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【製作事例】1968 Guyatone EB-15ピックアップリペア

[Production Example] 1968 Guyatone EB-15 Pickup Repair

This is an example of a pickup that was repaired and made at Nekodamari Kobo.

1968 Guyatone EB-15 pickup repair

We received an inquiry from our website about a request to have the pickups rewound. The equipment in question was a 1968 Guyatone EB-15 pickup.

When it comes to Guyatone, the Bisar series is popular, but from the name I thought it was a Gibson series electric bass, but it is actually an upright bass.

Upright basses are rare in themselves, and I have never seen one made by Guyatone. The symptom was that the sound was unusually quiet, so I suspect there may be an internal break or a wiring problem.

Since it was impossible to determine whether or not the item could be repaired without seeing it in person, we provided an approximate price estimate based on the staged repair work and asked the owner to send us the item in person.

◆ Repair proposal details

1. When the repair is completed with minor adjustments and modifications to the wiring

Simple repair cost: Approx. 2,000 yen + tax

2. If the diagnosis shows that repair is not possible

Only return shipping charges will be charged

3. When the entire film needs to be rewound

As it is a four-piece single coil setup, the estimated price is 10,000 to 15,000 yen + tax

4. When remaking almost the entire contents

To recreate the original shape, the estimated cost is 20,000 yen + tax.

This time, I only touched the pickup during the repair. Here is a photo of the actual guitar given to me by the owner. This is the first time I've seen it.

■ Start diagnosis Identify the cause Check power supply

When I checked the pickup that arrived, I found that it had a unique structure that was full of originality. One single coil is placed for each string, and the two are combined in an arch shape. The pickup cover is also custom made with welding, polishing, and surface treatment.

When Nekodamari Kobo works on a pet, we always explain the situation to the owner and get their consent before carrying out any risky disassembly. For this reason, we start by making a visual diagnosis when we arrive at the pet.

First, to check if a pickup is functioning properly, you need to check the electrical current and structure. If there is no resistance, no sound will be produced.

When I measured the pickup this time, it was "0.15k". It's a number that makes you wonder "why?" On the other hand, "0k" would be easier to understand, but there's no doubt that it is an abnormal value in general.

At the very least, if the coil was broken, it wouldn't conduct electricity, so it's possible that it isn't broken. Also, considering its age, it's in relatively good condition, so I decided to check the "structure" of the device.

■Continued diagnosis Identifying the cause Confirming the structure

I couldn't know the structure on the back until I saw it in my hands, so I guessed it would either have a ``humbucker-like structure'' or ``four single coils.''
The end result is a messy wiring with "four single coils." The components are three wires coming out of each coil, which are bundled together into a two-core lead wire. The tricky thing is whether these three wires are all the same or different. In some cases, the wires are reverse-wound and forward-wound, so...
What bothered me this time was that the wiring was exposed and the solder was old. If these are the reasons, it could be that the wires are in contact with the ground and there is no sound, or that the solder has peeled off and is unstable, causing the resistance to be abnormal.
One thing that bothers me a little is that it is a 1968 Guyatone EB-15, and some guitars and basses from this era have unique structures that don't follow basic theory. There are many unique products from the manufacturer, such as Besar, so it's possible that the pickup structure is different from what is commonly used today.
In this case, even if it is repaired, it may not be able to be used in modern times. Therefore, we contacted the owner to ask for permission to melt the solder and disassemble it to make an accurate diagnosis, while explaining our current impressions and diagnosis, assuming that the item would be rewound.

Confirmation to the owner

・Can I disassemble and perform simple repairs using solder? If the repair can be completed, the repair is complete.

- When rewinding, check the sound you have in mind and your playing style.

In the worst case scenario, if rewinding is not possible or if a part is damaged, the contents may have to be remade into something different.

■Continued Disassembly: Internal Disassembly and Reason for Failure

He readily agreed, and we continued with the work. Unfortunately, even after resoldering, the abnormal value did not change. Next, we need to disassemble it and check all the coils to determine where the abnormality is.

When I took it apart, I found it to have an interesting structure.

The structure is that a metal part with a bumpy surface is placed in the center of a small coil, and the magnetic force of a large magnet attached to a metal plate is transmitted. Although the structure is similar to that of a humbucker, it is not common, and in order to create this structure, it was not possible to use any general-purpose parts.

However, I found something strange. When I checked the coils individually, they all had electricity. This means that there is nothing wrong with the coils.

Also, even when I looked at the condition, it didn't look like it was damaged, so I couldn't figure out the reason for the failure. And from a general interpretation, the coils were also abnormal. One coil was "about 0.6k," which is 1/10 of the value of a normal ST.

Here, I checked the initial wiring again and found the reason for the failure. The wiring was incorrect, and the connection was in a way that negated the output.

However, another puzzling point is that if the pickup was being used by the owner and suddenly went wrong, the above reason does not apply.

If you bought it second hand and it doesn't make any sound or it's too quiet, then it will fit together, but that won't explain the abnormal coil. If you connect it correctly, the expected resistance is about 2.5k. This is still half of a normal ST.

Something that had been bothering me earlier comes to mind.

"It is a 1968 Guyatone EB-15, and some guitars and basses from this era have unique structures and are not made according to basic theory. There are many unique products from manufacturers such as Vissar, so it is possible that the pickup structure is different from the modern common structure."

In the unlikely event that it does not match the concept behind the product, we must consider the possibility that it may have been damaged. We have contacted the owner to clarify the circumstances, such as whether someone else may have tampered with it during production.

Confirmation to the owner

- Is this bass a bass that "the owner had been using and suddenly went wrong," or was it "bought second hand but has no sound or is too quiet"?

- As a matter of possibility, there is a possibility that the concept behind the manufacturing process may be flawed.

・Even if the wiring is corrected correctly, the result will be a low number that is generally less than 3k, but there are rare cases where pickups are made with this concept.

Thank you for contacting us early, and the owner's intention is,

"If it was a used item that had a problem with no sound from the moment it was purchased, and it has become difficult to use in general, then I don't mind rebuilding the whole thing."

We will continue to consider rewinding and propose specifications.

■While undergoing verification work...

It is rare for the resistance to be intentionally lowered, but in cases such as when the magnetic force is strengthened like in G&L, or when using a chained structure like humbuckers, there are designs that aim for low noise by intentionally setting the resistance low.

If the manufacturing concept had not been violated, there was a possibility that this could have been the intention, so we decided to reconnect the wiring to the correct one and carry out verification work.

For comparison, let's compare it with an Alnico 5JB pickup with a resistance of 10k...

It's not lacking in power, and the low noise specifications produce a straightforward sound that sounds great with effects.

My head is full of questions, but one possibility is that the sound was correct according to the design, but there was a mistake in the wiring work during manufacturing, and this incorrect wiring has remained floating around in the world and is still in existence today.

You might wonder, "Is that even possible?", but the wiring and solder are old, and because it is a unique upright bass, it may have passed through the hands of someone who used it without connecting it to an amplifier.

The owner was thinking of using it with a rock band, so if this sound doesn't suit them, I would recommend rewinding it, but it seems like it will be usable normally.

Since the customer had requested that we "just rebuild it," it might have been fine to just go ahead and rebuild it, but since it is a "pickup that hasn't been able to show its true potential for 50 years," we wanted the owner to try it out for themselves, so we made an unusual proposal.

Proposals for owners

- Complete this repair at this stage and try the product with the correct wiring.

- Try it out, and if you don't like it or have any concerns, reroll it or make modifications.

We contacted them and they agreed to let us try it out. They also requested that we make the lead wire longer, so we replaced it with a silver mesh wire from our inventory.

Repair completed! Review and points of regret

When the owner arrived and checked it, he checked it out with the band playing at full volume, and gave us the following comment:

"I am very pleased with how it can drive an amp so clearly with power that rivals that of a Precision Bass.

Because the strings have a large vibration range, the volume is sufficient to cause clipping unless the pickup itself is lowered quite a bit.
The sound quality is also natural and the original sound is amplified as it is.
*Photo sent by the owner

Since the product can be used without any problems, the repair is complete.

Looking back and thinking about it, I realize that I may have made things more complicated by my preconceived notion that it was a special Visar-type pickup and therefore thought that it might be unusable.

We were also informed that the owner had installed a cover earth, which was not included as standard. From a design perspective, since it is an upright bass, we believe that a cover earth was not necessary, but if we had properly checked the playing style, etc., we could have installed it in our workshop and delivered it to you, so we have added this as a point of reflection.

While each person will have their own feelings and thoughts about this, Nekodamari Kobo believes that this pickup repair has allowed a pickup that had not been able to perform to its full potential for 50 years to be used according to its original specifications.

You can always customize it to make it exactly how you want it, but if you're fortunate enough to have it in your hands, and it's in good condition and not "broken," I thought it might be a good idea to make use of it.

The owner would have had to incur unnecessary customization costs, so it may have been a bit presumptuous of a suggestion, but we are glad that he accepted it and was satisfied with the result.

I had the opportunity to see the actual product for the first time, and I was impressed that a pickup that gives off a sense of playfulness and challenge has been around for over 50 years.

At the same time, it gave me a good stimulus to try to create a pickup that is playful and challenging even in the modern era.

Since the repaired items have been tampered with by Nekodamari Kobo and are no longer original, we have placed a simple marking on them. We think that from now on we will continue to place unnoticeable marks on repaired items.

Summary: Cost, specifications, and duration

details of repair Pickup Repair Diagnosis
Repair specifications

1968 Guyatone EB-15 pickup wiring correction

Lead wire replacement

Material: Silver mesh wire

Repair cost 3,000 yen + tax (including return shipping)

Dear Owner,

Amount of burden

3,300 yen + one shipping charge (Yamato Transport)



Repair period

On average, it takes about 1 to 2 weeks.

This time: 2 days for diagnosis, 2 days for wiring correction work

Warranty details

Free repairs when defects occur within the normal range of use

Thank you very much for your request. If you have any inquiries regarding pickup rewinding, please feel free to contact us using the inquiry form.

Nekodamari Kobo Co., Ltd.

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