Glenn,
3 of the 5 digits work OK. My original description of the problem was not clear.
One digit is missing the center horiz segment, another digit is missing the top horiz segment.
The other 3 digits are fine.
Hank
________________________________
From: "TekScopes@..." <TekScopes@...>
To: TekScopes@...
Sent: Tuesday, February 19, 2013 2:49 AM
Subject: [TekScopes] Digest Number 7355
All about classic Tektronix CRT o'scopes
All about classic Tektronix CRT o'scopes Group
15 New Messages
Digest #7355
1a
Re: What use for a 640 Ohm 1x Probe? by "KeepIt SimpleStupid" KeepItSimpleStupid
1b
Re: What use for a 640 Ohm 1x Probe? by "Don Black" donblack1au
1c
Re: What use for a 640 Ohm 1x Probe? by "Philip" ndpmcintosh
1d
Re: What use for a 640 Ohm 1x Probe? by "David" david_william_hess
2a
Re: Tektronix 2465 capacitors etc. by "Chris" digitalinuxguy
2b
Re: Tektronix 2465 capacitors etc. by "John Snyder" ykochcal
3a
DC504 counter display by "HankC" hankc918
3b
Re: DC504 counter display by "Chris van Lint"
3c
Re: DC504 counter display by "David" david_william_hess
3d
Re: DC504 counter display by "taylorvandy" taylorvandy
3e
Re: DC504 counter display by "Miroslav Pokorni" mpokorni1
3f
Re: DC504 counter display by "Glenn Little WB4UIV" glittle_29445
4a
Manual / schematic for Leader 524S counter? by "Dave C" davec2468
4b
Manual / schematic for Leader 524S counter? by "Dave C" davec2468
5a
Tek 485 by "John Polakowski" johnpolakow
Messages
1a
Re: What use for a 640 Ohm 1x Probe?
Mon Feb?18,?2013 8:19?pm (PST) . Posted by:
"KeepIt SimpleStupid" KeepItSimpleStupid
I'm wondering if it could be an RF probe.? . com/rfprobe1. htm
Another I have studied is an old Fairchild that is in good condition that
has a resistance of 640 ohms end to end on the center conductor. To what use
could one put to such a probe?
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1b
Re: What use for a 640 Ohm 1x Probe?
Mon Feb?18,?2013 8:43?pm (PST) . Posted by:
"Don Black" donblack1au
I think you are measuring the inner conductor resistance. This is made
of resistance wire (often wound in a spiral) to damp reflections back
the cable. The cable isn't terminated (the input impedance of the scope
is 1 Meg) and like any transmission line energy is reflected where it
isn't absorbed by matching termination. This is a compromise to damp
such reflections, useful at low frequencies.
Tektronix explains their techniques in their concept book series, the
one you want is called 'Oscilloscope Probe Circuits" . It's available to
download on the Internet and is an excellent guide to probe design.
Silicon Chip also has a good article on probes a while back that I think
explained it.
Don Black.
I'm wondering if it could be an RF probe. . com/rfprobe1. htm
> >
> > Another I have studied is an old Fairchild that is in good
condition that
> has a resistance of 640 ohms end to end on the center conductor.
To what use
> could one put to such a probe?
> >
>
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1c
Re: What use for a 640 Ohm 1x Probe?
Mon Feb?18,?2013 8:55?pm (PST) . Posted by:
"Philip" ndpmcintosh
Yeah. It doesn't have any markings on it other than the name "Fairchild&quo t; on the cable, and I am glad I checked it before I actually tried to test it.
In looking at an old but classic oscilloscope book it mentions a "direct" probe that has essentially 0 resistance used for checking low impedance, low frequency circuits. And, it also describes the "isolation&quo t; probe which has an R of 4.7 to 10kOhms. It might be something intended to serve as one of these.
It looks like it is from the early 60's and perhaps was used on the Fairchild 766H. I doubt there would be much current use for this probe.
Be careful with that!
Danger, 640 Ohms!
On 2/18/2013 5:50 PM, Alex wrote:
640 ohms ought to be enough for anyone.
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1d
Re: What use for a 640 Ohm 1x Probe?
Mon Feb?18,?2013 9:38?pm (PST) . Posted by:
"David" david_william_hess
I agree with what Don posted. The 640 ohms is just the resistance of
the inner conductor of the coaxial cable for a x1 oscilloscope probe.
I measured about 250 ohms on a x1 probe I happen to have in reach.
On Tue, 19 Feb 2013 04:55:41 -0000, "Philip" ndpmcintosh@ mac.com>
wrote:
Yeah. It doesn't have any markings on it other than the name "Fairchild&quo t; on the cable, and I am glad I checked it before I actually tried to test it.
In looking at an old but classic oscilloscope book it mentions a "direct" probe that has essentially 0 resistance used for checking low impedance, low frequency circuits. And, it also describes the "isolation&quo t; probe which has an R of 4.7 to 10kOhms. It might be something intended to serve as one of these.
It looks like it is from the early 60's and perhaps was used on the Fairchild 766H. I doubt there would be much current use for this probe.
Be careful with that!
Danger, 640 Ohms!
On 2/18/2013 5:50 PM, Alex wrote:
640 ohms ought to be enough for anyone.
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2a
Re: Tektronix 2465 capacitors etc.
Mon Feb?18,?2013 8:36?pm (PST) . Posted by:
"Chris" digitalinuxguy
John,
A HUGE thank you on checking that and giving me your value! I was hoping the short wasn't in the main board somewhere as that doesn't look like fun to pull in the least.
I just checked the resistance from the pin 7 (blue 87v wire) on the connector (power supply still out and on the bench) and I got a value of 25.55Kohm, so it would appear I should be OK to go at that (assuming that powering something else up on the main board doesn't cause it to short/overload the supply). I was testing the diodes on the power supply and diode CR1244 is giving me 0.538V forward and 0.630v reverse. I think I might pull it and check it out of the board later tonight after I eat etc.
Thanks for the help!
Chris
--- In TekScopes@yahoogrou ps.com, "John Snyder" wrote:
Chris
The problem could be in the 87V regulator
Or
Their could be a short/low Resistance some where in the load
I have a 2465B open and I measured a load resistance of 25.3K to ground on
Pin 7 of J121 (87V, the blue wire) with the power supply unplugged from the J121 connector
unit
John
-----Original Message-----
From: TekScopes@yahoogrou ps.com [mailto:TekScopes@yahoogrou ps.com] On Behalf
Of Chris
Sent: Sunday, February 17, 2013 5:40 PM
To: TekScopes@yahoogrou ps.com
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.
All voltages measured in the scope with everything hooked up. I just got
done checking the voltages pre-regulator.
At J233A I get:
pin 5 (87v unregulated) 97.6v
Pin 3 (42v unregulated) 49.0v
And at J234A I get:
pin 5 (15v unregulated) 18.94v
Pin 4 (5v unregulated) 6.64
Pin 2 (-5v unregulated) -6.92v
Pin 1 (-15v unregulated) -18.54v
Based on the unregulated values, I believe the issue must lie in the
regulator portions, and since I'm getting the 97.6v pre-regulated it would
seem to me the voltage doubler is working. I also double checked and
verified the 10v reference voltage at the test point on the main board as
well as the J121 connector that feeds the main board. (I figured this was
important to double check as the regulators all are based off the 10v
reference as I read it). Of course this is where I wish to learn more - I
understand what the individual components do but I still somewhat struggle
to see what the assembly as a whole is doing, which is why I'm trying to get
into all this, so maybe my understanding is skewed. :)
At any rate, it would seem to me that with the unregulated voltages where
they're at, that the issue would have to lie within the follow area:
ome.com/images/ /tek2465reg. jpg
Yes? No? I mean I have the correct voltages on the left side of those three
groups, and the wrong voltages on the right side, so it would seem that's
where I should look next?
Thanks for helping this newb out!
Chris
--- In TekScopes@yahoogrou ps.com, "Tom Miller" wrote:
The +87 is from a doubler and added to the +42. I would take a close look
at the three 10 uF caps and all the diodes in that area. Be sure to only use
fast diodes for any replacements.
Since you recapped this unit, don't overlook the fact that bad capacitors
can come from the factory new. Did you measure all these voltages in the
scope or on an external load?
Regards,
Tom
------------ --------- --------- ------
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2b
Re: Tektronix 2465 capacitors etc.
Mon Feb?18,?2013 11:49?pm (PST) . Posted by:
"John Snyder" ykochcal
Chris
The CR1244 is across the B-E junction of the transistor, so in circuit it
would not measure Open like a diode out of the circuit would.
I have my board out waiting for the inverter board to dry from it's
cleaning, and I measure .706V forward (of the diode) and .581V reverse
(instead of open, which is forward for the transistor junction.)
You could measure all the voltages Q1220, Q1221, Q1222, and Q1224 E,B and C
along with U1281A pin 1, 2 and 3 CR1220 anode to see what is out of wack
John
-----Original Message-----
From: TekScopes@yahoogrou ps.com [mailto:TekScopes@yahoogrou ps.com] On Behalf
Of Chris
Sent: Monday, February 18, 2013 8:37 PM
To: TekScopes@yahoogrou ps.com
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.
John,
A HUGE thank you on checking that and giving me your value! I was hoping
the short wasn't in the main board somewhere as that doesn't look like fun
to pull in the least.
I just checked the resistance from the pin 7 (blue 87v wire) on the
connector (power supply still out and on the bench) and I got a value of
25.55Kohm, so it would appear I should be OK to go at that (assuming that
powering something else up on the main board doesn't cause it to
short/overload the supply). I was testing the diodes on the power supply
and diode CR1244 is giving me 0.538V forward and 0.630v reverse. I think I
might pull it and check it out of the board later tonight after I eat etc.
Thanks for the help!
Chris
--- In TekScopes@yahoogrou ps.com, "John Snyder" wrote:
Chris
The problem could be in the 87V regulator
Or
Their could be a short/low Resistance some where in the load
I have a 2465B open and I measured a load resistance of 25.3K to ground on
Pin 7 of J121 (87V, the blue wire) with the power supply unplugged from
the J121 connector
unit
John
-----Original Message-----
From: TekScopes@yahoogrou ps.com [mailto:TekScopes@yahoogrou ps.com] On
Behalf
Of Chris
Sent: Sunday, February 17, 2013 5:40 PM
To: TekScopes@yahoogrou ps.com
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.
All voltages measured in the scope with everything hooked up. I just got
done checking the voltages pre-regulator.
At J233A I get:
pin 5 (87v unregulated) 97.6v
Pin 3 (42v unregulated) 49.0v
And at J234A I get:
pin 5 (15v unregulated) 18.94v
Pin 4 (5v unregulated) 6.64
Pin 2 (-5v unregulated) -6.92v
Pin 1 (-15v unregulated) -18.54v
Based on the unregulated values, I believe the issue must lie in the
regulator portions, and since I'm getting the 97.6v pre-regulated it would
seem to me the voltage doubler is working. I also double checked and
verified the 10v reference voltage at the test point on the main board as
well as the J121 connector that feeds the main board. (I figured this was
important to double check as the regulators all are based off the 10v
reference as I read it). Of course this is where I wish to learn more - I
understand what the individual components do but I still somewhat struggle
to see what the assembly as a whole is doing, which is why I'm trying to
get
into all this, so maybe my understanding is skewed. :)
At any rate, it would seem to me that with the unregulated voltages where
they're at, that the issue would have to lie within the follow area:
ome.com/images/ /tek2465reg. jpg
Yes? No? I mean I have the correct voltages on the left side of those
three
groups, and the wrong voltages on the right side, so it would seem that's
where I should look next?
Thanks for helping this newb out!
Chris
--- In TekScopes@yahoogrou ps.com, "Tom Miller" wrote:
The +87 is from a doubler and added to the +42. I would take a close
look
at the three 10 uF caps and all the diodes in that area. Be sure to only
use
fast diodes for any replacements.
Since you recapped this unit, don't overlook the fact that bad
capacitors
can come from the factory new. Did you measure all these voltages in the
scope or on an external load?
Regards,
Tom
------------ --------- --------- ------
Yahoo! Groups Links
------------ --------- --------- ------
Yahoo! Groups Links
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3a
DC504 counter display
Mon Feb?18,?2013 8:52?pm (PST) . Posted by:
"HankC" hankc918
Anyone familiar with the TM500 counter, model DC504 ?
I just picked one up & I noticed a couple of the digits are missing the middle horizontal segment.
So, it displays an "8" as a "0" , or a "0" as a "U" .
In your experience, is this a display problem or one of the chips driving the display ?
HankC
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3b
Re: DC504 counter display
Mon Feb?18,?2013 8:55?pm (PST) . Posted by:
"Chris van Lint"
More than likely the LED read outs.
Chris VK4CVL
At 03:52 PM 19/02/2013, you wrote:
Anyone familiar with the TM500 counter, model DC504 ?
I just picked one up & I noticed a couple of the
digits are missing the middle horizontal segment.
So, it displays an "8" as a "0" , or a "0" as a "U" .
In your experience, is this a display problem or
one of the chips driving the display ?
HankC
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3c
Re: DC504 counter display
Mon Feb?18,?2013 9:18?pm (PST) . Posted by:
"David" david_william_hess
Going by the schematic, the display digits are multiplexed which is
the common configuration so if the middle horizontal segment is
working on at least some digits, then the 7 segment display driver is
fine. If some segments of every 7 segment display work, then the
column display driver is fine as well.
That pretty much narrows any problem to bad display segments or
possibly an open connection to the missing display segments. I would
normally consider the later less likely than the former except that
two of the same segment are missing.
On Mon, 18 Feb 2013 20:52:57 -0800 (PST), HankC hankc918@yahoo. com>
wrote:
Anyone familiar with the TM500 counter, model DC504 ?
I just picked one up & I noticed a couple of the digits are missing the middle horizontal segment.
So, it displays an "8" as a "0" , or a "0" as a "U" .
In your experience, is this a display problem or one of the chips driving the display ?
HankC
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3d
Re: DC504 counter display
Mon Feb?18,?2013 9:48?pm (PST) . Posted by:
"taylorvandy" taylorvandy
--- In TekScopes@yahoogrou ps.com, HankC wrote:
Anyone familiar with the TM500 counter, model DC504 ?
I just picked one up & I noticed a couple of the digits are missing the middle horizontal segment.
So, it displays an "8" as a "0" , or a "0" as a "U" .
In your experience, is this a display problem or one of the chips driving the display ?
HankC
Common problem - FND357 displays go bad - fixed mine with two new LED displays. 6 bucks each, do a google search to see who might have them cheap.
Cheers,
Taylor
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3e
Re: DC504 counter display
Mon Feb?18,?2013 10:48?pm (PST) . Posted by:
"Miroslav Pokorni" mpokorni1
Tektronix had propensity to use chip IC sockets. Try to remove display
package and reseat it. That might re-establish pin connection. Sometimes
it takes several re-seatings to clear the socket.
Miroslav Pokorni
On 2/18/2013 9:18 PM, David wrote:
Going by the schematic, the display digits are multiplexed which is
the common configuration so if the middle horizontal segment is
working on at least some digits, then the 7 segment display driver is
fine. If some segments of every 7 segment display work, then the
column display driver is fine as well.
That pretty much narrows any problem to bad display segments or
possibly an open connection to the missing display segments. I would
normally consider the later less likely than the former except that
two of the same segment are missing.
On Mon, 18 Feb 2013 20:52:57 -0800 (PST), HankC hankc918@yahoo. com
wrote:
Anyone familiar with the TM500 counter, model DC504 ?
I just picked one up & I noticed a couple of the digits are missing
the middle horizontal segment.
So, it displays an "8" as a "0" , or a "0" as a "U" .
In your experience, is this a display problem or one of the chips
driving the display ?
HankC
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3f
Re: DC504 counter display
Mon Feb?18,?2013 11:17?pm (PST) . Posted by:
"Glenn Little WB4UIV" glittle_29445
If it displays a "8" as a "0" and a "0" as a "U" it is almost
certainly a driver issue.
If it were a bad display segment the "0" would display as a "0"
if the "8" displayed as a "0" .
Do all positions display the same incorrect digits?
73
Glenn
WB4UIV
At 11:52 PM 2/18/2013, you wrote:
Anyone familiar with the TM500 counter, model DC504 ?
I just picked one up & I noticed a couple of the digits are
missing the middle horizontal segment.
So, it displays an "8" as a "0" , or a "0" as a "U" .
In your experience, is this a display problem or one of the chips
driving the display ?
HankC
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4a
Manual / schematic for Leader 524S counter?
Mon Feb?18,?2013 9:46?pm (PST) . Posted by:
"Dave C" davec2468
Anybody have the user guide for this counter? (Leader user guides always include the schematic.)
Thanks,
Dave
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4b
Manual / schematic for Leader 524S counter?
Mon Feb?18,?2013 9:48?pm (PST) . Posted by:
"Dave C" davec2468
Um... that's a model 824S counter.
Dave
-=-=-=-
Anybody have the user guide for this counter? (Leader user guides always include the schematic.)
Thanks,
Dave
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5a
Tek 485
Mon Feb?18,?2013 11:12?pm (PST) . Posted by:
"John Polakowski" johnpolakow
I have two Tektronix scopes: a 485 and a 2465. Both of them need a little TLC, but I'm going to focus on the 485 at the moment as it is non-functional. I'm not an experienced electronics tech, but I'm not a complete novice either.
I really like the blue phosphor of the 485. For the moment the traces will show up, but the traces don't respond to input on either channel. I think the problem lies with the attenuator cards, but I'm not 100% sure thats the only problem. This I know for sure: if I take my signal gen and hook up its output to the place on the vertical amplifier where the attenuator plugs in, the signal is displayed on the scope. Another strange symptom is that on Channel 1, if the impedance is on the 50 Ohm setting, the trace is there, but on the 1 MegaOhm setting it disappears. Any thoughts guys? Have any experience with this sort of thing?
I've taken out the channel 1 attenuator and have it in my hands right now. Where should I start troubleshooting?
Thanks!
John
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