notice the broken trace because it was underneath the IC. It was the connection from U2965 (pin8) to to U2890 (pin 10/9). - (working as an invertor). It was partially working because the inputs were coupling capacitively- that why I could it make worse by touching the IC with my finger. BTW the A5 schematic is totally wrong and does not show that connection ( show to a different gate of U2890). Fortunately I had working A5 board and I could measure the traces..
Maybe there is an update schematic - please let me know.
Bernd
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2465B - trace show gaps when turn on readout SOLVED
Hi
I solved the issue. I was not the U2890. I was a broken trace underneath U2965- probably a result of the leaky capacitor and at that time for repair I did not notice the broken trace because it was underneath the IC. It was the connection from U2965 (pin8) to to U2890 (pin 10/9). - (working as an invertor). It was partially working because the inputs were coupling capacitively- that why I could it make worse by touching the IC with my finger. BTW the A5 schematic is totally wrong and does not show that connection ( show to a different gate of U2890). Fortunately I had working A5 board and I could measure the traces..
Maybe there is an update schematic - please let me know.
Bernd
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Re: Tek 453 resistor specs -- Horiz amp
On Thu, Mar 31, 2022 at 05:22 PM, Mike Merigliano wrote: After switching to Ext Horiz, the trace was way off to the left, so I have to
turn up the intensity knob to 3 o'clock and the Horiz Position knob to 1
o'clock. Normally, In A sweep, the Intensity knob is around 11 o'clock, and
when in A Intens B or B delayed, the Intensity is at noon.
Is the low intensity and shifted position while in Ext Horiz normal? I did not
see anything in the manual about this. Also, the phase shift a 1 MHz is 42
degrees. Is this excessive? The shift negligible/invisible at 100 KHz. ----- For horizontal shift Mark's reply is most likely. If it doesn't fix the shift confirm that you see 0V at connector CJ of sheet <10> with Ext Horiz grounded, and Ext Horiz mode selected. Intensity could be because of shifted R1003 on page <14> or dirty contact 3F in the same sheet. Are all supply voltages at their target levels? Ozan
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Re: Tek 453 resistor specs -- Horiz amp
Mike,
Which resistor did the lead come out of?
As for replacing or new build, I use 1% Xicon 1/2w. I have found that the Chinese sellers on "that auction" site have excellent 1-5W 1% types and are of the proper physical size. The temperature drift of these is 100 ppm/deg.C while the Xicons are 50 ppm. Using 1/4W 1%, I will use in places where the power is low enough. I like the low drift, very low noise and accuracy of the 1% types. This is my personal choice from using them long enough in enough things to decide to use these. Carbons are alright in some places. Replacing a carbon with a film type is usually better.
By the dot being off that much, it sounds like your "mag register" pot need adjusting. That is done by putting in a signal, setting the horiz. pots to centre, setting the sweep to 10x then getting the centre of the signal in the centre of the screen. Using the 1kc test signal to the input will give ten waveforms on 1ms/sec. in the normal position. You would want the centre of waveform five in the centre at 10x setting. This should get the dot in or near the centre when in XY mode. Moving the position knob some is likely.
Mark
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Re: "Ghost" Image on CRTs with Expansion Mesh (e.g. 475, 485, etc.)
A CRT expert I spoke to today said the "can" behind the mesh is more positive than the mesh and attracts and collects the secondary electrons. There is an electrode on the CRT symbol labeled "horizontal deflection plate shield" which may be the "can" the expert was referring to, but I'd have to check back with him on this.
--
Bob Haas
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While you're at it, you should also verify Vcc to the processor, pins 8 and 35, if you haven't already done so. Use a scope when checking power and ground pins to make sure there's nothing weird happening. -mark On Thu, Mar 31, 2022 at 04:32 PM, I said: ... I would check that both your processor Vss pins (1 and 21) are connected to
ground. Maybe you have a bad socket. ...
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David C. Partridge
Jean-Paul
Bob Haas