Thanks Bill & Ralph!
So since I've managed to do the BTL connection, I have tried all configurations and all configurations did not allow me to start at 67.5k Hz. I need to start it 50k and dial it up. Hopefully after I install the toggle switch, I am able to start it at 50k and flip it to get 67.5k (just an extra step), otherwise I guess I will have to rely on the mechanical switch on the turntable. Anyways, I guess I will live with this since I don't have that many 45rpm records anyway.. So here are the configurations and my findings
1) BTL to 12:240 xmfr (runs pretty hot, finger hot)
2) BTL to 24:240 xmfr (did not remove 5k6 resistor because volume knob at the amp too sensitive and difficult to get 115v) - but I think running it in this mode with the 5k6 resistor removed and powering the motor at 115v would have my amp run the coolest and might be the best and I will need a higher resistance trimmer in order to get more fine adjustments as with the current volume knob (25k) at 7o'clock + the alps potentiometer at SG4 output at max, I get 115v and somehow the voltage goes against the direction I'm turning somewhere around 3-4o'clock and can rise as high as 160v before falling back to 115v at 5o'clock max volume. I think I can blame this to the volume control at my amp having not enough resistance perhaps and with the BTL mode, it is very powerful.
3) SE to 24:240 xmfr (remove 5k6 resistor to run the motor in 115v) - amp runs only very slightly warm. comparable to BTL to 24:240 mode, but this allows me to set the volume knob somewhere around 10-11o'clock with ALPs pot at max volume for 115v max. This is the configuration that Ralph suggested. This runs cool too.
I am planning to use the ALPs pot at the panel for voltage adjustment and the volume control at the amp to set the maximum voltage for the ALPs pot. The ALPs pot is for the SG4 output. Would this be ok?
I think I will be running the 2nd configuration since it runs the coolest. But I think I will need a higher resistance trimmer to replace the volume control. May I know which trimmer should I get?
So since I've managed to do the BTL connection, I have tried all configurations and all configurations did not allow me to start at 67.5k Hz. I need to start it 50k and dial it up. Hopefully after I install the toggle switch, I am able to start it at 50k and flip it to get 67.5k (just an extra step), otherwise I guess I will have to rely on the mechanical switch on the turntable. Anyways, I guess I will live with this since I don't have that many 45rpm records anyway.. So here are the configurations and my findings
1) BTL to 12:240 xmfr (runs pretty hot, finger hot)
2) BTL to 24:240 xmfr (did not remove 5k6 resistor because volume knob at the amp too sensitive and difficult to get 115v) - but I think running it in this mode with the 5k6 resistor removed and powering the motor at 115v would have my amp run the coolest and might be the best and I will need a higher resistance trimmer in order to get more fine adjustments as with the current volume knob (25k) at 7o'clock + the alps potentiometer at SG4 output at max, I get 115v and somehow the voltage goes against the direction I'm turning somewhere around 3-4o'clock and can rise as high as 160v before falling back to 115v at 5o'clock max volume. I think I can blame this to the volume control at my amp having not enough resistance perhaps and with the BTL mode, it is very powerful.
3) SE to 24:240 xmfr (remove 5k6 resistor to run the motor in 115v) - amp runs only very slightly warm. comparable to BTL to 24:240 mode, but this allows me to set the volume knob somewhere around 10-11o'clock with ALPs pot at max volume for 115v max. This is the configuration that Ralph suggested. This runs cool too.
I am planning to use the ALPs pot at the panel for voltage adjustment and the volume control at the amp to set the maximum voltage for the ALPs pot. The ALPs pot is for the SG4 output. Would this be ok?
I think I will be running the 2nd configuration since it runs the coolest. But I think I will need a higher resistance trimmer to replace the volume control. May I know which trimmer should I get?
If you want more control, you will want to reduce the resistance of the volume control.
I would use a fixed resistor between the SG4 and the amp input and use the volume control to adjust output. You can pick the value empirically; increase the series resistor to reduce the output and give you more adjustment range.
For a 2W motor, the amp should never get more than barely warm. If it is running hot, it is most likely breaking into oscillations. The amp is designed to work from 20-20kHz and into mostly resistive loads and you are driving a very inductive load.
If you have access to an oscilloscope, you can see what is happening, if it is going into clipping or oscillations.
I would use a fixed resistor between the SG4 and the amp input and use the volume control to adjust output. You can pick the value empirically; increase the series resistor to reduce the output and give you more adjustment range.
For a 2W motor, the amp should never get more than barely warm. If it is running hot, it is most likely breaking into oscillations. The amp is designed to work from 20-20kHz and into mostly resistive loads and you are driving a very inductive load.
If you have access to an oscilloscope, you can see what is happening, if it is going into clipping or oscillations.
So after running it for awhile. I realized something when running in BTL mode which I should have noticed yesterday. It seems the voltage will fluctuate +-2volts and not very stable at the speaker output across all voltage output from 0-240v.
So I guess I'm back to my last known good working configuration, SG4 output to R and L at the 3 pin and GRD to 3 pin GRD and no change at speaker output with xmfr running 24:240 powering my thorens 115v with 5k6 resistor removed.
This is the most stable configuration. voltage doesn't fluctuate, heatsink is only slightly a little warm.
Happy to have it running and learnt so much these past few days messing around.
So I guess I'm back to my last known good working configuration, SG4 output to R and L at the 3 pin and GRD to 3 pin GRD and no change at speaker output with xmfr running 24:240 powering my thorens 115v with 5k6 resistor removed.
This is the most stable configuration. voltage doesn't fluctuate, heatsink is only slightly a little warm.
Happy to have it running and learnt so much these past few days messing around.
Been thinking about populating the top left corner of the TDA8950 board for 12v+ to power up the SG4 from this board to make things more compact. It seems I would need a regulator at U2 position. thinking of getting a LM317. and I'm getting about 14.5v DC (no load) going in to the emitter of U2. I think that should be enough to power the SG4?
I did some rough googling trying to learn about the LM317, on my board, and in reference to theLM317 datasheet, R18 is supposed to be the fixed resistor and R19+R20+R21 is supposed to be the variable resistor going in to the collector, it seems for me to get 12v out from it, I will need to get R19 + R20 + R21 to 4k ohms. Right now R19 and R20 is both 2.4k ohms and R21 is 220ohms. R18 is 220ohm.
Alternatively I believe I can just change R18 to a 275ohm resistor I think. Can someone help confirm this?
C7, i believe are the capacitors to help with stabilizing the output and i believe installing just a 1 uF capacitor would be enough right?
C9 and C10 seems omittable to me I think and looks like it is for the negative voltage out which I do not need.
Hope can someone confirm this for me.. I'm only a beginner in electrics.. Thanks!
I did some rough googling trying to learn about the LM317, on my board, and in reference to theLM317 datasheet, R18 is supposed to be the fixed resistor and R19+R20+R21 is supposed to be the variable resistor going in to the collector, it seems for me to get 12v out from it, I will need to get R19 + R20 + R21 to 4k ohms. Right now R19 and R20 is both 2.4k ohms and R21 is 220ohms. R18 is 220ohm.
Alternatively I believe I can just change R18 to a 275ohm resistor I think. Can someone help confirm this?
C7, i believe are the capacitors to help with stabilizing the output and i believe installing just a 1 uF capacitor would be enough right?
C9 and C10 seems omittable to me I think and looks like it is for the negative voltage out which I do not need.
Hope can someone confirm this for me.. I'm only a beginner in electrics.. Thanks!
I tried doing this, but this happened instead. Not sure why... When there's load the 14.5VDC drops to about 12v. So I'm supplying 12VDC inside the regulator and the regulator is giving out 5VDC. Any idea what caused this?.. I have a LM317t lying around.. Maybe I should try with the LM317 and see if I get any difference in results?
Attachments
If I had to guess, I'd say the 12V (14.5V) supply does not start up cleanly, has excessive ripple or noise on it. Try isolating the supply to the SG4 with a series diode (1N4001 or similar, anode towards supply, cathode to SG4) and a large filter cap (1000uFd or more) from the SG4 12V input to ground.
Does the SG4 have a reset controller installed at U4? It should prevent this type of occurrence.
Does the SG4 have a reset controller installed at U4? It should prevent this type of occurrence.
The B3F-3150 will not be a fit for the SG-4 PCB for 2 reasons:
1. The spacing on the 2 front holes of the existing footprint are 6.35mm and the B3f-3150 is 4.5mm.
2. Both front holes of the existing footprint are ground. The current switches make contact between the front pads and the rear pads, not from side to side.
If you turn the switch sideways so the actuator is facing U8, then the pins would fit and the switch would be between the correct pads, but that doesn't work for activating the switches.
Probably better to just mount switches on a separate piece of perf-board and run wires to the SG4.
1. The spacing on the 2 front holes of the existing footprint are 6.35mm and the B3f-3150 is 4.5mm.
2. Both front holes of the existing footprint are ground. The current switches make contact between the front pads and the rear pads, not from side to side.
If you turn the switch sideways so the actuator is facing U8, then the pins would fit and the switch would be between the correct pads, but that doesn't work for activating the switches.
Probably better to just mount switches on a separate piece of perf-board and run wires to the SG4.
I used these
https://www.altronics.com.au/p/s1405-spst-mom.-solder-tail-pushbutton-switch/ and they work fine.
A bit big and ugly though but you should be able to find something similar.
Regards,
kffern
Hi Bill,
first of all, thank you for this amazing project.
I'm ordering parts at Mouser, and have few question.
1) Crystal 9B-18.432MAAJ-B is on backorder. Can I use ABL-18.432MHZ-D7YI? The only difference is ESR - 40 Ohm vs 30 Ohm.
2) can I use Use DS1812-10+ instead of DS1833-10+ (which is obsolete)?
Differences (1812 vs 1833):
Threshold Voltage: 4.35V vs 5.00V
Output Type: Active High, Push-Pull vs Active High, Open Drain
Reset Delay Time: 150 ms vs 450 ms
Operating Supply Current: 40 uA vs 50 uA
3) Can I use 24Vin -12Vout DC-DC Converter from 24V switching power supply to SG4 board? RKZ3-2412S RECOM Power | Mouser
Thanks in advance for your help.
Giorgi
first of all, thank you for this amazing project.
I'm ordering parts at Mouser, and have few question.
1) Crystal 9B-18.432MAAJ-B is on backorder. Can I use ABL-18.432MHZ-D7YI? The only difference is ESR - 40 Ohm vs 30 Ohm.
2) can I use Use DS1812-10+ instead of DS1833-10+ (which is obsolete)?
Differences (1812 vs 1833):
Threshold Voltage: 4.35V vs 5.00V
Output Type: Active High, Push-Pull vs Active High, Open Drain
Reset Delay Time: 150 ms vs 450 ms
Operating Supply Current: 40 uA vs 50 uA
3) Can I use 24Vin -12Vout DC-DC Converter from 24V switching power supply to SG4 board? RKZ3-2412S RECOM Power | Mouser
Thanks in advance for your help.
Giorgi