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be a short to ground elsewhere. The capacitor you used does not appear to be an X2-rated type. Check all the component values, especially around IC3. Suitable material for speaker cabinets I am interested in building the Senator loudspeakers (September 2015; siliconchip.au/Series/291). The author suggests making the walls of the cabinets from furniture boards available in Australia, but in Poland, it is difficult to find such material. Is it possible to build the columns simply from MDF or beech timber, keeping the dimensions? Also, three sides of the cabinet (front, top and side) have double thickness. Is this only for aesthetic reasons, or does it have acoustic significance? If it has an acoustical significance, can I simply use thicker material for these walls? (B. K., Poland) ● It is OK to use MDF or beech; our construction was based on locally available materials. The double sides are for both aesthetic reasons and superior acoustics, so please use the same Advertising Index Altronics.................................27-30 Dave Thompson........................ 103 Digi-Key Electronics...................... 3 ElectroneX..................................... 7 Emona Instruments.................. IBC Hare & Forbes............................. 11 Jaycar.........................IFC, 9, 40-41, ...............................61, 66-67, 86-87 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 dimensions if possible. You could use thicker MDF rather than doubling it up if you prefer. Currawong transistor equivalents Regarding the Currawong 2 × 10W Stereo Valve Amplifier (November 2014 – January 2015; siliconchip.au/ Series/277), the STX0560 transistors have been discontinued and are no longer available. Unfortunately, there don’t seem to be any 600V TO-92 transistors anywhere. The highest rating I can find is either 400V or 500V, and there is no stock until October 2023. I know the rail is only supposed to be 310V, but 400V is still too close for comfort to my mind. Do you know of any suitable equivalents, or are you confident that a 400V transistor like the PHE13003A,412 (currently in stock at Mouser) will be OK? (T. S., Balcatta, WA) ● We think a 400V collector-emitter rating is sufficient. That’s still a safety margin of more than 25%. However, the gain of those transistors is pretty poor compared to the originals (30 vs 100 <at> 100mA). Therefore, we recommend also changing Q1 to a transistor like the BUJ302A,127. Its higher hfe of about 70, compared to 30 of the original KSC5603D, will partially compensate for the lower gains of Q2 & Q3. They appear to be pin-compatible and the BUJ302A has a more-than-adequate 1050V, 4A collector-emitter rating. In fact, the BUJ302A is a great transistor when a high-voltage NPN BJT is required. It avoids the poor gain problem of most other transistors with similarly high voltage ratings. It is available in both through-hole (TO-220) and SMD (DPAK) packages, although the SMD version is currently scarce. Microchip Technology.............OBC Oatley Electronics..................... 103 SC Advanced Test Tweezers...... 82 SC Pico W BackPack................ 101 Silicon Chip Shop.................98-99 Silicon Chip Subscriptions........ 13 The Loudspeaker Kit.com............ 6 Tronixlabs.................................. 103 Wagner Electronics..................... 89 104 Silicon Chip Errata and Next Issue Mouser Electronics....................... 4 Getting back to the topic of the discontinued STX0560 transistors, we’ve noticed that high-gain, high-voltage NPN transistors have gone extinct for reasons we don’t understand. It isn’t just the high-voltage types; even the ‘garden variety’ BC846C & BC856C are now unavailable from most vendors. We wonder if the silicon fabs that used to make these parts have changed their processes. Boost Controller troubleshooting I have built the Independent Electronic Boost Controller (siliconchip. au/link/abhk). The 10W resistor burns out as soon as 12V is applied to the board. I have not connected any inputs. What can be causing this? (L. N., Johannesburg, South Africa) ● Most likely zener diode ZD2, just below the 10W resistor, is shorted. Perhaps it is the wrong voltage type or has been installed the wrong way around. Trouble locating pin 1 of an IC I have been unable to locate pin 1 of the supplied INA282 IC. I checked the Texas Instruments data sheet, and my markings don’t correspond, so I have included a photo of the device for your opinion. My device has a white bar at one end; is that indicating the pin 1 end? (B. R., Eaglemont, Vic) ● We checked the TI data sheet, and all it shows is a chamfered edge on the pin 1 side and an “ID” in the pin 1 quadrant. Unfortunately, it doesn’t say what the ID marking is. That bar must indicate the pin 1 end, but we suggest you also check for a chamfer on the expected side. It’s hard to see the champfer if you are looking at the IC top-down. SC Heart Rate Sensor Module review, February 2023: for safety reasons, the module should be used with a battery-powered computer that is not connected to the mains, or any other equipment, during use. We also advise that the ‘patient’ avoids contact with any other equipment while the ECG probes are connected. 45V 8A Linear Bench Supply, October-December 2019: the circuit diagram (Fig.3) on p27 of the October 2019 issue shows the cathode of D5 connecting to the wrong location. It should instead connect to the VCC rail, which includes the positive ends of the 4700µF capacitors and the collectors of Q4-Q7. Next Issue: the April 2023 issue is due on sale in newsagents by Monday, March 27th. Expect postal delivery of subscription copies in Australia between March 24th and April 14th. Australia's electronics magazine siliconchip.com.au