Ok, is it this one; https://se.rs-online.com/web/p/solder-flux-removers/1908290?
Yeah I read that about the select switch, thanks for the reminder though.
The PCB that I make my own I use aceton to clean the flux of, but then I don't have to worry about silkscreen or anything like that. Isopropyl alcohol (IPA), also avalaible from RS, may be a better option. Can i use this instead? Isopropyl should be avalaible at my local pharmacy, think I'll get some for this project.
Quick update re the LSK389B devices. Some builders have struggled to secure these as they have not been generally avaiablle at the major distributors.
TI recently introduced the JFE2140 dual JFET which has been positioned as an alternative to the LSK389/489 devices. The TI devices are SOIC and pin for pin replacement of the LSK389/489 (note the PCB accepts the metal can or the SOIC packages).
If you decide to build the X-Altra MC/MM phono preamp, you can use the TI devices for the same or slightly better performance.
They are avaiablle at Mouser and the Part # is 595-JFE2140DR
Here is the link to the TI data sheet https://www.ti.com/product/JFE2140
TI recently introduced the JFE2140 dual JFET which has been positioned as an alternative to the LSK389/489 devices. The TI devices are SOIC and pin for pin replacement of the LSK389/489 (note the PCB accepts the metal can or the SOIC packages).
If you decide to build the X-Altra MC/MM phono preamp, you can use the TI devices for the same or slightly better performance.
They are avaiablle at Mouser and the Part # is 595-JFE2140DR
Here is the link to the TI data sheet https://www.ti.com/product/JFE2140
Replying my own mail. Kindly ignore it. Board is OK. Sorry for any misunderstanding.
Going through checks and debugging of Phono preamp.. Here's what I have: Hope you can help and I'll keep searching!
1)The initial check power supply measurements are to specification!
With all devices mounted:
1) I now have +5.6V and +20.V at power supply???( initial test they were 8V and 23V)
2) I have spot on +15v/-15V
3) I have+10V low noise reference +/- 100mv
4) Both of 10VRC points are 9.82V???
5) I have -5VRC is -5V +/- 50mv
6) R61 and R82 is over 5V, should be 3V problem?
7) U26 and U10 pin 7 are good
8) U27 pin 6 I get fluctuation from low MV to 170MV so there is a problem here
9) I have 20mv at right MC input but 80MV at Left MC input Problem Here
Note - I didn't match Q1,2,3,4 - Checking the few extra 851's vs 951's that I have, there is 200 plus HFE span. I assume this shouldn't cause the above problems but I can pull these and attempt to match.. I have 6 of each!
Add/Edit - I installed JFE2140DR
1)The initial check power supply measurements are to specification!
With all devices mounted:
1) I now have +5.6V and +20.V at power supply???( initial test they were 8V and 23V)
2) I have spot on +15v/-15V
3) I have+10V low noise reference +/- 100mv
4) Both of 10VRC points are 9.82V???
5) I have -5VRC is -5V +/- 50mv
6) R61 and R82 is over 5V, should be 3V problem?
7) U26 and U10 pin 7 are good
8) U27 pin 6 I get fluctuation from low MV to 170MV so there is a problem here
9) I have 20mv at right MC input but 80MV at Left MC input Problem Here
Note - I didn't match Q1,2,3,4 - Checking the few extra 851's vs 951's that I have, there is 200 plus HFE span. I assume this shouldn't cause the above problems but I can pull these and attempt to match.. I have 6 of each!
Add/Edit - I installed JFE2140DR
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Thank you Bosai!
I traced the fluctuation on pin 6b U27 and found it U26
When compare U26 to U19, this is what I see - P1,2 and 3 = 10V on both
P4 -15V both
P5 0V both
P6 U19 = 0.3mv and U26 = 0.8mv
P7 U19 = -15mv and U26 = wild fluctuation from low mv to -2.5V
P8 =15V both.
Fluctuation is of course also at pin 3 U27
I traced the fluctuation on pin 6b U27 and found it U26
When compare U26 to U19, this is what I see - P1,2 and 3 = 10V on both
P4 -15V both
P5 0V both
P6 U19 = 0.3mv and U26 = 0.8mv
P7 U19 = -15mv and U26 = wild fluctuation from low mv to -2.5V
P8 =15V both.
Fluctuation is of course also at pin 3 U27
Going through checks and debugging of Phono preamp.. Here's what I have: Hope you can help and I'll keep searching!
1)The initial check power supply measurements are to specification!
With all devices mounted:
1) I now have +5.6V and +20.V at power supply???( initial test they were 8V and 23V) I assume these are the inputs to the 7815 regs as measured wrt 0V - if so the voltages are ok although a little on the low side on the V- side where you measure +5.6V.
2) I have spot on +15v/-15V - OK - that's good
3) I have+10V low noise reference +/- 100mv - Good
4) Both of 10VRC points are 9.82V??? - this is after the 47 Ohm resistors (R63 and R78) - Good.
5) I have -5VRC is -5V +/- 50mv - this is ok - good. What about the +5V supply?
6) R61 and R82 is over 5V, should be 3V problem? - this is ok - the Id vs Vsource is a bit higher on the JFE2140
7) U26 and U10 pin 7 are good - I assume you mean U26 and U19 pin 7 - should both be in range of -250 mV to +250mV
8) U27 pin 6 I get fluctuation from low MV to 170MV so there is a problem here - Check that R52 and R56 are soldered in correctly. If either of these has an unsoldered side, you will get the problems you mention. If you have used NE5534A in this location, make sure C96 is installed - if not, the opamp will be oscillating.
9) I have 20mv at right MC input but 80MV at Left MC input Problem Here. That is on the high side. Check that you have C9, C10 and C24 and C25 installed the right way around. If one of them is reversed (or you have a very leaky cap) you will get a large offset on the input. Also check that R11, R12 and R23 and R24 are the correct values and correctly soldered down. Can you open U28 and U29 and measure the input offset, then close U28 and U29 and remeasure it. Also, what is the voltage you are measuring at U28 and U29 after they are closed?
Note - I didn't match Q1,2,3,4 - Checking the few extra 851's vs 951's that I have, there is 200 plus HFE span. I assume this shouldn't cause the above problems but I can pull these and attempt to match.. I have 6 of each! Should be ok. Ideally you want the Vbe's of the transistors to be within 15mV of each other and then the hFE's to be closely matched. The input offset servo (U1) can servo out quite large offsets if you find you cannot get a resonalble close match. The 80mV offset is the highest I've seen which makes me tend to believe it might be an issue on the base decoupling caps or perhaps the servo circuit.
Add/Edit - I installed JFE2140DR
Is this with the input short circuited or open? If the input is open, you might be picking up 60Hz noise. Can you put a scope on it?
1)The initial check power supply measurements are to specification!
With all devices mounted:
1) I now have +5.6V and +20.V at power supply???( initial test they were 8V and 23V) I assume these are the inputs to the 7815 regs as measured wrt 0V - if so the voltages are ok although a little on the low side on the V- side where you measure +5.6V.
2) I have spot on +15v/-15V - OK - that's good
3) I have+10V low noise reference +/- 100mv - Good
4) Both of 10VRC points are 9.82V??? - this is after the 47 Ohm resistors (R63 and R78) - Good.
5) I have -5VRC is -5V +/- 50mv - this is ok - good. What about the +5V supply?
6) R61 and R82 is over 5V, should be 3V problem? - this is ok - the Id vs Vsource is a bit higher on the JFE2140
7) U26 and U10 pin 7 are good - I assume you mean U26 and U19 pin 7 - should both be in range of -250 mV to +250mV
8) U27 pin 6 I get fluctuation from low MV to 170MV so there is a problem here - Check that R52 and R56 are soldered in correctly. If either of these has an unsoldered side, you will get the problems you mention. If you have used NE5534A in this location, make sure C96 is installed - if not, the opamp will be oscillating.
9) I have 20mv at right MC input but 80MV at Left MC input Problem Here. That is on the high side. Check that you have C9, C10 and C24 and C25 installed the right way around. If one of them is reversed (or you have a very leaky cap) you will get a large offset on the input. Also check that R11, R12 and R23 and R24 are the correct values and correctly soldered down. Can you open U28 and U29 and measure the input offset, then close U28 and U29 and remeasure it. Also, what is the voltage you are measuring at U28 and U29 after they are closed?
Note - I didn't match Q1,2,3,4 - Checking the few extra 851's vs 951's that I have, there is 200 plus HFE span. I assume this shouldn't cause the above problems but I can pull these and attempt to match.. I have 6 of each! Should be ok. Ideally you want the Vbe's of the transistors to be within 15mV of each other and then the hFE's to be closely matched. The input offset servo (U1) can servo out quite large offsets if you find you cannot get a resonalble close match. The 80mV offset is the highest I've seen which makes me tend to believe it might be an issue on the base decoupling caps or perhaps the servo circuit.
Add/Edit - I installed JFE2140DR
Is this with the input short circuited or open? If the input is open, you might be picking up 60Hz noise. Can you put a scope on it?
Excellent, many thanks!
1) Yes, at the input of the 7815 reg's wrt 0: 5.8V and 22V now, plugged into wall. I was plugged into variable transformer!
2)✔
3)✔
4)✔ Yes, after R63 and R78
5)✔ I also have +5V
6)✔
7) I Said the wrong IC's - U26 has the fluctuation on pin 7 and with DVM set to hold it rises to -14.5V and if I watch long enough it will settle for short periods..
All parts appear to be installed properly, correct values, no missing solder joints etc..
will investigate the rest - Waiting for part for soldering iron..
8) U27 pin 3 and 6 sees the fluctuation but is it carried down from U26 - U26 is OPA1641 without C96 installed
1) Yes, at the input of the 7815 reg's wrt 0: 5.8V and 22V now, plugged into wall. I was plugged into variable transformer!
2)✔
3)✔
4)✔ Yes, after R63 and R78
5)✔ I also have +5V
6)✔
7) I Said the wrong IC's - U26 has the fluctuation on pin 7 and with DVM set to hold it rises to -14.5V and if I watch long enough it will settle for short periods..
All parts appear to be installed properly, correct values, no missing solder joints etc..
will investigate the rest - Waiting for part for soldering iron..
8) U27 pin 3 and 6 sees the fluctuation but is it carried down from U26 - U26 is OPA1641 without C96 installed
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I have the correct IC's in right positions.. My correction to my mistake above made it confusing..
U19(LM4562) pin 7 has -15mv on it.. U26(LM4562) pin 7 fluctuates, it take about one minute for that to start. It looks normal at power up and the voltage slowly drops to around -30mv and then eventually it shoots up and down in about 5 second cycles..
U19(LM4562) pin 7 has -15mv on it.. U26(LM4562) pin 7 fluctuates, it take about one minute for that to start. It looks normal at power up and the voltage slowly drops to around -30mv and then eventually it shoots up and down in about 5 second cycles..
Joel,
can you measure the voltage at the source of U21 and U20 and then the voltage across R82 and R61.
In the meantime please carefully check the soldering joints around U26 - especially R76, C86, and R71 and R72.
Note also that R77 and C86 are important for AC stability and these soldering connections must be checked.
can you measure the voltage at the source of U21 and U20 and then the voltage across R82 and R61.
In the meantime please carefully check the soldering joints around U26 - especially R76, C86, and R71 and R72.
Note also that R77 and C86 are important for AC stability and these soldering connections must be checked.
I found something. U26 pin 7, I press the probe down with a little force on the pin and the voltage is stable at low MV. when release pressure it goes high. I touched up the solder on the U26 and same problem.. I'll look for bad solder joints.
V across R82 = 5.4 and 5.2V across R61.
Thank you. you got me on the right path!
V across R82 = 5.4 and 5.2V across R61.
Thank you. you got me on the right path!