New (old stock) 251853-01 hybrid 30-pin chip for the Commodore 1571 disk drive. Gemini Artificial Intelligence (see below) refers to this chip as needing a 31-pin chip socket-- probably because one of the pins on the chip is intentionally missing. Installation would require a 31-pin socket even though there are only 30 pins on the chip. U.S. seller. Based on its condition we are sure this chip is new. Extremely rare. From U.S. seller!Note: We are not sure if this chip is compatible with the Commodore 128D computer (which has a built-in 1571 disk drive) or not. See my follow-up Gemini question (below-- near bottom) for the answer to this question.We strongly recommend that potential purchasers of this chip do adequate research to verify that this is the chip they need. If your Commodore 1571 disk drive is malfunctioning we cannot guarantee that this particular chip will solve the problem. Also, we strongly recommend that only highly skilled chip installers purchase this chip due to its unique pin configuration-- unless you are purchasing it only as a collector's item or as a spare for a professional installer to install for you at some future date (if needed). We also strongly recommend that installers of this chip seriously consider installing a compatible chip socket if possible to carefully insert this chip into. Overheating the legs of this chip while attempting to solder it in place could very likely cause permanent heat-related damage to this chip! Compatible chip sockets (like the ones mentioned by Gemini below) may be available on and/or other online sources. I don't remember how this hybrid chip is situated in relation to other internal components-- even though I have repaired hundreds of the 1571 disk drives decades ago (I never actually replaced one of these hybrid chips though). Before ordering make sure that there is enough clearance (in relation to other internal components) for the chip AND the chip socket to be installed-- unless you are purchasing this chip as a collector's item only.We ship these chips in special static-resistant chip boxes with black crisp anti-static foam to protect them.
This chip is in very nice overall condition (see photos) but may not be in mint condition.Because of the precision required to successfully install this chip (without damaging it) we are not accepting returns on this particular chip. You can see from the photos though that this is a new (old stock) chip. The way these are mounted on the 1571 circuit boards it would have been virtually impossible to remove this chip without the chip legs looking much worse than in the photos.Note: Our shipping price is a couple of dollars higher than our actual shipping cost on these normally because of our cost on the special anti-static boxes which we ship them in.We have been selling Commodore hardware, parts and accessories for nearly 43 years (since 1983) and have a great reputation. The following (slightly edited by us) information about this chip is courtesy of Gemini Artificial Intelligence (note we haven't independently verified all of this information from Gemini but it looks credible):
The 251853-01 (often marked as M36A2U57) is a Read/Write Hybrid IC that goes to the Commodore 1571 floppy disk drive. It sits at location U7 on the main logic board, where it functions as the head amplifier and stepper motor controller.
It is important not to confuse it with the 251853-02 variant, which is specifically designed for the 1541B disk drive. They are not interchangeable.
As for installing them, finding an exact 31-pin SIP (Single In-line Package) socket off the shelf is practically impossible today. However, because the chip uses standard 0.1-inch (2.54mm) pin spacing, you can easily create a custom socket using widely available modern components:
Machine-Tooled SIP Socket Strips: This is the most reliable method. You can purchase standard 32-pin or 40-pin machine-tooled SIP socket strips (sometimes called SIL sockets) and simply snap or score-and-snap the plastic to cut them down to exactly 31 pins. The round, machined holes provide a very secure, low-resistance grip for the flat pins of the hybrid IC.
Standard Female Header Pins: The standard square 2.54mm female headers will also work perfectly. To get a clean cut on a 40-pin strip, pull out the 32nd metal pin with a pair of needle-nose pliers, then use flush cutters to snip the plastic at the newly emptied slot. This prevents you from accidentally crushing the 31st socket during the cut.
Socketing these hybrid chips is highly recommended, as it prevents direct soldering heat from damaging the aging component and makes any future diagnostic work significantly easier.
Does this chip also work in the Commodore 128D computer which has a built-in 1571-type disk drive?
The answer depends on which specific version of the Commodore 128D you are working with:The answer depends on which specific version of the Commodore 128D you are working with:
The answer depends on which specific version of the Commodore 128D you are working with:Original Commodore 128D (Plastic Case): Yes. The original plastic-case model (primarily sold in Europe) essentially contains a standard, standalone 1571 drive logic board mounted internally. It uses the exact same 251853-01 Read/Write hybrid IC at location U7.
Commodore 128DCR (Metal Case): No. The "Cost Reduced" (DCR) version, which features a metal chassis and was the primary model sold in North America, integrated the disk drive electronics directly onto the main computer motherboard. In this redesign, Commodore eliminated the large 31-pin hybrid IC and replaced it with a smaller, surface-mounted CX20185 head amplifier IC at location U108.
If you are dealing with the metal-cased 128DCR, the 251853-01 cannot be used.
