TESORO GOLDEN SABRE

[kt315]

ZIP it. open ADVANCED reply form and attach the file.

[Mr.Jaick]

Please post the schematic you made!

how can i send the schematic sheet in altium format here?
the schematic that i made the pcb out of it is bit deference but i turned it into the original one from Dan Bowers pdf
it's the original now

[Mr.Jaick]

Voltages you have are fine. They do not need to be exact.
Good checking Voltages On the pins of the Chips.

The RX phase shift is NOT important at this stage of troubleshooting. Also I played a lot with the TGSL I built and this circuit actually works very well with almost any phase shift.
This is NOT the problem yet.

The Problem is in the DISC Circuit as I have pointed out in previous posts.

i think i discovered the problem somewhere
take a look at these pictures:

all signals reference is at the middle X axis of the scope screen.
disc pot and GB pot connected but disc switch is not connected

1- TX signal (2v/div , 10us t/dev)


2- U102(LM393) pin 6 which is inverting input , GB pot at mid range (2v/div , 10us t/dev)
output of GB section is clean square wave for the Jfet(TR5) , no problem


3- U101(LF353) pin 6 , the problem (5v/div , 20us t/dev)
actually i accidentally switched the first op_amp of LF353 with second one when i was designing the PCB, my bad but it doesn't effect anything, does it??


4- middle pin of 100k disc pot, at min (2v/div , 10us t/dev)
it's simply the TX signal from that 3.3k resistor


5- U102 pin 2 which is the inverting input of comparator (2v/div , 10us t/dev)


6- U101 pin 7 , this is the problem for that flat DC voltage (2v/div , 10us t/dev)


7- middle pin of disc pot, at max , obviously it feeds that DC signal form U101 into next stage(comparator) when i turn the disc pot to MAX and cause the problem (2v/div , 10us t/dev)


and to notice i used PN4391 instead of J107 , at that time i only found this FET and didn't know about BF245 so maybe i would change it in advance

[waltr]

i've seen some people has about -6 , i think it depends on IC chips consumption

i checked the voltage +8 and -5 on all the chips, they are fine
the pcb is a custom metalized double sided , i ordered from a pcb manufacturer
but i'll check everything again, thank you

thanks sir i'll try schotky diodes , it will help
the signal occupies 6.9 blocks on the screen, so 360/6.9 = 52 degrees for each horizontal block, and each block has divided by 5 sections so each of them means 10 degrees of phase shift and the phase shift between tx and rx is 2 sections so i think it's fine, isn't it?

Voltages you have are fine. They do not need to be exact.
Good checking Voltages On the pins of the Chips.

The RX phase shift is NOT important at this stage of troubleshooting. Also I played a lot with the TGSL I built and this circuit actually works very well with almost any phase shift.
This is NOT the problem yet.

The Problem is in the DISC Circuit as I have pointed out in previous posts.

[Nandor]

Please post the schematic you made!

[Mr.Jaick]

You can also try to use ICL7660 to make negative voltage for the circuit. You need less components and it makes -7.48volts loaded, works splendid!

Do not forget that you have very asymmetrical voltages for the IC's that means that the negative peaks of the signals get clipped. I really believe that this is your problem.

regards

yes i have a bit asymmetrical waveform , and negative peaks get clipped a little
and yes something is wrong with my setup , i'll try to figure out
regards

[Mr.Jaick]

Mr Jaick the phase shift between your Tx and Rx does not seem to be 20deg, there is obviously much less than that maybe 10-15 after seeing the picture you posted.

About the negative voltage, try Schotky diodes those have less on resistance and pair those transistors to have equal hFE and also low ESR electric capacitor is a must! The best I have made was around -6.7volts.

Waltr has some really good points also!

thanks sir i'll try schotky diodes , it will help
the signal occupies 6.9 blocks on the screen, so 360/6.9 = 52 degrees for each horizontal block, and each block has divided by 5 sections so each of them means 10 degrees of phase shift and the phase shift between tx and rx is 2 sections so i think it's fine, isn't it?

[Mr.Jaick]

I got this backwards. The Disc pot goes into the Negative comparator input so output high when input low.

Thanks for details on scope pictures.
The signal at the wiper of the Disc pot is moving up as you turn the pot. This is Not correct and why the comparator output goes to a solid high level.
What should happen is the signal should become more and more delayed as you turn the pot.

Did you CHECK the Voltages on the opamp and comparator? -4.8 is lower than typical but should work.
Re-check the Disc pot connections and component values. Check all soldering and since you have a hand made double sided PCB ensure connection are made TOP & BOTTOM where needed.

i checked the voltage +8 and -5 on all the chips, they are fine
the pcb is a custom metalized double sided , i ordered from a pcb manufacturer
but i'll check everything again, thank you

[Mr.Jaick]

i've seen some people has about -6 , i think it depends on IC chips consumption

[Nandor]

You can also try to use ICL7660 to make negative voltage for the circuit. You need less components and it makes -7.48volts loaded, works splendid!

Do not forget that you have very asymmetrical voltages for the IC's that means that the negative peaks of the signals get clipped. I really believe that this is your problem.

regards

[Nandor]

Mr Jaick the phase shift between your Tx and Rx does not seem to be 20deg, there is obviously much less than that maybe 10-15 after seeing the picture you posted.

About the negative voltage, try Schotky diodes those have less on resistance and pair those transistors to have equal hFE and also low ESR electric capacitor is a must! The best I have made was around -6.7volts.

Waltr has some really good points also!

[waltr]

This is a Comparator, When pin 2 Voltage is higher than ground out is high. When lower than ground, output low.

I got this backwards. The Disc pot goes into the Negative comparator input so output high when input low.

Thanks for details on scope pictures.
The signal at the wiper of the Disc pot is moving up as you turn the pot. This is Not correct and why the comparator output goes to a solid high level.
What should happen is the signal should become more and more delayed as you turn the pot.

Did you CHECK the Voltages on the opamp and comparator? -4.8 is lower than typical but should work.
Re-check the Disc pot connections and component values. Check all soldering and since you have a hand made double sided PCB ensure connection are made TOP & BOTTOM where needed.

[kt315]

8 - 0,6 - 0,6 - 1 - 1 = -4.8

0,6V on a diode
1V on C-E of a transistor
why you must see more voltage bit high??

[Mr.Jaick]

First, the Scope Voltage scale and Time base are Unkown so I can not give much on what you show us.
Also is the scope AC or DC coupled?
Where on the scope is the ZERO Volt level for each trace?

The TX_signal.jpg seems too clean and is NOT the same waveform that is in the Tx_RX_lf353out.jpg.
The TX signal in the second jpg looks like what I expect, with a slight kink near the peaks.

Are you Sure U101 & U102 have both +8 and -5V (-6.2)??

What does the signal going into U102, pin 2 look like? This is a Comparator, When pin 2 Voltage is higher than ground out is high. When lower than ground, output low.
Since the output is HIGH when the Disc pot is turned past middle indicates that the signal on pin 2, AC wave, is completely above ground. This signal should be going positive and negative. This can happen if U101 does not have -5(6.2)V.

scope time base is 10us per div and voltage is obvious when the tx is large it's 2V/div and when it's smaller it's 5V/div
both DC coupled , trigger source is vertical(VERT)
zero reference for first and second pic is at the X=zero (middle screenl)
for third pic: middle of bottom section and for forth is middle of top section of the screen
the last one is lower than middle screen if i remember it right

that test point on middle pin of the disc pot goes higher in DC and AC waveform dies when i turn it clockwise

TX waveform is clean because of that 100k trimmer, it's not a problem , it changes with that trimmer pot
unfortunately i could't capture the signal on pin 2 of U102 cuz my tx circuit runs unstable perhaps for dirtiness or bad solder joint,
since the pcb is a double sided board, it's so sensitive to desolder components, and that 100k trimmer legs.... but i see the signal before and after those 100pf caps ,
, before caps obviously is tx but after caps was a very low amplitude distorted signal !!! is that normal?

i think my negative rail is a bit low , i don't know why?
it's about -4.8

[waltr]

First, the Scope Voltage scale and Time base are Unkown so I can not give much on what you show us.
Also is the scope AC or DC coupled?
Where on the scope is the ZERO Volt level for each trace?

The TX_signal.jpg seems too clean and is NOT the same waveform that is in the Tx_RX_lf353out.jpg.
The TX signal in the second jpg looks like what I expect, with a slight kink near the peaks.

Are you Sure U101 & U102 have both +8 and -5V (-6.2)??

What does the signal going into U102, pin 2 look like? This is a Comparator, When pin 2 Voltage is higher than ground out is high. When lower than ground, output low.
Since the output is HIGH when the Disc pot is turned past middle indicates that the signal on pin 2, AC wave, is completely above ground. This signal should be going positive and negative. This can happen if U101 does not have -5(6.2)V.