can someone advice me on how to calibrate the bios - trim on these amplifier boards .
I have built the the amplifier into separate chassis all is working but they are pretty much stone cold unless they are driven hard. what component do i need to measure across and to what value
thanks
I have built the the amplifier into separate chassis all is working but they are pretty much stone cold unless they are driven hard. what component do i need to measure across and to what value
thanks
i will also like to add its fused on the iec and the negative rail , you can not see it because its underneath the amplifier board
Blue trimmer in front of the middle transistor on the radiator 🙂
This amplifier is class AB (B). It shouldn't warm up without a signal. The fuse must be installed in both power rails.
This amplifier is class AB (B). It shouldn't warm up without a signal. The fuse must be installed in both power rails.
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i know about the trimmer lol , i need to know what component i need to measure across and to what valve . Thanks
The default price included 2 channel assembeld and tested amp board
works voltage: Recommned +/-DC45V
Transformer power recommend above 300VA
Output power: 80W +80W at 8ohm
150W+150W at 4ohm.
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Measure dcv across the 0.27 ohm resistors
Adjust the 1000 ohm pot for roughly 26mV x 2 across
both 0.27
The more static bias the hotter the heatsinks, larger class A range
Adjust the 1000 ohm pot for roughly 26mV x 2 across
both 0.27
The more static bias the hotter the heatsinks, larger class A range
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thank you much for reply and advice , what would you suggest ? keep the amplifier boards at class a/b or raise upto class a .
if i was to raise to class a what mv would i adjust the dcv too ?
thanks again so much
if i was to raise to class a what mv would i adjust the dcv too ?
thanks again so much
Run it as intended class a/b
Do those to-3 metal can transistors have thermal compound on both sides of the mica insulators?
It takes a while for the heatsinks to warm up check bias after warmup
That to-126 pkg with the thermal pad, if the part has no exposed metal it does not need the insulator, remove pad and just use some thermal compound
Do those to-3 metal can transistors have thermal compound on both sides of the mica insulators?
It takes a while for the heatsinks to warm up check bias after warmup
That to-126 pkg with the thermal pad, if the part has no exposed metal it does not need the insulator, remove pad and just use some thermal compound
0.026 / 0.44 = ~60mA of static bias
I was referring to the schematic that was posted above which looks to be an old RCA design using different components
I was referring to the schematic that was posted above which looks to be an old RCA design using different components
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Bd138,139 in a to-126 with exposed metal is old stock so insulator required.
If you are powering up for the first time, suggest to use a dim bulb tester.
If you are powering up for the first time, suggest to use a dim bulb tester.
after a evening of messing around with the amplifer board the only component the trim pot changes in the small device labeled 3090 its the small blue device close to the trim pot and i have trimmed them both too 250.0 mv
does anyone know what is the correct value please 😀
the 0.22 ohm resistors does not change with the trim pot
does anyone know what is the correct value please 😀
the 0.22 ohm resistors does not change with the trim pot
