Here is the description how to modify the Delco Bose radio model 16041551 to 0.05 MHz steps on the FM band. This is useful in countries other than the USA, where radio stations aren’t on odd-tenth megahertz intervals.
remove the upper cover (3 screws)
remove the 5 screws holding the first PC board.
gently lift the PC board.
locate two diodes (1N4148) between display and IC labeled “DM 246 DQ 7815D” (28 pin) on the second PC board, now visible.
there is spare place for another two diodes. Add a diode to the location closest to the above IC. This can be done in two ways:
Remove the bottom cover and the cassete drive, clean the soldering pads from solder. Solder in the diode and reinstall all removed parts.
Do nothing of point 1), but solder the diode across the IC mentioned above. Anode to pin 10 and cathode to pin 26. (This is much easier)
reinstall PCB and cover.
If you are not familiar with radio electronics and soldering, ask a friend to do the modification, who is.
Here are the functions the other diodes control:
Diode 4 installed:
Frequency range on FM is 87.5 – 104.0 Mhz, step 0.05 Mhz, frequency range on AM is 531 – 1602 Khz, step 9 Khz.
Diode 3 installed:
Frequency range on FM is 76.0 – 90.0 Mhz, step 0.1 Mhz, frequency range on AM is 531 – 1602 Khz, step 9 Khz.
Note: D3 and D4 installed does not do anything i.e: radio act as no diode is installed in D3 and D4
Diode 2 NOT installed:
No Seek and Scan function on the radio, setting clock is as usual.
Diode 1 NOT installed:
No clock on display when radio is switched off.
Information about the casette deck:
It is a Blaupunkt Toronto SQR 46.