Tandy 2000 PSU

For more information, see this article's corresponding Wikipedia page: Device.

This device is in the WorkNeeded:OriginalParts category because it was flagged as missing information on the original parts. It may have replacement parts listed but those cannot be assumed to be identical to the originals. If you have a list of the original parts, please feel free to add them by copying the relevant table from EditorsToolbox:Tables

This device is in the WorkNeeded:General category because it was flagged as missing general information about the device. The information may be incomplete, using default text, or inaccurate and should be verified with external sources if possible. If you can add or correct information on this page, please feel free to edit it and do so.

Preliminary Information
Leak Risk	High
Batteries	None
Destructive Entry	No

The Tandy 2000 was a computer made by Tandy Corporation, based in Fort Worth, Texas, in 1983. The computer is unique for its use of the Intel 80186 processor, which is uncommon among PCs. While it is capable of running special builds of DOS 2.11 and Windows 2.0, its popularity was curtailed by its lack of hardware compatibility with IBM PCs. Plus, a bevy of technical bulletins and memoranda that came out about the system over the next four years indicated a product that one could argue was half-baked at release time. However, there was still a wide audience for these technical bulletins, and plenty of research into fixing, maintaining, and troubleshooting the Tandy 2000, because it ended up serving as the computer that would run Radio Shack stores throughout the 1980s and possibly beyond.

Known Issues

Symptom or Problem Encountered

One very common problem is that the Tandy 2000 will not proceed past the "Memory Size = ___KB" (e.g. 256KB) message.

Causes

• After displaying this message, the BIOS code tries to wake up the floppy drive and commence reading. If the floppy drive fails to seek anything useful, it will attempt to wake up the hard drive and do the same thing. If neither are readable, the system will hang without printing anything else to the screen. This is because what would normally be on the PC BIOS in terms of bootstrapping the OS actually exists on the Tandy 2000 boot disk.

Solutions

• Ensure you have bootable media in the system. It is not enough to fully diagnose the system with simply a working power supply and monitor.
• Check that the floppy controller and cable is properly working, and that correct power is getting to the drive.
• Use a floppy disk emulator and compatible image. Note that the Tandy 2000 uses 720KB DSQD (quad density) media at a 250kbps throughput rate, with double the tracks of a 360KB DSDD disk but at the same throughput as a DSDD disk.

Disassembly Notes

The computer and its power supply are rather easy to disassemble and pull apart. The trickiest part about changing the capacitors is that many of them are soldered flush to the board, making it difficult to wiggle them out of their spots. Furthermore, the four located within the shielding are the most difficult of all to wiggle. For these, it is especially recommended to use an electric desoldering vacuum pump, rather than any kind of manual pump.

Original Parts

Basic PCB Name

All capacitors have +/-20% tolerance.

Capacitor Specifications and Footprint Information

RefDes	Qty	Capacitance	Voltage	Mount	Diameter/Size	Height	Lead Spacing	Temp	Type	Brand	Series
C6, C8, C9, C10, C11, C12	6	2200 µF	16	Radial	18.5 mm	37 mm		105 °C	Electrolytic
C18, C20, C24, C26, C28	5	10 uF	35	Radial				105 °C	Electrolytic
C19	1	4.7 uF	50	Radial				105 °C	Electrolytic
C21	1	100 uF	35	Radial				105 °C	Electrolytic
C29	1	330 uF	16	Radial				105 °C	Electrolytic
C30, C40	2	220 uF	250	Radial	26 mm	40 mm		105 °C	Electrolytic
C31, C32	2	100 uF	250	Radial				105 °C	Electrolytic
C42 (and possibly C37)	2?	1000 uF	16	Radial				105 °C	Electrolytic

Replacement Parts

Basic PCB Name

Capacitors

RefDes	Qty	Compatible Part Number	Order Links
C6, C8, C9, C10, C11, C12	6	EKYB160ELL222MK20S	Mouser
C18, C20, C24, C26, C28	5	ESC106M035AC3AA
C19	1	EEU-FR1H4R7
C21	1	EKYB350ELL101MF11D
C29	1	EGXL160ELL331MJC5S
C30, C40	2	UCS2E221MHD
C31, C32	2	EEU-EE2E101
C42 (and possibly C37)	2?	EKYB160ELL102MJ16S

If parts are not available or different selection is preferred, you can use the values in the Original Parts section to perform a parametric search.

Related Links

Tandy Model 2000HD (abytebehind.com)

GitHub - Tandy2K/Tandy2000: Tandy 2000 Archive