Re: Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
Yes, it's clearly been a long time since I've had to work on one of these. I was thinking that pulling the drive dog forward would disengage the drive dogs from the rear drum, but that bothered me, as something in the back of my mind kept saying, "A Sweep in front, B Sweep in back."
So the interlocking is done by the knobs and the drive dogs continue to turn the rear drum even when its shaft is pulled forward.
Thanks, that makes more sense.
For the original poster: If the front knob does not turn the B drum, does it turn the 1/8" B drum's shaft? If it does, but the B shaft does not turn the B drum, then the drive dog has either shattered (most likely) or come loose from the shaft. You'll have to remove that retaining washer from the shaft to get it apart. That can be tricky, or you can destroy the washer and buy a new one at your local hardware store.
Does anyone have a better name for that kind of retaining washer? It looks like an internal star lockwasher, but the inside spikes flare in one direction so that it can be pushed on but can't be easily pulled off. McMaster-Carr calls them Push-On External Retaining Rings.
|
Re: Wanted: Feet for TDS6xx scope..
Hello Lyle.
If you can't locate a replacement set, have you considered 3D printing a set?
J
|
Re: Recommended ventilation clearance around a 2465 scope
Thanks everyone for your valuable feedback.
Thank you for the heat sink suggestion avtek2. Reading through the various threads about "horizontal output IC" cooling, there seems to be an even split between those that advocate installing a heat sink, and those that say the original engineering took "horizontal output IC" cooling into account. The fan in my particular scope was dead, and the prior owner apparently had been successfully using the 2465 that way ... "ouch"! I've replaced the scope with a new fan with the same specs rather than repair the old fan. For cooling, other than the fan replacement, I still haven't quite decided what do do about adding the heat sink.
I've finally finished 3D printing the rear feet for my scope. Luckily someone had already posted a model on Thingiverse, so I only had to tweak the CAD to lift it up a bit more than the original design. I'm also going to 3D print new front feet with a smidgen more height for ventilation per M Yachad's reply above. Hopefully these will give me more than enough clearance on the bottom of the scope.
Thanks again for all the help,
J
|
Hi Pete.
They are not shorted. I have checked all the transistors in the power supply with a dedicated transistor checker. They are fine and within specs.
|
My bad. I wasn¡¯t probing the right places. Instead of checking voltages between chassis ground and directly at both emitters, I probed between ground and + C215/ C218. According to the schematic, this should be the same. But apparently not¡
|
Re: Looking for a replacement Tunnel Diode for a 7B53N
My current understanding is capacitance directly plays in to rise time. Lower capacitance faster the rise time. I would expect this to be fine. But for D180 in a 284 capacitance is a HUGE deal .
Zen
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of n4buq Sent: Friday, December 17, 2021 2:36 PM To: tekscopes < [email protected]> Subject: Re: [TekScopes] Looking for a replacement Tunnel Diode for a 7B53N A follow-on question: How critical is the total capacitance for this TD? Specs state 8pF but the TekWiki page states that as a maximum and I presume less would work. I found a 10mA 2pF and am wondering if that will be suitable. Thanks, Barry - N4BUQ ----- Original Message ----- From: "Barry" <n4buq@...>
To: "tekscopes" <[email protected]>
Sent: Wednesday, December 15, 2021 9:43:43 PM
Subject: Looking for a replacement Tunnel Diode for a 7B53N One of the tunnel diodes in my 7B53N is bad. It is a TEK P/N
152-0140-01 (10mA, 8pF).
Does anyone know where I could get a replacement? I've been looking
at the Russian TDs on eBay and I think some of those might work but am
wondering if other folks have tried those as replacements.
Thanks,
Barry - N4BUQ
|
Re: Looking for a replacement Tunnel Diode for a 7B53N
A follow-on question: How critical is the total capacitance for this TD? Specs state 8pF but the TekWiki page states that as a maximum and I presume less would work. I found a 10mA 2pF and am wondering if that will be suitable.
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "Barry" <n4buq@...>
To: "tekscopes" <[email protected]>
Sent: Wednesday, December 15, 2021 9:43:43 PM
Subject: Looking for a replacement Tunnel Diode for a 7B53N One of the tunnel diodes in my 7B53N is bad. It is a TEK P/N 152-0140-01 (10mA,
8pF).
Does anyone know where I could get a replacement? I've been looking at the
Russian TDs on eBay and I think some of those might work but am wondering if
other folks have tried those as replacements.
Thanks,
Barry - N4BUQ
|
Also some of the supplies in this unit are unregulated. Check the
transformer for correct line voltage. The line voltage have moved up I the
world sence these were built it is normal for some of the supplies to be
elevated here in the US these were made for 115vac. And they are now seeing
125 vac at the line. This will elevate some of the supplies. It might be
fine.
Eric
toggle quoted message
Show quoted text
On Fri, Dec 17, 2021, 2:17 PM saipan59 (Pete) <saipan1959@...> wrote: Hi Stephen,
My first thought is that the series regulators on +/-10 are not regulating.
Most obvious issue would be Q213 and Q217 are shorted, and/or D213 and
D216 are open.
Check the 27VAC at the transformer, and verify that you see about 14VAC
between each side and Ground.
Given all the problems you already found and fixed, perhaps the unit was
exposed to a "catastrophic" event, such as being powered by 230V when the
switch was set to 115V.
Pete
|
Hi Stephen,
My first thought is that the series regulators on +/-10 are not regulating.
Most obvious issue would be Q213 and Q217 are shorted, and/or D213 and D216 are open.
Check the 27VAC at the transformer, and verify that you see about 14VAC between each side and Ground.
Given all the problems you already found and fixed, perhaps the unit was exposed to a "catastrophic" event, such as being powered by 230V when the switch was set to 115V.
Pete
|
On Fri, Dec 17, 2021 at 07:56 PM, Stephen wrote:
However, 1 is referenced to chassis ground, and it should be + and - 10V +/-
1.5V, but I read very high at +16.73V and -16.59V.
The manual tells you to check the voltages, but not how to correct them when
they¡¯re not within specs.
Can anyone help? Thanks.
That's a very simple circuit with two main causes for your problem, although a bit surprising the two separate supplies are both bad: 1. D213 and D216 open. Check if they carry +10V and -10V aginst GND. 2. Q213 and Q217 shorted between C and E or open B. Depending on how the instrument is constructed (I don't have one), some connections could be open. Should be easy to check with your DMM. The voltages are shown in the Manual. Raymond
|
Hi all,
I finally found the time to repair the Type 106 I bought back almost a year ago¡
A few months ago I had offline help from 2 very nice people here.
That thing had shorts everywhere. A few blown transistors, 3 out of 5 shorted bridge rectifiers, burned resistors, shorted and opened diodes, the whole shebang¡. In other words, it drove me crazy¡
It¡¯s now finally back from the dead, and working quite well, except for a few voltage issues.
3 voltages are referenced to what they call the ¡°A SUPPLY¡±: +150 +/- 15V, -150V +/- 15V, -20V +/- 2V.
All check within specs at +153.7, -150.72, and although the -20V reads a bit low at 18.73V, it¡¯s still ok.
However, 1 is referenced to chassis ground, and it should be + and - 10V +/- 1.5V, but I read very high at +16.73V and -16.59V.
The manual tells you to check the voltages, but not how to correct them when they¡¯re not within specs.
Can anyone help? Thanks.
|
Re: OT: microwave oven blows fuse
Thanks, Dave (and all the others who have given recommendations).? I poked around a bit, and all the door switches operate properly, the relays are all open circuited as shown on the wiring diagram, and nothing seems amiss.? The only thing that's weird is a bit of rust in one corner on the screws holding the main cover and the cover over the convection fan, like water was sitting on there for a while.? Last night I put in a cheapie glass fuse and turned it on, expecting it to blow right away.? Nope, and it even heated up a mug of water.? Of course then I stripped a sheet metal screw hole, the one right under the magnetron!? Any other screw hole I would have left alone.? So I found a nut that would fit and epoxied it in place.? Tonight I will put it all back together and hope there was just a temporary short somewhere that was blowing fuses.? ?Otherwise it's back to the drawing board.....? ? ? ? ?JimSent from my Verizon, Samsung Galaxy smartphone
toggle quoted message
Show quoted text
-------- Original message --------From: ebayatessnh <ebay@...> Date: 12/17/21 6:30 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] OT: microwave oven blows fuse Hi Jim,My microwave stopped working. I don't recall if it finally blew the fuse, but it was arcing behind the control panel. Being an electrical engineering, I investigated the circuit as you and other have suggested. Nothing seemed to be amiss.It turned out that the little microwave transparent window in the back upper right of the unit had food splashed on it. The dirty window was not allowing the microwave energy to get into the enclosure. As a result the energy found another path and caused the arcing.A $4 replacement window from Amazon solved the problem.DavePS, my wife wanted to just throw it out and buy a new one, but like many here, the reward of fixing something outweighs the financial consideration of the time spent on the repair.
|
Re: OT seeking a special resistor
On Tue, Dec 14, 2021 at 09:42 AM, ken chalfant wrote: Does anyone have an RPC HP-6 or BP-6 600Meg resistor, possibly rescued from a
Pomona 2900A high voltage probe, that you are willing to sell? I'm guessing that this is what we used to call a "zebra stripe" HV resistor. To find a replacement, we'd need diameter, length, and the threading in the end, and, of course, the resistance, 600 MOhms. The common specs are 3/8" diameter, length? and #6-32 threads. These tend to be hard to produce in tight tolerances, so when close tolerance is needed they are usually made by screwing together two selected resistors with half the length and ~half the resistance, one plus, one minus. When finished, the pair would be wrapped in transparent heat shrink and marked with the total resistance. The transparent heat shrink also protects the carbon stripe that is the resistance element, as that stripe is quite fragile. Sometimes, however, the transparent cover is a liability in extreme HV conditions, so it is omitted or stripped off. You can find these zebra stripe HV resistors both bare and covered. Once bare, however, they often get chips in the resistive stripe if they are not handled with great care, as when stored side by side in a drawer. I've never done this, but I've been told that one could make one's own high value, HV resistors, by painting on a ceramic rod with India ink. I suggest that you examine your resistor carefully for any chips/interruptions in the stripe. If your resistor is one of the bare ones, and you find a problem in the continuity somewhere, you might be able to bridge the gap with a tiny dot of India Ink. If this HV probe is the style with the built in meter, you should also consider the possibility that the resistor is good but the meter has failed in some way. There could also be problems with the connections somewhere. Make sure you're barking up the right tree.
|
Check 32V Unregulated supply in particular. Check Fuses F736, F746 and F768. A slip of the probe can open one or more of these. 32V unregulated is most likely dead and this will kill the HV section. These fuses are "conveniently" located at the rear of the A1 board and are not east to reach or replace.
--
Michael Lynch
Dardanelle, AR
|
I have not checked the 455 diagram. If it is similar to the 465M, I would start checking the voltages first. Assume you have checked all the fuse. Where exactly did you slip the probe?
|
Re: Tek 577 restoration -- help needed
This is a copy of table 5-1
TABLE 5-1
VERTICAL CURRENT/ DIV STEP/ OFFSET AMPL Resistor (1/4%) C-B Difference in DVM Reading B-E Within ¡À3%, ¡À1 nA
2 nA . 1 V 10MOhm 0.3200 V 0.0296 V
5 nA . 2 V 0.8000 V 0.0400 V
10 nA .5 V 0.8800 V 0.0375 V
20 nA 1 V 1.760 V 0.0638 V
50 nA 2 V 4.400 V 0.1430 V
|
Re: Tek 577 restoration -- help needed
Rogerio,
I will send you some resources off list.
Zen
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Rogerio O Sent: Friday, December 17, 2021 8:41 AM To: [email protected]Subject: Re: [TekScopes] Tek 577 restoration -- help needed Dear all, I found the instructions of step 3 of 177 calibration very confusing. my doubts, up to this moment are: 1- in step 3e I should note the DMM reading, but I change the spot position to the 8th division only in step 3f. 2- What does the 4th column in table 5-1 mean by "within +-3%,+- 1nA" I can't start the calibration procedure until I figure out this. Please help!!!
|
Re: Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
On Fri, Dec 17, 2021 at 03:06 PM, n4buq wrote:
I'm reasonably sure that the forward drum is the primary sweep control and the
rear is the delayed sweep control in this plugin.
The inside shaft reaches through the hollow haft to the rear drum and is controlled by the front grey knob; the B sweep. The outer, hollow shaft, only reaches to the front drum and is controlled by the clear plastic disk with protrusion which sits behind the gray knob; the A sweep. There is no other way this could be arranged. Raymond
|
Re: OT: microwave oven blows fuse
Hi Jim,
My microwave stopped working. I don't recall if it finally blew the fuse, but it was arcing behind the control panel. Being an electrical engineering, I investigated the circuit as you and other have suggested. Nothing seemed to be amiss.
It turned out that the little microwave transparent window in the back upper right of the unit had food splashed on it. The dirty window was not allowing the microwave energy to get into the enclosure. As a result the energy found another path and caused the arcing.
A $4 replacement window from Amazon solved the problem.
Dave
PS, my wife wanted to just throw it out and buy a new one, but like many here, the reward of fixing something outweighs the financial consideration of the time spent on the repair.
|
Re: Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
Hi Jim,
I'm reasonably sure that the forward drum is the primary sweep control and the rear is the delayed sweep control in this plugin.
I may need to open my 465B and compare the rear drum. From what I can tell, there's not much way to get the shaft and the disc that's holding it in place out of rear hole without some modifications. The disk has either a retaining/grip ring or is crimped onto the shaft. Either way, if I get the disc off of the shaft, the shaft will probably come out the front end of the drum but I'm pretty sure the disc will not come out of the rear hole (and, certainly, not the smaller front hole).
I'll keep looking at possibilities but it's not looking real good at this point.
Thanks again,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "Jim Adney" <jadney@...>
To: "tekscopes" <[email protected]>
Sent: Thursday, December 16, 2021 5:59:00 PM
Subject: Re: [TekScopes] Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam On Mon, Dec 13, 2021 at 09:55 AM, n4buq wrote:
If I pull on the hollow shaft, there's definitely spring tension as it should
be, but
when I rotate it with it pulled forward, all I can feel is it
grinding/catching against something in the forward part of the drum. I presume
that's the broken dog (or what's left of it) grinding against whatever the dog
used to latch into. It's been a couple decades since I worked on one of these. Thinking about it, I
suspect that the drive dogs should drive that drum in normal operation, but
when the shaft is pulled the dog disengages and lets that drum stay in place
while the front drum still rotates. If that's the case, the rear drum controls
the main sweep while the front drum controls the faster sweep.
The drive dog body is a cylinder about 1/4" in diameter, with two ~1/8"
protrusions, 180 apart, that stick out from the main body. The hole in one drum
end plate is 1/8" to clear the bare shaft; the other end plate has a 1/4" hole
with two protrusions to clear the dogs. To assemble, slide the spring on the
shaft, then the drum on the shaft. The drive dog body slips in the larger hole,
the spring is compressed, and then that little retaining washer slides on the
other end, so the dog body can't come back out. The position and orientation of
everything is important.
If you have everything apart, the shaft may not want to come out the small hole
end because of the knurling on the shaft. In that case, carefully work the
retaining washer off the shaft so everything can slide out the other end.
At that point, you should be able to see exactly what you are up against.
I MAY still have one of the brass replacement dog bodies.
|
saipan59 (Pete)
Raymond Domp Frank
Michael W. Lynch