Nakamichi PA-7AII
A power amplifier documented only in its own parts lists. That says something about how Nakamichi built it.
Overview
The PA-7AII survives in the record mostly through its service documentation, not its marketing. The manufacturer's parts manual for the PA-7II family lists the PA-7AII as a distinct variant alongside the PA-7II and the PA-7EII, each with its own carton box, front panel assembly, and rear panel part number. The PA-7AII's front panel is part number HA05431A, its rear panel 0H05299C, and its carton 0F04167B. That level of variant-specific documentation is typical of Nakamichi in this era. The same chassis and circuit topology shipped in several regional and revision flavors, and the parts book kept them all straight.
The manual makes clear that the PA-7AII shares its core architecture with the PA-7II and PA-7EII. The amplifier boards are listed as a common assembly. Amp. L P.C.B. Ass'y BA07259A covers the PA-7II, the PA-7AII (U.S.A.), and the PA-7EII, while a separate board, BA07446A, is specified for the PA-7AII (Canada). Anyone hunting parts today should know that, because the two boards are not interchangeable in the documentation. The right-channel board, BA07260A, is listed without regional qualifiers.
The output stage is a big bank of discrete transistors. Each channel uses nine 2SC3856 NPN devices and eight complementary 2SA1492 PNP devices. That's seventeen power transistors per channel, thirty-four in total across the amplifier. In the parts list they appear as individual line items with their own schematic reference numbers (Q116L through Q133L on the left channel, for instance). You only get that kind of detail when a manufacturer expects technicians to replace individual devices rather than whole modules. The front end uses a 2SK240 dual FET, five 2SA970 transistors, and 2SC2240 devices, with a μPC1237H IC handling protection duties.
Thermal management is handled by dedicated thermistor boards on each side - Thermistor L P.C.B. Ass'y BA07261A and Thermistor R P.C.B. Ass'y BA07262A. Each carries a 2SC3423 transistor, a 102AT-2 thermistor, and a 1K ¼-watt metal film resistor. There is also a limiter board, BA07263A, specified for the PA-7II (Other) and the PA-7AII. It is distinct from the BA07264A limiter board used in the PA-7II (Australia & Saudi Arabia) and PA-7EII. The limiter circuit includes a 24VDC relay, a DBA10 diode bridge, and a 500mA fuse.
The limiter board is one of the more interesting footnotes in the manual. Nakamichi built the PA-7AII with a limiter circuit that was not shared with every regional variant of the PA-7II, since the Australian and Saudi Arabian units got a different board. The parts list doesn't say whether that reflects different protection requirements, different regulatory expectations, or a running production change. It does confirm that the PA-7AII was not simply a relabeled PA-7II. It had its own bill of materials.
The rear panel carries the model-specific part number 0H05299C. The speaker output cords differ by market: the PA-7AII (U.S.A.) and PA-7EII share a yellow speaker cord (0B83335A), while the PA-7AII (Canada) uses a different cord (0B83550A). A separate input ground cord, 0B83334A, and a ground bracket, 0J05246A, round out the rear-panel assembly. The amplifier sits on four legs, part 0J05029A, shared between the PA-7II and PA-7AII.
Power input goes through a U.S.A.-specific power cord, 0B80200A, for the PA-7AII, with a single 10A fuse (0B90118A) protecting the U.S.A. unit. The PA-7II in other markets used a 7A fuse, and the Australian/Saudi/UK variants used a T6.3A slow-blow. The fuse rating difference between the PA-7AII and the PA-7II (Other) is a small but concrete sign that these were not identical amplifiers wearing different badges.
The service documentation also lists a full accessory package for the PA-7AII: an owner's manual in English, German, and French (0D04449A), a warranty card specific to the PA-7AII (0D04797C), a general catalogue (0D04766B), and a tape catalogue (0D04700B). A model-specific warranty card, not a generic Nakamichi card, suggests the PA-7AII was sold as a distinct SKU in at least some markets, not merely as a running change to the PA-7II.
Period coverage of the PA-7AII in the audio press is thin. Neither constitutes a formal review with measured specifications, and no independent lab data for the PA-7AII appears in the available period sources. The PA-7AII appears to have been a lower-profile variant than the PA-7II, possibly a market-specific or mid-cycle revision that never received the full review treatment.
The parts manual is what collectors and technicians can rely on, and it is unusually complete. It documents the amplifier down to individual resistor values and capacitor types - metal film and carbon resistors, electrolytic and mylar and polystyrene capacitors, zener and silicon diodes - and it distinguishes the PA-7AII from its siblings at the level of individual part numbers. For anyone restoring one today, that manual is the difference between guessing and knowing.
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