The size of suspensions for corvette speakers is 75 001. Audio and video equipment repairman in Barnaul

16.06.2019

Manufacturer: 150 AC-001 "Corvette" identical with 75 AC-001 "Corvette". Produced by NPO "Okeanpribor" (Peter). The only difference is in GOSTs.

Purpose and scope : For high-quality reproduction of music and speech programs in stationary domestic environments. The recommended power of a high-quality household amplifier is 10 - 100 watts. The preferred installation option is on a stand 0.3 - 0.5 m.

The distinguishing feature of the system is that it has high level characteristic sensitivity and the ability to withstand high values electrical power, which allows you to play programs with a wide dynamic range without audible distortion. This makes it possible to use the 150 AC-001 not only with conventional "analogue" program sources, but also with a digital laser player.

Specifications

3-way speakers with bass reflex

Frequency response: 25 (-19 dB) - 25000 Hz

Frequency response unevenness in the range of 100 - 8000 Hz: ± 3 dB

Sensitivity: 91 dB

Characteristic sensitivity: 0.73 Pa√W

Rated electrical resistance: 8 ohms

The minimum value of the total electrical resistance: 6.4 ohm

Maximum noise power: 100 W

Ultimate long-term power: 150 W

Limiting short-term power: 300 W

Weight: 30 kg

Dimensions (WxHxD): 38.6x71x34 cm

Design features

The AC case is made in the form of a rectangular non-separable box made of chipboard, veneered with fine wood veneer. The thickness of the walls of the case is 16 mm, the front panel is three-layer (plywood - chipboard - plywood) - 24 mm. The design of the hull includes elements that increase the rigidity of the hull and reduce the amplitude of wall vibrations - stiffeners and ties.

The 150 AS-001 uses a set of heads designed for a new generation of high-quality high-sensitivity speakers - produced by the Krasny Luch plant, which is located in the city of Krasny Luch. The design of head assemblies using specially developed software packages for calculating their characteristics on a computer made it possible to create efficient heads with low non-linear distortions. The heads are framed with decorative overlays made of ABS-2020 plastic: the low-frequency head overlay is round, with six mounting holes, the mid-range and high-frequency head overlay is rectangular with eight fastening holes. Midrange head with inside isolated from the total volume of the case by a special hermetic pipe connecting the front and rear walls of the case. The heads are located on the front panel symmetrically about the vertical axis. At the same time, in order to reduce the uneven frequency response of sound pressure in the frequency range of 1000 Hz, which occurs due to reflection from the front panel of the speaker, the midrange head is installed closer to the upper edge of the front panel, above the high-frequency head.

On the front panel, in addition, there is a decorative nameplate with the name of the speakers, the shape of the typical frequency response of sound pressure and overload indicators for the bass, midrange and treble bands of the speakers; a hole with a diameter of 75 mm, which is the outlet of the phase inverter pipe with a length of 91 mm. the geometric dimensions of the phase inverter provide tuning to a frequency of 36 Hz.

Internal volume of the EXPERT - 57 l. To reduce the impact on the frequency response of sound pressure and the sound quality of the speakers of the resonances of the internal volume, the speaker cabinet is filled with effective sound-absorbing material ATM-1.

Inside the housing, electrical filters are mounted, designed by methods of optimal synthesis using a computer and providing, in addition to electrical separation of low-, medium- and high-frequency bands of the speakers, also correction of amplitude and phase characteristics.

Filters provide separation of the bands: between the bass and midrange heads - 600 Hz; filter on the side of the bass head - 2 orders, and on the side of the midrange head - 3 orders; between MF and HF heads - 6000 Hz; the filter on the side of the midrange head is 3 orders, and on the side of the high-frequency head - 4 orders.

In the design of the filters, resistors of the C5-35V type, capacitors of the MBGO type, an inductor on plastic frames with "air" cores are used.

The speaker system 150 AC-001 has a circuit for protecting the loudspeaker heads from electrical overloads and indicating the presence of such overloads in the input signal.

When a signal appears at the AC input that exceeds the allowable power for any speaker, the protection device reduces the signal to a safe value for each corresponding head. The occurrence of an overload in any band of the speaker warns the glow of the indicators on the front panel above the corresponding inscription - LF, MF or HF.

The protection and indication circuits are configured to operate when a real musical signal is applied to the speakers with a peak power of 75 - 100 W, which corresponds to a sound pressure level of at least 110 dB. With the PROTECTION plug installed, the circuit operates at signal peaks of 300 - 350 W, which corresponds to a sound pressure level of about 116 dB. The first mode provides maximum reliability; the second is the maximum dynamic range and is used in tests for maximum short-term power.

There are four plastic legs on the base of the speakers, and on the rear wall there are terminals for connecting the supply wires and a PROTECTION socket for installing a plug-switch that changes (increases) the protection threshold.

Design features

The 75AS-001 uses a set of heads designed for a new generation of high-quality high-sensitivity speakers - 100GDN-Z, ZOGDS-1, 10GDV-4, manufactured by the Krasny Luch plant. The design of head assemblies using specially developed software packages for calculating their characteristics on a computer made it possible to create efficient heads with low non-linear distortions. The heads are framed with decorative overlays made of ABS-2020 plastic: the low-frequency head overlay is round, with six mounting holes, the mid-range and high-frequency head overlay is rectangular with eight fastening holes. The midrange head on the inside is isolated from the total volume of the case by a special sealed pipe connecting the front and rear walls of the case. The heads are located on the front panel symmetrically about the vertical axis. At the same time, in order to reduce the uneven frequency response of sound pressure in the frequency range of 1000 Hz, which occurs due to reflection from the front panel of the speaker, the midrange head is installed closer to the upper edge of the front panel, above the high-frequency head.

On the front panel, in addition, finding a decorative nameplate with the name of the speakers, the shape of the typical frequency response of sound pressure and overload indicators for the bass, midrange and treble bands of the speakers; a hole with a diameter of 75 mm, which is the outlet hole of the bass reflex tube with a length of 91 mm. the geometric dimensions of the phase inverter provide tuning to a frequency of 36 Hz.

In the design of the filters, resistors of the C5-35V type, capacitors of the MBGO type, an inductor on plastic frames with "air" cores are used.

The speaker system 75 AC-001 has a circuit for protecting the speakers from electrical overloads and indicating the presence of such overloads in the input signal.

After listening to my S-90s for two years, I finally wanted to change them to something better and more powerful. I didn’t want to give thousands of dollars, besides, I read an incredible amount of laudatory articles on the Internet about the Corvette 75AC-001, which, with the appropriate alteration, outplay many speakers in the price range from $500 to $1000. So I decided to buy them and remake.
In Minsk, these Corvettes very rarely appear, and after months of studying "From hand to hand" I saw the Corvette 150AC-001. All articles on the Internet unanimously claim that 75AC-001 and 150AC-001 are one and the same, so I gladly purchased the long-awaited last ones. In addition, the seller said that this was a converted version, handing me the extracted overload protection boards. I was even happier because I didn't even have to redo them myself. At the seller, I checked the performance of the speakers on his compositions without trying to test them for quality at all, because I was sure that if they were not burned, they would not play badly.

I brought it home, connected to my old 20-year-old Sharp amp, 80 watts per channel. And oh horror, the Corvettes played terribly muffled, yielding to my S-90s at times! But the lower classes certainly pleased me with both power and depth. In the end, I decided not to jump to conclusions before replacing the amplifier and wires - I had simple electrical ones.
My speakers cost so much that I need 12 meters of cable, so I bought a cable for only $ 2 per meter - Phoenix Gold (super OFC series SS162).
Amplifier Yamaha A-700 - 150 watts per channel into 8 ohms, signal/noise 106 dB, intermodulation distortion 0.005%. Nothing changed! I read on the Internet about the S-90 and found out that they have high tops and the middle is not correct.
The thought came - maybe I don’t understand high-quality sound at all, or I don’t have normal hearing at all, and this sound is correct?
Then I decided to compare them with my Sennheiseh HD-590 headphones - their sound compared to $ 1000 acoustics can be considered a reference. Of course, it is not entirely correct to make such comparisons, but as a result, I realized that the S-90 overestimate the upper range of the middle and highs, and the Corvette drowns out these ranges even more than the S-90 overestimates. After listening to the Corvettes also and turning the equalizer, I came to the conclusion that the biggest problem is in the 6-7 kHz range.
There were thoughts to bring the speakers back to the seller, fill the face and take the money.
But after some thought, I decided to open the column.
I had this one circuit diagram filter boards 75AC-001 with overload protection.

I also had articles on alteration. Immediately I saw that the coils are on a plastic frame, and not on the board like 75AC-001.
Further analysis showed that the filter board itself is different.
But looking more closely, I found some similarities. And then I realized that the seller who remade these speakers, seeing these discrepancies, did not climb further and simply threw out the overload protection board. And in articles on
the alteration says that you need to solder several resistors (marked in red on the diagram). Having compared and checked everything, I dropped out the necessary resistors and soldered the minuses of the speakers to one point. I assembled the speakers and heard that the middle and highs began to sound louder, less muffled by the lows, but the dip in the 6-7 kHz range still remained.

Then I decided to trace all the tracks on the filter board and draw a diagram, suspecting that there were some differences. And I found them. Here is the final version of the converted 75AC-001 filter board with marked elements that are simply absent in 150AC-001.

And here is the diagram of the 150AC-001 filter board, compiled by me after the alteration, and if you look closely, you can see that the values of many elements are slightly different from 75AC-001.

How much do these changes affect? Maybe it's not the filter board at all? Maybe it’s just that in 1991 they began to do everything badly?
And so I came across on the Internet a mention of programs that calculate electrical circuits. I found Electronic Work Bench Multisim 7. I downloaded the 70 mb demo - the limitation of the demo is that you can't save the file.
For two days I searched for crack, but did not find it and decided to just not turn off the computer.
It also took several days to figure out the program.
Here's what I got for the midrange. Red line - 75AS-001. Blue - 150AC-001 before rework. Green 150AC-001 after rework.

The sound changed a lot, most of all it was heard in the voice, but the left speaker sounded somewhat muffled than the right one, and then I experimented in Multisim and found that increasing the resistance of the resistor R2 shifts the high-frequency cutoff to the right on the graph. Experimentally, by ear, the value turned out to be 22 ohms.
Here's what I got for the tweeter. The graphs for the 150s and 75s coincide by 99 percent.

Here is a graph for the low frequency. Red line - 75th, green 150th.

From what I understand, it's not that bad. It's just that the 150s in the range of 3.5 - 3.8 kHz will sound a little quieter than the 75s. But this range is perfectly picked up by the midrange, so no problems are heard.
As a result, the speakers began to sound much better, but anyway, mid-high frequencies are not quite enough and this has to be corrected with an equalizer.
On the Internet, I came across information that the 75s were even back in the 90s. There is no date on my 150s, but the woofers indicate 91g, the 11th month, so most likely that all 150s are like that, but not a fact.
Crossover on the left before rework and on the right after.

Here you can see the coil for the woofer and large capacitors for the midrange.

So I have them located for listening, in the phase inverter there is a foam circle about a centimeter thick - this is better for my room.

I hope that this article will at least somehow help the unfortunate owners of 150AC-001 of the same issue as mine. Now I'm thinking of trying to find a filter board from 75AC-001 or even find the 75th to the 90th year. Haven't found it yet.
Despite the work done, the desired result has not been achieved.

Amplifier Corvette 100U-068S 1993 release. The amplifier is complete, has a layout similar to the amplifier Brig 001. The power amplifier has two separate supply voltages. +-23V and +-42V.

Brief description of the amplifier. Amplifier weight 7kg. The power transformer is covered by a metal shield, but not completely enclosed. It is small in power, about the same as in the amplifier Brig 001. The amplifier housing is assembled on a metal chassis, which is a sheet of metal about 0.4 mm thick. with holes for ventilation. On this sheet, the power amplifier boards, the power supply capacitor unit, the power transformer, the preamplifier and the tone block are fixed with screws. All modules are fixed with screws - similar to self-tapping screws. The top of the amplifier is closed with a cover, which is aligned with the front front panel of the amplifier. The front panel of the amplifier is plastic, black. The plastic is rather weak, prone to wear, so over time, “wiping” on the volume, tone, balance knobs is possible. Also on buttons. It is possible to cover the front panel with varnish or other composition to preserve appearance. You can use KRYLON varnishes to coat plastics.

The volume control - slide type is assembled from resistors, the same as on the Odyssey - 010 amplifier. Only in the Odyssey all controls are assembled from fixed resistors. In the Corvette, the rest of the controls - balance, tone, loudness - are simple variable resistors SP3-33. Over time, they also become unusable, the track wears out or breaks. Each button is highlighted with a separate light. Miniature light bulbs CMN are used as backlight, which shine through a red light filter built into the front panel. Red glowing red dots are obtained opposite each button.

Amplifier appearance.

View of the amplifier with the cover removed.

The internal layout of the amplifier.

Separately, we should talk about the backlight of the buttons, as everyone is faced with burnt out light bulbs. The buttons are illuminated by miniature SMN lamps of 10-12 volts. The voltage on the lamps is approximately 9 volts. The light bulbs are 5 pieces each in special plastic blocks, thin antennae leads are threaded into the holes and soldered to the output points. In this amplifier, some of the bulbs have already failed. You can replace them with the same ones, you can find them. If you replace light bulbs with LEDs, it will be more preferable and more beautiful. In order to replace light bulbs with LEDs, you need to do the following: LEDs need to be taken white color. Red LEDs can also be taken, but since there are already red filters in the front panel, I see no reason to put them. Light filters in the front panel are convex from the inside, from the outside. those. on the front they look like dots of red color. Therefore, if you put 3mm LEDs, they will not fit in size. Their leads can be inserted into the holes in the plastic block, but from the outside they will stand out for their entire length. Therefore, when we close the lid with the front panel, it will not close for us, the 3mm LEDs will interfere due to convex filters, and the 3mm LEDs themselves are large.

It is necessary that the LEDs are fully inserted in the same way as the paws in round cells, seats and did not protrude even a millimeter. Otherwise, the cover with the front panel will not close. I picked up such LEDs for 1.8mm, with a flat top. They fit perfectly in size and do not protrude beyond the cell. At the same time, they shine brightly in white. The second question is how to match them in terms of supply voltage. A voltage of about 9 volts comes to the light bulbs. It takes 3 volts to power the LEDs. It is necessary to take 300 ohm resistors with a power of 0.25 W and connect them in series to each LED. You can calculate the resistance of a resistor using a formula that is available on the Internet. At the same time, the voltage on the LED is limited to 3 Volts, which is what we need. It all looks like this:

Replacing light bulbs with LEDs.

Resistors of 300 ohms must be installed on the LEDs in two blocks, which contained 5 pieces each. light bulbs. The 6-light strip next to the record input switches will be wired differently. Resistors are not required for these LEDs. They already have 3 volts. If you put resistors on them, then the LEDs will not glow at all, because there will be a voltage drop across them. We have made changes to the amplifier circuit and therefore we need to take this into account. It looks like this:

LEDs without terminating resistors on the right side of the record input switches.

One more nuance - when connecting LEDs, polarity should be taken into account, because. voltage is constant.

Illuminated buttons with new LEDs.

P.S. In amplifiers SANSUI miniature light bulbs are also used for illumination. They can also be replaced with LEDs, but you need to take into account that the voltage on them is variable and you will also need a diode to rectify the alternating voltage.

The Corvette 100U-68S amplifier has differences in electronic components depending on the year of manufacture. Early versions of the amplifier were equipped with power filter capacitors for 15000 microfarads x 63V, 2 each. The capacitors were the same as in the Odyssey 010 amplifier - K50-37. Later releases of the amplifier already had other capacitors - 2200 microfarads x 63V each, which are made up of several capacitors, giving a total of 15000 microfarads per arm.

In the Odyssey - 010 amplifier, by the way, late releases also used 2200 microfarad x 63V capacitors made up of several pieces. And the metal knobs for adjusting the volume and tone on the early versions of the Odyssey - 010 had "cuts" for ease of regulation, on later versions they were already without "cuts", but simply round.

In the Corvettes of later releases, they went even further and replaced the output transistors in metal cases KT865 with transistors in plastic cases such as KT8101. The version I have is 1993. And capacitors and transistors have already been replaced in it in the direction of cheaper prices, or in the 90s the Union was already collapsing.

I decided to replace the 2200 microfarad x 63V capacitors with new ones, since there was no trust in them. The replacement was made with Jamicon capacitors.

We will install such capacitors in each arm with a voltage of + -42V. It will turn out 16,000 microfarads for each shoulder.

We replace electrolytic capacitors in the power filter.

It is also necessary to prevent the volume control resistor. To do this, it must be removed and disassembled. Wipe contact fields from dirt with alcohol, lubricate all rotating parts with new CIATIM-201 grease.

There was another problem with this copy of the amplifier. One channel was missing intermittently. The reason turned out to be simple, but finding it was not so easy. The contact on the power amplifier board connector was not soldered. After soldering all the pins of the power amplifier board connector, the sound became normal and did not interrupt.

Also, another feature of the Corvette amplifier that many people encounter is clicks after the amplifier is turned off. They were also in this amplifier. It is necessary first of all to replace the capacitor C2 of the protection unit with 22 microfarads with a new one and solder separate wires to its terminals, which must be connected to the free contact group of the PKN network switch. Thus, by turning off the amplifier, we discharge the capacitor C2, which does not have enough time to discharge. Perhaps this is due to a change in the scheme to replace light bulbs with LEDs.

The sound of the amplifier is decent. Excellent sound, there is dynamics, it does not paint the sound, like some amplifiers. There is more than enough power. The built-in LED power indicator allows you to focus on power, although it is hooked to one channel. Therefore, in order to maintain a decent sounding amplifier, you need to replace the power filter capacitors. Other capacitors can be changed as needed. Some of them are non-polar, some are electrolytic.

The disadvantage of the amplifier is its heating. He is already starting to heat up while working on the headphones. This is the mode of the output transistors, which have a separate power supply of + -42 Volts. At long work at high volume, it will get very hot, so you can install a fan to blow on the radiators of the output transistors, by the way, the radiators are small in it.

When developing the Corvette amplifier, the experience of creating the Brig-001 amplifier was taken into account. It will be of interest to fans of Brig.

Acoustic system Corvette 150AC-001.

Acoustics Corvette 150AS-001- I will describe the features of this acoustics. Compare it with 35AC-018 Amphiton.

Acoustics is made of chipboard panels, made quite neatly. All chipboard panels are perfectly aligned. The acoustics are painted with black paint, most likely my native black paint is on my copies. I’ll note right away that the wall thickness of the Corvette acoustics. Front wall made of 25mm plywood. In Amfiton 35AC-018 - the thickness of the front wall of chipboard is -38mm, but this is understandable, Amphiton 018th is the leader in front wall thickness among Soviet acoustics of the 35AC series. The woofer in this acoustics is quite large - 300mm. This is 100GDN-3. There are two spacers inside the case - one between the tweeter, the other is located vertically along the rear wall of the acoustics case. Spacers compensate for the rigidity of the hull and the lack of front wall thickness.

Inside, everything is also well fitted, there are not the slightest gaps. A fairly large woofer 100GDN-3 occupies almost half of the body volume. Here, of course, a more voluminous body would be needed. The 30GDS midrange speaker is mounted on top of the 10GDV-4 tweeter, which is also unusual. The midrange speaker is isolated inside with a cardboard cylinder, which rests against the back wall of the case, while creating additional rigidity of the case.

acoustic wiring. What can be noted. Made with dignity, the wiring is intertwined with black thread, neatly stacked. What can you say about acoustic wiring Amphiton 35AS-018. A single-core wire was used there, and of poor quality and thin. Which definitely needs to be changed. There is no need to change the wiring in Corvettes. It is stranded and thick.

At the bottom inside the case there is a filter on a separate board and a protection board. Protection is connected through a separate connector on the rear wall speaker system. Screw terminals are good, but they loosen over time. It is necessary to glue a textolite bar inside the case epoxy resin, tighten the screws and then the screw terminals will work normally.

In my copy, the woofer 100GDN-3 turned out to be with a handicraft suspension. The suspension was made of rubber window seal. Of course, such a suspension will not work normally and it must be replaced with a factory one.

Also, the 10GDV-4 tweeter did not work. There was a break inside the coil.

The sound-absorbing material inside the case is a lump of cotton wool glued in the middle to the back wall of the case. Whether the developers proceeded from the volume of sound-absorbing material is unknown, but the volume of wool in the two cases is different. Cotton wool, located in a single lump in the middle of the case, touches the wiring, part of it blocks the opening of the bass-reflex tube, and everywhere inside the case, the remains of cotton wool are scattered. To carefully lay the cotton wool, you can fix it with a piece of gauze. Attach gauze with a stapler.

Amplifier Corvette 100U-068S 1993 release. The amplifier is complete, has a layout similar to the amplifier Brig 001. The power amplifier has two separate supply voltages. +-23V and +-42V.

Brief description of the amplifier. Amplifier weight 7kg. The power transformer is covered by a metal shield, but not completely enclosed. It is small in power, about the same as in the amplifier Brig 001. The amplifier housing is assembled on a metal chassis, which is a sheet of metal about 0.4 mm thick. with holes for ventilation. On this sheet, the power amplifier boards, the power supply capacitor unit, the power transformer, the preamplifier and the tone block are fixed with screws. All modules are fixed with screws - similar to self-tapping screws. The top of the amplifier is closed with a cover, which is aligned with the front front panel of the amplifier. The front panel of the amplifier is plastic, black. The plastic is rather weak, prone to wear, so over time, “wiping” on the volume, tone, balance knobs is possible. Also on buttons. It is possible to cover the front panel with varnish or other composition to preserve the appearance. You can use KRYLON varnishes to coat plastics.

Amplifier appearance.

View of the amplifier with the cover removed.

The internal layout of the amplifier.

Separately, we should talk about the backlight of the buttons, as everyone is faced with burnt out light bulbs. The buttons are illuminated by miniature SMN lamps of 10-12 volts. The voltage on the lamps is approximately 9 volts. The light bulbs are 5 pieces each in special plastic blocks, thin antennae leads are threaded into the holes and soldered to the output points. In this amplifier, some of the bulbs have already failed. You can replace them with the same ones, you can find them. If you replace light bulbs with LEDs, it will be more preferable and more beautiful. In order to replace light bulbs with LEDs, you need to do the following: you need to take the LEDs in white. Red LEDs can also be taken, but since there are already red filters in the front panel, I see no reason to put them. Light filters in the front panel are convex from the inside, from the outside. those. on the front they look like dots of red color. Therefore, if you put 3mm LEDs, they will not fit in size. Their leads can be inserted into the holes in the plastic block, but from the outside they will stand out for their entire length. Therefore, when we close the lid with the front panel, it will not close for us, the 3mm LEDs will interfere due to convex filters, and the 3mm LEDs themselves are large.

It is necessary that the LEDs are fully inserted as well as paws into round cells, seats and do not protrude even a millimeter. Otherwise, the cover with the front panel will not close. I picked up such LEDs for 1.8mm, with a flat top. They fit perfectly in size and do not protrude beyond the cell. At the same time, they shine brightly in white. The second question is how to match them in terms of supply voltage. A voltage of about 9 volts comes to the light bulbs. It takes 3 volts to power the LEDs. It is necessary to take 300 ohm resistors with a power of 0.25 W and connect them in series to each LED. You can calculate the resistance of a resistor using a formula that is available on the Internet. At the same time, the voltage on the LED is limited to 3 Volts, which is what we need. It all looks like this:

Replacing light bulbs with LEDs.

LEDs without terminating resistors on the right side of the record input switches.

One more nuance - when connecting LEDs, polarity should be taken into account, because. voltage is constant.

Illuminated buttons with new LEDs.

I decided to replace the 2200 microfarad x 63V capacitors with new ones, since there was no trust in them. The replacement was made with Jamicon capacitors.

We will install such capacitors in each arm with a voltage of + -42V. It will turn out 16,000 microfarads for each shoulder.

We replace electrolytic capacitors in the power filter.

The disadvantage of the amplifier is its heating. He is already starting to heat up while working on the headphones. This is the mode of the output transistors, which have a separate power supply of + -42 Volts. When working at high volume for a long time, it will get very hot, so you can install a fan to blow the radiators of the output transistors, by the way, the radiators are small in it.

When developing the Corvette amplifier, the experience of creating the Brig-001 amplifier was taken into account. It will be of interest to fans of Brig.

Acoustic system Corvette 150AC-001.

Acoustics Corvette 150AS-001- I will describe the features of this acoustics. Compare it with 35AC-018 Amphiton.

At the bottom inside the case there is a filter on a separate board and a protection board. Protection is connected through a separate connector on the back of the speaker system. Screw terminals are good, but they loosen over time. It is necessary to glue the textolite strip with epoxy resin inside the case, tighten the screws and then the screw clamps will work normally.

Also, the 10GDV-4 tweeter did not work. There was a break inside the coil.