Hey Team,
Been working on this "F7 inspired" clone, which has been a very fruitful adventure. Just as I was finished biasing the amp, the GND on one of the power rails jumped out and shorted to the V- on the same (this is at the PSU board) as I saw it happen I quickly I was able to power down the amp before "anything" happened. But as we know sometimes things happen in instants.
Before you scold me, I know, shouldve done a better job of soldering and confirming, which I'll you I thought I did, but alas, we've all been there I suspect.
After the frustration and panic subisded, and I got back to and and carefully checked and powered up the amp again after repairing the loose wire. All checked out and it plays normally.
Now, I've hooked up to a signal generator and an oscilloscope. The Oscilloscope was connected to a 8R 25W resistor meanwhile the signal gen is run directly to the RCA inputs. I am running a 1000HZ signal @5V to the amp, and I am hearing a high pitched whine coming from the amp somewhere. If I raise the frequency, so does the pitch go up.
Admittedly, I didnt get to this step before my incident, and this is my first rodeo with the oscilloscope and generator in this way. Inevitably I wonder if its related to my previous mishap. My intention was to check that the response was the same on both channels, though for all I know I am going about it all wrong. This is prior to hooking up to a analyzer to run THD etc.
All in all, looking for the best way to proceed - big DOH moment, and sadly, just before crossing the finishing line.
with thanks,
Been working on this "F7 inspired" clone, which has been a very fruitful adventure. Just as I was finished biasing the amp, the GND on one of the power rails jumped out and shorted to the V- on the same (this is at the PSU board) as I saw it happen I quickly I was able to power down the amp before "anything" happened. But as we know sometimes things happen in instants.
Before you scold me, I know, shouldve done a better job of soldering and confirming, which I'll you I thought I did, but alas, we've all been there I suspect.
After the frustration and panic subisded, and I got back to and and carefully checked and powered up the amp again after repairing the loose wire. All checked out and it plays normally.
Now, I've hooked up to a signal generator and an oscilloscope. The Oscilloscope was connected to a 8R 25W resistor meanwhile the signal gen is run directly to the RCA inputs. I am running a 1000HZ signal @5V to the amp, and I am hearing a high pitched whine coming from the amp somewhere. If I raise the frequency, so does the pitch go up.
Admittedly, I didnt get to this step before my incident, and this is my first rodeo with the oscilloscope and generator in this way. Inevitably I wonder if its related to my previous mishap. My intention was to check that the response was the same on both channels, though for all I know I am going about it all wrong. This is prior to hooking up to a analyzer to run THD etc.
All in all, looking for the best way to proceed - big DOH moment, and sadly, just before crossing the finishing line.
with thanks,
Avoid more than 4 V peak input. Start low and slowly increase the level.
Do most testing with less input, like around 1 V peak.
Do most testing with less input, like around 1 V peak.
Last edited:
Ah that makes great sense - I dont know why I thought I had read that was a valid voltage to start. The scope sine wave is good, as far as my eyes can tell, attached is 1V @ 1000HZ, one channel each, so there is some mismatching with the channels, I defer to the pros if this is within tolerance. I dont have a before/after sparks flying to show for, however. Inverted one for clarity in the image.
Scope was given to me by someone getting rid of it from a defunct business, its like-new and ostensibly a nice unit despite my inexperience.
Heard that Rayma will stick to it.
Scope was given to me by someone getting rid of it from a defunct business, its like-new and ostensibly a nice unit despite my inexperience.
Heard that Rayma will stick to it.
Attachments
If you use 5% resistors, there could be as much as 20% difference in the amplitudes of the two channels.
Alway use 2% or better feedback resistors.
Or your scopes' probe adjustments could be off. Check both of them with the scope's calibration square wave.
You'll find that a triangle wave will be much better, for comparing amplitudes, and for checking the clipping point.
Alway use 2% or better feedback resistors.
Or your scopes' probe adjustments could be off. Check both of them with the scope's calibration square wave.
You'll find that a triangle wave will be much better, for comparing amplitudes, and for checking the clipping point.
I think you're like on the right track there, Rayma, I need to place another mouser order (which usually times to be about 24 hours after placint he last, or abou when the last arrives.) and I can order some replacement, might be worth swapping those out universally and better match them
For any orders, no minimum, DIGIKEY gives free shipping, if you mail in a check with your order and state tax.
I do this all the time. It does take longer to get the parts, because of mailing time from you to Digikey.
6. Shipping Charges.
Products Shipping from DigiKey's Warehouse. Except as otherwise provided on the Site, (1) shipping or freight charges and insurance will be paid by the customer*
* When a check or money order accompanies your order, DigiKey pays all shipping and insurance (our choice for method of shipping) to all addresses in the U.S. and Canada.
I do this all the time. It does take longer to get the parts, because of mailing time from you to Digikey.
6. Shipping Charges.
Products Shipping from DigiKey's Warehouse. Except as otherwise provided on the Site, (1) shipping or freight charges and insurance will be paid by the customer*
* When a check or money order accompanies your order, DigiKey pays all shipping and insurance (our choice for method of shipping) to all addresses in the U.S. and Canada.
Last edited:
Part of that mismatch is that the two waveforms on the display are offset from each other.
You can trim the remainder with a large value resistor in parallel with the feedback resistance
on one channel.
You can trim the remainder with a large value resistor in parallel with the feedback resistance
on one channel.