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Re: S-52 only works with lowered +15 V power supply

 

Just discovered that R27 on the schematic is 510 ohm: on the board there a 2.0 kohm is mounted instead.
My timing board has the code number 670-1320-02 so I don't have the latest schematic. I bought mine from Dave's Artekmedia and it references the 670-1320-00 version of the pcb with only two schematic changes/additions (R60 and CR10).
Moreover: the voltages -2.5V and -3V, they vary if the + 15V varies, changing the operating point of BJTs. The -5.1 V is rock- steady.
The waveform at the point "E" is very critical.
Blowing some compressed air in the zone around R26 / 27 / 30/37 the pulse width at pin "E" (positive pulse at right of waveform 10) changes noticeably, influencing the width of TD pulse.
I'm reaaaaally puzzled.

Max
Re: S-52 only works with lowered +15 V power supply

 

Probably to decrease parasitic inductance on the power and ground pins.? Wirebonds make great inductors, and as the edge speeds increased, ground and power bounce became a problem.? V = L*di/dt.? I assume the power and ground pins went to the center of the package.? Corner pins are the worst possible choice for inductance.Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Harvey White <madyn@...> Date: 7/4/20 12:47 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] S-52 only works with lowered +15 V power supply 74L series of chips should be checked for pin compatibility with anything else.? Not sure why they did that, but that's been a design problem for any number of years when substituting.Also, not all 7400 series chips have power and ground at 14/7 or 16/8.? Surprise....HarveyOn 7/4/2020 2:21 PM, unclebanjoman wrote:> While checking the circuit I just discover that SN74L93 and SN74LS93 are NOT pin-to-pin compatible!> I was using the "classical" 7493 datasheet from Texas Instruments datasheet and wondering how it worked ...> I never imagined that the 74L93 had a different pinout! I found the correct pin-out in a very old National databook.>> Max>> >>
Re: S-52 only works with lowered +15 V power supply

 

74L series of chips should be checked for pin compatibility with anything else.? Not sure why they did that, but that's been a design problem for any number of years when substituting.

Also, not all 7400 series chips have power and ground at 14/7 or 16/8.? Surprise....

Harvey

On 7/4/2020 2:21 PM, unclebanjoman wrote:
While checking the circuit I just discover that SN74L93 and SN74LS93 are NOT pin-to-pin compatible!
I was using the "classical" 7493 datasheet from Texas Instruments datasheet and wondering how it worked ...
I never imagined that the 74L93 had a different pinout! I found the correct pin-out in a very old National databook.

Max
Re: S-52 only works with lowered +15 V power supply

 

That is true for other 74 series.? Should always check pinout.? Example, 74L,LS,W: 95, 85, 78, 72, 74 and maybe others.
Carl Hallberg (W9CJH)

On Saturday, July 4, 2020, 1:21:11 PM CDT, unclebanjoman <mmazza@...> wrote:





While checking the circuit I just discover that SN74L93 and SN74LS93 are NOT pin-to-pin compatible!
I was using the "classical" 7493 datasheet from Texas Instruments datasheet and wondering how it worked ...
I never imagined that the 74L93 had a different pinout! I found the correct pin-out in a very old National databook.

Max
Re: S-52 only works with lowered +15 V power supply

 

While checking the circuit I just discover that SN74L93 and SN74LS93 are NOT pin-to-pin compatible!
I was using the "classical" 7493 datasheet from Texas Instruments datasheet and wondering how it worked ...
I never imagined that the 74L93 had a different pinout! I found the correct pin-out in a very old National databook.

Max
Re: S-52 only works with lowered +15 V power supply

 

Work still in progress.
Yesterday I put a normal metal film resistor in parallel with the other two (R65/R68). Measured total resistance now is 1,33 ohm. OK.
Behavior is almost unchanged. With +15 V on the positive supply the main pulse appears only with R90 fully CW.
A strange thing I noticed: with the unit just powered up the pulse width initially is approx 500 ns or so.
While the unit warms up, the pulse width gradually decreases until it disappears completely after 1 or two minutes.
To make it reappear I have to decrease the supply to 14.5 V.
Suspecting some thermal drift, I tried to blow (with my breath) over the zone around R109 ( the resistor in series with the 5.1 V zener): the pulse reappears except to shrink in duration and then disappear again within 30 sec.
Oh yeah, in that pcb zone there are the resistors R106,R107 and R108 which generates the -3 V and - 2.5 V reference voltages. Measured, they are 3.1 and -2.6 respectively.

I don't think Tek made such a critical temperature circuit. I suppose that the optimal operating conditions are reached after a few minutes of warm-up and that the engineers have taken into account the heating produced by the 85 ohm resistor for the zener polarization.
Resistor values in the circuit area around Q86, Q88, Q80 are all in the range.

I will patiently check all the waveforms by comparing them with those shown on the diagram and I will check the voltage values on the basis of Q86 and Q88 also.

Varying the voltage between 13 and 15.5 V I noticed another phenomenon: the DURATION of the main pulse first decreases, then abruptly increases and then decreases again until it disappears completely at 15.1 / 15.2 V. Seems to be a timing problem, just like Albert said.
To better describe this phenomenon, a video would be needed. If I can do it, I'll upload it on the TekScopes forum.

Max
Re: 7603 HV oscillator doesn¡¯t start up

 

It isn't that they were selected, the 2N3055 devices at the time were all homotaxial and had low beta compared to more modern versions.

Even with this in play some HV circuits were cranky and wouldn't do well with very low and very high betas.

Look for a 150-0140-xx with a beta in the range of approx 20-50.

We fought this in the B Phase of the 611 and I'm familiar with the problem.

Rolynn
Tek Bvtn and Sunset 1966-1971
Re: Wikipedia is not an appropriate topic for TekScopes. WAS repair tools: Autotransformers/variacs

 

On Fri, Jul 3, 2020 at 04:59 PM, nonIonizing EMF wrote:


Thinking I can make a Tekwiki wiki on Wikipedia
I'm against it.
We've got the curated (and excellent) Tekwiki.
Marketing campaigns don't belong on any of the wikis.
Re: Tektronix 2230

 

Hi Bert
OK it means in my case t906.
Do you have the schematic for 2230 so that we can confirm the transformer.
Thanks.

On Sat, Jul 4, 2020, 9:12 AM Bert Haskins <bhaskins@...> wrote:


On 7/3/2020 9:50 PM, Saroj Pradhan wrote:
Hi Bert
Thanks for your concern and suggestion.

But it operates normally with external power supply (in my case I used
38v
dc across tp950 and tp940).

Saroj
No, I mean the HV supply, the one that runs off the input AC and
supplies the +40V.

Shorted turns make it draw too much current.




On Sat, Jul 4, 2020, 1:28 AM Bert Haskins <bhaskins@...>
wrote:

On 7/2/2020 8:51 PM, Saroj Pradhan wrote:
Hi Leo
No worry. It happens.
Sure I will check the component.
I confirmed that the scope is still working with external supply.
But before going further I want share with you my experience during the
testing of scope with limiter bulb.
1. That day you suggested to put on the scope without limiter bulb. And
you know the outcome.
2.It seems that even with shorted q9070
I could hear the same high pitch(with limiter bulb lighting)
3 changed q9070 and put on the scope(with limiter bulb). This time I
had
flashing light and there was power led at front panel also flashing.
And I
could hear the pitch at the same frequency as of bulb or led flashing.

Put off the scope. Again put on the scope with same result. Third time
when I put on the scope q9070 damaged again. Any logic behind this?
Thanks.
Saroj
First, let me say that I have several 223x family scopes and had very
few problems with them.

I did have a 2215A that uses a similar power supply that gave me fits
until I finally figured out that the high voltage transformer had
shorted windings.

I proved this to myself by doing a ringing test after removing the
transformer.

Good luck,

Bert
Re: Tektronix 2230

 

On 7/3/2020 9:50 PM, Saroj Pradhan wrote:
Hi Bert
Thanks for your concern and suggestion.

But it operates normally with external power supply (in my case I used 38v
dc across tp950 and tp940).

Saroj
No, I mean the HV supply, the one that runs off the input AC and supplies the +40V.

Shorted turns make it draw too much current.




On Sat, Jul 4, 2020, 1:28 AM Bert Haskins <bhaskins@...> wrote:

On 7/2/2020 8:51 PM, Saroj Pradhan wrote:
Hi Leo
No worry. It happens.
Sure I will check the component.
I confirmed that the scope is still working with external supply.
But before going further I want share with you my experience during the
testing of scope with limiter bulb.
1. That day you suggested to put on the scope without limiter bulb. And
you know the outcome.
2.It seems that even with shorted q9070
I could hear the same high pitch(with limiter bulb lighting)
3 changed q9070 and put on the scope(with limiter bulb). This time I had
flashing light and there was power led at front panel also flashing. And I
could hear the pitch at the same frequency as of bulb or led flashing.

Put off the scope. Again put on the scope with same result. Third time
when I put on the scope q9070 damaged again. Any logic behind this?
Thanks.
Saroj
First, let me say that I have several 223x family scopes and had very
few problems with them.

I did have a 2215A that uses a similar power supply that gave me fits
until I finally figured out that the high voltage transformer had
shorted windings.

I proved this to myself by doing a ringing test after removing the
transformer.

Good luck,

Bert
Re: Tektronix 2230

 

Hi Bert
Thanks for your concern and suggestion.

But it operates normally with external power supply (in my case I used 38v
dc across tp950 and tp940).

Saroj

On Sat, Jul 4, 2020, 1:28 AM Bert Haskins <bhaskins@...> wrote:


On 7/2/2020 8:51 PM, Saroj Pradhan wrote:
Hi Leo
No worry. It happens.
Sure I will check the component.
I confirmed that the scope is still working with external supply.
But before going further I want share with you my experience during the
testing of scope with limiter bulb.
1. That day you suggested to put on the scope without limiter bulb. And
you know the outcome.
2.It seems that even with shorted q9070
I could hear the same high pitch(with limiter bulb lighting)
3 changed q9070 and put on the scope(with limiter bulb). This time I had
flashing light and there was power led at front panel also flashing. And I
could hear the pitch at the same frequency as of bulb or led flashing.


Put off the scope. Again put on the scope with same result. Third time
when I put on the scope q9070 damaged again. Any logic behind this?
Thanks.
Saroj
First, let me say that I have several 223x family scopes and had very
few problems with them.

I did have a 2215A that uses a similar power supply that gave me fits
until I finally figured out that the high voltage transformer had
shorted windings.

I proved this to myself by doing a ringing test after removing the
transformer.

Good luck,

Bert
Re: Wikipedia is not an appropriate topic for TekScopes. WAS repair tools: Autotransformers/variacs

Chuck Harris
 

<>

nonIonizing EMF wrote:

Would be nice if more Tektronix related information was on Wikipedia. Thinking I can make a Tekwiki wiki on Wikipedia and maybe add on the Tektronix Wikipedia Wiki also. Looks like the following "Tektronix Analog Oscilloscopes" wiki does link to Tekwiki and more:


I made this update for the edge connectors that I'm thinking I can elaborate on too for more Tektronix and maybe other gear. I'm new to all this, though notice the use in other gear too.


Please note if I'm missing anything pertinent and/or questions, comments and/or suggestions. Thanks for sharing!
Re: Wikipedia is not an appropriate topic for TekScopes. WAS repair tools: Autotransformers/variacs

 

Would be nice if more Tektronix related information was on Wikipedia. Thinking I can make a Tekwiki wiki on Wikipedia and maybe add on the Tektronix Wikipedia Wiki also. Looks like the following "Tektronix Analog Oscilloscopes" wiki does link to Tekwiki and more:


I made this update for the edge connectors that I'm thinking I can elaborate on too for more Tektronix and maybe other gear. I'm new to all this, though notice the use in other gear too.


Please note if I'm missing anything pertinent and/or questions, comments and/or suggestions. Thanks for sharing!
Re: Tektronix 2230

 

On 7/2/2020 8:51 PM, Saroj Pradhan wrote:
Hi Leo
No worry. It happens.
Sure I will check the component.
I confirmed that the scope is still working with external supply.
But before going further I want share with you my experience during the testing of scope with limiter bulb.
1. That day you suggested to put on the scope without limiter bulb. And you know the outcome.
2.It seems that even with shorted q9070
I could hear the same high pitch(with limiter bulb lighting)
3 changed q9070 and put on the scope(with limiter bulb). This time I had flashing light and there was power led at front panel also flashing. And I could hear the pitch at the same frequency as of bulb or led flashing.


Put off the scope. Again put on the scope with same result. Third time when I put on the scope q9070 damaged again. Any logic behind this?
Thanks.
Saroj
First, let me say that I have several 223x family scopes and had very few problems with them.

I did have a 2215A that uses a similar power supply that gave me fits until I finally figured out that the high voltage transformer had shorted windings.

I proved this to myself by doing a ringing test after removing the transformer.

Good luck,

? Bert
Re: Tek 564 on DFW Craigslist for cost + shipping [taken]

 

Ok, but by who? You?
Colin.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Oz-in-DFW
Sent: 03 July 2020 16:28
To: [email protected]
Subject: Re: [TekScopes] Tek 564 on DFW Craigslist for cost + shipping [taken]

as the subject says, taken.
Re: Tek 564 on DFW Craigslist for cost + shipping [taken]

 

as the subject says, taken.
7603 HV oscillator doesn¡¯t start up

C G
 

Assembly: CRT Circuit (8)
New el. caps.
Transistors checked with multimeter (don¡¯t own a working curve tracer until the said 7603 is repaired. So stupid!). Read that TO-3 are factory selected and must have low gain, right?u

Mainframe power supply restored. All voltage checked within tolerances.

Any ol¡¯timer clue?

Christian
Re: Tek 564 on DFW Craigslist for cost + shipping

 

I am interested in the scope. I have a Fedex account, so if you can drop it off at one of their locations I can take care of the shipping costs from my end. I have a specific use for the scope and it would do the job very well. Thanks, Bruce Gentry KA2IVY

On 7/3/20 9:31 AM, Oz-in-DFW wrote:
I don't need it, but I figure I'll rescue it later today as I'll be in that neighborhood. He wants $25. You can have it for that plus whatever actual shipping is to you. I'll box it up and weigh it as soon as I get a chance. Probably this weekend.
Tek 564 on DFW Craigslist for cost + shipping

 

I don't need it, but I figure I'll rescue it later today as I'll be in that neighborhood. He wants $25. You can have it for that plus whatever actual shipping is to you. I'll box it up and weigh it as soon as I get a chance. Probably this weekend.

Re: 475 questions

 

Hi Bruce,
Don't get discouraged by your initial problems and spectacular fireworks. Do you have phone with an camera? Sometimes the more experienced techs can spot what is wrong from pictures. It might be helpful to document the areas you worked on.
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