Hi Chris,
Please see what I did. I see no impact to anything beside my Turn OFF "boom" is disappeared. I can't connect MOVs close to the motor itself. My motor is in shell and quite hided behind MDF panel. In other words, MOV connection will require significant disassembly and might be ugly at the end.
Please see what I did. I see no impact to anything beside my Turn OFF "boom" is disappeared. I can't connect MOVs close to the motor itself. My motor is in shell and quite hided behind MDF panel. In other words, MOV connection will require significant disassembly and might be ugly at the end.
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Hi all FSP-ers. I have finally taken the plunge to populate my 2 FSP boards ordered a couple of years ago and the recently bought raw DC board. I had ordered a 50VA transformer with 36+36V secondaries because the raw DC circuit (Pic 2 in the official build guide) shows 2 x36VAC secondaries.
Seeing that the Rail and Gnd voltage should read somewhere between 34 and 36V I now realise my two secondaries are twice over specified.
I am thinking of paralleling the two transformer secondaries for the full 36Vac and feeding it into paralleled AC secondary input connectors on the raw DC board.
Is this a good and safe practice? Or should I buy another transformer with 2 x18V secondaries?
Thanks for your advice and help.
Seeing that the Rail and Gnd voltage should read somewhere between 34 and 36V I now realise my two secondaries are twice over specified.
I am thinking of paralleling the two transformer secondaries for the full 36Vac and feeding it into paralleled AC secondary input connectors on the raw DC board.
Is this a good and safe practice? Or should I buy another transformer with 2 x18V secondaries?
Thanks for your advice and help.
The rail voltage is measured after the on board regulator for each channel. Where it has "rail" printed there is a test point pad. The regs will be adjusted to 34-36V. Their inputs must be higher. 10-15V higher. The raw DC board has two separate rectification and filtering sections. Its a double mono scheme. Each of your secondaries can connect to each of its inputs. There are voltage drop/RC filter power resistor positions after each bridge on the raw board should you need burn any excess voltage since transformers and mains power differ in tolerances. If not used they should be jumpered. You could even emulate current draw loading with 500 Ohm 5W dummy loads on the raw DC board's outputs before connecting the phono so to test and trim it in leisure and in no fear for over-voltage to the phono channels DC inputs.
That reference was for those finding ready made 18V-18V transformers that can wire in series to reach 36V. Practice has shown that many times 32 or 34 VAC transformers are healthier than expected on lively mains feeds and are enough too. In any case throw away some voltage on those after bridge power resistor points if your raw will be more than 50V DC when loaded. It will do good both on regulators dissipation and will also perform filtering of EMI.
It's clearer now. I still have some more work to do on the boards as I'm waiting for a few more components.
I will power it up with a dummy load (is 470R/5W OK? -- this is more readily available locally) to check that the raw DC is close to 50V. Then I'll trim as you suggested, if necessary.
I will keep you posted with my progress.
I will power it up with a dummy load (is 470R/5W OK? -- this is more readily available locally) to check that the raw DC is close to 50V. Then I'll trim as you suggested, if necessary.
I will keep you posted with my progress.
Dear SALAS,
Need some help troubleshooting.
All of a sudden one of my channels has started humming. The other channel is quiet. Both boards are, otherwise, exactly the same, of course.
When I measure AC on the power leads they are of the same value so I figure I can discount my raw supply.
Have I destroyed something within the regulator? Where would be a good place to look?
THANKS,
Need some help troubleshooting.
All of a sudden one of my channels has started humming. The other channel is quiet. Both boards are, otherwise, exactly the same, of course.
When I measure AC on the power leads they are of the same value so I figure I can discount my raw supply.
Have I destroyed something within the regulator? Where would be a good place to look?
THANKS,
We don't have a previous case in the thread so to lead you directly to a known solution but I would look first in the power regulator and in the cascode transistor of the first stage. Maybe a DMM in ACmV mode could be helpful. Optimally it takes using a scope to hunt for AC waveform in places that there should be DC only. Starting with the DC rail after the regulator.
Sorry guys, cartridge specs are:
Cartridge system: MI
Output voltage: 5mV
Channel separation 1kHz: 30dB
Frequency range: 10Hz-55kHz
Compliance: 20 um/mN
Stylus type: Elliptical
Tracking force recommended: 1,5gr
Internal impedance DC: 475ohm
Internal inductance: 45mH
Recommended load Resistance: 47kohm
Cartridge weight: 5.5gr
Cartridge system: MI
Output voltage: 5mV
Channel separation 1kHz: 30dB
Frequency range: 10Hz-55kHz
Compliance: 20 um/mN
Stylus type: Elliptical
Tracking force recommended: 1,5gr
Internal impedance DC: 475ohm
Internal inductance: 45mH
Recommended load Resistance: 47kohm
Cartridge weight: 5.5gr
40dB is the usual "standard" for 5mV cartridges. With 46dB gain you risk clipping in some very strong records peaks or during loud pops. I had carefully set the various gains recommended for MM, HMC, MC, LMC in the manual for that reason. If you need more than -10dbV consumer standard output at 0dB disc modulation that FSP is designed for, then I suggest you use a 10dB gain line preamplifier so to ensure the proper allocation in some total system gain scheme. Think about that and if you still want to try 46dB to see for yourself about your record peaks and average audible THD level with that gain and your cart, I can still inform you how to go 46dB but I don't recommend it.
At 0dB modulation is the -10dBV as I wrote. Can give adequate pk-pk which is double what's on Q4's drain (11-12V in most builds) i.e. 22-24Vpp. So the sensitivities and gains recommendations should be followed to keep those relationships steady as designed.