Last Updated on 5 June 2026 by Suffocation
It is not a problem to operate old computers with AT power connectors using an adapter with a new ATX power supply. However, new power supplies usually do not generate the -5V that some sound and video cards require. The Voltage Blaster solves this problem. It is a small ISA 8-bit plug-in card whose task is to supply the -5V to the bus.
Thanks to Necroware for this project.
Link to the project
Views
Facts
- Provision of -5V on the ISA Bus
- Using the -12 Volt and a voltage regulator
- LED indicates if the -5V is present
Circuit diagrams
Documentation
No further information.
Assembly
Record
| Description | Worth |
|---|---|
| Gerber available | Yes |
| Gerber file | Link |
| Ordered where | JLCPCB |
| Piece | 30 |
| Price + Tax and Delivery | 25€ |
| Special features | Leedfree, Black |
Here the Gerber files are stored, please check the original page to see if there is anything newer.
Components
I ordered the components from Mouser; the price for one unit is approximately €3.
| Component | Size | Number | Description | Price € |
|---|---|---|---|---|
| U1 | LM7905G-TA3-T | 1 | Negative Voltage Regulator 6mA to 220V | 1,30 |
| C1, C2 | Elko, 33 uF | 2 | Electrolytic capacitor | 0.45 |
| D1 (optional) | LED, Green, 2V 5mm | 1 | LED | 0,08 |
| R1 (optional) | 330R | 1 | Resistance | 0,11 |
| Record | 1 | Record | 0,84 | |
| Summer | 2,77€ |
Structure
Variations
Order
- Resistance
- Voltage regulator (snip off directly after the thick part)
- LED
- Capacitors
Commissioning
Plug in and feel at ease. You might want to check the -5V pin on the ISA slot to make sure everything is okay before plugging in a card.
Miscellaneous
eBay
I've listed the remaining parts on eBay, €5.10 for the kit, €7.10 for the finished board.
Assembled for €10 including postage and packaging – https://www.ebay.de/itm/206324908879
As a kit for €7.10 incl. postage and packaging https://www.ebay.de/itm/206324928290
Data sheets
General Tips
Soldering points
Check the solder joints on the ICs again carefully, preferably with a microscope or magnifying glass, for short circuits and contact. Measure with a multimeter or continuity tester.
For small solder joints on through-hole components, use flux if possible; it makes life easier and increases the quality of the connection.
Problems
–
Conclusion
| Description | Worth |
|---|---|
| Successful | Yes / No |
| Price per piece | ~€3 (excluding labour and consumables) |
| Soldering time | 10 minutes |
| Function | Good – but has an ISA slot |
| Is it worth it | Yes – if you want to use a Soundblaster 2.0 with an ATX power supply, for example, you can't avoid such a solution. |
| Restrictions | Occupies an ISA slot; there are also solutions that can be integrated into the ATX cable. |
Related Posts
- Retro Projekt – DiskBuddy 64
- Retro Projekt – Joystick Tester
- Retro Project - ISA 8-Bit Backplane
- Retro Project – 8-Bit ISA Ethernet Card (isa8_eth)
- Retro Project – FDC USB Floppy Disk Controller
- Retro Project – Floppy Disk Controller (isa-fdc)
- Retro Project – ROMOS
- Retro Project – USB to RS232 Mouse Adapter
- Retro Project – Monotech ISA Double ROM
- Retro Project - Greaseweazle 4.1
Sources
To the project
Retro pages
https://archive.org – Old software, magazines, manuals, and much more.
https://theretroweb.com – PC Hardware Directory.
https://www.winhistory.de/index.php – DOS, Windows Version Descriptions.
Win 3.1x Tools and Tricks
Retro Forensics
https://forum.classic-computing.de/forum – German/English forum with many retro computer enthusiasts.
https://www.vogons.org – I have found many tips on hardware here, they also have a driver directory.
https://www.dosforum.de – Forum with strict rules and very helpful regarding DOS, Windows questions are not welcome.
https://dosreloaded.de – DOS, hardware repairs, BIOS files and more.
https://www.winhistory-forum.net DOS and Windows history.
Retro Shops
https://ram-co-shop.de - PC parts, including newer ones, have ordered a lot from there and it's always worked.
http://www.amoretro.de – Sold on eBay and has a nice directory of old hardware
https://retroreiz.de – Atari, Nintendo, Sega and others.
https://www.retroworld.info/de – Stickers, signs and more.
https://retesa-nb.de – Older PC hardware
https://www.retro8bitshop.com – C64 tricky
Logbook
| Date | Description |
|---|---|
| 23.09.2025 | Post created. PCB ordered. |
| 04.06.2026 | Images inserted, Data sheets added |
| 05.06.2026 | Post finalised, a few more pictures, remaining PCBs listed on eBay. |