On Wed, Nov 24, 2021 at 10:12 AM, pdxareaid wrote:
you will be dealing with mechanical issues when recapping.
here are some ideas:
this is the best solution i have seen when it comes to replacing old caps with
new:
/g/TekScopes/files/Replacing%20Electrolytic%20Filter%20Capacitors%20in%20a%20Tektronix%20465.pdf
here is another (i used this a few times before i knew about
better...imo...solution above):
Phil, I have been repairing 475's lately, so I have been using the discs from E-bay. I really like the "standoff board" concept and I will contact Barry off list to see if he has some of these boards so that I will have one on hand for my next 465. The discs are a good option as well, just not as simple the next time the caps require replacement. Getting the old caps out without damaging the PC board is still the bigger issue. Lots of patience required. Regardless, the power supply ripple must be brought under control or further troubleshooting will be futile. . -- Michael Lynch Dardanelle, AR
|
I think the examples shown by Rehorn are too nice. The signals are periodic and exactly an integer number of periods fits in the sampling period. He must have made use of that information to arrive at an exact reconstruction (using the periodic extension of sampled data), without saying so. I wonder what the results would look like when a later on mentioned general interpolation process is used.
Albert
|
|
|
If you look at
you will find the spec of most of the Russian tunnel diodes you are likely to find. You need Germanium, not Gallium Arsenide, 'switching', and a peak current Ip that matches the spec of the original part. I think Ip was 4.7mA for the 454 diodes, the 453 may well be different. The Russian parts do not have a tight spec for the capacitance, low capacitance gives a faster switching speed, I doubt that the switching speed is critical for the 50MHz 453. When I was looking at the Russian tunnel diodes some years ago it was much easier to find the stripline packages rather than the wire ends.
Roger
|
Re: Looking for 7704A - J290L (Power for Readout)
Please excuse the TYPO in the subject line. That should read:
Looking for 7704A - J20L (Power for Readout)
I hit the 9 key by mistake and didn't notice it until I saw the message coming back from the reflector.
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "n4buq" <n4buq@...>
To: "tekscopes" <[email protected]>
Sent: Wednesday, November 24, 2021 9:31:43 AM
Subject: [TekScopes] Looking for 7704A - J290L (Power for Readout) Could someone please point me to the schematic location of J20L on the Main
Interface board for a 7704A? According to the schematic for the READOUT board,
the cable for P34L (the power rail connection for the Readout Board) is
terminated on the other end at P20L which plugs in to J20L on the Main
Interface board but I cannot find J20L on the schematic for the Main Interface
(or anywhere else). It is clearly shown on the picture of the Main Interface
board (along with the grid location) and I know where J20L is physically on the
board, etc., but I just cannot find it on the schematic.
Thanks,
Barry - N4BUQ
|
Looking for 7704A - J290L (Power for Readout)
Could someone please point me to the schematic location of J20L on the Main Interface board for a 7704A? According to the schematic for the READOUT board, the cable for P34L (the power rail connection for the Readout Board) is terminated on the other end at P20L which plugs in to J20L on the Main Interface board but I cannot find J20L on the schematic for the Main Interface (or anywhere else). It is clearly shown on the picture of the Main Interface board (along with the grid location) and I know where J20L is physically on the board, etc., but I just cannot find it on the schematic.
Thanks,
Barry - N4BUQ
|
can noone give me russian replacement td part numbers then that may work in this 453?
|
Michael.
Im afraid the ripple is all over the place, and not able to see any sawtoot pattern at Q1038.
Will order up new caps for psu and dismantle the board for access. Will order up for both scopes, as the other ona that actually works but looks terrible also suffer from ripple.
Hugo
|
Re: High isolation filament transformers - was Re: [TekScopes] Help with my 661
Stancor P-8191 or Thordarson 26F65 is a 6.3V primary, 6.3V secondary, 1.2 amp, with 5kv isolation.
No idea where you could find one, though...
|
Re: TEKTRONIX 475 VOLTS/DIV
Please call me Tom! :)
--Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
toggle quoted message
Show quoted text
On 11/23/2021 17:27, one6146 via groups.io wrote: As I said to Prof. Lee, D'oh!
Now,I know better, at least, I think I do.
Thanks Mike,
klc
On Monday, November 22, 2021, 04:29:57 PM EST, Michael W. Lynch via groups.io <mlynch003@...> wrote:
That is where the knobs stop in the 1x range.? You should see that there are two small windows above the knob and behind the numbered collar.? The "5" on the clear collar should stop above the left window (illuminated when scope is "on") situated behind the clear collar.? The 10/20/50V ranges are attained by using a properly equipped TEKTRONIX 10X probe which will cause the left side window to go dark and the right side window behind the collar to then illuminate.
The Window to the left is illuminated when the scope is turned on (if the circuit and lamp are not damaged)? and the Window to the right should come on when a TEKTRONIX 10X probe is used which connects the contact ring of the BNC to the ground through a spring loaded pin.? This is called "probe coding".? I hope My attempt to explain makes sense.
|
Re: TEKTRONIX 475 VOLTS/DIV
As I said to Prof. Lee, D'oh!
Now,I know better, at least, I think I do.
Thanks Mike,
klc
toggle quoted message
Show quoted text
On Monday, November 22, 2021, 04:29:57 PM EST, Michael W. Lynch via groups.io <mlynch003@...> wrote:
That is where the knobs stop in the 1x range.? You should see that there are two small windows above the knob and behind the numbered collar.? The "5" on the clear collar should stop above the left window (illuminated when scope is "on") situated behind the clear collar.? The 10/20/50V ranges are attained by using a properly equipped TEKTRONIX 10X probe which will cause the left side window to go dark and the right side window behind the collar to then illuminate.?
The Window to the left is illuminated when the scope is turned on (if the circuit and lamp are not damaged)? and the Window to the right should come on when a TEKTRONIX 10X probe is used which connects the contact ring of the BNC to the ground through a spring loaded pin.? This is called "probe coding".? I hope My attempt to explain makes sense.? ?
--
Michael Lynch
Dardanelle, AR
|
Re: TEKTRONIX 475 VOLTS/DIV
D'oh!
Yes. The probe has the little pin sticking on the connector. Ya need the correct probe !
Thank you,
klc
toggle quoted message
Show quoted text
On Monday, November 22, 2021, 04:18:02 PM EST, Tom Lee <tomlee@...> wrote: I assumed that someone would've answered you earlier, but I don't see any reply (but I only just got your post, so maybe relevant messages are stuck in the Great Cloud somewhere). In any case, the higher voltage ranges correspond to the scope being used with a 10:1 probe. The scope itself does not have those higher ranges. If you look carefully, there are two illuminators behind the knob skirts. The higher range one lights up when a 10:1 probe with the right dingus (to tell the scope that it's a 10:1 probe) is used. Random third-party probes rarely have this feature, so you have to keep the factor of 10 straight in your head. So, stop trying to rotate the knob further. :) -- Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 11/19/2021 18:05, K Cleary via groups.io wrote: The VOLTS/DIV knob for Both channels 1 & 2 will not rotate? past the 5 volt indicator. The lower ranges act normally.It would be nice to have the 10/20/50 Volt ranges working.
Searching 'here',it doesn't appear to be a common problem, but I have to ask, before I venture * inside *.
Any help is appreciated.
klc
|
Re: Tek 7104 finally fixed
Stefano,
Another way you can replace the low voltage electrolytic is to use #10 screws, star washers and nuts to secure them where the screw mounts are. The leads of the capacitor can be bent around the bolt and secured. That would make sure both sides of the board have electrical contact. Restuffing the screw types with other styles I had to figure out since I have not seen how others have done it. My way works for me.
Mark
|
Re: Tek 7104 finally fixed
Hello Mark, thank you for the advise for the 741 on the horizontal amplifier, I'll check that one too. Actually I still have to do a few hours burn in test (hoping nothing will burn!) of the 7104, so far I had it powered on only for some minutes with no problems.
Calibration... I read the service manual and in my understanding it costs a fortune! I think I will keep it as it is because first I use it only for my hobby, I'm not a R&D guy; second, I really do not know who can calibrate it here in Italy and, moreover, I have no assurance that someone has all the specific and calibrated instruments to calibrate a 1978 oscilloscope. I wouldn't spend hundreds of euros with no sure result,
Going back to the capacitors, thanks for the hint. I searched replacements with screws and not snap-in type, but I'll keep in mind your suggestion for the high voltage ones. Quite tricky is the low voltage one that has super-extremely low ESR. I found only a Cornell Dubilier - CDE 2200uF 75V but the distance of the screws is greater than the original one, that's why I decided not to restuff it.
Stefano
|
High isolation filament transformers - was Re: [TekScopes] Help with my 661
On 2021-11-23 3:33 p.m., Torch wrote: Hammond Manufacturing still makes some "classic" filament transformers and I think a few are hipot tested to 4kv.
EG: 185E12. Primary 115/230. Secondary 6.3vac, 4A (in parallel -- 12.6vac 2A center tapped in series). Hipot tested to 4kv.
Catalog is here:
Yes, mains voltage primary types are widely available. But if anyone knows where to look for a lower voltage ratio, e.g. 3:1, 2:1, 1:1, with filament voltage secondary and very high isolation voltages (6kV+), I'd like to know - for a related reason, possibly needing to replace a HV supply... --Toby
|
Hi Torch , I think I have found a solution -- an Ebay seller had a Stancor transformer 6.3v @ 1.2A rated for 5kV at a reasonable price , so I am now just waiting for the post .
Brian (UK)
toggle quoted message
Show quoted text
On Tuesday, 23 November 2021, 20:33:51 GMT, Torch <tekscopes@...> wrote:
Hammond Manufacturing still makes some "classic" filament transformers and I think a few are hipot tested to 4kv.
EG: 185E12. Primary 115/230. Secondary 6.3vac, 4A (in parallel -- 12.6vac 2A center tapped in series). Hipot tested to 4kv.
Catalog is here:
|
Hammond Manufacturing still makes some "classic" filament transformers and I think a few are hipot tested to 4kv.
EG: 185E12. Primary 115/230. Secondary 6.3vac, 4A (in parallel -- 12.6vac 2A center tapped in series). Hipot tested to 4kv.
Catalog is here:
|
Re: Help with an ailing 7D14
Interleaved responses. On 11/23/2021 1:12 PM, k6whp wrote: Harvey, et al,
To directly answer Harvey's immediate questions:
(1) Yes, +15 VDC. OK, then we have the right supply voltage. (2) Yes, per the manual. A lower voltage relay would, of course, draw more power. (3) How would one determine the current being drawn by the relay? Since it's the coil doing all the heating, I'd do the following, a lot "just because". 1) unplug each relay and check the coil resistance.? Since these are DC, impedance is not a problem.? That gives you an idea of what the coil current should be at 15 volts.? (paranoid moment: the supply voltage is correct?). 2) run a relay at the rated coil voltage (less a volt or so for driver drop), and see how warm it gets.? Same as the plugin? 3) in the plugin, measure the voltage across an "on" coil. Very obvious things, though. I'd check the ripple on the supply just because, too. If you have another mainframe other than a 7704A, I'd try that, too. Your diagnosis of the heat problem is reasonable, given what you have done, but I'm puzzled as to why it happens.? If I had a 7D14, I'd look for you, but I don't want to drag out the 7704, it would be a 7904 instead. Don't remember reading much that says "don't use these plugins in these 7000 series frames...." Harvey
I again refer you to the blog entry that provides a more coherent summation of my testing. Perhaps reviewing that and the 7D14 schematic will occasion some suggestions as to how to measure the current being drawn by any of these relays.
As to Barry's suggestion, probably a good idea to embark on an examination of the relays separately from the circuit. A whole host of test scenarios come to mind to find out what's "in the box".
To remind you of my theory that the heat generated by the relays cause the problem with the unit. Early on, spraying cold (compressed) air gently over the general area of the Q130A/Q103B and surrounds "cured" the problem, Subsequently, placing a muffin fan over the two horizontal bays allowed the 7D14 to operate problem free without incident. (That is, I tested it for six hours running with no problems.)
Anyone familiar with a 7704A knows that the unit is cooled by a rather weak fan mounted such that the airflow is directed horizontally towards the more aft section of the unit and well away from the fronts of the four bays.
I may have been attempting to solve the wrong problem.
Will report back; thanks for the suggestions.
|
On Mon, Nov 22, 2021 at 02:31 PM, Tom Lee wrote:
If you wish to debate this, please do so off list to limit the thread derail.
Hi Tom, I disagree. There are those here to learn, those here to expound, those here for clarification, Those here... So long as any debate is civil, I for one am all for a clear hearing. larry
|
Re: Help with an ailing 7D14
Harvey, et al,
To directly answer Harvey's immediate questions:
(1) Yes, +15 VDC.
(2) Yes, per the manual.
(3) How would one determine the current being drawn by the relay?
I again refer you to the blog entry that provides a more coherent summation of my testing. Perhaps reviewing that and the 7D14 schematic will occasion some suggestions as to how to measure the current being drawn by any of these relays.
As to Barry's suggestion, probably a good idea to embark on an examination of the relays separately from the circuit. A whole host of test scenarios come to mind to find out what's "in the box".
To remind you of my theory that the heat generated by the relays cause the problem with the unit. Early on, spraying cold (compressed) air gently over the general area of the Q130A/Q103B and surrounds "cured" the problem, Subsequently, placing a muffin fan over the two horizontal bays allowed the 7D14 to operate problem free without incident. (That is, I tested it for six hours running with no problems.)
Anyone familiar with a 7704A knows that the unit is cooled by a rather weak fan mounted such that the airflow is directed horizontally towards the more aft section of the unit and well away from the fronts of the four bays.
I may have been attempting to solve the wrong problem.
Will report back; thanks for the suggestions.
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"
|
Michael W. Lynch
Brian
k6whp