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Re: Concentric A and B time-base knobs/interlocking
Hi Raymond,
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I probably didn't express myself clearly enough. The situation with regard to the horizontal display buttons is this: 1) A is fine and does what it should. 2) MIX shows both time-bases, but the start point is moved about a half of a large division to the left. The position of the changeover point is moved by the "Delay Time Position" multiturn pot as you would expect. 3) A INTEN shows the A time-base, but there is no bright-up indicating where the B (delayed) time-base will run from and to. There is a less-intense portion which can be moved by the "Delay Time Position" control, but it's length isn't controlled by the setting of the B (delayed) time-base knob, only it's position. 4) B DLY'D shows the B (delayed) time-base, but the first part shows a bright vertical line of the same amplitude as the signal at the vertical input. There is also some indication that some of the flyback is visible. I think maybe I had the A Trig Holdoff control at "A ENDS B" before, but for these observations, it is at "NORM". Other controls are: A Trig mode Auto A Coupling AC A Source Norm B Coupling AC B Source Starts after delay. I hope this is a bit clearer. Colin. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Raymond Domp Frank Sent: 14 August 2018 14:59 To: [email protected] Subject: Re: [TekScopes] Concentric A and B time-base knobs/interlocking On Tue, Aug 14, 2018 at 03:39 PM, Colin Herbert wrote: Colin, Not sure if I understand exactly what you mean: The "A" part of the trace (that's the part movable by the delay setting) is supposed to be intensified, not the "B" part. Are you sure "B ends A" isn't set? It's the fully CW position of the Holdoff knob, which is just to the right of the Calibrator loop. If that's not it, ISTR that there's a separate adjustment for the A and B part (one being the normal Intensity setting). Unfortunately, ATM I have no time to look it up in the Service Manual. Raymond |
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Re: Concentric A and B time-base knobs/interlocking
On Tue, Aug 14, 2018 at 03:39 PM, Colin Herbert wrote:
Colin, Not sure if I understand exactly what you mean: The "A" part of the trace (that's the part movable by the delay setting) is supposed to be intensified, not the "B" part. Are you sure "B ends A" isn't set? It's the fully CW position of the Holdoff knob, which is just to the right of the Calibrator loop. If that's not it, ISTR that there's a separate adjustment for the A and B part (one being the normal Intensity setting). Unfortunately, ATM I have no time to look it up in the Service Manual. Raymond |
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Re: Concentric A and B time-base knobs/interlocking
Hi,
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I removed both the Trig & Sweep Logic board and the Timing board. I could then remove the shielding covering the cams and the cam assemblies themselves carefully. I then extracted the appropriate B-time-base cam and actuating rod and applied just enough cyanoacrylate to the broken parts. After leaving this quite a long time to cure (while also actuating the pull-up actuator so that it didn¡¯t gum up, I checked it out and then re-assembled everything. I can now (sort-of) use the delayed time-base as well as the A time-base. The oddity remaining is that while I can use the A time-base, mixed and B delayed, the A intensified by B isn't working properly. The "A" part of the display is given and is brighter than just showing the A time-base on its own, but the supposedly intensified "B" part in too dim to see, even if I turn the intensity up to maximum. I have a Timing board from a parts-donor which I could put in, but I'm not sure whether the Timing board is the source of the bright-up pulse, despite trying to find this out from the manual. Of course, the parts-donor also has a Trig & Sweep Logic board which could be used. However, I don't know if either of these boards is functioning properly..... Colin. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Raymond Domp Frank Sent: 16 July 2018 00:52 To: [email protected] Subject: Re: [TekScopes] Concentric A and B time-base knobs/interlocking Colin, Usually, this is a symptom of the core of the plastic drum for the B-timebase being loose from the shaft that controls it from the front. Often forcing the knob beyond the extreme position breaks the injection molded bond between the aluminium shaft and the drum's core. Also, the plastic of the drum tends to become brittle with time, as I've seen in one case, where the complete assembly had disintegrated. This problem and its solution have been described in this group in the past but I haven't tried looking things up. I have used two methods for repair: 1. The safe way of removing the trigger and time base boards, disassembling the switch assembly and repairing the bond with cyanoacrylate glue. This is quite doable if you pay attention to what you're doing. Note that your 'scope may contain a spring-loaded cam-and-pin to prevent a few extreme combinations of the A- and B-timebase, as noted on the front plate. This part of the assembly is not present on later (?) units and AFAIK only prevents the selection of less-accurate combinations. 2. The adventurous way, as follows (read all steps through so you understand the procedure before doing anything): a. Don't start by opening the 'scope, let alone disassembling anything! Instead: b. Remove the red variable time base button c. Note the length of B-timebase shaft coming out of the 'scope in the pushed-in (no B-timebase) position and pull the B-timebase shaft out of the 'scope. It should come out easily if the problem is as suspected. d. Try pushing the shaft in and out a few times. It should not bend with the surrounding (A-timebase) tube and see if you can get the same length of staff sticking out as noted in c. d. Remove all grease from the shaft e. Cover the shaft with a thin layer of silicon grease but leave about 1 cm at both ends free f. Thinly cover the top end and ribbed tip of the shaft that is supposed to sit inside the drum with a layer of cyanoacrylate gel g. Take a deep breath and push the shaft in as far as it was before (point c). You may want to rehearse this without grease and glue first. h. Wait until the glue has set. If you correctly followed this procedure, with a tiny bit of luck the shaft is now strongly stuck to the drum and *not* to the surrounding A-timebase tube, because the silicon grease prevented that. Obviously, you basically only get one shot at this because if you pull the B-shaft out and push it in again, the glue-covered end will pass through the remaining grease in the outer (A-timebase) tube, killing the effectiveness of the glue. Unless you put an inordinate amount of glue on the end (almost impossible) or did not completely cover the shaft with silicon grease (possible), it'll be easy to pull the B-shaft out again from the A-shaft if the procedure didn't work and you'd still have to follow procedure 1. I have had complete success with both procedures in several cases (3 or 4 with method 2. alone, no retries or going to procedure 1.) and no failures, apart from the case where the plastic drum assembly had almost disintegrated and the switch assembly had to be replaced by a donor unit. Please report back which procedure you followed and its results. Good luck! Raymond |
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Re: 464
On Tue, Aug 14, 2018 at 04:14 AM, Roy Morgan wrote:
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 BiblesThat would be the scan I made about 14 years ago and made available to this group: /g/TekScopes/message/7215 It then has spread to various sites for free download which is OK. But it's annoying is that it often comes up for sale on eBay. The original is off course in Letter format but for some reason my scanner was set to A4 format leaving a white field at the bottom if each page. Since then I have rescanned the whole manual with a better scanner and in the correct format: BTW, it's from 1989 not 1998 /H?kan |
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Re: 464
Roy it is also available on the KO4BB site as a clean PDF file down loaded it myself. they also have a lot of Tek manuals, the weekly pubs and tech notes too.
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Jim O On August 13, 2018 at 7:13 PM Roy Morgan <k1lky68@...> wrote: |
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Re: 464
Roy Morgan
Jon,
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I searched Tek Wiki web site: w140.com/tekwiki/ <> And did not find this manual. Am I looking on the right place? Is there a direct link to it? Or to the page or list of manuals it is found among? Ah I did find it at: That version has 94 pages though the last page is numbered 88. Ah I also did find it on the proxy site manuals page: And the direct link is: Thanks, I can certainly learn a lot from that manual. My 547 seems to be working ok but its 1A1 has incorrect gain in one channel. Roy 547 and 545B Roy Morgan k1lky68@... <mailto:k1lky68@...> On Aug 12, 2018, at 4:37 PM, Jon Batters <jonbatters32@... <mailto:jonbatters32@...>> wrote: |
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Re: Scope
On 2018-08-13 12:37 PM, Roger Evans via Groups.Io wrote:
Tom,For those curious what else is there: --Toby Roger |
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Re: Scope
I think the nearest you'll get to schematics is what H?kan has published <
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>. You'll some schematics for the 644A there, though ISTR there are significant differences to the 684A. On Mon, 13 Aug 2018 at 12:13 Thomas Dodge <tdodge2404@...> wrote:
Thanks for your email. Yes, it is a TDS 684A. I actually got it running |
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Re: Scope
Tom,
This is where I found mine. It is not a service manual in the traditional sense with schematics but it does have some useful information on removing boards and voltage test points. Despite the name it does include the 684A. www.dennlec.com/images/manuals/tek-tds-784a-service-manual.pdf Roger |
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Re: Scope
The clearest you will get is a service manual for TDS544A as I recall. None of the others have ever been released. Many of the sections are the same or similar though so it is still helpful.
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--Eric Sent from my Samsung Galaxy smartphone. -------- Original message --------From: Thomas Dodge <tdodge2404@...> Date: 8/13/18 11:13 AM (GMT-06:00) To: [email protected] Subject: Re: [TekScopes] Scope
Hi Roger, Thanks for your email. Yes, it is a TDS 684A. I actually got it running yesterday, and it is working very well. I think it had been in the surplus place for a long time, and so it took a while for everything to initialize, but it works great. It is in very good condition. Do you know where I can get an original service manual for it? I will take a look inside it and look at the condition inside. Thank you very much. Tom On Mon, Aug 13, 2018, 8:49 AM Roger Evans via Groups.Io <very_fuzzy_logic= [email protected]> wrote: Tom, |
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Re: Scope
Hi Roger,
Thanks for your email. Yes, it is a TDS 684A. I actually got it running yesterday, and it is working very well. I think it had been in the surplus place for a long time, and so it took a while for everything to initialize, but it works great. It is in very good condition. Do you know where I can get an original service manual for it? I will take a look inside it and look at the condition inside. Thank you very much. Tom On Mon, Aug 13, 2018, 8:49 AM Roger Evans via Groups.Io <very_fuzzy_logic= [email protected]> wrote: Tom, |
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Re: Scope
Tom,
Do you mean a TDS 684A? I have one of these and it has serious problems with leaking of the SMD electrolytic capacitors on the acquisition board and subsequent corrosion. There are not too many to change and you can find the service manual which details the procedure for removing the acquisition board. Look very carefully around the other SMD components near the attenuator assembly, this is where I have the most obvious corrosion rather than near the electrolytics. Best to fix these before they cause damage to the PCB tracks and vias. Roger |
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Re: 422 AC power socket
Just use a 30mm cord grip and solder a cable.
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On Mon, Aug 13, 2018, 10:31 AM <johnasolecki@...> wrote:
Picked up a 422 in pretty good shape but it didn't come with the AC power |
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422 AC power socket
Picked up a 422 in pretty good shape but it didn't come with the AC power cord. It needs a round female socket (nema 15-5R) that's about 30 mm or 1.81" in diameter. The smallest I've found online or in the vintage scope restoration aisle of Home Depot is about 35mm or 1.38".
Getting tricky using alligator clips on the pins for power. Does anyone have the correct item for sale or can refer me to a source? Thanks, John (I guess I could convert it to an IEC but I'd really prefer to keep it original) |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
LOL!? LGBTQRC?? ;-)
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Mark On 08/13/2018 04:44 AM, Adrian wrote:
Oh but they are! |
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Re: 2465B Replace Aluminum Electrolytics with Tantalum
Oh but they are!
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I've met several who were so conflicted that they thought they were resistors. Adrian On 8/12/2018 11:17 PM, Mark Wendt wrote:
Huh. Who knew tantalums could be emotionally conflicted. |
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Re: Scope
On Sun, 12 Aug 2018 13:51:55 -0700, you wrote:
Hi Harvey,That it *didn't* come on immediately suggests that there may be a problem that is waiting to happen. It depends on where the potential problem might be, mostly, in such scopes, it goes into two causes: one being a bad power supply, the second being the capacitors going bad. When they do, they leak electrolyte and start to damage the PC board. I'd suggest a search of your scope model to see if others have noted that it's in the suspect years/models for such a problem. I have a TDS540A, and it is a candidate for bad capacitors. Harvey
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Re: Resurrecting a 475 - Request for Guidance
On Sun, 12 Aug 2018 12:17:22 -0700, you wrote:
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.Simple minded approach to dead capacitors (seriously). 1) signs of discoloring, generally turning black or brown. 2) glowing in the dark (not kidding....) 3) excessive smoke 4) very low resistance 5) very low resistance especially with one lead lifted 6) missing body, resulting in two small leads from the pc board (not kidding) 7) signs of mechanical damage 8) leaking of anything, including signs of traumatized solder joints nearby. 9) bulging cans 10) burned resistors or opened inductors in a supply line leading to the part Further tests involve (with power on) low voltages, burning resistors, ticking power supplies (if switchers), excessive current draw. not to make fun of this, but if you go back and look at a lot of the posts about bad capacitors, this is what they'll say. I've seen most of them. Harvey |
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Re: Resurrecting a 475 - Request for Guidance
The 'J4' connector ('J4' is silk screened right next to it) is one of the solid board-to-board connectors; It's shown with 'J4' superimposed over it in figure 7-15 in the 475 manual - on one of the picture diagrams for board A9
I'm struggling to find the designation or reference for the capacitor in the service manual; it's a yellow dipped radial lead capacitor, 2.2uf, 20V. The smoke-emitting resistor measures at 9¦¸? The resistance from the negative lead of C1318 to ground is 0.25¦¸ Regarding the power supply resistance checks, the +50, +5 and -8 rails have appropriate resistances to ground. +110, unregulated +50 and -105/160 are way out, and the values wander around a bit. -15 is at 61K¦¸, and +15 is at 9.75¦¸. I have a feeling that the +15 rail may be shorting through the resistor mentioned earlier; when it and the capacitor I believe to be the culprit are bypassed with a length of wire, the resistance to ground of the +15 rail drops to below 1¦¸. Thanks! |
Raymond Domp Frank
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