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Scope on the bench ready for refurb.
Scope on the bench ready for refurb.
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Old 26th April 2017, 11:15 PM   #1
mashaffer is offline mashaffer  United States
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Default Scope on the bench ready for refurb.

In a recent discussion here it was mentioned that I needed to get a scope. Well I have one. The catch is I need to do a little work to put it back into service.

A very generous gentleman gave me a Tek 545B with CA plugin. He said that it does power up and show a dot on screen but no sweep. There are several tubes that are broken and have gone white. They are a 12AU6, 6DJ8, and this one that I can't read. It looks like 9C... or 90... on the envelope.

SmTube1.JPG

SmTubeTop.JPG

I have downloaded a manual for the scope and one for the CA unit and the sockets are marked so I should be able to figure it out.

Normally I would just replace all electrolytic caps (at least in PS) but there are lots of cans in there so am tempted to wait on that.

SmFront.JPG

SmGuts2.JPG

SmGuts4.JPG
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Old 29th April 2017, 01:03 PM   #2
audio king is offline audio king  Canada
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The tube type is labelled on the chassis right beside every socket.
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Old 29th April 2017, 02:10 PM   #3
mashaffer is offline mashaffer  United States
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Quote:
Originally Posted by audio king View Post
The tube type is labelled on the chassis right beside every socket.
Thank you I did later on figure out what it was. Tubes had already been removed and I hadn't located the socket for this one.

mike

BTW, I originally posted in the tubes forum thus the reference above to "a recent discussion here it was mentioned"
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Old 30th April 2017, 03:31 PM   #4
kevinkr is offline kevinkr  United States
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Scope on the bench ready for refurb.
I had a 545A for almost 3 decades and the B is definitely an improvement (better CRT) - as long as you can handle the heat this is a pretty nice instrument.

Might be worthwhile to try and reform the supply electrolytics before applying power to the unit.
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Old 10th February 2018, 02:52 PM   #5
mashaffer is offline mashaffer  United States
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Resurrecting this old thread. Putting together a tube buy for the project. The three empty sockets I can find are for two 6922 (explains the 6DJ8) and a 8426. I presume that the 12AU6 must have come from that socket as they are pin compatible.

When I replace the tubes should I bring it up on a dim bulb apparatus? Gradual application of AC using variac advisable?
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Old 11th February 2018, 03:23 AM   #6
audio king is offline audio king  Canada
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That would be a good plan.The 545 uses SS rectification,so a nice slow ramp-up with the Variac should help awaken the caps with minimal stress.

Do make sure that you peer into every nook and cranny (top and bottom) of that chassis;those TEK buggers hid tubes in the weirdest places.I had a 547 run me around in circles for an embarassing amount of time before I spotted an empty socket.
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Old 11th February 2018, 04:57 PM   #7
mashaffer is offline mashaffer  United States
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Thank you. It is indeed a marvel of packaging.
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Old 11th February 2018, 06:10 PM   #8
RJM1 is offline RJM1  United States
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Funny story, Back in 1975 I bought a Tek 545 from a friend who worked for US Army Natick Labs. He bought it at auction and sold it to me for $15.00. It had been calibrated in 1974. It worked good for years. In 1982 I moved to Florida from Massachusetts and had to take a driver’s test with a 75 Chevy Nova 6cyl. They had one test called a panic stop where you stop as quickly as you can without locking up the breaks. The first time the rear brakes locked up and I failed, the second time they said that I did not stop quick enough. I then threw the 75Lbs Tek 545 in the trunk and passed! I eventually sold the scope for $50.00 in 1987 after it would not display a trace for 20 minutes after it was turned on.
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Old 12th February 2018, 10:58 PM   #9
MAAC0 is offline MAAC0  Portugal
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Nice tube collection. Useful in Winter for heating up the Bench
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Old 12th February 2018, 11:21 PM   #10
Conrad Hoffman is offline Conrad Hoffman  United States
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The 545B is still my main scope, used weekly or more often. I have fancier scopes, but the 545B has nice big knobs and takes the high gain differential plug-in, the 1A7A. Mine has been very reliable since I got it maybe 30 years ago. A problem it had was every now and then the trace would slowly fade out, usually at some critical time, say when demonstrating something to someone. Many people claimed it was caused by a faulty HV transformer. Mine turned out to be a paper cap across the HV transformer. It's been perfect ever since I changed it out.
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