Recapping Radio Craftsmen SEP Amp

Thanks guys—I appreciate the info.

Looks like I'll need to get the Y1 safety capacitor because of the larger .02µF spec on the old cap: (from Dave Cantelon's article, linked above): "One limitation ceramic disc safety caps have is that the largest uF capacitance size available is 0.01 uF (which is sometimes lower than what is needed per the schematic). If you require Y2 safety capacitor that has a capacitance over 0.01uF you will need to use Y2 capacitor made of Poly Film."

While there is no .02µF value, there is a 275VAC/ .022µF value, so I'm assuming that will work ok and went ahead and ordered that.

I intend to work on this this weekend, so I'll post updates here. Thanks again!
 
That will work fine.
Also if you have the space, 2. .01s in parallel equal a .02
That value in this circuit isn't critical
 
There are all sorts of paths that lead you to the wrong parts. I like to think of them as spares and inventory (stock?).
Every once in a blue moon I have something I actually need.
Paraphrasing Dr John.
"I was in the right part but it must've the wrong time"
 
If you repair or build for any length of time you will end up with plenty of extra parts. Not a bad thing, most are cheap and tend to be used later in another project. A good portion of my extra parts are due to wrong parts ordered,over ordering, and changing course in mid stream.
 
Makes sense to me—I'm already ordering extras of everything "just in case". :D

Plus, it just doesn't seem right ordering 94¢ worth of parts and then paying $4.99 (or whatever) for shipping...
 
RECAPPING PART 1:

Ok so I swapped out the filter caps yesterday. I tried to be as organized and to work as cleanly as I could, trying to make strong mechanical connections and not relying solely on the solder. I also ended up adding shrink tubing to most of the existing or new leads that I had to de-solder/re-solder. It's not the absolute tidiest work I've ever seen, but I'm ok with what I did, considering I've only soldered once before.

I'll try to finish up by next weekend (I have the multi-section cap, the Y-cap, and possibly the fuse to replace) but for now I have a few realizations to share:
  1. My fingers are giant gauze-covered sausages. I definitely have a newfound respect for surgeons.
  2. Either I'm going blind, or I definitely need more light (likely both...)
  3. Solder is absolutely amazing stuff, and it takes less than you'd think.
  4. Multiple vintage leads that are looped though and around again and soldered on top of each other are a total PITA to deal with.
  5. Cheap tools are a waste of money.

BEFORE:

Filter Caps_PRE 02.jpg


AFTER:

Filter Caps_POST 01.jpg

Filter Caps_POST_WHOLE 01.jpg



FUSE:
I also cut off the plastic tube connected to the mains input, and confirmed that it IS a fuse. Any one know how I could find out the fuse rating? And what would be the simplest way of installing a new one? (sorry for the crappy iPhone closeup...)

Filter Caps_POST_FUSE 01.jpg


Filter Caps_POST_FUSE 02.jpg
 

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Looks good so far. :thumbsup: Much cleaner than the original cap install. You are replacing the cap thats glued itself to the back of the chassis, right? As for the fuse, I wouldn't think anything bigger than a 2 amp slow blow fuse is needed. I don't see any extra holes for a fuse holder and drilling in a populated chassis can be sketchy. I would use an inline fuse holder. The twist open type with a lead on each end. Once you get the old fuse out, you should be able to read the amp rating to be sure.
 
Light is important. If you have reading glasses, use them. If you don't you might need them (or need them updated).
Cheap tools tend to be worthless but some decent ones can be had for not crazy money and they should last you a while (maybe a lifetime). If you want some suggestions, mention what you might be looking for.
For a relative novice, i think you did a nice job:thumbsup:
 
nj pheonix said:
Light is important. If you have reading glasses, use them. If you don't you might need them (or need them updated).
Cheap tools tend to be worthless but some decent ones can be had for not crazy money and they should last you a while (maybe a lifetime). If you want some suggestions, mention what you might be looking for.
For a relative novice, i think you did a nice job:thumbsup:
Click to expand...
Two tools I use a lot are an adustable magnifier with light and one of those cheap headsets with a set of magnifying lenses. Both are a huge help for people like us with sausage fingers. I think I payed around $10 for the headset at harbour frt. And wood chopsticks are really handy when working on high voltage tube amps. But as pheonix stated most tools you want to be better quality. Like a decent soldering station and solder sucker.
 
nj pheonix said:
Light is important. If you have reading glasses, use them. If you don't you might need them (or need them updated).
Cheap tools tend to be worthless but some decent ones can be had for not crazy money and they should last you a while (maybe a lifetime). If you want some suggestions, mention what you might be looking for.
For a relative novice, i think you did a nice job:thumbsup:
Click to expand...

Lavane said:
Looks good so far. :thumbsup: Much cleaner than the original cap install. You are replacing the cap thats glued itself to the back of the chassis, right? As for the fuse, I wouldn't think anything bigger than a 2 amp slow blow fuse is needed. I don't see any extra holes for a fuse holder and drilling in a populated chassis can be sketchy. I would use an inline fuse holder. The twist open type with a lead on each end. Once you get the old fuse out, you should be able to read the amp rating to be sure.
Click to expand...

Thanks guys, I appreciate it. I really enjoyed the process, and am just glad that I didn't F*** it all up, ha! I think I'm going to get a PCB and practice soldering just for fun—there's something enjoyable about trying to get it right. (of course, I watched this series on soldering from the 1980s and now realize all the mistakes I made lol...)

Yes, I'm planning on changing that wax cap for a line-to ground safety cap. I'll look into a 2 amp slow blow fuse—I definitely don't want to drill into the chassis, so I'll research an inline fuse holder and see what what I can rig up. (So the 2-amp fuse is def going to be ok?)

I went out and got a decent pair of Klein wire cutters and a smaller needle nose pliers. I think being more precise will help de-soldering/re-soldering the multiple leads that I'm encountering. (I used an exacto knife on some in some of the more difficult places, so I may look into tools that are more surgical—tweezers, forceps, etc.)

Lavane said:
Two tools I use a lot are an adustable magnifier with light and one of those cheap headsets with a set of magnifying lenses. Both are a huge help for people like us with sausage fingers. I think I payed around $10 for the headset at harbour frt. And wood chopsticks are really handy when working on high voltage tube amps. But as pheonix stated most tools you want to be better quality. Like a decent soldering station and solder sucker.
Click to expand...

I will definitely be on the lookout for an adjustable magnifier with light and also the headset—I think that will help a lot.

I got a solder sucker that seemed to be well-made, and I thought would work well. It *is* well-made, but unfortunately it's a little too small for my hand and kept getting blocked. Also the tip kept getting clogged (I pulled off the silicon tip, and ended up yanking out the solder plug so it worked out fine, but it was still a bit of a hassle...) Anyway it ended doing the job ok.

QUERY:
How should I remove the multi-section capacitor? I was planning on just clipping it off under the chassis close to the base and leaving all the soldered leads in place and then de-solder/resolder them one-by-one once the new can is in place, but I'm pretty sure I won't be able to get in there and not nick the existing wires. I was hoping to avoid desoldering everything first, but I may end up needing to do that...any suggestions?
 
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The can cap removal can be a bit of a bitch for the novice.
Not so much because its complicated , as that you tend to be undercooked (if that's a word).
The problem is the chassis acts as a heat sink, and even with a 140w soldering gun (a weller?)
You may not be able to get enough heat to the tabs of the can to remove solder or get it loose.
Your proposed approach is a good idea..You can cut the mounting tabs close to the chassis.
Sometimes once this is done , you can carefully heat what's left and rock the top side free.
I've seen and tried taking a seemed tool with a small grinding tip or a wire brush just to clear that last bit.
I wouldn't suggest trying to pick one up, but ideally there are some big irons (2-300w) which have enough heat to get those out pretty easily.
If you opt to grind, wear eye protection and try to watch where any big chunks of metal fly (if they do).
I'll see if i can come up with the better choices for Klein for you.
 
Oh on the leads of the cap.
Sometimes it's easier to just clip close in , restroom and reattach and solder. You can usually come up with the extra 1/4" of wire.
Take pictures , and take notes on what went where. . It tends to go back together more cleanly if it takes the same route it sat in for the last 50 years
 
I bought a cheap 300 watt gun for cap cans. Around $18? I use it just for cap cans. since I have no other use for one I didn't want to get a Weller. It works fast, so the gun isn't on for long. It's worked just fine for the five or so cans I've removed with it. If I were using one regularly I would spend much more for one. I tend to spend more on the tools and test equipment I use regularly. Like a good soldering station with adjustable heat and adjustment tools, those little sticks with various ends on them for adjusting pots, trimmers and such, worth the extra few bucks. If you at some point decide to slide further down the rabbit hole a good scope, signal generator and other equipment is going to cost ya some.
 
Last edited:
Hmm, seems like getting the can out of there might be trickier than I had planned...

How does this sound for a line of attack:
  1. Clip the leads close to the solder joint on each tab (retaining as much lead length as possible)
  2. With the space created around the can, clip each tab close the chassis
  3. Pull out the can
  4. Place the new can in the space, twist lock it in place, and then loop and re-solder all of the leads back in (unless my Weller 40 watt solder iron doesn't have enough power to do that?)
 
It might not pop out after you clip (It might with a little rocking). Sometimes they're soldered to the chassis pretty good.
I have no beef with you clipping leads. Its a little difficult sometimes to get clean leads (often stranded with caked on solder) to reattach. Kind of why I described what i did before.
Cutting tabs off keeps your connections together. If you leave in place, you sometimes can hold wire with long nose and pull while heating with iron.
Sometimes you have no choice but to save as much lead as possible and then sleeve and/or heat shrink.
Oh,
I didn't look at the can.
It may have different values identified with symbols, (triangle, square, half moon...
) make sure new cap orients to same connections when you install.
If all the sections are the same it really doesn't matter but it's a good habit to get in to.
 
I just looked
The 40-40-40-40 @ 350v is fine.
The first section off the rectifier should only be a single 40.
You can double up either of the other 2 for a little more capacity ( yes pun intended)
It likely won't make much of a difference so you can just as well leave blank
 
I was looking at you pics.
That cap is mounted on an insulator.
The tabs aren't soldered to the chassis.
It will come right out.
Just unsolder wires and components
 
Ok, if I understand you correctly @nj pheonix, I can just desolder the leads from the tabs, and then pull the can. If that will work, I'll move forward with that—

I didn't quite understand your comment on doubling up. My plan was to just copy exactly what is existing here—do you think that'll work? I'm trying to idiot-proof this process as much as possible :rolleyes:

Here are a couple closeup shots of the multi section can from underneath the chassis:

RC A1000 CanCapCloseup02.jpg


RC A1000_CanCapCloseup.jpg
 
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