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Re: No trace on 556 :(
Hello Evan,
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I have what is left of a 556 scope. I just checked and both high voltage (plastic rectangular) enclosures are still in the chassis. The front panel and low voltage transformer are also available. Don't know what condition. Free except whatever it takes to get it out of here. I already took the tunnel diodes and the tubes are missing. Would like to get rid of it. Plus lots of other Tek stuff. Carl (W9CJH) -------------------------------------------- On Thu, 8/2/18, <thespin@...> wrote:
Subject: [TekScopes] No trace on 556 :( To: [email protected] Date: Thursday, August 2, 2018, 8:03 AM Hey all, I just acquired a 556, but it's having some fairly serious issues. Before powering it on, I checked all the supply rails for shorts with a meter, and checked the power plug for shorts as well. I then proceeded to slowly turn the scope on with a variac. Once at full voltage for a few moments, I heard a bang and smelled that something had gone wrong. Surprisingly, the main rails are all healthy (350,225,100,-150). The high voltage on the upper beam is at it's nominal voltage, but the high voltage on the lower beam is around 100 volts. Boooo. Okay... so now I wonder... if the post-deflection acceleration (supplied by the lower beam supply only) is dead, will the CRT still light? What are the chances that I blew up the HV transformer itself and will need to wind a new one? What components are most likely to have exploded in that area? Evan |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
tom jobe
Look at the data sheet for the Nichicon HE series capacitors, in the 'endurance' section it says that the capacitor's life doubles (in hours) when you go up from 6.3 mm to 12.5 mm diameter.
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This fits right in with what you are saying about skinny capacitors. tom jobe... On 8/12/2018 3:43 PM, Mark Goldberg wrote:
On Sun, Aug 12, 2018 at 3:23 PM, tom jobe <tomjobe@...> wrote:Hi Mark,I have been told that skinny electrolytics dry out faster. |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
On Sun, Aug 12, 2018 at 3:23 PM, tom jobe <tomjobe@...> wrote:
Hi Mark,I have been told that skinny electrolytics dry out faster. Regards, Mark |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
tom jobe
Hi Mark,
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That is an interesting point you make about using aluminum electrolytics with a higher diameter to length ratio. A recent capacitor discussion on Tekscopes included links to capacitor data sheets about the brand and series being discussed, and in one of the data sheets I saw that even within the same series of capacitor the ratings went up with larger diameters. Wish I could remember the exact brand and series of capacitor so I could find that same data sheet again. tom jobe... On 8/12/2018 2:58 PM, Mark Goldberg wrote:
On Sun, Aug 12, 2018 at 12:42 PM, machineguy59 via Groups.Io < |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
On Sun, Aug 12, 2018, 17:58 Mark Goldberg <marklgoldberg@...>
Huh. Who knew tantalums could be emotionally conflicted. Mark |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
On Sun, Aug 12, 2018 at 12:42 PM, machineguy59 via Groups.Io <
machineguy59@...> wrote: I don't share your disdain for tantalum electrolytic capacitors. TheirI have been using Kemet T494 series SMD -55 C to +125 C Low ESR Tantalum for a very long time in aviation products and have not had issues. They claim to use "conflict free Tantalum". I have also used high quality electrolytics with higher diameter to length ratios if I needed really big capacitance. Regards, Mark |
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Re: Resurrecting a 475 - Request for Guidance
Can you better identify "J4" or give the capacitor designator from the service manual?
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One of the common failure points is a tantalum 47 uF cap (C1318) that filters the DC supply to the HV generator. There is a choke that may smoke until the fuse gives. Measure the resistance from ground to the fuse. If it is near zero ohms, pull one end of that cap to see if the short clears. If it does, replace the cap. Be sure to only use the correct fuse. Then you can go and check all the low voltage power supply test points. If you have another scope, check the ripple per the service manual. The 475 is a fine scope. Regards ----- Original Message -----
From: "JR" <jswrussell@...> To: <[email protected]> Sent: Sunday, August 12, 2018 3:17 PM Subject: [TekScopes] Resurrecting a 475 - Request for Guidance I have recently become the proud owner of a 475 that I found abandoned at the side of a road! Other than a couple dents in the casing, it appears to be in pretty good condition. After replacing the fuses, I was greeted with what appeared to be a very fuzzy trace when turning the power on. However, very soon afterwards, a resistor directly adjacent to the J4 connector on board A9 (listed in the manual as 'interface circuit board assembly') began to smoke, at which point I powered it off. One of the leads of the resistor in question is connected to the positive side of a orange dipped (tantalum?) capacitor, which leads me to suspect that it may be the culprit, given all that I have read so far regarding worn out and failed capacitors on 400 series scopes. When testing the capacitor in the board, it certainly seems like it's shorted, which I presume would explain the smoke from the adjacent resistor. I'm hesitant to power it on again to check all the rail voltages in case I further damage the resistor. I suppose I should start by verifying which capacitors are good and bad, and replacing the failed ones? In this case, is there a definitive criteria for determining which capacitors are good and which need to be replaced? Or should my attention be directed elsewhere first? Any advice and suggestions would be greatly appreciated. |
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Resurrecting a 475 - Request for Guidance
I have recently become the proud owner of a 475 that I found abandoned at the side of a road! Other than a couple dents in the casing, it appears to be in pretty good condition.
After replacing the fuses, I was greeted with what appeared to be a very fuzzy trace when turning the power on. However, very soon afterwards, a resistor directly adjacent to the J4 connector on board A9 (listed in the manual as 'interface circuit board assembly') began to smoke, at which point I powered it off. One of the leads of the resistor in question is connected to the positive side of a orange dipped (tantalum?) capacitor, which leads me to suspect that it may be the culprit, given all that I have read so far regarding worn out and failed capacitors on 400 series scopes. When testing the capacitor in the board, it certainly seems like it's shorted, which I presume would explain the smoke from the adjacent resistor. I'm hesitant to power it on again to check all the rail voltages in case I further damage the resistor. I suppose I should start by verifying which capacitors are good and bad, and replacing the failed ones? In this case, is there a definitive criteria for determining which capacitors are good and which need to be replaced? Or should my attention be directed elsewhere first? Any advice and suggestions would be greatly appreciated. |
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Re: Acqusition board available, cheap
I would be interested
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On Sun, Aug 12, 2018, 1:00 PM Bruce Lane <kyrrin@...> wrote:
I have a surplus acquisition board, P/N 679-4774-02 (from the |
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Re: Scope
Hi Harvey,
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Thanks for your email. It was very helpful. I was working with the scope for a while, turning it off and on a few times, and finally the screen came up. I suspect that since the scope hadn't been powered up in a long time, it might take a while to initialize, and it seems fine now. Thanks very much. I appreciate your help. Now I have two more Tektronix scopes to fix, and one could be a project. Tom On Sun, Aug 12, 2018, 9:22 AM Harvey White <madyn@...> wrote:
On Sat, 11 Aug 2018 20:31:33 -0700, you wrote: |
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Re: 464
Hi Gypsy, The question is too open-ended. It is expected that you would ask it and then list the 'five' basic tests you ran and their results. The 464 S/M itself has a Troubleshooting chapter for you to read & follow ! You should/must get a copy of the 1998 Tek Manual ; Troubleshooting Your Oscilloscope ; Getting Down to Basics, 068-0315-00. It is one of our Bibles. It's 82 pages and mine is maybe 120 pages with copies of data from my various Tek Scopes and annotations, for example, I made my own index for Ch-7 that's 13 lines long to all out subjects and installed 3-ring dividers to them. You will get help from this great Group, if you show up with Facts and test results.! we cannot read your S/M for you.
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Acqusition board available, cheap
I have a surplus acquisition board, P/N 679-4774-02 (from the label) or
G9F-2841-00 (from the top copper layer). It was, as far as I know, working when pulled out of its host TDS520. The 'scope itself sustained mechanical damage in shipping, though its electronics were not affected. Anyone interested? How does $30 and free shipping within the USA sound? Thanks much. -- --- Bruce Lane, ARS KC7GR kyrrin (at) bluefeathertech dot com "Quando Omni Flunkus Moritati" (Red Green) |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
I don't share your disdain for tantalum electrolytic capacitors.? Their dramatic failure modes to happen when they are operated near their rated voltage.? For this reason, I de-rate their voltage application by more than 4:1.? That seems pretty safe by most accounts.? Also, I chose capacitors with an ESR equivalent or less than the aluminum capacitors they replaced (smaller ones were available at higher ESR).? I know nothing of the "ethics" of tantalum capacitors or their vendors. ?
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On the other hand, I know that SMD aluminum electrolytic capacitors are known to leak electrolyte onto the PCB.? Newer ones may not do it so often, but they do it.? When they do, they nearly always destroy portions of the board.? Tantalum electrolytic capacitors do not leak.? I considered ceramic capacitors but their capacitance values are voltage sensitive and that dictates significant voltage derating for them too. On ?Sunday?, ?August? ?12?, ?2018? ?02?:?20?:?50? ?PM? ?CDT, Hawker <rick@...> wrote:
So you replaced parts who's current main failure mode is less capacitance with a part who's known normal failure modes are burns up in flames taking out the PCB or short circuit taking out the parts before? And we won't even touch on the questionable ethics of Tantalum. I have NEVER seen a quality electrolytic made after the mid 1990s leak unless it was over temperatured or over voltaged. I'm pretty sure that is a bygone problem. Doesn't seem like a smart move to me.? A modern LOW ESR 5k hour 105C electrolytic should be far Superior to Tantalum with the ESR going 2-4 octaves higher with a safer part.? You could possibly use a X7R or X5R MLCC for even lower ESR that goes 10 octaves longer and reliability but some of those older circuits are not ceramic stable and X7R/X5R are micro-phonic, where other options are not. |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
So you replaced parts who's current main failure mode is less capacitance with a part who's known normal failure modes are burns up in flames taking out the PCB or short circuit taking out the parts before? And we won't even touch on the questionable ethics of Tantalum. I have NEVER seen a quality electrolytic made after the mid 1990s leak unless it was over temperatured or over voltaged. I'm pretty sure that is a bygone problem.
Doesn't seem like a smart move to me. A modern LOW ESR 5k hour 105C electrolytic should be far Superior to Tantalum with the ESR going 2-4 octaves higher with a safer part. You could possibly use a X7R or X5R MLCC for even lower ESR that goes 10 octaves longer and reliability but some of those older circuits are not ceramic stable and X7R/X5R are micro-phonic, where other options are not. |
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DM501A AC range calibration
Howdy all.
Was trying to calibrate a DM501A this weekend. DC volts calibrated with no issues however AC volts and dBmV did not. In both cases I ran out of pot room just a tad before I had it in agreement with my Fluke 289 meter that I used for reference. I'm debating if I should just not worry about it. It is such an old meter. Any idea what is the normal reason they don't reach calibration range? I used a 500Hz signal to calibrate but I saw no difference at 100Hz or 1KHz so I don't think the issue is around there. I'm wondering how deep I'll have to go to fix this one. It looks like dBmV doesn't have enough resolution to be useful so I'm not so worried about that. |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
On 8/11/2018 4:28 PM, machineguy59 via Groups.Io wrote:
See this photo album /g/TekScopes/album?id=66462 for my recent repairs on a 2465B. This 2465B had modest corrosion on the A5 board from leaking aluminum electrolytic capacitors. On this board the pads for C2222 and C2520 were partially eaten away and R2013 itself had failed completely (R2013 pads were OK). A few cycles of applying flux, hot air heating, then wash with PCB cleaner and the board was ready for repair. But I wanted a repair that did not suffer the same fate as the OEM assembly.That 30 years might not be so far off. Has anyone on this list ever seen one of these solid Ecaps ever "wear" out? I often replace aluminum electrolytics with the solid SMD parts. I have yet to see one of these fail in service. -Bert |
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Re: Scope
On Sat, 11 Aug 2018 20:31:33 -0700, you wrote:
All the lights ought to come on, then the power up sequence starts. You should hear relays clicking, and you should see different lights on the front panel. If not, then you have a possible power supply problem, or a possible processor problem. There are diagnostic modes that you should be able to use to check out the processor. However, another possibility is that the display has failed. If so, then you can plug in a computer display to the scope and you should be able to see something. I'd do that first, then check power supply voltages, then check the processor, etc. Harvey On Sat, Aug 11, 2018 at 8:27 PM Thomas Dodge <tdodge2404@...> wrote:Hi, |
Bruce Lane
Jon Batters
Ancel