What is the frequency of oscillations? If the frequency is low (<100Hz), I would look at the power supply (also check to see if the voltage from the power supply is constant or oscillating). If the frequency is high (kHz or higher), it is the amp and xfmr interacting most likely. Do you have a snubber network across the output of the xfmr? If not, try a .01uFd film cap rated for 400VAC or higher directly across the output. Adding small series resistance between the amp and the LV secondary of the xfmr can also help, although it will dissipate heat and lower the output voltage.
Hi Bill,
The PS drops voltage as soon as the amp starts to oscillate (16 to 18V)
I tried using the PS from the good SGV unit. The amp oscillates at around 120v output at the transformer.
I then used the output transformer from the good SG4 unit and the TDK power supply and the amp oscillates.
I have a cheap DSO138 oscilloscope. It looks like the oscillations are lower than 50 hz. But occasionally I see some around 80 hz so generally below 100Hz.
Looks like I need to change PS and transformer? I had thought the TDK unit was overkill. It was bought off ebay australia. The box and paperwork looked genuine.
It might be a while before I can get replacements. The seller of the good PS has disappeared. Is the Meanwell SMPS good for this? They are a bit more expensive.
Thanks,
kffern
I used a GS60A24 for the Eagle. It has been replaced by the GST60A24 which works the same, but can be sensitive to line voltage fluctuations (ie when the house AC kicks in). You definitely need a stable voltage source to power the amp.
I don't recall what sized xfmr you are using? I know some prefer overkill, but the larger the xfmr core, the more difficult it can be to drive at start up, especially with a class D amp; they tend to shut down instantaneously when they detect an overload. The Eagle used a 25W toroid and it drove Lencos without a problem.
I don't recall what sized xfmr you are using? I know some prefer overkill, but the larger the xfmr core, the more difficult it can be to drive at start up, especially with a class D amp; they tend to shut down instantaneously when they detect an overload. The Eagle used a 25W toroid and it drove Lencos without a problem.
After much experimenting, I found the addition of an NTC thermistor worked really well for controlling the inrush current of the xfmr. For xfmrs in the 50VA range the NTC 5D-9 works well for me with my 100W class D amps.
You really shouldn't see any noticeable drop in the PSU output voltage; I use a 24V 10A
SMPS and there's only about 0.1V drop between no load and full load.
AFAIK Meanwell PSUs have a good reputation, I always include an at least x4 power capability in my PSUs.
You really shouldn't see any noticeable drop in the PSU output voltage; I use a 24V 10A
SMPS and there's only about 0.1V drop between no load and full load.
AFAIK Meanwell PSUs have a good reputation, I always include an at least x4 power capability in my PSUs.
Yes, exactly. Earlier in my experimenting I used fixed resistors, as shown here:-
https://www.diyaudio.com/forums/att...-vpi-synchronous-turntable-motor-dsc_0122-jpg
This was too wasteful, and several alternatives were tried, including using relays to switch out the resistors when up to speed; but the NTC resistors were,in my case at least, the best, and easiest solution.
The only downside is that too quick turning off and back on, when the NTC is still at its low resistance, but even here there's only a short delay until the amp resets and restarts OK
This is where some of the precursors to the SG4 were discussed
Optimally driving a (VPI) synchronous turntable motor
https://www.diyaudio.com/forums/att...-vpi-synchronous-turntable-motor-dsc_0122-jpg
This was too wasteful, and several alternatives were tried, including using relays to switch out the resistors when up to speed; but the NTC resistors were,in my case at least, the best, and easiest solution.
The only downside is that too quick turning off and back on, when the NTC is still at its low resistance, but even here there's only a short delay until the amp resets and restarts OK
This is where some of the precursors to the SG4 were discussed
Optimally driving a (VPI) synchronous turntable motor
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I'm using a 50VA in the working unit. In the second unit I have tried a 50VA, 80VA and 30VA. All had the same problem. There does seem to be a problem with the TDK smps as it drops voltage with both SG4 units. I have plugged it into the TDA7492 amp that I first suspected was not working and it is playing music through the garage speakers.
Ralph, I'm trying to find something on RS supplies in australia to avoid paying for shipping. Would this be the equivalent B57237S0509M000 | EPCOS B57237S0509M000 Thermistor 5Ω, 15 (Dia.) x 7mm | RS Components
Regards,
kffern
Finished 3, Very Happy
I finished 3 motor controllers for my two record players plus another for future use. The pcb's were sold in threes so I just went for it. I have a 24V Rega type DIY table that uses their 24V , 4W motor upgrade, wired for 2 phases using the stock type 4 pin DIN connector. I used a stereo TDA7492 chip amp and two Signal LP-40-200 output transformers. I made by own rectification board with a 12V regulator coming off a diode for the SG-4.
The other table is an old Russco Studio Pro B that uses a 25W Bodine NYC-12 motor that is built like a tank with an idler wheel and 7+ lb. platter. The Russco had a bad phase shift capacitor that caused the motor and cap to heat up after a few minutes of use and slow down. The difference in 2 phase wiring is night and day for reducing vibration and noise. You get more torque too as it is more efficient. I used a GX20 4 pin aviation connector off of eBay, 4 X 18 guage SJOOW wire for a safe connection to the motor, and the chip amps are DC 12-24V TPA3116 D2 100W (rated into 2 ohms, but 50W into 4 ohms and maybe 35W into 8 ohms.) The Chassis are cheap Hammond aluminum units that flex and I would not recommend them but they allowed me to fashion my own faceplates from zebra wood and are just the right size. They make a steel version and that is the way I would go, or order some nice ones from overseas.
I am very grateful to Pyramid for his generosity with his knowledge and help. This DIY website is awesome and the Russco in particular was a long time in the making with much money invested. The capacitor to fix the issue is hard to find, 3.45uf, and wiring it 2 phase substantially improved the noise floor, its main weakness. The Rega allows for pitch control and the 2 phase wiring gives this little motor more torque, enough to use a cleaning cloth for dust while the record is spinning. I am a happy camper!
I finished 3 motor controllers for my two record players plus another for future use. The pcb's were sold in threes so I just went for it. I have a 24V Rega type DIY table that uses their 24V , 4W motor upgrade, wired for 2 phases using the stock type 4 pin DIN connector. I used a stereo TDA7492 chip amp and two Signal LP-40-200 output transformers. I made by own rectification board with a 12V regulator coming off a diode for the SG-4.
The other table is an old Russco Studio Pro B that uses a 25W Bodine NYC-12 motor that is built like a tank with an idler wheel and 7+ lb. platter. The Russco had a bad phase shift capacitor that caused the motor and cap to heat up after a few minutes of use and slow down. The difference in 2 phase wiring is night and day for reducing vibration and noise. You get more torque too as it is more efficient. I used a GX20 4 pin aviation connector off of eBay, 4 X 18 guage SJOOW wire for a safe connection to the motor, and the chip amps are DC 12-24V TPA3116 D2 100W (rated into 2 ohms, but 50W into 4 ohms and maybe 35W into 8 ohms.) The Chassis are cheap Hammond aluminum units that flex and I would not recommend them but they allowed me to fashion my own faceplates from zebra wood and are just the right size. They make a steel version and that is the way I would go, or order some nice ones from overseas.
I am very grateful to Pyramid for his generosity with his knowledge and help. This DIY website is awesome and the Russco in particular was a long time in the making with much money invested. The capacitor to fix the issue is hard to find, 3.45uf, and wiring it 2 phase substantially improved the noise floor, its main weakness. The Rega allows for pitch control and the 2 phase wiring gives this little motor more torque, enough to use a cleaning cloth for dust while the record is spinning. I am a happy camper!
Attachments
Anyone got an extra board?
First off thank to Bill, Seth, Ralph and all who contributed to this thread. Over 100 pages now and chocked full of invaluable information.
I'm in the process of ordering parts and it occurred to me that since OshPark requires a minimum order of three boards there maybe some spares floating around that a kind soul may want to part with (given adequate compensation)
If you have an extra board and wish to sell it - please PM me and let me know how much you want for it. Shipping will be to the US (Durham, NC).
As an aside, for those of us in pandemic lock-down mode: have you noticed picking up a lot more DIY projects lately? ;-)
Thanks,
-bill
First off thank to Bill, Seth, Ralph and all who contributed to this thread. Over 100 pages now and chocked full of invaluable information.
I'm in the process of ordering parts and it occurred to me that since OshPark requires a minimum order of three boards there maybe some spares floating around that a kind soul may want to part with (given adequate compensation)
If you have an extra board and wish to sell it - please PM me and let me know how much you want for it. Shipping will be to the US (Durham, NC).As an aside, for those of us in pandemic lock-down mode: have you noticed picking up a lot more DIY projects lately? ;-)
Thanks,
-bill
Hi.
Today I finally finished my SG4 PCB.
Unfortunately I forgot to reverse direction of MCP101-450H
When I turned on the power supply I got STBY on the main LCD displey but after 3 sec something started to smoke. I quickly turned off and tried to reverse direction of MCP101-450H.
Now I get only full light up LCD screen.
How can find what component failed or can I run without MCP101-450H if I put reset pin of MP to ground or 5V?
Today I finally finished my SG4 PCB.
Unfortunately I forgot to reverse direction of MCP101-450H
When I turned on the power supply I got STBY on the main LCD displey but after 3 sec something started to smoke. I quickly turned off and tried to reverse direction of MCP101-450H.
Now I get only full light up LCD screen.
How can find what component failed or can I run without MCP101-450H if I put reset pin of MP to ground or 5V?
I need boards too
Hi Bill,
I am looking for both SG-4 and MA-4D boards too. Would you be willing to share costs if we order a set from OSHPark.
Thanks,
Matthew
First off thank to Bill, Seth, Ralph and all who contributed to this thread. Over 100 pages now and chocked full of invaluable information.
I'm in the process of ordering parts and it occurred to me that since OshPark requires a minimum order of three boards there maybe some spares floating around that a kind soul may want to part with (given adequate compensation)
As an aside, for those of us in pandemic lock-down mode: have you noticed picking up a lot more DIY projects lately? ;-)
Thanks,
-bill
Hi Bill,
I am looking for both SG-4 and MA-4D boards too. Would you be willing to share costs if we order a set from OSHPark.
Thanks,
Matthew
