Tek 545A Scope


David Kuhn
 

I recently acquired a 545A. It was quite a mess. I published some
pictures of it on the OLD Tek Scope forum on Facebook.

The Type D plugin was really a mess. I had to replace literally every
small wire! Every small wire. The amplifier chassis is mounted on
deteriorated rubber balloon mounts which, maybe in shipping, caused every
small wire to break off. With the help of the schematics from TekWiki, I
rewired that module this morning and it actually works now!

Anyway, the fan was seized, but that was easily fixed. What was not is the
rubber mounts are all crumbled and the blades very much bent. I used WD40
and after spinning it with 120 volts applied it can spin quite well (except
for the bent blades). What do people usually do to remount these fans? I
could just use screws and maybe some soft rubber washers, but I do not have
rubber stand-offs. Can you get them?

Without the fan installed. It now turns on and seems to work. The
calibrator switch took a shot of Deox 5 to get the calibrator working.
Monitoring with another scope, it is spot on with its amplitude output.

The Type D module, even with my re-wiring is damn close to spot on.

The trace is bright and very sharp. Very good CRT.

And then it blooms, starts to dim and goes away. Sounds like a high
voltage transformer?

With a floor fan on the bench pointed into the scope (it really puts out a
lot of air), it ran for over an hour before I shut it down.

What are the odds that fixing the main fan, or installing a replacement,
will keep it running? Without the fan, I am guessing it went maybe 5
minutes, maybe a little more, before blooming and losing the trace.

Also, I replaced zero caps so far. Boy does it have a huge amount of large
can caps. Do you guys typically replace them all or only as needed? The
trace has ZERO ripple or pulsations on it. The Square wave was fairly
perfect,

I had fun with this repair, so far, but find that those 4 divisions are
going to be very limiting for usage. I really thought this was a 547 when
I grabbed it all excited and then "Waaa Waaa waaaa" when I realized the
four divisions. LOL I'll trade this for a 547 with a good hiv xfrmr - LOL
(yea right).

Anyway, I hope that someone(s) can give me some directions to my questions
above. I've been lurking a long time for a 500 series scope to fix up; I
finally have one.


Dave Wise
 

Send me your address off-list and I’ll mail you three new rubber mounts. I bought a lifetime supply from McMaster-Carr years ago.

Typically the electrolytic caps in 500-series mainframes are fine, even 70 years after manufacture. You’ve already weathered the main risk, which is blowing the fuse on the first turn-on after years of idleness.
Most of the other caps in A-suffix instruments are ceramic or plastic film and will outlive you.

Late 500-series instruments, notoriously the 547, have lossy epoxy impregnant in the HV transformer. The only cure is a rewind.
Your 545A predates that, your transformer contains beeswax. These can absorb water if stored in a humid location, but a few hours bake should dry it out like new.

One other thing to try. C808, the 1nF cap that resonates the HV primary, is probably a hybrid paper-plastic dielectric. The paper side can go lossy. Replace it and see. Any polyester or polypropylene cap will do. Sometimes the 500pF “doorknob” ceramic caps in the tripler will fail, but that’s usually a dead short, not what you’re seeing.

HTH,
Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David Kuhn via groups.io
Sent: Tuesday, June 08, 2021 1:26 PM
To: TekScopes@groups.io
Subject: [TekScopes] Tek 545A Scope

I recently acquired a 545A. It was quite a mess. I published some
pictures of it on the OLD Tek Scope forum on Facebook.

The Type D plugin was really a mess. I had to replace literally every
small wire! Every small wire. The amplifier chassis is mounted on
deteriorated rubber balloon mounts which, maybe in shipping, caused every
small wire to break off. With the help of the schematics from TekWiki, I
rewired that module this morning and it actually works now!

Anyway, the fan was seized, but that was easily fixed. What was not is the
rubber mounts are all crumbled and the blades very much bent. I used WD40
and after spinning it with 120 volts applied it can spin quite well (except
for the bent blades). What do people usually do to remount these fans? I
could just use screws and maybe some soft rubber washers, but I do not have
rubber stand-offs. Can you get them?

Without the fan installed. It now turns on and seems to work. The
calibrator switch took a shot of Deox 5 to get the calibrator working.
Monitoring with another scope, it is spot on with its amplitude output.

The Type D module, even with my re-wiring is damn close to spot on.

The trace is bright and very sharp. Very good CRT.

And then it blooms, starts to dim and goes away. Sounds like a high
voltage transformer?

With a floor fan on the bench pointed into the scope (it really puts out a
lot of air), it ran for over an hour before I shut it down.

What are the odds that fixing the main fan, or installing a replacement,
will keep it running? Without the fan, I am guessing it went maybe 5
minutes, maybe a little more, before blooming and losing the trace.

Also, I replaced zero caps so far. Boy does it have a huge amount of large
can caps. Do you guys typically replace them all or only as needed? The
trace has ZERO ripple or pulsations on it. The Square wave was fairly
perfect,

I had fun with this repair, so far, but find that those 4 divisions are
going to be very limiting for usage. I really thought this was a 547 when
I grabbed it all excited and then "Waaa Waaa waaaa" when I realized the
four divisions. LOL I'll trade this for a 547 with a good hiv xfrmr - LOL
(yea right).

Anyway, I hope that someone(s) can give me some directions to my questions
above. I've been lurking a long time for a 500 series scope to fix up; I
finally have one.


David Kuhn
 

Thank you. I just sent you an email with my UPS account information.
Don't use your own money to ship. If you want something for them, I can
send money via PayPal.

Dave

On Tue, Jun 8, 2021 at 6:05 PM Dave Wise <david_wise@phoenix.com> wrote:

Send me your address off-list and I’ll mail you three new rubber mounts.
I bought a lifetime supply from McMaster-Carr years ago.

Typically the electrolytic caps in 500-series mainframes are fine, even 70
years after manufacture. You’ve already weathered the main risk, which is
blowing the fuse on the first turn-on after years of idleness.
Most of the other caps in A-suffix instruments are ceramic or plastic film
and will outlive you.

Late 500-series instruments, notoriously the 547, have lossy epoxy
impregnant in the HV transformer. The only cure is a rewind.
Your 545A predates that, your transformer contains beeswax. These can
absorb water if stored in a humid location, but a few hours bake should dry
it out like new.

One other thing to try. C808, the 1nF cap that resonates the HV primary,
is probably a hybrid paper-plastic dielectric. The paper side can go
lossy. Replace it and see. Any polyester or polypropylene cap will do.
Sometimes the 500pF “doorknob” ceramic caps in the tripler will fail, but
that’s usually a dead short, not what you’re seeing.

HTH,
Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David
Kuhn via groups.io
Sent: Tuesday, June 08, 2021 1:26 PM
To: TekScopes@groups.io
Subject: [TekScopes] Tek 545A Scope

I recently acquired a 545A. It was quite a mess. I published some
pictures of it on the OLD Tek Scope forum on Facebook.

The Type D plugin was really a mess. I had to replace literally every
small wire! Every small wire. The amplifier chassis is mounted on
deteriorated rubber balloon mounts which, maybe in shipping, caused every
small wire to break off. With the help of the schematics from TekWiki, I
rewired that module this morning and it actually works now!

Anyway, the fan was seized, but that was easily fixed. What was not is the
rubber mounts are all crumbled and the blades very much bent. I used WD40
and after spinning it with 120 volts applied it can spin quite well (except
for the bent blades). What do people usually do to remount these fans? I
could just use screws and maybe some soft rubber washers, but I do not have
rubber stand-offs. Can you get them?

Without the fan installed. It now turns on and seems to work. The
calibrator switch took a shot of Deox 5 to get the calibrator working.
Monitoring with another scope, it is spot on with its amplitude output.

The Type D module, even with my re-wiring is damn close to spot on.

The trace is bright and very sharp. Very good CRT.

And then it blooms, starts to dim and goes away. Sounds like a high
voltage transformer?

With a floor fan on the bench pointed into the scope (it really puts out a
lot of air), it ran for over an hour before I shut it down.

What are the odds that fixing the main fan, or installing a replacement,
will keep it running? Without the fan, I am guessing it went maybe 5
minutes, maybe a little more, before blooming and losing the trace.

Also, I replaced zero caps so far. Boy does it have a huge amount of large
can caps. Do you guys typically replace them all or only as needed? The
trace has ZERO ripple or pulsations on it. The Square wave was fairly
perfect,

I had fun with this repair, so far, but find that those 4 divisions are
going to be very limiting for usage. I really thought this was a 547 when
I grabbed it all excited and then "Waaa Waaa waaaa" when I realized the
four divisions. LOL I'll trade this for a 547 with a good hiv xfrmr - LOL
(yea right).

Anyway, I hope that someone(s) can give me some directions to my questions
above. I've been lurking a long time for a 500 series scope to fix up; I
finally have one.









David Kuhn
 

" One other thing to try. C808, the 1nF cap that resonates the HV primary,
is probably a hybrid paper-plastic dielectric. The paper side can go
lossy. Replace it and see. Any polyester or polypropylene cap will do.
Sometimes the 500pF “doorknob” ceramic caps in the tripler will fail, but
that’s usually a dead short, not what you’re seeing."

O am printing this out and will investigate this in the days that come;
thank you.

Dave

On Tue, Jun 8, 2021 at 6:05 PM Dave Wise <david_wise@phoenix.com> wrote:

Send me your address off-list and I’ll mail you three new rubber mounts.
I bought a lifetime supply from McMaster-Carr years ago.

Typically the electrolytic caps in 500-series mainframes are fine, even 70
years after manufacture. You’ve already weathered the main risk, which is
blowing the fuse on the first turn-on after years of idleness.
Most of the other caps in A-suffix instruments are ceramic or plastic film
and will outlive you.

Late 500-series instruments, notoriously the 547, have lossy epoxy
impregnant in the HV transformer. The only cure is a rewind.
Your 545A predates that, your transformer contains beeswax. These can
absorb water if stored in a humid location, but a few hours bake should dry
it out like new.

One other thing to try. C808, the 1nF cap that resonates the HV primary,
is probably a hybrid paper-plastic dielectric. The paper side can go
lossy. Replace it and see. Any polyester or polypropylene cap will do.
Sometimes the 500pF “doorknob” ceramic caps in the tripler will fail, but
that’s usually a dead short, not what you’re seeing.

HTH,
Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David
Kuhn via groups.io
Sent: Tuesday, June 08, 2021 1:26 PM
To: TekScopes@groups.io
Subject: [TekScopes] Tek 545A Scope

I recently acquired a 545A. It was quite a mess. I published some
pictures of it on the OLD Tek Scope forum on Facebook.

The Type D plugin was really a mess. I had to replace literally every
small wire! Every small wire. The amplifier chassis is mounted on
deteriorated rubber balloon mounts which, maybe in shipping, caused every
small wire to break off. With the help of the schematics from TekWiki, I
rewired that module this morning and it actually works now!

Anyway, the fan was seized, but that was easily fixed. What was not is the
rubber mounts are all crumbled and the blades very much bent. I used WD40
and after spinning it with 120 volts applied it can spin quite well (except
for the bent blades). What do people usually do to remount these fans? I
could just use screws and maybe some soft rubber washers, but I do not have
rubber stand-offs. Can you get them?

Without the fan installed. It now turns on and seems to work. The
calibrator switch took a shot of Deox 5 to get the calibrator working.
Monitoring with another scope, it is spot on with its amplitude output.

The Type D module, even with my re-wiring is damn close to spot on.

The trace is bright and very sharp. Very good CRT.

And then it blooms, starts to dim and goes away. Sounds like a high
voltage transformer?

With a floor fan on the bench pointed into the scope (it really puts out a
lot of air), it ran for over an hour before I shut it down.

What are the odds that fixing the main fan, or installing a replacement,
will keep it running? Without the fan, I am guessing it went maybe 5
minutes, maybe a little more, before blooming and losing the trace.

Also, I replaced zero caps so far. Boy does it have a huge amount of large
can caps. Do you guys typically replace them all or only as needed? The
trace has ZERO ripple or pulsations on it. The Square wave was fairly
perfect,

I had fun with this repair, so far, but find that those 4 divisions are
going to be very limiting for usage. I really thought this was a 547 when
I grabbed it all excited and then "Waaa Waaa waaaa" when I realized the
four divisions. LOL I'll trade this for a 547 with a good hiv xfrmr - LOL
(yea right).

Anyway, I hope that someone(s) can give me some directions to my questions
above. I've been lurking a long time for a 500 series scope to fix up; I
finally have one.









Jonathan Pyle
 

When I restored my 1963 rackmount 545A (RM45A) I replaced all the electrolytic and "PTM" (paper tubular molded) capacitors. Before replacing the capacitors, I had ripple and the supply rails were far off, and replacing the capacitors cured all that. I don't know whether the capacitors in the parts list that are marked as "PTM" were actually paper in my instrument; maybe they were actually plastic and didn't need replacement, but I didn't want to take any chances.

My long-shot, non-expert, probably bad ideas about the disappearing trace: 1) High voltages in this part of the circuit go directly to the potentiometers for intensity, focus, and astigmatism, so maybe scratchy pots could cause the trace to go away (another deoxit fix?); 2) If V814A or V814B stopped working after heating up to a certain point, maybe that would explain the fact that the trace disappears after a while. To test that, you could temporarily swap them out with 12AU7s from elsewhere in the instrument to see if the problem goes away. (V800 is also important but it's the only 6AU5 in the instrument so that debugging technique is not available.) I don't have any problems with the trace blooming and disappearing but I often see vertical instability that seems to be related to thermal changes. It will be working fine and then the trace will wobble vertically or even shoot off the screen. Putting the scope back in its case seems to prevent this; I assume it works best if the temperature is warmer and the airflow is more consistent. So it is conceivable to me that if you got the regular fan working and closed up the instrument, maybe it would work more reliably.


Roy Morgan
 

The Right Stuff

On Jun 9, 2021, at 11:58 PM, Jonathan Pyle <jhpyle@gmail.com> wrote:

When I restored my 1963 rackmount 545A (RM45A)
. . .
maybe scratchy pots could cause the trace to go away (another deoxit fix?);
I think not.
De-Oxit is right for metal to metal contact switches. It *may* harm variable resistor controls.
Caig "Fader Lube" IS the right stuff (formerly called MCL-moving contact lubricant).

Accept no substitutes.

Roy


Dave Wise
 

David Kuhn, I read that your Type D plugin has bad shock mounts. I have found a source for new rubber cushions indistinguishable from new originals. Notes below:

ACTION: Buy "DJI ZH3-3D Damping Rubber Set (Part 42)", $5.19 at ebay.
This is four bags of four each of four different type isolators.
The ball shaped ones (gray "A40" and white "30")
are *perfect* drop-in replacements.

FIXED!

NOTE: "DJI Z15 Zenmuse Spare Part 7 Damping Rubber for gimbal gyroscope"
at aliexpress is probably okay too. 6 parts $8.
"DJI Zenmuse H4-3D Part 3 Damping Rubber" looks identical to H3-3D part 42.
"DJI Zenmuse H3 2d Damping Rubber Part 15" at 3rdrockhobbies is
twelve cushions (3 kinds, all ball type) for $5.
These look exactly like Barry Controls 275-N1 which are ~$10 each.
Parts for Phantom series are no good.
I don't think there ever was an H2.


David Kuhn
 

Thank you!

On Fri, Jul 30, 2021 at 12:23 PM Dave Wise <david_wise@phoenix.com> wrote:

David Kuhn, I read that your Type D plugin has bad shock mounts. I have
found a source for new rubber cushions indistinguishable from new
originals. Notes below:

ACTION: Buy "DJI ZH3-3D Damping Rubber Set (Part 42)", $5.19 at ebay.
This is four bags of four each of four different type isolators.
The ball shaped ones (gray "A40" and white "30")
are *perfect* drop-in replacements.

FIXED!

NOTE: "DJI Z15 Zenmuse Spare Part 7 Damping Rubber for gimbal gyroscope"
at aliexpress is probably okay too. 6 parts $8.
"DJI Zenmuse H4-3D Part 3 Damping Rubber" looks identical to H3-3D
part 42.
"DJI Zenmuse H3 2d Damping Rubber Part 15" at 3rdrockhobbies is
twelve cushions (3 kinds, all ball type) for $5.
These look exactly like Barry Controls 275-N1 which are ~$10 each.
Parts for Phantom series are no good.
I don't think there ever was an H2.