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Extender cards for 2753P
All,
I think I made a mistake when I sent this already. Sorry if it gets double posted. I am sorry if this has been asked before but my 2753P has a problem when I try and set the SPAN/DIV below 500KHz. It say s "1st low failure" I tried to fix it based on google but no luck. I need the extender cards. Anybody know where I can get one ? Thanks in advance. I think any 495x series instrument will also suffice as well as 2755x. 73, N2FGX George |
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Re: Fixing up a 5S14N (for search: 7S14)
tl;dr: ch1 at least 'ok'; ch2 cr2 on order
Welp, as said to begin with I hadn't done all my homework before posting some early results. On Sun, Dec 12, 2021 at 09:35 PM, Don Bitters wrote: . . . What happens when you switchThe various peculiarities of both channels follow the sampler boards. On Mon, Dec 13, 2021 at 08:36 AM, Jim Adney wrote: Dead cells would leave their two terminals effectively shorted, while removedRight. Don't know what I (wasn't) thinking. And yes, it makes a difference because... On Tue, Dec 14, 2021 at 01:48 AM, Roger Evans wrote: If you look at the 7S14 schematic <1> Samplers and Compensation, it shows thatOh. And it couldn't be any more clear in the schematic. I looked right at that and didn't see it. Maybe because my brain simply vetoed the possibility. It's really counter-intuitive to me that batteries pass signal with >1GHz bandwidth. I can't say why I think they wouldn't -- it just seems like if someone had asked me out of the blue if chemistry belongs in a GHz signal path it would have been easy to answer 'no' and believe myself. And there's no 'a-ha moment' yet -- I've had a little think about it and it's still skew in my head. But there it is and it works. Thank you both for kicking me in the right direction. So, given that the cells pass GHz signal, I've since spent some time staring at the schematic, and at the board, and re-reading that bit of the manual and about avalanche transistors, and back to the schematic, and the board, .... etc. ..., and maybe I have the strobe generator/sampling gate/preamplifier about halfway figured out. I suppose that's why I was fascinated to get one of these and all the more to have one in hand: pretty much everything about it makes my head hurt. Anyhow... On Tue, Dec 14, 2021 at 01:48 AM, Roger Evans wrote: With the age of these units it is also possible that the 2k resistors R1, R2R1 & R2 measure 2.15 & 2.17 k¦¸. In circuit but at least one end looks isolated by caps so I _think_ that's a fair read. For now I'll assume that's not enough difference to overwhelm the offset control. (on the healthier sampler they measure 2.10 & 2.10) However both sides of the CR1 diode package measured hundreds of k¦¸ both ways, which sounds unlike diodes. I've just ordered some of the HSMS-8202 diodes pairs mentioned in other threads here. They're out of production and out of stock among reputable sellers but google found some for low-risk money and estimated delivery about when I expect to get another swing at this next year. ...So that's the more broken sampler, which was ch1. I've kept that one out for more surgery later. I put the better working sampler from ch2 in ch1 to make at least a single channel unit for now. The short story of that is that working through the LF compensation, loop gain, DC balance & memory balance has it working fairly well. At least as far as I can tell with a 5kHz-200MHz square wave source (Adafruit Si5351A module). I'd like to go back for another round of comparing between the sampler and normal Yt operation, which seems like a meaningful comparison up to about 10MHz with the 50/60MHz 5441 scope. The sampler is obviously faster, but within limits of the slower scope they don't always agree. I'll have to check again since getting it better dialed in, but one strange thing that persisted was for the longest square wave periods, ~100-200¦Ìs, the sampler showed a small step-up in the last ~10¦Ìs of the high state while the normal Yt display showed very flat tops. That seems impossible... how does the sampler know that an effectively steady-state signal is going to transition in 10¦Ìs? Some of what had seemed strange may have been the intermittent self-oscillation syncing up with signals around 5MHz. The odd two-level "noise" persisted on either channel with the 'bad' sampler. No idea what that could be - but first the diodes. Until next year- Merry Christmas, Blessed New Year, and all the best of whatever else you celebrate around this part of the year. |
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Re: Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
Removing the retaining washer would not have allowed a fix. It was necessary to remove the front hub from the drum to get to those parts and repair them. I can only presume the drive mechanism in this drum is different from the one(s) you worked on.
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Thanks, Barry - N4BUQ ----- Original Message -----
From: "Jim Adney" <jadney@...> On Sat, Dec 18, 2021 at 08:37 PM, n4buq wrote:/g/TekScopes/album?id=270912I don't see anything in your photos that resembles the drive dog that I'm |
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Re: Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
On Sat, Dec 18, 2021 at 08:37 PM, n4buq wrote:
/g/TekScopes/album?id=270912I don't see anything in your photos that resembles the drive dog that I'm familiar with. In my opinion, you would have been MUCH better off simply removing the retaining washer and not damaging the drum. Now you have 2 things to fix. |
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Re: Type 106
Status Update
All 10R and 33R resistors replaced on the tube sockets. Unit pretty much calibrated except for the ¡°sampling scope¡± part. I don¡¯t have one (yet) Due to the nature of the adjustment pots, frequency accuracy is kind of hard to get, but it¡¯s close enough. I don¡¯t think that really matters that much. I get 100.05 KHz, and 1.09 Mhz. I believe that¡¯s fine. Unless pots are changed to multi-turns, it¡¯s almost impossible to get better. But again, I don¡¯t think that really matters. Unit has been sound and stable for a couple of hours outside it¡¯s enclosure, and about the same amount of time inside it. I¡¯ve dedicated so much time and effort, on and off, that I¡¯d like to think I¡¯m finally out of the woods. Thank you all again for your time and patience. PS: Next in line will be my 067-0502-01. Just a minor issue though. |
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Re: 2247A problems (no power on)
A cricket here, chirping in. Sorry to hear of the mechanical difficulties. I too remember being completely perplexed the first time I attempted to mechanically take apart a 2247A.
Do you have the service manual? Isn't there a processor routine that runs on start-up? Like a pre-flight checklist, where if all conditions aren't met, the machine shuts itself down? And weren't there various firmware revisions for this product, where this start-up check routine could have been modified? I'd guess that it certainly polls the MBU state. Could you have a dead battery? |
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Re: OT: microwave oven blows fuse
One troubleshooting Aid that I made up when working on microwaves & then used for general troubleshooting was an electrical box with a circuit breaker in it.
It was made to "industrial" heavy duty standards from a solid mounting block with blank switch plate on top with a lead coming out one end using a plastic grommet - the type that tightens onto a lead so it can't be pulled out. The circuit breaker was fitted in circuit instead of the fuse when testing to save blowing fuses. I later made up some leads from blown fuses so the "fuse lead" could just be clipped in. I later retrofitted them with insulated banana sockets & insulated banana plugs on the fuse box. Another handy device I use now is the Wago 221 series Compact Lever Connector or Lever Nuts. You just lift the lever, slide the stripped wire in & put the lever down. They will firmly hold a wide range of wire sizes even down to a small single strand. Using the 221's normally gives me no excuse to use the old "fool killer" leads on anything with a wire lead or that I can tack a wire lead on. I did retrofit my old "fool killers" with insulated banana plugs & totally insulated alligator / crocodile clips that can just be swapped over. Regards, Brian. |
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Re: 2247A problems (no power on)
Well still went ahead and fully recapped the power supply but still no change. And in the process managed to break the power switch link rod. How was I supposed to unlink it to get it out of the way I don't know as the access to the point at the corner where it couples into the shaft that comes out at the front panel is completely covered up by the chassis and the bottom main board which I don't think would be a good idea to remove just to do this. It would have been nice if someone could have explained the procedure to remove the power switch lever, but so far this thread seems like cricket sounds.
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Re: Type 106
On Sun, Dec 19, 2021 at 02:26 AM, n4buq wrote:
Thanks Barry. While I¡¯m at it, I¡¯m gonna check the values of all the resistors in there. After all this thing¡¯s been through, that probably won¡¯t hurt¡. |
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Re: Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
I was kind of surprised that this came apart as easily as it did. I began to realize that the hub appeared to have a slightly different color than the drum and that started me down the road of using the razor knife. I should've realized that long ago but kept thinking that end of the drum was one molded piece so kept looking elsewhere.
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Thanks again, Barry - N4BUQ ----- Original Message -----
From: "Raymond Domp Frank" <hewpatek@...> On Sun, Dec 19, 2021 at 03:37 AM, n4buq wrote:That looks quite promising, Barry! |
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Re: Type 106
Glad to see you found the problem. Odd that it needed a resolder but I suppose that happens.
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I need to take the time to check things more thoroughly but I have other projects that I need to sew up before getting back to that one. Thanks, Barry - N4BUQ ----- Original Message -----
From: "Stephen" <stephen.nabet@...> First of all, I¡¯d like to thank you for all your great ideas and suggestions: |
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Re: Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
On Sun, Dec 19, 2021 at 03:37 AM, n4buq wrote:
That looks quite promising, Barry! No it is not what I meant with the "glue method". The glue method is meant to repair a situation where a plastic part that normally is fixed on a corrugated shaft inside the drum assembly has broken loose, allowing complete extraction of the shaft through the front. The repair is done by carefully greasing most of the shaft, leaving just the part that is to be glued open and putting some cyanoacrylate glue on that part. Next, the shaft is pushed in through the tube (outer shaft) into the plastic part. Surprisingly(!), this has worked for quite a lot of people. I remember at least three successful operations and no failures (like glueing everything together... Raymond |
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Re: Type 106
First of all, I¡¯d like to thank you for all your great ideas and suggestions: Mark, Barry, Tom, Pete, Eric, Raymond, and all those that I probably unintentionally forgot to mention.
I went back to the last thing I did ¡°before¡± I lost the output. And that was changing D232. I reflowed the solder joints, but still nothing. Then, before I used a power supply to substitute for the PT, I decided recheck all the voltages coming out of the secondary, and the those after all the rectifiers on the + and - sides (disconnected from the circuit). Everything was as they should, albeit a bit high due the the line voltage I guess. Although the PT primary is rated at 230V, and the manual even calls for testing up to 250V and some change. I then cleaned and resoldered D232, and bingo, traces are back up again. While checking the tube voltages, I realized that most of the 10 and 33 ohm resistors where way out of tolerance. One is is even at 45ohm instead of 33. All of them will be changed, probably today. I¡¯m gonna let the unit run for a couple of hours on the bench, and pray for nothing else to give (again!!) PS: Sorry if I don¡¯t always answer right away, but being in a different time zone than most of you guys, Europe (Paris), and sometimes quite busy with family, I¡¯m doing my best. |
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Re: Type 106
Stephen,
The low value electrolytics in the supply and signal circuits are likely bad. Ones made in the late 60's to early 70's that are axial with a clear jacket, usually Sprague, are commonly bad by open or short. The jackets on these will be thicker and can have a yellow tint due to age and usually sticky to the touch. These type will commonly suddenly fail. I have seen this in years past. The photos on the W140 site look like these ones with the thicker jacket. The low values can be replaced with film types. The low value ones likely have high ESR. C10 and C20 can be replaced with a film of 5mfd 250V or higher. the 4mfd types can be 4,7mfd 50 to 250/400V. Using a 400V type instead of 250V works fine. Film to replace electrolytics can improve things. No polarity, "0" ohms ESR and long lives. If C249 is bad, you will not get high amplitude fast rise R246. Adding more capacitance across the 9-10V supplies might help. With the bridge rectifiers shorting, the main filters are the culprit. At the age of the piece, restuffing them would be a good idea, e.g. Nichicon LGR, ULD, UHE, UCY. Replacing axials with radial can be done. I have done this many times. For restuffing cans, radials are used. Using a 16-30 ohm NTC in the primary will lower surge current and drop the voltage a bit since your mains voltage is a bit high. The mention of bad solder joints is also something to check. Oil the fan. I hope this can help you. The other posts I read before replying. The diodes may need replacing as some said. David W's way sounds great. Mark |
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Re: OT: microwave oven blows fuse
Hi all,
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As mentioned by Dave, fixing something is better then tossing and buying again. It's also good practice for us problem solvers! On the issue of broken interlocks the wife here used to slam the microwave door all the time, at the time, parts were getable locally,so I did. Since then slamming is banned here! lol! At the cottage the very nice microwave would start and die. Turns out the LSI IC on the PCB had tin flashed pins tarnished to black,after cleaning and cycling in the socket a few times, it's back to normal! Most fixes can be simple if we can recognize it! Merry and safe Christmas to all! Pete On Saturday, December 18, 2021, 04:34:18 p.m. GMT-5, Jim Ford <james.ford@...> wrote:
Thanks, Ben.? I will see what I can do to get the interlock assembly.? Merry Christmas and Happy New Year to you and yours!? ? ?Jim?Sent from my Verizon, Samsung Galaxy smartphone -------- Original message --------From: "benwetzel via groups.io" <benwetzel@...> Date: 12/18/21? 7:45 AM? (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] OT: microwave oven blows fuse You will need to replace the plastic bracket that holds all of the switches.? Or easier approach is to get the whole interlock assembly. Good luck sir.Ben |
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Re: Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
I figured out how to get to the broken parts and here are some pictures:
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/g/TekScopes/album?id=270912 It turns out that the front part of the drum cam was indeed glued to the drum body. I took a razor knife and worked it around that seam and the front hub popped right off. As you can see, the two sections inside that comprise the drive dogs and the hub were broken. I suspect a hard hit to the shaft with the gray knob removed but can't say for sure. Jim - I presume these are the "dogs" you referred to? Raymond - was this the part to which you were referring when you mentioned the "glue method"? In any case, a bit if glue and this should be back together and working once again. If the tunnel diode I ordered works (I should get it in a few days), I may have a fully-functioning 7B53N. Thanks, Barry - N4BUQ ----- Original Message -----
From: "Raymond Domp Frank" <hewpatek@...> On Fri, Dec 17, 2021 at 10:44 PM, Jim Adney wrote:This all looks very much like a rather frequent problem with 465- and |
Raymond Domp Frank
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