Circle Oh Reader Service Card

Updates

Number 11 cn your Feedback card

Techno-Wtiizzy 1, Parts 1 & 2

Refer to the above article in the December 1992 issue, page 12. Diode D1 is backwards in the schematic diagram {Figure 3), it should be Installed as shown in Figure 1 below. Note that the diode position is shown correctly in the parts placement diagram in Figure 4b. TNX to Joe Leikhim for the correction.

The Baste program to determine the diode placement for a given frequency has a typo in line 9000 ("010 r was entered twice instead of l,0110").

It should read: S000 DATA "OQOQYQQOI YOG 10Y0G11VQ100VG 10lY0110Y01ir. As a result, the values shown in the accompanying sidebar entitled "Some Common QRP Frequencies for the TW-1" are in error and should be recalculated with the updated Basic program. TNX to JeanClaude Abmzit for the correction;

In the January 1993 issue on page 14, the wire size was omitted for the output filter toroid windings (Table 1). It's best to use #26 enameled magnet wire.

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12 volts

Figure 1. The corrected schematic of the Techno-Whizzy 1 voltage regulator circuit sfrow-ing the proper placement of diode D1. Refer to Figure 3 in the December 1992 issue.

12 volts

Figure 1. The corrected schematic of the Techno-Whizzy 1 voltage regulator circuit sfrow-ing the proper placement of diode D1. Refer to Figure 3 in the December 1992 issue.

Figure 3. Modifies (ton of the U9 connections to provide an improved Figure 2 (a). The corrected PC board fori pattern for the Programmable Frequency Audio Generator, pulse shape to the serial clock input of the ML2035 and to the CP0 (b). Parts placement. ci0ck input of the 74LSQ3 counter.

Programmable Frequency Audio Generator

Refer to the above article in the January 1993 issue, page 16. The PC board fort pattern shown in Figures 5 & 6 shows U9 as a 8-pin device; It should be a 16-pin device. Figure 2 shows the corrected version of the PC board foil pattern and parts placement

In addition, author Loyd Redman has some comments and improvements that will help you the circuit up and operating:

it Is recommended that you use only a 74LS73 for U7. If you substitute a 7473, the circuit may start operating at a random frequency when power is applied since the 7473

triggers on a positive-going pulse while the 74LS73 triggers on a negative-going pulse. If you do use a 7473h the connections to S1 should be changed so that U7 does not toggle until S1 is activated.

When using the ML2035, its output frequency may initially be half or double the desired frequency specified by the digital word. This indicates that the 16 bits of the digital control word a:e shifted either one bit right or one bit ieft. I noted that the pulse directly out of pin 2 of the CD4049 (U9) was poorly shaped, depending on the value of C3, Rt and Rin. I remedied the problem by first routing the output from pin 2 through one of the unused inverters in the CD4049, then on to pin 2 of the ML2035 and to pin 14 of the 74LS93 (see Figure 3), \ also recommend that you not use the same PC board for both the ML2035 and the ML2036 (i.e. populating the board for both parts but removing one of the ML parts), ( used separate boards for each version of the fC and carefully cut any traces not needed.

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