Date   

Tek514D Blows Fuse

Steve Hendrix
 

My dad is a long-retired EE, and no longer able to do a lot of electronics. But we are enjoying a chance to work together, where I can be his eyes and hands while he shares his knowledge of ancient (to me) history. I'm a practicing EE today, but my knowledge of tubes is mostly theoretical. I live about an hour away from him, so need to be sure I take along everything I need when I visit. So there's the picture.

Yesterday I attended a funeral for a high school classmate of mine, and took the opportunity afterwards to visit Mom & Dad to tinker some more with another instrument (to be discussed on the HP group). I didn't have my scope along and found that we needed one, so fired up his Tek514D. Not so much, this first try - no line fuse installed. We couldn't find any reference for the correct fuse (I've since found it, a 5A slo-blo) and the only one we had handy was a 20A - the house circuit breaker will protect that! But we tried it anyway. Power switch on, pilot light lights, fans run.....maybe 20 or 30 seconds, then all dark. Yup, the fuse is more than clearly blown.

Based on discussions here and on the HP group, I'm suspecting deteriorated electrolytic caps in the power supply. I found a schematic on the Bama site. It appears that Tek liked to just stock one size (20 µF) and use them in parallel where more capacitance was needed. I assume that those probably need at least a 630V rating. We didn't have time to open up the scope, as I had to attend to several household repairs while there. Can anyone guide me as to what physical size is going to fit, and even get so specific as to what to order from DK? I have a large stock of capacitors of all sizes, but very limited on high-voltage types as I mostly work at 24VDC and below these days. Any other tips as to how to tackle this?

One other question as well. I recognize the schematic symbols for triodes, tetrodes, and pentodes. But they use an unfamiliar symbol several times in the schematic of the power supply. Sometimes two plates on opposite sides of a circle, with a little hook entering 90º from the plates (similar to the cathode symbol in the tubes). Sometimes the two plates are side-by-side, with the hook directly opposite them. What is that? Based on the way they're used in the schematic, I'm speculating that they're diodes. (?)

Steve Hendrix


Re: Tektronix 2245a Flickering Trace

William Schuler
 

“Do you have a second scope you could turn on
your 2245A?

Siggi”

That makes me wonder – can you use a mostly functional scope to diagnose
itself? Or could that be catastrophic, like creating tears in the
time/space continuum when messing around with time machines? ; )

If it comes to it my friend has a scope for use.

On Thu, Jan 2, 2020 at 11:22 PM William Schuler via Groups.Io
<guitardad1967=gmail.com@groups.io> wrote:

Thanks for narrowing it down guys. I will look into it this weekend. I
could take it over to my buddies house who has a scope...

On Thu, Jan 2, 2020 at 8:54 PM KB6NAX <gumbear@...> wrote:

Yup, I have to agree with Siggi. The "OSD," meaning the vertical
sensitivity callout in the lower left hand corner and the sweep time in
the
lower right hand corner also are jumping sideways along with the
sine wave. So the jitter is occurring in the horizontal amplifier chain,
not
the triggering circuit. With power off, carefully reseat anything that
plugs in.
Don't slip up and plug anything back in wrong that you pulled out - no
bent
pins, etc.

Arden


I think it's safe to say that you have more than just a triggering
issue,
as your OSD (on-screen display) is jumping around as well as the traces
(see e.g. around here https://youtu.be/j6Dqke1CIRE?t=74). This could be
as
simple as a marginally plugged-in connector somewhere, but you should be
looking at points common to the OSD and sweeps. This includes power
supplies and e.g. the horizontal amplifier. Your vertical appears
unaffected, however.
If you haven't read this:
https://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf
already,
you may want to take a gander. Do you have a second scope you could turn
on
your 2245A?

Siggi <







Re: TDS694C 50 Ohm Overload

 

Hi George,

I believe that is the input preamp, not the ADC. There's a good possibility that someone overloaded and killed it. They are BGA devices so they're not very repairable without a donor board and re-balling.


Re: Anyone ever heard of a 535-S6 model Tek scope?

Jamie Ostrowski
 

Interesting find, John. Thanks. I noticed it is in the earlier style case,
too.

On Fri, Jan 3, 2020 at 9:43 PM John Williams <books4you@...> wrote:

The 535-s6 listing should say

1.5 microseconds to 10 seconds for the delay spec.




Re: What you may not know about the creator of Groups.io

Jim Ford
 

Hi, Dennis.You do have to click on the Did You Mean link on Wikipedia.  Your link below doesn't go directly, FYI.Mark's blog was far too software-oriented for a hardware guy like me.  Although I am trying to learn Python so I can control my test equipment via GPIB and USB.  That's not proceeding very rapidly, though.Oh well.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Dennis Tillman W7PF <@Dennis_Tillman_W7pF> Date: 1/3/20 7:23 PM (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] What you may not know about the creator of Groups.io Mark Fletcher has a long history developing very successful softwareapplications.I frequently get a reply from him to questions I ask or to features we wouldlike to see added to TekScopes.Contrast this with Yahoo groups where it was impossible to call, email, senda letter, or walk into an office to request assistance. There was no way toknow if there were still humans involved or was it running all by iteself.This Wikipedia link will tell you a little more about Mark. It is a quickread.https://en.wikipedia.org/wiki/Mark_Fletcher_(businessman)This is the link to Mark's Blog. You can spend as much time as you wantreading about the fascinating things he has been involved in and developed.One of Marks earlier creations was acquired by Yahoo in 2000 and becameYahoo Groups. If you scroll down, almost to the bottom (Sept. 23, 2014) youcan read the introductory announcement of his latest creation, Groups.io,which he created because, as he puts it, "Yahoo Groups and Google Groupsboth exude the dank air of benign neglect."https://wingedpig.com/Dennis Tillman W7PF-- Dennis Tillman W7PFTekScopes Moderator


Re: Anyone ever heard of a 535-S6 model Tek scope?

John Williams
 

The 535-s6 listing should say

1.5 microseconds to 10 seconds for the delay spec.


Re: 465M Junker

toby@...
 

On 2020-01-03 8:40 PM, KB6NAX wrote:
Here's the latest news on my junker 465M:  The input FET's I ordered
came in.  Three Siliconix old stock 2N5912's and one 151-1090-04 old
stock.  I cobbled together Tek's 20 ohm totem pole circuit on a
prototyping board.  I set the + and - 5 volt supplies precisely.  All of
the FET's were well under 20 mV offset from 0 volts at the output.
...
douched the connectors with MG Chemicals Super Contact Cleaner and
reseated the connectors multiple times.  Finally, the scope became
quiet.  Twisting, tumbling and other forms of abuse yielded no more
noise problems.  I'm gonna let the patient burn in for a while and
torture it some more before going into calibration mode.  I'm not sure
I'm "there" yet.
These stories are fantastic and very educational to repair noobs like me.

Thankyou for posting it!

--Toby



Arden


-----Original Message----- From: kb6nax
Sent: Friday, December 27, 2019 1:23 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 465M Junker

Progress report on the 465M junker:  After a couple of good sessions I
think
I found nearly all of the problems.  ..........



Re: 575 vs. 576 comparisons

Mlynch001
 

Gary,

Well, if you get a 576 you still gonna need that cart. The 576 is heavier than the 575. I prefer the larger screen, readout display and the overall more modern design. That being said, the 575 is a very capable machine in its own right. I am not well versed into tube technology, so I prefer to stick with the solid state 576 or 577. My brother has a 575 and I have the 576 and 577D1. So we have the bases covered pretty well. Either way you go, you have a winner, providing that they work.

--
Michael Lynch
Dardanelle, AR


What you may not know about the creator of Groups.io

 

Mark Fletcher has a long history developing very successful software
applications.
I frequently get a reply from him to questions I ask or to features we would
like to see added to TekScopes.
Contrast this with Yahoo groups where it was impossible to call, email, send
a letter, or walk into an office to request assistance. There was no way to
know if there were still humans involved or was it running all by iteself.

This Wikipedia link will tell you a little more about Mark. It is a quick
read.
https://en.wikipedia.org/wiki/Mark_Fletcher_(businessman)

This is the link to Mark's Blog. You can spend as much time as you want
reading about the fascinating things he has been involved in and developed.
One of Marks earlier creations was acquired by Yahoo in 2000 and became
Yahoo Groups. If you scroll down, almost to the bottom (Sept. 23, 2014) you
can read the introductory announcement of his latest creation, Groups.io,
which he created because, as he puts it, "Yahoo Groups and Google Groups
both exude the dank air of benign neglect."
https://wingedpig.com/

Dennis Tillman W7PF






--
Dennis Tillman W7PF
TekScopes Moderator


Re: 575 vs. 576 comparisons

Gary Robert Bosworth
 

I am very happy with my 575. It is electronically lean and mean. If you
have healthy tubes, and relatively new power supply capacitors, the display
is crisp and stable. My only complaint is that the 575 is outrageously
heavy. You really need to put it on a cart if you want to get it out of
your way.

Gary

On Fri, Jan 3, 2020 at 6:46 AM John Griessen <@jgriessen> wrote:

Can someone point me to good talk about the differences in the groups.io
archives?

There's a cheap 575 available, but I'm trying to reduce down for a move to
NM...

576 is better by far and best to wait for, right?



--
Gary Robert Bosworth
@grbosworth
Tel: 310-317-2247


Re: Anyone ever heard of a 535-S6 model Tek scope?

John Williams
 

Here is the listing in the 1958 Tektronix Catalog:

Special Models

Type 535-S1 , sweep delay 1 /<sec to 1 sec . . . $1 325

Type 535-S2, sweep delay 1 00 /'.sec to 1 sec . $1 325

Type 535-S6, sweep delay 1.5 ^sec to 10 sec. $1325

I am not sure what all that means though.


Re: Anyone ever heard of a 535-S6 model Tek scope?

snapdiode
 

Awesome. Never heard of this, and it's not in Stan's handbook. Have you asked the seller the origin of this scope?


Re: ACCOUNTING FOR YOUR CONTRIBUTIONS

Reginald Beardsley
 

I sent $10. I should be delighted if any or all were spent on "dinner for two".

I'm very interested in the accounting as a metric of the health of the community. Not how it was spent, but how much was contributed.

Thanks.

Have Fun!
Reg


Anyone ever heard of a 535-S6 model Tek scope?

Jamie Ostrowski
 

I ran into a 535-S6 scope on ebay. I don't know the seller...I don't even want to buy it. But I am curious - has anyone heard of one of these? I couldn't find any info on it.

https://www.ebay.com/itm/Oscilloscope-535-S6-Tektronix-Vertical-Amplifier/324031553118?hash=item4b71c91e5e:g:s-4AAOSwTzBeD6Wm


Re: 465M Junker

KB6NAX
 

Here's the latest news on my junker 465M: The input FET's I ordered came in. Three Siliconix old stock 2N5912's and one 151-1090-04 old stock. I cobbled together Tek's 20 ohm totem pole circuit on a prototyping board. I set the + and - 5 volt supplies precisely. All of the FET's were well under 20 mV offset from 0 volts at the output. So I flipped a coin and installed a 2N5912 into the channel 1 vertical amp circuit. Now I had two working channels. But what came next was a trip down a bumpy road. The gain match between channels 1 and 2 was inconsistent on various sensitivity settings. Channel 1 was erratic and at times very noisy. After fussing and fuming I removed the shield from the ch 1 attenuator switch and spotted a possible source of the problem. Some years ago I gave up on a 475 which had several faulty attenuator plug-in modules. The 465M has two in each channel. I worked them up and down in their sockets a few times and seemingly made a reduction in the erratic behavior. But being a glutton for punishment I wasn't going to give up yet. Just moving the scope around caused dramatic changes in the chaos displayed on the CRT. And then suddenly it would stop, I'd get nice noise free traces. Then it would start up again. Turning the scope over a couple of more times the CRT went blank, no trace. Having repaired HV problems on 455's I know to take a look at the +95 volt test point. Nothing there. The HV 32 volt fuse was blown. It's supposed to be a 250 mA fast blow but what was in the fuse clips was 1.5 amps. Wow! Catastrophic failure - groan. More punishment. To cut to the chase the oscillator NPN was dead shorted. It just so happens I have a bag of NOS GE D44H11 transistors, what Tek uses in the 455 and 465M under their part number. After replacing the transistor the HV came up and the typical 90 mA was flowing through the new 1/2 fuse I installed. That was a close call. Back to the masochistic effort. Looking for broken solder joints I found one of the 300 mA UNREG 32V fuse clips to be broken. I soldered that and went about looking for the intermittent some more and then the trace again magically disappeared again. But I heard a faint "tink" when that happened, the sound of a fuse blowing. Now I was about to excrete a brick. I didn't have a 300 mA fuse so I put in a 1/2 amp fuse and powered up on the variac as usual. Line current normal, everything working again. Must have been a tired fuse. Twisting, turning prying, poking, and probing I finally found my way to the +5 volt supply bus and observed very noisy behavior when it was nice enough to present itself. Ah, well, those damn cables that connect the rear panel power transistors to the power supply regulator circuits at the rear of the scope could be the problem. Why didn't I think of that earlier? I douched the connectors with MG Chemicals Super Contact Cleaner and reseated the connectors multiple times. Finally, the scope became quiet. Twisting, tumbling and other forms of abuse yielded no more noise problems. I'm gonna let the patient burn in for a while and torture it some more before going into calibration mode. I'm not sure I'm "there" yet.

Arden

-----Original Message-----
From: kb6nax
Sent: Friday, December 27, 2019 1:23 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 465M Junker

Progress report on the 465M junker: After a couple of good sessions I think
I found nearly all of the problems. ..........


Re: ACCOUNTING FOR YOUR CONTRIBUTIONS

KB6NAX
 

By now just about everyone has read my post to TekScopes "asking for small
contributions" (my exact words). I owe you a complete financial accounting. .......

I wonder why. Whatever one contributes is done gratis without expectation of becoming a titan of technology. If you get a few extra nickels in your pocket, Dennis, give them to your favorite charity. Just my "contribution." Back to finishing up my junker 465M.

Arden


Re: Tek 2710 SA error: Unable to delete files at startup

alfa beta
 

@Rogerio :
had the same problem with my 2710, I tried the fix but it didn't work with my unit
It was many years ago, in the end I sold the failing 2710 and bought a 2712
Anyway the schematics of the fix are here

https://drive.google.com/open?id=1TAAd8pYNN3hkDGeYgNHsr33b7Brjc8MJ

https://drive.google.com/open?id=1Vm-WE_EQSDuvua8fINe-6E1iqfEHv0rS

adri






----- Messaggio originale -----
Da: Rogerio O <@rodd414>
Rispondi a: <TekScopes@groups.io>
A: <TekScopes@groups.io>
Inviato: 03/01/2020 20:10:38
Oggetto: [TekScopes] Tek 2710 SA error: Unable to delete files at startup
________________________________________________________________________________

Dear all,
I bought one unit with this error some years ago.
Since then I have seen other units on sale with the same problem but I could not find a solution for this problem.
I have been contacted by an Edaboard member who thought I have found the solution described there in an old post.
I copied below the post with a description of the solution to the problem, but, unfortunately the schematic with the mod developed by him was lost due to a database error.
My hope is that one person of this forum that is familiar with the 2710 design could figure out how to reconstruct missing the signals using the 74HCT04 and 74HCT00 as mentioned.
Happy 2020 for all
"*****quote*******
Hi,
here is another 2710 which had this problem.
I bought it from a colleague who described these symptoms before repair:
- Power-on messages about NVRAM / file system errors
- Spurious characters on the display
- Useless files which could not be deleted

After exchanging battery, RAM and bus drivers on the display storage board, he used a logic analyzer to track down the error to a faulty OE- signal from PLD U352 Pin 24 to bus driver U462 Pin 19. The CPU could still write to the NVRAM, but reading was not possible.

The faulty OE- signal could be reconstructed from other existing signals by two SMD logic circuits (74HCT04 and 74HCT00).
After his repair, almost all analyzer functions worked, but many amplitude normalizations always failed.

It cost me some more hours to find out that the CPU will read the acquired signal not only from the NVRAM, but also accesses the ADC data directly. The logic signal for this is called REDAT-.

So I extended the replacement circuit, and now the amplitude normalizations also work. It seems that REDAT- is not used during normal operation, but only for calibration.

A simplified but logically equivalent circuit is attached as PDF. It uses a 74HCT08 and 74HCT00 for reconstruction.

The ICs are stacked onto U566 (right besides the bus connector) and powered by vertically soldered wires on Pins 7 and 14. All other pins have been bent to go out straight horizontally and are connected using thin isolated copper wire (as used e.g. for transformers).
Pin 19 of the bus driver U462 is lifted from the PCB, the original DROE- signal is taken from the PCB-pad and the reconstructed signal is routed to the pin.

I cannot be sure that all 2710 can be repaired this way, but since the symptoms described here are very coincident, there is a good chance to make them all work again.

Good luck,
Andreas.


******** unquote**********


Re: Push-push switch repair (need some theory of operation)

Ke-Fong Lin
 

Hi everyone,

Thanks for your comments and advices. I'll work on the switch this week-end.
My intention was to open it and "twick" it back to work. But I got convinced to use some cleaner/lubricant on it.
I've settled on MG chemical's super contact cleaner. I'll order that monday.
So basically, I'll open it this week-end and hopefully re-assemble and hopefully make it work by the end of next week.

Best regards,


ACCOUNTING FOR YOUR CONTRIBUTIONS

 

By now just about everyone has read my post to TekScopes "asking for small
contributions" (my exact words). I owe you a complete financial accounting.
This will take me a day or two to prepare. So please be patient.

With a few exceptions everyone used PayPal so it will be relatively easy to
post a sorted list of PayPal transaction numbers and the amount received
from each transaction. Anyone who contributed will be able to confirm their
contribution has been accounted for by verifying their transaction number
and amount are in the list. No personal information will be revealed this
way.

Please hold any suggestions for how to do this the next time or how to spend
the money. Michael Dunn and I have discussed these very same issues and
more. I will include our thoughts about how this should be handled along
with the financial accounting of the contributions.

I need a few days to create an accounting of the contributions and to
summarize Michael's and my ideas for how to proceed. Until then please be
patient and make space in the forum for our members to ask questions about
collecting, repairing, restoring, and using the wonderful tools Tek's
engineers have created for us to explore and play with.

Dennis Tillman W7PF



--
Dennis Tillman W7PF
TekScopes Moderator


Re: 130 LC meter

Richard Knoppow
 

Re parasitic reactance in resistors. I used my late lamented Boonton RX meter (looking for another, it got knocked off a bench and is unrepairable). I found that in the range of the instrument carbon and metal film resistors had considerably less parasitic reactance than carbon composition resistors. In fact, this is illustrated in the instruction manual. While one would think the spiral construction of the resistor would result in considerable inductance it does not. The parasitic capacitance is neutralized by any inductance. Of course the amount depends on the value and size of the resistor but ordinary quarter or half watt units up to several thousand ohms have very little reactance.

On 1/3/2020 12:11 PM, Albert Otten wrote:
Hi Dave,

Nice to read that at least one person was content with that frequency based calibration method.
Some remarks follow below.

Albert

On Thu, Jan 2, 2020 at 09:21 PM, Dave Wise wrote:

Not the OP's problem but it's about the 130. I want to document some
interesting symptoms and their causes.

I calibrated it using Albert Otten's 2016 topic "Tpe 130 L-C meter calibration
using only a 300 pF cap", https://groups.io/g/TekScopes/topic/7656928#126515 .
It's much easier than acquiring an S-30, all you need is one good close cap
and a frequency counter. Few labs had counters when the 130 was born.
Since I had the counter connected, I decided to try calibrating C7, Resistance
Compensation.

SYMPTOM: Not possible to match readings 1M vs 100K, C7 at minimum still too
big.
FIX: Reducing R8 helps. I put in 680K instead of 1M.
It looks like my C7 is also at the in one extreme but I don't take the risk (of breaking) to adjust his trimcap.
NOTES:
Carbon film and metal film have less parasitic C than carbon comp at these
values and frequencies.
...
Old black Welwyn 1% spiral-cut carbon? film resistors in my junk box which
happen to be the type used in early production of S-30: 100K is 0.4pF, 1M is
0.5pF . > So I adjust R8 so 1M reads 0.1pF higher than 100K.
I didn't try to measure parasitic capacitance of a 1M or 100k resistor. But I did several measurements with resistor clamped in the fixture, excessive lead length cut away. I inserted a resistor, set the offset for a reading at 1.5 pF, the quickly removed the resistor and noted the drop in the reading. Essentially always the reading dropped by 0.25 to 3 pF, for different R values and different ratings (1/2, 1/4, 1/8 W), metal film and cc. So I should be content with the setting of C7 I think. The big Welwyn resistors (body over 1") give a drop of 1 pF or slightly more.
There is also a remark in the manual about line voltage sensitivity when C7 has not enough range. You might look at this.
SYMPTOM: C99 and C100. Tek installed them backwards, they're
drawn backwards on the schematic too.
FIX: Probably EVERY 130 needs them replaced, with anode facing positive voltage.
This seems so obvious that we might guess that Tek had a special reason for this. At full scale deflection the (reverse) voltage is 0.75 V. That might or might not be high enough to cause damage? Could it give some meter protection when the multivibrator frequency approaches zero?
SYMPTOM: 10pF reads high on 30pF range.
CAUSE: Dielectric Absorption in C92 .0047/400 charge pump cap.
This is the first failure I've ever seen that was traceable to DA.
It makes the cap appear larger than it should be, and changing with frequency,
so readings that are low on the scale pump too much charge and get skewed upwards.
NOTES:
You can measure C92, C93 etc in-circuit if the 130 range switch is OFF.
The cap is not leaky.
It's a Sprague 160P DiFilm. (Plastic/paper dielectric.)
Use GR 1680-A to measure C at 1kHz and 400Hz.
Should read 4.7nF, but I see 6.5nF at 1kHz, 7.5nF at 400Hz. Yep.
An ideal cap will be constant C, a cap with DA will increase with decreasing f.
Later I tested it using the soak-discharge-wait-measure method. Significant rebound,
over 10V after 100V soak. That will mess up a charge pump!
FIX: Replaced with polypropylene. Also replaced C93 .015/400 10pF range because
it had some DA too.
I measured C91 to C95 both with the GR 1656 (1 kHz) and with a cheap Aldi DMM. The 2 readings were remarkably close, within 0.5%, except for 3.5% in C91. Also the differences from nominal were <10%, except again for C91. The measurement principles are very different. Hence I would trust C92 to C95 but question C91.
Joke's on me - now 10pF on 30pF range reads a bit low where it used to read high.
I bet those 160P caps had some DA when new, and Tek drew the meter scale to fit.
Maybe I should have used something with more DA. Oh well, |error| is smaller now at least.
LESSON: Replace all paper/plastic caps in positions sensitive to Dielectric Absorption,
even if they test good for leakage.
The scales are non-linear anyway since the frequency deviation is a nonlinear function of the capacitance under test. This is most pronounced at the 300 pF range but hardly visible at the 10 pF range. The 3 pF range can be considered as linear. I doubt that Tek corrected the scale for other effects. I didn't check my 130 yet with 10 pF on the 30 pF range but this should be easy using the frequency counter. Maybe later.
HTH,
Dave Wise
--
Richard Knoppow
dickburk@...
WB6KBL