Hi Keith, Notice that on the printed side of the Pass board there is a rectangular indication for Q200, Q201, Q100, and Q101. Further, notice that the corners of the rectangle are nipped off on one side. This should correspond to the the shape of the FET casings. This would be easy to miss with an older pair of eyes like mine. The orientation of the FETs should agree with the printed symbol on the board. My thought was that if you reversed one of the FETS it could throw off the balance between the FETS and cause a distorted or dead channel.
Wall warts are inconsistent in whether the center pin is positive or negative. It would be easy to conclude that the center pin was positive and wire it that way when, in fact, the center pin is negative. Yes, I have done that before.
Another thing about wall warts is that they may only output AC. It would be easy to conclude that an 18 volt wall wart was outputting 18 volts DC when, in fact, it was outputting 18 volts AC. Extreme distortion would be expected. Yes, I have made this mistake before.
A key voltage measurement would be to test the connections for proper polarity at the circuit board pads labeled "power." You need a volt meter for this. Further, it would be helpful to take an AC measurement at the power pads to verify that AC voltage is not present.
Did you include R4 and the indicator LED (D2)? Was the LED lit during the time you had the B-1 powered? If so, then the polarity of the power connections is apt to be correct. I would still check for AC at the power pads on the circuit board. Please let me know.
Addendum. Also note on the Pass circuit board that there is a line across the rectangle indicating D1. This line is toward one end of the rectangle. There should be a band around the D1 diode. The band on the diode must be oriented in agreement with the line drawn on the circuit board. If D1 is reversed then the gate voltages on the FETs are apt to be wrong. A distorted or dead channel would be expected.
B1 Buffer...only
Hi guys,
Great thread. Am new here.
Just would like to ask if any one has built the B1 as a buffer only similar to the good old MF X10D. Meaning no volume control needed.
If this has been done, would appreciate directing me to the right thread.
Thanks and regards,
JoeyGS
Hi guys,
Great thread. Am new here.
Just would like to ask if any one has built the B1 as a buffer only similar to the good old MF X10D. Meaning no volume control needed.
If this has been done, would appreciate directing me to the right thread.
Thanks and regards,
JoeyGS
Hi,
Can the B1 be used along with a light speed attenuator ? Please suggest.
Best regards,
Bins.
Can the B1 be used along with a light speed attenuator ? Please suggest.
Best regards,
Bins.
look up the previous threads on Lightspeed and DCB1 as well as here for info on combining the two strategies.
Thanks you so much lae2,
I was very careful when installing the FETS but I will inspect them again.
The wall wart thing I will look at more closely. It is a power supply from an older HP printer. I may have reversed the plug when I replaced the one that was on it as it was too large to fit anything I could find that would mount on the back of the chassis. On closer inspection of the wall wart I finally noticed a symbol that looks like an indication that I did make a bad assumption when trying to interpret which was positive and which was ground.
I appreciate your suggestions very much and will report back as soon as I can get you the information. I will be tied up the rest of the afternoon taking my lovely Wife to a medical appointment.
Thanks again,
Keith
I was very careful when installing the FETS but I will inspect them again.
The wall wart thing I will look at more closely. It is a power supply from an older HP printer. I may have reversed the plug when I replaced the one that was on it as it was too large to fit anything I could find that would mount on the back of the chassis. On closer inspection of the wall wart I finally noticed a symbol that looks like an indication that I did make a bad assumption when trying to interpret which was positive and which was ground.
I appreciate your suggestions very much and will report back as soon as I can get you the information. I will be tied up the rest of the afternoon taking my lovely Wife to a medical appointment.
Thanks again,
Keith
If the supply was AC it would account for the noise. More like a buzz really. You can always use a 9v battery as a low voltage/low current test.
Regards,
Regards,
By the way lae2,
I was very careful about the orientation of the diode.
I am a novice to building from scratch as this is my first project, but I have done parts replacement types of mods and some repair work when I could figure out the problem. I have also build speakers and x-overs. This just seems like a whole new world of possibilities to screw things up royally!
I did include the associated resistor and the LED but the LED never lit. That might just point back to the power polarity.
Thanks SO much!
Keith Lockwood
I was very careful about the orientation of the diode.
I am a novice to building from scratch as this is my first project, but I have done parts replacement types of mods and some repair work when I could figure out the problem. I have also build speakers and x-overs. This just seems like a whole new world of possibilities to screw things up royally!
I did include the associated resistor and the LED but the LED never lit. That might just point back to the power polarity.
Thanks SO much!
Keith Lockwood
If the LED never lit, it may be because the PS caps were never given the opportunity to charge.
Check the LED on its legs with test leads and a battery to see if it even works.
Check the LED on its legs with test leads and a battery to see if it even works.
That would be great if you could identify a reversed polarity. I suspect that the FETs might have survived. Music might be in your near future.
I recently tweaked my more than 15 year old equipment and dramatically improved the sound. I have tinnitus. It was totally surprising to me that my system went from irritating my tinnitus to soothing it. Thus, I am hooked on trying to build an extremely musical system that performs at low volume. Currently I am listening to Aerial 7Bs driven by Classe and Perreaux amplifiers. I plan to build one of the NP class a amps sometime this year. I doubt that my 86 DB 7Bs are going to work well with a 10 Watt amp. I may be coming to you for help with building a pair of high efficiency speakers. My fingers are crossed for your B-1.
I recently tweaked my more than 15 year old equipment and dramatically improved the sound. I have tinnitus. It was totally surprising to me that my system went from irritating my tinnitus to soothing it. Thus, I am hooked on trying to build an extremely musical system that performs at low volume. Currently I am listening to Aerial 7Bs driven by Classe and Perreaux amplifiers. I plan to build one of the NP class a amps sometime this year. I doubt that my 86 DB 7Bs are going to work well with a 10 Watt amp. I may be coming to you for help with building a pair of high efficiency speakers. My fingers are crossed for your B-1.
I got a chance to reverse the power lead and still nothing at all. At least there is no hum. no LED. I have to take off for the rest of the afternoon.
Thanks to everyone who has tried to help.
Thanks to everyone who has tried to help.
i am a newbie, but here are the things i would check:
polarity, AC and DC voltage out of the wall wart. What is the measured output voltage of the power supply? Some of those printer bricks are over 25V which is too much for the B1.
Check the polarity of the electrolytic caps. If they are backwards you will smell it fast.
You have verified the correct orientation of the Sk170 and the diode. The remaining parts are not directional.
Do you have a pot wired in correctly?
Check the imput and output wiring, as well as any ground you have.
Dont quit yet
On my pass B1 pcb the printed orientation /shape was incorrect.
From the B1 manual;
Check the data sheet for the fet you are using,the trace on the pcb on Q101 & Q201 should connect the drain (or #1 pin from left to right facing the flat side pins down)to the gate (or pin # 2)
Guys,
I got the matched FETS from Collin at Pass DIY when I bought the board. Are you telling me the board is printed wrong?
I will do further checking on the power supply. It is a 30V unit, but Nelson himself said that would be fine and I put 50V rated cans in to be on the safe and, um, "reliable" side
I am happy that you guys rally around with suggestions to help out when the **** hits the fan.
The bitch is that I went all out with a Goldpoint attenuator and a Bent Audio remote control stepper motor, which I haven't installed yet. I wanted to make sure it worked beforehand. There is over $350 right there. Man I am stupid.
Many thanks to everyone who keeps trying to help out. I won't give up yet. I guess I can't.
Thanks again,
Keith
I got the matched FETS from Collin at Pass DIY when I bought the board. Are you telling me the board is printed wrong?
I will do further checking on the power supply. It is a 30V unit, but Nelson himself said that would be fine and I put 50V rated cans in to be on the safe and, um, "reliable" side
I am happy that you guys rally around with suggestions to help out when the **** hits the fan.
The bitch is that I went all out with a Goldpoint attenuator and a Bent Audio remote control stepper motor, which I haven't installed yet. I wanted to make sure it worked beforehand. There is over $350 right there. Man I am stupid.
Many thanks to everyone who keeps trying to help out. I won't give up yet. I guess I can't.
Thanks again,
Keith
Sorry Keith,
according to the schematic the boards are showing the correct orientation, I should have looked more closely before posting, sorry for the wrong information.
Don't be so hard on yourself,keep a level head and you will get this B1 going.
according to the schematic the boards are showing the correct orientation, I should have looked more closely before posting, sorry for the wrong information.
Don't be so hard on yourself,keep a level head and you will get this B1 going.
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igwt,
No problem. You are just trying to be helpful and it is much appreciated.
I need to go back through some of the suggestions I have so far.
I am confused because today I didn't even get the distorted signal from the left channel after changing the power supply polarity.
I do have two sets of outputs wired, one of the sets has my high pass filter caps(VH Audio TFTF) to roll off the bottom of my main amp and the other set is for an output to a plate amp for a sub. I haven't finished the sub yet(I am sure I will come up with a new and crerative way to screw that up too). would it be possible that not shorting this second set of outputs is causing a problem?
Now I am wondering if my amp died in this fiasco. I need to QC that right away.
Thanks sincerely to everyone for their helpful input,
Keith
No problem. You are just trying to be helpful and it is much appreciated.
I need to go back through some of the suggestions I have so far.
I am confused because today I didn't even get the distorted signal from the left channel after changing the power supply polarity.
I do have two sets of outputs wired, one of the sets has my high pass filter caps(VH Audio TFTF) to roll off the bottom of my main amp and the other set is for an output to a plate amp for a sub. I haven't finished the sub yet(I am sure I will come up with a new and crerative way to screw that up too). would it be possible that not shorting this second set of outputs is causing a problem?
Now I am wondering if my amp died in this fiasco. I need to QC that right away.
Thanks sincerely to everyone for their helpful input,
Keith
Hey Keith, Inspired by IGWT I just got out my 370 fets, the b-1 board, and the 370 data sheet. I have not populated by Pass B-1 board yet. I plan to fry up some 2sk170s with point-to-point wiring before I risk the magical Pass stuff. As igwt has noted, the board drawings are correct for the 370s. On the other hand, if you are using 170's then it would be easy to be lead astray by the board markings. You can see the trace bridge between the source and gate of Q101/201 on both the top and bottom of the circuit board. The Linear Systems diagram for the 170 is more explicit than the Toshiba diagram. Regardless, if you are using Pass 370s, then the board markings are correct.
I recently retired a few HP ink jet printers to the recycling center but I kept the wall supplies. I just checked them. They are AC! Be certain that there is not a sine-wave symbol associated with the output voltage. If so, that would mean AC.
You might decide on a divide and conquer approach here. We need to know why that LED is not lit. As Chris suggested, you could test it with a 1k resistor and a 9V battery. Or, you could kill two birds in one stone and test the voltage at the + solder pad for the LED. With a 30 VDC supply you would expect to drop 27 VDC across R4 and 3VDC across the LED. Thus, a voltage reading from ground to the "+" pad for the LED should be about + 3 VDC. But that would be only if the LED was lit. With the LED not lit I would expect that you would measure +30 VDC at the "+" pad. If so, this would indicate that the LED was either open (bad) or reversed biased (installed backwards). If 0 VDC is measured at the "+" pad for the LED then I would bet you have a faulty power brick or an AC power brick. Flip your voltmeter to the AC setting and see if you get an AC reading between ground and the "+" solder pad for the LED. If we can just get that LED working we could then move on to the next battle.
I recently retired a few HP ink jet printers to the recycling center but I kept the wall supplies. I just checked them. They are AC! Be certain that there is not a sine-wave symbol associated with the output voltage. If so, that would mean AC.
You might decide on a divide and conquer approach here. We need to know why that LED is not lit. As Chris suggested, you could test it with a 1k resistor and a 9V battery. Or, you could kill two birds in one stone and test the voltage at the + solder pad for the LED. With a 30 VDC supply you would expect to drop 27 VDC across R4 and 3VDC across the LED. Thus, a voltage reading from ground to the "+" pad for the LED should be about + 3 VDC. But that would be only if the LED was lit. With the LED not lit I would expect that you would measure +30 VDC at the "+" pad. If so, this would indicate that the LED was either open (bad) or reversed biased (installed backwards). If 0 VDC is measured at the "+" pad for the LED then I would bet you have a faulty power brick or an AC power brick. Flip your voltmeter to the AC setting and see if you get an AC reading between ground and the "+" solder pad for the LED. If we can just get that LED working we could then move on to the next battle.
lae2,
The HP power supply indicates an output of 30V with a symbol that looks like a solid line with dashes below it. I guess I need to figure out if it is just dead although I did get the distorted output from the left channel yesterday and nothing at all today after changing the polarity, not even any hum. Maybe the supply is just dead.
I am getting exhausted now and will have to continue tomorrow. I have Lyme neuroborreliosis and it messes with me. I get fatigued very easily and get easily confused. this is in addition to having an ill tempered, almost turrets like condition.(that got me banned from Audio Asylum which is the best thing that ever happened to me)
I do have a fresh 15VDC wall wart that came from Bent Audio for use with the remote control motor. I know 15V isn't optimum but it should make something happen, shouldn't it?
Thanks everyone who has made suggestions.
I will start trying a few of the suggestions I haven't had time to implement yet.
I have looked at everything else I can think of. Maybe because I was trying to use caution and not get anything too hot I used my 25 watt iron instead of the 40 and perhaps I have a bunch of cold solder joints? The solder was flowing out nicely and I used what I thought was the best eutectic leaded solder I could get my paws on so I didn't think I would be overheating any components.
Time for a break. At least the amp ain't dead.
Thanks again,
Keith
The HP power supply indicates an output of 30V with a symbol that looks like a solid line with dashes below it. I guess I need to figure out if it is just dead although I did get the distorted output from the left channel yesterday and nothing at all today after changing the polarity, not even any hum. Maybe the supply is just dead.
I am getting exhausted now and will have to continue tomorrow. I have Lyme neuroborreliosis and it messes with me. I get fatigued very easily and get easily confused. this is in addition to having an ill tempered, almost turrets like condition.(that got me banned from Audio Asylum which is the best thing that ever happened to me)
I do have a fresh 15VDC wall wart that came from Bent Audio for use with the remote control motor. I know 15V isn't optimum but it should make something happen, shouldn't it?
Thanks everyone who has made suggestions.
I will start trying a few of the suggestions I haven't had time to implement yet.
I have looked at everything else I can think of. Maybe because I was trying to use caution and not get anything too hot I used my 25 watt iron instead of the 40 and perhaps I have a bunch of cold solder joints? The solder was flowing out nicely and I used what I thought was the best eutectic leaded solder I could get my paws on so I didn't think I would be overheating any components.
Time for a break. At least the amp ain't dead.
Thanks again,
Keith
Matching Q101 and Q100
I am up early this AM unable to sleep from fretting over whether I have enough ibuprofen to get my back through this impending weekend of shoveling snow. Worse, I woke up fretting over matching Q100 and Q101. Previously, it just seemed intuitively obvious to me that they should be matched but then I realized that I could not articulate why. In fact, why not intentionally mismatch the Idss's and place the higher Idss device in the Q101 postion and then match the current by adding a source resistor to Q101? That way, the currents could be matched and, at the same time, stability could be enhanced. My listening room varies from 64 deg F in Winter to 80 deg F in Summer. Maybe a source resistor on Q101 would not be a bad idea. If Q100 is intentionally mismatched to Q101 then Q100 could be without a source resistor and there would be one less source of noise. Plus, in a suspenders and belt move, I plan to connect heat sinks across Q100 and Q101 to enhance stability - not to dissipate heat but to equalize temperature.
Then, having recently read NP's writings on distortion, my insomnia was further driven by questioning if it would be better to match Q100 and Q101 for transconductance rather than for Idss. Transconductance, as I understand it, is not subject to circuit design. Do differences in the transconductances between Q100 and Q101 contirbute to non-linear distortion of the AC waveform?
Then I started worrying about the voltage divider at R2/R3. It seems that R103 anchors the gate of Q100 at a virtual ground. Might there be any benefit in tweaking R2/R3 to reflect the particular characteristics of Q100/101? NP uses the word "about" to describe the relationship of the source dc voltage to the gate dc voltage of Q100 and 1/2 Vcc. "About?" I imagine that "about" reflects the internal feedback of Q100 that sets Idss? Maybe R2/R3 could be tweaked for symmetrical clipping and, thus, set the operating point in the most linear region? I suppose that Spice is in my future. I need to take a pill.
I am up early this AM unable to sleep from fretting over whether I have enough ibuprofen to get my back through this impending weekend of shoveling snow. Worse, I woke up fretting over matching Q100 and Q101. Previously, it just seemed intuitively obvious to me that they should be matched but then I realized that I could not articulate why. In fact, why not intentionally mismatch the Idss's and place the higher Idss device in the Q101 postion and then match the current by adding a source resistor to Q101? That way, the currents could be matched and, at the same time, stability could be enhanced. My listening room varies from 64 deg F in Winter to 80 deg F in Summer. Maybe a source resistor on Q101 would not be a bad idea. If Q100 is intentionally mismatched to Q101 then Q100 could be without a source resistor and there would be one less source of noise. Plus, in a suspenders and belt move, I plan to connect heat sinks across Q100 and Q101 to enhance stability - not to dissipate heat but to equalize temperature.
Then, having recently read NP's writings on distortion, my insomnia was further driven by questioning if it would be better to match Q100 and Q101 for transconductance rather than for Idss. Transconductance, as I understand it, is not subject to circuit design. Do differences in the transconductances between Q100 and Q101 contirbute to non-linear distortion of the AC waveform?
Then I started worrying about the voltage divider at R2/R3. It seems that R103 anchors the gate of Q100 at a virtual ground. Might there be any benefit in tweaking R2/R3 to reflect the particular characteristics of Q100/101? NP uses the word "about" to describe the relationship of the source dc voltage to the gate dc voltage of Q100 and 1/2 Vcc. "About?" I imagine that "about" reflects the internal feedback of Q100 that sets Idss? Maybe R2/R3 could be tweaked for symmetrical clipping and, thus, set the operating point in the most linear region? I suppose that Spice is in my future. I need to take a pill.
Could have, my hooking up the wall wart with the polarity inverted be like installing the two big caps backward?
Does it seem likely now that the big caps C1 and C2 are now done for?
Looking at a diagram of the board it seems that it would be just like installing them backward.
Keith Lockwood
Does it seem likely now that the big caps C1 and C2 are now done for?
Looking at a diagram of the board it seems that it would be just like installing them backward.
Keith Lockwood
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