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Amplifier Modules and PCBs For Sale

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#1,242
I have done the fix

Z0vkiUc.jpg


however, I'm slightly confused as to why it was necessary as all it seems to achieve is to connect the 'bottom' end of C17 to a different ground plane connection point at the 'left' end of C16? There is still continuity between the bottom of C17 and the bottom of C18 in spite of cutting the PCB tracks - am I missing something?
 
#1,243
The addition of R8 and R10 in V1A, V1B versions have made the ground plane reference of C17 different. Ground reference of C17 of TPA3255 is sensitive, it will not get the full power and the OCP will trip early.

TPA3251 does not have this problem so if we use the board with TPA3251, no fix will be needed.

Regards,
Lester

nautibuoy said:
I have done the fix

however, I'm slightly confused as to why it was necessary as all it seems to achieve is to connect the 'bottom' end of C17 to a different ground plane connection point at the 'left' end of C16? There is still continuity between the bottom of C17 and the bottom of C18 in spite of cutting the PCB tracks - am I missing something?
Click to expand...
 
#1,244
OK, thanks again Lester.

I'm almost ready to power up, heatsink installed, cap bank installed and I've just finished soldering up the op-amp plug-in boards.

I'll be using single-ended input so have set the jumper under the board to 'SE'.

Just one last question - with single-ended input I assume I connect my signal wires to In+ (hot) and Ground and ignore In-?
 
#1,245
Yes, just leave it floating. Also the pinout on TICore260BTL is different, refer to the picture below.

Careful on the polarity of the opamps (specially opamp to adapter mounting / soldering).
 

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#1,254
Hi Lester. I suggest you try installing some insulation material under the power supply module. In the picture below, which has two Mean Well SMPS units for tube filament duty, I used some spare glass/epoxy sheet, similar to PCB material, and ensured there's no continuity to the chassis via the stand-offs by using plastic types.

lI2V5pG.jpg


Anyway, I'm assuming you amp works so your power supply doesn't have problems with the amp's capatince at start-up?
 
#1,255
nautibuoy said:
Anyway, I'm assuming you amp works so your power supply doesn't have problems with the amp's capatince at start-up?
Click to expand...
There's no problem on startup since voltage ramp-up is quick.
There's a problem though when the ramp-down is not yet finished and the amp was restarted.
I placed a delay on the switcher so that the capacitors will be fully discharged on next power cycle. I also placed 1.8K ohms to bleed the capacitors faster. The daughtercard I designed will eliminate any ramp-up/down problems.

nautibuoy said:
Hi Lester. I suggest you try installing some insulation material under the power supply module. In the picture below, which has two Mean Well SMPS units for tube filament duty, I used some spare glass/epoxy sheet, similar to PCB material, and ensured there's no continuity to the chassis via the stand-offs by using plastic types.
Click to expand...

Maybe I'll just float the power supply by not connecting the earth terminal of SMPS300RS, then insulate the standoffs?

In Amir's review of modulus-286 he reported the same tingling sensation, it uses dual output version SMPS300RS too.

My only concern is that the mains leakage might show up on THD measurements.
 

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