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 Post subject: Have some Tek 575 restoration questions
PostPosted: Nov Wed 26, 2014 1:40 am 
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Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
Hey guys & gals,

I've done all of the factory recalibration procedures on my newly acquired Tektronix 575 curve tracer (circa. 1964) and I've reached the point where I know a little more than when I first started working on this grand old beauty. Now, I need the kind of assistance that you folks are best at. So, please allow me to start off with a question regarding some glitches I'm seeing in the 575's CRT.

I get these blank spots on the curve traces that come and go on the CRT regardless of where I position the curve family within the X, Y plane. My -1700V adjustment is spot on and my 300V, 100V, and -150 are all within factory spec. However, I noticed that during my last calibration when my line vo!ltage was set to the required factory recalibration value of 117V, those sporatic missing pieces of curve traces (like watching air bubbles pass through a bend in a clear water hose) were replaced by larger missing traces that didn't oscillate between solid and bubbly.

Where do I start with tracking down the reason for this type of poor "bubbly" performance? Also, the percent of ripple is within factory spec for all power supplies.....as far as I can tell.

Thanks in advance & much obliged.


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Wed 26, 2014 1:57 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25381
Location: Pocasset, Cape Cod, MA
Any chance of a photo or two? I'm leaning toward breakdown in the HV supply, intermittent arcing to ground.


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Wed 26, 2014 2:56 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16670
Location: Albuquerque, NM 87123
Sounds like poor filtering in one of the supplies. I remember having trouble with a 15 volt supply.


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Wed 26, 2014 3:42 am 
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Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
Okie dokie. Thanks for the quick reply guys. How do I post photos on the form....cut-n-paste?


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Wed 26, 2014 6:55 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 16670
Location: Albuquerque, NM 87123
For some reason I do not understand, new members are not allowed to post photos.

I think there are four 2000uf capacitors that can go bad; check these.


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Wed 26, 2014 7:30 am 
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Joined: Jan Thu 24, 2013 4:55 am
Posts: 1350
Location: South New Jersey 08077
I would suggest checking through the Intensity and Blanking circuitry looking for ripple.

_________________
Ex: Same job, same building, same phone #; 4 Corp's: RCA, GE, Martin, Lockheed-Martin: 48+yrs '14


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Wed 26, 2014 12:43 pm 
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Joined: Nov Wed 15, 2006 7:56 am
Posts: 1416
Location: germany
575 don`t like dirty food, then they can make things you will not understand.
My one is with short cable connected to an AC power constanter, perfect working. Without this it works not always clean.

Image

greetings
Martin


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Wed 26, 2014 1:19 pm 
Member

Joined: Mar Thu 12, 2009 2:20 am
Posts: 1503
Location: Dayton, OH
Johnnysan may be on the right track...

Did you recap it? There's a small number of PTM (paper) caps in the HV supply, possibly a fair number of them if you've an early serial numbered one.
(If you have an early SN, I'd look at the schematics, and parts list. They're all high voltage caps (couple of KV) and will probably need to be replace with ceramics.)

I've done two 575's, though that hardly makes me an expert.
I recapped the both, and other than minor problems, smoked series resistors, an open POT, and a few weak tubes, I don't recall any significant problems getting either up and running.

David


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 5:45 am 
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Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
Ah, there's an Img button just above the text box I'm typing into. Let's see if it will let me upload a photo. I'll take a look at the caps in the HV area (small penned-in area on the underside with a smallish transformer in it....big things seem to come in small packages). Just for the record, I'm an ex-luthier turned ex-R&D Tech, turned ex-UNIX admin re-turned ex-luthier and back to being a part-time R&D Tech. Don't quit your day job, twice! Just taking my first DC circuits course at the local Tech school, and of course, I built a few Heathkits when I was twelve.

Here goes:.....nope, no image.

Okay, let's try a URL:

http://fretsmusic.com/pics/bubbles.JPG

I've been talking to a guy by the name of Stan Griffiths at the Tek Museum in Oregon. He's a great guy and a great resource, as he and some of his fellow museum-mates worked at Tektronix for about a thousand years. Stan suggested that I look at all of the 6AN8 tubes. He said that the 6AN8's are probably the most unreliable tubes ever made. After replacing one in the 100V section, the 300V and -150V started behaving themselves.

Hopefully the above URL makes it through to you guys.


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 6:13 am 
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Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
Willitwork wrote:
I would suggest checking through the Intensity and Blanking circuitry looking for ripple.


Well, I can trace the leads from the Intensity pot back to their point of origin and most likely get pretty lost from there, but I'm willing to learn....and, what is Blanking and where do I start with that one? Thanks!


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 6:14 am 
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Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
MM wrote:
575 don`t like dirty food, then they can make things you will not understand.
My one is with short cable connected to an AC power constanter, perfect working. Without this it works not always clean.

Image

greetings
Martin


Nice looking machine. Very clean. Thanks for the advice.


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 6:19 am 
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Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
Alan Douglas wrote:
Any chance of a photo or two? I'm leaning toward breakdown in the HV supply, intermittent arcing to ground.


Sorry Alan, I'm a total novice when it comes to forums. Here's a link to a photo of the problem:

http://fretsmusic.com/pics/bubbles.JPG

I hope I'm not making too much of a mess here guys. Please feel free to advise.

-Barry


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 12:59 pm 
Member

Joined: Nov Wed 15, 2006 7:56 am
Posts: 1416
Location: germany
Barry you are right, there is a little mistake,
the short unblanking is syncron to the steps.

greetings
Martin


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 1:46 pm 
Member

Joined: Mar Thu 12, 2009 2:20 am
Posts: 1503
Location: Dayton, OH
Yeah, definitely looks like ripple...

I'm still betting on the high voltage paper caps, if you've not replaced them. Be careful, one of them (C809) is mounted directly on the HV transformer. You can pull it, but be aware of the fine transformer wires that will become detached with it.

Edit: Ah-ha. Before & After pictures of the HV cage. (Sorta, its from two different 575's.)

Happy Thanksgiving,

David

Attachment:
HV_Labels.jpg
HV_Labels.jpg [ 184.28 KiB | Viewed 4215 times ]

Attachment:
575mod122-hvcage.jpg
575mod122-hvcage.jpg [ 139.52 KiB | Viewed 4215 times ]


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 2:56 pm 
Member

Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
dholland wrote:
Yeah, definitely looks like ripple...

I'm still betting on the high voltage paper caps, if you've not replaced them. Be careful, one of them (C809) is mounted directly on the HV transformer. You can pull it, but be aware of the fine transformer wires that will become detached with it.

Edit: Ah-ha. Before & After pictures of the HV cage. (Sorta, its from two different 575's.)

Happy Thanksgiving,

David

Attachment:
HV_Labels.jpg

Attachment:
575mod122-hvcage.jpg


Thanks David, I really appreciate the time you took to number those puppies! Nice work.

There is a small spool of 2% silver solder attached to the central plane heatsink of my 575....any advice on de-soldering / soldering to ceramic?

Happy Thanksgiving,
-Barry


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 2:59 pm 
Member

Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
MM wrote:
Barry you are right, there is a little mistake,
the short unblanking is syncron to the steps.

greetings
Martin


Thank you Martin.
-Barry


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 3:03 pm 
Member

Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
Johnnysan wrote:
For some reason I do not understand, new members are not allowed to post photos.

I think there are four 2000uf capacitors that can go bad; check these.


Thanks Johnny.
-Barry


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 3:05 pm 
Member

Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
Willitwork wrote:
I would suggest checking through the Intensity and Blanking circuitry looking for ripple.


Thanks Willit.
-Barry


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 3:07 pm 
Member

Joined: Nov Wed 26, 2014 12:27 am
Posts: 42
Alan Douglas wrote:
Any chance of a photo or two? I'm leaning toward breakdown in the HV supply, intermittent arcing to ground.


Hey Alan, thanks for getting things rolling by asking for a photo.
-Barry


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 Post subject: Re: Have some Tek 575 restoration questions
PostPosted: Nov Thu 27, 2014 4:47 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 25381
Location: Pocasset, Cape Cod, MA
It can't be intermittent though; it's the same time on each step.


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