Need help with 561A


Denton, Adam (Exchange)
 

Re the 561 HV transformer breakdown, I did successfully wind a
replacement -- see my message
http://groups.yahoo.com/group/TekScopes/message/4310

It is not too bad. The thing is, I would insist that you re-wind
a 'former that has the pri and sec adjacent to each other -- side-by-
side, with full plastic in between. I actually rewound 2
transformers -- the first was concentric (and is actually the one I'm
talking about in post 4310) but it lasted only 2 weeks before the HV
punched through internally.

So I made a new one, but used a side-by-side unit and used 2 layers
of electrical tape. It has lasted several months without any problem.

Some hints:
1) it's ok to leave some of the E's and I's out -- it's impossible to
get them all back in ;-)
2) since these scopes are not models of efficiency (my heating bills
decline whenever I use one ;-), there's no need to worry about the
windings getting too far from the core because of layers of
electrical tape.

To do the whole 'former actually didn't take more than a couple of
hours. Add to that additional time to fashion and drill your scope
to mount the new 'former.

This problem is extremely common btw. Good luck.


Morris Odell <morriso@...>
 

Or, if you
could find a 6.3 VAC, 600 ma filament transformer that could
stand to have 3300 volts applied to it without arcing to
ground, you could supply CRT filament power with a separate
transformer. I have never seen one of those transformers
either . . . I HAVE seen some good for 1500 volts, however,
so this solution will work in some other models of scopes
such as the the 530, 540, and 550 series.
I don't know what the situation is in the US but down here in Oz all the
little (Chinese made) transformers sold by the electronics parts houses
comply with a standard that specifies a 4 kV insulation rating. I have
used these for the CRT of a 543 and a 310A (admittedly a bit less less
than 3.3 kV) with no trouble at all.

It might be worth checking the transformers available these days in the
US.

Morris


Stan & Patricia Griffiths <w7ni@...>
 

This sounds like HV arcing problems to me. The 561A has a rather high
(-3300 volts, I think) on the CRT cathode. The CRT filaments are also
elevated to this voltage so the CRT will not arc internally. This means the
power transfomer CRT filament winding must also be raised to -3300 volts.
High humidity will eventually cause this filament winding to arc over
internally inside the transformer. I think I have heard of ONE occasion
where a scope owner with this problem was able to salvage the transformer.
Tek's cure was always to replace the transformer with a new one. You can
check this by first measuring the -3300 and see if it fluctuates during the
arc. If it does, you can isolate the CRT filament winding right at the
transformer terminals by disconnecting BOTH filament winding wires and then
seeing if the arcing stops. If it does, you have found the problem. If you
could find an isolation transformer good for 600 ma and an isolation voltage
of at least 3300 volts, you could insert it between the CRT filament winding
and the CRT filament itself. I have never seen a transformer like this . .
. Or, if you could find a 6.3 VAC, 600 ma filament transformer that could
stand to have 3300 volts applied to it without arcing to ground, you could
supply CRT filament power with a separate transformer. I have never seen
one of those transformers either . . . I HAVE seen some good for 1500 volts,
however, so this solution will work in some other models of scopes such as
the the 530, 540, and 550 series.

Stan
w7ni@easystreet.com

----- Original Message -----
From: "n4buq" <n4buq@aol.com>
To: <TekScopes@yahoogroups.com>
Sent: Sunday, April 18, 2004 1:06 PM
Subject: [TekScopes] Need help with 561A


I recently bought a couple of 561A's, primarily for the plugins and
to have a good supply of spare parts for my existing 561A. While the
plugins seem to work, neither of the "new" scopes work properly, and
I was wondering if someone might know by the symptoms what the
problem might be.

Both of them produce a rather loud ticking noise which coincides with
a flashing effect in the 6AS7 and the OG3 tubes. Both 6AS7's also
glow a fairly bright violet color and I'm not sure if that is
normal. On one of the scopes, when the flashover occurs and I have
the calibrator hooked up to the input, I get a blur of random traces
on the screen.

I had noticed before that my "good" 561A sometimes would tick like
this, but hadn't traced it to the source.

Is this an indication of power supply problems? I suspect filter
caps simply because of their age, but not sure if this is it. I
haven't bought a schematic yet, so it's difficult for me to do much
analysis at this point. I was just figuring this might be a pretty
common symptom and someone might be able to tell me some things to
check.

Also, still looking for a source for the power cords. Are these now
unobtanium?

Thanks!

Barry - N4BUQ





Yahoo! Groups Links







n4buq <n4buq@...>
 

I think I found the answer to my own question. The 6AS7G is bad. It
checks zero on my tester. I took the one out of my working 561A (it
checked strong in the tube tester), put it in one of the "new" scopes
and it works fine. I plan to try it in the other "new" one tomorrow
(the 6AS7G was too hot to handle easily after being on for a while
tonight).

Thanks,

Barry - N4BUQ

I recently bought a couple of 561A's, primarily for the plugins and
to have a good supply of spare parts for my existing 561A. While
the
plugins seem to work, neither of the "new" scopes work properly,
and
I was wondering if someone might know by the symptoms what the
problem might be.

Both of them produce a rather loud ticking noise which coincides
with
a flashing effect in the 6AS7 and the OG3 tubes. Both 6AS7's also
glow a fairly bright violet color and I'm not sure if that is
normal. On one of the scopes, when the flashover occurs and I have
the calibrator hooked up to the input, I get a blur of random
traces
on the screen.

I had noticed before that my "good" 561A sometimes would tick like
this, but hadn't traced it to the source.

Is this an indication of power supply problems? I suspect filter
caps simply because of their age, but not sure if this is it. I
haven't bought a schematic yet, so it's difficult for me to do much
analysis at this point. I was just figuring this might be a pretty
common symptom and someone might be able to tell me some things to
check.

Also, still looking for a source for the power cords. Are these
now
unobtanium?

Thanks!

Barry - N4BUQ


Leo Schleider <rp11156@...>
 

Hi,
for the power cords I bought a bunch of adaptors at
OEM parts in Colorado Springs. The adapter fits on
one side into the connector at the scope and on the
other side into a regular power cord.

All I could find was the old adress. They moved within
the town. So the old adress/phone number might help you
to figure out the current adress.

OEM Parts, Inc.
3025 North Hancock Avenue
Colorado Springs, CO 80907-8724
Tel: 719.635.4466 � Fax: 719.475.2249

Leo



-----Urspr�ngliche Nachricht-----
Von: n4buq [mailto:n4buq@aol.com]
Gesendet: Sonntag, 18. April 2004 22:07
An: TekScopes@yahoogroups.com
Betreff: [TekScopes] Need help with 561A


I recently bought a couple of 561A's, primarily for the plugins and
to have a good supply of spare parts for my existing 561A. While the
plugins seem to work, neither of the "new" scopes work properly, and
I was wondering if someone might know by the symptoms what the
problem might be.

Both of them produce a rather loud ticking noise which coincides with
a flashing effect in the 6AS7 and the OG3 tubes. Both 6AS7's also
glow a fairly bright violet color and I'm not sure if that is
normal. On one of the scopes, when the flashover occurs and I have
the calibrator hooked up to the input, I get a blur of random traces
on the screen.

I had noticed before that my "good" 561A sometimes would tick like
this, but hadn't traced it to the source.

Is this an indication of power supply problems? I suspect filter
caps simply because of their age, but not sure if this is it. I
haven't bought a schematic yet, so it's difficult for me to do much
analysis at this point. I was just figuring this might be a pretty
common symptom and someone might be able to tell me some things to
check.

Also, still looking for a source for the power cords. Are these now
unobtanium?

Thanks!

Barry - N4BUQ





Yahoo! Groups Links


n4buq <n4buq@...>
 

I recently bought a couple of 561A's, primarily for the plugins and
to have a good supply of spare parts for my existing 561A. While the
plugins seem to work, neither of the "new" scopes work properly, and
I was wondering if someone might know by the symptoms what the
problem might be.

Both of them produce a rather loud ticking noise which coincides with
a flashing effect in the 6AS7 and the OG3 tubes. Both 6AS7's also
glow a fairly bright violet color and I'm not sure if that is
normal. On one of the scopes, when the flashover occurs and I have
the calibrator hooked up to the input, I get a blur of random traces
on the screen.

I had noticed before that my "good" 561A sometimes would tick like
this, but hadn't traced it to the source.

Is this an indication of power supply problems? I suspect filter
caps simply because of their age, but not sure if this is it. I
haven't bought a schematic yet, so it's difficult for me to do much
analysis at this point. I was just figuring this might be a pretty
common symptom and someone might be able to tell me some things to
check.

Also, still looking for a source for the power cords. Are these now
unobtanium?

Thanks!

Barry - N4BUQ