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 Post subject: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 2:08 am 
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Joined: Jul Tue 22, 2008 6:12 pm
Posts: 106
Location: Winnipeg, Canada
I just acquired two of these along with a Type 585 A and a pile of Plug ins.

The hope is to get one 545 A fully restored and back in service, but the CRT is going to need replacing. It has some very odd internal scratches to the phosphors on the inside of the screen. The Operating Instructions for this scope do not go into any detail at all, from what i can see, regarding CRT replacement. Are there any other documents covering this work?

David
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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 3:23 am 
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Joined: Feb Sun 17, 2008 11:36 pm
Posts: 2036
Location: Dayton, Ohio
The Instruction Manual is what you want. There is a rubber bushing used on the "B" versions that was difficult to remove because it stuck to the base of the CRT. Every thing else is straight forward. Disconnect the anode lead, and side leads at the neck. The CRT comes out through the front after removing the plastic graticule and other hardware. Are you sure that the scratches are not on the graticule?

Marks on the phosphor might be caused by burning.

Good idea to wear eye protection, a lot of surfaces will probably be stuck after all this time.

I only have a manual for the "545B" version. There may be some differences.

I'll check out in my garage for a 545A manual.

Charlie


Last edited by tinwhisker on Sep Mon 30, 2019 3:36 am, edited 1 time in total.

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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 3:32 am 
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Location: Liberty, Missouri
Does your manual have schematics and troubleshooting information? Usually Tek manuals are on the order of an inch thick or better. Not so sure there would be blow by blow description of CRT replacement, but thats a mechanical exercise for the most part, and shouldn't be all that difficult. Its been a few years since I had a 500 series scope in the shop but I don't remember there being all that much work involved.

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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 3:53 am 
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Joined: Feb Sun 17, 2008 11:36 pm
Posts: 2036
Location: Dayton, Ohio
I edited my previous post with additional info. I found an Instruction Manual for the 535A-545A o'scopes.

Make a sketch out the pin leads, to replace them in the proper places.

(1) Disconnect all of the leads at the neck of the CRT.
(2) I used (IIRC), a long needle nose pliers on the rubber anode nipple, to squeeze the internal spring so as to clear the anode of the CRT.
(3) Loosen the tube clamp at the base of the CRT.
(4) pry the CRT socket evenly off the CRT.
(5) Remove the graticule, hardware, and pull the CRT out through the front.

Don't strike the CRT shield, as it may interfere with its function. (according to Tektronix later manuals)

Charlie


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 4:01 am 
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Joined: Feb Sun 17, 2008 11:36 pm
Posts: 2036
Location: Dayton, Ohio
Mikeinkcmo wrote:
Does your manual have schematics and troubleshooting information? Usually Tek manuals are on the order of an inch thick or better. Not so sure there would be blow by blow description of CRT replacement, but thats a mechanical exercise for the most part, and shouldn't be all that difficult. Its been a few years since I had a 500 series scope in the shop but I don't remember there being all that much work involved.


The Instruction Manuals I have include adjustments, etc. but no schematics. A separate "PARTS LIST and SCHEMATIC DIAGRAMS" publication has the schematics.

On those old 545's, a Operator's Manual was located in a "flip open" door on the top of the scope.

Charlie


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 4:49 am 
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Joined: Jul Tue 22, 2008 6:12 pm
Posts: 106
Location: Winnipeg, Canada
Thanks for the input, gentlemen.

I actually have a couple of original Operator’s Handbooks and a PDF copy of the Instruction Manual (126 Pages). Nothing at all on either replacement or installation of the CRT in the Instruction Manual.

The black marks on the face of my CRT are definitely on the inside of it. They are small stubby horizontal lines for the most part, with very crisp, defined edges. Not at all like the greyish burn lines from the beam sitting in the same spot too long.

Having never attempted a CRT exchange on anything before, I find the task a bit daunting.

David
VE4DTD


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 5:15 am 
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Joined: Feb Sun 17, 2008 11:36 pm
Posts: 2036
Location: Dayton, Ohio
The hardest part is to break loose 60 year old bushing, if present. The CRT removal is described on page 5-2 of the INSTRUCTION MANUAL. The manual for the 545B, (page 4-3), is more explicit on CRT removal.

They recommend applying talcum powder on the new CRT base, to prevent sticking to the rubber gasket. I think I used silicone grease on rubber parts, including on the anode nipple.

Also, avoid storing CRT's face down. I have been told loose particles can land on the phosphor.

Good luck,

Charlie


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 1:14 pm 
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Joined: Jun Sun 23, 2013 9:03 pm
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Location: Canandaigua, NY
FWIW, I still use my 545B almost every day. It rarely requires service and is just ideal for analog work within its bandwidth. I have a spare in the corner that's set up with odd plug-ins like the diode reverse recovery plug-in.


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Sep Mon 30, 2019 2:49 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5363
Location: Sunbury, Ohio 43074
Personally, I'd restore the 585A. I have two of them, since it was my first "real" scope back in the day. One day I'll restore one of them.

Why the 545 over the 585?

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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Tue 01, 2019 4:32 am 
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Joined: Jul Tue 22, 2008 6:12 pm
Posts: 106
Location: Winnipeg, Canada
Hi Barry.

It boils down to mice, actually. They were actively living and entertaining themselves in the 585 A, but the two 545 A’s were just pantries for food storage. A lot less damage and more parts if needed.

David
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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Tue 01, 2019 2:00 pm 
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Joined: Aug Mon 04, 2014 9:42 pm
Posts: 108
I find that in the most of my old TEK scopes, the crt clamp ring at the base is usually split into a couple of pieces and particularly the bushing has deteriorated to dust. I have make some jury rigged solutions, but some of the real things are available now and then on ebay. There's one there now, but for a 502a. They'll fit, but the metal mounting bracket will probably be useless


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Wed 02, 2019 11:50 am 
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Joined: Nov Wed 15, 2006 7:56 am
Posts: 1403
Location: germany
David do not forget, after swapping the CRT you have to do the complete calibration of the deflection amplifiers bec. the CRT is always something different in sensitivity.
Usefult Things: a well known voltage source for vertical, and a time mark generator for the horizontal
If there is no time marker you can use the AC line 50 or 60Hz to adjust the gain from the horizontal deflection.

Martin


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Thu 03, 2019 12:07 am 
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Joined: Sep Sat 13, 2014 7:05 pm
Posts: 48
This link has 545 manual
check it let me know if it helps you.

http://w140.com/tekwiki/wiki/Main_Page

have 5 Tektronix scopes here.
xxx2fan


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Mon 07, 2019 4:47 am 
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Joined: Jul Tue 22, 2008 6:12 pm
Posts: 106
Location: Winnipeg, Canada
I have now cleaned, tested and replaced as necessary, all the tubes in this scope, with the exception of the inverted ones on the right side of the chassis. I think that leaves about 10 tubes.

In addition, the scope now sports a new CRT. Wasn’t a bad changeover actually. Just very time consuming studying every step countless times. First time doing it, so quite pleased.

I will probably finish the remaining tube work next and then clean up all the knobs etc on the front panel. Decades of dust, dirt and finger grease has built up on all those little grooves the knobs sport. I can also see a few small white indicator dots are in need of touching up. After that, I need to reinstall the missing cooling fan assembly, but need to pick up some 3% silver solder before tackling that project. Once that is all done, some work on the High Voltage Supply section is lurking in the weeds.

David
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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Fri 18, 2019 12:28 pm 
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Joined: Jul Tue 22, 2008 6:12 pm
Posts: 106
Location: Winnipeg, Canada
A complete, correct, replacement cooling fan assembly has now been cleaned, lubed and physically installed back into the scope. The plan to pick up 3% silver solder last weekend was put on hold when a major, 3-say snow storm blew through town. That purchase is scheduled for tomorrow now, so the soldering work on the fan install will be completed shortly.

Once the fan was installed, I powered it up to check it out in situ. It is surprising just how much air it is capable of pulling through the chassis. And the only real noise it makes is from the air itself, being drawn through the aluminum mesh filter element.

David
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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Fri 18, 2019 6:14 pm 
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David Dunlop wrote:
And the only real noise it makes is from the air itself, being drawn through the aluminum mesh filter element.

I've found that you can get Aprilaire Super Filter Coat (to put back the sticky coating on the aluminum mesh filter, after you wash it in soapy water) at a good price from McMaster-Carr. They don't disclose the manufacturer in their on-line catalog, but when I received my shipment it was genuine Aprilaire Super Filter Coat.

https://www.mcmaster.com/2071k3

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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Fri 18, 2019 10:06 pm 
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Joined: Feb Sun 17, 2008 11:36 pm
Posts: 2036
Location: Dayton, Ohio
The metal air filter and "filter coat" oil is a little messy, but is renewable, whereas the rubber filters were handy when they were available, but, would "rot" and fall apart after a few years, especially if someone mistakenly sprayed "filter-coat" oil on them.

Don't forget to remove the shorting jumper placed on the TRIG LEVEL control during adjustments. The manual doesn't tell you to remove it when adjustments are finished.

Charlie.


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Sat 19, 2019 5:07 pm 
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Joined: Jul Tue 22, 2008 6:12 pm
Posts: 106
Location: Winnipeg, Canada
Thank you all for the information you have provided. This is certainly an interesting scope to work on, and about as far away as I can get, on the spectrum of scopes, from my existing OS-8/B!

I have ordered a book called "Oscilloscopes: Selecting and Restoring a Classic", written a number of years ago by a long term employee of Tektronix. Just received a notice this morning from the local PO that it has arrived, so some interesting reading is ahead of me this Winter!

The four attached photos are the first two of what I started out with, and the latter two of where the project stands at the moment.

Cheers for now,

David
VE4DTD


Attachments:
Tek Type 545 A Scope 1.JPG
Tek Type 545 A Scope 1.JPG [ 501.32 KiB | Viewed 594 times ]
Tek Type 545 A Scope 2.JPG
Tek Type 545 A Scope 2.JPG [ 585.54 KiB | Viewed 594 times ]
Tek Type 545 A Scope 3.JPG
Tek Type 545 A Scope 3.JPG [ 544.53 KiB | Viewed 594 times ]
Tek Type 545 A Scope 4.JPG
Tek Type 545 A Scope 4.JPG [ 619.03 KiB | Viewed 594 times ]
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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Oct Sat 26, 2019 8:39 pm 
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Joined: Jul Tue 22, 2008 6:12 pm
Posts: 106
Location: Winnipeg, Canada
I was able to pick up some 3% silver solder last week and this morning completed soldering in the cooling fan leads.

I was also able to study the High Voltage Supply to get ready for swapping a good one into the scope. That will be interesting. 9 leads to disconnect and transfer over, two of which will have to be cut and spliced. One cap will also need to be reconnected or replaced. This may take a while.

David


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 Post subject: Re: Tektronix Type 545 A Oscilloscope CRT Replacement
PostPosted: Nov Sun 17, 2019 5:17 pm 
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Joined: Jul Tue 22, 2008 6:12 pm
Posts: 106
Location: Winnipeg, Canada
I am slowly making good progress on the restoration of this scope. Still no trace on the CRT, but I have narrowed down the likely cause of that problem. Before I approach that issue, however, I have a couple of issues I need some opinions/help with first.

When my work on the scope reached the point I was comfortable in powering it up for the first time and turned it on, the first really nice sign was the main fuse did not blow, the cooling fan came on and there was the obligatory 25 second or so delay while the heaters warmed before full power came on. That’s when things got interesting in the High Voltage Supply.

The heaters in all five rectifier tubes lit up as expected but when full power came up, V842 got really bright inside, to the point where it washed out the heater glow (and any other glow) from the other four rectifier tubes, There was also a steady, intermittent crackling sound coming from underneath the High Voltage Supply Board and with each large crackle, all five rectifier tubes would blink out and back on.

I shut the scope down and pulled the Oscillator tube. It tested OK, but I had a spare available that tested better, so I swapped them out. I then pulled the feedback regulator tube for the oscillator and tested it. One half was a complete dud, so I replaced it and turned the set back on. When full power came up this time, V842 was still brighter than the other four rectifiers, but just comfortably so. What did become visible, however, was that although all five rectifiers warmed up equally during the first 25 seconds of power, within 2 seconds of full power being applied, the filament on V862 died. Since this rectifier is part of the -1350 CRT cathode circuit, and is in ‘fail mode’, it makes sense the CRT cannot produce a trace at the moment. The other nice thing that was noted, was the complete disappearance of any crackling noises and the blinking phenomenon of all five rectifier tubes had gone.

My plan at this point is to replace all five rectifier tubes with new ones, just to be on the safe side.

I have also found two resisters in the HV Supply that are running overly high: R802 should be 390 Ohms and is currently at 447 Ohms (14.6% over limit), and R814 which should be 470 MOhms and is currently 508 MOhms . This latter resister is only 8% over spec, but all other resisters are so close to spec by comparison, I figure I might as well replace this one.

Where I need some clarification is regarding some of the capacitors in the High Voltage Supply.

In Stan Griffiths book on the Tekronix oscilloscopes, he mentions a series of black, cylindrical oil filled capacitors that were used in the High Voltage Supplies. These caps had coloured rings on them and for some reason, in High Voltage Supplies, he mentions these caps were prone to failure and he recommends replacing them all, outright. In the attached photo, the ceramic terminal strips immediately left of the HV Supply board have, what I think, are three such caps: the top, third and fourth caps. In addition to the red ring at the left side of each, they are marked in red, in three rows: SPRAGUE, 160P, .047 – 400 DC (or, .001 – 600 DC). If these are the suspect caps, then I shall replace them when I replace the two resisters. In the HV Circuit, they are C801, C803 and C808.

One last oddity in this photo I need help with.

Take a look at the two ceramic terminal strips at the right hand side of the board, supporting the two 5642 rectifier tubes V842 and V852.

When I first opened up the HV Supply section, it was filthy dirty inside and these two ceramic strips looked burned black. It was rather alarming. After cleaning, however, I discovered these two ceramic strips were deliberately coated in some type of black material that covers the upper portion of the ceramic and the soldered connections. This coating does not appear on the other three ceramic strips where the remaining three 5642’s are mounted. When I checked two other stripped HV Supply boards I have on hand, they showed the exact same coating patterns on them when cleaned of dirt.

Does any one know what this coating is, why it was applied to just these two 5642 connections, and will it create any problems breaking into them to replace the two rectifier tubes?


David
VE4DTD


Attachments:
Tek 545 A HV Supply 1.JPG
Tek 545 A HV Supply 1.JPG [ 610.84 KiB | Viewed 259 times ]
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