Date   

explosion mystery on my 7104

Sparky99
 

I powered by 7104 on this evening. After about 30 minutes I hear a loud squealing noise (imagine steam escaping from a boiling kettle) coming from the back of the instrument and immediately sensed a very intense burning / smoke smell - the kind I would usually associated with electrolytic caps that let go, but only seemingly stronger. My house RCD for the circuit the scope is on also tripped about the same time that I turned the scope off.
Fearing the worst I unplugged the scope, reset the RCD and took a look at the back - only to be met with a mystery. The cooling fin nearest the mains IEC connector was covered with a dark brown guey substance which had run down to the lower end of the fin. The other side of the IEC connector was blackened with dust and some goo. The IEC connector itself was oddly empty of any goo or particles, seemingly indicating that whatever caused the "explosion" was external to the inner part of the connector at least. The force of the explosion was such that the wall behind the scope was also covered with debris - small blackened parties and a light coating of dark brown residue. The mains fuse of the scope was intact.
The fuse, RCD and external nature of the guey and blackened areas all indicate that it was something external to the scope which caused the problem - but what? I have not tried powering the scope on yet, will wait until tomorrow for that - I am already in quite some trouble tonight with my wife :). Any thoughts on what might have caused the explosion? I considered insects, but the amount of goo suggest something unusually large, and also I don't understand how they could have caused current to flow between the live and earth conductors (thus tripping the RCD) as the IEC connector is reasonably well sealed when plugged in - especially from the kind of large bugs that would contain sufficient "goo". Has anyone got any ideas or theories on this?

Sparky 99


Re: 7104 versions, and vertical amplifier issue

 

On Thu, Jun 17, 2021 at 10:46 PM, Jim Adney wrote:


Peter A. Keller
Yes, of course, Peter Keller, not Paul…

Raymond


Re: 7104 versions, and vertical amplifier issue

Jim Adney
 

On Thu, Jun 17, 2021 at 11:10 AM, Raymond Domp Frank wrote:

Do you mean Paul Keller's book? That excellent book was "merely" distributed
by Dennis a few months ago. It was a monumental effort nevertheless and very
worthwhile for those who ordered one.
I just checked my original copy, bought from Deane Kidd a couple decades ago.
"THE CATHODE-RAY TUBE, Technology, History, and Applications"
by Peter A. Keller
ISBN: 0-9631599-0-3


Re: 7104 versions, and vertical amplifier issue

 

There was a French variant of the 7104 that had approx. 2-3GHz BW. It was discussed here some years back - search the archive.

David

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Raymond Domp Frank
Sent: 17 June 2021 17:11
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7104 versions, and vertical amplifier issue

Hi Jon,

On Thu, Jun 17, 2021 at 05:59 PM, Jean-Paul wrote:


These are some faint memories, I have yet to research this connexion, but I am
certain our TEK veterans will be able to fill in the history.
ISTR that earlier attempts to get more info from within the group didn't yield much.

One source is the excellent CRT book that Dennis reprinted.
Do you mean Paul Keller's book? That excellent book was "merely" distributed by Dennis a few months ago. It was a monumental effort nevertheless and very worthwhile for those who ordered one.

Raymond


Jon

PS: spoke to our friend Japp. Hope to visit next Autumn.
I'm sure you'll enjoy visiting Jaap.


Re: SG 502 Assistance?

Tom Lee
 

I’d start by looking at the actual waveform. The specific way in which it distorts will be a useful clue.

Cheers
Tom

Sent from my iThing, so please forgive brevity and typos

On Jun 14, 2021, at 22:01, sweetbeats <torridheatstudios@gmail.com> wrote:

Greetings everybody.

Hope this is an okay place to post this. I’m a member of the TM 500 group as well and will redirect this to there if advised.

I’ve been a member for some years but really essentially lurk as time to tinker with my audio and Tek gear is in limited to non-existent supply.

But the time has come to try and get my stuff working. I have a modest TM 500 setup…mainly using two TM 504 frames loaded with:

SC 502 (needs work…have a couple parts units)
DM 501A (dead…doesn’t appear to power up)
PS 503A (works!)
FG 502 (unknown commodity just yet)
AA 501A (seems to work!)
SG 502 (this seems to work too…more below)

I have additional modules, DC 504 (unknown commodity), an additional PS 503A, PS 501-1, DD 501, and too many mainframes…need to get rid of some…RTM 506, two spare TM 504, and two TM 503.

I want to use my TM 500 gear primarily to maintain/repair analog audio equipment.

Okay.

That’s the rundown.

So I’m working on the SG 502. It cleaned up nice, the frequency range buttons are a bit sticky, but the AA 501A says it is producing <0.004% THD from about 9Hz to 108kHz. Nice! The interesting thing is once you go outside of that range, like almost immediately, the distortion goes up considerably. Like…50% THD and higher. Are there any usual suspects I should address as a given with my SG 502 before doing anything else, or outside of that does anybody have any suggestions for a next step to helping it perform within spec across it’s designed frequency range (5Hz to 500kHz)?

Thanks!

Cory Oace





Re: SG 502 Assistance?

Jean-Paul
 

We can see the rated THD with all filters on and at max output of the pair ~ 0.0018%

Look at the residual output signal to see the distortion plus noise content

Jon


Re: 7104 versions, and vertical amplifier issue

 

Hi Jon,

On Thu, Jun 17, 2021 at 05:59 PM, Jean-Paul wrote:


These are some faint memories, I have yet to research this connexion, but I am
certain our TEK veterans will be able to fill in the history.
ISTR that earlier attempts to get more info from within the group didn't yield much.

One source is the excellent CRT book that Dennis reprinted.
Do you mean Paul Keller's book? That excellent book was "merely" distributed by Dennis a few months ago. It was a monumental effort nevertheless and very worthwhile for those who ordered one.

Raymond


Jon

PS: spoke to our friend Japp. Hope to visit next Autumn.
I'm sure you'll enjoy visiting Jaap.


Re: SG 502 Assistance?

Jean-Paul
 

Check AA501 and SG502 specs, % THD varies with filters setting.

Jon


Re: 7104 versions, and vertical amplifier issue

Jean-Paul
 

Raymond: Memories are from 1967 but 7104 was in 1978..1979.

So I did see many TEKs at the Labs but those were NOT 7104.

Still i am certain the original 7104 requirement was for the Agencies.

https://w140.com/tekwiki/images/3/30/Tekscope_1979_V11_N1.pdf

Jon


Re: 7104 versions, and vertical amplifier issue

Jean-Paul
 

Raymond,

These are some faint memories, I have yet to research this connexion, but I am certain our TEK veterans will be able to fill in the history.

One source is the excellent CRT book that Dennis reprinted.

Jon

PS: spoke to our friend Japp. Hope to visit next Autumn.


SG 502 Assistance?

sweetbeats
 

Greetings everybody.

Hope this is an okay place to post this. I’m a member of the TM 500 group as well and will redirect this to there if advised.

I’ve been a member for some years but really essentially lurk as time to tinker with my audio and Tek gear is in limited to non-existent supply.

But the time has come to try and get my stuff working. I have a modest TM 500 setup…mainly using two TM 504 frames loaded with:

SC 502 (needs work…have a couple parts units)
DM 501A (dead…doesn’t appear to power up)
PS 503A (works!)
FG 502 (unknown commodity just yet)
AA 501A (seems to work!)
SG 502 (this seems to work too…more below)

I have additional modules, DC 504 (unknown commodity), an additional PS 503A, PS 501-1, DD 501, and too many mainframes…need to get rid of some…RTM 506, two spare TM 504, and two TM 503.

I want to use my TM 500 gear primarily to maintain/repair analog audio equipment.

Okay.

That’s the rundown.

So I’m working on the SG 502. It cleaned up nice, the frequency range buttons are a bit sticky, but the AA 501A says it is producing <0.004% THD from about 9Hz to 108kHz. Nice! The interesting thing is once you go outside of that range, like almost immediately, the distortion goes up considerably. Like…50% THD and higher. Are there any usual suspects I should address as a given with my SG 502 before doing anything else, or outside of that does anybody have any suggestions for a next step to helping it perform within spec across it’s designed frequency range (5Hz to 500kHz)?

Thanks!

Cory Oace


Re: Type 284

Simon Tregear
 

Chris,

Simon here again.

What is the status of the 7CT1N ?

What model is the DIF probe. ?

And would you ship either to VIC.

Thanks, S

On 17 Jun 2021, at 10:35 am, Chris van Lint <chrisvanlint@bigpond.com> wrote:

I have a taker here in Melbourne Australia for the type 284 PG. Thank you to those who have responded. I do have some smaller items, which could be shipped at a reasonable price. Stuff like a differential probe, a P6230, P6046, P6156, 7S12 with a S-6 and S-52, transistor mounts (013-072/013-069/013-0098-02), a 067-0503-00 Precision DC Divider, a 7T11 pcboard with the reed relays still intact (sorry no TD), a 7CT1N, a 10MHz TCXO and the pre-scaler for the DC508 etc.

Contact me off-line.

Chris


Re: 7104 versions, and vertical amplifier issue

 

On Thu, Jun 17, 2021 at 05:12 PM, Jean-Paul wrote:


A few memories from LBL and LLNL ~ 1960s. (yes I am OLD!)

The original 7104 client was at Defense Nuclear Agency/ Atomic Energy
Commission.

Only after some years was 7104 released for general sales.
Hi Jon,
Do you have any more information on this?

Raymond


Re: 7104 versions, and vertical amplifier issue

Jean-Paul
 

Chris: A few memories from LBL and LLNL ~ 1960s. (yes I am OLD!)

The original 7104 client was at Defense Nuclear Agency/ Atomic Energy Commission.

The "shots' at the Nevada and Pacific test ranges, cost 10s of M$ and months to setup.

Many fast sensors arrayed around the device Ground Zero or surface zero. .

Long buried coax from Shot Cab to Instrument Hut. Imagine dozens of scopes, shock rack mounted set for single trigger.

A neuc or thermonuc detonation is on a nS scale, with exponential decay of temperature, pressure etc. LLNL or Los Alamos was in charge of the shots and often EGG did the instrumentation.

Each 7104 had a scope camera, to record on film.

Only after some years was 7104 released for general sales.

From an optimist in the Nuclear Age...

Jon


Re: 7104 versions, and vertical amplifier issue

cmjones01
 

An update: I love this scope. I'm a thousand miles away from my usual
lab at the moment, and had to solve a problem for a client. This
required measuring the length of a particular state on a 600MHz clock
signal which occurs once, at startup, after a FPGA programming phase
which takes several seconds. Usually I'd just reach for the digital
scope, but all I have here is the 7104. Seeing the 600MHz clock is, of
course, no sweat for it. But the MCP really comes in to its own when
looking for a one-shot event. Set the trigger, select single-sweep
mode, crank up the intensity, start up my circuit and bingo - clear as
day, there's the pulse on the screen. All 14 microseconds of it.
Plenty clear enough to see and measure in normal room light.

Amazing stuff.
Chris

On Wed, Jun 16, 2021 at 9:31 PM Chris Jones <chris@stumpie.com> wrote:

Good news: the scope now works. I cleaned and reseated the Y output hypcon U862 a couple of times but nothing changed. Then I cleaned and reseated the driver U842 and, for good measure, swapped its elastomer and plastic frame with U862. Now I have full vertical sweep, and a usable scope.

There are lots of niggles remaining: both 7A29s have attenuator contact problems (the attenuation factors are randomly wrong) as well as an odd effect rounding the end of the leading edge of the calibrator waveform, which I suspect is due to the feed-beside adjustments. The 7B15 is reluctant to trigger and the plug-in connectors have various intermittent issues, as I'd expect on a scope which has been stored for a while.

Chris

On Wed, 16 Jun 2021, 16:57 Mark Vincent, <orangeglowaudio@gmail.com> wrote:

Chris,

The Hypcons are sensitive to being clean and the contacts being aligned right. You should remove each and clean the contacts on the chip and connector. Also do this to the other ICs and transistors. The square mounting frames for the Hypcons should be put on with an even pressure on all sides. The screws are tightened to snug in opposite corners at a time as the lug nuts on the wheel of a vehicle. I did add good heatsink compound to the Hypcons and the heatsinks. Roger is right about making sure the coax connectors are also cleaned. It is possible the neck pins have oxidation on them. Check the voltage at the input of the vertical if cleaning does not fix the problem. It is possible the problem is earlier. One dirty contact somewhere can cause headaches in finding it. Many here will agree to this having seen it enough times.

IF yours looses sync in the readout, the 741 IC under the handle on the horiz. board towards the rear will be bad. I had this happen in mine. It will occur when it warms a little. This happened in mine after a minute with the left side off. The trace will remain normal. This information is only in case this happens to yours or anyone else's.

Jon is right about keeping the intensity low. When I use mine, the intensity is enough to see the line and readout. When a trace is on the screen, I turn the intensities up a little. The intensities I keep it at are so that it is barely visible until I raise it enough to see a trace and readout which is still low. The yellow LED will not come on the way I keep the two set. It may be easier to use a lamp on the circuit while keeping the screen in a low light level to ensure the trace seen is safe for the MCP.

Mark





Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

Federico, perhaps easier to do is a continuity test between R701 pin 5 and U781/6, with your DMM at resistance measurement. One lead fixed to that pin 5. The other, extended with a length of insulated wire and blank tip, probing/touching the pins of U781. It doesn't harm when you touch the wrong pin.
Albert


Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

On Thu, Jun 17, 2021 at 09:34 AM, Pitpat wrote:

Hi, i didn't understood that pin 6 was still to be tested, i thought that the
one i got from pin 5 of the weighted resistor was sufficient.
It's just to verify that that there is no interruption between that pin 5 and U781/6.
IIRC you had a contradictory situation where that pin 5 was well negative (<< -0.27 V) while U781/1 was -8.6 V.
Anyway, today i fiddled a bit with a hook tipe probe around pin 6, could it be
-0,27v ? it seems not to change with all the slower sweep settings.
That must have been U781/7. But nevertheless good to know that the non-inverting input is ok.
I've also noticed that sometimes when the time base knob is rotated fast
enough for just a fraction of a second the correct readout appears and then it
switch back to the unknown, that means that the MUX should be fine right?
Could perhaps be mechanical stress on some board when you rotate the time/div knob?

Albert


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

Hi, i didn't understood that pin 6 was still to be tested, i thought that the one i got from pin 5 of the weighted resistor was sufficient.
Anyway, today i fiddled a bit with a hook tipe probe around pin 6, could it be -0,27v ? it seems not to change with all the slower sweep settings.
I've also noticed that sometimes when the time base knob is rotated fast enough for just a fraction of a second the correct readout appears and then it switch back to the unknown, that means that the MUX should be fine right?


Re: 7104 versions, and vertical amplifier issue

cmjones01
 

On Wed, Jun 16, 2021 at 11:33 PM Raymond Domp Frank <hewpatek@gmail.com> wrote:

On Thu, Jun 17, 2021 at 12:06 AM, cheater cheater wrote:

The Soviets had 3GHz direct display scopes.
AFAIK, the 7104 was (claimed to be) the only general-purpose, commercially available plugin 'scope with a bandwidth of 1 GHz.
I also have an interest in Soviet scopes, and own a couple of their
7000-series-inspired models plus many of the plugins (always looking
to complete the set!). What I find striking is just how common Tek's
products are in the "west" versus how uncommon their Soviet
equivalents are in their part of the world. I've spent quite a while
trawling the Russian-speaking internet looking for accessories for my
Soviet scopes, and there's simply not all that much out there. I think
they were built in relatively small numbers and, because of the course
of history since then, many have been scrapped. Indeed, search for any
Soviet equipment part number and most of the links will be for sites
advertising its precious metal content and offering to scrap it.

In contrast, even something as exotic as the 7104 isn't at all rare,
even though it was originally incredibly expensive and purchased only
by well-funded laboratories and government contractors. Even today, 40
years after its introduction, anyone who wants one can probably find
one, and they're not even expensive. I paid £150 (less than $200) for
mine in the UK including the full set of "correct" plugins, and all
that was needed to get it going was a dose of contact cleaner. That
means that this extreme high-end technology is available to small
businesses like mine, amateurs and experimenters. It strikes me as a
curious consequence of the cold war's technology race.

Chris


Re: 7104 versions, and vertical amplifier issue

Jean-Paul
 

Bonjour, I am unaware of any French scopes with 1 GHz BW,

CRT scopes I have seen here in France were 100 MHz or less.

RE Russian scopes, most of their electronics in were heavy copies of US models.

до свидания
do svidaniya

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