Repairing a 1964 Gibson Skylark GA 5T Tremolo Tube Amplifier

“Adopt a son,” was the tagline under the Instagram photo. A local music shop had a vintage Gibson amplifier listed for sale in remarkably good cosmetic shape — except for the logo.

1964 Gibson Crestline GA 5T Skylark Tremolo

I had a quick chat with Mary about the rising value of vintage instruments that veered into a promise to sell the large Line6 AX2-212 amplifier sitting in my study, and I was off to retrieve the Gibson.

The amplifier had the original speaker, the original leather handle, no tears in the tolex or cloth, and very minimal rust on the faceplate. Unfortunately, the amp didn’t play quite as good as it looked. We still brokered a deal, and I brought it home. That’s when I took the week long deep dive into vintage radio and amplifier repair.

Yes, we have gone way beyond banana bread.

The Death Cap

It wasn’t until 1969 that Underwriters Laboratories mandated three-prong plugs on appliances. Amplifiers from the 1950s and 1960s came with a two prong power cord, which could be plugged in either way. The lack of earth ground made those amplifiers susceptible to RF noise. To combat this, designers added a capacitor between the negative terminal of the power cable and the chassis ground of the amplifiers. It was well-known and accepted at the time that if a musician was touching the guitar strings and touched another reverse grounded object such as a microphone, he or she would receive a noticeable shock. The problem with having a capacitor coming from the cable to ground was that if it failed open, it would deliver the full 120 volts AC to the musician.

The “paper caps” and the “death cap” on the unmolested board.

While I wanted to keep the amplifier as original as possible, I decided removing the “death cap” and adding a three-prong power cable with ground to earth was the way to go. I also relocated the positive cable lead to run through the fuse before the switch for a little added protection of the amplifier internals.

Three strand power cable with earth ground installed.

120hz Hum

The most noticeable issue with the amplifier was a very loud hum coming through the speakers even with the volume turned to zero. A lower 60hz hum can be an indicator of poor shielding, but a 120hz hum is usually an indicator of bad filter capacitors.

From what I could tell, the amplifier internals had never been touched, so the circuit was sporting two paper-wrapped electrolytic capacitors — a Maximite and a Minimite. I didn’t have a way to test those capacitors, but it’s generally accepted that the lifespan for a paper-wrapped electrolytic capacitor is 6 – 10 years. Being 56 years old, it was a pretty solid bet that both of them needed to be replaced.

I replaced the Maximite with two modern 22mf 450volt capacitors, and the Minimite was swapped for one of the same. I flipped the amplifier back on, and the hum was gone.

A pair of 22mf 400Volt capacitors in place of the Maximite.

As a side note, if someone is selling you a tube amp and says, “It has a hum, but it still plays great,” walk away. You can’t play great battling that hum. You can’t record with that hum. You can’t perform with that hum. Also, it’s just a matter of time before the leaking capacitors fry the power transformer and cause more damage to the amplifier.

The Mysterious Disappearing Tremolo

This amplifier has a built-in tremolo circuit powered by the oscillations of a vacuum tube. When I purchased the amplifier, it wasn’t working at all. Later at home you could hear the oscillations in the 120hz hum, but it wasn’t evident in the actual guitar sound. Then I tapped on a few connections and spread some crowded wires apart, and the tremolo disappeared completely.

My online searches turned up conflicting diagrams, some indicating a 6EU7 tube and some indicating a 6C4. As I researched both, the 6C4 was noted for it’s oscillations, so I ordered one thinking I had the wrong tube. Turns out a 6C4 isn’t even the right size for the plug. I tried a new 6EU7, and the tremolo was back.

Matched Power Tubes

When I purchased the amplifier, the dates and makes of the tubes varied greatly. The schematic called for two 6AQ5 power tubes, but one was a much more recent 6005. Power tubes are supposed to be electrically matched, so that they have the same plate current and amplification characteristics. The performance of vacuum tubes can vary wildly, so matched tubes were allegedly manufactured at the same time and more rigorously tested to meet the same specifications. When I ordered replacements from Amplified Parts, they sent me a pair of matched new old stock 6AQ5 tubes that were manufactured together in France in 1963. It kind of blows my mind that there’s still parts for these amplifiers sitting in warehouses.

Does the amp sound better with the matched tubes? Maybe I’m just a auditory plebeian, but I can’t tell a difference.

With the three-strand cable, new filter capacitors and new tubes, the amp is playing well, and I imagine it should be able to handle another 50 years. However, if I get the chance to upgrade my testing equipment I’d like to take some measurement and see how far off the original values the other capacitors and various resistors have wandered.

I should also probably spend a little time working on my guitar skills, so they do justice to this amplifier.

Review: Big Kahuna 12-volt Portable Shower

Thanks to a generous co-worker of mine we had the chance this weekend to test a Big Kahuna Portable Shower Shower.

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The system consists of the water tank (ours is 8 gallon, but they’re available in various sizes), the 12 volt plug, the hose with the shower head at the end, and a small water pump inside.  I was happy to see that both the plug, and the shower head came with very long cords because we had intended to put it down in the lazarette for after-swim shower and dog washing in the cockpit.

The pump inside is German made.

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The whole thing was very simple to put together, and even full of water was light enough for me to lift town into the lazarette. The top lid is supposed to absorb sunlight to give you warm showers, but I’m a bit skeptical of that claim.

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The pressure on it was similar to a standard shower head and about the same as what we get from the faucets on the boat. It wouldn’t do much good trying to spray mud off the anchor, but it has enough pressure to rinse soap out of your hair.

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It was also perfect for washing a certain smelly dog.

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It would definitely be more cost efficient to just connect a wash-down hose to our current water system. However, the Big Kahuna does have some advantages.

Not all boats have pressurized water systems, so it is definitely the easiest way to add a cockpit wash-down hose.

With the Big Kahuna you’re also adding additional freshwater capacity. It’s nice to know those cockpit showers aren’t cutting into the drinking water supply.

Portability is another perk. Take the Big Kahuna to the beach, and you no longer have to get back in the car with sandy feet or gear.

We’ll be testing the Big Kahuna further, but I’m definitely looking forward to rinsing the salt off next time I go swimming. Plus, no more dog hair in the boat drains.

The “Scrubba Wash Bag” Review

Last year we got the Scrubba Wash Bag from Fred’s brother for Christmas.

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It’s basically just a dry bag with bumps on one side and an air vent, but on the Scrubba website it brags that it will produce a “machine quality wash.”  We have been wanting to try it out, but until last week we’d never been on a boat long enough that we remembered to use it.

So here’s how it works:

1. Fill the bag with clothes, enough water to get them all wet, and a tiny bit of detergent. (We used fresh water for the washing, but I suppose it could be salt water.)

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2. Then you let out all the air and just swoosh it around. This can be harder than it looks, as a lot of the clothes tend to get knotted up.

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3. The bag then calls for two rinses. I think the first rinse could be salt water, and then the second rinse with fresh water, but we used fresh for both.

The Verdict

Pros

  • It did indeed wash the clothes, and several big stains came out.
  • It packs up into a tiny space. This would be a big deal if you were backpacking.
  • It can doubles as a dry bag, and you may also be able to use it in place of a bucket for some things.

Cons

  • If you’re only using fresh water, I feel like it uses just as much or more water than a sink or a bucket.
  • Even after the second rinse, the clothes were still a little soapy.
  • The actual washing is a bit awkward and difficult. It would be easier to stir and rub the clothes in a bucket than it was to try and rub them around in the bag.
  • It’s more likely to get a hole than a bucket.

In closing, If you are backpacking or camping I think this is a major advantage. It could roll up in your pack and serve several purposes. If you’re on a boat and you already have a bucket or sink with a good plug, save your cash.

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Mary’s thoughts on Sperrys

One of my friends the other day asked me if it’s true that boaters wear special shoes. Well we do, and for us at least in the past our choice has been Sperrys. These below are the current members of our collection. (I might have a few more pairs of shoes than Fred … )

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When choosing boat shoes I look for four things: non-marking soles, good grip on deck, comfort and style.

While I love my Sperrys for their style, I have trouble with blisters. They’re fine for short stints on deck, but if I walk around the marina in them my feet are killing me.

Fred, while finding his shoes to be very comfortable and wearing them all the time, has only had them for 14 months, and they are no longer gripping the deck. When this happens the shoes are actually dangerous, so he’s not allowed to wear them on the boat anymore.

We have fallen into the pattern of using the shoes for the first year on the boat, and then after that they become casual city shoes.

Recently Sperry came out with these new shoes, which for me anyway may be a solution.  Supposedly breathable, pack-able and flexible. I will have to give them a try to let you know what I think — except they’re $75. Maybe if I buy them I’ll be able to do yoga on a surf board like the girl in the picture.

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Lately I’ve just been giving up on looking fashionable and have been wearing some regular old Nike sneakers with white soles. I have to say, they look pretty awful, but man they are comfortable. They also dry fast and grip really well. I can walk for miles in them with no blister issues.

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Then there is always the option of going barefoot. I feel like there is some sort of rift on this subject with experienced sailors on either side of the issue. On one side going barefoot is comfortable, free, quick drying, and generally in the spirit of the vagabond lifestyle. On the other hand, if you are out on the ocean and you break a toe, it could be a problem. Although even on land most people will just let a broken toe heal on its own, so unless you manage to break your whole foot, it’s probably not going to be life or death. So far Fred has already broken two toes since we purchased Gimme Shelter. He kicked a dock cleat while not even on the boat, and then he broke the other toe on a pulley for the jib mounted on the deck. Since then he has been consistently wearing shoes, but with summer fast approaching and his shoes having hardened dangerous soles we will be back to barefoot before you know it. I can’t see myself dropping $150+ on another pair of Sperrys for both of us this year.

Does anyone have any suggestions for comfortable, long lasting boat shoes that don’t make me look like a soccer mom?

Improving the ONA Bowery camera bag

I’m always looking for the perfect camera bag. While big padded Lowepro bags and backpacks are great, they kind of scream, “HEY, I’M A TOURIST AND THIS IS MY CAMERA THAT YOU SHOULD STEAL!” For a very long time I was looking for something small and light that could still handle a camera body and one or two lenses when I’m traveling or hiking.

Then last Christmas my lovely wife bought me this beautiful ONA Bowery leather camera bag.

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In the past two years this bag has transversed the United States and crossed the Atlantic twice. However, the more I’ve carried it, the more I’ve noticed it has a few problems.

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On the inside, it has only one padded divider. That means you get one camera with a mounted lens on one side, and one lens or flash crammed into the other with a charger.

Those two small front pockets and two small side pockets can each hold one, and only one, of the following: a spare battery, a passport, a lens filter, or a USB cable.

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ONA touted this rear pocket as being for an iPad Mini or other small tablet. Well, I happened to have an iPad Mini, so I stuck it in there. However, it slid out twice in my car and once at Charles de Gaulle airport, so I decided sticking anything in the open back pocket was just asking for it to be lost or stolen.

ONA sells large padded dividers for the briefcase size bags and small padded dividers like what came with the Bowery, but for some reason they don’t sell a divider the width of the Bowery to create an internal iPad sleeve. However, my very lovely and talented wife, who was thoughtful enough to buy me the bag in the first place, can sew.

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For $15 I ordered two large padded dividers, and after about 30 minutes of work, Mary had downsized one of them to the interior size of the Bowery. (Thank you, honey!)

I now have a secure interior slot for the iPad, a notepad, or a battery charger.

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I really don’t know why ONA doesn’t sell the bags like this in the first place. The padded dividers are just cardboard wrapped in packing foam. (And they are a serious pain to cut through with old scissors!) If they can sell two for $15 at a profit, they could definitely add one to each bag without increasing production costs enough to raise the cost of the bag.

And now with the interior padded pocket for tablets, why not add a zipper to the rear outside pocket, so it’s actually usable?

Are you listening ONA?!!!

Shortly after I received this bag, ONA released the Berlin, which if I could do it all again, I’d probably choose that slightly larger model. However, being a gift from Mary, I’ll stick with the Bowery. It is a very tough bag, and it keeps me packing light when we’re doing lots of walking.

Winch woes

Our O’day 34 came with Barlow 25 winches. Barlow, like O’day, has been out of business for decades.

As I complete various spring-cleaning and maintenance tasks, I decided it would be a good time to service and lube the winches. However, while all previous winches I owned had some sort of snap ring holding them together, the Barlows had me stumped.

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No snap ring, no holes for a deck wrench — definitely no handy “tool free” servicing like you find in modern winches.

Also note the stress cracks in the fiberglass around the winch. O’day didn’t bother to use any sort of backing plate at all when they installed these.

To service the winch, you have to unscrew the reverse-threaded allen bolt in the center of the winch. However, being two speed winches, the winch rotates in both directions. Although I spent at least an hour trying to break the bolt loose, I was never able to budge it. I did, however, manage to strip out the head of the bolt in the port winch.

After much searching, I came across this on the Internet:

Barient/Barlow Winch Disassembly TOOL: Bar 395-Tool:
Special Tool for Assembly and Disassembly of various Barient and Barlow Winches. Tool has Winch Handle stud with a hole in the top to hold drive socket while using an allen wrench to loosen the socket screw.

Oh yeah, a tool like that would have been super helpful — too bad they don’t make them anymore.

So now I’ve got two Barlow 25 winches that, if nothing else, need to be unbolted, so that a proper backing plates can be put inside the boat.

We wandered by the Kemah Boater’s Resale shop looking for grill covers since we refuse to pay $50 for a grill cover at West Marine. (FYI, they have a million kettle-style grill covers, but no rectangular grill covers.) While we were there I spent some time looking at winches. There was only one Barlow winch in the entire store with the same type set-up as mine, and the allen bolt in the center had been replaced with a big flat-head screw. Obviously I was not the only one who had a problem with these things.

The shop actually had a set of Barlow 25 self-tailing winches for sale, but they had the much more user friendly set up with two holes in the center cap, so it could be screwed out with a deck-plate wrench. I thought about purchasing them since they were the same size and had the same bolt pattern, but then I asked myself, if I’m going to spend money to replace winches, don’t I want something that will have replacement parts if it breaks? Also, if I’m going to spend the money to change them out, don’t I want to upsize them, so Mary has an easier time trimming in the jib sheets?

Then I saw these guys sitting on the shelf for just a few dollars more.

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An executive decision was made.

No, we won’t be replacing the radar this year. No, we won’t be purchasing a dinghy this spring. Yes, we will be sailing with self tailing winches … as soon as I figure out how to get the old ones off.