Type 547 Restoration

[MED6753]

In order to get up to date on this project read these 2 posts first.

https://www.eevblog.com/forum/testgear/ ... msg4257175

https://www.eevblog.com/forum/testgear/ ... msg4261495

So a year later it's back on bench 2 to complete the restoration.



I'm not happy with the foam tape I installed to fill the gap between the plug-in and mainframe so I'm going to remove it and I have an alternative in mind. Stay tuned.



The HV assembly was removed and sent to Germany for repair and returned earlier this year. I have it double sealed to guard against moisture ingress. I will be performing my own 6 hour bake out at 150 degrees F as I did with the other two Type 547's. Then install with desiccant bags and sealed.



The last time this scope was powered up was well over a year ago and it was stable. But before applying power I will ESR check all the filter capacitors. If they check good they will remain in place. Once a successful burn-in then a functional check and calibration.

[MED6753]

The foam tape has been removed and in it's place is self adhesive felt lining. Much better fit. And in the process of trimming the felt I discovered that the chassis is bent front to back as well as side to side. I'm surprised the plug-in fits at all and engages the connector. But all seems OK.





Next on the agenda is 6 hour bake out of the HV assembly.

[BU508A]

Hei med,

what do you think about this 547?
It just showed up in the German Kleinanzeigen.
Seller is saying, that likely the deflection is broken. Beam is visible, sadly he did not take a picture of it while the scope is on.

https://www.kleinanzeigen.de/s-anzeige/ ... 3-168-6931

[MED6753]

Appears to be in decent shape. Depending on which deflection is broken the fix will be easy or not so easy. Horizontal deflection issues are fairly easy to fix with readily available parts. Vertical deflection is a different story. Depending on S/N the vertical output transistors are unobtainium or difficult to source but not impossible. But the older S/N's can be upgraded to the new transistors with very few additional parts and I've successfully completely that upgrade on one of mine.

I would ask the seller to indicate which deflection system is not working. The asking price is reasonable as long as that is the only issue.

[mnementh]

Hei med,

what do you think about this 547?
It just showed up in the German Kleinanzeigen.
Seller is saying, that likely the deflection is broken. Beam is visible, sadly he did not take a picture of it while the scope is on.

https://www.kleinanzeigen.de/s-anzeige/ ... 3-168-6931

Ooooh.... Tektronix Holland. Now I'm imagining Pippi Longstocking getting zorched by a unprotected anode during final testing...

mnem
At last... the mystery of that hair finally revealed...

.

.

[BU508A]

Appears to be in decent shape. Depending on which deflection is broken the fix will be easy or not so easy. Horizontal deflection issues are fairly easy to fix with readily available parts. Vertical deflection is a different story. Depending on S/N the vertical output transistors are unobtainium or difficult to source but not impossible. But the older S/N's can be upgraded to the new transistors with very few additional parts and I've successfully completely that upgrade on one of mine.

I would ask the seller to indicate which deflection system is not working. The asking price is reasonable as long as that is the only issue.

Thanks med for your comments.
I'd really thought about it to purchase that 547 but since it is pick-up only it will not pay off. One way would be around 500km from here to Zapfendorf.
Hope, it will find another good home.

[mnementh]

Oh come now... would be worth the trip just so you could say you've been to a place with the audacity to call themselves Zapfendorf...

mnem
*now imagining a city populated entirely by Zap Brannigans... yes, even the girls.*

[BU508A]

I knew it, that somebody will find "Zapfendorf" amusing.
Btw, such names aren't that unusual for Bavaria.

[MED6753]

The HV assembly is currently in the oven for a 6 hour bake at 150 degrees F (66 C).





It will be sealed up again for pending install.

[mansaxel]

I knew it, that somebody will find "Zapfendorf" amusing.
Btw, such names aren't that unusual for Bavaria.

I assume that Koppelstangenhof is nearby and both are adjacent to the river Welle where it passes through the Achslager valley.

[tautech]

The HV assembly is currently in the oven for a 6 hour bake at 150 degrees F (66 C).

Served best with a red, a white or Bahama Sea blue ?

[MED6753]

Checked all the electrolytic capacitors with the Peak Atlas meter and got some interesting results. And before anyone asks the meter is working properly. I checked it on new capacitors. Of the 16 electrolytics checked 11 of them displayed results as shown. That is a dismal result. To insure there was no other circuit interaction I also isolated the capacitors and got same result. Now if I were to apply power would these "leaky" capacitors do a quick reform? Maybe. Or perhaps short out. Do you feel lucky? Not this boy. Or should I perform a tedious reform process with no guarantee of success? Not going to waste my time. This tool pretty much backs up what I've said all along. Any electrolytic capacitor >40 years old should be changed. And that's exactly what I'm doing, even the ones that tested good. Mouser order has been submitted.

[MED6753]

Since I had the room in the new lab this is why I went through the trouble to expand bench 2. Even a full size 500 series can be placed on it's side with plenty of room to spare.

[MED6753]

I was going to install the HV assembly today but got distracted on other things. Hopefully tomorrow and then work on the replacement capacitors which were delivered today.

[MED6753]

The HV assembly is now installed with desiccant bags.



Cover installed and wire entry areas sealed with silicone.



Since I was in the neighborhood replaced C802 which is part of the B+ to HV Oscillator decoupling network. The original can was disconnected and left in place.



Next on the agenda is replacement of the balance of the PSU capacitors.

[MED6753]

Due to the latest data obtained here this project is now on hold. Any changes/updates made to those two Type 547's will obviously affect this current project.

viewtopic.php?p=4651#p4651

[MED6753]

I've made an executive decision, which means it's probably the wrong decision, to terminate this project. My reasoning? I already have two functional Type 547's and the potential for needing replacement unobtainium parts in the future is high. So this scope will become a parts unit. And if I find a source for re-winding the HV transformers this scope will give it up for that grand experiment.

And quite frankly. I need to move onto something else. Off to Ebay.

[Zenith]

I'm sure it was a difficult decision, but you made a sensible and measured choice, which we can all respect.

The bane of my life is a Schlumberger/CRC 4760 sweeper, which came with the even more rare manual for about £10 at a swapmeet years ago. It was one thing after another. When the PSU was sorted out, and many dead tants replaced, it worked on the bottom range, 0.1 to 12MHz. The top range, 1 to 120MHz was elusive, as was the metering. The thing appears to be jinxed. In the course of working on it my HP8640A died twice, with minor faults and my Tek 475 also died twice, once because of a dead smoothing capacitor, and once because a small signal transistor in the Y amp decided it was time to depart this world. Finally, a hard to find and expensive varicap diode in the sweeper vapourised with a voltage applied as directed by the manual.

The last time I looked at it a few months back, the power lines were all over the place. Probably more dead tants.

I should just throw it away or take it to a swapmeet and get rid of it and its gremlin. I don't actually need it as I have an HP8601 and couple of DDS function generators which are better. I just don't like the idea of being defeated by it.

[vk6zgo]

The main albatross around my neck is my Tektronix 7613.
I have been, on & off, trying to fix it for years, but it has been heavy going.

It originally croaked, seemingly a simple power supply problem, when I was using it to fault find a ham transceiver.
At around the same time, another radio, & a 13.8v power supply also died, so most of my "on & off" has since been devoted to trying to get at least something sorted, whilst looking guiltily over my shoulder at the poor old 7613 mouldering away in the corner.

My little "Digititech" 10MHz 2"screen analog thingy has done sterling service, allowing me to at least trace the 9MHz IF in one of the radios, & I even stretched the bounds of friendship, using it to look at the transmit side's 28MHz output.
Ain't graceful response taper off great? ---- Much preferable in this case to "precipice" style cutoff!

At the last Hamfest, I picked up a BWD 845 , both because it is a bit of a collector's item, & because it has a nice big display AND I can get my Delayed timebase "hit".
I spent a morning tracing through another radio, pinning down the faults with some ease, & enthusing at how easy things are with "a proper CRO", only for the thing to lose both horizontal timebases.

The downside is that its book isn't as good as the 7613 one, but a very big upside is that the previous owner, who is a very savvy person, added extra pages referring to previous faults & how they were fixed.

It failing is a bit sad, though, as I had planned to clear the decks of ham radios & use the BWD in an attempt to "Blitz" the 7613 in hopes of finally fixing it.

[tautech]

Sounds like a fine project for us to look into when I run outta things to do while over your ways Bryan.
Had better find a 7613 manual and do some swat......

What's its fault ?

[tggzzz]

The main albatross around my neck is my Tektronix 7613.

I used a 76xx and 465 in the late 70s early 80s.

I liked the 76xx large display and needed 4 traces (no logic analyser was available). But my principal memory was that I had to be careful that it was working as I expected. Too often I needed to, ahem, reseat the plugins. Or worse.

The 465, despite its Heath Robinson internal construction, just did its job.

Hence I've never been tempted to get a 76xx for more than 5s - except for the sampling plugins. But now that desire has been sated, I'm pleased to say.

[bd139]

Probably mentioned this before but back in the 90s there was a mini revolt where I was working because people didn't want their 7904's replaced with "some newfangled digital thing" despite it usually being a HP 54615B (500MHz 1GS/sec). That meant lots of "for indication only" stickers on the things. Dicky plugins, power supply problems and rickety probes aside they have a feel about them which is hard to replace. Some of it's the awesome size that feels like it's actually better at doing the job, something which may be shared with the likes of a 547. Of course when they finally pulled the plug on that, they disappeared out of the skip like lightning. I suspect based on the age of the usual users, they probably ended up at hamfest SK sales around 2003-2013

Alas I didn't get either what with being the TE department resident monkey and had to use whatever was piled up in the corner, usually some Philips PM3217 that had been rotting for a decade. Still a good scope.

[mansaxel]

My "on-going project" is the Tek 5440, which has been diagnosed with multiple faults.

The first, of course, was a tant across the most important voltage in the PSU, which controlled all the others.

Second is as of now still undiagnosed -- one of the vertical plugins places a short on one of the supply lines. Since it is the slowest of them, I have bypassed this by pulling the plugin, only to meet Error No 3.

Third and current is the apparent failure of the Tek proprietary IC in the horizontal plugin where all the magic more or less is contained. It probably replaced another full length PCB in the plugin. Diagnosis said "it has nice 5V, but it chooches not". (which diagnosis procedure also proved the age-old saying that you need at least two scopes, one to fix the other.) I have a replacement IC, procured at some cost from the Greek parts store. Now I only need to dare replacing it... It is not the price of the component, it is the high content of Unobtainium in it that scares me. Sphere were out of stock, for instance.