Hi,
I suspect that the higher capacitance is due to a larger area of junction.
It may also be that the speed of turn off is inversely proportional to capacitance or area.
If this is the case then all diodes that have a large capacitance will have a lower Vf at the same required current.
You choose which seems more important.
I suspect that the higher capacitance is due to a larger area of junction.
It may also be that the speed of turn off is inversely proportional to capacitance or area.
If this is the case then all diodes that have a large capacitance will have a lower Vf at the same required current.
You choose which seems more important.
Sorry, I just realized I made an error in converting uA to mA, which made me think that the On Semi has higher reverse current than the IR. Actually the On Semi has a lower typical reverse current of .02 mA @ 20 V 125 deg.C compared to .08 mA for the IR under the same test conditions. So it looks like the On Semi is superior to the IR in most of the specs except the junction capacitance where it has a typical value of 77 pF compared to only 35 pF for the IR. What exactly is the detrimental effect of the higher capacitance?
I've finally gotten around to testing the input and output voltages of the +/-15 V regs under four different scenarios:
1. Quiescent (no activity);
2. D/A to A/D loopback of one stereo pair (2 output and 2 input channels in use);
3. D/A to A/D loopback of two stereo pairs (4 output and 4 input channels in use);
4. D/A to A/D loopback of three stereo pairs, and Media Player output on one more stereo pair (8 output and 6 input channels in use).
For the loopback, I ran several instances of RightMark Audio Analyzer (each instance being one stereo pair). The amazing thing is that I got the same readings in all the four tests! For the +15 V reg, the input was always 23 V and the output was always 14.91 V. For the -15 V reg, the input was always -23 V and the output was always -15.02 V. I used a BK Precision 2408 DMM for testing. The readings were consistent all throughout. I would watch the meter for a minute and it wouldn't fluctuate!
It seems I don't really have a voltage sag problem. Do I still need to test further with my scope?
Next game plan: I want to try putting in the Schottky replacement diodes to see what their effect would be on the readings. This, without installing the LDO regs yet. The LDO regs have a lower maximum input voltage of 26 V compared to 35 V for the stock regs. Before installing the LDO regs, I want to make sure that the input voltage with the Schottky diodes installed does not exceed 26 V.
Please let me know what you think. Thanks!
I've finally gotten around to testing the input and output voltages of the +/-15 V regs under four different scenarios:
1. Quiescent (no activity);
2. D/A to A/D loopback of one stereo pair (2 output and 2 input channels in use);
3. D/A to A/D loopback of two stereo pairs (4 output and 4 input channels in use);
4. D/A to A/D loopback of three stereo pairs, and Media Player output on one more stereo pair (8 output and 6 input channels in use).
For the loopback, I ran several instances of RightMark Audio Analyzer (each instance being one stereo pair). The amazing thing is that I got the same readings in all the four tests! For the +15 V reg, the input was always 23 V and the output was always 14.91 V. For the -15 V reg, the input was always -23 V and the output was always -15.02 V. I used a BK Precision 2408 DMM for testing. The readings were consistent all throughout. I would watch the meter for a minute and it wouldn't fluctuate!
It seems I don't really have a voltage sag problem. Do I still need to test further with my scope?
Next game plan: I want to try putting in the Schottky replacement diodes to see what their effect would be on the readings. This, without installing the LDO regs yet. The LDO regs have a lower maximum input voltage of 26 V compared to 35 V for the stock regs. Before installing the LDO regs, I want to make sure that the input voltage with the Schottky diodes installed does not exceed 26 V.
Please let me know what you think. Thanks!
Hi,
if you have 23V as Vin, Then I suspect you don't have a problem with supply voltage.
Yes, you do need to measure the ripple on the input.
If the ripple + regulator Vdrop uses up the 8V of headroom you have measured then the regulators will drop out.
The worst case conditions should be replicated; Lowest mains voltage and lowest load impedance/highest output current
if you have 23V as Vin, Then I suspect you don't have a problem with supply voltage.
Yes, you do need to measure the ripple on the input.
If the ripple + regulator Vdrop uses up the 8V of headroom you have measured then the regulators will drop out.
The worst case conditions should be replicated; Lowest mains voltage and lowest load impedance/highest output current
I finally learned how to use my scope. I saw the ripple voltage on the input to be about 3 V. The dropout voltage of the existing regs is 2 V. So it seems that the 8 V headroom of the input voltage is enough.
My probe has 1X and 10X settings. I used the 10X setting as I read that it's the most commonly used. Was this the right choice?
I was afraid to use the 1X setting as I read that it has a higher capacitance which adversely affects the operation of most circuits. Would it have been unsafe to use 1X?
I saw the ripple voltage on the input to be about 3 V. The dropout voltage of the existing regs is 2 V. So it seems that the 8 V headroom of the input voltage is enough.My probe has 1X and 10X settings. I used the 10X setting as I read that it's the most commonly used. Was this the right choice?
I was afraid to use the 1X setting as I read that it has a higher capacitance which adversely affects the operation of most circuits. Would it have been unsafe to use 1X?
Hi,
3Vpp ripple is quite high when just a few mA are drawn, but that is the downside of the doubler.
Yes, use the 10x or even 100x for best results with a scope.
Only use the 1x when the signal voltage becomes too low to measure.
The 10M and low cap produces the least effect on the operation of the circuit being probed.
If you are taking this hobby seriously then buying fixed 10X and fixed 100x probes would be a good investment. Keep the universal 1x/10x for day to day use.
3Vpp ripple is quite high when just a few mA are drawn, but that is the downside of the doubler.
Yes, use the 10x or even 100x for best results with a scope.
Only use the 1x when the signal voltage becomes too low to measure.
The 10M and low cap produces the least effect on the operation of the circuit being probed.
If you are taking this hobby seriously then buying fixed 10X and fixed 100x probes would be a good investment. Keep the universal 1x/10x for day to day use.
I have a 1010 too and I wonder why it has such a lousy psu. Why the hell use a 9V Tranny?
I started to desolder the whole psu rubbish and tomorrow (hopefully) I will draw a schematic of it and find what is connected how. I will post my findings here.
Initially I´m thinking about tinkering my own LM317/337 preregulator/regulator psu.
I started to desolder the whole psu rubbish and tomorrow (hopefully) I will draw a schematic of it and find what is connected how. I will post my findings here.Initially I´m thinking about tinkering my own LM317/337 preregulator/regulator psu.
SmellOfPoo said:I have a 1010 too and I wonder why it has such a lousy psu. Why the hell use a 9V Tranny?
I'm very interested in what you find out!
My next mod on the PSU is to replace the caps with better quality ones. But first I would like to understand the function of the caps. The PSU is located in a small area of the 1010's D/A board:
http://home.ca.rr.com/mtl777/Files1/Delta 1010 D-A Board PSU.jpg
To aid our discussion, I made a crude diagram of the PSU layout, with the red lines depicting the connections:
http://home.ca.rr.com/mtl777/Files1/Delta 1010 PSU Layout.jpg
The layout is by no means complete. Just enough detail for my questions which are:
1. What is the function of C14 and C17? Are these the so-called "booster caps"?
2. What is the function of C12? Is it the smoothing cap for the input voltage to the +15V reg?
3. What is the function of C13? Is it the smoothing cap for the output voltage of the +15V reg?
I would also like to know what specs to look for when buying the replacement caps. (Note, I will replace only the big caps, not the SMD's.) Are ultra-low impedance and high ripple current recommended for all of these caps? (I'm considering Rubycon ZA/ZL/ZLH and Panasonic FM.)
Thanks!
Here is the top layer with marked bottom traces. Yellow dots mark the connections to the underlying planes. Would be nice if s.o. could draw the schematic out of it, I got no time at all and I will not keep the psu.
An externally hosted image should be here but it was not working when we last tested it.
Thanks for the picture update!
Do the +/-15V regs of your 1010 also have a 1N5818 diode connected across their ground and output pins? My regs have this diode. I want to replace my regs with LDO type (LM2940CT-15 and LM2990T-15) but I'm not sure what to do with the 1N5818 diodes. Should I simply attach them to the replacement LDO regs in exactly the same way they are attached to the existing regs? I'm worried that there might be some incompatibility between these diodes and the LDO regs. Is this something to worry about? Looking at it from the principle of operation of a voltage regulator (i.e., it receives an input voltage, has a ground connection, and outputs a regulated voltage), it seems that there should be no problem since the regs, although of different type, have the same principle of operation. But I want to be sure, just in case you more experienced experts know better or have ever encountered a problem with this.
Thanks!
Do the +/-15V regs of your 1010 also have a 1N5818 diode connected across their ground and output pins? My regs have this diode. I want to replace my regs with LDO type (LM2940CT-15 and LM2990T-15) but I'm not sure what to do with the 1N5818 diodes. Should I simply attach them to the replacement LDO regs in exactly the same way they are attached to the existing regs? I'm worried that there might be some incompatibility between these diodes and the LDO regs. Is this something to worry about? Looking at it from the principle of operation of a voltage regulator (i.e., it receives an input voltage, has a ground connection, and outputs a regulated voltage), it seems that there should be no problem since the regs, although of different type, have the same principle of operation. But I want to be sure, just in case you more experienced experts know better or have ever encountered a problem with this.
Thanks!
Mine has no diodes across ground and ouput. But there´s nothing to worry about; those diodes are for protection against current backflow through the regulator. When the supply is turned off, the caps unload and a part of this current would flow back through the regulator if there wasn´t the diode conducting to the input.
Usually there is another diode in blocking direction across input and output. If for some reason the output voltage should be greater than input voltage the regulator would be killed immediately and eventually short-circuited. In such a case the input voltage would be conducted to the circuit behind the regulator what could cause even more harm.
Usually there is another diode in blocking direction across input and output. If for some reason the output voltage should be greater than input voltage the regulator would be killed immediately and eventually short-circuited. In such a case the input voltage would be conducted to the circuit behind the regulator what could cause even more harm.
Thanks, I'm greatly relieved to know that there's nothing to worry about!
BTW, are ultra low impedance, high ripple current rated caps the best ones to buy for replacing all those big caps in the PSU? Is there something to watch out for, such as the impedance or ESR being too low?
Thanks again!
BTW, are ultra low impedance, high ripple current rated caps the best ones to buy for replacing all those big caps in the PSU? Is there something to watch out for, such as the impedance or ESR being too low?
Thanks again!
Only change the caps after the regulator outputs fot something better (C61, C23, C19, C13). The caps before the regulators are not "seen" by the DACs and OPAMPs.
In case of C61, which seems to be for the digital section of the DACs, use some good standard capactor instead of ultra low esr one. There could be unwanted side effects when the impedance of capacitor is too low.
Would be great if you could figure out the schematic ... I hate that kind of job.
In case of C61, which seems to be for the digital section of the DACs, use some good standard capactor instead of ultra low esr one. There could be unwanted side effects when the impedance of capacitor is too low.
Would be great if you could figure out the schematic ...
I hate that kind of job.
Pana FM is fine. Larger values on C14 / C17 will not affect the function of the voltage doubler.
http://en.wikipedia.org/wiki/Voltage_multiplier
http://en.wikipedia.org/wiki/Voltage_multiplier
Here's a thread I found on the web discussing mods on the Delta 1010. I compiled and shortened it into Word doc format for easier reading. This is the discussion that motivated me to modify my 1010.
http://home.ca.rr.com/mtl777/Files1/Delta 1010 Mods.doc
Somewhere in the discussion, JohnR is talking about "boost caps":
"The +/- 15V power supply for the op amps in the breakout box is a bit of a joke. If you rectify 9V ac you usually only get around 12-13Vdc so there's a capacitor-based voltage doubler to boost the voltage high enough to feed to a pair of 15V regulators. Unfortunately the boost caps are undersized so the voltage isn't boosted high enough for the regulators to do anything. This means the op amps are being fed a ripply, noisy, unregulated power supply."
Which caps is he referring to as the boost caps? Are they C14 and C17? Please help to identify these boost caps as I want to try increasing their value.
Thanks!
http://home.ca.rr.com/mtl777/Files1/Delta 1010 Mods.doc
Somewhere in the discussion, JohnR is talking about "boost caps":
"The +/- 15V power supply for the op amps in the breakout box is a bit of a joke. If you rectify 9V ac you usually only get around 12-13Vdc so there's a capacitor-based voltage doubler to boost the voltage high enough to feed to a pair of 15V regulators. Unfortunately the boost caps are undersized so the voltage isn't boosted high enough for the regulators to do anything. This means the op amps are being fed a ripply, noisy, unregulated power supply."
Which caps is he referring to as the boost caps? Are they C14 and C17? Please help to identify these boost caps as I want to try increasing their value.
Thanks!
C14 / C17 are the ones ...
But if you can wait a couple of days I will finish my psu & I post the details. It will omit the whole original psu including transformer. The opamp supply will be something like this:
The ADC / DAC supply be be quite the same with each only the positive half.
But if you can wait a couple of days I will finish my psu & I post the details. It will omit the whole original psu including transformer. The opamp supply will be something like this:
An externally hosted image should be here but it was not working when we last tested it.
The ADC / DAC supply be be quite the same with each only the positive half.
That looks very good, but I'm not really knowledgable enough to do a complete PSU overhaul as I've had no formal electronics training. I'm just handy with soldering and have learned a little electronics by browsing the web but that's about it. I will have to be contented with simple component changes for now. But please do post your final work for future reference.
Speaking of simple mods, will it be alright to replace the caps C14, C17, C22, C60, C18, and C12 with Panasonic FM or FC? It may not make a perceivable difference in the sound, but I just want to replace the original caps as I think they're probably not very good quality.
Thanks!
Speaking of simple mods, will it be alright to replace the caps C14, C17, C22, C60, C18, and C12 with Panasonic FM or FC? It may not make a perceivable difference in the sound, but I just want to replace the original caps as I think they're probably not very good quality.
Thanks!
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