Date   

Re: loosing knob markings. Any hope ?

Dave Daniel
 

I forgot about those - I used them for making front panels. I would put the letters on, then spray with clear lacquer, let it cure and then bake the panels briefly. For buttons, one could spray some "Workable Fixatif" or matte lacquer to fix the letters and provide additional resistance to the letters rubbing off. I hadn't though of that until just now.

DaveD


On Thu, Apr 11, 2013 at 10:55 AM, Ed Breya <edbreya@...> wrote:
 

Remember dry-transfer lettering sheets? I don't know if any are still made, but modern and better equivalents probably are - I'll have to check out that website - good info.

I still have many of those old-school sheets - some over 40 years old. Unfortunately, after many years, the waxy letter material deteriorates and won't work anymore - I don't know if mine are still good. I've used them to make instrument panels and documents since I was a kid - way before PCs and printers. They're good for small projects and repairs.

Ed



--- In TekScopes@..., "pa7rg" wrote:
>
> Although I never used it, I would try transfer decal print paper:
> http://www.youtube.com/watch?v=d8XuJ0Z3bbQ
> http://www.decalpaper.com/default.asp or something.
>
>
> Robert
>
>
> --- In TekScopes@..., ct1dmk <ct1dmk@> wrote:
> >
> > Hello,
> >
> > My beloved 76xx (have two) scopes are losing the black letters on their
> > knobs.
> > one of them I was just dusting it off (dry fine brush) and letter just
> > gone like fine powder... (or became attached to my finger when I pressed
> > a knob)
> > :-( :-( :-(
> >
> > Is there any nice way to apply new letters etc... or is doomed for ever ?
> >
> > can I leave it without any markings or maybe ugly hand written letters
> > if I have the courage... hummm.... sad day for me... tek wise.
> >
> > Luis Cupido
> > ct1dmk.
> >
>




--

------------------------
Dave (Nick) Daniel
KC0WJN
------------------------


Re: loosing knob markings. Any hope ?

Ed Breya
 

Remember dry-transfer lettering sheets? I don't know if any are still made, but modern and better equivalents probably are - I'll have to check out that website - good info.

I still have many of those old-school sheets - some over 40 years old. Unfortunately, after many years, the waxy letter material deteriorates and won't work anymore - I don't know if mine are still good. I've used them to make instrument panels and documents since I was a kid - way before PCs and printers. They're good for small projects and repairs.

Ed

--- In TekScopes@..., "pa7rg" <robert.pa7rg@...> wrote:

Although I never used it, I would try transfer decal print paper:
http://www.youtube.com/watch?v=d8XuJ0Z3bbQ
http://www.decalpaper.com/default.asp or something.


Robert


--- In TekScopes@..., ct1dmk <ct1dmk@> wrote:

Hello,

My beloved 76xx (have two) scopes are losing the black letters on their
knobs.
one of them I was just dusting it off (dry fine brush) and letter just
gone like fine powder... (or became attached to my finger when I pressed
a knob)
:-( :-( :-(

Is there any nice way to apply new letters etc... or is doomed for ever ?

can I leave it without any markings or maybe ugly hand written letters
if I have the courage... hummm.... sad day for me... tek wise.

Luis Cupido
ct1dmk.


Re: TEK 532 --

Tim Phillips <tim@...>
 

from Tim P (UK)
I think that is a single-shot option - the original 532 didn't have one.
Some of them may have had P7 phosphors - the 'scope was popular
in the BioMed / Engineering fields, where 5MHz was plenty.
The Delayed  Gate was useful for driving Stimulators.
Tim
 

----- Original Message -----
Sent: Thursday, April 11, 2013 4:51 PM
Subject: Re: [TekScopes] Re: TEK 532 --

 

One other thing I just noticed: yours has a extra toggle switch below the external horizontal input, and what looks like an extra light above it. What do those labels say for those two? Mine has neither, but is still a P11.


Respectfully,
Cliff White, W5CNW
w5cnw@...
On 04/10/2013 10:14 PM, Cliff White wrote:
 

Mine's also blue, probably P11, and only says "532" w/o the 57. Strange.



On 04/10/2013 10:12 PM, d.sligar wrote:
 

I'm not sure exactly what the "57" represents, but I think at least part of it specifies the phosphor -- which, I believe, is a longer persistence type. Note the blue color.

David

--- In TekScopes@..., Cliff White wrote:
>
> Question: Why does his scope say "Type 532-57"? My 532 just says "Type
> 532"... ?
>
>
> On 04/10/2013 03:30 PM, Steve wrote:
> >
> > --- In TekScopes@... ,
> > David Sligar wrote:
> > >
> > > Hello, Group --
> > >
> > > As possibly many new members do, my first post is a plea for help.
> > Once my very nice 532 is working again, I might decide that I prefer
> > "reliable" to "elegant" -- and trade this one in for something a
> > little newer.
> > >
> > >
> > > I've been using this scope on a daily basis for about a month. On
> > Friday morning I tuned it on and suddenly -- no sweep. I've been
> > going through the beast as carefully
> > > as I can, looking for the bug.
> > > Tubes all check good, no visible damage / exceptions, "all" voltages
> > measure
> > > correctly. I suspect one might need a (working) scope to figure out
> > > where the sweep waveform disappears. I decided I'd try running my
> > > function generator as external sweep -- it worked, so that says at
> > least
> > > the horiz. amp is OK. I've now spent a couple of days
> > > and I'm not sure I'll be able to find what's wrong.
> > >
> > > Amazing how helpless we are without tools! I hope one or more of you
> > will be able to suggest where I should look.
> > >
> > > Thanks very much,
> > > David Sligar
> > > Grants Pass, OR
> >
> > David,
> >
> > A second scope would be very helpful, but you may be able to do some
> > things without it. Selecting a very slow sweep speed (1 div/sec) would
> > allow you so see the sawtooth on a DMM.
> >
> > First you need to isolate the main area not working. It could be at
> > least three -- trigger, timebase, or blanking. Turning the Trigger
> > Stability control to the far right should force the scope to free run.
> > This does not isolate the trigger circuit however. It only biases the
> > multivibrator in a way to have it reset when the sweep length
> > comparator trips at the end of the sweep.
> >
> > With another scope, you can trace all of the trigger circuit fairly
> > easily. I usually use line trigger mode when doing this, as I know
> > this gives a reliable signal, eliminating the possibility of a problem
> > in the trigger pickoff circuit in the plug-in. Trace the signal
> > through the comparator(V308), and verify the Trigger level control
> > moves the grid voltage around (pin 9 for all + polarity settings, pin
> > 2 for all -- mode positions).
> >
> > I was hoping to disable the unblanking pulse to rule that out, but I
> > don't see a way to do that simply by pulling tube, as the signal is
> > generated in a dual triode (V430B) that is shared with the trigger
> > multivibrator. Unfortunately, the AC coupling to differentiate the
> > pulse occurs before these tube stages, so there is no place you can
> > easily short to ground or a supply to get a stable DC bias voltage.
> >
> > If the trigger is going through OK, then you need to focus on the time
> > base. Use the circuit description in the manual to guide your
> > troubleshooting.
> >
> > Let us know your progress. Your scope looks really clean and is worth
> > preserving.
> >
> > - Steve
> >
> > >
> >
> >
>




Free for postage 200C Scope mobile manual

Artekmedia <manuals@...>
 

Title says it all, includes parts lists and exploded assembly drawing

USA postage will be $.66 folded in a legal envelope or $1.52 laid flat in a large...Paypal payment add $.50

International about $1.50 more

Dave
ArtekManuals

--
Dave Henderson
Manuals@...
www.Artekmanuals.com
PO Box 175
Welch,MN 55089
651-269-4265


Re: loosing knob markings. Any hope ?

pa7rg <robert.pa7rg@...>
 

Although I never used it, I would try transfer decal print paper:
http://www.youtube.com/watch?v=d8XuJ0Z3bbQ
http://www.decalpaper.com/default.asp or something.


Robert

--- In TekScopes@..., ct1dmk <ct1dmk@...> wrote:

Hello,

My beloved 76xx (have two) scopes are losing the black letters on their
knobs.
one of them I was just dusting it off (dry fine brush) and letter just
gone like fine powder... (or became attached to my finger when I pressed
a knob)
:-( :-( :-(

Is there any nice way to apply new letters etc... or is doomed for ever ?

can I leave it without any markings or maybe ugly hand written letters
if I have the courage... hummm.... sad day for me... tek wise.

Luis Cupido
ct1dmk.


Re: How many oscilloscopes a gentleman should have?

Artekmedia <manuals@...>
 

Then there is the old axiom ..."He who dies with the most toys wins !"

Dave
ArtekManuals
(I only own 6 scopes but I will bet I actually own more manuals than the rest of you combined)

On 4/11/2013 11:29 AM, Ed Breya wrote:
 

The correct answer is: Enough to satisfy the need, plus some spares.

For this type of situation, the "exact" number can be determined analytically by using the 2nd order Lipshitz Hoarding Equation of the Fourth Kind (from Lipshitz, J. L., "Mathematical Analysis and Modeling of Human Behaviour," Kensington-Trent, 1971). Chapter 12, "The Acquisition and Hoarding Instinct," explains it in depth.

It won't do much good though, unless you can accurately assess the two-dozen or so coefficients involved, which depend mostly on characteristics of the population and the individual, and the rest on the environment. It can get rather complicated, and even then, only gives a statistical answer - an exact mean number, but with a standard deviation that can be quite large.

The "fourth kind" of the equation allows for non-integer and negative values, so even partial or non-working scopes could be considered - BUT - it gets so complicated it's hardly worth the effort over the discrete version "third kind." Just for the hell of it, I tried both, using self-assessed coefficients. I couldn't even get an answer from the continuous version, but with the discrete, I came up with 37 units with sigma 11 for myself.

So, after all that, I'd recommend my first answer above, and not worry about the numbers.

Ed

--- In TekScopes@..., Mark Wendt wrote:
>
> On 04/10/2013 02:12 PM, vdonisa wrote:
> > Question inspired from the 532 thread - what's the optimal number of oscilloscopes a gentleman should have?
> >
> > I know there's a minimum of 2 - so you can repair the troubled one - and I've seen as much as 6 (pretty crowded place, the owner used to have at least 4 pieces of each type of equipment).
> >
> > What's your "optimal" number?
> >
> > Valentin :-)
>
> Till you have no more room for more? I've got 5 working and 1 dead with
> CRT issues and 1 more k-ball unit.
>
> Mark
>


-- 
Dave Henderson
Manuals@...
www.Artekmanuals.com
PO Box 175
Welch,MN 55089
651-269-4265


Re: How many oscilloscopes a gentleman should have?

Ed Breya
 

The correct answer is: Enough to satisfy the need, plus some spares.

For this type of situation, the "exact" number can be determined analytically by using the 2nd order Lipshitz Hoarding Equation of the Fourth Kind (from Lipshitz, J. L., "Mathematical Analysis and Modeling of Human Behaviour," Kensington-Trent, 1971). Chapter 12, "The Acquisition and Hoarding Instinct," explains it in depth.

It won't do much good though, unless you can accurately assess the two-dozen or so coefficients involved, which depend mostly on characteristics of the population and the individual, and the rest on the environment. It can get rather complicated, and even then, only gives a statistical answer - an exact mean number, but with a standard deviation that can be quite large.

The "fourth kind" of the equation allows for non-integer and negative values, so even partial or non-working scopes could be considered - BUT - it gets so complicated it's hardly worth the effort over the discrete version "third kind." Just for the hell of it, I tried both, using self-assessed coefficients. I couldn't even get an answer from the continuous version, but with the discrete, I came up with 37 units with sigma 11 for myself.

So, after all that, I'd recommend my first answer above, and not worry about the numbers.

Ed

--- In TekScopes@..., Mark Wendt <mark.wendt@...> wrote:

On 04/10/2013 02:12 PM, vdonisa wrote:
Question inspired from the 532 thread - what's the optimal number of oscilloscopes a gentleman should have?

I know there's a minimum of 2 - so you can repair the troubled one - and I've seen as much as 6 (pretty crowded place, the owner used to have at least 4 pieces of each type of equipment).

What's your "optimal" number?

Valentin :-)
Till you have no more room for more? I've got 5 working and 1 dead with
CRT issues and 1 more k-ball unit.

Mark


Re: Tek 576 Curve Tracer Repair

 

Hi Sam,

I had last year a problem with the 576.
There was smoke coming out from the
left side.

It was the wire wound resistor in the power supply.
I replaced this and also the cap. But the problem
remained. It was not there when I turned the
mains voltage on not so fast using a variac.

The problem was - Albert was very helpful analysing -
a defective transistor in the current limiting of the
power supply.

May be you should have a look at this wire wound
resistor getting hot. It really burned out with a
bright light !

You could try powering up more slowly.
May be also your power supply is bad somehow.

Best,
Matthias


Re: Tek 2230 power fault fix

Graziano Tedoldi
 

--- In TekScopes@..., "chipbee40" <chipbee40@...> wrote:

Have you checked the bridge CR901-4 and C906? At 240V supply you should have approx 315Vdc on C906. It can go open as can the bridge diodes, you may be getting AC through which the mosfet won't like.

--- In TekScopes@..., "tedgraz1961" <systecma@> wrote:



--- In TekScopes@..., David <davidwhess@> wrote:

On Thu, 11 Apr 2013 08:25:58 -0000, "tedgraz1961" <systecma@>
wrote:

--- In TekScopes@..., David <davidwhess@> wrote:

On Wed, 10 Apr 2013 22:57:00 -0500, David <davidwhess@>
wrote:

On Mon, 08 Apr 2013 20:55:27 -0000, "tedgraz1961" <systecma@>
wrote:

Maybe that Tek has used low-power versions of the TL594?
Q928 and Q930 form a latching circuit that only supplies power to U930
once the voltage across C925 reaches about 23 volts. The trigger
point occurs when the voltage across R927 reaches 6.8 volts. After
starting, power to U930 is supplied from the transformer winding
connected to CR920 and the voltage across C925 drops to 14.3 volts as
marked in the schematic.
I was thinking about this some more and with Q9070 removed so no power
will come from the transformer, I doubt the voltage across C925 will
stay level. It should pulse up and down slowly as the latching
circuit tries to power U930.

R926 could be open, C925 could be leaking, or there is some other
power drain across C925.

None of that explains why Q9070 failed though unless CR920 was bad.
power at U930 is poor : 2 V

at C925 10,60 V

R926 is OK

CR920 is OK

How to check T906 windings value ? I test isolation from 3 winding only .
You do not need to yet. Something else is wrong.

The voltage to the startup network is not rising high enough to start
for some reason and that has nothing to do with the transformer.

How did you test CR920? Could it have high leakage or be breaking
down at 10.6 volts?

What is the voltage at the base and collector of Q928 and Q930?
I rising CR920-U930-R907-R912-C940-C941-R937-R934-C943-R945-R941-VR943-T948pin3/4- but V max 15/18V !!!

rising VR925 Vcc up to 50-60 V

Well, change zener 6,1 same effect !

I do not understand how this virtual ground work
Ok testing diode

Replace diode with new 1000V 2Amp ...same result


Re: TEK 532 --

Cliff White <w5cnw@...>
 

One other thing I just noticed: yours has a extra toggle switch below the external horizontal input, and what looks like an extra light above it. What do those labels say for those two? Mine has neither, but is still a P11.


Respectfully,
Cliff White, W5CNW
w5cnw@...
On 04/10/2013 10:14 PM, Cliff White wrote:

 

Mine's also blue, probably P11, and only says "532" w/o the 57. Strange.



On 04/10/2013 10:12 PM, d.sligar wrote:
 

I'm not sure exactly what the "57" represents, but I think at least part of it specifies the phosphor -- which, I believe, is a longer persistence type. Note the blue color.

David

--- In TekScopes@..., Cliff White wrote:
>
> Question: Why does his scope say "Type 532-57"? My 532 just says "Type
> 532"... ?
>
>
> On 04/10/2013 03:30 PM, Steve wrote:
> >
> > --- In TekScopes@... ,
> > David Sligar wrote:
> > >
> > > Hello, Group --
> > >
> > > As possibly many new members do, my first post is a plea for help.
> > Once my very nice 532 is working again, I might decide that I prefer
> > "reliable" to "elegant" -- and trade this one in for something a
> > little newer.
> > >
> > >
> > > I've been using this scope on a daily basis for about a month. On
> > Friday morning I tuned it on and suddenly -- no sweep. I've been
> > going through the beast as carefully
> > > as I can, looking for the bug.
> > > Tubes all check good, no visible damage / exceptions, "all" voltages
> > measure
> > > correctly. I suspect one might need a (working) scope to figure out
> > > where the sweep waveform disappears. I decided I'd try running my
> > > function generator as external sweep -- it worked, so that says at
> > least
> > > the horiz. amp is OK. I've now spent a couple of days
> > > and I'm not sure I'll be able to find what's wrong.
> > >
> > > Amazing how helpless we are without tools! I hope one or more of you
> > will be able to suggest where I should look.
> > >
> > > Thanks very much,
> > > David Sligar
> > > Grants Pass, OR
> >
> > David,
> >
> > A second scope would be very helpful, but you may be able to do some
> > things without it. Selecting a very slow sweep speed (1 div/sec) would
> > allow you so see the sawtooth on a DMM.
> >
> > First you need to isolate the main area not working. It could be at
> > least three -- trigger, timebase, or blanking. Turning the Trigger
> > Stability control to the far right should force the scope to free run.
> > This does not isolate the trigger circuit however. It only biases the
> > multivibrator in a way to have it reset when the sweep length
> > comparator trips at the end of the sweep.
> >
> > With another scope, you can trace all of the trigger circuit fairly
> > easily. I usually use line trigger mode when doing this, as I know
> > this gives a reliable signal, eliminating the possibility of a problem
> > in the trigger pickoff circuit in the plug-in. Trace the signal
> > through the comparator(V308), and verify the Trigger level control
> > moves the grid voltage around (pin 9 for all + polarity settings, pin
> > 2 for all -- mode positions).
> >
> > I was hoping to disable the unblanking pulse to rule that out, but I
> > don't see a way to do that simply by pulling tube, as the signal is
> > generated in a dual triode (V430B) that is shared with the trigger
> > multivibrator. Unfortunately, the AC coupling to differentiate the
> > pulse occurs before these tube stages, so there is no place you can
> > easily short to ground or a supply to get a stable DC bias voltage.
> >
> > If the trigger is going through OK, then you need to focus on the time
> > base. Use the circuit description in the manual to guide your
> > troubleshooting.
> >
> > Let us know your progress. Your scope looks really clean and is worth
> > preserving.
> >
> > - Steve
> >
> > >
> >
> >
>




7844 final conclusion

Craig Sawyers <c.sawyers@...>
 

Hi all

Well, after being given the runaround by the supply, my conclusion is that
it is in fact the transformer. Overall symptom is that the Beam-I-Sense
line is periodically interrupting the controller. After checking every
component in this circuit (including curve tracing Q1373), replacing the
U1275 from another supply, and replacing the HT multiplier with one from a
7704A spares supply the symptom was unchanged.

Today I have progressively disconnect HT circuits. I first disabled the 3kV
voltage doubler by pulling a lead on C2301 and C2311. No change. I then
disconnected the DC restorers by unsoldering the resistor chains that feed
them (a long shot). No change.

So now the only thing left connected to HT transformer winding is the
(already replaced) x7 multiplier. Even the 6.3V winding is no longer
stressed by being floated to 3kV. Symptom is identical, with Beam-I-sense
pulsing.

So it looks like I might have to weld together a 7904 and 7844 supply to get
the 7844 working. Unless one of you has a spares 7904 supply with a known
good transformer?

Craig


Re: RM15/515 Vertical Problem

Cliff White <w5cnw@...>
 

Steve, I think you meant to post this to the 532 thread?

On 04/11/2013 09:18 AM, Steve wrote:

 

--- In TekScopes@..., "Tom Miller" wrote:
>
> I would use an ohmmeter to check all the resistors in the vertical amp stages. Just measure them and see if they match the value on the resistors. If for example you measure 12 K across a 10 k resistor, you know it is bad. If it measures 5 k, you need to consider how it is used in the circuit. Most of the time, the carbon comp resistors go high in value, even open circuit.
>
> The fact that the position control works narrows things down to just the four tubes. Also, you can take some voltage readings on all four tubes with the controls set to normal positions.
>
> Good luck, you are off to a good start.
>
>
> Regards,
> Tom

With all due respect, I would not start here. Vertical and horizontal amp both work in XY mode, so unlikely to be a vertical problem.

The sawtooth test as suggested would verify unblanking, but unblanking is not likely to be the problem, Power supplies are good, so I would focus on trigger or time base.

If you have another scope, set the trigger to one of the Line positions (+ or -), with the trigger level knob near the center and stabilty set to auto. Set the time base to a medium to fast sweep (1 ms/div or faster) This should rearm the trigger before each new trigger pulse.

look at pin 6 on V306 (trigger comparator), then pin 1 of V320 (trigger shaper). Should see something like a square wave at V306, then a sharper pulse at V320 with a period of 16.6 ms (60 Hz power). If this is good move on to the time base. If not try swapping one of these tubes (where you don't see the signal).

If you only have a volt meter, go back to the slow sweep and look at pin 5 of V460. You should see a sawtooth here, which most likely you won't (as that would indicate it is only unblanking).

If you have a good trigger pulse but no sweep, it gets a bit more complicated. My schematics don't show waveforms, and the 532 circuit is a bit different than other 53x or 54x circuits. I would need to figure out what some of these waveforms should look like. Perhaps another member who has a working 532 can probe around and report what they see.

Let us know what the trigger circuit shows

- Steve



Need help with corrupted flash image on TDS460A

@Arcticgeek
 

Hi folks,

I have a TDS460A that I just picked up on ebay. It had a power supply issue that I have now fixed, but there is yet another problem because the unit does not boot.

By attaching a console port to the CPU board I have found that the flash rom checksum is bad, and that is what is halting the boot process. My guess is somebody tried to update the flash and then aborted the update. At any rate, I need to fix this problem.

I know the firmware can be updated using a PC with GPIB and the appropriate SW. Does anyone out there have the TDS460A firmware and the appropriate update utility software? If so, please message me!

I would also appreciate any help that someone could provide on how to do this. I believe I need the following:

1. Old PC with ISA slots running MSDOS
2. NI GPIB card installed in 1 of the slots
3. GPIB cable from pc to scope
4. The update utility and firmware images

Its been a LOOONG time since I used an ISA-based PC with DOS, but I might be able to scrounge up some old hardware....but is there a better/more modern way of doing this? Has anyone tried this.

Any advice/help is appreciated.

Thanks in advance.


Re: Tek 2230 power fault fix

chipbee40
 

Have you checked the bridge CR901-4 and C906? At 240V supply you should have approx 315Vdc on C906. It can go open as can the bridge diodes, you may be getting AC through which the mosfet won't like.

--- In TekScopes@..., "tedgraz1961" <systecma@...> wrote:



--- In TekScopes@..., David <davidwhess@> wrote:

On Thu, 11 Apr 2013 08:25:58 -0000, "tedgraz1961" <systecma@>
wrote:

--- In TekScopes@..., David <davidwhess@> wrote:

On Wed, 10 Apr 2013 22:57:00 -0500, David <davidwhess@>
wrote:

On Mon, 08 Apr 2013 20:55:27 -0000, "tedgraz1961" <systecma@>
wrote:

Maybe that Tek has used low-power versions of the TL594?
Q928 and Q930 form a latching circuit that only supplies power to U930
once the voltage across C925 reaches about 23 volts. The trigger
point occurs when the voltage across R927 reaches 6.8 volts. After
starting, power to U930 is supplied from the transformer winding
connected to CR920 and the voltage across C925 drops to 14.3 volts as
marked in the schematic.
I was thinking about this some more and with Q9070 removed so no power
will come from the transformer, I doubt the voltage across C925 will
stay level. It should pulse up and down slowly as the latching
circuit tries to power U930.

R926 could be open, C925 could be leaking, or there is some other
power drain across C925.

None of that explains why Q9070 failed though unless CR920 was bad.
power at U930 is poor : 2 V

at C925 10,60 V

R926 is OK

CR920 is OK

How to check T906 windings value ? I test isolation from 3 winding only .
You do not need to yet. Something else is wrong.

The voltage to the startup network is not rising high enough to start
for some reason and that has nothing to do with the transformer.

How did you test CR920? Could it have high leakage or be breaking
down at 10.6 volts?

What is the voltage at the base and collector of Q928 and Q930?
I rising CR920-U930-R907-R912-C940-C941-R937-R934-C943-R945-R941-VR943-T948pin3/4- but V max 15/18V !!!

rising VR925 Vcc up to 50-60 V

Well, change zener 6,1 same effect !

I do not understand how this virtual ground work


Re: RM15/515 Vertical Problem

ditter2
 

--- In TekScopes@..., "Tom Miller" <tmiller11147@...> wrote:

I would use an ohmmeter to check all the resistors in the vertical amp stages. Just measure them and see if they match the value on the resistors. If for example you measure 12 K across a 10 k resistor, you know it is bad. If it measures 5 k, you need to consider how it is used in the circuit. Most of the time, the carbon comp resistors go high in value, even open circuit.

The fact that the position control works narrows things down to just the four tubes. Also, you can take some voltage readings on all four tubes with the controls set to normal positions.

Good luck, you are off to a good start.


Regards,
Tom
With all due respect, I would not start here. Vertical and horizontal amp both work in XY mode, so unlikely to be a vertical problem.

The sawtooth test as suggested would verify unblanking, but unblanking is not likely to be the problem, Power supplies are good, so I would focus on trigger or time base.

If you have another scope, set the trigger to one of the Line positions (+ or -), with the trigger level knob near the center and stabilty set to auto. Set the time base to a medium to fast sweep (1 ms/div or faster) This should rearm the trigger before each new trigger pulse.

look at pin 6 on V306 (trigger comparator), then pin 1 of V320 (trigger shaper). Should see something like a square wave at V306, then a sharper pulse at V320 with a period of 16.6 ms (60 Hz power). If this is good move on to the time base. If not try swapping one of these tubes (where you don't see the signal).

If you only have a volt meter, go back to the slow sweep and look at pin 5 of V460. You should see a sawtooth here, which most likely you won't (as that would indicate it is only unblanking).

If you have a good trigger pulse but no sweep, it gets a bit more complicated. My schematics don't show waveforms, and the 532 circuit is a bit different than other 53x or 54x circuits. I would need to figure out what some of these waveforms should look like. Perhaps another member who has a working 532 can probe around and report what they see.

Let us know what the trigger circuit shows

- Steve


Re: Tek 576 Curve Tracer Repair

Bob Koller <testtech@...>
 

The machine left, or your left viewing from the front?



From: c1ferrari
To: TekScopes@...
Sent: Wednesday, April 10, 2013 6:19 PM
Subject: [TekScopes] Tek 576 Curve Tracer Repair

 
Hi all,

I bought a 576 from eBay with a Tektronix cal from Dallas which expired 01-DEC-10. Everything was going well and I was learning how to use the instrument...until today.

I was attempting to characterize 6C33C tubes when smoke began to emanate from the top array of ventilation ports on the machine's left side. Immediately, I attenuated the Variable Collector Supply and switched the machine off.

I did not observe any POP or other sound in connection with this event.

Now that I've recovered, somewhat, my equilibriium -- I'm writing the post to ask this august group if there is anyone, any resource in my neck of the woods -- San Diego, that can take a look at my beloved Tek 576 CT.

Please, let me know.

Very best regards,

Sam




Re: RM15/515 Vertical Problem

Cliff White <w5cnw@...>
 

Aha! I might have found it. R353 and 354 both measure around 18M, when the schematic says they should be 8K. I'll replace them and see what happens!


Respectfully,
Cliff White, W5CNW
w5cnw@...
On 04/10/2013 10:23 PM, Tom Miller wrote:

 

I would use an ohmmeter to check all the resistors in the vertical amp stages. Just measure them and see if they match the value on the resistors. If for example you measure 12 K across a 10 k resistor, you know it is bad. If it measures 5 k, you need to consider how it is used in the circuit. Most of the time, the carbon comp resistors go high in value, even open circuit.
 
The fact that the position control works narrows things down to just the four tubes. Also, you can take some voltage readings on all four tubes with the controls set to normal positions.
 
Good luck, you are off to a good start.
 
 
Regards,
Tom
 
----- Original Message -----
Sent: Wednesday, April 10, 2013 10:57 PM
Subject: Re: [TekScopes] Re: RM15/515 Vertical Problem

 

Ok, what next?


On 04/10/2013 08:50 PM, Tom Miller wrote:
 
You can check off the power supplies. Good work.
 
 
Tom
 
----- Original Message -----
Sent: Wednesday, April 10, 2013 9:44 PM
Subject: Re: [TekScopes] Re: RM15/515 Vertical Problem

 
I've checked all the power supplies, and here's what I got:

-150 Supply:
    -150.4VDC, 50mv (p-p) ripple

+100 Supply:
    +99.5VDC, 20mv ripple

+300 Supply:
    +300.8VDC, 50mv ripple


I then adjusted the "-150 Adj", and got the following data:

-150 Supply:
    -150.0VDC, 50mv (p-p) ripple

+100 Supply:
    +99.3VDC, 20mv ripple

+300 Supply:
    +299.95VDC (actually the meter couldn't decide between 299.9 and 300.0)
         50mv ripple


Looks good to me, do y'all agree?


On 04/10/2013 03:09 PM, HankC wrote:
 
Cliff,

A 515 & an RM15 are the same schematic.
There may be some slight differences in parts layout but they are electrically the same.
Until you have all the power supplies in spec, you are wasting your time looking at anything else.

 
HankC, Boston
WA1HOS




Re: Tek 2230 power fault fix

Graziano Tedoldi
 

--- In TekScopes@..., David <davidwhess@...> wrote:

On Thu, 11 Apr 2013 08:25:58 -0000, "tedgraz1961" <systecma@...>
wrote:

--- In TekScopes@..., David <davidwhess@> wrote:

On Wed, 10 Apr 2013 22:57:00 -0500, David <davidwhess@>
wrote:

On Mon, 08 Apr 2013 20:55:27 -0000, "tedgraz1961" <systecma@>
wrote:

Maybe that Tek has used low-power versions of the TL594?
Q928 and Q930 form a latching circuit that only supplies power to U930
once the voltage across C925 reaches about 23 volts. The trigger
point occurs when the voltage across R927 reaches 6.8 volts. After
starting, power to U930 is supplied from the transformer winding
connected to CR920 and the voltage across C925 drops to 14.3 volts as
marked in the schematic.
I was thinking about this some more and with Q9070 removed so no power
will come from the transformer, I doubt the voltage across C925 will
stay level. It should pulse up and down slowly as the latching
circuit tries to power U930.

R926 could be open, C925 could be leaking, or there is some other
power drain across C925.

None of that explains why Q9070 failed though unless CR920 was bad.
power at U930 is poor : 2 V

at C925 10,60 V

R926 is OK

CR920 is OK

How to check T906 windings value ? I test isolation from 3 winding only .
You do not need to yet. Something else is wrong.

The voltage to the startup network is not rising high enough to start
for some reason and that has nothing to do with the transformer.

How did you test CR920? Could it have high leakage or be breaking
down at 10.6 volts?

What is the voltage at the base and collector of Q928 and Q930?
I rising CR920-U930-R907-R912-C940-C941-R937-R934-C943-R945-R941-VR943-T948pin3/4- but V max 15/18V !!!

rising VR925 Vcc up to 50-60 V

Well, change zener 6,1 same effect !

I do not understand how this virtual ground work


Re: TEK 532 --

Cliff White <w5cnw@...>
 

If you connect a dc voltmeter (preferably analog) to the sawtooth out jack, then set the sweep speed to the slowest it goes, can you see the voltage changing as a ramp? You might also try the same thing with the delayed gate out.


Respectfully,
Cliff White, W5CNW
w5cnw@...
On 04/11/2013 12:19 AM, d.sligar wrote:

 

Hi, Cliff --
No trigger setting has any effect on the beam (spot). No settings were changed from the day before, when I used the scope normally. The sweep just wasn't there Friday morning when I powered up.
Thanks,
David

--- In TekScopes@..., Cliff White wrote:
>
> Did you try setting the trigger to line or external?
>
> Respectfully,
> Cliff White, W5CNW
> w5cnw@...
> On 04/10/2013 10:04 PM, d.sligar wrote:
> >
> > Thank you, Steve.
> > Just one comment, I have a dual trace plugin (53/54 K) as well as the
> > 53/54 C. Neither of these gives a sweep, so I maybe can eliminate the
> > pickoff circuits. (?)
> > Otherwise, I'll try what you suggest. I do think it's too soon to see
> > this one ascend (descend?) to scope heaven.
> >
> > I feel a bit over my head with this, but I'm not ready to give up.
> > I'll let you (and the group) know how things progress.
> >
> > Thanks again!
> > > >
> > > > David,
> > > >
> > > > A second scope would be very helpful, but you may be able to do some
> > > > things without it. Selecting a very slow sweep speed (1 div/sec)
> > would
> > > > allow you so see the sawtooth on a DMM.
> > > >
> > > > First you need to isolate the main area not working. It could be at
> > > > least three -- trigger, timebase, or blanking. Turning the Trigger
> > > > Stability control to the far right should force the scope to free
> > run.
> > > > This does not isolate the trigger circuit however. It only biases the
> > > > multivibrator in a way to have it reset when the sweep length
> > > > comparator trips at the end of the sweep.
> > > >
> > > > With another scope, you can trace all of the trigger circuit fairly
> > > > easily. I usually use line trigger mode when doing this, as I know
> > > > this gives a reliable signal, eliminating the possibility of a
> > problem
> > > > in the trigger pickoff circuit in the plug-in. Trace the signal
> > > > through the comparator(V308), and verify the Trigger level control
> > > > moves the grid voltage around (pin 9 for all + polarity settings, pin
> > > > 2 for all -- mode positions).
> > > >
> > > > I was hoping to disable the unblanking pulse to rule that out, but I
> > > > don't see a way to do that simply by pulling tube, as the signal is
> > > > generated in a dual triode (V430B) that is shared with the trigger
> > > > multivibrator. Unfortunately, the AC coupling to differentiate the
> > > > pulse occurs before these tube stages, so there is no place you can
> > > > easily short to ground or a supply to get a stable DC bias voltage.
> > > >
> > > > If the trigger is going through OK, then you need to focus on the
> > time
> > > > base. Use the circuit description in the manual to guide your
> > > > troubleshooting.
> > > >
> > > > Let us know your progress. Your scope looks really clean and is worth
> > > > preserving.
> > > >
> > > > - Steve
> > > >
> > > > >
> > > >
> > > >
> > >
> >
> >
>



Re: Tek 2230 power fault fix

 

On Thu, 11 Apr 2013 08:25:58 -0000, "tedgraz1961" <systecma@...>
wrote:

--- In TekScopes@..., David <davidwhess@...> wrote:

On Wed, 10 Apr 2013 22:57:00 -0500, David <davidwhess@...>
wrote:

On Mon, 08 Apr 2013 20:55:27 -0000, "tedgraz1961" <systecma@...>
wrote:

Maybe that Tek has used low-power versions of the TL594?
Q928 and Q930 form a latching circuit that only supplies power to U930
once the voltage across C925 reaches about 23 volts. The trigger
point occurs when the voltage across R927 reaches 6.8 volts. After
starting, power to U930 is supplied from the transformer winding
connected to CR920 and the voltage across C925 drops to 14.3 volts as
marked in the schematic.
I was thinking about this some more and with Q9070 removed so no power
will come from the transformer, I doubt the voltage across C925 will
stay level. It should pulse up and down slowly as the latching
circuit tries to power U930.

R926 could be open, C925 could be leaking, or there is some other
power drain across C925.

None of that explains why Q9070 failed though unless CR920 was bad.
power at U930 is poor : 2 V

at C925 10,60 V

R926 is OK

CR920 is OK

How to check T906 windings value ? I test isolation from 3 winding only .
You do not need to yet. Something else is wrong.

The voltage to the startup network is not rising high enough to start
for some reason and that has nothing to do with the transformer.

How did you test CR920? Could it have high leakage or be breaking
down at 10.6 volts?

What is the voltage at the base and collector of Q928 and Q930?

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