Designations

Basically there are -1 and -2 variations of the TM848 (1-single or 2-double sided). There are also two basic (PCB) variants. The older (larger) one with discrete logic and a newer (smaller) one with an 8748 microcontroller. The newest are the -1E and 2E. It is also strange that the manuals I am familiar with always use the designation -1 or -2 for the older models. But on my two drives and on various pictures on the Internet, however, I always read -01 or -02. There may still be another difference here.

The older -01 and -02 are belt-driven, the newer -1E and -2E not. To add a little more confusion, there is also a version -01 mod II. According to pictures I have, this corresponds to version -1E.

Images

I bought a pair of belt-driven Tandon TM848-02 on eBay US for $150, a bargain. Both drives are mounted on an inclined construction.

The older TM848-01/02 seems to have a fundamental problem with leaking electrolytic capacitors. I have observed this information both on the Internet and on one of my drives. See next picture. I have replaced all the electrolytic capacitors in both my drives. This takes a maximum of 30 minutes per drive.

After replacing the capacitors I have checked and calibrated the revolutions per second to 360 RPM. Use the variable resistor R133.

I also noticed that the following red area gets very hot (on both of my drives). Depending on the room temperature, this can heat up to 60 °C (140 °F). I cannot say whether this is generally the case or whether it is due to the age of some (other old) components. Both the resistors and the two ICs (SN75472P) look good on the outside; not burnt.

I did some tests with both drives and the TexElec 8" floppy drive adapter. I use the factory jumper settings. Both 8" drives are running fine now (Sep 2024).

• TM848 shipping carton with jumper settings (I use the factory settings)
• TM848 brochure
• TM848 service manual
• TM848-1E-2E user manual

• Verein zum Erhalt klassischer Computer e.V.: Reparatur 8 Zoll Tandon TM848-2E
• VCF: Tandon TM848-2 fuse
• VCF: Trouble with 8" Tandon TM848-02