Dear Mr Poon, ([email protected]) 1/27/2015

Dear Mr Poon, ([email protected]) 1/27/2015 I found a good simple soluDon that doesn’t require taking the PCB out: Add a 4700 uF (16V or 32V) cap across C23 (330uF, 16V) to get: 30 sec delay from POWER ON to connecDng speaker, 9 sec from POWER OFF unDl disengages speaker. Add a 22kOhm R across these caps for rapid cap discharge to get: 36 sec delay from POWER ON to connecDng speaker, 2.5 sec from POWER OFF unDl disengages speaker. Connect C (+) between right leg (right, as viewed from the front of the amp) of 12V zener ("12V") (other side than the transistors are on) and C(-­‐) to ground leg of LED ("LED", leg towards the rear). Do not use smaller R than 22k as it may never reach the 12.5V to disengage the relay. Larger than 22k will reduce the benefit of speedy discharge. This R ensures that when amp is turned off and on there won’t appear any serious DC at the speakers. This way no serious cone movement is ever seen, except a slight one ~1 sec at turn off or during rapid power cycling. Justus V Verhagen SE-­‐160 MK1 DYI UPGRADE TO PREVENT TURN ON/OFF THUMP Several have noDced that powercycling the amps can lead to large cone excursions. Below is an effecDve and simple soluDon that doesn’t require taking the PCB out: STEPS 1) solder a 22k ohm resistor across the leads of a 4700 uF cap(16V or 35V electrolyDc, available at Radioshack etc.) 2) Connect this 4700 uF caps POSITIVE lead to right leg (right, as viewed from the front of the amp) of the 12V zener ("12V") (other side than the transistors are on) and connect the NEGATIVE lead to the ground leg of the LED ("LED", leg towards the rear). See pink arrows in the picture below. RESULTS: Adding a 4700 uF cap across C23 (330uF, 16V) gives: 30 sec delay from POWER ON to connecDng speaker, 9 sec from POWER OFF unDl disengages speaker. Adding a 22kOhm resistor (1/8W or higher) across these caps for rapid cap discharge to get: 36 sec delay from POWER ON to connecDng speaker, 2.5 sec from POWER OFF unDl disengages speaker. Do not use smaller R than 22k as it may never reach the 12.5V to disengage the relay. Larger than 22k will reduce the benefit of speedy discharge. This R ensures that when amp is turned off and back on there won’t appear any serious DC at the speakers. This way no serious cone movement is ever seen, except a slight one ~1 sec at turn off or during rapid power cycling. Justus V Verhagen 44 Rd
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Simple example: Here's a power-­‐on Dme delay relay circuit that takes advantage of the emiler/base breakdown voltage of an ordinary bi-­‐polar transistor. The 5.1 volt zener diode creates a higher turn-­‐on voltage for the Darlington connected transistor pair. Most any bi-­‐polar transistor may be used, but the zener voltage will vary from about 3 to 10 volts depending on the parDcular transistor used. Time delay is roughly 16 seconds using a 22K resistor and 1000uF capacitor and 5.1 zenner and can be reduced by reducing the R or C values. Longer delays can be obtained with a larger capacitor, the Dming resistor probably shouldn\'t be increased past 47K. The circuit should work with most any 12 volt DC relay that has a coil resistance of 75 ohms or more. The 10K resistor connected across the supply provides a discharge path for the capacitor when power is turned off. 46
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