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I have some but they are the ones that come out in the 90 degree rubber boot.

Jim

Anyone know where a replacement power cord can be obtained that matches the original for a 400-series scope (for U.S. power outlets)? Someone cut the ground pin off of my 465B and I'd like to replace it with a cord like the original (the kind that has the "keeper" clip). Mine is the style that comes out of a plain strain relief (not the larger rubber boot like I've seen on some 465B models).

Thanks,
Barry - N4BUQ

Sorry on behalf of the group for the "helpless" comment. That was uncalled-for when you don't know who's at the other end of the conversation, or what their abilities/handicaps might be.

That being said... I'm surprised that the problem isn't your DIP switch. Those are very common failure items on these units. If you haven't gone back and double/triple-checked that switch, I'd definitely do so before going any further. Unlike the IC, I do believe it's a good idea to reflexively replace those DIP switches whenever you're working on the boards that include them. Same with the one on the back, if you think you will ever want to use the GPIB port for anything. Although Sergey's tip about cutting the leads on the IC won't be as effective for removing the DIP switches, it's still a valid strategy if you crush the plastic body with pliers and pull it off first. A Dremel tool is also a good way to go.

Working without extenders, it's sometimes helpful to tack-solder a few 'probe wires' onto various device pins to bring the signals out for monitoring. The extenders are nice to have -- and almost mandatory for some procedures -- but unfortunately they're not always available.

-- john, KE5FX

Hi Jim,

Thanks for the kind remarks. Unfortunately, I don't think there's any room for another snap-in cap on that board.

Here's the list I used. I'm pasting this in with tabs but I have a feeling those will be replaced with spaces so the columns may not align with their headers.

Note that there are two entries for C4429. I chose the taller one (45mm) as its tolerance kept it in the range of the original.

Mouser P/N Capacitance Voltage Diameter Length Temp
C4419 5000uF 25V 647-LGU1V682MELZ 6800uF 35V 22mm 40mm 105C
C4429 1200uF 100V 647-LGU2A122MELZ 1200uF 100V 22mm 40mm 105C
C4429 1200uF 100V 647-LGU2A152MELZ 1500uF 100V 22mm 45mm 105C 5mm taller but higher capacitance that will meet original tolerance
C4439 550uF 100V 647-LGU2C681MELZ 680uF 160V 22mm 40mm 105C
C4521 5500uF 30V 647-LGU1V682MELZ 6800uF 35V 22mm 40mm 105C
C4531 5000uF 25V 647-LGU1V682MELZ 6800uF 35V 22mm 40mm 105C


As you can see, I used 6800uF, 35V for a 5500uF, 30V cap.

I was thinking around $8 shipped in the U.S. for just the board. I'd have to look into the rest of the hardware. I could also supply the caps if there's enough interest. I ordered the #8-32 x 1.5" aluminum standoffs from Mouser as well. Also, I used stainless screws and stainless internal-toothed lock washers on both sides of both boards.

Note the solder lug that's sitting on top of one of the standoffs. I actually made a mistake on the board design. Without looking closely at the schematic, I thought the -8V supply's positive side was grounded but that's not the case (that's the side that's regulated to maintain -8V) and, thus, if you look closely, you can see where I had to remove part of a trace. I hose to run the positive lead soldered to the main board and then directly up against the pad on the small board. I could have done that a bit neater but that would have depended on the post and screws being part of the circuit and I didn't care for that as much. If I make another set of boards there will be solder pads for both sides of the cap for the -8V supply. I plan to also make a cutout to clear the thermal switch which will make it possible to use much shorter standoffs which might look neater.


Thanks,
Barry - N4BUQ

I was moving things around today, and happened to turn the tuning knob on my 190A, and the frequency display didn't rotate.? Turns out the rubber donut was cracked/broken in five places (but still soft!) and had fallen off.? This must be a common failure- is a there a simple, common replacement? If not, I'll have to drag out my box of o-ring and bushing catalogs.
-Dave

I hate to disagree with Jose, but there have been a fair number of papers
on constructing NLTLs --- some even using discrete diodes.
If you'd like to read a review of the patents, may I refer you to this
short paper? I know the author personally.

Patents and Microwave Measurements-Nonlinear Transmission Lines [TCC
Tidbits] <>
<>IEEE Microwave Magazine
<>


Year: 2016, Volume: 17, Issue: 7
<>
Pages: 78 - 81

On Tue, Jul 24, 2018 at 1:00 PM, Craig Sawyers <
c.sawyers@...> wrote:

FWIW non-linear optical methods are used to compress the length of laser
light pulses. Somewhat
analogous to NLTL's, but at 10^14Hz.



Craig

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Ed

Breya via Groups.Io

Sent: 24 July 2018 17:32
To: [email protected]
Subject: Re: [TekScopes] Homemade tunnel diodes

Jose said:
"Not many people seem to have made DIY NLTL, let alone samplers based on

it."

This is probably true, because NLTLs usually have lots of stages, so can

get very big and

complicated
before you get remarkable compression. For simplicity and effectiveness,

a single SRD/varactor of

the
right type, in the right circuit environment, is pretty hard to beat for

straight up impulse

generation or
frequency multiplication. A whole bunch of them cascaded can form a

NLTL, with its edge-

enhancement and wide BW. As always, it depends on the particulars of the

application.

I don't think there's a need for a "modern" replacement for the

SRD/varactor. It's a common RF

part -
not at all an obsolete technology. Nowadays there are alternatives for

many applications, by using

fast
active devices capable of appropriate edge speeds.

Ed

On Tue, 24 Jul 2018 15:00:00 -0700, you wrote:

Here is a pondering question for you all to think on. How many of you have considered replacing (upgrade) the ceramic disc caps to a higher class 2 grade like X5R or X7R to replace all the Z5U ones used as they are the worst of the class 2 and as they deteriorate with age plus are susceptible to temp and frequency changes to capacitance so they might be responsible for the little niggling problems with the scopes over time or after repairs but it is just not right?

I haven't seen a problem where I can pin it down to one of them
failing. I'm probably not as critical as others might be, though.

Harvey

I tend to use x5R and X7R for new designs, though.

After all they are old and older technology and in most cases much used. Just a thought to consider.

Jim

Yes, they are.? And, yes, they suck!


Sent from my Verizon, Samsung Galaxy smartphone

I don't think that Z5U types are still being manufactured; I know surface mount types were phased out years ago.? Maybe really cheap disk types are still being made.??
-Dave

From: Jim Olson <v_12eng@...>
To: [email protected]
Sent: Tuesday, July 24, 2018 3:04 PM
Subject: Re: [TekScopes] ceramic capacitors

Forgot to add that the higher class 2 have much less change to capacitance +-15% vs +20%-85% so should make the scope more stable.

Jim

Really neat practical fix very tidy I am doing a 466 which uses six caps so how would that board work there would have to mount one closest to the transformer to the main board?
What are you asking for the board and hardware I am in the US in CA.
Where did you get the new electrolytics from having a hard time finding the correct ratings for the 466 the 5500uf 30v are scarce.

Jim

Now sorry I posted here after the responses received so far. I didn't ask for advice on how to repair the board, or comments on my helplessness, but rather, a pointer to someone (knowledgeable) who could troubleshoot and repair, or supply a replacement board.

I have 60+ year background in electronics, mostly telecom and computing, along with three degrees in electrical engineering. I have no doubt I could remove the IC in question, and have done so on other equipment where I have significant hands on experience. However, the board in question is a very densely packed multilayer board with a mix of surface mount, radial lead, DIP and other devices. In examining the circuit diagram, there are many potential causes for the problem I am seeing other than the tri-state buffer, including the possibility of damaged traces due to leaking electrolytics. I would surmise from examining the circuit diagram that the buffer IC may be the least likely cause of the problem. I am seeing this possibly irreplaceable board for the first time ever and feel it prudent to find someone experienced at diagnosing and repairing Tek 49x series SAs rather than just diving in and "yanking out" parts without good cause. Without this board the SA is junk, and there is no point in possibly making the situation worse. A little finesse and relevant experience go a long way, and someone who has done this before will find and fix the problem sooner than someone who hasn't. Compounding the problem is the dense packing of boards inside the SA. Getting a probe on various test points is practically impossible without soldering a lead to the board to bring the signal out (unless one has an extender board).

So, thanks for taking time to post. Happy to receive your suggestions for a repair facility or replacement board.

Recently, I had a problem with the LV supplies in my 465B. Thinking it was a shorted electrolytic can, I decided to replace all of them (although it turned out to be a shorted tantalum but had already pulled the cans before finding the real problem).

I decided to design a small PC board on which to mount modern snap-in caps. THe board mounts with standoffs in the exising larger holes that are left when the cans are removed and allow replacement of the snap-ins if/when they fail and that can be done without further soldering on the original board.

Pictures of the board and the process are in the following album:

/g/TekScopes/album?id=64929

If anyone is interested, I have extra boards for sale.

Thanks,
Barry - N4BUQ

And yet the scope is stable enough already.

There is an old saying: "If it ain't broke, don't
fix it."

-Chuck Harris

Jim Olson wrote:

Forgot to add that the higher class 2 have much less change to capacitance +-15% vs +20%-85% so should make the scope more stable.

Jim

Here is a pondering question for you all to think on. How many of you have considered replacing (upgrade) the ceramic disc caps to a higher class 2 grade like X5R or X7R to replace all the Z5U ones used as they are the worst of the class 2 and as they deteriorate with age plus are susceptible to temp and frequency changes to capacitance so they might be responsible for the little niggling problems with the scopes over time or after repairs but it is just not right?

After all they are old and older technology and in most cases much used. Just a thought to consider.

Jim

On Tue, Jul 24, 2018 at 01:02 PM, Bert Haskins wrote:

Be careful about using a fet with a higher voltage rating, as the voltage
rating goes up, so does the the gate capacitance

Yes forgot to tell him to check for that too... but in my defense it was implied in my generic "meets or exceeds specs" general statement ^^

Of course in case of gate capacitance, "exceeds" means lower not higher... just in case ! ^^

Luckily he would probably have been fine anyway, unless going wild on over rating the voltage.


Vince

On 7/24/2018 12:27 PM, satbeginner wrote:

Hi all,

a cheap and broken 2215A found it's way to my home :-), so now I am in the process of getting it repaired.

I used this document from H?kan that helped me a lot:

The fuse would blow instantly, so I separated the main PS from the rest by removing Q9070.
An inspection by the eye learned that there were several low voltage elco's leaking,
C960/C962 (+8,6V) were leaking;
C961/C963 (-8,6V) were leaking;
C968/C970 (+5,2V) were bad;
C956 (+30V) was leaking;

Fortunately no real damage to the PCB.

Also the Q9070 and CR907 were toast.
According to the document the FET is a IRF730 (400V 5,5A 0,75Ohm 12ns) and the diode a BYD73G (400V 1A 50ns)

I replaced all the capacitors first, and now the scope has trace(s) when applying 43VDC to TP940 (Pos) and TP950 (neg).

Being the optimist, I replaced Q9070 with a FQPF4N90C (900V 4A 3,5Ohm 50ns) and CR907 with a PR1507 (1000V 1,5A 300ns) I harvested from a switching PS,
but.... They last about 2 seconds...

Based on H?kan's document I applied a test voltage to C925, and the signals at the chip U930 check out, and since I tested all surrounding components Q908, CR908, R909, CR920, I come to think it must be the speed of the Q9070 and CR907 that causes the sudden death of these replacement components.

My question is: does anybody (recently) repaired a 2215A LVPS and replaced these 2 comonents?
If so, what replacements were used ?

The documents suggest a MTP6N55 for the FET and a BYD73G for the diode, but I would love to hear if there are other successful candidates.

Pictures can be found in this album: /g/TekScopes/album?id=64919

un saludo,

Leo

Be careful about using a fet with a higher voltage rating, as the voltage rating goes up, so does the the gate capacitance and the
22xx drive circuit is marginal to say the least.
Check drive circuit carefully!

I have learned the hard way to disconnect the voltage multiplier early in the troubleshooting procedure.
A bad voltage multiplier puts a large load on the rest of the power supply.
Get all the low voltages right first.

-Bert

Unless it's an expensive IC, troubleshooting a circuit like that is difficult since it is only read once while the SA is booting up. That's why most people would just change a gumdrop IC to attempt the repair. There isn't much else that could cause an error like that.

I used to spend full days testing and repairing MC68340 based embedded controller boards That IC is part of the Motorola 68000 family.

I am in Florida. I am looking at a portable shed to use as a new shop until the 1200 square foot shop is usable.

Michael A. Terrell

To be fair, some of the members are just getting into electronics. I've been at it for over 50 years. At one point I spent eight hours a day testing new circuit boards and repairing the bad ones. My work was better the the two women in rework, and they had better toys than my couple Ungar Loner irons.

For my own work, I prefer a vacuum desoldering iron. In days past I replaced thousands of bad DIP ICs with a Radio Shack desoldering iron. I did use some wick for desoldering, but I used regular copper braid and liquid RMA flux because it does less damage. NASA referred to it as 'wet wicking' and recommended it because it caused less damage to circuit boards. Also, when you trim the used part of the braid, leave about half the width of the wick of used wick. This allows you to transfer the heat faster, and starts the capillary action faster.

I recovered and sold thousands of 256K RAM chips back in the 286 computer days with a solder pot. We sold them for $2.75 each, and we had people begging for them because there was a world wide shortage on the spot market. We would get boards with 144 of them, and I could remove all of them from a board in under five minutes with minimal or no damage to the PCB.I used surface tension to have the solder slightly higher than the edges of the solder pot, and a special pair of pliers or a long, thin stainless steel rod that was ground flat at the end to slip it under the ICs.


Michael A. Terrell

Hi Vincent,

this is funny, after my previous post I went looking for a Faster, Lower On-resistance, Higher Voltage FET, and found this one: IPA60R280E6 , so this is in the same area as the one you advised and used.. :-) :-)
From the same seller I ordered some ultra fast diodes ER506 (600V 5A 35ns) as replacement for CR907, so these should work too.

BTW, in the beginning my choosen FET and diode did "work", but that was because C956 still had a short, so the neon's were blinking.
It never had to deliver the actual power to the scope.

After I fixed C956, the primary PS died instantly because of the wrong FET.

Thanks for the advise, will keep you posted as soon as the parts arrive.
(I am in inland Spain, so be patient)

Leo