[{"content":"","date":null,"permalink":"/categories/","section":"Categories","summary":"","title":"Categories"},{"content":"","date":null,"permalink":"/devices/","section":"Devices","summary":"","title":"Devices"},{"content":" The Dexibell VIVO P7 is a sample-based, fully polyphonic digital piano. It uses a Fatar TP/100 LR keybed, which features 88 weighted keys, hammer action and triple key contacts to ensure maximum fidelity in the action and in the velocity response.\nDexibell VIVO P7 This stage piano is a very robust machine and is very well suited for live applications. Sometimes though, intense live usage and exposure to moisture and heat can cause damage to the keybed rubber contacts and make some of the keys behave incorrectly. The resulting behavior can be missing dynamics, missing NOTE ON or NOTE OFF messages. This phenomenon happens usually on the most used keys. In the case of this particular instrument, the affected key was middle C — what did I just say?\nKey Contacts #The part of our interest is a rubber strip of 12 contacts (13 for the last octave). Each of the contact presents three small carbon-charged rubber tips, one by one offset by a very small amount in height. When the player strikes a key, the three small nubbins press in a fast sequence against corresponding contacts on the keybed PCB and the instrument CPU reads the key press.\nThe difference in height of the three contacts allows for very high quality sound dynamics. In fact, the CPU reads the speed of the key stroke based on the delay between the sequential contacts of the three rubber tips and converts this into MIDI velocity, digitizing the player expressivity with high fidelity.\nKey contact strip Since the Fatar TP/100 keybed is still in production, key contacts are very easily obtainable from an official spare parts dealer — and since I live in Italy and Fatar is an Italian company, this is going to be a piece of cake.\nReplacement Procedure # Warning: This repair requires removing one full octave of keys from the keybed. The plastic the keys are made of can be very brittle and a precise extraction procedure is needed to avoid breaking the key retention clips. Disassembly \u0026amp; Keybed Extraction #The initial stage involves disassembling the instrument flanks and front panel. Once the front panel is loose, the ribbon connector that links it to the main board can be disconnected and the front panel can be put aside.\nAfter the front panel is off, unplug the three ribbon cables that tether the keyboard and the aftertouch bar to the main board. Remove also the screws that fix the central metal bracket to the instrument chassis.\nWarning: Ribbon cable holding clips are very fragile. Controlled and symmetric force must be applied when unlatching the retainers on the connector in order to avoid the risk of breaking the small plastic parts or ripping the connector from the PCB. Then, the instrument must be put face down. In this position all the mounting screws of the keybed can be easily removed from the bottom of the chassis. When all the screws are undone, the back chassis should come up freely and leave the keybed in the upside-down position.\nNote: To avoid scratching the keys and making the keybed fall, put a soft mat or a folded rug under the keyboard whilst it\u0026rsquo;s in the upside-down position. Key Removal #To avoid a complete disassembly of the keybed, to access the key contact strip all the keys of the affected octave must be removed carefully. In order to to this, a controlled and steady pressure must be applied from the back of the key, where the key grabs on the back mounting rail. The key will pop out and will be possible to remove it by pulling it up.\nKeybed removed from the chassis Note: Sliding parts of the keys are covered in white lithium grease. Do not wipe off the grease and do not make the lubricated parts contact other parts of the instrument. If some of the grease is wiped off, reapply it before repositioning the keys. Contact Strip Replacement #The affected strip can be removed just by pulling it away. All the small centering cylinders will pop out of the keybed PCB and all the contacts will be exposed. This is a good moment to gently wipe the contacts on the PCB with a cotton swab slightly wetted with isopropyl alcohol.\nThe positioning of the new contact strip is quite delicate. With a small hex screw or with an unbent paper clip all the small rubber cylinders must be refitted to the PCB holes. This operation is a little bit fiddly because if too much pressure is applied there is the risk of rupturing the rubber membrane that holds the strip together.\nReassembly Steps #When the contact strip is completely flush on the PCB, all the keys can be reinserted and clipped to the back rail ot he keybed. While remounting the keys, it is necessary to carefully reintroduce the mechanical cams of the key hammer action on the key side slots.\nAfter all the keys are placed back on the frame, rotate back the keybed to an upside-down position and reposition the back chassis on top of it.\nWarning: Keybed threaded standoffs are made of plastic. When fastening the screws, ensure to catch the correct threading, otherwise the standoff can split apart and the screw might not torque correctly anymore. Reinsert the ribbon connectors on the main board, reattach the center bracket to the chassis and reconnect the front panel ribbon cable.\nFinally fasten the front panel back and reassemble the keyboard flanks.\nFinal Test #Simply playing all the keys of teh affected octave tests out if the notes are correctly read and played. If a thorough test is needed, it is possible to connect the keyboard to a DAW and check the MIDI velocity response of all the notes and verify its consistency in the octave and between different octaves.\nThis type of maintenance is key — pun intended — in the life of a stage piano. And fortunately it is a very quick and easy routine. Don\u0026rsquo;t mistreat you keyboards. Keep \u0026rsquo;em clean and dry!\n","date":"July 20, 2026","permalink":"/posts/dexibell-vivo-p7-key-contacts/","section":"Posts","summary":"\u003cp\u003eThe \u003cstrong\u003eDexibell VIVO P7\u003c/strong\u003e is a sample-based, fully polyphonic digital piano. It uses a \u003cstrong\u003eFatar TP/100 LR\u003c/strong\u003e keybed, which features 88 weighted keys, hammer action and triple key contacts to ensure maximum fidelity in the action and in the velocity response.\u003c/p\u003e\n\u003cp\u003e\n\n\n\n\n\n\u003cfigure\u003e\n    \n    \n\n\n\n\n\n\n\n\n  \n    \u003cpicture\n      class=\"mx-auto my-0 rounded-md\"\n      \n    \u003e\n      \n      \n      \n      \n        \u003csource\n          \n            srcset=\"/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_a8744732cc762ab.webp 330w,/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_479e45d338739126.webp 660w\n            \n              ,/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_71328c054a183e80.webp 1024w\n            \n            \n              ,/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_8493bfdfa2164297.webp 1320w\n            \"\n          \n          sizes=\"100vw\"\n          type=\"image/webp\"\n        /\u003e\n      \n      \u003cimg\n        width=\"1324\"\n        height=\"583\"\n        class=\"mx-auto my-0 rounded-md\"\n        alt=\"Vivo P7\"\n        loading=\"lazy\" decoding=\"async\"\n        \n          src=\"/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_a0ccc6320be51d7d.png\" srcset=\"/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_22308198ada3a285.png 330w,/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_a0ccc6320be51d7d.png 660w\n          \n            ,/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_1f7f68da737fc98c.png 1024w\n          \n          \n            ,/posts/dexibell-vivo-p7-key-contacts/vivo-p7_hu_8beb01af1958b93d.png 1320w\n          \"\n          sizes=\"100vw\"\n        \n      /\u003e\n    \u003c/picture\u003e\n  \n\n\u003cfigcaption class=\"text-center\"\u003eDexibell VIVO P7\u003c/figcaption\u003e\n\u003c/figure\u003e\n\u003c/p\u003e\n\u003cp\u003eThis stage piano is a very robust machine and is very well suited for live applications. Sometimes though, intense live usage and exposure to moisture and heat can cause damage to the keybed rubber contacts and make some of the keys behave incorrectly. The resulting behavior can be missing dynamics, missing NOTE ON or NOTE OFF messages. This phenomenon happens usually on the most used keys. In the case of this particular instrument, the affected key was middle C — what did I just say?\u003c/p\u003e","title":"Dexibell VIVO P7 Digital Piano — Silent middle C"},{"content":"","date":null,"permalink":"/devices/dexibell-p7/","section":"Devices","summary":"","title":"Dexibell-P7"},{"content":"","date":null,"permalink":"/tags/digital/","section":"Tags","summary":"","title":"Digital"},{"content":"","date":null,"permalink":"/tags/keybed/","section":"Tags","summary":"","title":"Keybed"},{"content":"","date":null,"permalink":"/categories/keyboards/","section":"Categories","summary":"","title":"Keyboards"},{"content":"","date":null,"permalink":"/tags/piano/","section":"Tags","summary":"","title":"Piano"},{"content":"Typical content: what broke, how it was diagnosed, what was replaced, and whether it worked. With some bonus tips and tricks from the bench.\nCome here for vintage audio, synthesizers, effect pedals — the kind of hardware worth fixing rather than binning.\n","date":null,"permalink":"/","section":"pmtronics // bench stories","summary":"\u003cp\u003eTypical content: what broke, how it was diagnosed, what was replaced, and whether it worked. With some bonus tips and tricks from the bench.\u003c/p\u003e\n\u003cp\u003eCome here for vintage audio, synthesizers, effect pedals — the kind of hardware worth fixing rather than binning.\u003c/p\u003e","title":"pmtronics // bench stories"},{"content":"","date":null,"permalink":"/posts/","section":"Posts","summary":"","title":"Posts"},{"content":"","date":null,"permalink":"/tags/repair/","section":"Tags","summary":"","title":"Repair"},{"content":"","date":null,"permalink":"/tags/","section":"Tags","summary":"","title":"Tags"},{"content":" The Dave Smith Instruments Prophet \u0026lsquo;08 is a modern classic, an 8-voice, 16-oscillator powerhouse that brought the Prophet name back to the forefront of analog synthesis, honoring the iconic Prophet 5.\nDave Smith Instruments Prophet \u0026lsquo;08 synthesizer However, even the best designs can have an Achilles\u0026rsquo; heel. If you own an early Prophet \u0026lsquo;08 or even its renewed PE version (Potentiometer Edition), you\u0026rsquo;ve likely encountered the dreaded \u0026ldquo;erratic values\u0026rdquo; when moving the encoders on the front panel.\nThe factory-installed continuous encoders are notorious for oxidation. Over time, the internal contacts degrade, leading to jittery values that make precise sound design an exercise in frustration. Or even impossible! Today on the bench, we are performing something more than a simple repair. I would define it a full \u0026ldquo;organ transplant\u0026rdquo; — replacing every single factory encoder with high-quality stepped alternatives.\nTo understand the issue, we have to do a quick detour on how digitally controlled analog synthesizers manage front panel reading and controls. Two main architectures are usually implemented:\nPotentiometers as voltage dividers — each control on the front panel is a linear potentiometer; the voltages present at each wiper are buffered, sampled at regular intervals by an ADC, stored by the CPU, converted back to analog voltages by a DAC and used as Control Voltage (CV) sources for all sections of the synth (an in-depth analysis on this architecture will be on a future read, when we will be working on the Moog SubPhatty). Rotary encoders — and since this is the case for the Prophet \u0026lsquo;08 on the bench today, let\u0026rsquo;s dive. How encoders work #Unlike a potentiometer, an encoder does not output variable voltages depending on its absolute position, but it works by sending precisely timed pulses depending on the direction of rotation. This principle is called Quadrature Encoding. The rotary encoder can be seen as two switches (called Channel A and Channel B) that open and close in sequence as you turn the shaft.\nThe switches, closing, connect the input voltage to the outputs, generating signals that are \\(\\pm 90^\\circ\\) out of phase. Phase is positive when turning clockwise and negative when turning counter-clockwise. The CPU monitors the state of both channels to determine the direction of the turn:\nChannel A leads Channel B: increment the value in memory. Channel B leads Channel A: decrement the value in memory. When oxidation occurs on the internal contacts, the \u0026ldquo;pulses\u0026rdquo; become electrically noisy, technically they bounce. The CPU, instead of seeing precise and sharp pulses, sees a chaotic series of state changes, which it interprets as the parameter jumping wildly back and forth.\nParts # EC12E series 24 step rotary encoder For this upgrade, I have selected the Alps Alpine EC12E series. These are superior to the factory parts due to their higher rotational life and better sealing against oxidation. I specifically chose the version with the 20mm bushing (longer than stock) to provide better mechanical robustness and stability to rotation.\nModel Variant Quantity Prophet \u0026lsquo;08 (Standard) 52 Prophet \u0026lsquo;08 (PE Edition) 11 Note: The PE (Potentiometer Edition) primarily uses pots for the synthesis parameters, but still requires 11 encoders for menu navigation and specific stepped functions. Replacement Procedure # Mains Safety: This repair requires opening the chassis. Always ensure the power cable is disconnected before removing any screws. The internal power supply contains high voltage capacitors that can hold a charge for some time. Disassembly \u0026amp; PCB Extraction #The initial stage of the process involves removing all front panel knobs and chassis screws. Once the front panel is opened, the internal ribbon cables are disconnected, followed by the removal of all mounting screws securing the front panel PCBs.\nDuring the extraction of the front panel PCBs, caution is required because the plastic button covers can be loose and easily lost.\n\u0026ldquo;Snip and Pull\u0026rdquo; Removal Method #Since the original encoders are destined for the scrap heap, there is no need to struggle with desoldering the entire multi-pin component at once.\nInstead, the process involves using a sharp flush-cutting tool to snip every leg of each encoder. Once the main bodies of the encoders are cleared away, flux is applied to the remaining pins, which are then cleared out using either desoldering braid and a tweezer or a desoldering gun. The larger structural side tabs are subsequently removed using fine tweezers and a standard soldering iron.\nResoldering and reassembly #The next phase involves populating all vacant positions on the board with the new encoders and soldering each one to the board.\nThe front panel PCBs are then reassembled to the metal frame, again paying attention to the plastic button covers in order to insert all of them correctly, and the whole physical housing of the synthesizer is finally reassembled.\nFinal system settings #The final step requires modifying the internal software configuration settings to match the new hardware:\nPower on the synthesizer Enter Global Settings. Change the EncMode parameter from Non-Det to Detent Correct setting on the Encoder Mode menu page The Aftermath #The \u0026ldquo;organ transplant\u0026rdquo; is a complete success. Here the pile of removed parts.\nThe final scrap pile And here the fully resoldered boards with all the brand new 24-detent encoders. A machine brought back to life and a very happy knob fiddler.\nThe assembled panels If your own early-generation Prophet is sitting in a corner gathering dust due to jittery encoders, this upgrade is well worth the bench time — it breathes decades of new life into a modern analog classic.\n","date":"May 25, 2026","permalink":"/posts/prophet-08-encoder-replacement/","section":"Posts","summary":"\u003cp\u003eThe \u003cstrong\u003eDave Smith Instruments Prophet \u0026lsquo;08\u003c/strong\u003e is a modern classic, an 8-voice, 16-oscillator powerhouse that brought the \u003cem\u003eProphet\u003c/em\u003e name back to the forefront of analog synthesis, honoring the iconic \u003cstrong\u003eProphet 5\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\n\n\n\n\n\n\u003cfigure\u003e\n    \n    \n\n\n\n\n\n\n\n\n  \n    \u003cpicture\n      class=\"mx-auto my-0 rounded-md\"\n      \n    \u003e\n      \n      \n      \n      \n        \u003csource\n          \n            srcset=\"/posts/prophet-08-encoder-replacement/prophet08_hu_6eedb2410d30714a.webp 330w,/posts/prophet-08-encoder-replacement/prophet08_hu_81ad603abaed632a.webp 660w\n            \n              ,/posts/prophet-08-encoder-replacement/prophet08_hu_10e0ad1b52f29098.webp 1024w\n            \n            \n              ,/posts/prophet-08-encoder-replacement/prophet08_hu_631ff14f4d1e2238.webp 1320w\n            \"\n          \n          sizes=\"100vw\"\n          type=\"image/webp\"\n        /\u003e\n      \n      \u003cimg\n        width=\"1600\"\n        height=\"616\"\n        class=\"mx-auto my-0 rounded-md\"\n        alt=\"Prophet 08\"\n        loading=\"lazy\" decoding=\"async\"\n        \n          src=\"/posts/prophet-08-encoder-replacement/prophet08_hu_4620789bba5da9e2.png\" srcset=\"/posts/prophet-08-encoder-replacement/prophet08_hu_19b0196bc6061470.png 330w,/posts/prophet-08-encoder-replacement/prophet08_hu_4620789bba5da9e2.png 660w\n          \n            ,/posts/prophet-08-encoder-replacement/prophet08_hu_c62652a246ccd541.png 1024w\n          \n          \n            ,/posts/prophet-08-encoder-replacement/prophet08_hu_a4cfd294e8f8098.png 1320w\n          \"\n          sizes=\"100vw\"\n        \n      /\u003e\n    \u003c/picture\u003e\n  \n\n\u003cfigcaption class=\"text-center\"\u003eDave Smith Instruments Prophet \u0026lsquo;08 synthesizer\u003c/figcaption\u003e\n\u003c/figure\u003e\n\u003c/p\u003e\n\u003cp\u003eHowever, even the best designs can have an Achilles\u0026rsquo; heel. If you own an early Prophet \u0026lsquo;08 or even its renewed PE version (Potentiometer Edition), you\u0026rsquo;ve likely encountered the dreaded \u0026ldquo;erratic values\u0026rdquo; when moving the encoders on the front panel.\u003c/p\u003e","title":"Dave Smith Instruments Prophet '08 — Encoder replacement"},{"content":"","date":null,"permalink":"/tags/encoders/","section":"Tags","summary":"","title":"Encoders"},{"content":"","date":null,"permalink":"/devices/prophet-08/","section":"Devices","summary":"","title":"Prophet-08"},{"content":"","date":null,"permalink":"/tags/replacement/","section":"Tags","summary":"","title":"Replacement"},{"content":"","date":null,"permalink":"/tags/synthesizer/","section":"Tags","summary":"","title":"Synthesizer"},{"content":"","date":null,"permalink":"/categories/synthesizers/","section":"Categories","summary":"","title":"Synthesizers"}]