Re: 466 +15 supply and U1724 (1458)

If the +65 volt supply is actually +60 volts, then that explains why
all of the other supply outputs are slightly low. They all directly
use the +65 volt supply as a reference so there is no mystery there.

Interesting the other half U1724A both inputs are 4.5 should be 8.9. Output 5.1 should be 8.3. And the Vcc is also 4.5. The reference voltage from VR1726 is correct enough at 9.3.
If the output of U1724B was driving Q1752 and Q1756 hard, like 8.8
milliamps hard which is within the output current limit of a 1458,
then Vcc would be pulled down causing problems with the +65 regulator
as well so I think we are looking at a problem with just the +15 volt
regulator. C1757 which you identified is the prime suspect. From the
Tektronix 466 parts list:

10uF 25V 20% 90201 TDC106M025FL Mallory

http://datasheet.octopart.com/TDC475M035NSF-CDE-datasheet-110389.pdf
http://www.cde.com/resources/catalogs/TDC.pdf

I was originally suspicious of a socket but now I think it was Colonel
Mustard, in the Conservatory, with the Candlestick. Err, I mean the
solid tantalum capacitor, in the +15 volt regulator, with a short.

There might be a short somewhere else on the +15 volt supply but
removing C1757 is the place to start. If you have a 10uF to 100uF
aluminum electrolytic capacitor laying around it can be used in its
place.

All voltage measure slightly low but the +15 is way down to 1.4V. Unregulated +15 is slightly high 25.9 vs 22.5 presumably because of no current through pass regulator Q1756.
Is it possible that the 10uf cap to ground at the + input [actually +15 volt output] is bad pulling that input down?
Given the above, this could be the whole problem. A shorted C1757
will pull the +15 volt output down, Q1754 will then limit the current
by pulling the output of U1724B down and that will cause Vcc of U1725B
to be pulled down.

On 25 Jan 2016 03:57:16 -0800, you wrote:

Thanks David for the input. Yes, I was thinking of the .02uf at the input but wrote the 10uf on the output. My bad.

The 65V is around 60V and adjustment is non-reponsive; but that is to be expected since U1724 is not working. No sockets on this board. So I'm going to check the supply to U1724 - R1727 and VR1725 and the U1724 itself.

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

Re: 7603 weirdo inverted Z axis

Albert Otten

Hi David,

From 15 V to 28 V seems a rather small change compared to the data in the calibration section. Maybe you set the time base for a slow speed that activates the Intensity Limit?
Albert

============

With Q1107 (a slow 2N3904???) removed on my 7603, the output at point
B is 14.8 volts which closely agrees with our current calculation so I
wonder if Marian's <public@... mailto:public@...> measurement of 20 volts at the
output of the z-axis amplifier is significant and indicates a problem.
I get the same 14.8 volt output with Q1107 installed, the readout off,
and the intensity control turned to minimum.

I also measured the output at point B and as the intensity control is
turned fully clockwise, the output increases to about 28 volts
monotonically.

Re: Hello from new member w 2465A issues

The oscilloscope does not need the AC line capacitors to operate so I
would remove them for now and verify that there are not other
problems.

The inrush current limiter, RT1016, is *after* the capacitors so check
the condition of the fuse.

On 25 Jan 2016 06:46:42 -0800, you wrote:

Hi David,

You are right, two large paper caps on the AC board have burst open - those were the bangs I heard. The main rectifier caps (in the black plastic holders) seem to be okay. I'll need to research the current limiter you mentioned. In your experience, should I replace all the capacitors like some people have advocated on Youtube or just the two broken ones?

Re: OT: QService components

Ed Breya

The best deodorizer is hydrogen peroxide solution - it works on most organic residue (even skunk juice). Just put some standard 3% H2O2 solution in an aerosol pump spray bottle and mist it onto the surfaces, then wipe and air-dry the item thoroughly before use.

Ed

Re: Hello from new member w 2465A issues

Ed Breya

Those paper AC line X-caps have been the subject of much discussion here and on the hpagilent group. They are the ones potted in amber colored epoxy, usually WIMA or RIFA brand. The bottom line is that they should be eliminated whenever encountered - even if not already failed - and replaced by proper X-rated plastic-dielectric caps. This is especially important in high line voltage (~240V) countries, where the caps are operating near their limit.

These are also used inside of some packaged line filter assemblies, and known to have caused internal failures there.

Ed

Engineering Co-op's

Hello All,

I am getting ready to wrap-up my first year at the University of Akron and was hoping someone here might know if Keithley Instruments in Solon, Ohio has any co-op positions. I know they were bought by TEK a few years back, but do not know if those intern opportunities went to Beaverton or elsewhere. Any help or guidance would be greatly appreciated.

Cheers,

David

Re: Engineering Co-op's

Ed Breya

I'd recommend looking to see if there's a Tek/Keithley design or manufacturing operation listed there locally and contact them, rather than starting at Tek HQ. If there's a Tek field office nearby, someone there should know. Also, the university should have info about local opportunities.

Ed

Re: Engineering Co-op's

Thank you Ed. I have checked with the university staff and career office, but they do not know of co-op’s with the local TE firms, all mostly Danaher. Do you know of anyone in this industry local to me who might offer direction?

Cheers,

David

Re: Recommendations / 2247A

John Dickens

I did not realize the 2236 has a 6802.

John

On Jan 25, 2016, at 4:18 AM, Malcolm Hunter malcolm.r.hunter@... [TekScopes] <TekScopes@...> wrote:

On 25 January 2016 at 00:45, John Dickens jake_117_dickens@... <mailto:jake_117_dickens@...>
[TekScopes] <TekScopes@... <mailto:TekScopes@...>> wrote:

It would be my first scope with a microprocessor. I also have a 7603 and a
2236 as well, not to mention a 503 in poor shape.
​The 2236 has a 6802 microprocessor, so the 2247A won't be your first. Or
do you mean something else?

Malcolm​

Re: OT: QService components

Hi Malcom,
I have bought from them several times and never encountered a tobacco smell.
I would have remembered if I had, since I have been a non-smoker all my
life. My dad was a lifelong cigar smoker and I can't stand the smell of
cigars to this day. Apparently we have a lot of non-smokers in the forum
judging from the comments I am seeing.

Someone else mentioned QService is out of business but I don't think that is
the case since they are still selling on Ebay and they have an active web
site at
http://www.qservice.eu/

Dennis Tillman W7PF

-----Original Message-----
Sent: Monday, January 25, 2016 4:01 AM
Subject: [TekScopes] OT: QService components

Hi,

Has anyone else ordered items from QService in Greece? I just received my
first order from them and everything smells of stale tobacco smoke. Is it
just me?

Malcolm

------------------------------------
Posted by: Malcolm Hunter <malcolm.r.hunter@...>
------------------------------------

Re: OT: QService components

Hi Dennis,
Someone else mentioned QService is out of business
I think you're referring to Stefans T.'s message. He wasn't referring to QService:

Lol, we had a very small electronics mail order here, over the years
> you could smell how his habit increased.
> The man is out of business now.
I've been a non-smoker all my life. I've purchased a few items from QService, one being a pretty large PCB (TDS520 logic board) in an antistatic bag. I can't remember them smelling of smoke.

Raymond

Re: Hello from new member w 2465A issues

Tothwolf

On Mon, 25 Jan 2016, edbreya@... [TekScopes] wrote:

Those paper AC line X-caps have been the subject of much discussion here and on the hpagilent group. They are the ones potted in amber colored epoxy, usually WIMA or RIFA brand. The bottom line is that they should be eliminated whenever encountered - even if not already failed - and replaced by proper X-rated plastic-dielectric caps. This is especially important in high line voltage (~240V) countries, where the caps are operating near their limit.

These are also used inside of some packaged line filter assemblies, and known to have caused internal failures there.
Rifa brand, not Wima. Wima has never made those translucent yellow X and Y type safety capacitors. Kemet now owns Rifa and continues to make these paper insulated safety capacitors, however I will not use them and generally replace them with Epcos film types of the same safety class (X or Y, it matters).

Re: Recommendations / 2247A

For what it is worth, I hear about fewer problems with the 4 channel
22xx oscilloscope than the 2 channel 22xx oscilloscopes and the 24xx
oscilloscopes. They seem to be more reliable although my 2247A does
currently have a problem that I have not tracked down. Apparently the
reference clock for the timer/counter is intermittent and I suspect
the clock crystal or oscillator is failing. I just have not gotten
around to fixing it.

The 4 channel 22xx oscilloscopes are also fully documented and parts
mules are inexpensively available making them easy to maintain.

The 2247A will not really do anything that your 2236 cannot but it has
a lot of user features. They both have a gated universal
timer/counter which is the big feature for these models. The 2247A
adds cursors, voltage measurements, and gated voltage measurements.

As I posted earlier, the 2247A series does *not* use digital
calibration so it does not have the loss of calibration issues of the
24xx series oscilloscopes which might be considered an advantage.

If I did *not* already have a 2247A, then I would want a 2236 for the
gated universal timer/counter.

The 2252 is not as common but it has all of the same features and for
practical purposes is the same as a 2247A.

On Mon, 25 Jan 2016 12:19:43 -0600, you wrote:

I did not realize the 2236 has a 6802.

John

Re: Hello from new member w 2465A issues

Ed Breya

I remember there were at least two brands that made those or similar caps. I looked up WIMA and found this example:

http://www.wima.com/EN/mp3x2.htm http://www.wima.com/EN/mp3x2.htm

They look a little different, but I think they're the kind I recall seeing in the past. I don't remember if I had seen any failures of this brand, but I assumed that they're close enough to the same as the RIFAs, which I've seen fail a few times - perhaps because they're more common.

Regardless of what the makers say in the specs, much experience here indicates that very messy catastrophic failures can occur with paper X-caps, with bangs, meltdowns, and noxious fumes - but perhaps no fires, which is the main point. The X-rated caps are for across-line use, so don't have shock hazard issues. The Y-rated are for line to ground, so could. I don't recall ever seeing this style of cap in a Y-application, only X, although it looks like they're available. I wouldn't trust them for any use - I've purged my stock of these long ago.

Ed

Two AM 503 CP Amps for parts or refurb

Bill (Doc) Courtright

Hello,
I am trying to clean house a bit here. I have two AM 503 Current probe amps that are complete except for one latch but both have a smoke film mainly on one side due to a smoky fire elsewhere in my former storage area.
One is SN B031467 with a tan board and some leaky caps the other is B064903 newer with a green coat board and is clean on the component side. This one should be salvageable.
I would like \$20 plus shipping for the pair. Due to their condition I would rather not put up on the auction site. Can e-mail pix on request.
Thanks,
Bill
KB3DKS

Re: Two AM 503 CP Amps for parts or refurb

I'll take them if still available.

Regards,
Tom WA3PZI

----- Original Message -----
From: Doxemf doxemf@... [TekScopes]
To: TekScopes@...
Sent: Monday, January 25, 2016 4:28 PM
Subject: [TekScopes] Two AM 503 CP Amps for parts or refurb

Hello,
I am trying to clean house a bit here. I have two AM 503 Current probe amps that are complete except for one latch but both have a smoke film mainly on one side due to a smoky fire elsewhere in my former storage area.
One is SN B031467 with a tan board and some leaky caps the other is B064903 newer with a green coat board and is clean on the component side. This one should be salvageable.
I would like \$20 plus shipping for the pair. Due to their condition I would rather not put up on the auction site. Can e-mail pix on request.
Thanks,
Bill
KB3DKS

Re: OT: QService components

Torch Fireman

On 25/01/2016 3:06 PM, 'Dennis Tillman' @Dennis_Tillman_W7PF [TekScopes] wrote:

Apparently we have a lot of non-smokers in the forum
judging from the comments I am seeing.
If you read the "Tektronics and You" employee manual, you will discover that the tobacco smoke smell is OEM. ;-)

Re: CL: Lot of 5 Tek 453's

They seem to be more reliable although my 2247A does
> currently have a problem that I have not tracked down. Apparently the
> reference clock for the timer/counter is intermittent and I suspect
> the clock crystal or oscillator is failing.
I have both a 2247A and a 2252. I like them a lot. I just wish their bandwidth would be larger.

My 2252 came with a problematic counter function. The PLL circuitry in the Slow Counter Logic IC (U1902) appeared bad.
As a test, I replaced the circuit with a simple XOR-based external PLL. It works so well that I decided not to go for a more elaborate solution.

Raymond

Tektronix TDS754D Fail++ Processor error + firmware

bddicch

Hello i have a TDS754D with a Fail ++ Processor error, from my experience with my TDS544A it was in that version part of recap job. and nvram failure.

To pinpoint this problem to the right direction. can it be a "dead NVRAM" ? ( after 10 years ) . i heared from other people the TDS754D version boards A10 and A11 have no smd cap problems.-> recapping not neccesary so not the problem with this A11 Dram Processor board.

can someone post a hex file from TDS754D NVram, (my options: 13,1F,2F,2C )

help wanted to solve my problem and hex file

2247A 2252 Timer Counter Reference

On 25 Jan 2016 13:53:02 -0800, you wrote:

They seem to be more reliable although my 2247A does
currently have a problem that I have not tracked down. Apparently the
reference clock for the timer/counter is intermittent and I suspect
the clock crystal or oscillator is failing.
I have both a 2247A and a 2252. I like them a lot. I just wish their bandwidth would be larger.

My 2252 came with a problematic counter function. The PLL circuitry in the Slow Counter Logic IC (U1902) appeared bad.
As a test, I replaced the circuit with a simple XOR-based external PLL. It works so well that I decided not to go for a more elaborate solution.

Raymond
That would be a much more involved repair than just a bad crystal or
bad oscillator. I hope that is not the problem with mine.

There number of things which could go wrong in that circuit including
the Motorola level shifters which I hear are known to be unreliable.
Usually with oscillators I find that the problem is the crystal.

When I run the detailed self diagnostics, they pretty much point
directly to a missing 100 MHz reference.