开云体育

Thanks for the valuable suggestions.

I've checked both Q1030, Q1036 and they seemed to be ok, then swapped Q1030 and Q1090, no difference, then swapped Q1036 and Q1096, no difference.

And then I've found that I can get a trace if I connect the probe to the calibrator, select trig mode to normal and adjust a 'level' pot _very_ accurate. Tiny movement to the right or left and the trace disappears.
So I can get the trace in norm mode, I just can't get a free running sweep.

This leads me to think that maybe this thing is not broken after all? Maybe it's just miscalibrated to death?
I have not calibrated it for five or six years and I doubt that the previous owner had.

Maybe I should try to calibrate it first.

Serge

I think "graticule" is a better term than "grid" here, to avoid confusion
with the grids of the electron gun structure.

On Mon, Dec 15, 2014 at 6:41 PM, roy.thistle@... [TekScopes] <
TekScopes@...> wrote:

Hi:
I bought a 7603 frame. It works (displays signals); but I removed the
bezel...and the CRT is cracked around the edges down to the grid.


I assume that the grid is bonded to the face of the crt, and there is a
thicker plate of glass that is bonded to the crt, above that. I think the
thicker glass must of shattered; but the crt is still good. I mean vacuum
or no vacuum...and it works so vacuum.


Does anyone know of, or can think of a way of repairing this (some kind of
windshield acrylic, or superglue?)


Also, I am very leery of operating it, because it could possibly implode!
Or, is this not so much a danger.
Best wishes all.

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

For giggles I popped the cover on my 2465. I have the -6 ROMs, but sadly I have no means to read them out. I tried flipping the CAL jumper, no change on the OSD. The DIAG jumper is also not it.

John,

I never did get your off list email.


Dave

Low ESR aluminum electrolytics (not polymer aluminum electrolytics) of from 2 to
4 times the capacitance will have an equivalent ESR except at higher frequencies
and this is what I normally use if a replacement tantalum is not available. The
capacitance is not as important as the ESR and high frequency performance so
quadrupling it will not cause any problems.

If high frequency performance is an issue, then I would include a parallel film
or ceramic capacitor of 1/10th or less of the value. Determining if this is
necessary may be difficult so I sometimes measure the peak to peak ripple with
and without the film or ceramic capacitor and if it does not make a significant
difference, I leave it out.

Hey Panos,

sorry, I can't help you with the ROM contents.


Is there some particular reason why you suspect the ROMs? They're checksummed and covered by power on self-checks.
See page 6-13: "Checksum - A sixteen bit, spiral-add checksum is calculated and compared to a two-byte value stored in ROM being checked."
Not that they couldn't possibly fail such that the checksum is defeated, but the odds seem low (1/65535 or so per ROM).



Do these dots follow the A5 board - e.g. have you tested both pairings of A5/readout boards?
This sure seems like a weird hardware failure if it's on the A5 board, rather than the readout board, as the characters are written serially to the readout board. I can't imagine a hardware failure mode that'd compromise only some addresses in the character RAM on a serial bus. Almost has to be software or else the readout board (or something really stupid like PSU ripple/bypassing).
Note that according to the service manual, "The lower 64 address locations in RAM each correspond to a specific readout location on the crt.", so it seems bytes 32-63 only are not managing to display "space"..


Are you perhaps thinking that this version of the ROMs simply behaves this (odd) way? Is this perhaps as inane as the A5 board indicating that the CAL/NO CAL jumper is in the CAL position?



Siggi

I agree you should to all of them and the A31 rectifier/filter as well. Low esr aluminum are fine.

Jerry Massengale

Dan,

I got your probe in and it works fine. I am guessing it is a 100mhz probe. If you want it I can send it to you. I paid $36.95 including shipping. If not I will be very happy to keep it. Sorry I butted in. I realized later that you may have wanted it.

Jerry Massengale

Please have anyone these roms available? I speak for TEK 2465 firmware version 6.

On 12/15/2014 3:06 PM, 'Dennis Tillman' dennis@... [TekScopes]
wrote:

Huntron Trackers are a joke (pardon my bluntness).
I am astounded that they can charge so much for something that does so
little.
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Sunday, December 14, 2014 5:35 PM
To: TekScopes@...
Subject: Re: [TekScopes] 7704A -just a quickie

<snip>
This may be contentious: I've acquired a couple of Huntron Trackers
(1000 &
2000) that were thrown in with a couple of scopes some time ago. I've
never
seen them mentioned here and would be interested to read any opinions on
their efficacy.
I used the Huntron 2000 for the continuity tests. I liked the
indication of
whether the circuit being tested appears to be totally resistive or if
some
other function is going on. I'm certainly not suggesting I possess any
expertise in its use.
All supply paths tested looked purely resistive, as expected.

------------------------------------
Posted by: Keith Smith <kahsmith@...>
------------------------------------

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

I have to wholeheartedly agree, nothing more than a small filament
transformer and a resistor! Dennis the box and connectors are obviously
very expensive. (Sarcasm off.)
Mike

PS: If I did replace C2087 and C2083, I'm guessing I should just do all of
them.
I see the 8.2?F are not so easy to get in Tantalum. Would Low ESR Aluminum
be a satisfactory substitute?
Thanks
k

On Mon, Dec 15, 2014 at 2:03 PM, Keith Smith <kahsmith@...> wrote:

Thanks, Dennis. Heh, it does seem like something that would encourage
strong opinions :)
(Bluntness is appreciated.)
What you say figures, given how glad folks are to get rid of them!
Interesting toy for a noob like me, though.

Jerry, I guess I'm going to need some resistors over a 1/2w ;)
I found the famous message# 84399 and need some time to digest the whole
conversation that went with it. I can see a shopping list coming out of it
if this goes the way I fear it will..
Very nice looking dummy load, Jerry!

BTW, I lifted 1 leg of C81 to 89 caps.
ESR by scope & FG at 200kHz and ?F by Fluke
C2081 0.8Ω 109?F
C2083 1.2 Ω 97.7?F
C2085 0.8 Ω 111?F
C2087 2.08 Ω 8.7?F
C2089 0.8Ω 9.23?F

Thanks all!
Keith



On Mon, Dec 15, 2014 at 1:06 PM, 'Dennis Tillman' dennis@...
[TekScopes] <TekScopes@...> wrote:

Huntron Trackers are a joke (pardon my bluntness).
I am astounded that they can charge so much for something that does so
little.
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Sunday, December 14, 2014 5:35 PM
To: TekScopes@...
Subject: Re: [TekScopes] 7704A -just a quickie

<snip>
This may be contentious: I've acquired a couple of Huntron Trackers (1000
&
2000) that were thrown in with a couple of scopes some time ago. I've
never
seen them mentioned here and would be interested to read any opinions on
their efficacy.
I used the Huntron 2000 for the continuity tests. I liked the indication
of
whether the circuit being tested appears to be totally resistive or if
some
other function is going on. I'm certainly not suggesting I possess any
expertise in its use.
All supply paths tested looked purely resistive, as expected.

------------------------------------
Posted by: Keith Smith <kahsmith@...>
------------------------------------

--
Keith Smith - KeithSmith.ca_Freelance Guitarist & Location Recording
Service <>

--
Keith Smith - KeithSmith.ca_Freelance Guitarist & Location Recording Service
<>


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

Well thanks for all the help. I was able to obtain the 7177 style board and it fixed it. So the second model was either incompatible or bad. I'm sending it back to the seller...

Thanks, that's exactly what I was looking for.

Andy

Thanks, Dennis. Heh, it does seem like something that would encourage
strong opinions :)
(Bluntness is appreciated.)
What you say figures, given how glad folks are to get rid of them!
Interesting toy for a noob like me, though.

Jerry, I guess I'm going to need some resistors over a 1/2w ;)
I found the famous message# 84399 and need some time to digest the whole
conversation that went with it. I can see a shopping list coming out of it
if this goes the way I fear it will..
Very nice looking dummy load, Jerry!

BTW, I lifted 1 leg of C81 to 89 caps.
ESR by scope & FG at 200kHz and ?F by Fluke
C2081 0.8Ω 109?F
C2083 1.2 Ω 97.7?F
C2085 0.8 Ω 111?F
C2087 2.08 Ω 8.7?F
C2089 0.8Ω 9.23?F

Thanks all!
Keith



On Mon, Dec 15, 2014 at 1:06 PM, 'Dennis Tillman' dennis@...
[TekScopes] <TekScopes@...> wrote:

Huntron Trackers are a joke (pardon my bluntness).
I am astounded that they can charge so much for something that does so
little.
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Sunday, December 14, 2014 5:35 PM
To: TekScopes@...
Subject: Re: [TekScopes] 7704A -just a quickie

<snip>
This may be contentious: I've acquired a couple of Huntron Trackers (1000 &
2000) that were thrown in with a couple of scopes some time ago. I've never
seen them mentioned here and would be interested to read any opinions on
their efficacy.
I used the Huntron 2000 for the continuity tests. I liked the indication of
whether the circuit being tested appears to be totally resistive or if some
other function is going on. I'm certainly not suggesting I possess any
expertise in its use.
All supply paths tested looked purely resistive, as expected.

------------------------------------
Posted by: Keith Smith <kahsmith@...>
------------------------------------

--
Keith Smith - KeithSmith.ca_Freelance Guitarist & Location Recording Service
<>

We had a thread here recently on a 456B with no sweep. In that case it turned out to be in the A sweep generator, see <>. This sounds similar, as the Q1024 collector voltage is off-spec. This voltage ought to be defined by the BE voltage of Q1036 and the pinch-off of Q1030, and should be practically invariant whether you're sweeping or not.



In the thread above it was the equivalent of your Q1030 that had gone bad, and was I believe shorted G->S. This leaks the ramp current into the base of the downstream transistor - Q1036 in your case.
The symptoms were slightly different, IIRC, as the sweep did start, but effectively went backwards and never triggered the end comparator.
Have you tried ramping the sweep speed up and down the range? If the JFET is bad, you may get a sweep on the highest ranges where Rt is the smallest, as there's sufficient base current for Q1036 there, at least.


You can measure whether the JFET is leaking through the gate by measuring the voltage drop over R1029, it should be zero. Also check Q1036, if that's shorted B->E, you'd see about the voltage you're seeing at Q1024's collector - I think.

I bet one of those is your problem (but I'm often wrong ;).



Note that the A and B sweep generators are identical, so you can swap components between them. Are the transistors socketed on your 465?

Huntron Trackers are a joke (pardon my bluntness).
I am astounded that they can charge so much for something that does so
little.
Dennis Tillman W7PF

647 EHT transformer info posted to the group photo section (I hope)
I am pretty sure the transformer is same for 647A scopes
Chris HJ

Has anyone ever been able to find the winding specifications for any other HV transformers (specifically the 647)? It seems like it would be good to find and archive as many as possible before they're lost forever.

On Mon, 15 Dec 2014 13:57:48 +0000, you wrote:

Bert,

The recent "design ideas" discussion led me to an announcement of a IGBT
that does not require a snubbing circuit

There have been IGBTs out there for quite some time, that clamp overvoltage not
by avalanching in the main device, but by intentionally turning the device
partially on, by means of a zener diode between collector and gate. It's not a
new thing.

Prime examples of such devices are the IGBTs used in engine ignition systems.
See the datasheet of the STGB20NB37LZ, to learn about it.

It makes perfect sense to extend this technique to higher frequency operation,
in switching power supplies.

It's true, of course, that there will be more power dissipation in the IGBT,
than when using a snubber. But who cares? What matters to a manufacturer is
getting the job done at the lowest possible cost. If a snubberless IGBT mounted
on a slightly larger heatsink is cheaper than a plain IGBT mounted on a smaller
heatsink plus a power resistor, high voltage capacitor and fast diode, they will
go for it. And typically the overall efficiency is better when using such a
clamped IGBT, than when using a snubber, because the IGBT clamps just the
necessary minimal amount, while a conventional snubber also consumes some energy
when the voltage is well inside the allowed range.

Manfred

This works at low Vds but at high Vds, the Vgs temperature coefficient reverses
so MOSFETs and IGBTs (*) suffer from something very similar to secondary
breakdown where local areas of the die can thermally runaway. The result is
that at high Vds, it may not be possible to turn the device on if the required
Ids is high without damaging it.

Ignition systems are relatively low power so this will not be a problem for them
but it is an issue for motor drives and high power switching power supplies.

The old lateral power MOSFETs did not suffer from this problem at least as much
but the highest density vertical MOSFETs sure do and it makes them unsuitable
for linear applications. For a while they made IGBTs intended for linear
operation but they were never common.

(*) Everybody says IGBTs are immune to secondary breakdown but their safe
operating curves sure show something that looks like it. I assume it is either
secondary breakdown in the bipolar transistor or a reversal of Vgs temperature
coefficient in the MOSFET.