7104 Oszilloskop

Shows the fast rise output of a PG506, with a 7A29 amplifier in a 7104 mainframe, extra readout information comes from a 7M13 unit. Photo taken with a Olympus E-510 four-thirds digital camera with 35mm macro lenses.

Die micro channel plate Röhre hat den Vorteil, das sie seltene erscheinende Signale noch mit voller Helligkeit darstellen kann. Fast alle anderen Oszilloskope mit Standard CRT zeigen bei einigen besonderen Signalformen gar nichts mehr, während das 7104 diese Signale noch fangen kann. Gerade im Hochgeschwindkeitsbereich von Digitalsignalen können damit z.B. Trigger Ausreißer dargestellt werden, oder selten auftretende Formen von Jitter, Implusen usw. - siehe Kataloge -. Diese Röhre hat nur eine Größe von 0.8cm/DIV im GEgensatz zu den üblichen größeren 1cm/DIV Röhren.

The micro channel plate has not only the advantage under low repetitve signals, the beam can focused also very sharp, see the sharp readout numbers, that's brilliant. This CRT has only a 0,8cm/DIV dimension, not the widely used bigger 1cm/DIV CRT.

Ein deratiger Helligkeitsvorteil hat auch seine Nachteile:

die 7104 Röhre muss sehr pfleglich behandelt werden, die Strahlenergie kann bei diesem Röhrentyp sehr schnell permanente Einbrennspuren verursachen. Um den Benutzer auf einen zu hell eingestellten Strahl hinzuweisen hat der Hersteller neben der CRT eine gelbe Leuchtdiode platziert, die anfängt zu leuchten als Hinweis bitte die Strahlstärke zu reduzieren, wird dies ignoriert erfolgt nach ca. 20 Minuten eine automatische Abschaltung. Die Leuchtdiode ist zweistufig, fängt sie an zu blinken soll möglichst sofort die Strahlstärke reduziert werden, ansonsten erfolgt die automatische Abschaltung sehr bald.

Man soll nicht der Auffassung sein durch diesen optischen Warnhinweis in Verbindung mit der automatischen Abschaltung sei die Röhre sicher gegen Einbrennen, das ist sie nicht. Ich möchte es nicht probieren, aber bei voll aufgedrehter Helligkeit und passenden Signalen können sicherlich wenige Sekunden ausreichend sein um Einbrennspuren zu verursachen. Anderseits muss das Gerät kurz die Möglichkeit geben die Strahlstärke voll auszunutzen um gerade seltene Ereignisse im Signal darstellen zu können. Ein ganz einfacher Vergleich, sehr leistungsstarke Fahrzeuge lassen dem Benutzer auch die Möglichkeit die Leistung vollends auszunutzen ohne ihn zu beschränken, wer da nicht bedacht und erfahren an die Sache geht kann die Folgen erahnen, bei diesem sehr leistungsstarkem Oszilloskop ist das genauso.

The yellow LED warns the user about a too high CRT intensitiy, after 20 minutes the instrument shuts down. If the LED blinks you should reduce CRT intensity soon as possible, after some minutes the instrument shuts down. The LED remind the user not to set intensity too high - beam energy burn-in phosphor. This micro-channel CRT is very sensitive, use it with care. I don't want to test it, but I think some seconds under full intensity combined with suitable signals burn-in the CRT already. It's a very powerful instrument, but like a muscle car it needs a good user.

Searching for burn-in marks:

Beam settings in the photo above:

reduce room light to a lower level
reduce beam intensity to a minimum
set the vertical amplifier offset so that the beam leaves the CRT viewable range (on the photo beam hidden below the bottom horizontal grid line)
increase the intensity very slowy that the beam starts illuminating the screen by reflected diffusion light

Photo with burn-in marks in a used 7104:

On top and bottom there are the readout marks.
On the vertical 4.th division there is a clearly visible straight line, the beam stands often there.
On 2.nd and 3.rd vertical division beam stands there also many times.
On vertical divisions > 4, beam stands there seldom.

Fortunately there are no big marks or signal curves from misuse, thank you former user my dear. These marks are typical for a normal operating history and they are not visible under normal operating settings, on the areas with burn-in marks MCP sensitivity is reduced.

My recommendations:

use the 7104 not for daily use, take better a 7904A, 7904, 7844 or 7704A. Use the 7104 working with important applications, excepted new unknown signals, fast signals, troubleshooting in high speed circuits, expecting low repetitive signals mixed with standard repetitive signals or just when you feel like using it for fun.
use the readout in this CRT in a less intensified position, reduce it always to a minimum viewable level or switch it off for continous operation.
reduce the room light to a minimum level, allows a reduced CRT intensity. Of course this CRT has the power for operating excellent under day-light, but why forcing the instrument showing it's full power?
use a viewing-hood and reduce intensity
don't give any stupid engineer or any other children a chance working with this instrument. In my life I've seen many engineers using scopes like a TV, operating powered ON for hours, sometimes powered over the weekend - unused - many times with a high intensity. Give these people onetimes a 7104 in their hands - they will burn-in a trace in the CRT for sure. They are the same people who are careless with probes, mostly the ones with high salaries and good skills in talking and rhetoric, later they will say: "it wasn't me".

Another example how a burn-in mark in a CRT looks (7834):

This is a CRT photo from my 7834 storage oscilloscope operating in the "Bistable Mode". Shown there is a waveform of a Type 109 Pulse Generator. In the background you see a triangle waveform and some horizontal lines, burn-in traces, they disappear anymore. It seems there was too much intensity and beam energy on the CRT, I don't know under which intensity the trace stands and for how long. Fortunately that's the only operating mode showing marks, other modes don't show.

Third shown 7104 on this website:

I've got another 7104 in working condition, "buy as is", I'm a lucky guy receiving an 7104 in an almost perfect optical condition, manufactoring year appoximately 1984.

Z-axis amplifier before cleaning, dust near the high voltage parts.

After removing the amplifier and cleaning the cabinet.

Cleaned amplifier and fan

Cleaned High Voltage Compartment

Cleaned High Voltage Cable and Anode Connector

Please follow the "Caution" instruction on the sticker when removing the high voltage connector and discharge the anode lead on chassis ground first. Don't hold the charged anode connector near any electronic part, an unwanted spark can destroy parts.

Cleaned Instrument.

Be carefull when cleaning the delicate amplifiers, especially the flexible PCB and wires near the deflection plates can break easily. Take also care for a protection against ESD (Electro Static Discharge), in general low capacitance high speed parts are very sensitive.

General ESD recommondations when cleaning instruments:	Reason:
Follow standard ESD protection rules (grounded mates, strap, ESD floors, e.c.t.)	Save ESD protection
If standard ESD protections rules are not applicable follow steps below:
clean the instrument being barefooted on a natural unsealed wooden, stone or concrete floor. (Of course never clean under powered AC-line).	Less human body charge due walking
Choose damp cotton cleaning rags, not dry synthetics	Avoid easy chargeable materials, important because they are in direct contact with the IC pins
Avoid any highly isolating materials near the open instrument (plastic, glass, Teflon, plastic tapes and bags e.t.c)	Avoid easy chargeable materials
Don't walk fast - walk slowly	Less human body charge due walking, less charge due slower material separation (shoes-floor)
Don't stand up from your chair when touching the instrument	Avoid human body charge due material seperation (trouser-chair)
Don't use pointed metal objects like screwdrivers or pincettes for cleaning	Similar to an lightning arrester, increase electric field strength
Never do it on a day with low air humidity (at least 40-50% relative humidity [under room temperature])	Important - dry air increase dramatically chargeable voltages

Cleaned Tube Section

Cleaned Readout Section with a lot of ASIC's.

Cleaned Front PCB Section

Cleaned Front Panel

Some minor scratches only, photo flash intensifies them, not visible under ambient light. Removing all the calibration stickers was a terrible job and took a lot of time, always being careful not destroying the surface.

Cleaned Mainframe

Color still powerful and bright, minor scratches in the surface only. Coaxial connectors still unoxidized and clean. A carrying handle like new. Unfortunately the instrument has no options, but this doesn't matter for almost all applications. If you can buy a working 7104 in such a condition, don't hesitate to buy and don't care for your money, this "Peak of Analog Scope Technology" will never come back.

Fourth shown 7104 on this website:

I've got another 7104 in working condition, "buy as is", again I'm a lucky guy receiving an 7104 in an almost perfect optical condition. This time in a seldom full options version ! I've searched a long time for it.

- after unpacking, condition like always: hundred of calibration and property stickers, dusty covers and dirty knobs. -

Receiving some packets on the same day. This 7104 was ordered overseas, transport costs were higher than the price for the device. Many electronics don't see the real value of such an excellent first class analoge scope, they prefer to pay more money for other (better known) lower performance second hand scopes and leave such beauties in the shops for me - thank you -
Some weeks ago a dealer in Germany offered three devices for a reasonable cheap price, I bought one of them (my third one), his second one took many weeks before somebody bought it, the third one was still available lastly. I can really smile, young chick say sometimes: "this 7000 series is too big for my table and the weight too much", later they tell: "I've bought a 100 MHz two channel service scope" (for nearly the same price). Some young electronics have to learn a lot.

with Option 2 and 3, X-Y phase corrected horizontal amplifier and improved EMC cover - this type is the peak of analog oscilloscope development

Last calibration in the 90ties from the manufactorer, somebody put a photo on the cover. I removed the calibration sticker for an inside inspection check before first time power on. Always check the correct wired AC voltage before power first time. The surface is still in excellent condition, only dust.

This was a eight division bandwidth test with a 1 GHz signal? - if so, it would be a perfect response. I haven't confirmed.

7104 Oscilloscope

First shown 7104 on this website:

Second shown 7104 on this website:

Screenshot:

Ein deratiger Helligkeitsvorteil hat auch seine Nachteile:

Searching for burn-in marks:

Another example how a burn-in mark in a CRT looks (7834):

Third shown 7104 on this website:

Fourth shown 7104 on this website: