Date   

Re: 545 HV won't oscillate 100% of the time.

Don Black <donald_black@...>
 

I hope you get it sorted out Dan but I was being facetious about the eBay tubes advertised as tested good. I wonder what tests were done? I noticed another ad for similar caps saying they were tested OK on a bridge. No mention of leakage or if the bridge had to be adjusted for losses. Maybe I'm just getting cynical in my old age.

Don Black,

On 08-Dec-13 10:33 AM, Daniel Koller wrote:
 

Hi all,
  My caps probably are bad.  When I first got the scope around 1980, I learned about "black beauties" and had to replace them in the power supply, but I think I recall being told that the bumble-bee types were fine, so those stayed in.  Now it looks like I have leakage from them in the HV power supply.  See the attached photo here: http://groups.yahoo.com/neo/groups/TekScopes/photos/albums/158207078/lightbox/1517700781
The two shiny black 0.001 uF caps stand out because they are coated in oil.  You can't see it on the photo, but there is a film of liquid oil between the middle cap and the 56K resistor below it.  Those two are coming out but being a big fan of "don't mess with it if it ain't broke" I might leave the other caps in unless there is an obvious failure. Mind you, my scope works well when it does turn on.

But I've had some other modifications it seems.  What's that square cap on the left and the 2.2K resistor doing there?  I'll have to trace the circuit to see where they were put in and why.  Maybe that was a long ago patch for the oscillator failure?  Or the cause of it now?

I see now why I had originally thought my scope was much younger than it is - before I learned from the group here that the "brown" Teks were pre-1954.  There is this circuit board in my scope:
http://groups.yahoo.com/neo/groups/TekScopes/photos/albums/158207078/lightbox/1026393052
Someone seems to have made factory improvements circa 1967.   What was in its place before this?  Is it possible my additional HV circuit components were placed in the same upgrades/refurbishment?

Back to the shop.  I've got an hour before guests arrive!

Dan

On Saturday, December 7, 2013 10:58 AM, Don Black wrote:

>I'm not so sure. Yours may be faulty, these are tested good so they must be a rare animal.
>
>Don Black.
>
>On 08-Dec-13 2:31 AM, Daniel Koller wrote:
>

>>I'll check and see what's in there.   And when I take them out, I'll sell them on e-bay to an audiophool!!
>>http://www.ebay.com/itm/4-TUBE-AMP-CAPACITORS-0-1uF-400V-Sprague-Bumblebee/171185528791?_trksid=p2047675.m1982&_trkparms=aid%3D333005%26algo%3DRIC.FIT%26ao%3D1%26asc%3D177%26meid%3D3232141210003616509%26pid%3D100009%26prg%3D1088%26rk%3D1%26rkt%3D5%26sd%3D181276706729%26
>>
>>(No affiliation with the seller!)
>>
>>Dan
>>
>>On Friday, December 6, 2013 11:27 PM, Chuck Harris wrote:
>>
>>>Most of the time with the 545, the problem is the
              black beauty oil/paper
>>>tubular capacitors used for the HV filters.  They
              always go bad, and if
>>>they haven't been replaced, you must replace
              them.  Ceramic is fine.
>>>
>>>There is also a BB cap that is in series with the grid
              feedback winding,
>>>and another in parallel with the plate winding.  Both
              must go.
>>>
>>>-Chuck Harris
>>>
>>>Daniel Koller wrote:
>>>> Howdy,
>>>>
>>>> The recent discussions on HV repairs has me
              thinking I should look into the issues
>>>> in my 545 (not A or B, old style square case).  
              It works very very well, but
>>>> about half of the time, increasingly more, the HV
              circuit will not oscillate.  If
>>>> I pull the plug-in out and drop it back in, it
              will work.  I know this is not a
>>>> recommended option!  Alternatively, if I shut it
              off and wait for it to cool, it
>>>> will work when I turn it on with about the same
              probability, or a little less.
>>>> Once the scope is on it's up to spec.
>>>>
>>>> The 6AU5 is not brand new, but is good.  It was
              replaced recently with no
>>>> improvement.
>>>>
>>>> So, suggestions as to where to start on this
              intermittant problem are welcome.  Is
>>>> there anything I should look for or measure that
              might indicate what is getting
>>>> tired?
>>>>
>>>> Dan
>>>>
>>>
>>>
>>>
>>>
>>
>
>
>>________________________________
>
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Re: 647 HV transformer

alexeisenhut@...
 

Eh, just noticed there's a nice database system right here.
Just click on database ^^^^ up there somewhere.


Re: 647 HV transformer

alexeisenhut@...
 

Maybe we should keep a database of 547s by S/N and if they had the transformer rebuilt?
Might be good come selling time.
https://docs.google.com/spreadsheet/ccc?key=0Akq_eqQcegmedGxheXl5aFRhU3FnQm9LOEpsamdFLXc&usp=sharing


Re: How to open a scope?

Reed Dickinson
 

I have experienced that same problem also.  Go to Harbor Freight and buy a 'slim Jim' or use a long piece of hacksaw blade.  The slim Jim is a long piece of tough thin steel used to open car doors.  Slide the slim Jim or bladeinside the case and work it around until you feel an obstruction.  Then examine the outside and look carefully for any anomolies in the outside case.  The screws holding the handle might be loose and catching on the chassis as you try to slide it out.  Pulling the handles outwards might make it clear.

Good luck

Reed Dickinson


On 12/7/2013 12:34 AM, machineguy59@... wrote:
 

The handles on some scopes can be damaged/bent and get hung up on the chassis rear plate as the case slides out.  Sometimes you can feel the handles bind when the case stops moving.  Try pushing the case back in slightly and then pull the handles out as you try to remove it again.  You might be able to feel if the handles bind up as the case slides. 



Re: 647 HV transformer

Cliff White
 

Is there any way to tell if a Tek transformer has wax or epoxy? I have a small suspicion that the tranny in my 536 has been replaced -- Possibly with one with epoxy. Were replacement transformers ever made with epoxy?



Respectfully,
Cliff White, W5CNW
w5cnw@...

On 12/06/2013 12:13 PM, Chuck Harris wrote:
 

To my knowledge, there are no "good" 547/545B transformers made
by tektronix. They all will fail given time, and the right environmental
conditions... unconditioned space, basements, etc. are really bad
for 547 transformers... as is lack of use.

There are quite a few 547's that have transformers made by Bill Schell,
and by me. They should be good for the long haul. There are so many
out there that surely some have changed hands by now.

-Chuck Harris

David wrote:
> Your hypothesis fits with other design choices that Tektronix made and most
> other companies make. Minimizing R&D expense by reusing existing designs with a
> minimum of alteration is great up until the loss of institutional knowledge
> causes problems. It is easier to quantify an initial hard dollar expense in
> time and money versus a later speculative loss that can only be estimated until
> it is too late by which time the loss has already occurred and is ongoing.
>
> Maintaining institutional knowledge is an expense with no immediately
> quantifiable benefit.
>
> I have not attempted to refurbish my 547 yet because I have no immediate need to
> use it until I get a uniquely useful plug-in for it like a sampler, TDR, or
> spectrum analyzer. Did any 547 oscilloscopes *not* have the bad epoxy
> transformer?
>



Re: 545 HV won't oscillate 100% of the time.

Daniel Koller
 

Hi all,
  My caps probably are bad.  When I first got the scope around 1980, I learned about "black beauties" and had to replace them in the power supply, but I think I recall being told that the bumble-bee types were fine, so those stayed in.  Now it looks like I have leakage from them in the HV power supply.  See the attached photo here: http://groups.yahoo.com/neo/groups/TekScopes/photos/albums/158207078/lightbox/1517700781
The two shiny black 0.001 uF caps stand out because they are coated in oil.  You can't see it on the photo, but there is a film of liquid oil between the middle cap and the 56K resistor below it.  Those two are coming out but being a big fan of "don't mess with it if it ain't broke" I might leave the other caps in unless there is an obvious failure. Mind you, my scope works well when it does turn on.

But I've had some other modifications it seems.  What's that square cap on the left and the 2.2K resistor doing there?  I'll have to trace the circuit to see where they were put in and why.  Maybe that was a long ago patch for the oscillator failure?  Or the cause of it now?

I see now why I had originally thought my scope was much younger than it is - before I learned from the group here that the "brown" Teks were pre-1954.  There is this circuit board in my scope:
http://groups.yahoo.com/neo/groups/TekScopes/photos/albums/158207078/lightbox/1026393052
Someone seems to have made factory improvements circa 1967.   What was in its place before this?  Is it possible my additional HV circuit components were placed in the same upgrades/refurbishment?

Back to the shop.  I've got an hour before guests arrive!

Dan

On Saturday, December 7, 2013 10:58 AM, Don Black <donald_black@bigpond.com> wrote:


I'm not so sure. Yours may be faulty, these are tested good so they must be a rare animal.

Don Black.

On 08-Dec-13 2:31 AM, Daniel Koller wrote:

 
I'll check and see what's in there.   And when I take them out, I'll sell them on e-bay to an audiophool!!
http://www.ebay.com/itm/4-TUBE-AMP-CAPACITORS-0-1uF-400V-Sprague-Bumblebee/171185528791?_trksid=p2047675.m1982&_trkparms=aid%3D333005%26algo%3DRIC.FIT%26ao%3D1%26asc%3D177%26meid%3D3232141210003616509%26pid%3D100009%26prg%3D1088%26rk%3D1%26rkt%3D5%26sd%3D181276706729%26

(No affiliation with the seller!)

Dan

On Friday, December 6, 2013 11:27 PM, Chuck Harris <cfharris@erols.com> wrote:

Most of the time with the 545, the problem is the
              black beauty oil/paper
tubular capacitors used for the HV filters.  They
              always go bad, and if
they haven't been replaced, you must replace
              them.  Ceramic is fine.

There is also a BB cap that is in series with the grid
              feedback winding,
and another in parallel with the plate winding.  Both
              must go.

-Chuck Harris

Daniel Koller wrote:
Howdy,

The recent discussions on HV repairs has me
              thinking I should look into the issues
in my 545 (not A or B, old style square case).  
              It works very very well, but
about half of the time, increasingly more, the HV
              circuit will not oscillate.  If
I pull the plug-in out and drop it back in, it
              will work.  I know this is not a
recommended option!  Alternatively, if I shut it
              off and wait for it to cool, it
will work when I turn it on with about the same
              probability, or a little less.
Once the scope is on it's up to spec.

The 6AU5 is not brand new, but is good.  It was
              replaced recently with no
improvement.

So, suggestions as to where to start on this
              intermittant problem are welcome.  Is
there anything I should look for or measure that
              might indicate what is getting
tired?

Dan



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Re: 536 HV Dropping Off (and other random issues)

Albert Otten
 

I would certainly test HV again with the CRT still removed. CRT anode lead well insulated.

Albert


Re: 647 HV transformer

Albert Otten
 

(coninued)
I forgot to mention (well, thought of it later on) that both heater windings in the 564 are at the same transformer leg. The other leg is empty. So there is no need to equalize. I didn't expect this, otherwise I would have chosen a 564 with two 5642s.

Albert


Re: 536 HV Dropping Off (and other random issues)

Cliff White
 

We seemed to have started a trend of HV threads!

Thanks for the clarification on the transformer test and the center tap of the primary. I guess I need to read up on Hartley oscillators!

I went ahead and pulled the CRT to check the anode connection. There was a little dust around it, but not too much. I've cleaned it up anyway. On that note, are there any tests y'all recommend while I have the CRT disconnected?

Also, is it possible I'm dealing with the same transformer epoxy issue? Maybe because of a replaced transformer? Is there a way to identify what material the transformer is potted in? I noticed the CRT appears to have been replaced -- The CRT itself has a property sticker on it, one on the neck and one on the base.


Respectfully,
Cliff White, W5CNW
w5cnw@...

On 12/05/2013 04:39 PM, kaboomdk@... wrote:
 


Hi Cliff,
  Wow, that's a neat test.  Seeing the primary voltage and the secondary change in lockstep sure seems to vindicate the transformer.  The voltages should remain in the same ratio as the turns ratio, unless perhaps you saturate the core and then it deviates further from an Ideal transformer.

One other thing to try might be to remove intensity circuit by removing V842 (at least partially and connecting an 8MOhm resistor across that transformer winding to give it a similar load as it has now.
That will leave nothing but the CRT anode circuit on the HV side.   On that note, is the anode clean, without dust around the connection point?  Are we are sure there are no discharge paths over the surface of the CRT?

Before you do that, measure the voltage across the intensity pot as Albert recommended.  

What have we done to vindicate R804, R805?  Still assuming all the caps are good.

Dan

---In TekScopes@..., wrote:

I ran another wire through the transformer once like you mentioned. I used another scope and calculated the RMS value. It started at 1.9 and went down to 1.0. Note that the circuit is still cut at R855, which might be causing the higher voltage. Also I think my winding is closer to a full turn than the real filament winding.

I then put a scope probe on the primary side of the transformer (AC-coupled). I set up the monitor scope such that both signals were stacked (appeared to be only one trace) by adjusting the variable v/cm control on one channel. When the fade out happened, they went down exactly together. I *think* this means the transformer's efficiency isn't changing. True? If so would that mean the transformer is not at fault, I think, although I'm not to certain about this part. Can anyone offer insight to that?

Then I added a diode clamp from pin 6 of V816 to the +100 supply. Note that the circuit is still cut at R855. Here's the values in that scenario.

Primary (pin 5, V800): 415ish to 325 (p-p)
"Filament" (my "winding"): 1.7 to 1.3 (rms) (compare that to the first time w/o clamp above)
DC Output (junction of R855 and C855): -950 to -630 (dc)
R807 (referenced to transformer end): 10.03 to 9.67 (dc) Should I measure this with the scope also? I can use my Type W differentially.



Respectfully,
Cliff White, W5CNW
w5cnw@...
On 12/05/2013 05:30 AM, aodiversen@... wrote:
 

Well, that rules out a possible tube fault at the primary side.
The diode heaters nominally receive 1.25 V AC from the single-turn "windings" through the transformer. This is 50 kHz AC (no DC component), so your DMM must be suitable for that frequency. It would be nicer, if possible, to guide an additional well insulated wire through the transformer and then view the induced voltage at an other 'scope. In my opinion you can only find a decrease to some 75% of nominal.
I don't know whether V800 can deliver more and more power when the screen voltage rises so extreme. Hence my suggestion to clamp the screen with a diode to the +100V supply. Then the change in primary AC swing during warming up will indicate whether the secundary load increases or decreases. Perhaps the AC swing reduces like before or even further now, for sure indicating now an increasing load at V800. But then the secundary load decreases  (less heater power and less power at the DC outputs, assuming again you already eliminated possible DC leakage by cap replacements). Hence that would imply leakage in the the secondary windings or leads. Again the reasoning is that the DC outputs collapse because of the reduced heater voltages, not because of the reduced secundary HV voltages.
I would also monitor the voltage across R807. At higher load the anode current will increase. (BTW I think R807 would burn out when its resistance increases dramatically.)

BTW did you measure DC across the Intensity pot? Should normally be slightly over 100 V.

Albert

 




Re: bama edebris manual uploads

alexeisenhut@...
 

That's good.
Sent it just now. It's just a manual for the 1S1 plugin but it's just so awesomely well done by a really good guy I have to share it.


Re: How to open a scope?

danishcah@...
 

My 465's also hang up solid on the grounding tab extension(s) and or the screwhead, as these protrude right out to the inside surface of the case. These can be found on any of the 4 sides, some of mine have been removed or just the tab removed, leaving a "stud" sticking out for no other reason than to catch on the case...  Dana  d:)>


Re: bama edebris manual uploads

Dave / NR1DX
 

Use KO4BB.com instead

On 12/7/2013 10:12 AM, alexeisenhut@... wrote:
 

Has anyone uploaded a manual there and notified ed? I did and never heard back. My upload is still sitting in the uploads directory so the file is there.

Too bad, it's a good idea.



-- 
Dave
Manuals@...
www.ArtekManuals.com



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Re: 647 HV transformer

Albert Otten
 

Intriguing thing those equilizing "8" windings. Chuck (private mail) suggested that these would perhaps first of all serve to equalize the heater voltages. I happens that one of my 564's has one 5642 and one semiconductor diode (done by previous owner), without equalizing loop. I guided additional wires through both holes of the EI-core and did waveform and rms voltage measurement at these.
heater side leg:  0.9 V
empty leg:         1.4 V
The heater current tries to prevent flux changes, so to some extend these prefer the empty leg and hence the induced voltage is higher there.
With a 6.8 Ohm load at the empty leg side wire the heater side voltage increased to 1.0 V.
The 'scope works normally with calibtrated HV IIRC. So the low 0.9 V (rounded up from 0.88 V) heater voltage seems sufficient for normal emission of the 5642.

Albert


Re: bama edebris manual uploads

 

Another good site for uploading manuals and firmware for test equipment is http://www.KO4BB.com .
 
Regards
 

----- Original Message -----
Sent: Saturday, December 07, 2013 11:12 AM
Subject: [TekScopes] bama edebris manual uploads

 

Has anyone uploaded a manual there and notified ed? I did and never heard back. My upload is still sitting in the uploads directory so the file is there.

Too bad, it's a good idea.


bama edebris manual uploads

alexeisenhut@...
 

Has anyone uploaded a manual there and notified ed? I did and never heard back. My upload is still sitting in the uploads directory so the file is there.

Too bad, it's a good idea.


Re: 545 HV won't oscillate 100% of the time.

Don Black <donald_black@...>
 

I'm not so sure. Yours may be faulty, these are tested good so they must be a rare animal.

Don Black.

On 08-Dec-13 2:31 AM, Daniel Koller wrote:
 

I'll check and see what's in there.   And when I take them out, I'll sell them on e-bay to an audiophool!!
http://www.ebay.com/itm/4-TUBE-AMP-CAPACITORS-0-1uF-400V-Sprague-Bumblebee/171185528791?_trksid=p2047675.m1982&_trkparms=aid%3D333005%26algo%3DRIC.FIT%26ao%3D1%26asc%3D177%26meid%3D3232141210003616509%26pid%3D100009%26prg%3D1088%26rk%3D1%26rkt%3D5%26sd%3D181276706729%26

(No affiliation with the seller!)

Dan

On Friday, December 6, 2013 11:27 PM, Chuck Harris wrote:

>Most of the time with the 545, the problem is the black beauty oil/paper
>tubular capacitors used for the HV filters.  They always go bad, and if
>they haven't been replaced, you must replace them.  Ceramic is fine.
>
>There is also a BB cap that is in series with the grid feedback winding,
>and another in parallel with the plate winding.  Both must go.
>
>-Chuck Harris
>
>Daniel Koller wrote:
>> Howdy,
>>
>> The recent discussions on HV repairs has me thinking I should look into the issues
>> in my 545 (not A or B, old style square case).   It works very very well, but
>> about half of the time, increasingly more, the HV circuit will not oscillate.  If
>> I pull the plug-in out and drop it back in, it will work.  I know this is not a
>> recommended option!  Alternatively, if I shut it off and wait for it to cool, it
>> will work when I turn it on with about the same probability, or a little less.
>> Once the scope is on it's up to spec.
>>
>> The 6AU5 is not brand new, but is good.  It was replaced recently with no
>> improvement.
>>
>> So, suggestions as to where to start on this intermittant problem are welcome.  Is
>> there anything I should look for or measure that might indicate what is getting
>> tired?
>>
>> Dan
>>
>
>
>
>





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Re: 545 HV won't oscillate 100% of the time.

Daniel Koller
 

On Friday, December 6, 2013 11:27 PM, Chuck Harris <cfharris@erols.com> wrote:


Most of the time with the 545, the problem is the black beauty oil/paper
tubular capacitors used for the HV filters.  They always go bad, and if
they haven't been replaced, you must replace them.  Ceramic is fine.

There is also a BB cap that is in series with the grid feedback winding,
and another in parallel with the plate winding.  Both must go.

-Chuck Harris

Daniel Koller wrote:
Howdy,

The recent discussions on HV repairs has me thinking I should look into the issues
in my 545 (not A or B, old style square case).   It works very very well, but
about half of the time, increasingly more, the HV circuit will not oscillate.  If
I pull the plug-in out and drop it back in, it will work.  I know this is not a
recommended option!  Alternatively, if I shut it off and wait for it to cool, it
will work when I turn it on with about the same probability, or a little less.
Once the scope is on it's up to spec.

The 6AU5 is not brand new, but is good.  It was replaced recently with no
improvement.

So, suggestions as to where to start on this intermittant problem are welcome.  Is
there anything I should look for or measure that might indicate what is getting
tired?

Dan



Re: How to open a scope?

Tim Phillips <tim@...>
 

from Tim P (UK)
I had to wrestle the case off my 453 - turned out there was a piece of sprung metal which (I guess) was to ground the scope chassis to the case. This had got stuck somehow and was binding somewhere on the metalwork. Gentle encouragement with a wooden Kebab skewer moved it enough to slide the case.
Tim
 

----- Original Message -----
From: gmail
Sent: Friday, December 06, 2013 10:49 PM
Subject: [TekScopes] How to open a scope?

 

Someone brought a Tek 2221 along tonight to do some measurements, which hadn't been used for a while. After some 15 minutes on, magic smoke escaped from the back. I'm guessing it is the usual suspect. So we tried to open the scope and we could only slide it out of the cover for nearly half the distance. Then it got really stuck. The scope was not opened up lately. Anyone with tips and tricks for this, or is it just brute force?
 
Thanks,
Guido


Re: How to open a scope?

 

The handles on some scopes can be damaged/bent and get hung up on the chassis rear plate as the case slides out.  Sometimes you can feel the handles bind when the case stops moving.  Try pushing the case back in slightly and then pull the handles out as you try to remove it again.  You might be able to feel if the handles bind up as the case slides. 


Re: 545 HV won't oscillate 100% of the time.

Chuck Harris <cfharris@...>
 

Most of the time with the 545, the problem is the black beauty oil/paper
tubular capacitors used for the HV filters. They always go bad, and if
they haven't been replaced, you must replace them. Ceramic is fine.

There is also a BB cap that is in series with the grid feedback winding,
and another in parallel with the plate winding. Both must go.

-Chuck Harris

Daniel Koller wrote:

Howdy,

The recent discussions on HV repairs has me thinking I should look into the issues
in my 545 (not A or B, old style square case). It works very very well, but
about half of the time, increasingly more, the HV circuit will not oscillate. If
I pull the plug-in out and drop it back in, it will work. I know this is not a
recommended option! Alternatively, if I shut it off and wait for it to cool, it
will work when I turn it on with about the same probability, or a little less.
Once the scope is on it's up to spec.

The 6AU5 is not brand new, but is good. It was replaced recently with no
improvement.

So, suggestions as to where to start on this intermittant problem are welcome. Is
there anything I should look for or measure that might indicate what is getting
tired?

Dan

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