Maker Pro
Maker Pro

Tek 545B O'scope Fuse and Power

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Phil Allison

Jan 1, 1970
0
"Trevor Wilson"
**I had one of these more than 30 years ago. It was hot, noisy, heavy and
an average performer. Do yourself a favour - buy a newer CRO. Even
something as old as a Tek 565b will be a revelation. You'll even be able
to move it about, without a forklift.


** Guess I am spoiled by my almost 30 year old BWD 821 ( dual trace 50MHz )
which weighs 7.8 kgs and consumes about 17 watts.



.... Phil
 
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Phil Allison

Jan 1, 1970
0
"Jeff Liebermann"
"Phil Allison"
Compared to your usual critical comments, I presume that's a
compliment.

** No it ain't.

It can mean anything that marketing wants to claim.


** Not when the words " soap free " are right there too.

I use a brush.

** FFS -

wot a painful, boring, literal, tiresome pedant !!!!!!!!!!!!!!!



..... Phil
 
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Trevor Wilson

Jan 1, 1970
0
"Trevor Wilson"



** Here is a pretty good pic of the insides of a 545B.

http://www.barrytech.com/tektronix/vintage/tek545bright.jpg

The AC tranny looks like it *might* be 500VA - but I expect Tek would use a
conservatively rated unit with a low temp rise.

If the OP would care to measure the primary resistance - I can say for sure.

**I found my 545A manual.

Power consumption is rated at 500 Watts. Weight is 65 pounds.

Fuse ratings:

6.25 Amp Slo-blo 3AG for 117VAC 50Hz
6 Amp fast blo 3AG for 117VAC 60Hz
3 Amp fast blo 3AG for 234VAC 60Hz
3 Amp slo-blo 3AG for 234VAC 50Hz

It's an interesting old CRO. I loved and hated mine in equal measure.
After I sold it, I bought a BWD, which I then swapped for a Tek 465B.
The 465B was boring. It did everything flawlessly and never gave me a
minute's trouble in more than 20 years.

The manual for the 545A occupies 50MB. I can post if you wish.
 
P

Phil Allison

Jan 1, 1970
0
"Trevor Wilson"
**I found my 545A manual.

Power consumption is rated at 500 Watts. Weight is 65 pounds.

Fuse ratings:

6.25 Amp Slo-blo 3AG for 117VAC 50Hz
6 Amp fast blo 3AG for 117VAC 60Hz
3 Amp fast blo 3AG for 234VAC 60Hz
3 Amp slo-blo 3AG for 234VAC 50Hz


** Hmmmmm.....

Those numbers make me think the AC tranny is quite conservatively rated for
voltage and frequency.

Doing so, reduces the severity of inrush surges quite a bit.

BTW 1:

If you operate a 240V rated tranny on 120V - there is barely ANY inrush
surge at all.

( Electro caps in the PSU not withstanding. )

BTW 2:

The main source of inrush surge with tube gear is often due to all the tube
heaters being cold at switch on - particularly if the rectifiers are
vacuum tubes. The buggers take quite a time to warm up and increase in
resistance too.

But the 545B uses selenium diodes - right?


..... Phil
 
M

Michael Black

Jan 1, 1970
0
"Trevor Wilson"


** Hmmmmm.....

Those numbers make me think the AC tranny is quite conservatively rated for
voltage and frequency.

Doing so, reduces the severity of inrush surges quite a bit.

BTW 1:

If you operate a 240V rated tranny on 120V - there is barely ANY inrush
surge at all.

( Electro caps in the PSU not withstanding. )

BTW 2:

The main source of inrush surge with tube gear is often due to all the tube
heaters being cold at switch on - particularly if the rectifiers are
vacuum tubes. The buggers take quite a time to warm up and increase in
resistance too.
Which reminds me, there's a time delay in there. I don't see it on the
schematic (which is spread over many pages so I'm not sure which section
it's in), but I suddenly remember there's a point when it starts up when
things suddenly kick into operation. I seem to recall hearing the relay
kick in. Since I can't find that on the schematic, I'm not sure what it's
controlling.
But the 545B uses selenium diodes - right?

I have the B manual and they are listed as silicon. I think I would have
noticed selenium when I was inside the scope if they'd had them.

Michael
 
B

Bill Gill

Jan 1, 1970
0
Which reminds me, there's a time delay in there. I don't see it on the
schematic (which is spread over many pages so I'm not sure which section
it's in), but I suddenly remember there's a point when it starts up when
things suddenly kick into operation. I seem to recall hearing the relay
kick in. Since I can't find that on the schematic, I'm not sure what
it's controlling.


I have the B manual and they are listed as silicon. I think I would
have noticed selenium when I was inside the scope if they'd had them.

Michael
My admittedly 60 year old memory is that the A had selenium.
At work we replaced them with some special silicon replacements
when those became available. They were the same form factor so
we just had to remove the old ones and put in the new ones. I
wouldn't bet you could still get those, but it wouldn't be a
very big job to put in a terminal strip and use 2n2006, or whatever
is available now.

Bill
 
B

Bill Gill

Jan 1, 1970
0
My admittedly 60 year old memory is that the A had selenium.
At work we replaced them with some special silicon replacements
when those became available. They were the same form factor so
we just had to remove the old ones and put in the new ones. I
wouldn't bet you could still get those, but it wouldn't be a
very big job to put in a terminal strip and use 2n2006, or whatever
is available now.

Bill
Whoops! 1n2006 not 2n2006. If there should happen to be a 2n2006
available it probably wouldn't make a good high voltage rectifier.
Bill
 
T

Trevor Wilson

Jan 1, 1970
0
"Trevor Wilson"


** Hmmmmm.....

Those numbers make me think the AC tranny is quite conservatively rated for
voltage and frequency.

Doing so, reduces the severity of inrush surges quite a bit.

BTW 1:

If you operate a 240V rated tranny on 120V - there is barely ANY inrush
surge at all.

( Electro caps in the PSU not withstanding. )

BTW 2:

The main source of inrush surge with tube gear is often due to all the tube
heaters being cold at switch on - particularly if the rectifiers are
vacuum tubes. The buggers take quite a time to warm up and increase in
resistance too.

But the 545B uses selenium diodes - right?

**I doubt it. The CRO does use a time delay at switch-on.
 
N

Noel Keith

Jan 1, 1970
0
Alright. I've done a whole lot in a short ammount of time. Cleaning out theOscilloscope was no simple task, but It's done. Dried and everything. And,as luck would have it, my fuses arrived today. Now's the really tricky part: finding the right fusecap.

Not so much as finding the right one, but making a temporary one until I can find a replacement one. I've also brushed up on my electronics vernacular, so I should have a much better idea of what you guys are talking about now as well. Alright, so I haven't given it much thought yet, but I've read in a couple of places that you can make your own fusecap using a machine screw and some electrical tape. Not sure on how WELL this would work, but I have plenty of replacement fuses if something goes wrong so I'm not too worried. Is there an easier way to do this? I mean, I can assume the head of themachine screw would be on the outside while the other end would be holdingthe fuse in place. Hmmm...
Any better ideas?
 
N

Noel Keith

Jan 1, 1970
0
Alright. I've done a whole lot in a short ammount of time. Cleaning out the Oscilloscope was no simple task, but It's done. Dried and everything. And, as luck would have it, my fuses arrived today. Now's the really tricky part: finding the right fusecap.



Not so much as finding the right one, but making a temporary one until I can find a replacement one. I've also brushed up on my electronics vernacular, so I should have a much better idea of what you guys are talking about now as well. Alright, so I haven't given it much thought yet, but I've readin a couple of places that you can make your own fusecap using a machine screw and some electrical tape. Not sure on how WELL this would work, but I have plenty of replacement fuses if something goes wrong so I'm not too worried. Is there an easier way to do this? I mean, I can assume the head of the machine screw would be on the outside while the other end would be holding the fuse in place. Hmmm...

Any better ideas?
Scratch that last. Of course that wouldn't work. The fuse fits into the capand so it would obviously stick out. Hmm, anything along the same principle, then? Egh, it's been a long day -_-
 
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Trevor Wilson

Jan 1, 1970
0
Alright. I've done a whole lot in a short ammount of time. Cleaning
out the Oscilloscope was no simple task, but It's done. Dried and
everything. And, as luck would have it, my fuses arrived today. Now's
the really tricky part: finding the right fusecap.

Not so much as finding the right one, but making a temporary one
until I can find a replacement one. I've also brushed up on my
electronics vernacular, so I should have a much better idea of what
you guys are talking about now as well. Alright, so I haven't given
it much thought yet, but I've read in a couple of places that you can
make your own fusecap using a machine screw and some electrical tape.
Not sure on how WELL this would work, but I have plenty of
replacement fuses if something goes wrong so I'm not too worried. Is
there an easier way to do this? I mean, I can assume the head of the
machine screw would be on the outside while the other end would be
holding the fuse in place. Hmmm... Any better ideas?

**Install a new fuseholder.
 
M

Michael Black

Jan 1, 1970
0
**Install a new fuseholder.
No, he just needs the part that screws in.

I thought all of those were standard.

I know the problem, that $20 TMC GPR-90 I got at a garage sale back in
August just sits there, the part of the fuseholder that screws in missing,
I suspect I lost it on the way home (by bus, and walking along putting it
down every so often). I thought for sure I had plenty of the caps, but an
immediate search turned up none, and I haven't gotten around to looking in
the basement boxes. Of course, the rectifier tube is mechanically
unsound, so I need to dig the box of tubes out too.

Michael
 
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Trevor Wilson

Jan 1, 1970
0
No, he just needs the part that screws in.

I thought all of those were standard.

**I'm sure they were all standard in 1960.

It is 2013.

Things change and fuseholders are cheap and easy to obtain.
 
P

Phil Allison

Jan 1, 1970
0
"Michael Black"
No, he just needs the part that screws in.

I thought all of those were standard.


** ROTFLMAO !!

Fuse holder caps have NO standardisation !!!

There are literally many hundreds of incompatible designs.

A missing fuse cap means replacing the holder, in 99% of cases.



..... Phil
 
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Noel Keith

Jan 1, 1970
0
Yes! There! Ok, so what I'm having to do is use a bolt that the fuse end sits in, and using electrical,tape to hold it in the fuse holder. I'll be damned... Everything works! Granted, some of the knobs need to be fixed a bit and I should probably calibrate it, but IT WORKS!

http://i.imgur.com/6wdKZvM.jpg

Now I just need a probe and some alligator clips! You guys have been reallyhelpful, even if it may not seem so... I may end up replacing the fuse housing, but I really don't feel like I need to at the moment

Thanks again!
 
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