b.w.d Mini-Lab Model 603B, includes function generator, regulated power supply and voltage/operational amplifier
The Power Supply of the BWD is fully working. I measured the 200V DC, the 15V
split rail and 6.3V AC power supplies, and all are measuring within 10% of
I did find some issues with the
amplifier section as it wasn't delivering the correct output. This is a
minor issue with the Op-Amps which are easily to replace. I did insert a new
one into a slot, and it seemed to work, however I didn't fully test this after
that to confirm.
The function generator has had some significant changes done
to it. The ramp generator was working and this fed into the 1st stage to
produce the base Triangle wave to feed the three function outputs (ie. Square,
Triangle and Sine waves).
The function generator is able to produce a square wave, however it doesn't
produce the Triangle or Sine wave.
Analysis of the circuit shows that several components are
- U100 - possibly an LM3046
to produce the sinewave
- U101 - possibly an MC1445L
- used for the Amplitude Modulation (AM)
- R18 - Unknown Value
Changes to the board:
- U5 - FET has been replaced
with a likely equivalent, and plugged into the IC socket.
- S102 - Looks to be rewired
- unknown reason why as this selects between the three waveforms.
- Several circuit board
tracks have been cut (drilled/knife). I suspect this is done to change the
circuit board to produce the square wave only.
- Additional resistors are
soldered off the board.
Square Wave - Works
Triangle Wave - not working
Looks to be missing the buffer stage between Stage 1 to the
amplifier, alternatively R18 goes directly into the amplifier, which I don't
think would work without the buffer impedance change. I copied the buffer
design from the Issue 21 of the BWD 603B on a breadboard, and was able to
produce the triangle wave output via the Function Generators amplifier.
Possible solution: Add an extra board and tap into
the Stage 1 triangle output and input it into the Function Generator amplifier
Sine Wave - not working
U100 and other components are missing. The board looks to
have had some changes to it to accommodate a square wave output only. I
couldn't get a sine wave output. Without the schematic I decided it would be
easier to build the circuit on a separate board and then tap it into the
amplifier output section.
Possible solution: Add an extra board and tap into the Stage 1 triangle
output and input it into the Function Generator amplifier output
Amplitude Modulation (AM Input) - Not working
FM input - Not tested
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