Date   

Re: Removing Sprague/Mallory cans - was Re: [TekScopes] 465M: No trace, No +5V, No +95V

David Holland
 

Rich's technique is pretty much what I do, though - obviously - better
documented. I do like his 3D printed threads, I'll have to try that
next time I need to re-stuff. Perhaps he has a pointer to some STLs? :-)

My concerns with sawing in place - particularly on a scope - would be
aluminium debris getting everywhere (and shorting something important out),
and/or the hacksaw wacking up against other things that won't appreciate
it.

Perhaps some sort of oscillating tool - but that won't take care of the
debris problem.

<shrug> I think I'll stick to removing them. After that replacement
becomes a "find an adapter", or a "restuff" problem. I don't disagree
removal is a problem, particularly without good desoldering equipment.

David

On Mon, Aug 10, 2020 at 10:33 AM <toby@...> wrote:

On 2020-08-10 9:21 a.m., David Holland wrote:
Once you have them out, a tubing cutter, and some aluminium tape will
work
wonders.

Thanks, I didn't realise you'd already desoldered them. That was the
tedious bit for me! Indeed I can't imagine how you could cut the can in
place -- forgive me for being slow. Yes, a hacksaw blade should be fine.

In my case, replacing the missing can connections was easy so I didn't
want to replace the can base once they were out.

--Toby

https://www.amazon.com/RIDGID-40617-Quarters-Tubing-Cutter/dp/B001P307PO?ref_=fsclp_pl_dp_3
(for example)

Otherwise, Hacksaw blade, or Jewelers saw? (I'm afraid I usually remove,
so not much experience there... - I think I did the hacksaw blade route
once on a radio, but didn't like the results, so remove anymore...)

David


On Mon, Aug 10, 2020 at 8:35 AM <toby@...> wrote:

On 2020-08-09 10:56 p.m., DaveH52 wrote:
I had a similar problem with my 465M. One of the raw supplies was low.
I replaced all the can capacitors by cutting them off just above the fat
part so I could save all the connections, removed the old stuff inside
and
soldered new caps into the bases. The capacitor mounting tabs are
actually
part of the circuit. Start by making sure you have all the raw supplies.
There's a 2uf cap just to the left of the HV shield near the test point
that went leaky and killed the +95V..
Having recapped a 603 and 604 recently, I'm curious what tool you used
to cut them, and what physical access was required. In my case I had to
remove the cans entirely, which was a challenging desoldering job
because there is only the bare minimum of clearance and access to the
pins.

Would like to see a photo series if you do this again - would probably
help a lot of people faced with the same task.

--Toby










Re: Removing Sprague/Mallory cans - was Re: [TekScopes] 465M: No trace, No +5V, No +95V

pdxareaid
 

Years ago I similarly opened the cans with a hacksaw after i desoldered from the board, though i just used a little flex glue to reassemble the base and cans.
that is a very nice 3d printer idea.
i chose to drill ventilation holes near the base of the can and at the top of the can for convection cooling of the stuffed caps.
i also dealt with C582 cap literally leaking electrolyte onto the board for the +95. C582 is a very common problem in the 465M.


Re: TM500 Plug-in Extention

Colin Herbert
 

My TM 500 extenders were supplied as a kit from Dan Meeks (though I doubt he has any left) and the ribbon-cable is ~87 cm long. I can't say that I've seen any problems with oscillation of the pass-transistors in the mainframe, but wouldn't they need to be connected to some circuitry in a plug-in at the other end of the extender? I can't see how an unpowered transistor can oscillate.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 10 August 2020 15:28
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM500 Plug-in Extention

Putting one small bead didn’t help...


Re: Removing Sprague/Mallory cans - was Re: [TekScopes] 465M: No trace, No +5V, No +95V

toby@...
 

On 2020-08-10 9:21 a.m., David Holland wrote:
Once you have them out, a tubing cutter, and some aluminium tape will work
wonders.

Thanks, I didn't realise you'd already desoldered them. That was the
tedious bit for me! Indeed I can't imagine how you could cut the can in
place -- forgive me for being slow. Yes, a hacksaw blade should be fine.

In my case, replacing the missing can connections was easy so I didn't
want to replace the can base once they were out.

--Toby

https://www.amazon.com/RIDGID-40617-Quarters-Tubing-Cutter/dp/B001P307PO?ref_=fsclp_pl_dp_3
(for example)

Otherwise, Hacksaw blade, or Jewelers saw? (I'm afraid I usually remove,
so not much experience there... - I think I did the hacksaw blade route
once on a radio, but didn't like the results, so remove anymore...)

David


On Mon, Aug 10, 2020 at 8:35 AM <toby@...> wrote:

On 2020-08-09 10:56 p.m., DaveH52 wrote:
I had a similar problem with my 465M. One of the raw supplies was low.
I replaced all the can capacitors by cutting them off just above the fat
part so I could save all the connections, removed the old stuff inside and
soldered new caps into the bases. The capacitor mounting tabs are actually
part of the circuit. Start by making sure you have all the raw supplies.
There's a 2uf cap just to the left of the HV shield near the test point
that went leaky and killed the +95V..
Having recapped a 603 and 604 recently, I'm curious what tool you used
to cut them, and what physical access was required. In my case I had to
remove the cans entirely, which was a challenging desoldering job
because there is only the bare minimum of clearance and access to the pins.

Would like to see a photo series if you do this again - would probably
help a lot of people faced with the same task.

--Toby







Re: TM500 Plug-in Extention

Stephen
 

Putting one small bead didn’t help...


Re: Removing Sprague/Mallory cans - was Re: [TekScopes] 465M: No trace, No +5V, No +95V

Rich Frahm
 

I restore old radios and often restuff the electrolytic filter capacitors and even the paper capacitors. Check out my thread on the Philco Phorum: https://philcoradio.com/phorum/showthread.php?tid=16421

That was fairly early on in my restoration experience and other techniques have been developed since then. When space permits I've even used the 3D printer to print threads to glue inside the can to allow them to be easily opened again, as well as a band to cover the resulting seam in the can.

https://drive.google.com/file/d/14aW6jnnTu6xfWodXFF2P4m49xbBiiE1o/view?usp=sharing
https://drive.google.com/file/d/1qchOg0MupjmL1dZVLsK0rYCnFCFfe_pQ/view?usp=sharing

I picked up a cheap set of steak knives at a dollar store to cut the cans open. Use a hose clamp as a guide when cutting.

Rich


Re: 475 With a bowed display. . . .Ideas?

Chuck Harris
 

I don't think so, and here is why:

When the scope is exposed to a strong magnet,
the field lines extend in loops from N to S poles.
When those flux lines confront a magnetizable metal,
they are distorted and concentrated into that metal,
making for truly weird looking flux arrangements.

On screen, such magnetizations of the mumetal
shield, which really is the only magnetizable material
anywhere near the CRT will make beam deflections in
small areas. This typically shows up as a kink
somewhere on the screen, near one edge.

_____________

_____________

___________/\

____________/

A power supply regulation failure could cause a progressive
pinch of the screen width making a "keystone" shape.

-Chuck Harris

Keith wrote:

Just thinking out loud here - if a scope sat on a bench (or in storage) in one position for a long time near some relatively powerful fixed nearby magnetic field, (like a big permanent magnet loudspeaker assembly, etc.) I suppose it is possible for some nearby magnetic anomaly like that to gradually induce a very specific magnetism somewhere, leading to visible misalignment? Such an unwanted magnetic influence could produce a very specific distortion and it would seem reasonable for such an influence to be most obvious on traces out at the edges of the CRT.

Maybe you could try degaussing the shield around the CRT? You can borrow my degaussing tool if you want. Sometimes it is the simple stuff. PIA to remove the shield and separate from the CRT, but that is probably the safest way to do it. Of course you would first have to remove those steering magnets like someone mentioned, or the degaussing tool would ruin them. Of course this means even more fiddling, but hey...that’s why we do this hobby, right?

Also, maybe the shield has been damaged by some mishandling in the past? Tek says, and I quote

“CAUTION This Mumetal shield has been carefully annealed after fabrication. Any shock may destroy its magnetic shielding characteristics”

So obviously it is possible for them to go bonkers. Just a thought...

Cheers,
CBG




Re: Removing Sprague/Mallory cans - was Re: [TekScopes] 465M: No trace, No +5V, No +95V

David Holland
 

Once you have them out, a tubing cutter, and some aluminium tape will work
wonders.

https://www.amazon.com/RIDGID-40617-Quarters-Tubing-Cutter/dp/B001P307PO?ref_=fsclp_pl_dp_3
(for example)

Otherwise, Hacksaw blade, or Jewelers saw? (I'm afraid I usually remove,
so not much experience there... - I think I did the hacksaw blade route
once on a radio, but didn't like the results, so remove anymore...)

David

On Mon, Aug 10, 2020 at 8:35 AM <toby@...> wrote:

On 2020-08-09 10:56 p.m., DaveH52 wrote:
I had a similar problem with my 465M. One of the raw supplies was low.
I replaced all the can capacitors by cutting them off just above the fat
part so I could save all the connections, removed the old stuff inside and
soldered new caps into the bases. The capacitor mounting tabs are actually
part of the circuit. Start by making sure you have all the raw supplies.
There's a 2uf cap just to the left of the HV shield near the test point
that went leaky and killed the +95V..
Having recapped a 603 and 604 recently, I'm curious what tool you used
to cut them, and what physical access was required. In my case I had to
remove the cans entirely, which was a challenging desoldering job
because there is only the bare minimum of clearance and access to the pins.

Would like to see a photo series if you do this again - would probably
help a lot of people faced with the same task.

--Toby






Re: TM500 Plug-in Extention

Stephen
 

On Mon, Aug 10, 2020 at 02:03 AM, Andy Warner wrote:


A problem I have seen with both home brew and official Tek extenders is
that the pass transistors can oscillate. Since they are most often used for
regulated supplies, it tends to make the entire module under test misbehave
badly. I seem to remember reading somewhere that the linear regulator
circuits these transistors are used in are sometimes near the edge of the
working envelope. Adding 60cm of wire to each transistor lead can just tip
them over the edge.

After seeing this: http://philippe.demerliac.free.fr/Tek.htm,
I am planning to modify one of my jamma-based extenders to add pass
transistors and heatsink mounted right at the module connector, to see if
it improves things.
Will report back when I have some results to share with the list.

Others have mentioned using ferrite beads to tamp down the oscillations, I
think mostly in the context of when you replace the transistors in the
mainframe; but perhaps it would help on the long leads. I doubt it can hurt.
Interesting...
I think I have some larger beads laying around. I’m gonna put one on each end of the connector and see if it helps.
Will report back.

Thank you for the info Andy.


Re: TM500 Plug-in Extention

Andy Warner
 

A problem I have seen with both home brew and official Tek extenders is
that the pass transistors can oscillate. Since they are most often used for
regulated supplies, it tends to make the entire module under test misbehave
badly. I seem to remember reading somewhere that the linear regulator
circuits these transistors are used in are sometimes near the edge of the
working envelope. Adding 60cm of wire to each transistor lead can just tip
them over the edge.

After seeing this: http://philippe.demerliac.free.fr/Tek.htm,
I am planning to modify one of my jamma-based extenders to add pass
transistors and heatsink mounted right at the module connector, to see if
it improves things.
Will report back when I have some results to share with the list.

Others have mentioned using ferrite beads to tamp down the oscillations, I
think mostly in the context of when you replace the transistors in the
mainframe; but perhaps it would help on the long leads. I doubt it can hurt.

On Mon, Aug 10, 2020 at 06:56 Stephen <stephen.nabet@...> wrote:

I’ve finally found the time to make an extender using JAMMA connectors to
be able to troubleshoot my DC 503 and my SC 502

I’ve removed the bridge connections from 1-2 and 3-4, and wired all the
pins from 1-5 and 7-13.
Pretty straight forward process. I didn’t connect anything beyond pin
13. Pins 2-3-4-8-12 use only one wire As both sides are connected.

I’ve tried PS503 and it works fine, except that when inside the TM, I can
check the +/- 20VDC AND the +5VDC while my ground lead is connected to
either ones on the plugin. But not when connected via the extender.

However, no other plugin (AM502, DC503, FG503) is working besides the
PS503...
I’ve checked the voltages, and everything is exactly the same on the
extender as on the TM506 connector itself.
There’s also full continuity between both ands of the extender.

I understand that pin 14 to 28 are not used when it comes to just power
the plugins...

What am I doing wrong??



--
Andy


Removing Sprague/Mallory cans - was Re: [TekScopes] 465M: No trace, No +5V, No +95V

toby@...
 

On 2020-08-09 10:56 p.m., DaveH52 wrote:
I had a similar problem with my 465M. One of the raw supplies was low. I replaced all the can capacitors by cutting them off just above the fat part so I could save all the connections, removed the old stuff inside and soldered new caps into the bases. The capacitor mounting tabs are actually part of the circuit. Start by making sure you have all the raw supplies. There's a 2uf cap just to the left of the HV shield near the test point that went leaky and killed the +95V..
Having recapped a 603 and 604 recently, I'm curious what tool you used
to cut them, and what physical access was required. In my case I had to
remove the cans entirely, which was a challenging desoldering job
because there is only the bare minimum of clearance and access to the pins.

Would like to see a photo series if you do this again - would probably
help a lot of people faced with the same task.

--Toby



Re: 475 With a bowed display. . . .Ideas?

Keith
 

Just thinking out loud here - if a scope sat on a bench (or in storage) in one position for a long time near some relatively powerful fixed nearby magnetic field, (like a big permanent magnet loudspeaker assembly, etc.) I suppose it is possible for some nearby magnetic anomaly like that to gradually induce a very specific magnetism somewhere, leading to visible misalignment? Such an unwanted magnetic influence could produce a very specific distortion and it would seem reasonable for such an influence to be most obvious on traces out at the edges of the CRT.

Maybe you could try degaussing the shield around the CRT? You can borrow my degaussing tool if you want. Sometimes it is the simple stuff. PIA to remove the shield and separate from the CRT, but that is probably the safest way to do it. Of course you would first have to remove those steering magnets like someone mentioned, or the degaussing tool would ruin them. Of course this means even more fiddling, but hey...that’s why we do this hobby, right?

Also, maybe the shield has been damaged by some mishandling in the past? Tek says, and I quote

“CAUTION This Mumetal shield has been carefully annealed after fabrication. Any shock may destroy its magnetic shielding characteristics”

So obviously it is possible for them to go bonkers. Just a thought...

Cheers,
CBG


Re: DC503 repair (pwr supply and incorrect display)

SCMenasian
 

I don't see where anyone has answered your final question. The answer is NO unless you can guarantee that the Tri-state output will not be in the HIGH state at any time that any OC output is LOW.


TM500 Plug-in Extention

Stephen
 

I’ve finally found the time to make an extender using JAMMA connectors to be able to troubleshoot my DC 503 and my SC 502

I’ve removed the bridge connections from 1-2 and 3-4, and wired all the pins from 1-5 and 7-13.
Pretty straight forward process. I didn’t connect anything beyond pin 13. Pins 2-3-4-8-12 use only one wire As both sides are connected.

I’ve tried PS503 and it works fine, except that when inside the TM, I can check the +/- 20VDC AND the +5VDC while my ground lead is connected to either ones on the plugin. But not when connected via the extender.

However, no other plugin (AM502, DC503, FG503) is working besides the PS503...
I’ve checked the voltages, and everything is exactly the same on the extender as on the TM506 connector itself.
There’s also full continuity between both ands of the extender.

I understand that pin 14 to 28 are not used when it comes to just power the plugins...

What am I doing wrong??


Re: DC503 repair (pwr supply and incorrect display)

Ravi Moghe
 

Quad latch with w/tri state ut - there would be a control signal on one of the pins of this ic that will make the latch output float at "high" state, irrespective of the state of signal at input pins.

If you google for this type of ic you will tend to find many parts. Additional details that you will need to match for will be operating voltage, bias currents, pin compatibility, open collector output etc.

I could just think of these points at the moment. May share further if I remember anything else.

Warm Regards,


Re: 2432A Chan Delay adjustment

 

The max output of a pg506 in fast rise mode (which is what you want) is between 100mV and a bit over 1V peak to peak.

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Peter K via groups.io
Sent: 10 August 2020 11:22
To: TekScopes@groups.io
Subject: Re: [TekScopes] 2432A Chan Delay adjustment

Thanks for the guidance.
From Scope’s SM I read, that I have to connect CH1 and CH2 through a 10X attenuator to generator and set it output amplitude to MAX. In specs for the PG506 is written that max output signal is 100V.
That means, that the scope expects fast rise signal with amplitude 10V and unknown frequency.
I tried different ones from 1 kHz to 1 MHz with no luck.
I will keep use it that way until I find a suitable calibration device .
Regards,
Peter.


Re: 2432A Chan Delay adjustment

Peter K
 

Thanks for the guidance.
From Scope’s SM I read, that I have to connect CH1 and CH2 through a 10X attenuator to generator and set it output amplitude to MAX. In specs for the PG506 is written that max output signal is 100V.
That means, that the scope expects fast rise signal with amplitude 10V and unknown frequency.
I tried different ones from 1 kHz to 1 MHz with no luck.
I will keep use it that way until I find a suitable calibration device .
Regards,
Peter.


Re: 7834 Missing Trace

Roger Evans
 

Thanks for doing all those measurements, if my understanding of U225 is correct (the manual doesn't describe its internals) it is something called a 'Gilbert Cell', which functions as a current multiplier. So if one current input is steady and the other is the signal then the steady current controls the gain of the cell for the signal input. You can also change the polarity of the steady current and make the amplifier effectively become an inverting amplifier. Being current driven, its inputs are always close to zero volts and I am not sure how significant are the small differences that you see. If you can find R551 on schematic <5> you can try adjusting it to get the +9V back to its nominal value and see how much the calibration changes. The -9V is derived from the +9V via an inverting op-amp and has its own adjustment, R570. Adjust +9V before testing the -9V.

In order to get the 7A12 working more nearly to its spec you can use the front panel gain adjustments to try and get the two channels somewhere near their nominal value. If you can borrow a second vertical plugin that would help enormously in being confident that the errors are in the 7A12 and not the mainframe.

Any progress in removing the 7A12 from the mainframe?

Regards,

Roger


Re: 475 With a bowed display. . . .Ideas?

Steph L
 

Thanks Michael for added detail and photos.

Process elimination; - I'd be inclined to swap Y output leads at point of connection to tube and try make sense of result.

Also, re your screen shot 475-trace-bent-6.jpeg, in terms of geometry, the image appears to be trapezoid shape. That is, the distance from left to right across the top of the pulses is shorter than across the base line, for the same number of pulses. This is a good clue. Looking at the Horizontal (X) sawtooth linearity between blanking, might offer a reason.

Sorry if you have explained this earlier, but when the Vertical Shift is used to lower the trace, does the top (trapazoid) line width "expand" out such that when the tops of the signal pulses are across the bottom of the tube face, do they now match gratical exactly as they do in that photo?? If so, it reinforces point - the tube geometry is somehow trapezoidal instead of rectangular in a 10:8 ratio.

Steph Lancaster
Melbourne (Australia)


Re: Tektronix 2230

Saroj Pradhan
 

Hi satbeginner
Understood. After I am satisfied with my repair work I will connect those
wire directly to the FET.
Thanks
Saroj

On Sun, Aug 9, 2020, 8:14 PM <tekscopegroup@...> wrote:

On Tue, Aug 4, 2020 at 06:33 PM, Saroj Pradhan wrote:
Before, at the beginning when I started to repair 2230, I Googled many
thread and forum. Some body suggested to remove the molex connector that
goes to the FET for connection and solder the wire directly to the FET.
What might be the reason behind this?
That connector I understood is known to sometimes develop a bad or
intermittent contact which can upset or even interfere with the operation
of the prereg to the point of possibly causing a no start condition. The
effect is compounded due to the FET getting hot and transferring heat to
the pins and the connector contacts, and in turn to the nylon body as well.
Sometimes the nylon body of the connector even looks a bit "baked" a sure
sign that its overheating, most probably due to poor contacts and IR^2
losses on a high amp current path. Clipping off the connector and soldering
the wires directly to the FET pins restores/eliminates this potential
contact problem. Back then I did it not have to remove this connector on my
2213A, just made sure all contacts where clean and tight, but anyone's else
mileage may vary. As long as the legs of the FET and the contacts of the
connector look to be in good shape, and the nylon body is not deformed or
shows signs of overheating I think it would be ok to keep the connector as
it makes troubleshooting/replacing the FET much easier.