Just one or two more batches to go trough first sorting in +10 Hfe over 3000 of the little dudes.
Then VBE match of Hfe 400 for current sources and 550 for inputs and one more finer sorting.
Ones from Conrad's are pretty tight but have to order 3 batches to get PNP NPN overlap.
I am going to call it a day as frost bite is setting in
Then VBE match of Hfe 400 for current sources and 550 for inputs and one more finer sorting.
Ones from Conrad's are pretty tight but have to order 3 batches to get PNP NPN overlap.
I am going to call it a day as frost bite is setting in
way cool
So I connected 75k across Ext. RIAA, and started measuring. The first set of measurements was done with 10K across the input. The whole device is not shielded, but it seems like an awful lot of noise to me, or is this normal in this test setup?
channel A:
output: +/-400mV dc movement, scope shows ac noise of about 300mVpp
ext riaa:+/-300mV dc movement, scope shows ac noise of about 150mVpp
opamp pin6: moves all around the place between up to 1.9V
channel B:
output: +/-300mV dc movement, scope shows ac noise of about 300mVpp
ext riaa:+/-175mV dc movement, scope shows ac noise of about 200mVpp
opamp pin6: moves 30mVpp around -7.7Vdc
Then I replaced the resistor across the input to 18R and remeasured:
channel A:
output: +/-125mV dc movement, scope shows ac noise of about 50mVpp
ext riaa:+/-190mV dc movement, scope shows ac noise of about 2mVpp
opamp pin6: moves all around the place between up to 1.9V
channel B:
output: +/-200mV dc movement, scope shows ac noise of about 50mVpp
ext riaa:+/-10mV dc movement, scope shows ac noise of about 2Vpp
opamp pin6: moves 30mVpp around -7.7Vdc
Hi studiostevus, thanks for all the measurements. The DC movements are pretty high but should reduce over time. You will probably note that there is a lot of movement e.g. when you blow on the input transistors....
I am worried about the noise you are seeing. Can you trigger to this on the scope, do you see frequencies in the range of a few Mhz? And, did you consider putting the compensation caps in the PSU (because the noise could come from there)? Please check the assembly guide on how that can be done....
I am worried about the noise you are seeing. Can you trigger to this on the scope, do you see frequencies in the range of a few Mhz? And, did you consider putting the compensation caps in the PSU (because the noise could come from there)? Please check the assembly guide on how that can be done....
I put some smd caps of 470pf and 2.2nf in the recommended places. This is what I see on the scope. I can't get it triggered better than this (50mhz scope). Taken at 0.05us/div
Also I am not entirely sure that this is not a measurement error....
Also I am not entirely sure that this is not a measurement error....
An externally hosted image should be here but it was not working when we last tested it.
Took some more, this time channel B:
Before adding the caps in the psu
After adding caps in the psu
Differences: lower amplitude overall and after the caps were inserted it seems only a clean sinus remains
Before adding the caps in the psu
An externally hosted image should be here but it was not working when we last tested it.
After adding caps in the psu
An externally hosted image should be here but it was not working when we last tested it.
Differences: lower amplitude overall and after the caps were inserted it seems only a clean sinus remains
Finally.....
Hi all, finally I could lay my hands on a couple Paradise R3 boards that were genuinely oscillating . This may not be your idea of a "fun" event though
These two boards were happily oscillating at 87MHz. Yes, it was the amplifier, not the PSU. This may not be properly visible on a 50MHz scope, so the oscillations that studiostevus is seeing could be just that. (The scope I used is a 1GHz scope not mine, unfortunately)
They are probably caused by very high HFE of the transistors, but I really need to check before I can make that claim. But the oscillations can be fixed with 68pF caps across Collector-Base of Q18 and Q7. I will post pictures later and update the assembly guide accordingly.
Studiostevus, this is something you could try and let us know if that solved the problem!
Hi all, finally I could lay my hands on a couple Paradise R3 boards that were genuinely oscillating . This may not be your idea of a "fun" event though
These two boards were happily oscillating at 87MHz. Yes, it was the amplifier, not the PSU. This may not be properly visible on a 50MHz scope, so the oscillations that studiostevus is seeing could be just that. (The scope I used is a 1GHz scope
not mine, unfortunately)They are probably caused by very high HFE of the transistors, but I really need to check before I can make that claim. But the oscillations can be fixed with 68pF caps across Collector-Base of Q18 and Q7. I will post pictures later and update the assembly guide accordingly.
Studiostevus, this is something you could try and let us know if that solved the problem!
Almost feels like you robbed the same telecom toroidal store as I did, panty-hose style.
Wonderful! Crazy that it took so long.
I am one of the builders who has been sitting on their hands waiting for the remaining mysteries to be solved. It's allowed me to take my time testing transistors and over time many more design parameters have been shared with the builders.
I might just start stuffing the boards pretty soon. Thank you for continuing the work all this time. I certainly appreciate the diligence.
I am one of the builders who has been sitting on their hands waiting for the remaining mysteries to be solved. It's allowed me to take my time testing transistors and over time many more design parameters have been shared with the builders.
I might just start stuffing the boards pretty soon. Thank you for continuing the work all this time. I certainly appreciate the diligence.
Hi all, finally I could lay my hands on a couple Paradise R3 boards that were genuinely oscillating . This may not be your idea of a "fun" event though
These two boards were happily oscillating at 87MHz. Yes, it was the amplifier, not the PSU. This may not be properly visible on a 50MHz scope, so the oscillations that studiostevus is seeing could be just that. (The scope I used is a 1GHz scope
They are probably caused by very high HFE of the transistors, but I really need to check before I can make that claim. But the oscillations can be fixed with 68pF caps across Collector-Base of Q18 and Q7. I will post pictures later and update the assembly guide accordingly.
Studiostevus, this is something you could try and let us know if that solved the problem!
Hi Alfred, thanks for the suggestion.
Unfortunately that didn't solve it. I get clear oscillations at 3.6mhz, see picture (0.05us/div)
That should be PSU oscillations then, the frequency looks quite suspicious. Sorry I couldnt figure out thre frequency from your previous pictures... You may want to increase the compensation caps in the PSU from 2.2nF to 3.3nF, and the 470pF to 1nF. Please also try and disconnect the amplifier, and check the voltages at the shunt regulators to see if it oscillates there
thanks
thanks
Here we go, the regulator unloaded at 10mV/0.1us/div......
What type of TO220's are there in the PSU, also what type of TO92's?