Date   

TEKTRONIX 260-1421-00 Switch, Beam Finder

piercec99@...
 

Hello everyone, I'm not sure if I am posting this in the right place. If I am in the wrong place please correct me. But I need a beam Finder switch for a 2445 scope the part number is TEKTRONIX " 260-1421-00 " I think any beam finder switch for any 2400 scope would work. Please someone Email me at piercec99@... or message me here. Thank you all !!!


Re: Test 04 Fail 02

Christoph
 

I turned to a new attempt repeating the CAL cycles to get rid of that
Test 04 fail 02 condition when powering up the scope.

Just went through CAL01 and still have this error. Do I have to go through all the cycles in ordered sequence or may I possibly skip one cycle and enter one that is more likely responsible for the fail condition?

Maybe I should mention that I obtained a preprogrammed Dallas NVRAM chip from that greek firm (QService) which contains calibration data for a 2465B (mine is a 2445B).

Not that some preprogrammed data now conflicts with my entered data so far.

I also have an empty "new" empty Dallas DS1225. Should I rather start with that to rule out any conflict with pre-existing data?

--
Christoph


Re: 7603 weirdo inverted Z axis

 

There are some ways you can narrow down the problem before tracing the
z-axis control circuits:

1. Does the readout intensity control also operate backwards?

Its signal goes directly to the readout board which then drives the
input to the z-axis amplifier in parallel with the normal intensity
signal so it bypasses all of the z-axis logic.

2. Plug-ins can also adjust the beam intensity. If you have a 7B92A
timebase, what does its intensity control do?

3. Is the leading edge unblanking working correctly when a fast pulse
edge is observed?

I checked my 7603 and with a 7B53A timebase, about 1/2 division at 50
ns/div (25 nanoseconds) is unblanked before a fast pulse edge. With a
faster timebase like a 7B92A, 1 full division at 50 ns/div (50
nanoseconds) is unblanked before a fast pulse edge. Oddly enough a
7B50A also unblanked 50 nanoseconds before the fast pulse edge so I
assume it shares more in common with the faster timebases than the
7B53A.

As far as tracing the circuit, the z-axis amplifier is straightforward
but the z-axis logic shown on schematic 2 gives me a headache. I will
have to break out Clipboard CAD to figure out exactly what is suppose
to be happening there. I do see one thing however:

The sweep gate rises at the base of U99B to redirect the current from
the intensity control through the emitter of U99B to the collector.
The intensity is controlled by this current. If the -15 volt
connection to the intensity potentiometer is open, then the current
would *increase* as it is turned counterclockwise lowering the
resistance between the wiper and ground reversing its operation. The
intensity control range would also be affected but this might not be
very noticeable if the grid bias was adjusted.

So instead of checking to see if the intensity potentiometer is
connected backwards, check to see if the -15 volt supply is present at
the intensity potentiometer and that the wiper actually moves between
0 and -15 volts as the control is turned through its full travel
range. Note that -15 volts is suppose to produce the highest
intensity and 0 volts is suppose to produce the lowest intensity.

On Fri, 22 Jan 2016 20:18:20 +0100, you wrote:

Among other issues with this 7603 were the Z axis operation, it seemed
like a blanking issue (beam is not blanked correctly), but on closer
inspection it is a bit more involved:

The intensity control works reversed (fully CCW is maximum intens, fully
CW blanks the beam). This is not a cabling issue.

Blanking signals are correctly processed by the Z axis logic, and the Z
axis amplifier produces the correct voltages on pin B (about 20 V with
P1171 open for a blanked beam, and about 90 V with maximum input current
for maximum intensity). I also cross checked this against a working 7623
just to be sure that I analyzed the circuitry correctly and understood
the circuit description.

So the inversion must happen somewhere else. I previously replaced all
HV caps in the HV unit, including the DC restorers. Now I also replaced
all diodes in the grid DC bias restorer. No change in behaviour.

The focus amplifier, preset and front panel control all work correctly.

I don't know what else I could check or what else could cause this.
Maybe someone here has another idea?

Cheers,
Marian


Re: Tek 555 service manual.

zerousair
 

Thanks for your time, wolf.


Re: Tek 555 service manual.

n4mf_sc
 

Or just a Digital Camera, and then to software.

Mitch
N4MF


Re: Tek 555 service manual.

Malcolm Hunter
 

For the odd schematic, a decent camera phone can serve extremely well
instead of scanning.

Malcolm


On 23 January 2016 02:18:50 "Tothwolf tothwolf@... [TekScopes]"
<TekScopes@...> wrote:

On Fri, 22 Jan 2016, lbfulton@... [TekScopes] wrote:

Those are the same manual I already have, John. I've been told there is
a much larger Tek manual for troubleshooting/repair down to component
level for the 555. If it does exist that's the one I'm looking for.
There are a number of different manuals for the 555. Becky at manualsplus
sent me an entire collection of 555 manuals shortly before they shut down.
I'll have a look this weekend to see exactly which P/Ns I have (I do know
they have schematics) but I won't be able to scan them right now as I do
not own a suitable scanner.


Re: Tek 555 service manual.

Tothwolf
 

On Fri, 22 Jan 2016, lbfulton@... [TekScopes] wrote:

Those are the same manual I already have, John. I've been told there is a much larger Tek manual for troubleshooting/repair down to component level for the 555. If it does exist that's the one I'm looking for.
There are a number of different manuals for the 555. Becky at manualsplus sent me an entire collection of 555 manuals shortly before they shut down. I'll have a look this weekend to see exactly which P/Ns I have (I do know they have schematics) but I won't be able to scan them right now as I do not own a suitable scanner.


Re: Tektronix 2445B help

 

Based on the dates, the 2465B may be very similar if not mostly
identical.

On 22 Jan 2016 16:06:09 -0800, you wrote:

I have a 2445B that stopped working and need a set of shematics, I have the 2445 service manual but it is very different and the only 2445B manual I could find on line does not have the schematics section. Can anybody help? Thank you.
Albert


Re: Tektronix 2445B help

ArtekManuals
 

Albert

We have it including the separate Options service manual

http://artekmanuals.com/manuals/tektronix-manuals/

Enter 2445B in the searcxh box

Not free but not insulting either, high quality scans

Dave
ArtekManuals.com

On 1/22/2016 7:06 PM, aprat@... [TekScopes] wrote:

I have a 2445B that stopped working and need a set of shematics, I
have the 2445 service manual but it is very different and the only
2445B manual I could find on line does not have the schematics
section. Can anybody help? Thank you.
Albert



[Non-text portions of this message have been removed]


--
Dave
Manuals@...
www.ArtekManuals.com


Tektronix 2445B help

Albert Prat
 

I have a 2445B that stopped working and need a set of shematics, I have the 2445 service manual but it is very different and the only 2445B manual I could find on line does not have the schematics section. Can anybody help? Thank you.
Albert


Tektronix 555 problem

zerousair
 

The upper beam on this scope will only sweep unless set to trigger from the lower beam time base. I can only get a dot with the upper beam set to the (A) upper time base. Both time bases are set the same for recurrent. I have tested all the upper time base tubes and all good. The supply voltages checked as per the Tek schem. for the time base seem to be fine. There is a "sawtooth out" jack on the front of the upper time base and from what I'm seeing using the working trace, there is no sawtooth waveform there. I only have this scope to check that with. Before I dig into it further, thought I'd ask you fellows here if you've had any experience with this. Been many years since I've worked electronic problems. I do have a time base extender. Thank for any time and advice.

Garrett


Re: 7603 weirdo inverted Z axis

Albert Otten
 

Hi Marian, do I understand you correctly if I think that the Z amplifier itself is working correctly but that the CRT gets brighter when the Z output at B gets lower (less positive)? In that case I have no idea what's going on, but then you should also "complain" that the Readout is shown as negative image.
If the Readout is correct then the logic board is suspect, for instance a faulty U99.

Albert


Re: 7603 weirdo inverted Z axis

Marian B
 

The Z axis amplifier is kinda an op amp in the sense that it is a global feedback amplifier. It does work correctly, both with manually provided inputs and when connected to the Z axis logic.

The intensity pot isn't hooked up backwards.

In the mean time I also checked whether all connections between the tube socket and the pin header in the HV unit are correct, but, unfortunately, they all are correct.

Another possibility is that someone inadvertently changed the circuit during
troubleshooting.
This seems most likely at this point, however there are very few spots in the scope that have been reworked before. Some are on the HV unit (the transformer and the thick film network where exchanged or reworked), but not in that area. I also can't see any changes in parts, except that some European parts have been used in non-critical parts of the circuit (e.g. BZX series Zeners instead of whatever Tek Beaverton specified, I guess this is normal for a Heerenveen-built scope).

I should try to probe the grid and cathode voltages again and see if this is really an issue with the HV unit. Maybe it works correctly after all and there is some strange fault in the tube itself? --- I'd prefer a fault in the HV unit, though.


Re: Tek 555 service manual.

zerousair
 

Those are the same manual I already have, John. I've been told there is a much larger Tek manual for troubleshooting/repair down to component level for the 555. If it does exist that's the one I'm looking for.


Garrett


Re: TDS544A status

 

Hi Ed,
Understod. Anyway, the LCDs I use is about $75 and I get 'em from China (Ebay). It takes a bit of shlocking, but the price is right.

Jay


Re: 7603 weirdo inverted Z axis

Ed Breya
 

One more thing - another failure type can happen with certain opamps, where output phase reversal occurs if an input is driven beyond its normal dynamic range. I don't recall how the intensity signals are processed in the 7K scopes, but if opamps are involved, check for proper operating conditions on all pins.


Ed


Re: 7603 weirdo inverted Z axis

Ed Breya
 

Unless the pot is hooked up backwards, the only way I can see that a signal can be improperly inverted is in an inverting gain stage that is damaged so that the input signal passes right through without inversion. This can happen in a common-emitter or opamp stage, where a failure or a missing part allows the signal to pass through the feedback loop rather than the active device.


Another possibility is that someone inadvertently changed the circuit during troubleshooting.


Ed


7603 weirdo inverted Z axis

Marian B
 

Among other issues with this 7603 were the Z axis operation, it seemed
like a blanking issue (beam is not blanked correctly), but on closer
inspection it is a bit more involved:

The intensity control works reversed (fully CCW is maximum intens, fully
CW blanks the beam). This is not a cabling issue.

Blanking signals are correctly processed by the Z axis logic, and the Z
axis amplifier produces the correct voltages on pin B (about 20 V with
P1171 open for a blanked beam, and about 90 V with maximum input current
for maximum intensity). I also cross checked this against a working 7623
just to be sure that I analyzed the circuitry correctly and understood
the circuit description.

So the inversion must happen somewhere else. I previously replaced all
HV caps in the HV unit, including the DC restorers. Now I also replaced
all diodes in the grid DC bias restorer. No change in behaviour.

The focus amplifier, preset and front panel control all work correctly.

I don't know what else I could check or what else could cause this.
Maybe someone here has another idea?

Cheers,
Marian


Re: TDS754A printer compatibiliy

Ed Breya
 

Thanks guys, for help with printers. I have several models of Brother laser printers - these are my favorites - I've standardized on them years ago after much disappointment with ink jets and the big brands. The problem with newer printers is that the Centronix port has pretty much disappeared in favor of Ethernet and wireless. I'll have to look at all of them and see what they have for ports and compatibility. I don't want to buy a printer just to go with the scopes - I was hoping to take one out of retirement/spare status and have it work, but maybe it just won't happen.


Ed


Re: TDS544A status

Ed Breya
 

Thanks Jay,
It's good to know these are available, but I'd be reluctant to get a new HVPS since the CRT isn't too good anyway. I can't look at it anymore now, but I recall that when it went through all the weird patterns at POST, there was one that lit the whole screen, and it clearly has some phosphor burn of various lines where the traces sat for long times.


I'd be more inclined to go with an LCD panel upgrade, but it probably isn't worth it on this scope. On the 754A it probably would be, if its display craps out.


Ed