Date   
Re: 465 No Horizontal Sweep

david
 

Cap C1220 is wet Tantalum, all caps in 465 are tantalum except for Filter Caps in power supply section. I replaced C1220 with a Aluminum electrolytic, and all is working correctly. Also replaced R1220 which was burned black. All voltage readings in Horizontal Amp section correct except for Collector of Transistor Q1226. Measures -0.36v, should be -0.45v ,20% low, I believe the -0.45v is the forward voltage of Diode CR1253, but scope is working well so I am not concerned. If it's not broke don't fix it.

Re: 7A15A issue or limitation??

Chuck Harris
 

Simple explanation, I think:

"Vertical mode" triggering is only valid when there is
a single vertical signal displayed on the screen, or you
are in ALT (alternate) mode.

It gets more complicated if I try to tell you why:

The only modes where the traces on the screen are exactly
what they appear is when there is only a single channel
displayed on the screen.

Whenever there is more than one channel on the screen,
there is some form of eye trickery going on. This is
because there is only a single beam in the CRT to draw on
the screen. A couple of scope models have multiple beams,
but they are the exception, rather than the rule...

In ALT (alternate) mode, it may appear to the eye that
there are two signals on the screen at the same time, but
in reality, the two signals are being shown singly,
alternating: A, B, A, B... If the sweep time is fast enough,
the eye merges the alternating images so they appear to the
brain to be simultaneous.

At the slower sweeps, the eye can easily see the traces
alternate.

In CHOP (chopped) mode, it may appear to the eye that there
are two signals on the screen at the same time, but in
reality, the two signals are chopped up into alternating
tidbits.... a tidbit of A, a tidbit of B, a tidbit of A, a
tidbit of B...all the while the sweep marches on, making a
sort of square wave with the tops being the tidbits of one
channel, and the bottoms being the tidbits of the other
channel.

Because the chopping of the A and B signals is faster than
the sweep speed, and with no time relationship to the sweep
speed, or the signals, the eye sees the chopped up signal to
have merged into what looks like simultaneous display.

But the trigger isn't a human eye, so it isn't fooled by this
trickery.

When the trigger mode is in "Vertical", the trigger is given
the exact signal the plugin is trying to display on the
screen: Single channel mode, gives the single channel.
Alternate mode, gives an alternation of Channel A and Channel B.
Chop mode gives a composite signal of a little bit of A, B,
and their vertical positions... A real dog's breakfast.

"Vertical mode" triggering is only valid when there is a
single vertical signal displayed on the screen, or you
in ALT (alternate) mode.

-Chuck Harris

tinkera123 wrote:

Hi,

I have been playing around with my 7A15A's, in different 7603 Mainframes, and have a 'jittering' or 'flickering' of the 4V Calibration signal.
The 'jittering' is a movement, always to the left, of the trace along the horizontal axis and return to the correct position.

I can define this issue or limitation as follows:-
Independent of Mainframe - 2 x 7603's used
Independent of Timebases - 7B53 and 7B92A used
Only occurs in TRIG SOURCE/VERT MODE with VERT MODE/ALT - both traces are stable in all other Modes
Only one of the traces becomes unstable
Only occurs when traces from each Vert Amp are 'un-overlapped' - when the two traces are overlapped, both traces are stable

The Manual states that in TRIG SOURCE/VERT MODE .... "each sweep is triggered by the signal being displayed on the CRT"

This suggests to me that when I dive into the Circuit Descriptions, that I should be looking for some 'switching mechanism' which is swapping the Triggering mechanism between the signals from each Vert Amp.
If this 'switching mechanism' is faulty or receiving a weak signal, then this maybe causing poor triggering, hence the 'jittering'.
However, this 'switching' between Vert Amp signals would occur in the Timebase or Mainframe.
But that doesn't make sense because the 'jittering' occurs in both 7A15A's, independently (ie. 7A15A + 7A26 + 7B92A etc), and in 2 different Mainframes, and with different Timebases.
So .... where have I gone wrong here???? ..... or is this a limitation of the 7A15A???

Any guidance is appreciated.



Re: Tek 3c66 Carrier Amplifier Bridge plug-in for the Tek 560 series scope

Tim Phillips
 

From Tim P (UK)
As you may have gathered from the manual, the 3C66, and 'big brother' Type
Q are very specialised plug-ins.
The only use is with transducers like pressure sensors and foil strain
ga(u)ges.
I have one in a 564 with a Statham pressure transducer and a
pneumotachometer, but TBH it lacks sensitivity here.
I have also seen a 564 storage 'scope with two 3C66s in X/Y configuration
for displaying stress / strain curves.
It's a 'fun' thing if you have the transducers, and probably useful for
teaching about certain engineering concepts, but yes, it's a
'one-trick-pony'
Tim

On Mon, 25 Nov 2019 at 20:07, garp66 <@garp66> wrote:

hi,

Has anyone had experience with the Tek 3c66 Carrier Amplifier Bridge
plug-in for the 560 scope ?

It appears to amplify signals from variable impedance transducers &
sensors, such as strain gauges, according to the TekWiki
reference: http://w140.com/tekwiki/wiki/3C66

Are there any other interesting uses for it ?
Can this 3c66 plug-in be modified or harvested for other use ?

thank you,
rick




Re: Yet another 7L5 issue (7L5 / 7854) below 10 kHz

Nenad Filipovic
 

Hi Cliff,

I wrote about a related problem in this message:
https://groups.io/g/TekScopes/message/149400
I also have the same issues with my 7L5/7854 as you reported (improper
reset and CF display below 10kHz), and my conclusion is that 7854 readout
processing does not conform to specification, so it's the 7854 firmware
issue. I summarized a part of it in the conversion document posted here:
https://groups.io/g/TekScopes/message/150089

So until someone dares to do brain surgery on 7854 ROMs, I doubt there's
much we can do. Tek did not touch it back in '82, so I figure it wasn't an
easy fix.
These recent microfiche scanning operations might reveal some project
documentation on 7854 firmware, though I'd be amazed if somebody fixed a 30
year old bug :) 7854 is still hard to beat even today.

Best Regards,
Nenad Filipovic

Early 515a schematic?

Jamie
 

Hello,

I have an early production 515a, which uses some 6U8s and 6BQ7s. At serial number 4804, Tek introduced a bunch of tweaks including replacing them with 6DJ8s. My paper manual's circuit diagrams depict the newer design, with the old components in red. I've come across a couple of mistakes in the red annotations, and also wonder if the voltage values are correct for the older design. Some of the old circuitry is omitted entirely in the new circuit diagram, for instance where in the calibrator a single 6AU6 pentode replaced the original 6U8 triode-pentode, but as far as I can tell, doesn't show the function of the 6U8's triode section.

I've searched without success for a PDF of the original 515 or pre-4804 515a schematics, without success. Do you have a 515 or early production 515a manual or PDF showing *only* the old circuits?

7A15A issue or limitation??

tinkera123
 

Hi,

I have been playing around with my 7A15A's, in different 7603 Mainframes, and have a 'jittering' or 'flickering' of the 4V Calibration signal.
The 'jittering' is a movement, always to the left, of the trace along the horizontal axis and return to the correct position.

I can define this issue or limitation as follows:-
Independent of Mainframe - 2 x 7603's used
Independent of Timebases - 7B53 and 7B92A used
Only occurs in TRIG SOURCE/VERT MODE with VERT MODE/ALT - both traces are stable in all other Modes
Only one of the traces becomes unstable
Only occurs when traces from each Vert Amp are 'un-overlapped' - when the two traces are overlapped, both traces are stable

The Manual states that in TRIG SOURCE/VERT MODE .... "each sweep is triggered by the signal being displayed on the CRT"

This suggests to me that when I dive into the Circuit Descriptions, that I should be looking for some 'switching mechanism' which is swapping the Triggering mechanism between the signals from each Vert Amp.
If this 'switching mechanism' is faulty or receiving a weak signal, then this maybe causing poor triggering, hence the 'jittering'.
However, this 'switching' between Vert Amp signals would occur in the Timebase or Mainframe.
But that doesn't make sense because the 'jittering' occurs in both 7A15A's, independently (ie. 7A15A + 7A26 + 7B92A etc), and in 2 different Mainframes, and with different Timebases.
So .... where have I gone wrong here???? ..... or is this a limitation of the 7A15A???

Any guidance is appreciated.




--
Cheers,
Ian,
Melbourne, Australia

Re: Trying to save a 576

 

Hi Ryan,
That was a very generous offer.
Hi to Kim!
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Ryan Scott via Groups.Io
Sent: Saturday, December 07, 2019 12:13 PM
Subject: Re: [TekScopes] Trying to save a 576

Hello, I have a 154-0563-05 CRT which came from the estate of a Tek collector. I don't have a 576 so it's of no use to me. You can have it for the cost of shipping from 97229 and take the gamble as it's in unknown condition. Regards, Ryan Scott

On Saturday, December 7, 2019, 09:49:50 AM PST, Bob Koller via Groups.Io <testtech=yahoo.com@groups.io> wrote:

Dennis, no other instrument used the 154-0563-xx CRT, unfortunately.




--
Dennis Tillman W7PF
TekScopes Moderator

Re: 7L5 dot frequency reset bug - any clues or a fix?

Dave Casey
 

I can test mine out tomorrow and let you know if it does the same thing.

Dave Casey

On Sat, Dec 7, 2019 at 4:46 PM Cliff Carrie <cliffcarrie@...> wrote:

The 7L5 manuals say the Dot Frequency should reset to 0.000 kHz at power
on. There have been previous posts about this not happening, but no mention
of a fix. I have personally seen two 7L5s, including the one I am currently
using in my 7854, that reset to a varying frequency near 3778 kHz. I have
forced a reset using a jumper to trigger the power-on reset timer. The Dot
Frequency goes to 0.000 kHz during the reset but goes back to 3778.xxx kHz
when the reset timer ends. All other modes and indicators reset as
expected. I don't think this is unique to the 7854 power on since the
mainframe was already powered up before I did my test. I suspect a timing
race in U830 as the reset pulse turns off. I know this is a minor
annoyance, but the circuitry is there, and I'd like to make it work
properly. My 7L5 service manual is 070-2184-01. The reset timer is Q621 on
Drawing 5 lower left. U830 is on Drawing 8 (see pins 4 and 17).

1: Has anyone experienced this on the 7L5 in a mainframe other than the
7854?
2: Who else is experiencing this in a 7854?
3: Does anyone have a fix?

Cliff Carrie



Yet another 7L5 issue (7L5 / 7854) below 10 kHz

Cliff Carrie
 

The dot frequency displays with the decimal point in the wrong place below 10 kHz (Fine mode on); the displayed number must be multiplied by 10. The 7L5 tunes correctly to 9.750 kHz, for example, but displays 0.975 kHz
Tek documented this in Service TekNotes in November of 1982. Strangely, they never produced or published a fix as far as I can discover. Does anyone have a solution, or ideas for one?

Cliff Carrie.

Re: 577 D1 function won't turn off

Mlynch001
 

Great information. Thanks for the update.
--
Michael Lynch
Dardanelle, AR

Re: 577 D1 function won't turn off

DW
 

I would like to make a correction it is NON storr that I adjusted not SENS COR

It is on the D1 storage board you will notice 4 blue dials grouped closely together, the second one over to the right, NON STORE is what resolved my problem

Re: 577 D1 function won't turn off

DW
 

I have an update

I performed the 370V calibration on TP 2 to ground from the D1 storage board. I was about 365 so i put it right at 370

I took pictures of the adjustments on the D1 board and very carefully moved each one slightly back and forth and noted the display.

I fixed my problem by carefully turning down SENS COR from the 3 o'clock position to near the 12 o'clock position, the ghosting problem disappeared and the D1 storage appears to work correctly and turn off when I don't want it. I turned off the instrument and back on, a brief flash of the screen but the display came on free of storage display artifacts

All the other settings are default except 370V and SENS COR

Hopefully this might help anyone out by trying this, maybe reply with your results to see if this is my particular case or perhaps it is a fix hopefully for some people

Re: 577 AC collector supply not reading zero on display

DW
 

Reading the manual I notice the following for the collector supply

120 Volts is fed to T101 autotransformer (Variable collector)

K125 turns T101 on or off

The wiper of T101 goes to what appears to be a filter L101 R101 and C101, and then it goes to the primary of T102

From T102 it appears this is where I get 6.5 25 100 400 and 1600V from for the collector

For 6.5 to 100V rectifier CR107 is used and above that CR103-106 is used

Since different rectifiers are used at higher volts I decided to test my problem at higher voltages, the problem appears to get much worse

At 1600V 8kOhms 5V Division 0 collector volts the line is 4 divisions across which should be 20V, not good

The collector supply appears somewhat simple if i look at certain sections of it. I feel like I simply have a T101 autotransformer issue. The wiper is making contact to the very edge but yet it acts like i have it turned up partially. Maybe a issue with T101 or maybe K125 or perhaps C101 is bad? I feel this problem is occurring at the beginning of the collector supply stage.

Re: Trying to save a 576

Mlynch001
 

I have a very early and a very late model 576. The CRT in the later one is an -05 at the end of the part number. The early one is a -00 or -01 if Memory serves me. The older one suffers from a bad HV transformer, which I am currently trying to get a replacement for.

--
Michael Lynch
Dardanelle, AR

Re: Trying to save a 576

Eric
 

On Sat, Dec 7, 2019 at 12:37 PM, Ed Breya wrote:


One more thing - it's possible that the intensity and focus pot string
resistors have drifted way out of spec. Depending on the circuit and drift
direction, you may not have enough range for intensity setting all the way up.
You'd have to study the circuit and make some measurements (they're elevated
to near cathode voltage).

Ed
CRT voltages tested at the neck pins.

1) -3815 Vdc
2) -3841 Vdc
3) -3840 Vdc
4) -2667 Vdc
5) NC
6) NC
7) 100 Vdc
8) 100 Vdc
9) 100 Vdc
10) 109 Vdc
11) 52 Vdc
12) NC
13) -3814 Vdc
14) - 3814 Vdc


Heater voltage ping 1-14) 5.9Vac

7L5 dot frequency reset bug - any clues or a fix?

Cliff Carrie
 

The 7L5 manuals say the Dot Frequency should reset to 0.000 kHz at power on. There have been previous posts about this not happening, but no mention of a fix. I have personally seen two 7L5s, including the one I am currently using in my 7854, that reset to a varying frequency near 3778 kHz. I have forced a reset using a jumper to trigger the power-on reset timer. The Dot Frequency goes to 0.000 kHz during the reset but goes back to 3778.xxx kHz when the reset timer ends. All other modes and indicators reset as expected. I don't think this is unique to the 7854 power on since the mainframe was already powered up before I did my test. I suspect a timing race in U830 as the reset pulse turns off. I know this is a minor annoyance, but the circuitry is there, and I'd like to make it work properly. My 7L5 service manual is 070-2184-01. The reset timer is Q621 on Drawing 5 lower left. U830 is on Drawing 8 (see pins 4 and 17).

1: Has anyone experienced this on the 7L5 in a mainframe other than the 7854?
2: Who else is experiencing this in a 7854?
3: Does anyone have a fix?

Cliff Carrie

Re: Trying to save a 576

Bob Koller
 

Eric,

Too bad the tube is weak, but very typical, I probably at least a dozen bad 576 tubes up in the loft, that I can't quite bring myself to toss.
You have the later HV transformer, so no worries there.
As for the dash number on the CRT, don't worry about that, all are usable, install any CRT that works!

Re: Trying to save a 576

Eric
 

Ryan, I would defiantly be interested in that especially if it has been in a box. The 05 is currently what is in there at the moment.

Re: Trying to save a 576

Eric
 

Bob you hit the behavior exactly square on the head. 0-75% intensity control the trace brightens then dims and brighten again and at full intensity it loses all resemblance of focus. So I think this tube is toast. Also this tube has a weird model number it is a 154-0563-05 I cant seem to find any reference to a tube version higher then 2. The High voltage transformer is the black silicone one.

Re: Trying to save a 576

Dave Voorhis
 

On 7 Dec 2019, at 21:18, Tam Hanna <tamhan@...> wrote:

on the risk of sounding like a broken record: please hang onto the DANAHER 576, 577 and 575 instruments with damaged screens.
Why do you call them _Danaher_ 576, 577, etc.?

I thought Tek wasn’t acquired by Danaher until 2007. Tek was still under independent ownership at the time the 575, 576, and 577 were made, wasn’t it?

If you’re naming it by current ownership, then wouldn’t it be more correct to call it Fortive?

Ownership often doesn’t reflect branding, anyway. E.g., a Vauxhall Corsa or Chevrolet Corvette is a Vauxhall Corsa or Chevrolet Corvette, not a General Motors Company Corsa or General Motors Company Corvette.

Or am I missing something here?