AMP1-B does not work

[deepspace]

Last week I finally received two AMP1-B kit's. With great care, I build the first one, and hooked it up as desciribed in the manual. I checked voltages, they were all okay. LED goes one for about a second, than goes off (should all be normal). But the relay does not switch on, so no sound (also not before the relay.

So I build the next amp with even more care. And it works flawlessly! Just superb!

Now I compared the two to make sure I didn't do anything wrong. Only differences:
- some SMD resistors. 104 vs 1003, but I guess that's the same value
- The IC's. The non-working kit has small, thing gray letterling, while the working kit has bright, thick, large white lettering.

For the rest, everything is the same, capacitors are the right way, transistors are good...

Since the LED goes off, I guess the damage should not be to big. So I'm hoping someone can help me figure this out...

Do diamonds shine on the dark side of the moon?

[Jan]

Hi,

Did you double check that you did not mix up the transistors or the diodes? Q3 is different from Q1, Q2, Q4. D4 should be a 13V zener, D2 a 6.8V zener and D3 a 1N4148 diode. Your IC:s must have been from different batches but this should not matter.

Yes, 1003 and 104 are the same resistor values 100K. (100 with three trailing zeroes or 10 with four zeroes)

Anyway, good to hear your other amp is working well.

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quote:Originally posted by jan
Did you double check that you did not mix up the transistors or the diodes? Q3 is different from Q1, Q2, Q4. D4 should be a 13V zener, D2 a 6.8V zener and D3 a 1N4148 diode. Your IC:s must have been from different batches but this should not matter.

I'll tripple check it again when I'm back form the Holidays

quote:Anyway, good to hear your other amp is working well.

Absolutly And it sound superb,too. I'll hook it onto a scope tomorrow to see output noise and stuff. It can do 100 Mhz fft, zo should be intersting . Some people notices a 100 mv 1 Mhz sine at the output of amp3 (input shorted). I'd like to see if amp1 has something like that also.

Do diamonds shine on the dark side of the moon?

[Jan]

Hi, There should be a idle switching frequency of around 600 kHz visible, with inputs shorted. It should be about 40-50 kHz different frequency on the two channels.

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quote:Hi, There should be a idle switching frequency of around 600 kHz visible, with inputs shorted.

True. But it's 2 Volts large!






Do diamonds shine on the dark side of the moon?