Whats the expected effect of freezing. Worse or better?

Inasmuch as the scope (occasionally) operates correctly when 'cool' (i.e. during warm-up) -- expect the freezing spray to momentarily 'correct' the problem when applied to the 'trouble spot'

Best regards
HP

 

Re your questions in post #192:

- I have been checking on the tube and discovered that -Vg1 is 21V; in the tube description the range mentioned is 75-35 V. I measured relative to the cathode. Think EMF NOT OK.

The beam cut off range is (-75) through (-35) volts per kilovolt applied to anode #1 (a1) --- Whereas the absolute maximum applied voltage range is (-200V) through (-1V) --- hence your reading (-21V) is not inconsistent with proper operation!

- In tube description I read : pda spiral resistance: whats that?

The Post Deflection Acceleration 'electrode' (a4) is implemented as a graphite spiral 'printed' on the envelope of the tube -- (The referanced specification indicates that the resistance of said spiral = 75MΩ)

- I also read on p 4 of tube description you provided: Vs (pattern correction Voltage):What is that and where can I measure that?

Geometry correction is achieved via 'bias' on 's' (Pin 9) -- Note, however, that the presenting symptoms are not consistent with difficulty in this area!

- I measured over R309 (2.2K): 187V

over R306 and R308: O V (guess R306 NOT OK; 308 OK)

over R306 and R308: O V (guess R306 NOT OK; 308 OK)

Inasmuch as the appropriacy of the above cited readings is contingent upon many conditions (i.e. control positions, modes, etc..) we'll leave them in abeyance for the nonce --That said, we'll revisit them should they 'lie in the path' of the troubleshooting process...

Very best regards
HP

 

Please print hard copies of Figure #3 and Figure #5 (below) for ready reference:

Figure 3

Figure #5

 

Alright -- first of all let's investigate the anomalous interaction of horizontal position and intensity:

-Observe EMF across R69 while varying R301 over its range
Please post E(R69) for CCW, Mid and CW positions of R301

-Observe EMF at test point 156/12 (Figure 5) while varying R301 over its range
Please post E(test point 156/12) for CCW, Mid, and CW positions of R301

Best regards
HP

 

Thanks for all info Hypatia. I'll be away for a few weeks and at my return i'll check the points you mentioned above;In the mean time, have some nice weeks!

 

Thanks for all info Hypatia. I'll be away for a few weeks and at my return i'll check the points you mentioned above;In the mean time, have some nice weeks!

You too! -- And please rest assured we will get it working! -- I haven't been 'beaten up' by an O'scope yet!

Have a pleasant vacation!
Best regards
HP

 

Alright -- first of all let's investigate the anomalous interaction of horizontal position and intensity:

-Observe EMF across R69 while varying R301 over its range
Please post E(R69) for CCW, Mid and CW positions of R301

-Observe EMF at test point 156/12 (Figure 5) while varying R301 over its range
Please post E(test point 156/12) for CCW, Mid, and CW positions of R301

Best regards
HP

Hallo Hypatia; all OK?
On the first test: On R69 (at slider) and R69 in MID position::
R301: CCW/MID AND CW -0,92 (no change with R301):
(turning R69 itself the slider goes from-12,18V ( in CCW) to 0 V (in CW) )

The second test: at 156/12:
R301 CCW: 118.9
R301 MID: 118.9
R301 CW: 118.7

 

Since I find the --12,18V a bit high (should be -13V) and I do not have the fenomenon of the fulll visibility of the baseline at warming up anymore, I remeasured tensions
WALL: 232V AC ;
AC at TRAFO;
expected and measured V
234; 233
214;213
117;114
107;104
100;92
13; 12
13;12

TRAFO temperature feels normal; at ELCO's also;

 

@patpin -- Nice to see you back on the fora!

I apologize that, between the exigencies of 'real life' and prior commitment to @Aleph(0) 's EHT thread, I may be 'scarce' for the next week or so... In the meantime, please keep an eye on this thread as I will post observations/questions/suggestions as time permits (Moreover, assistance from other members may be forthcoming!) --- I expect to be in a position to offer you my (well-neigh) 'undivided attention' beginning on or about the week of March 7

Thanks for the readings! -- I will analyze same and try to post conclusions/ 'next steps' sometime tomorrow

Very best regards
HP

 

@patpin -- Nice to see you back on the fora!

I apologize that, between the exigencies of 'real life' and prior commitment to @Aleph(0) 's EHT thread, I may be 'scarce' for the next week or so... In the meantime, please keep an eye on this thread as I will post observations/questions/suggestions as time permits (Moreover, assistance from other members may be forthcoming!) --- I expect to be in a position to offer you my (well-neigh) 'undivided attention' beginning on or about the week of March 7

Thanks for the readings! -- I will analyze same and try to post conclusions/ 'next steps' sometime tomorrow

Very best regards
HP

Thanks Hypatia; no hurry. In the mean time I bought a bitcope BS05. Probably it will help to debug on the antique scope... but i'll have to learn it first.

 

Did a test with bitscope with Time/div on 10 µS on testpoint 156/G and get: pulse with 41,6V peak to peak an duration of 130µS

When I do the same on point 156/F I get the reverse pulse (as in the manual) but with peak to peak 16V;

 

Did a test with bitscope with Time/div on 10 µS on testpoint 156/G and get: pulse with 41,6V peak to peak an duration of 130µS
View attachment 101348
When I do the same on point 156/F I get the reverse pulse (as in the manual) but with peak to peak 16V;

While I haven't had time to study your results yet, I felt I must advise you to please exercise extreme caution while 'prodding about' with your digital scope! Case in point; the deflection plates (of the instrument under test) are near acceleration potential (with respect to the cathode) -- Please, always make doubly certain that maximum P-P EMFs aparent under a proposed test condition cannot exceed your digital scope's maximum input rating under the worst-case fault scenario! Moreover, please be wary of 'shorting out' the test circuit via the test scope's return lead! -- Digital instruments seldom grant second chances!

I promise to have a good look at your results ASAP!

Best regards
HP

 

While I haven't had time to study your results yet, I felt I must advise you to please exercise extreme caution while 'prodding about' with your digital scope! Case in point; the deflection plates (of the instrument under test) are near acceleration potential (with respect to the cathode) -- Please, always make doubly certain that maximum P-P EMFs aparent under a proposed test condition cannot exceed your digital scope's maximum input rating under the worst-case fault scenario! Moreover, please be wary of 'shorting out' the test circuit via the test scope's return lead! -- Digital instruments seldom grant second chances!

I promise to have a good look at your results ASAP!

Best regards
HP

 

I am taking care of protecting the bitscope by measuring with DVM on DC and AC before connecting and even then always use 10:1 probe first.

 

Other measurment on 156/F: peak to peak about 4V; medium level 104V; NOT OK; exchanging TR33 for TR37 and viceversa: no effect;

 

Hello I measured between the 2 bases of TR33 and TR37 and found 143 ohm in circuit. Then I desoldered C44 fast since it is PS : It is a short.
I'll brief U treat as soon as a substitute is found. It's a 1.5 nF "PS"..Can I replace it with a ceramic like http://www.conrad.be/ce/nl/product/...r-1500-pF-400-VAC-20-1-stuks?ref=searchDetail
Thanks

 

I am taking care of protecting the bitscope by measuring with DVM on DC and AC before connecting and even then always use 10:1 probe first.

Kudos! --- I apologize should my post have seemed a tad condescending! --- It's merely that I've seen too many cases of test equipment damage owed to negligent application of same -- Clearly, you know what's to be appreciated in the ways of caution!

C44 fast since it is PS : It is a short

--Emphasis added--
Sounds promising!

t's a 1.5 nF "PS"..Can I replace it with a ceramic

Polystyrene (dielectric) Caps exhibit a high degree of stability/predictability over temperature -- hence my strong recommendation that replacement is with another Cap of the same type! --- That said, if there will be a delay in acquisition of a proper replacement - you may certainly temporally substitute it with an appropriately specified ceramic type (to determine the extent to which the difficulty has been isolated)

Good luck!
HP

 

Kudos! --- I apologize should my post have seemed a tad condescending! --- It's merely that I've seen too many cases of test equipment damage owed to negligent application of same -- Clearly, you know what's to be appreciated in the ways of caution!



--Emphasis added--
Sounds promising!



Polystyrene (dielectric) Caps exhibit a high degree of stability/predictability over temperature -- hence my strong recommendation that replacement is with another Cap of the same type! --- That said, if there will be a delay in acquisition of a proper replacement - you may certainly temporally substitute it with an appropriately specified ceramic type (to determine the extent to which the difficulty has been isolated)

Good luck!
HP

Ok i'll look for a ceramic one first.
Hope I didnt destroyed it by desoldering...


Hello, Where can one find such PS caps? Dont find them at the current stores overhere.
Hello, Where can one find such PS caps?

 

Hello, Where can one find such PS caps? Dont find them at the current stores overhere.

I'll check it out and get back to you -- with, hopefully, specific link{s} to vendor{s}

 

Hello, Where can one find such PS caps

It would be nice if I knew what country you are in.
I use www.mouser.com
There is also Jameco, Digikey, and a few others.
Somewhere on this site is a list of vendors.
If there isn't, there should be.