Date   
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

Re: Tek 555 service manual.

John Clark
 

There appear to be a few on eBay. Most are listed as service manuals even though they say "instruction manual" on the front. However, looking at listing pictures item 271658505408 looks like the same version that's available on the Tek wiki site that has full diagrams, parts lists, and theory of operation. $26 and free shipping seems reasonable.

John
To: TekScopes@...
From: TekScopes@...
Date: Fri, 22 Jan 2016 08:25:33 -0800
Subject: [TekScopes] Tek 555 service manual.


























Was wondering if anyone here had a factory service manual for a 555 scope. I have the instruction manual already. Thanks for any time and help.








Garrett










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

Re: Tek 555 service manual.

ArtekManuals
 

Garrett

IF the manual you have has a part number on the title page in the lower
left hand corner which is 070-165
Then that is the factory Service manual ( actually it is a combined
Operator & service manual ) IF your INSTRUCTION copy has the part number
above on it but has no schematics then your copy is incomplete ...

WE have a COMPLETE copy of that manual for download but I think it is
likely there are free copies available on the WEB


Dave
ArtekManuals.com




On 1/22/2016 11:25 AM, lbfulton@... [TekScopes] wrote:

Was wondering if anyone here had a factory service manual for a 555
scope. I have the instruction manual already. Thanks for any time and
help.


Garrett



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

Garre

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

Tek 555 service manual.

zerousair
 

Was wondering if anyone here had a factory service manual for a 555 scope. I have the instruction manual already. Thanks for any time and help.


Garrett

Re: TDS754A printer compatibiliy

Vince Vielhaber
 

I don't know if this helps at all, but the 2040 is a PCL-5e printer.

Vince.

On Thu, January 21, 2016 11:14 pm, edbreya@... [TekScopes] wrote:
Thanks Al,


I tried the laserjet and almost every other one too, but it didn't work
with the Brother HL-2040. I'm wondering if maybe the printer's
communication and format settings can be changed via a PC hooked up to
it. I don't recall ever seeing any explicit provision for that in
printers, since the drivers usually take care of all the details.


Ed





--
Michigan VHF Corp. http://www.nobucks.net/ http://www.CDupe.com/
http://www.foggymist.com The Foggy Mist Emporium

Re: TDS544A status

Siggi
 

My TDS784D does this as well. I recapped the CRT driver board, which
alleviated this for a spell. I was in email contact with another TDS owner
who found that in his case it was due to degradation of the connections to
the horizontal deflection coil. Apparently there's reasonable peak currents
there and the connector is not so hot.
Once I get through the pile of HP gear hogging my bench ATM, I'll give the
connections a look-see and a good clean, as this random, flickering
shearing is a little annoying.

On Thu, Jan 21, 2016 at 23:04 edbreya@... [TekScopes] <
TekScopes@...> wrote:



Now I'm getting paranoid - I just remembered that lately the 754A display
sometimes has slight flickering in the display shortly after power-up, and
then would be OK after warming up a bit. I hope this is not a sign of
impending doom like a flaw in the HV transformer that gets worse as
happened in the 544A. I'm thinking about maybe opening it up to see if
there's any evidence of HV leakage on the outside of the transformer.



Ed





Re: TDS544A status

 

Hi Ed,

I have a number of those HV assemblies lying around from doing conversions to LCDs
They were converted as the CRTs were too dim for resale. I've been slowly unloading them on Ebay, but they're not hot sellers by any means. You can see one of them in Ebay item 321799417496
http://www.ebay.com/itm/Tektronix-TDS784C-HV-CRT-board-for-TDS700-600-and-500-series-oscilloscopes-/321799417496?ssPageName=STRK:MESE:IT http://www.ebay.com/itm/Tektronix-TDS784C-HV-CRT-board-for-TDS700-600-and-500-series-oscilloscopes-/321799417496?ssPageName=STRK:MESE:IT
If you're in the US, I'll send one to you for $75 including shipping.

Jay

Re: TDS544A status

stefan_trethan
 

It can never hurt to open it up and have a look.
Except in those cases where you damage something in the process of course. ;-)

Even if there is nothing to be found at the very least it will give
you some idea what to expect when things do go wrong.

ST


On Fri, Jan 22, 2016 at 5:04 AM, edbreya@... [TekScopes]
<TekScopes@...> wrote:
Now I'm getting paranoid - I just remembered that lately the 754A display sometimes has slight flickering in the display shortly after power-up, and then would be OK after warming up a bit. I hope this is not a sign of impending doom like a flaw in the HV transformer that gets worse as happened in the 544A. I'm thinking about maybe opening it up to see if there's any evidence of HV leakage on the outside of the transformer.


Ed



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



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Posted by: edbreya@...
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Yahoo Groups Links


Re: TDS754A printer compatibiliy

Tothwolf
 

On Thu, 21 Jan 2016, edbreya@... [TekScopes] wrote:

I tried the laserjet and almost every other one too, but it didn't work with the Brother HL-2040. I'm wondering if maybe the printer's communication and format settings can be changed via a PC hooked up to it. I don't recall ever seeing any explicit provision for that in printers, since the drivers usually take care of all the details.
According to the user manual, it looks like the HL-2040 only supports GDI. The 2070N supports PCL, Epson FX-850 and IBM Proprinter XL emulation. See pages 2-1, 2-17, A-2 and A-3

https://www.brother-usa.com/ModelDocuments/Consumer/Users%20Manual/UM_HL_2040_2070N_EN_1289.PDF

Re: TDS754A printer compatibiliy

Tothwolf
 

On Thu, 21 Jan 2016, edbreya@... [TekScopes] wrote:

I tried the laserjet and almost every other one too, but it didn't work with the Brother HL-2040. I'm wondering if maybe the printer's communication and format settings can be changed via a PC hooked up to it. I don't recall ever seeing any explicit provision for that in printers, since the drivers usually take care of all the details.
I'm not sure if this will help, but I have a HL-2070N which is the same basic printer as the HL-2040 but it also has a network interface. The default mode for the 2070N is the Epson FX-850 but it can be switched to the IBM Proprinter XL via its built-in webserver based configuration page.

If you happen to need it sometime, I have the service manual for these printers in pdf format. I don't remember where I got it from but Brother doesn't seem to make it publicly available.

Also, if you ever begin to have trouble with the printer not feeding paper, pick up a LM6291001 paper feeding kit (mine was ~$15 from a printer supply company). The feed roller assembly in these printers seems to last for about 20k-25k pages after which the textured roller surface is worn too much to reliably pull paper from the paper tray. Installing the roller requires quite a bit of disassembly (and you have to carefully align the marks on the gears while installing it), but following the diagrams in the service manual makes it pretty easy.

If you have trouble with double-feeds, there is a small rubber dampening pad for the feed solenoid that breaks down and turns into a sticky tar-like goo. Removing it solves the problem, although after removing it, you can definitely hear an audible click when the solenoid pulls in.

Re: TDS754A printer compatibiliy

Ed Breya
 

Thanks Al,


I tried the laserjet and almost every other one too, but it didn't work with the Brother HL-2040. I'm wondering if maybe the printer's communication and format settings can be changed via a PC hooked up to it. I don't recall ever seeing any explicit provision for that in printers, since the drivers usually take care of all the details.


Ed

Re: TDS544A status

Ed Breya
 

Now I'm getting paranoid - I just remembered that lately the 754A display sometimes has slight flickering in the display shortly after power-up, and then would be OK after warming up a bit. I hope this is not a sign of impending doom like a flaw in the HV transformer that gets worse as happened in the 544A. I'm thinking about maybe opening it up to see if there's any evidence of HV leakage on the outside of the transformer.


Ed

Re: TDS754A printer compatibiliy

allanjamison
 

Ed:

I have a TDS 544A and it has a centronics parallel port. I have used it with several printers that use the standard HP PCL language. Set the printer options to output to the centronics port and select the laserjet format.

It should work. The PCL format uses ASCII characters and it a very common standard in the older, more expensive printers, from many vendors. Many current printers also support PCL but you have to check the specifications. Very inexpensive printers now do most of the formatting in the PC and require proprietary drivers.

I hope this information helps. I am assuming the your TDS 754A has similar options.

In my TDS 544A there is also a floppy disk that you can use to save standard image formats. These formats can be processed by most PC drawing and word processing programs. That is another way to get a screen print into a document or print it out.

Al Jamison

Re: 7603 Strange HV Need Help

Ed Breya
 

Yes, the sockets can cause much more grief in terms of diagnosis and repair. I was thinking more in terms of frequency of occurrence - I've seen way more stories about bad caps, although perhaps sockets actually are the cause of more trouble than is attributed to them.


Ed

Re: 7603 Strange HV Need Help

 

I would actually rank the TI sockets as a larger problem than tantalum
capacitors. The capacitors unambiguously fail and are relatively easy
to find and replace. The sockets become intermittent with no visible
sign and replacing them is a much more involved procedure.

On 21 Jan 2016 14:21:24 -0800, you wrote:

The problems with TI sockets and ICs with silver plated leads are well known, and have been discussed here a number of times over the years. Unfortunately, Tek used a helluva lot of them in many of our favorite instruments from that era. I believe they are one of the main causes of problems - especially strange and intermittent ones. I'd rank the TI problem well below the usual bad Ta caps and worn out Al caps, but it's up there somewhere near the top of the list.

Ed

Re: 7603 Strange HV Need Help

 

I have never encountered this problem with silver or these TI ICs of
which I have lots but I have with thick gold. I assume the leads are
FeNi42 which was a common lead frame material in the past and whatever
process which is needed to plate silver to FeNi42 was lacking.

Maybe silver sulphide which is that black tarnish you find on silver
can form between the lead frame material and the silver isolating it.

On 21 Jan 2016 15:42:36 -0800, you wrote:

In a nutshell, there is something seriously galvanically and/or metallurgically wrong with those TI IC leads with Ag plating. Over time, and depending on the environment, the bond between the Ag plating and whatever is underneath disintegrates, literally disconnecting the outside surface from the leadframe material, causing loss of contact. I have even seen this in leads that were soldered to the board clean through.

Ed

Re: 7603 Strange HV Need Help

Ed Breya
 

In a nutshell, there is something seriously galvanically and/or metallurgically wrong with those TI IC leads with Ag plating. Over time, and depending on the environment, the bond between the Ag plating and whatever is underneath disintegrates, literally disconnecting the outside surface from the leadframe material, causing loss of contact. I have even seen this in leads that were soldered to the board clean through.


Ed