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I agree with Stephen. Use enough iron! If you use too small of an iron
you'll have to hold it on the board for too long while you wait for the
solder to heat up enough and melt and there's a good chance that you'll
overheat the board and cause the copper traces to lift. Also get a
temperature controlled soldering iron if you don't already have one. I
guarantee that it will make a marked improvement in your soldering
ability. And with a temperature controlled iron you almost can't use too
large of a soldering iron! If it fits, it will work!

Before you start make sure that the iron, the solder and the joint are
all as clean as possible! I use Kester 2% silver solder and it has a very
low melting point, 300F or so. It mixes with the original solder and lowers
the melting point so that I can quickly unsolder the joint and avoid any
chance of overheating the circuit board or the part. For unsoldering
something I set the iron at about 650 F and melt some of the solder onto
the tip of the soldering iron then apply the tip to the joint on the
non-component side of the circuit board. I already have my manual solder
sucker cleaned, cocked and ready to go. Once the solder on the joint is
thoroughly melted, not just the top melted, I use the solder sucker to pull
up the molten solder. If done correctly you shouldn't have to hold the iron
on the joint for perhaps two to three seconds and it will remove all of the
solder from the joint except for perhaps a very slight amount directly
between the lead and plated hole. I then use a small flat blade screwdriver
to push the lead sideways in the hole and break the lead free from the
plating if it's still attached. If I did the previous step correctly then
the lead is usually already completely free. It should take only a small
amount of force to break the lead free, don't force it. If it won't come
free then there's probably still solder on the reverse side of the board.
Only after I've checked and made sure that all of the leads on the part are
free do I lift the part away from the board. It should come free with no
force whatsoever. On double sided boards after you use the solder sucker,
you need to look at the reverse side and be sure that the solder there was
melted and removed as well. If it's not then you probably didn't wait long
enough after the solder started to melt to allow ALL of the solder (on both
sides of the board) to melt. If that's the case then you need to resolder
the joint and then desolder it all over again. I've never found any other
reasonable method of getting all of the solder off of the component side
other than resoldering and starting over again. I developed this method
while repairing circuit boards that could NOT be replaced at any cost and
that not damaging the boards was absolutely the top priority. Once I worked
out all of the materials and techniques it worked extremely well and I've
repaired thousands of boards using this method. FYI I've tried vacuum
operated solder suckers such as Pace brand but I still prefer one of the
manual ones. It's just easier to use even if I do have to manually cock it
each time. Keep the tip clean and pull the tip off every so often and clean
out the old solder inside of the sucker and regrease the piston and they'll
work on and on and on. I've acquired a few more of them as spares but I'm
still using one that I bought back in the 1970s. If it's operating
correctly, you can cock one then put your finger over to tip and then fire
it and the piston will back back part way but not all of the way due to the
vacuum inside of it and it will *hold* the vacuum.
I probably have or or have had at least one of every brand of soldering
iron out there and a wide variety of Pace and other soldering and
desoldering stations but I do most of my work using a regular Weller or
Hakko (929 IIRC) temperature controlled soldering iron and an antistatic
version of the Soldapullt solder sucker. I've also used the metal Paladin
solder suckers but for anything larger than a small joint I like the
Soldpullt because it's slightly larger and pulls more air. BUT, it's very
important IMO that you use a *top* quality solder such as Kester even when
unsoldering a joint. The Kester 2% silver loaded solder is hard to find and
is now stupidly expensive but it's by far the best solder that I've ever
used and I HOARD every bit of it that I can find and I use it very
sparingly. I won't waste my time trying to use lead free solder. FOR
ANYTHING!

I started out soldering, *and desoldering,* with a 200 Watt American
Beauty soldering iron with no temperature control. You should try that
sometime! I delaminated a lot of circuit cards!

Thanks everyone!! Doesn’t look so formidable a job now.

Bill

Hi Michael,

Last night my curiosity got the better of me and I searched for and found the DM501 schematics.

BTW, the Tek Wiki's DM501 (not DM501A) manual is incomplete, and I found one with complete, if unmerged, schematic pages. Good enough for my needs. But I should get this to the Tek Wiki admin to update. That's on me.

With that I brought in the plug-in which sacrificed itself for the cause. Along with its stink - that was a mistake, but it's cold out in the garage. I studied it against the schematics and board layout. Here's the dope: The trace that fried is not only connected to 33v common, but also traces back into the plug-in where it is grounded to the chassis. More careful examination of the failed trace does look like current was trying to travel down both branches to both "grounds". The connection to pin9B happened to loose first. But there's a distinct source from R421 that travels down both branches, one to 9B, the other to the chassis ground. So R421 seems to be the source of the current.

I did initially think: "the 33v common is ungrounded!" I ran back down to the garage, pulled out the TM504 and verified that indeed the 33v common has continuity to ground. A couple/few ohms due to connector grime? So it's not like the 33v common has something untoward on it. I did also verify the source fuses are correct capacity and type. I powered up the unit and verified the 33v common is at 0v relative to chassis ground.

Somewhat humorously, R421 is driven by a pot, R420 from pin 5 of U420, and R419 from pin 6 of U420. This is the 5v adjust. That circuit is driven by 12v derived from the +33v supply and a Zener, VR410, 12v. If VR410 opens, does the 12v rise and create over-voltage on the +12v supply in the plug-in? I would test, but I'm not plugging that thing back into a working PS unit quite yet.

The second plug-in that had started to burn had a singular trace from pin 7 (gnd) of a 7400 14 pin DIP. No apparent trace to chassis ground, nor any other component. I didn't dig too much deeper into that plug-in: DC504 (not A). The 7400 is one of many IC components driven of +5v derived from +33v by U405. Again, not powering that up any time soon to further debug.

So at this point the issue seems to be bad plug-ins, not something generally wrong with the power supply units. I do need better test equipment (working on that), and should find a better current detection setup before I go testing more plug-ins.

I should note these plug-ins are ancient. Many/most have calibration seals on them with due dates in the 90s - if not earlier. The seals on these two plug-ins were unbroken suggesting they haven't seen power in almost 30 years. As other recent experience has revealed, things do go bad just sitting in dry warm climates. Time to bust out a lightbulb setup? I also do have a vaiac that is due to arrive tomorrow. Just part of the learning process. The TM5xx series units are _not_ robust supply units. Rather quick-n-dirty cheap products. A little disappointing, but caveat emptor.

Dave

On Mon, Apr 26, 2021 at 10:39 PM, Alan Young wrote:

I have put a bid in on a 2246
which was rather low so I doubt that will happen.

If you will be considering one of the 224x line of scopes (2245/2245A, 2246/2246A, 2247A, and 2252A), I'd aim for the 2247A model, it has a couple of very useful additional counter/timer features over the 2246 like direct frequency/period readout which might be handy for amateur radio work, and this model should in most cases command a very similar price as the 2246/A. Or at the very least try to the the improved A version 2246. The next option would be the 2252A which is one up from the 2247A and the only difference is that the 52 has one additional blue button on the front panel labeled "Hard Copy" that allows to print the screen. But in all other respects the 2252A is exactly the same as the 2247A, although it does not come up for sale as often. I have owned a 2247A for 10 years now, and even though I have other scopes including a spec-wise much superior 2465B, the one that almost always gets fired up first is the 2247A as it is a very intuitive scope that has tons of nice and easy to use features. The only thing I had to do to it so far was to preemptively replace all the fast rectifier diodes as it is recommended, and twice the internal Lithium battery (the one that originally came with the scope was already dead). This scope also does not store any cal constants in volatile memory so the demise of the battery does absolutely not affect calibration.

All in all I'd say the 2247A is a nice middle ground between the lower cost design 22xx line and the higher tier 2465/67. Yes the 224x scopes power supply requites a bit of disassembly but nothing as complicated as the 2465. Even the 22xx line requires some disassembly to get to the power supply by removing the shielding cage and the bottom plastic cover, which sometimes can be a bear to remove, so no free lunch on any of these scopes in terms of working on recapping or repairing the power supply which is a given on scopes of this age unless the previous owner has gone fairly recently through the process.

On Tue, Apr 27, 2021 at 09:45 AM, Dave Peterson wrote:

In case you haven't already come across these things:

Here's the adapters Paul is referring to:

eBay listing number "273254508468".

I have used this seller's products for years. They are excellent. Also note that he has added a larger via to allow the use of "snap in" capacitors. This opens up another group of capacitors for your projects. His previous design used 3 small vias for + and - sides, those vias would only fit "standard" wire leads, snap in cap terminals would not fit. With the addition of the larger via ion the group, you can easily use snap in caps.

--
Michael Lynch
Dardanelle, AR

Hi Bill,

I slip a single ended hacksaw blade just under the cap, and saw off the lugs to remove the cap.? After that, very little heat is needed to remove the nubs from the board.

Make sure you do not leave any filings behind.

Good luck !

--
===============================
Scott Singelyn
Information Systems Manager
Flat Rock Metal, Inc.
26601 W. Huron River Dr.
Flat Rock, MI 48134-1090
Phone: (734) 782-4454 x 2660
Fax: (734) 782-5640
===============================

Dave,

What about "9A"? Any damage to that trace? Both 9A and 9B are tied to the 33.5 Common return. Are the fuses on the +33.5 Supply the correct "Fast Acting" fuses of the right current rating? I do not have answers to your other questions. I have never encountered or even heard of this phenomenon and I have several Power Modules as well as 2 dozen working plug ins.

The only way I have burned up a trace is when I plugged my flexible extender card to the module "upside down" (I know, DUMB Move!). I did have a few components go BOOM when i turned on the power. .

--
Michael Lynch
Dardanelle, AR

In case you haven't already come across these things:

Here's the adapters Paul is referring to:

eBay listing number "273254508468".



Seller is:



Or search for "Capacitor Adapter 15.5mm triangle".

Worth reading:

/g/TekScopes/files/Tek%20465%20Power%20supply%20Capacitor%20Replacement%20Guide%20-from%20web-/_Tek%20465%20Power%20Supply%20Capacitor%20Replacement%20Guide.pdf

Note that's from this groups files section. Search for "465 Power Supply Capacitor" to find it and others.

A message on this board where I describe the caps I selected to order from Mouser: /g/TekScopes/message/176235

If you go back to the beginning of that thread there's a link to a photo album showing a problem I encountered: /g/TekScopes/album?id=258720

The little trace circled in red in one picture shows the little jumper trace on the backside of A9 coming from C1512. It was the trace via from the front side to the back side that pulled out with the cap body when removing it. It didn't so much as pull out as disintegrate in tiny pieces that I didn't realize where there. I didn't find the problem until it was all reassembled and this little route wasn't reconnected. The solder wouldn't flow from the front to rear through the via without the trace material there. It was a bear to get fixed. Cautionary tail: continuity check all vias before reassembly. Repair damaged ones with copper tape. Available in mass quantities on Amazon.

Good luck and enjoy! It's very satisfying to recover a scope that's in good physical condition.

Dave

I've never had any problems but I have a Metcal setup. Suitable high end equipment (Pace, Metcal, etc) always helps.

Chipquick might be a good way to lower the melting point on those joints and minimize damage to the board.

And of course, use the little adapter boards to mate the modern snap cap to the 4 pin layout for the NLA original caps.

Paul

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows

I have successfully changed all the caps in one of mine, a a few other as well.
I used a fairly powerful iron with a broad and thick tip. That will melt the solder very quickly, especially if you add some in the process for better heat conductivity. Suck the solder one pad at a time. When all the pads are done, reheat them a bit, one at a time, and slightly wiggle the cap from underneath. Do that very gently; some pads are also connected on the other side. If you don’t suck all the solder, you risk breaking the pad when pulling the cap. Remember to check all the connections on the other side of the board too.

Hope that helps.

Before I jump into replacing the low voltage power supply filter capacitors I wanted to see what technique others have used. My concern is damaging the circuit board. What is the best way to remove the solder while avoiding damaging the circuit board?
Thank you,
Bill

Hi!

I got two non working 7603 so I’m trying to get at least one of them to work.
Just got one of them (which is in very good external shape!) for free from a very friendly man here in Sweden who has a huge collection of electronic stuff.

The one I just got had a faulty power supply so I’ve borrowed a few parts from my other 7603 got good results for the +5, +15, +50, +130, -15, and -50, they are all well within specs. But I got nothing showing up on the CRT.

This is what I got when I look at the horizontal deflection plates:


What’s the next step? Swap some boards from the other 7603?

I mainly work with guitar amplifiers so I don’t got much experience working on scopes but I got some “basic bench equipment” and can measure up to 30kV if needed. ?


All the best,
Henric

www.facebook.com/hermanssonamplification

Alan,

If you are unwilling or unable to repair a scope then my first advice
would be that when it comes to E-bay, don't buy anything that isn't
classified as "New" or "Used". Under E-bay's rules, anything sold in those
categories must work, regardless of any disclaimer that the seller puts in
their description. If the item arrives and doesn't work or is damaged or
not as described, then per E-bay and PayPal's rules, you are entitled to
all of your purchase price back and any shipping and/or packing fees that
you paid. And the seller must pay for the return shipping if he wants the
item back. It's a pretty iron clad guarantee and E-bay and PayPal WILL
enforce it, but only as long as you buy an item that is "New" or "Used". It
helps to keep records and photos of everything. If I get a package that
looks beat up, I take pictures of it before I open it and more pictures as
I open the box and before I remove item, then more pictues as I take the
item out and then of the empty box and the packing material that was in it
and then all sides of the item. And more picture of the inside if I open
the item up. I bought a complete original BC-348 radio from E-bay a few
years ago and it was packed unbelievably poorly and smashed when I got it.
And I had very specifically asked the seller to pack it *well* and offered
to pay extra for that but he didn't do it. He just crammed it in an
undesize thinwall box with a single sheet bubble wrap. He and I went round
and round about it but I finally filed a claim with E-bay, sent them the
pictures and they *immidiately* refunded my money and paid me to ship the
item back to the seller. By the time that it was over with, the seller not
only didn't make a penny on the sale, he also paid almost $180 for the
shipping!

For tube type equiptment, you really shoud try to avoid shipping and
try to find something locally that you can go pickup in person. For big,
heavy or delicate items, when I search E-bay one of the things that I like
to do is to sort the results by distance from me. If I find something
nearby I then contact the seller and make sure that they allow local pickup
before I buy. I've bought dozens of big heavy items such as linear power
supplies and this has wrorked out well for me.

Post up your location and someone here might be able to help you out.

Joe

Hi all,

As a first timer here, I thank you for your replies. The enquiry was on behalf of a friend who has a 1503c with a cracked screen, so replacement is his only option.

I'll follow up the links that have been posted, there may be a solution to be found...

For myself I've one point five 1503 with crts in them (one only half works and will be kept as spares if I can't resurrect it - it's been 'modified' shall we say...

Old technology never dies, the repairs just get newer

Hi Alan,

The 2246 is quite a nice scope, but a big change from a 465, and maybe more than you need for the kind of work you want to do. In the 2200 series there are some very nice, lower priced scopes that will probably meet your needs; I would consider a 2215/2215A or 2235/2235A as common, full-featured scopes.

The advantage of the 2215 and 2235 is that they are easy to work on and do not require much, if any, unobtainable parts to repair their most common failure modes. The 465, from the decade before the 2200-series, has more parts that are no longer obtainable, can only be obtained at significant cost, or must be salvaged from another scope. That is not say anything bad about the 465: it's a beautiful instrument, easy and fun to use, and built like a tank (both in durability and mass). The 2200-series were a cost-cutting effort by Tek in the 80s to compete with new foreign competition, and they feel like it. The 2200-series are still very good scopes, but they feel more flimsy (on the up-side, they are much lighter than a 465, which may be a concern for you, depending on your disability).

The features of a 2215 or 2235 are very similar to the 465, right down to having very similar controls for most functions. The 2246, being a much later entrant in the 2200-series (and actually looking a lot more like a 2400-series scope) has significantly different controls than the earlier scopes, so it will feel very different when you use it (it will also have features that the earlier 2200-series, and the 465 lack, like cursors, on-screen readout, and automatic measurements, so it's a trade off).

Any scope of this age, both 70s era 465s and 80s era 2200-series scopes are going to have dried out electrolytic capacitors. The problem gets a little worse with newer old scopes (late 80s/early 90s vintage) that have particularly destructive surface mount caps. The 2246 is right on the boundary for those specific bad caps, and the pictures I see of the insides on TekWiki don't seems to show any of them, so maybe that's not an issue for this model. Certainly the 2215/2215A or 2235/2235A do not have the bad surface mount caps.

That said, yes the switching power supplies have some specific failure modes that can apparently be challenging to diagnose, but the easy of servicing the 2200-series makes up for some of that, I think. I have worked on both the 475, which is almost identical to the 465, and a number of 2200-series scopes, and the 2200-series are arranged so that you can much more easily access both sides of the PCBs, even in the power supply section, while the 475 (and 465) can require significant disassembly to get to the power supply boards. Also, since the 2200-series are much lighter than the 400-series it is easier to move it around when working on or with a 2200-series scope (the 2215 weighs about 13 lbs, while the 465 weighs about 23 lbs).

Just my 2-cents.

-- Jeff Dutky

Welcome Joe!

Do you have the Service Manual hardcopy? Or have you downloaded it from the Tek Wiki page?




There should be a fault tree in there (don't have a reference at hand at the moment), and it does sound like you might have a CH1 trigger issue. Or an issue with the sweep logic. Also on the Tek Wiki is an excellent document on "Troubleshooting Your Oscilloscope" in:




The Tek Wiki is a great resource.

Hope this helps.
Dave

Hi Joe,

A 10:1 probe is actually the norm, because that's how you get to 100MHz bandwidth. A 1:1 passive probe is fundamentally limited to a small fraction of that (~5MHz for a 1m-long probe).

If you look more closely at the BNCs on the front panel, you'll see that they are not ordinary BNCs. There's an insulated ring that contacts a spring-loaded dingus that protrudes from a proper Tek probe to trigger the x10 LED.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

Hello All,
I am in a situation where I have been physically disabled. I am an amateur radio operator and am looking for a scope for general purposes. My partiality runs towards a 465 as that is what I used in the Coast Guard in the mid 70's. It was state of the art and I always thought that we somehow lucked out to get them. Most of our scopes were Dumont or Fairchild surplus from the Navy. We almost never got new test equipment. I am looking for a scope just to play with associated with hf stuff 50 MHz and below. I see a lot of 465's on Ebay and would love to have one just for nostalgia. I have put a bid in on a 2246 which was rather low so I doubt that will happen.
I guess my question is would the 465 be a better bet than something like a 2246 for tinkering? I do notice that the electrolytic power supply caps seem to be a problem with the switching power supply on the 22xx series and I'm not sure I can physically replace then if needed.
Again, my use for a scope is tinkering. The 465 for nostalgia.
Any thoughts or help would be most appreciated.

There is a tremendous wealth of information on this site and I can read posts for hours!

Thanks,

Alan Young
N5AGY

I bought an 456B and mostly it seems to be in good working order. I have a couple questions and appreciate your time and help.
When using different sine wave inputs on both A & B channels pretty much match my Rigol1054. All of volts/div and time/div settings seem spot on. Nice sharp focused beam. Really very good for a scope sold as “for parts”.
Using the Source trigger NORM, LINE and CH 2 triggers fine, but it does not appear to trigger at all on CH 1. I can adjust the Holdoff to stop the scrolling, no TRIG light...

With 2 different sine waves on CH1 and CH2 1 get a blank screen with XY mode, the volts/div dials DO light. When pressing Beam Find I get a vertical line and a height I can adjust with volts/div but no horizontal deflection at all.
I will go through the calibration check list, this may be a problem somewhere on the horizontal board? Both problems may stem from the same place? I’d like to have more of an idea of possible problems before attempting any calibrations.

I realize that the volts/div maxes out at 5, but there are 10-20-50 V/Div on the dial. If I’ve read correctly these are for special probes (10x etc). Is there some sort of probe sense that lights up at the 1 o’clock position of the V/D dial? There doesn’t seem to be anything special on the BNC connectors on this scope...

Thanks I’m advance for any input!

I had a problem with my display recently, and in my research gleaned that they are rare. However, I managed to repair mine - a relatively simple problem with an elastomeric connector. But your fault may be quite different from mine.
There is a long thread over on eevblog on this topic (in the repair section - if I was more savvy, or sitting at my desktop, I would add a link). A number of people have fabricated ‘modern’ replacements.
Happy to talk more if you think repair is an option for you...
Roman