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hifi-alex  
#21 Posted : Wednesday, September 24, 2008 5:47:29 AM(UTC)
hifi-alex

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Has this problem been solved?

I ask because I've got a similar problem since I finally assembled my RevC's last weekend.

When switching the transformer on, nothing really happens. Relay doesn't start, LED is dark.
When switching it off, nothing happens at first, and after about 5-6 seconds the relay clicks twice (on and off) and the LED lightens up for half a second.

I checked all resistors, diodes and caps and there was nothing suspicious, besides that I soldered C6 in opposite way...
I changed C6 then, but the outcome was the same as mentioned above.

Voltages are +/- 36V on the rails (transformer is a +/- 25V one) an all voltages are as required (about 12.2V across ZD 1&2, 23.5V across R1&4).
The voltage between pin 1 and 7 of the LM318 is 24.2V and the LM3886 Voltages are +/- 36V like the rails...

I really don't know what to do now, any suggestions?
Russ White  
#22 Posted : Wednesday, September 24, 2008 6:04:40 AM(UTC)
Russ White

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I can only guess what the problem is, but it sounds like possibly one or more of the transistors on the protection/delay circuit is incorrect, or possibly bad? Also may need to recheck resistor values there.

Look carefully at each transistor and make sure it is the correct type for the spot it is in.

The other possibility is the the LM318 opamp is perhaps dead? What is the voltage at its output while the power is on?

Cheers!
Russ

Edited by user Wednesday, September 24, 2008 7:50:56 AM(UTC)  | Reason: Not specified

hifi-alex  
#23 Posted : Wednesday, September 24, 2008 7:18:53 AM(UTC)
hifi-alex

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Russ White wrote:
The other possibility is the the LM318 opamp is perhaps dead? What is the voltage at its outputs while the power is on?

Voltage from LM318's Pin 6 (Output) to PGND is 11.7 V...
Russ White  
#24 Posted : Wednesday, September 24, 2008 7:24:56 AM(UTC)
Russ White

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That's is definitely not right. It should be right around 0.
hifi-alex  
#25 Posted : Wednesday, September 24, 2008 7:28:43 AM(UTC)
hifi-alex

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Russ White wrote:
That's is definitely not right. It should be right around 0.

I ordered a few LM318 and BC546 & BC639 transistors and will replace them as soon as they arrive.

Thanks for your help for now!

Best regards,
Alex
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