Date   

Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

Good morning!
If you mean the time that the dot takes to cross the screen it seems about right for each settings.
5s for the .5 2 for the .2, 1 for the .1 and 2 for the EXT


Re: Tunnel diode pulses for calibration fixture

Tom Gardner
 

If you want to use discrete components, you could use the Tektronix 485 calibrator circuit, diagram 16 in the service manual. The output stage is rather strange, uses a 50V and 2N6314s,  supply, but achieves a clean 1ns risetime into 50 ohms - and a pleasing exponential staircase into 1Mohm :)

Alternatively use three parallel 74LVC1G*+143ohms with very good decoupling. That will drive 50ohms at <300ps transition time.

There are also several threads on EEVBlog forum, of course

On 08/06/21 05:24, Morris Odell wrote:
There are plenty of web pages on Emitter Coupled Multivibrators you can find with a Google search. One helpful page is https://cadernodelaboratorio.com.br/en/astable-multivibrator-with-a-single-capacitor/ . The ECM has the advantage of only needing one timing capacitor and that the second (output) transistor does not have to saturate so it can produce a faster transition. Also the output point at the collector of the second transistor does not drive any other part of the circuit so is not loaded or slowed down by it.

I used 2N2369 transistors in my lash up and easily obtained transitions too fast for my 50 MHz Tek 547/1A4 to measure.

If you want to find a comprehensive treatment, look no further than the classic "Pulse, Digital and Switching Waveforms" by Millman & Taub


Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

Strangely it seems that the .5s setting shows a readout of .2s, The .2s show .1s and .1 Is correct. (A bit confusing i know)
Frederico, you probably didn't check the non-store actual sweep speeds at .5s, .2s, .1s/div. You can check these slow speeds even without signal, 5s, 2s, 1s per full trace. EXT speed is also .2s/div.
Albert


Re: Rebuilt 7904A / 7L12 and bad Forum advice

 

Appreciate the repair notes. Agree that it's worth doing this right,
and that there's no reason to keep power supply capacitors "vintage".
We've all seen what happens when those "vintage" tantalums give up the
ghost. It's like taking a torch to the board. Have you considered
replacing the coax or the HV lead? How did you add new insulation onto
the HV lead?

Thanks

On Tue, Jun 8, 2021 at 3:45 AM David Campbell <k_8_b_y_p@ieee.org> wrote:

...and except for flaky ' drum' switch contacts..

PERFECT.
.
Scope picture- Perfect. Shows under- damped ringing on the Cal signal at
x00 MHz.

Full bay of plugins work perfectly. None of this
" power supply cant handle all the plugins..." nonsense.

SA perfect. No spurs whatsoever exc for 2.x L.O. and 2.4 GHz as expected,
and those are half the max. allowed level.

Coarse tuning on SA right on exc for wear in the dial mechanism.

All alignments that were checked were in spec.

Fortunately I ignored the BAD ADVICE from
" Forum Experts" here and replaced all the electrolytics in the mainframe
and all tantalums in the 7L12.

The worst advice was " youll risk damaging circuit boards" said by persons
who knew nothing about me.

Odd. No such thing happened. Those boards are very well made.

Maybe 50 years soldering experience, Manufacturing engineering and SMT
experience helped...And 15 years hi volume repair bench experience helped
as well...


Notes, and a couple unforgiveable, manufacturing errors found and fixed.

Compared to HP gear, this Tek looks like a High School class assembled it.

1. SIX ELECTROLYTICS in the scope leaking badly. One in the HV board under
rated (160V on a 130Vsupply) It was bulged and on its way to catastrophic
failure.

The 11th Commandment is:

" Thou shalt rate ' lytics at 2X WVDC!"

Tek didnt do it. Had I taken the advice of " Forum Experts" here, Id have
ended up with the typical
" power supply hand grenaded" situation.

2. Threaded Standoff too short in 7L12, badly warped A1300 board near the
large transistor. Standoff too short, the screw fastening the board to
standoff bent the board. Let the board relax, then put spacers between
board and standoff.

3. Large tantalum in 7L12, A1300 bd causing wires to be pinched. Replaced
all the old tants with new ones laid down, plenty of space to spare.

4. coax cable from A500 marker to front panel badly stretched. Poor
assembly work. Cable incorrectly routed.

5. HV multiplier in 7904 right up against grounded metal panel. If that HVM
starts to leak current and it finds an arc path to that shield, itll be
catastrophic destruction. Moved the board back and put a HV barrier
between. Saw lots of potted HVM fail this way in old TV sets.

6. Put extra insulation on the CRT HV lead. That wire insulation is 30
years old. Arcing can damage the HV board. HV lead was hanging down near
the switch and cal generator board causing interference. Poor assembly
work. HV lead much too long.

Recapping.

Easy to do, exc. for being multi layer boards, ONCE THE BOARDS ARE OUT.

Getting the boards out without damaging any wires, cables or headers is the
trick.

The buried power planes make great difficulty cleaning the PTHes out.
Solder wick wont work. Heat the PTH and stick a wooden bakers toothpick in
the hole. Push the molten solder thru.

30 watt iron on a variable voltage. Turn heat up and down as needed. This
was some of the easiest soldering Ive done bc of thick boards, well made
with plenty of copper. Youll have to try to damage these boards...but dont!

Tantalums. Cut one lead, unsolder the un- cut lead and remove component.
Then remove cut lead.

Electrolytics in the scope, not so easy. Cant cut one lead easily.

Power supply is not so static sensitive and is easily removable. Heat sink
mounted devices removed and old heat sink grease cleaned out and replaced.
Screws set with low strength Loctite so they cant loosen. DO NOT just shove
the PS assy. back in the chassis, move the cables if necessary so it slides
in easily without pressing on the boards behind the backplane.

DO NOT replace caps in a SMPS with caps not rated for high frequency
filtering. No junk from Jameco or hamfest.

Whomever wired this scope did a pathetic job of wiring routing.

Other boards in mainframe...DONT REMOVE THEM.

1. Static sensitive, custom ICs.

2. Flex ribbon connectors to CRT

3. Coax cables. Old plastic, formed in place over 30 years, dont bend them.

Replaced all the ' lytics without removing the boards. Not easy, but
eliminates much chance of damage.

7L12.

.DO NOT just pull center section out. Old wiring and cables dont like being
bent and twisted.

CAREFULLY pull the connectors off on A1100 and without bending the wiring,
slip the board out.

That gives access to A1300. Same with it..DO NOT bend wiring or coax
cables. One intermittent connection caused by torquing a cable will make
you pull your hair out....

Dont remove the other boards. No large filters on them. One cap on A1100
can be replaced from top side, cut the cap body off and solder new cap to
the leads.

Replace the three caps in the microwave area, 2.2 on the board with ICs and
two on the +/ - 15V supplies to the mixer block (mixer?).

DO NOT use electrolytics in the 7L12. They are tantalum for a reason!
Especially do not install tantalums backwards! Boom. Crying. Throwing
things.

Caps and polarity not marked on the boards. DO NOT power it up without
verifying polarity against schematic.

(Note: Recall.. NO SPURS in the SA display...none. .thats what new state of
the art filter caps buys! Clean power lines!)

DO NOT PUT OVER SIZED CAPS IN.( capacitance wise, over voltage is fine).
Highly experienced engineers sized them. Excess capacitance also means
higher pulse charging currents. No reason to do so and old connectors do
not need high currents.

Carefully break loose and reseat as many connectors as possible. No
twisting or bending.

STATIC SAFE WORKSTATION MANDATORY!!!!

Human body can generate 3Kv.

Manuals.

Unless its the manual for the SN range you have dont trust the parts list
for ordering caps.

Older 7L12 manual said front panel pots are fastened by swaged fittings.
Not on mine, had to remove front panel to access panel nuts. Manual said
electrolytic caps...not in mine- all tantalum. Alignment procedure for
vertical gain was wrong. Fairly minor details.

This scope and plugins were $20,000- ish , new cost. If it isnt worth
doing right, dont do it.

These are not ham radio toys. Word to the wise.


Any questions, Email me. Wont accept any more interference, or ignorant
lectures from supposed Forum Experts here that gave such bad advice.

k_8_b_y_p@IEEE.ORG





Re: Tunnel diode pulses for calibration fixture

Morris Odell
 

There are plenty of web pages on Emitter Coupled Multivibrators you can find with a Google search. One helpful page is https://cadernodelaboratorio.com.br/en/astable-multivibrator-with-a-single-capacitor/ . The ECM has the advantage of only needing one timing capacitor and that the second (output) transistor does not have to saturate so it can produce a faster transition. Also the output point at the collector of the second transistor does not drive any other part of the circuit so is not loaded or slowed down by it.

I used 2N2369 transistors in my lash up and easily obtained transitions too fast for my 50 MHz Tek 547/1A4 to measure.

If you want to find a comprehensive treatment, look no further than the classic "Pulse, Digital and Switching Waveforms" by Millman & Taub

Morris


Rebuilt 7904A / 7L12 and bad Forum advice

David Campbell <k_8_b_y_p@...>
 

...and except for flaky ' drum' switch contacts..

PERFECT.
.
Scope picture- Perfect. Shows under- damped ringing on the Cal signal at
x00 MHz.

Full bay of plugins work perfectly. None of this
" power supply cant handle all the plugins..." nonsense.

SA perfect. No spurs whatsoever exc for 2.x L.O. and 2.4 GHz as expected,
and those are half the max. allowed level.

Coarse tuning on SA right on exc for wear in the dial mechanism.

All alignments that were checked were in spec.

Fortunately I ignored the BAD ADVICE from
" Forum Experts" here and replaced all the electrolytics in the mainframe
and all tantalums in the 7L12.

The worst advice was " youll risk damaging circuit boards" said by persons
who knew nothing about me.

Odd. No such thing happened. Those boards are very well made.

Maybe 50 years soldering experience, Manufacturing engineering and SMT
experience helped...And 15 years hi volume repair bench experience helped
as well...


Notes, and a couple unforgiveable, manufacturing errors found and fixed.

Compared to HP gear, this Tek looks like a High School class assembled it.

1. SIX ELECTROLYTICS in the scope leaking badly. One in the HV board under
rated (160V on a 130Vsupply) It was bulged and on its way to catastrophic
failure.

The 11th Commandment is:

" Thou shalt rate ' lytics at 2X WVDC!"

Tek didnt do it. Had I taken the advice of " Forum Experts" here, Id have
ended up with the typical
" power supply hand grenaded" situation.

2. Threaded Standoff too short in 7L12, badly warped A1300 board near the
large transistor. Standoff too short, the screw fastening the board to
standoff bent the board. Let the board relax, then put spacers between
board and standoff.

3. Large tantalum in 7L12, A1300 bd causing wires to be pinched. Replaced
all the old tants with new ones laid down, plenty of space to spare.

4. coax cable from A500 marker to front panel badly stretched. Poor
assembly work. Cable incorrectly routed.

5. HV multiplier in 7904 right up against grounded metal panel. If that HVM
starts to leak current and it finds an arc path to that shield, itll be
catastrophic destruction. Moved the board back and put a HV barrier
between. Saw lots of potted HVM fail this way in old TV sets.

6. Put extra insulation on the CRT HV lead. That wire insulation is 30
years old. Arcing can damage the HV board. HV lead was hanging down near
the switch and cal generator board causing interference. Poor assembly
work. HV lead much too long.

Recapping.

Easy to do, exc. for being multi layer boards, ONCE THE BOARDS ARE OUT.

Getting the boards out without damaging any wires, cables or headers is the
trick.

The buried power planes make great difficulty cleaning the PTHes out.
Solder wick wont work. Heat the PTH and stick a wooden bakers toothpick in
the hole. Push the molten solder thru.

30 watt iron on a variable voltage. Turn heat up and down as needed. This
was some of the easiest soldering Ive done bc of thick boards, well made
with plenty of copper. Youll have to try to damage these boards...but dont!

Tantalums. Cut one lead, unsolder the un- cut lead and remove component.
Then remove cut lead.

Electrolytics in the scope, not so easy. Cant cut one lead easily.

Power supply is not so static sensitive and is easily removable. Heat sink
mounted devices removed and old heat sink grease cleaned out and replaced.
Screws set with low strength Loctite so they cant loosen. DO NOT just shove
the PS assy. back in the chassis, move the cables if necessary so it slides
in easily without pressing on the boards behind the backplane.

DO NOT replace caps in a SMPS with caps not rated for high frequency
filtering. No junk from Jameco or hamfest.

Whomever wired this scope did a pathetic job of wiring routing.

Other boards in mainframe...DONT REMOVE THEM.

1. Static sensitive, custom ICs.

2. Flex ribbon connectors to CRT

3. Coax cables. Old plastic, formed in place over 30 years, dont bend them.

Replaced all the ' lytics without removing the boards. Not easy, but
eliminates much chance of damage.

7L12.

.DO NOT just pull center section out. Old wiring and cables dont like being
bent and twisted.

CAREFULLY pull the connectors off on A1100 and without bending the wiring,
slip the board out.

That gives access to A1300. Same with it..DO NOT bend wiring or coax
cables. One intermittent connection caused by torquing a cable will make
you pull your hair out....

Dont remove the other boards. No large filters on them. One cap on A1100
can be replaced from top side, cut the cap body off and solder new cap to
the leads.

Replace the three caps in the microwave area, 2.2 on the board with ICs and
two on the +/ - 15V supplies to the mixer block (mixer?).

DO NOT use electrolytics in the 7L12. They are tantalum for a reason!
Especially do not install tantalums backwards! Boom. Crying. Throwing
things.

Caps and polarity not marked on the boards. DO NOT power it up without
verifying polarity against schematic.

(Note: Recall.. NO SPURS in the SA display...none. .thats what new state of
the art filter caps buys! Clean power lines!)

DO NOT PUT OVER SIZED CAPS IN.( capacitance wise, over voltage is fine).
Highly experienced engineers sized them. Excess capacitance also means
higher pulse charging currents. No reason to do so and old connectors do
not need high currents.

Carefully break loose and reseat as many connectors as possible. No
twisting or bending.

STATIC SAFE WORKSTATION MANDATORY!!!!

Human body can generate 3Kv.

Manuals.

Unless its the manual for the SN range you have dont trust the parts list
for ordering caps.

Older 7L12 manual said front panel pots are fastened by swaged fittings.
Not on mine, had to remove front panel to access panel nuts. Manual said
electrolytic caps...not in mine- all tantalum. Alignment procedure for
vertical gain was wrong. Fairly minor details.

This scope and plugins were $20,000- ish , new cost. If it isnt worth
doing right, dont do it.

These are not ham radio toys. Word to the wise.


Any questions, Email me. Wont accept any more interference, or ignorant
lectures from supposed Forum Experts here that gave such bad advice.

k_8_b_y_p@IEEE.ORG


Problems with my tek 492BP

fring050@...
 

Hello,
I got some troubles with my TEK 492BP (B020153).
During investigations i have 2 questions:
1) how can i activate my 10 MHZ reference connected source (switching from internal to external)?
2) In the service manual Vol. 1 for the 492AP/BP i find the following string for looking at the LO 1 state => <BLUE > <SHIFT> <EXT>
This gives the error "no macro is stored at selected number". That make sense because because <BLUE > <SHIFT> markings near my front panel EXT button is talking about macro's. Could it be that the service manual is not the right one for my SA or is it just my user error?
Thanks Ben


Re: Tunnel diode pulses for calibration fixture

durechenew@...
 

Some details about the emitter coupled multivibrator; transistors options ? This might be a better solution, considering possibilities for parameters adjustment
TT


Re: Tunnel diode pulses for calibration fixture

Morris Odell
 

Hi Gerald,

You will find a description of a Tek TD pulser at: https://w140.com/tekwiki/wiki/067-0681-01

As an alternative I have achieved pretty fast risetimes with an emitter coupled multivibrator using 2N2369 transistors built on a copper ground plane - there are probably faster transistors available now.

Tunnel diodes are indeed fragile but you don't need to go to extremes. They are not MOS devices. Commercial packaging in the 1960's was just like for any other component.

Also, I believe you can still buy affordable Russian TD's on the e place if you want to experiment with them.

Good luck,

Morris VK3DOC


Re: Another 7D20 attenuator question

Bob Headrick
 

This is an old thread, but I just got a 7D20 with attenuator issues on Ch1. Dallas - you mention you polished the substrate pads.. What did you use for polishing? I do not want to damage the substrate.

- Bob Headrick


Re: 2465 Blank screen when warm

david
 

Needs horizontal calibrated
David


Re: 2465 Blank screen when warm

david
 

I got a used U800 from Ebay, Installed it in a socket and put stainless spacers under chip on screws. Scope is working now but needs horizontal. Is it OK to just do the horizontal Calibration and stop there? Don't have equipment to do vertical.
David


Re: TEK576 looking for repair parts

 

The vintageTEK Museum has a 576 parts unit. We could sell you the whole 5-resistor assembly. Contact us at contactus@vintagetek.org to arrange.



--
Bob Haas


Photo Notifications #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

Shaun M <shaun_merrigan@...> added the album Type 114 Refresh: Images of repair/refresh of a couple of Type 114 Pulse Generators


The following photos have been uploaded to the Type 114 Refresh album of the TekScopes@groups.io group.

By: Shaun M <shaun_merrigan@...>


Added Folder /Type 114 Refresh #file-notice

TekScopes@groups.io Notification <noreply@...>
 

Shaun M <shaun_merrigan@...> added folder /Type 114 Refresh


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

At 0.1 s/div i have -8.57v at pin 1 and 3.27v at pins 2 and 13, unfortunately pin 6 of U781 is in the worst position (timing cap in front of it and a weighted resistor behind) and so not accessible at all...
Strangely it seems that the .5s setting shows a readout of .2s, The .2s show .1s and .1 Is correct. (A bit confusing i know)
What a mess
Federico
PS since you lured me into it... I've just won a bid for a nice X10 Philips probe :)


Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

U780/13 tested 3.2v aswell and U781/1 -8.53v (odd?)
So to summarize, U780/1 and U781/1 were -8.5 V, U780/2 and U780/13 were +3.2 V. That's exactly correct for the setting 0.1 s/div, but not for EXT. Are you sure you set EXT? If so, what happens at 0.1 s/div?
In EXT position U781/6 should be far negative, but U781/1 at -8.5 V suggests that U781/6 must be +0.7 V. Could you measure U781/6?
Albert


Added lots of hard to find FETs and MOSFETs to the Stuff page.

 

So many people have been chasing hard to find FETs recently that I spent some time digging though all our semi inventory, and posted up the ones I thought might be useful for fixing test gear and RF items. You can see them here on the stuff day page:

https://www.sphere.bc.ca/test/stuffday.html#fets

I have put the Tek parts there too (and I have more to post this week, also HP parts). I will try and make sure there is a rich assortment there to look through. I also added three interesting FET substitution guides at the top of the section, to help you find a replacement for that toasted part. There are 2N4000/500 series parts, J-series parts, and M-series parts, plus Tek 151-1xxx parts so far. I also have siliconix ultra low leakage current diodes and CL diodes I will add in shortly.

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.
https://www.sphere.bc.ca/test/index.html


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

U780/13 tested 3.2v aswell and U781/1 -8.53v (odd?)


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

R6441 and C6441 tested OK actually C6441 was already been replaced few days ago.
I feel like i have the fault under my nose....

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