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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



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






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


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







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.


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










Rich Frahm
 

I'll gladly share my stl files, but there are many different sizes of cans so my files would only be useful if you happen to be working on a can that's the same size.

https://drive.google.com/file/d/1PkOBNd7AQ0NAYyy0vTUZcMlEWXXGoqYT/view?usp=sharing

Rich


David Holland
 

Thank you sir, I think I can scale them as necessary.


David

On Mon, Aug 10, 2020 at 12:05 PM Rich Frahm <criageek@...> wrote:

I'll gladly share my stl files, but there are many different sizes of cans
so my files would only be useful if you happen to be working on a can
that's the same size.


https://drive.google.com/file/d/1PkOBNd7AQ0NAYyy0vTUZcMlEWXXGoqYT/view?usp=sharing

Rich