Date   

Re: Isolating a CRT-multiplier problem

Jim Popwell Jr <jpopwell@...>
 

I believe he is telling you to put the 20k 1/4watt      BETWEEN   the hv transformer and the multiplier, not in the lead going to the crt.

the idea is to let the osc and hv transformer work , if they are ok they will generate about 5kv to 7kv and in doing so cook the 20k .
 if the multiplier is too much of a load it will burn up the 20k resistor.

if the 1/4 watt resistor doesn't burn up then the multiplier is NOT too much of a load and probably ok.



On Sep 26, 2013, at 4:41 AM, "wb5tka" <dan@...> wrote:

 

My idea was to simply unplug the output of the multiplier from the CRT lead and fire up the scope. If the HV oscillator continues to fail to run, then the problem would be the multiplier. If the oscillator runs, then the problem would be with the CRT since now the multiplier is in the circuit but the CRT which may be loading the output of the multiplier and causing the problem has been isolated. Granted there could be a problem within the multiplier which only causes the problem to show up under a load but as the components within the multiplier are only diodes and capacitors, those components usually do not act that way. They either work or they don't work and will be affected only by a load if they are working correctly.

My question was will running the unit with no load on the multiplier create a problem?

Thanks,

--- In TekScopes@..., Reed Dickinson wrote:
>
> Hi:
>
> You are correct, you have two sources of HV problems, the 3X multiplier
> or the CRT. To isolate the problem disconnect the HV lead from the CRT
> and solder a 20K, 1/4W resistor between the 3X multiplier and the
> flyback transformer and fire up your scope. If the 20K resistor burns
> up the problem is in the multiplier. If it does not burn up the problem
> is in the CRT. You may have to wait a while but the problem will
> eventually be apparent.
>
> Reed Dickinson
>
>
>
> On 9/25/2013 7:01 AM, wb5tka wrote:
> >
> > Thanks Reed. Sounds like that's the way to go. Though a new scope
> > would be appealing, right now I have some other spending priorities
> > (photography equipment can bankrupt you too, LOL) I really hate to let
> > go of the old 465. As long as there is a way to get it going again
> > without out going overboard on the cost, I'm willing to give it a go.
> >
> > One more question. Is there any way to be sure that the problem is
> > indeed the multiplier and not something following it? I know from here
> > it goes to the CRT and baring a short there (nothing measured on the
> > pin to ground of the lead running from the multiplier output side or
> > the end which goes to the CRT) the problem should be with the module
> > itself.
> >
> > Is it a valid test (and a safe one) to unplug the output end which
> > goes to the CRT and power the unit up with the multiplier in circuit?
> > Just wanting to make sure that with no load on it that nothing blows.
> >
> > --- In TekScopes@..., Reed Dickinson > > >
> > > CORRECTION
> > >
> > > In checking my notes I did not connect the D tap on the ECG538 to
> > > ground. Connecting D to ground would only work if the source was
> > > capacitor coupled. The correct connections are to leave the D tap
> > > unconnected, connect the LOW tap to GROUND and the IN tap to the
> > > transformer. Do not connect anything to the FOCUS tap.
> > >
> > > Reed
> > >
> > >
> > >
> > > On 9/24/2013 11:01 PM, Reed Dickinson wrote:
> > > >
> > > > The NTE538 or ECG538 voltage tripler will work quite nicely in 465,
> > > > 465B 475, 457A scopes. Connect the D and LOW taps to ground and do
> > > > not use the FOCUS tap. Cut the end off the original tripler and
> > > > splice it onto the new HV lead. Use a thick plastic piece of tubing
> > > > around the splice and fill with silicon to insulate it, make sure
> > > > there are no sharp wire whiskers on the splice or you will get a
> > > > corona arc. Drill two holes in the metal chassis where the old
> > tripler
> > > > was and mount the 538 with two screws. You might have to trim a
> > > > little metal from the aluminum cover that covered the original
> > tripler.
> > > >
> > > > Reed Dickinson
> > > >
> > > >
> > > >
> > > > On 9/24/2013 3:06 PM, wb5tka wrote:
> > > >>
> > > >> Since it appears that high voltage multipliers for the older scopes
> > > >> such as the 465 are virtually impossible to find, does anyone have
> > > >> any experience or thoughts on building one? I've heard of them being
> > > >> built and I'm willing to give that a try but I don't know if the
> > > >> multiplier in the 465 is 3X, 4X or whatever.
> > > >>
> > > >> Thoughts?
> > > >>
> > > >> Dan,
> > > >>
> > > >
> > > >
> > >
> >
> >
>



Re: 7D13 does not work

 

David,

The readout digits stay at 020. Changing functions and scales moves the decimal point and text as expected but the value never changes and I see no evidence of a cycle.

I am trying to find a UTV I can afford for the rancho and I am trying to sell off much of my tektronix resources. I have much to do. I really expected a logic or power supply problem but The ICs have been swapped and the power supply voltages appear to be okay.

I guess I will have to see if i can print out the schematics and do some reading. I hate reading manuals.


Jerry Massengale



-----Original Message-----
From: David
To: TekScopes
Sent: Wed, Sep 25, 2013 8:57 am
Subject: Re: [TekScopes] 7D13 does not work

 
Do any of the modes work?

DC volts is usually the place to start but the 7D13 uses an internal isolation
power supply so the output voltages of that should be checked.

The early Tektronix multimeters use the same terminal for volt, ohm, and amp
measurements so it is possible to damage the amp mode switches if one shorts out
a low impedance source during range selection. Check the switch elements to see
if the amp connections are fused together. The highest current range switch
element and maybe others when fused together will cause the symptom you
describe.

On Wed, 25 Sep 2013 09:39:06 -0400 (EDT), you wrote:

> Hi,
>
>I have a 7D13 that seems to go into the right modes but does not work. The display does not blink in ohms mode. I believe all socketed semiconductors have been checked okay. help wanted.
>
>Jerry Massengale


Re: 7D15 Has died and need troubleshooting tips..

k6whp
 

Gentlemen,


Thank you for the advice. I shall continue my search. For curiosity and because I am a complete idiot, can you describe the procedure you refer to as "ohm the rails".


Thanks,


Bill, k6whp



---In tekscopes@..., <dcasey@...> wrote:

I'll second the tantalum caps. Both of my 7D15's had shorted tants.
Sometimes they don't short until they get power applied and thus
measure fine when you ohm the rails.
They don't always looked burned either.

Dave Casey


Quoting David <davidwhess@...>:

> There is nothing special about the transistors in the switching
> power supply so
> modern replacements will not be a problem.
>
> My primary suspects would be the various epoxy dipped solid tantalum
> capacitors
> located on just about every printed circuit board. A close visual inspection
> may reveal one with a cracked or burned exterior. Tektronix did not voltage
> derate some of them at all.
>
> On 25 Sep 2013 14:10:43 -0700, you wrote:
>
>> I have a 7704A and recently had my 7D15 freq counter go South
>> taking down the whole scope. It was in a horizontal slot and just
>> went pffffffffft one evening. Following analysis done:
>>
>> (1) Replaced 7D15 in slot with another plug-in. Scope works fine.
>>
>> (2) Pulled the 7D15 and looked over the little A8 switcher board on
>> it and the caps and resistors appeared good. Did NOT check the
>> transistors. Are there commonly available replacements for those?
>>
>> (3) Left the A8 board off and plugged the 7D15 back into the slot;
>> same result: dead scope.
>>
>> Can I conclude that the switcher is o.k. and I should be looking
>> elsewhere on the 7D15. If so, where? If not, what?
>>
>> I did some snooping and did not see any suspect (i.e., burnt)
>> components, etc.
>>
>> My thanks in advance for any help.
>>
>> Bill, k6whp
>


Re: Isolating a CRT-multiplier problem

wb5tka <dan@...>
 

Hank,

With the 465, the heater voltage is created with a winding from the high voltage transformer. Not the main power transformer. I have unplugged the socket from the CRT but the oscillator still failed to operate. Only when I lifted the jumper which supplies the ground to the tripler module did the oscillator run. It produced a high pitched (mosquito like) sound and the HV TP read -2.4 KV. I did not think to look at the CRT rear to see if I could see the heater lit.

--- In TekScopes@yahoogroups.com, HankC <hankc918@...> wrote:

Where does the filament voltage for the CRT come from ?
The reason I ask is because I have seen older scopes, where the CRT filament is fed by the main power transformer.
Leakage paths in the transformer will load down the negative HV, which affects the entire HV supply.
This is easily checked by disconnecting the CRT socket & see if the HV starts working, as measured by a DMM.


 
HankC, Boston
WA1HOS


Re: Isolating a CRT-multiplier problem

 

Hank, the filament supply for the 465/475 scope comes from a winding on the HV transformer.
 
Regards,
Tom
 

----- Original Message -----
From: HankC
Sent: Thursday, September 26, 2013 11:06 AM
Subject: [TekScopes] Re: Isolating a CRT-multiplier problem

 

Where does the filament voltage for the CRT come from ?
The reason I ask is because I have seen older scopes, where the CRT filament is fed by the main power transformer.
Leakage paths in the transformer will load down the negative HV, which affects the entire HV supply.
This is easily checked by disconnecting the CRT socket & see if the HV starts working, as measured by a DMM.

 
HankC, Boston
WA1HOS


Re: 576 Step Generator Problem

dc_rawding
 

So then I checked the voltage at the Q150B ... it is supposed to be at 0V ... it
was (this is from memory ~7V).


To clarify ... The check was done at the base wire of Q150B ... the reading there was approximately +7V.

--- In TekScopes@yahoogroups.com, "dc_rawding" <drawding@...> wrote:

Albert,

The CRT always has the correct steps (0-10) and they are always spaced at 2V per step.

I was able to do some more testing on Tuesday ...

The signal looks good at all settings at pin AI ... with the wire from pin AF dis.connected the settings look good. So to me that clears the circuit up through the resistors to pin AF. However, when I hook up the wire to pin AF ... the problem shows up.

So I did some more testing to try and isolate the problem... I remove the wires from pins AE and AD. I then verified pin AB was at ground potential. With this set up ... I still was seeing the problem. I then took out Q150 and placed two separate 2N2484s in its place. The problem went away! Cool! Well... not so much. WIth the new transistor pair in there ... when pins AE and AD were hooked back up ... no signal at terminal B (with invert pressed or released).

So then I put Q150 back in ... everything returned to back the way it was (same limits on positive going steps at terminal B)

So then I checked the voltage at the Q150B ... it is supposed to be at 0V ... it was (this is from memory ~7V). This is where my troubleshooting ended for the evening. So I am thinking that there is leaking in the +1 amplifier section of he circuit. I have no guesses as to why the replacement transistors seem to work with the pins AE and AD removed ... and not when they are hooked up. Perhaps solving the high voltage at the base of Q150B will solve this issue too.

I will not be able to do any more testing until Friday.

Thanks again for all your help.

Dave


Re: Isolating a CRT-multiplier problem

 

Where does the filament voltage for the CRT come from ?
The reason I ask is because I have seen older scopes, where the CRT filament is fed by the main power transformer.
Leakage paths in the transformer will load down the negative HV, which affects the entire HV supply.
This is easily checked by disconnecting the CRT socket & see if the HV starts working, as measured by a DMM.

 
HankC, Boston
WA1HOS


Re: 576 Step Generator Problem

dc_rawding
 

Albert,

The CRT always has the correct steps (0-10) and they are always spaced at 2V per step.

I was able to do some more testing on Tuesday ...

The signal looks good at all settings at pin AI ... with the wire from pin AF dis.connected the settings look good. So to me that clears the circuit up through the resistors to pin AF. However, when I hook up the wire to pin AF ... the problem shows up.

So I did some more testing to try and isolate the problem... I remove the wires from pins AE and AD. I then verified pin AB was at ground potential. With this set up ... I still was seeing the problem. I then took out Q150 and placed two separate 2N2484s in its place. The problem went away! Cool! Well... not so much. WIth the new transistor pair in there ... when pins AE and AD were hooked back up ... no signal at terminal B (with invert pressed or released).

So then I put Q150 back in ... everything returned to back the way it was (same limits on positive going steps at terminal B)

So then I checked the voltage at the Q150B ... it is supposed to be at 0V ... it was (this is from memory ~7V). This is where my troubleshooting ended for the evening. So I am thinking that there is leaking in the +1 amplifier section of he circuit. I have no guesses as to why the replacement transistors seem to work with the pins AE and AD removed ... and not when they are hooked up. Perhaps solving the high voltage at the base of Q150B will solve this issue too.

I will not be able to do any more testing until Friday.

Thanks again for all your help.

Dave


Re: Tektronix 2465BDM Calibration Help

Chuck Harris <cfharris@...>
 

Hi Daniel,

I calibrate 2465's for $140 plus shipping to/from Maryland, USA.
Shipping works out to about $1/lb on a well packed 2465... about
$30 each way in the US.

I have a Fluke 5200A, and 5205A, so I can calibrate the AC up to
1000Vrms.... I have a Fluke 343A for DC up to 1000V and, I have
the usual TG501, PG506, SG503,FG501, and a Systron Donner leveled
synthesizer to take the frequency up to 1GHz. I also have a
Tektronix 35ps tunnel diode pulser for checking pulse response.

My standards are not NIST traceable, but they have been spot
checked to other standards, and I believe result in a system
calibrated better than Tektronix specified for the 2465.

The Fluke 5205A is truly a scary piece of equipment. It will
do 1000V at 100ma, and will truly cook you! It has a bunch of
4CX250 tetrodes driving the final stage. It weighs more than
150lbs! The fans really roar.

-Chuck Harris

lazystrings wrote:

I repaired a Tektronix 2465B DM and I was able to calibrate with lots of pain the Horizontal time base that was out of cal in some ranges.
Before any calibration was performed I backed up the NVRAM Dallas 1225Y but it was already dead and it wasn't holding the data reliably. I Installed a Socket and replaced it with a fresh 1225AD and downloaded NVRAM data I found at the KO4BB repository. Once I installed the NVRAM on the A5 board, the Scope started without errors but some of the horizontal scales where out of tolerance. The DMM was also totally out of Calibration.
I was able to calibrate everything on the scope part but on the DMM side I don't have equipment to calibrate ACV and ACA.
I have a FLuke 5200A but it only goes to 110V and I need to be able to generate 500VAC (scary stuff) to finish the CAL routine as it doesn't allow for partial calibration.
I have no access to other equipment (unless I rent some). Is there any safe way to generate the high voltages at the required frequencies to finish the calibration of the DMM? Is it possible to modify the memory locations on the NVRAM with the right parameters to the missing calibration parameters?
I couldn't find on the service manuals the location of each parameter.
I can read the contents of the Ram using Exerciser 02 and also reading the bin file I created after I backed up the fresh NVRAM with my eprom programmer. I found the exact location by finding the information shown by Exerciser 02 and looking at the binary file I created.
Any advise would be greatly appreciated.
Thank you
Daniel


Re: Sign the Petition to get the old groups back.

iglesia_cristiana_arpas_eternas
 

 Hi Jay..I agree..the sign was done!!

Regards Gabriel.



---In tekscopes@..., <jayw_comark@...> wrote:

This is so bad I cannot even contribute anymore using this lousy NEO web interface.
For some reason, I can create a subject, but cannot add any content, so I had to email this in.
If this does not get any better, I'll probably unsubscribe... What's the use?

Anyway, this showed up on manual exchange so I figured I'd post info for this petition here.
"Yahoo! Groups: I want the old Yahoo Groups back!"

http://www.change.org/petitions/yahoo-groups-i-want-the-old-yahoo-groups-back?share_id=LXrsiDuGzv&utm_campaign=signature_receipt&utm_medium=email&utm_source=share_petition

Jay


Re: Sign the Petition to get the old groups back.

Don Black <donald_black@...>
 

Yahoo is playing with fire. It's not just Yahoo groups, it's their corporate reputation that will stink. When I first started using the Internet it was just evolving from text to graphic sites and Yahoo was the new search engine that was the wonder of the age. Since hen there are a host of other search engines available, Google has become the giant to the point where it's now part of the language -  Google to find .....
Yahoo lost the lead and has tried to diversify but it needs all the credence and good will it can get. Maybe only 1% of its group have actually left but most members who regularly use it are not just annoyed but furious. There have been many of the biggest companies who have tried forcing something new and unwanted on the public and have soon had the sense to reverse the decision to preserve their market. The longer Yahoo holds out the more damage it will do. Businesses associated with them will soon get the jitters if their reputations, customers and sales fall away. I haven't noticed it hitting the mass media here yet but if they continue it will happen. I don't have any shares in Yahoo but I'd be worried if I did.

Don Black.

On 26-Sep-13 11:02 PM, Knut wrote:
 

I think wanting the old Yahoo Groups back is a futile exercise.


So far, the groups that left because of Neo accounted for just under a million group members.
That is still less than 1% of the total number of Yahoo Group users.

Groups that are REALLY unhappy with Yahoo Groups have already moved like one of the other Yahoo Groups I'm a member of.
Others like this one will probably move unless Neo somehow magically gets fixed.
And the majority of the groups will just continue with Yahoo as best they can.

I can just dee the spin by Yahoo - 99% of our Yahoo customers are happy with the new format.

Knut

---------------
On 2013-09-26, at 6:12 AM, Jay Walling wrote:
 


Anyway, this showed up on manual exchange so I figured I'd post info for this petition here.
"Yahoo! Groups: I want the old Yahoo Groups back!"




Re: Sign the Petition to get the old groups back.

Knut <knut@...>
 

I think wanting the old Yahoo Groups back is a futile exercise.

So far, the groups that left because of Neo accounted for just under a million group members.
That is still less than 1% of the total number of Yahoo Group users.

Groups that are REALLY unhappy with Yahoo Groups have already moved like one of the other Yahoo Groups I'm a member of.
Others like this one will probably move unless Neo somehow magically gets fixed.
And the majority of the groups will just continue with Yahoo as best they can.

I can just dee the spin by Yahoo - 99% of our Yahoo customers are happy with the new format.

Knut

---------------

On 2013-09-26, at 6:12 AM, Jay Walling wrote:
 


Anyway, this showed up on manual exchange so I figured I'd post info for this petition here.
"Yahoo! Groups: I want the old Yahoo Groups back!"



Re: Tektronix 2465BDM Calibration Help

J. L. Trantham
 

Daniel,

 

Where are you located?

 

Joe

 

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of lazystrings
Sent: Thursday, September 26, 2013 1:45 AM
To: TekScopes@...
Subject: [TekScopes] Tektronix 2465BDM Calibration Help

 

 

I repaired a Tektronix 2465B DM and I was able to calibrate with lots of pain the Horizontal time base that was out of cal in some ranges.
Before any calibration was performed I backed up the NVRAM Dallas 1225Y but it was already dead and it wasn't holding the data reliably. I Installed a Socket and replaced it with a fresh 1225AD and downloaded NVRAM data I found at the KO4BB repository. Once I installed the NVRAM on the A5 board, the Scope started without errors but some of the horizontal scales where out of tolerance. The DMM was also totally out of Calibration.
I was able to calibrate everything on the scope part but on the DMM side I don't have equipment to calibrate ACV and ACA.
I have a FLuke 5200A but it only goes to 110V and I need to be able to generate 500VAC (scary stuff) to finish the CAL routine as it doesn't allow for partial calibration.
I have no access to other equipment (unless I rent some). Is there any safe way to generate the high voltages at the required frequencies to finish the calibration of the DMM? Is it possible to modify the memory locations on the NVRAM with the right parameters to the missing calibration parameters?
I couldn't find on the service manuals the location of each parameter.
I can read the contents of the Ram using Exerciser 02 and also reading the bin file I created after I backed up the fresh NVRAM with my eprom programmer. I found the exact location by finding the information shown by Exerciser 02 and looking at the binary file I created.
Any advise would be greatly appreciated.
Thank you
Daniel


Re: Isolating a CRT-multiplier problem

wb5tka <dan@...>
 

My idea was to simply unplug the output of the multiplier from the CRT lead and fire up the scope. If the HV oscillator continues to fail to run, then the problem would be the multiplier. If the oscillator runs, then the problem would be with the CRT since now the multiplier is in the circuit but the CRT which may be loading the output of the multiplier and causing the problem has been isolated. Granted there could be a problem within the multiplier which only causes the problem to show up under a load but as the components within the multiplier are only diodes and capacitors, those components usually do not act that way. They either work or they don't work and will be affected only by a load if they are working correctly.

My question was will running the unit with no load on the multiplier create a problem?

Thanks,

--- In TekScopes@yahoogroups.com, Reed Dickinson <reed714@...> wrote:

Hi:

You are correct, you have two sources of HV problems, the 3X multiplier
or the CRT. To isolate the problem disconnect the HV lead from the CRT
and solder a 20K, 1/4W resistor between the 3X multiplier and the
flyback transformer and fire up your scope. If the 20K resistor burns
up the problem is in the multiplier. If it does not burn up the problem
is in the CRT. You may have to wait a while but the problem will
eventually be apparent.

Reed Dickinson



On 9/25/2013 7:01 AM, wb5tka wrote:

Thanks Reed. Sounds like that's the way to go. Though a new scope
would be appealing, right now I have some other spending priorities
(photography equipment can bankrupt you too, LOL) I really hate to let
go of the old 465. As long as there is a way to get it going again
without out going overboard on the cost, I'm willing to give it a go.

One more question. Is there any way to be sure that the problem is
indeed the multiplier and not something following it? I know from here
it goes to the CRT and baring a short there (nothing measured on the
pin to ground of the lead running from the multiplier output side or
the end which goes to the CRT) the problem should be with the module
itself.

Is it a valid test (and a safe one) to unplug the output end which
goes to the CRT and power the unit up with the multiplier in circuit?
Just wanting to make sure that with no load on it that nothing blows.

--- In TekScopes@yahoogroups.com, Reed Dickinson <reed714@> wrote:

CORRECTION

In checking my notes I did not connect the D tap on the ECG538 to
ground. Connecting D to ground would only work if the source was
capacitor coupled. The correct connections are to leave the D tap
unconnected, connect the LOW tap to GROUND and the IN tap to the
transformer. Do not connect anything to the FOCUS tap.

Reed



On 9/24/2013 11:01 PM, Reed Dickinson wrote:

The NTE538 or ECG538 voltage tripler will work quite nicely in 465,
465B 475, 457A scopes. Connect the D and LOW taps to ground and do
not use the FOCUS tap. Cut the end off the original tripler and
splice it onto the new HV lead. Use a thick plastic piece of tubing
around the splice and fill with silicon to insulate it, make sure
there are no sharp wire whiskers on the splice or you will get a
corona arc. Drill two holes in the metal chassis where the old
tripler
was and mount the 538 with two screws. You might have to trim a
little metal from the aluminum cover that covered the original
tripler.

Reed Dickinson



On 9/24/2013 3:06 PM, wb5tka wrote:

Since it appears that high voltage multipliers for the older scopes
such as the 465 are virtually impossible to find, does anyone have
any experience or thoughts on building one? I've heard of them being
built and I'm willing to give that a try but I don't know if the
multiplier in the 465 is 3X, 4X or whatever.

Thoughts?

Dan,


Re: Isolating a CRT-multiplier problem

wb5tka <dan@...>
 

Reed,

When you say solder the resistor between the multiplier and the flyback transformer, though I have heard the term, I've never been a TV technical person (my work in electronics has been pretty much everything else) I am not sure what you mean by the flyback transformer. The only transformer I know of (other than the main pwr supply) is the HV transformer which creates the high voltage as the result of the HV oscillator working. So I would have no idea where to tie the end of the resistor.

At the multiplier end, I presume you mean to somehow manage to get the end of a resistor in contact with the conductor part of the output lead of the multiplier which is down inside the white insulated elbow connector at the end of the output lead. Or did I miss something?

--- In TekScopes@yahoogroups.com, Reed Dickinson <reed714@...> wrote:

Hi:

You are correct, you have two sources of HV problems, the 3X multiplier
or the CRT. To isolate the problem disconnect the HV lead from the CRT
and solder a 20K, 1/4W resistor between the 3X multiplier and the
flyback transformer and fire up your scope. If the 20K resistor burns
up the problem is in the multiplier. If it does not burn up the problem
is in the CRT. You may have to wait a while but the problem will
eventually be apparent.

Reed Dickinson



On 9/25/2013 7:01 AM, wb5tka wrote:

Thanks Reed. Sounds like that's the way to go. Though a new scope
would be appealing, right now I have some other spending priorities
(photography equipment can bankrupt you too, LOL) I really hate to let
go of the old 465. As long as there is a way to get it going again
without out going overboard on the cost, I'm willing to give it a go.

One more question. Is there any way to be sure that the problem is
indeed the multiplier and not something following it? I know from here
it goes to the CRT and baring a short there (nothing measured on the
pin to ground of the lead running from the multiplier output side or
the end which goes to the CRT) the problem should be with the module
itself.

Is it a valid test (and a safe one) to unplug the output end which
goes to the CRT and power the unit up with the multiplier in circuit?
Just wanting to make sure that with no load on it that nothing blows.

--- In TekScopes@yahoogroups.com, Reed Dickinson <reed714@> wrote:

CORRECTION

In checking my notes I did not connect the D tap on the ECG538 to
ground. Connecting D to ground would only work if the source was
capacitor coupled. The correct connections are to leave the D tap
unconnected, connect the LOW tap to GROUND and the IN tap to the
transformer. Do not connect anything to the FOCUS tap.

Reed



On 9/24/2013 11:01 PM, Reed Dickinson wrote:

The NTE538 or ECG538 voltage tripler will work quite nicely in 465,
465B 475, 457A scopes. Connect the D and LOW taps to ground and do
not use the FOCUS tap. Cut the end off the original tripler and
splice it onto the new HV lead. Use a thick plastic piece of tubing
around the splice and fill with silicon to insulate it, make sure
there are no sharp wire whiskers on the splice or you will get a
corona arc. Drill two holes in the metal chassis where the old
tripler
was and mount the 538 with two screws. You might have to trim a
little metal from the aluminum cover that covered the original
tripler.

Reed Dickinson



On 9/24/2013 3:06 PM, wb5tka wrote:

Since it appears that high voltage multipliers for the older scopes
such as the 465 are virtually impossible to find, does anyone have
any experience or thoughts on building one? I've heard of them being
built and I'm willing to give that a try but I don't know if the
multiplier in the 465 is 3X, 4X or whatever.

Thoughts?

Dan,


Re: Single Transistor Blocking Oscillator Question

Don Black <donald_black@...>
 

Or transformer, doubler faulty? Try disconnecting the doubler from the transformer and see if it oscillates.

Don Black.

On 26-Sep-13 5:59 AM, iglesia_cristiana_arpas_eternas@... wrote:
 

Hi Dennis..in order to try help you..could you hand draw the circuits and show us?.

At first glance any good HV transistor "must" be right if excited by secondary winding , but if no being to oscillate..perhaps some cap or resistor associated is out of value.

Is any start up  base current present?

Gabriel.



---In tekscopes@..., wrote:

I am debugging a very interesting one of a kind engineering prototype that Tek made in 1970. No schematics exist for it. It contains two small (2 ½ cm x 6 ½ cm) CRTs. It does not work. I have repaired most of it and have one major obstacle left before it will spring to life. It uses a single transistor blocking oscillator to generate the CRT voltages. The CRT has all its voltages connected via the rear socket so they do not require a high anode voltage.

                                                          

The blocking oscillator circuit uses a single NPN TO-220 medium power transistor. It runs off of a 40VDC supply. It was missing the HV fuse. I guessed that the fuse was on the order of 0.5A fast blow. So the transistor has to be able to handle ½ Amp. Someone attempted to repair it once before and, among other mistakes, they substituted the wrong transistor.

 

I can guess that a blocking oscillator transistor has to have a high Vceo and Vcbo on the order of a few hundred volts because the HV transformer will generate spikes as it turns off. Unfortunately Beta goes down as Vceo and Vcbo go up. So I have no idea if the circuit will work with a typical High Voltage transistor’s Beta which is usually in the 10 to 50 range.  I thought I might need a Darlington to get the Beta high enough but that may not be the case if the HV Transformer’s base drive winding is designed for driving a low Beta transistor. What I am fairly sure of is that the transistor has to handle +40V Vcc at 0.5A Ic. I tried a HV transistor with a Beta of about 100and it didn’t oscillate. I also tried another HV Darlington Transistor (NTE2540) which didn’t work either.

 

The output of the HV Transformer goes through a simple 2X multiplier. It appears to be OK and is not shorted. There is a 0.6 Ohm resistor between the emitter of the oscillator transistor and ground for degeneration or to limit collector current.

 

My best hope to figure out what the right transistor might have been is to find other single NPN TO-220 blocking oscillator schematics in use about the same time (1970-1971) in Tek products that had a small CRT in them. But I’m drawing a blank.

 

CAN ANYONE SUGGEST OTHER TEK SCHEMATICS FROM 1970-1972 THAT WOULD SHOW A SINGLE TRANSISTOR BLOCKING OSCILLATOR TO DRIVE SMALL CRTS?

 

.



Sign the Petition to get the old groups back.

 

This is so bad I cannot even contribute anymore using this lousy NEO web interface.
For some reason, I can create a subject, but cannot add any content, so I had to email this in.
If this does not get any better, I'll probably unsubscribe... What's the use?

Anyway, this showed up on manual exchange so I figured I'd post info for this petition here.
"Yahoo! Groups: I want the old Yahoo Groups back!"

http://www.change.org/petitions/yahoo-groups-i-want-the-old-yahoo-groups-back?share_id=LXrsiDuGzv&utm_campaign=signature_receipt&utm_medium=email&utm_source=share_petition

Jay


Re: File space increased to 2GB

Mark Wendt <mark.wendt@...>
 

On 09/25/2013 04:54 PM, Jim Cotton wrote:



After the notepad gets wet you may be able to recover your data,
not so likely for the iThing...

I file a folder full of data sheets and hand drawn schematics every time
I make a custom TM500 or NIM bin module.

The PDF always goes between sheets when tracing a signal,
hard to trace without paper.

Jim Cotton
n8qoh
Hard to write troubleshooting notes on the schematics when it's on a computer screen too.

Mark


Re: Hakko Soldering iron tip thermometer

Mark Wendt <mark.wendt@...>
 

On 09/25/2013 01:30 PM, Michael A. Terrell wrote:
Mark Wendt wrote:
On 09/25/2013 10:48 AM, Michael A. Terrell wrote:
Mark Wendt wrote:
Well, mine arrived from Hong Kong the other day, and I finally scrounged
up a battery for it. Fired it up, and mine reads in Centigrade.

Didn't someone here on the list get one, and find it in Fahrenheit?

If so, if you are interested in a swap, let me know.
There are two versions, you need to read the listing for the unit you
bought and see if it says Fahrenheit. They may have shipped you the
wrong version.
Yes, I knew there were two versions. The listing doesn't say much one
way or the other, other than the temperature range and resolution in the
blurb down below:

http://www.ebay.com/itm/281084703958?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Resolution is stated as 1˚F, which can't be done in the ˚C mode.
True dat. I was presuming it was just boilerplate for the ad. I'll send them an email and see what they do.

Mark


Re: File space increased to 2GB

Mark Wendt <mark.wendt@...>
 

On 09/25/2013 01:10 PM, Artek Manuals wrote:

Mark & Garey

OK try uploading a file to the files section and see if it takes, I
tried uploading a file on another group , it acted like it went up but
the file never showed up in the directory

Garey

What is a Iphone? Is it useful for reading a letter size PDF page on or
a full size schematic? :-)

Dave
ArtekManuals
I just uploaded a text file and it showed up. Deleted it right after it showed.

Mark

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