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 Post subject: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 1:15 am 
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I was trying to remove this capacitor can on my A730E, but two twist tabs are heavily soldered in place. I've wicked and sucked away a few grams of solder (ok - a half a gram :lol: ) but can't seem to break the two soldered tabs loose. Access to the can from the top is tight, no means I can see of getting to the rim due to the speaker coil on one side.
Attachment:
Z A7305E TOP.png
Z A7305E TOP.png [ 137.4 KiB | Viewed 504 times ]

I am happy putting the new electrolytics under the chassis after failing to unsolder these tabs. I plan to leave the can in place and bend the three twister tabs flat and cut off the square and triangle capacitor leads.
I see some tar bubbles which the heat of the my heavy duty hakko 455 caused to flow a bit more. Is that tar going to be a problem in the future?


Attachments:
A730E CAN AFTER.gif
A730E CAN AFTER.gif [ 154.13 KiB | Viewed 504 times ]
A730E CAN BEFORE.gif
A730E CAN BEFORE.gif [ 157.74 KiB | Viewed 502 times ]

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 1:22 am 
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Location: Scranton, PA 18505
I’m not familiar with your model soldering iron but you’ll need 400 watts or more. Make sure the tip is clean and tinned. Also after your gun is up to temperature trying adding a little flux to the joint when you are heating it and then get your solderwick in there. They can be very stubborn at times. Good luck


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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 1:33 am 
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250 watt iron will work fine, however, the iron must have a large copper bolt that stores the heat and can deliver it to the chassis.

Borrow such an iron or do the Yard sale thing. These irons are not cheap new...

I have an American Beauty and a Vulcan, both massive copper bolts but neither over 300 watts.

Alternative?

Leave the can in place, install a tie strip nut bolt for new caps and radio connections, or reroute connections and find alternate terminals on the chassis for the filters. Never had a problem on an atypical AA5/5 doing such a re-locating...

YMMV

Chas


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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 1:57 am 
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Right, you'll do more damage than good sometimes, trying to remove a can like that. Someone persistant could bore in from below with a Dremel tool, but I wouldn't try it.

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 2:28 am 
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I just leave those cans in place, disconnecting the wires to the central terminals completely, and using the outer terminals as the ground for the replacements.

This is important if the can is insulated from the chassis, as it is in many radios. Using the outer tabs for grounding the replacements ensures they are connected properly in the circuit.

That does not apply in this case.

- Leigh

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 2:38 am 
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I restuff a NOS can cap of similar size, and don't worry about the old can or it's mounts. One dremel tool action, and the old one is off, the newly restuffed one in, and tabs twisted for testing, only resoldered once the unit works.

As to restuffing the NOS can, I have my way, which by no means is the only way to restuff. Plenty of great ideas in that area - some are downright brilliant!

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 2:55 am 
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Are you using your solder wick correctly.
Your before and after photos look like you are just moving the molten solder around. Often I just use the outer braid of some TV coax.

Greg.


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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 2:57 am 
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Chas wrote:
250 watt iron will work fine, however, the iron must have a large copper bolt that stores the heat and can deliver it to the chassis.

Borrow such an iron or do the Yard sale thing. These irons are not cheap new...

I have an American Beauty and a Vulcan, both massive copper bolts but neither over 300 watts.

Alternative?

Leave the can in place, install a tie strip nut bolt for new caps and radio connections, or reroute connections and find alternate terminals on the chassis for the filters. Never had a problem on an atypical AA5/5 doing such a re-locating...

YMMV

Chas


You can use a solder gun also, replace the element with a short piece of #12 copper wire. I use mine for all chassis soldering now. You can also use a larger piece of copper wire to use it to cut styrofoam :)

jason


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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 3:17 am 
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Location: Mountains of Mourne. Ireland.
22-1757 is a dual section capacitor, I don't have your schematic!
Image

Greg.


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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 4:08 am 
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It's definitely not the best way looks wise, but the aluminum on these cans is soft, and they can be cut (or chiseled) off just above the base relatively easily.


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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 5:06 am 
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Thanks everyone for the info! I'm going to add the two E-caps under and grounded to chassis using terminal strips.

Regarding use of the wick - towards the end of this session, I did use some flux with the wick and picked up a good deal of solder.
The two factory applied beads under the components tacked on these cans were bigger than I thought, when I hit them with the hot iron the first time with the solder sucker at the ready, the solder seemed to multiply rapidly, no way to keep up. So, I tried to mop up as best I could but I created a mess. Now I'm sure there is solder in the twist joints I'll never get out. BTW, that HAKKO is 45 watts, but it is hotter than my smaller iron with a bigger chisel tip at 540 C. So, the can stays, I won't worry about the tar, just disconnect the A and B terminals and use the tabs for B-.

In the photo above A730E CAN BEFORE there is a red/brown ceramic disc cap running from C1 B to twist tab/chassis. It is marked with 01. It shattered when I tried to disconnect it. I'm going to replace it with a .01uF 1000V film cap from Mouser. I bring this up as I think it is the same as C34 on the SAMS data sheet from the radiomuseum, but it isn't called out on the pictorial components diagram for capacitors. On the schematic it would be C34, I believe but C34 doesn't correspond to the picture exactly.

The rest of the replacement seems straight forward, some great examples on this site using search. I didn't see anything about the cans being soldered in place however.
Cheers,
John


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A730E Diode.PNG
A730E Diode.PNG [ 84.57 KiB | Viewed 426 times ]

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Fri 13, 2018 8:58 pm 
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Leigh wrote:
I just leave those cans in place, disconnecting the wires to the central terminals completely, and using the outer terminals as the ground for the replacements.

This is important if the can is insulated from the chassis, as it is in many radios. Using the outer tabs for grounding the replacements ensures they are connected properly in the circuit.

That does not apply in this case.

- Leigh

amen

I just looked at one of these radios for a friend. it was loaded with silver migration in the IFTs in both AM and FM.

it was so bad that it wasn't only the frying egg syndrome. it was pop corn, frying eggs, sizzling bacon, and boiling potatoes all in one to the point that it killed reception.

no, just no...next radio...

steve

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Sat 14, 2018 2:16 am 
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sergneri wrote:
The rest of the replacement seems straight forward, some great examples on this site using search. I didn't see anything about the cans being soldered in place however.
Cheers,
John

Regardless of temperature rating your iron is approx 125-150 watts shy of being useful for such task. The surrounding metal sucks up all the heat, need large tip and big wattage to keep the heat coming.

Me I break out Big Bertha, yet to meet a can she couldn't heat. A four tab, four lugger is a piece of cake.

Image

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Sat 14, 2018 3:02 am 
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35Z5 wrote:
sergneri wrote:
The rest of the replacement seems straight forward, some great examples on this site using search. I didn't see anything about the cans being soldered in place however.
Cheers,
John

Regardless of temperature rating your iron is approx 125-150 watts shy of being useful for such task. The surrounding metal sucks up all the heat, need large tip and big wattage to keep the heat coming.

Me I break out Big Bertha, yet to meet a can she couldn't heat. A four tab, four lugger is a piece of cake.

Image

Hi sergneri,
Nothing at all wrong with your plan to install new caps beneath the chassis. Nor to abandon the idea of re-stuffing the original can cap. But your failure to be able to de-solder and remove this twist-lock can cap should not be the basis of your decision on this. And besides, you may have need to remove similar twist-lock can caps on future projects.

+1 to comments above by Tom ("35Z5"). You need a hotter soldering iron, such as he mentions. But regardless of its temperature, its tip must be clean to promote proper heat transfer. When soldering or de-soldering cleanliness is everything! A hot clean soldering iron, combined with use of de-soldering braid and/or a solder sucker, should permit easy removal of any twist-lock can capacitor.

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Sat 14, 2018 5:15 am 
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Dutch Rabbit wrote:
amen

I just looked at one of these radios for a friend. it was loaded with silver migration in the IFTs in both AM and FM.

it was so bad that it wasn't only the frying egg syndrome. it was pop corn, frying eggs, sizzling bacon, and boiling potatoes all in one to the point that it killed reception.

no, just no...next radio...

steve


Steve - how did you know those IFTs had that problem? Is it something these A730E's have or did the radio exhibit some specific problem (like the bad static/full plate breakfast with pop corn?) This project was to simply recap and redo the selenium rec. :?

Thx - John

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Sat 14, 2018 5:25 am 
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Poston Drake wrote:
sergneri wrote:
The rest of the replacement seems straight forward, some great examples on this site using search. I didn't see anything about the cans being soldered in place however.
Cheers,
John

Hi sergneri,
Nothing at all wrong with your plan to install new caps beneath the chassis. Nor to abandon the idea of re-stuffing the original can cap. But your failure to be able to de-solder and remove this twist-lock can cap should not be the basis of your decision on this. And besides, you may have need to remove similar twist-lock can caps on future projects.

+1 to comments above by Tom ("35Z5"). You need a hotter soldering iron, such as he mentions. But regardless of its temperature, its tip must be clean to promote proper heat transfer. When soldering or de-soldering cleanliness is everything! A hot clean soldering iron, combined with use of de-soldering braid and/or a solder sucker, should permit easy removal of any twist-lock can capacitor.


Yep, heat is next to cleanliness and I keep my tip bright and shinny! However good I think I am at soldering, de-soldering 1960's Zenith silver is a new twist for me. I'm thinking a bigger braid, as one suggested above using coax, for example, is better than the using up the little spool of braid I have. I think that was meant for SMD, not for jobs like this. Your comments make me want to try it again but I was going to get out the Dremmel and file off what chunks I can before cleaning up one more time.
Cheers,
John

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Sat 14, 2018 6:04 am 
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Location: Powell River BC Canada
In shops in the past, when more heat was needed, the techs in the next
cubicle came over, with their irons. and several heated what was worked
on.

On the Weller D440 or 550 you could shine the tip all you wanted
but the heat came from reefing on tip nuts hard.

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Sat 14, 2018 2:55 pm 
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radiotechnician wrote:
In shops in the past, when more heat was needed, the techs in the next
cubicle came over, with their irons. and several heated what was worked
on.

On the Weller D440 or 550 you could shine the tip all you wanted
but the heat came from reefing on tip nuts hard.

Agreed, if tip isn't snug, even the big gun is a effort in futility.

Before I adopted Bertha($15 antique/junk shop find), I'd have a 8200 in each hand.
At a 280 watts combined, they'd do the job but are somewhat clumsy.

With solder clenched in my teeth, I've soldered with a pair.

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Sat 14, 2018 5:42 pm 
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I have a few soldering coppers. Those could be heated with a propane
torch, then used. If I ever find a gasoline blowtorch....

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 Post subject: Re: CAP CAN Twist Tabs Soldered On
PostPosted: Jul Sat 14, 2018 8:39 pm 
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For the blowtorch, you put in Naptha, white gas. You knew this, just forgot. :lol:
Yes, I remember the torch roaring away on the mechanic's bench with an 'iron' balanced on top.
Now we know it was copper, not 'iron'.

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