Date   

Re: 516 Triggering not working

Mark Vincent
 

John,

Looking at page 5-8 indicates mine is with the high voltage at the plate of the Miller tube V161A. Grounding the grid did make the difference in the paragraph; stuck in run up position. Zero sweep signal at R330. The only way a horizontal line can be generated is by putting the scope in the ext. horiz. mode and feeding a signal to the ext. horiz. post. Any signal stops on the right side of C44 if the scope is on or off. Varying the pots in the triggering circuit and varying the B+ did nothing. I know the triggering can be touchy. The B+ voltages are spot on.

Mark


Re: 516 Triggering not working

John Williams
 

Sorry Mark I forgot to ask if you have checked all of the power supply voltages. The sweep is especially sensitive to these voltages being incorrect.


Re: 516 Triggering not working

John Williams
 

Hi Mark. Sounds familiar. I have been fooled many times by the famous Tektronix sweep circuit. So if I sound like I am a bit dense please forgive. First, are you sure the sweep circuit is what is dead? If you check with your scope on either side of R330 / C330 you would normally see the sawtooth there if the sweep is running. This would be dead here if the sweep is dead. There should be sawtooth here if the sweep is running. If dead, you can check to see what state the sweep generator is stuck in. It can be run-up or not run-up. The procedure for checking this is on page 5-8 / 5-9 of your instruction manual, troubleshooting section. Once you have determined this the text should help guide you through further testing. Good hunting.


516 Triggering not working

Mark Vincent
 

I have been working on the circuit for a week after the 27mmfd to the Sweep
Gating Multivibrator and Hold-Off Circuit with no success. All I get now is
a spot, no horiz. line. The part before the 27mmfd condenser, C44, works
and was adjusted so signals will trigger on the plate side. Lifting the
"hot" side or a signal into the Ext. Trig. post will not start the
sweeping. There is zero output unless R114, R184 and R185 are unsoldered.
Using the cal. voltage output of another scope up to 100V made no
difference. Output was zero with the resistors soldered in. This is with
the scope on or off. Touching any of these resistors to its respective
point with them unsoldered will make the signal go to zero. The bias of
V135A and V185A is deep enough to cut these sections off. The valves are in
very good to like new condition and the resistors are 1% types. The power
supply voltages are right. The unit has been overhauled. This problem
suddenly came up. The diode across the 4700 ohm resistor is good and
another one did not make any difference. The hold-off caps are Orange
Drops. The timing cap is the original type. I did a resistance A-B with my
working 317. The resistances were the same. Reference was to the chassis.
Putting a signal in a vertical or horizontal input causes the spot to be
two spots with a thin dim trace in between them. I cannot figure out what
happened to cause the loss of triggering. I know this circuit is used in
other 300 and 500 series. Thanks.

Mark


Re: Tek 4654M; No Trace, No +5V, No +95V; Help

Tom Lee
 

I think we both inhabit pretty much the same neighborhood, where we kludge/kluge, jerry-/jury-rig, hack, bodge, etc. My UK friends long ago introduced me to "Heath Robinson" as their version of Rube Goldberg, and taught me that /bodge /and /botch /are cousins. I am all too familiar with them!

Happy sleuthing.

--Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 10/14/2020 13:22, Harrison wrote:
Tom. Thanks for setting me straight. For now I am going your Bodge route. I have located some 1N4148 diodes and will put them in so I can continue to chase the issue in parallel with locating the correct diode. I had to look up "Bodge". New word to me. In my neck of the woods we call it "monkeying something" or "jerry rigging". Have a good day.




Re: Tek 4654M; No Trace, No +5V, No +95V; Help

DaveH52
 


Re: Tek 4654M; No Trace, No +5V, No +95V; Help

Harrison
 

Tom. Thanks for setting me straight. For now I am going your Bodge route. I have located some 1N4148 diodes and will put them in so I can continue to chase the issue in parallel with locating the correct diode. I had to look up "Bodge". New word to me. In my neck of the woods we call it "monkeying something" or "jerry rigging". Have a good day.


Re: Tek 4654M; No Trace, No +5V, No +95V; Help

DaveH52
 

I had a problem with the +95 on my 465M. There's a 2uF/100V cap located between the HV shield and the 95V TP that was shorted.


Re: Tek 4654M; No Trace, No +5V, No +95V; Help

John
 

Michael, thanks for posting that Tek cross-reference. I was looking to determine what part number 156-0048-03 is in my 468 is and found it in there. I knew it was a transistor array of some kind but this allowed me to cross-reference to a manufacturers part number (SL3045) and locate a datasheet. I had wondered whether such a reference existed and have now downloaded it for future use. Thanks.


Re: Tek 4654M; No Trace, No +5V, No +95V; Help

Tom Lee
 

Hi Harrison,

A 1N400x rectifier will almost certainly be a poor choice. There's an important property of rectifiers known as "reverse recovery". In brief, once turned on, a real rectifier takes nonzero time to turn off (and this effect is distinct from junction capacitance effects). So when the applied voltage reverses, the diode will remain conducting for some time called the reverse recovery time. For a 1N4000-series rectifier, that recovery time is typically within a factor of 2 of 5us (depending on manufacturer). Also, at a 1A rating, that rectifier also has too much capacitance (I commented on this in my previous post), so aside from reverse recovery considerations, a 1A rectifier of any time is already a non-candidate.

My guess is that the rectifier you put in is getting hot. It is also loading the transformer (and drive circuitry) to the point of risking widespread expensive damage, so take out that rectifier now. It's effectively throwing a short circuit across the rest of the power supply. If you're going to stick in a bodge, stick in the particular bodge that I described: Three 1N4148 diodes in series.

--Cheersm
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 10/14/2020 08:38, Harrison wrote:
Tom; Thanks for the fine explanation and information. I followed most of your detailed guidance, but due to my weak theory background some went over my head. Currently, studying the books and the internet, I came to believe that a 1N4000 series rectifier diode was comparable and would work. I had some 1N4005 diodes in my junk bin so I installed one of those. From your perspective will that work or is it out of line with the specs you cite and I need to make the circuit perform as designed? I will say, with the 1N4005 installed I am still blowing a 1.6A fuse in F558. That is with the circuit intact with the exception of T550 pins 9 and 10 disconnected. The 95V TP reads 7.6V. The 32V, +5V and -5V all read as expected. The other issue I noticed is I have some funny readings on Q552 (100 Ohms to ground on the collector and base). But checking it out of circuit it checks out good. I keep good notes but I believe I am probably, again because of my theory level, "data rich and analysis poor".. I.E. I often don't see what I am seeing or understand what a measurement is telling me. Perhaps, in addition to the fun of it, trying to improve my understanding of theory is why I continue to chase my tail on this project. The scope is not my bench scope. It was a hand me down that If it goes south completely all is still well.
Harrison




Re: Obsolete Motorola IC

 

On Wed, Oct 14, 2020 at 06:32 PM, boid_twitty wrote:


All inputs 'high' to get a 'high' output sounds like 'positive logic'
AND, to me, too.

I'm guessing that ECL and 'positive logic' aren't obviously compatible
terms.
"High" and "Positive Logic" are not directly linked to the power supply being positive (like TTL, CMOS, PECL) or negative (like ECL, MECL, HECL) with respect to Ground but whether a logic "1" is associated with the more positive or the more negative voltage level.
IOW, in negative logic, a gate where the output is at its most negative only when all inputs are at their most negative level is an AND gate as well, just in negative logic.
IOW again, "positive" or "negative" logic indicates the choice in interpretation of voltage levels as "1" or "0" and as such is not dependent on logic family.
"Positive logic" and positive supply voltages are most common and convenient but nothing different by principle. Choices have been made for all common logic families.
With ordinary ECL, the logic voltages are more stable against the more positive supply rail than against the negative supply rail, so the noise margin is better if the logic voltage is interpreted against the positive supply rail. This is the main reason why normal ECL uses a positive ground.

Raymond


Re: Obsolete Motorola IC

Stephen Hanselman
 

Just to add a bit more paranoia. HP, in their 3000/6x,7x computers, used ECL for the high speed "ROM" memory. They did not use normal ROMs but loaded what they called Writable Control Store (WCS) from disc each time the computer was started. They told us (field CEs) that the two boards consisted of 100K ECL, as opposed to the 10K ECL in the rest of the CPU, which would blow up "with a cross look". Later they proved the smaller 4KB board was so sensitive that cosmic rays, yes it was "cosmic", caused the memory to forget what was stored in them.

You really have to use ALL of that bothersome anti-stat stuff or the chips will die

Steve

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Fabe via groups.io
Sent: Wednesday, October 14, 2020 9:55 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Obsolete Motorola IC

Isn't ECL (emitter coupled logic) is based in bipolar trannies and not CMOS? It's the HV of static electricity that breaks down those MOSFET oxide gates etc. The RCA 4000 series were simply terrible like that? Parasitic protective diodes where never used at that time (the '70's) and even today..... you don't rely on anyone to look over your shoulder.

One curse of death to avoid is to ever take anything lightly to ever use Styrofoam as an IC taxi station. That material is a static electricity hog! That's even when you see it wrapped up in tin foil. I learned as a tech..... only to have my nose rubbed in it,

For those thinking of EBay.... I got a few darts in the tail from buying factory rejects from China or parts improperly stored. Electronic replacement parts is ultimately a no return world.

Fabe

Fabian Hartery, B.Eng (Electrical)36 Chamberlains Road Conception Bay South, NL A1W 5E9, Canadafabian_hartery@yahoo.ca
tel: 709-834-3575


On Wednesday, October 14, 2020, 11:54:57 a.m. NDT, Jean-Paul <jonpaul@ix.netcom.com> wrote:

Beware all ECL is ESD suseptible, use static precautions


Jon


Re: Obsolete Motorola IC

Fabe
 

Isn't ECL (emitter coupled logic) is based in bipolar trannies and not CMOS? It's the HV of static electricity that breaks down those MOSFET oxide gates etc. The RCA 4000 series were simply terrible like that? Parasitic protective diodes where never used at that time (the '70's) and even today..... you don't rely on anyone to look over your shoulder.

One curse of death to avoid is to ever take anything lightly to ever use Styrofoam as an IC taxi station. That material is a static electricity hog! That's even when you see it wrapped up in tin foil. I learned as a tech..... only to have my nose rubbed in it,

For those thinking of EBay.... I got a few darts in the tail from buying factory rejects from China or parts improperly stored. Electronic replacement parts is ultimately a no return world.

Fabe

Fabian Hartery, B.Eng (Electrical)36 Chamberlains Road
Conception Bay South, NL
A1W 5E9, Canadafabian_hartery@yahoo.ca
tel: 709-834-3575

On Wednesday, October 14, 2020, 11:54:57 a.m. NDT, Jean-Paul <jonpaul@ix.netcom.com> wrote:

Beware all ECL is ESD suseptible, use static precautions


Jon


Re: Tektronix 2445 and 2445A not working for parts or repair

Bob Wilson
 

If you still have a 2445 please email me at rwilson@Hiwaay.net.

Bob


Re: 7623A Storage problem

Colin Herbert
 

OK, I have loosened/removed what I think are the correct screws/CRT base/anode connector/multipin connectors and the casing seems to be loose. However, it is proving to be a problem getting that whole assembly away from the HV board. I realise that the manual suggests care, to avoid damage to pin connectors and components, but does anyone who has experience of this have any hints as to how to go about it? Surely I cannot be the first to gain access to this HV board? It seems as though plug P1196 is nearly in view, but is being rather shy!

TIA, Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via groups.io
Sent: 12 October 2020 16:27
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7623A Storage problem

I am a bit puzzled as to how I gain access to Q1195 and other parts on the HV board. I can see where it is located on the shield of the HV compartment, but how do I get access to it? I have removed the A12 low-voltage regulator board and the fan assembly, but the manual then tells me to disconnect various things including the CRT base socket, the CRT anode plug and the multi-pin connectors on the A8 Z-axis board. It then says that there is one screw on the bottom of the high-voltage compartment and two screws at the top to release it from the chassis. Since the Z-axis board is still attached to the high-voltage compartment, as also is the A13 readout board, this puzzles me. I cannot see the screws which hold the high-voltage compartment in place and some of the multi-pin connectors on the Z-axis board are obscured by the casing of the scope. I can also see two high-voltage connections to the CRT, one on either side of the scope. Which one is the anode connector?
TIA again, Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Miguel Work
Sent: 25 September 2020 21:13
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7623A Storage problem

I remember that is mounted in the HV metallic shield/box



-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Colin Herbert via groups.io
Enviado el: viernes, 25 de septiembre de 2020 18:47
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] 7623A Storage problem

I have found that F814 (2A) on the LV power supply was blown and continues to do so, possibly because of a failure of Q1195 or C1198 (47uF). My question is how can I get to either of these components? I can see from the Manual that C1198 is on the HV board and that I might have to get in there to look at it. But Q1195 isn't on the HV board because it is heatsinked, but where is it located? I have a transistor checker and can thus check it out, if I can locate it.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roger Evans via groups.io
Sent: 23 September 2020 14:43
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7623A Storage problem

Colin,

I had the afterthought about low voltages since the regulation of the power transistor Q1195 relies on +5V, +15V and +130V being OK. The components I mentioned are all on the low voltage side of the transformer T1199 and can be checked with the power off. Q1195 is attached by a plug and socket so it can effectively be tested out of circuit, Q1190 can be checked as a pair of diodes for open circuit / short circuit. The two capacitors are likely to be short circuit if they have failed and L1198 will be open circuit if the fuse didn't do its job in time.

At least you don't have to wait 30 minutes for the high voltage to leak away!

Regards,

Roger


Re: Obsolete Motorola IC

boid_twitty
 

All inputs 'high' to get a 'high' output sounds like 'positive logic'
AND, to me, too.

I'm guessing that ECL and 'positive logic' aren't obviously compatible
terms.

I just follow the schematic, or truth table.

RL


Re: Air filters for big 500 series scopes

Keith
 

And if you want to use something a little snazzier for coating that air filter than a spray of PAM, may I suggest K&N filter oil? FWIW, K&N filter oil has a special extra-sticky agent in there that aggressively gathers dust, along with other nasty and probably carcinogenic stuff that keeps the gooey stuff gooey longer than PAM. One spray can of K&N costs about twice what a can of PAM costs, but since it is a specialized material you can tax deduct it as a bench supply/consumable item - which you probably can't with PAM.

One can of K&N costs $8.50 at Wally, and will last approximately two and a half lifetimes and you can use it on your lawnmower foam filter too.

Most importantly, PAM is safe and nontoxic. K&N on the other hand is dangerous, explosive when sprayed, possibly mutagenic and generally dangerous for the unskilled to handle. Of course this means it is probably also the very best choice for air filter oil. :-)

Here's the MSDS. http://kandn.com/msds/99-0516.pdf

But PAM will certainly work too. Just my 2C


Cheers,

Keith


Re: Tek 4654M; No Trace, No +5V, No +95V; Help

Harrison
 

Tom; Thanks for the fine explanation and information. I followed most of your detailed guidance, but due to my weak theory background some went over my head. Currently, studying the books and the internet, I came to believe that a 1N4000 series rectifier diode was comparable and would work. I had some 1N4005 diodes in my junk bin so I installed one of those. From your perspective will that work or is it out of line with the specs you cite and I need to make the circuit perform as designed? I will say, with the 1N4005 installed I am still blowing a 1.6A fuse in F558. That is with the circuit intact with the exception of T550 pins 9 and 10 disconnected. The 95V TP reads 7.6V. The 32V, +5V and -5V all read as expected. The other issue I noticed is I have some funny readings on Q552 (100 Ohms to ground on the collector and base). But checking it out of circuit it checks out good. I keep good notes but I believe I am probably, again because of my theory level, "data rich and analysis poor".. I.E. I often don't see what I am seeing or understand what a measurement is telling me. Perhaps, in addition to the fun of it, trying to improve my understanding of theory is why I continue to chase my tail on this project. The scope is not my bench scope. It was a hand me down that If it goes south completely all is still well.
Harrison


Re: Tektronix 2465A noise on readout

Gregor
 

Hi larry,

That's a good idea!
I uploaded all photos I took while the repair here:
https://groups.io/g/TekScopes/album?id=254966

And I also created a summary in pdf format and uploaded it here:
https://groups.io/g/TekScopes/files/Tektronix_2465A_noise_on_readout

-Gregor

On Tue, Oct 13, 2020 at 11:14 PM, Lawrance A. Schneider wrote:


This has been a lot of fun to follow.
I do not have a 2465A. I do have a 2465 and a 2465B. I hope you put your
photos and a summary on this site for future reference.

Thanks for the fun, larry


Re: Obsolete Motorola IC

Jean-Paul
 

Beware all ECL is ESD suseptible, use static precautions


Jon

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