Sisyphism said:
A bulb is nice to detect a problem at first run.
If all is ok the bulb enlights brievly and go dark again with pots at min.
The charging caps then nothing.
If the bulb stay lighting , switch off, there is a fault or pots are maximum.
I you do not start at a too low voltage, why not to use your variac in a
second time.
Yes, pots at minimum = Zero Ohm.
First i have to put the PSU into the case,
and there are some questions about thermistors i should use.
Attached File:
This is something I DO NOT KNOW IF IT REALLY WORKS FINE,
How should i calculate those Thermistors ?
TH1 should be ok i think, but how about TH2 + TH3 ?
Please correct me, if there is something wrong.
First i have to put the PSU into the case,
and there are some questions about thermistors i should use.
Attached File:
This is something I DO NOT KNOW IF IT REALLY WORKS FINE,
How should i calculate those Thermistors ?
TH1 should be ok i think, but how about TH2 + TH3 ?
Please correct me, if there is something wrong.
Attachments
Sisyphism said:Yes, pots at minimum = Zero Ohm.
First i have to put the PSU into the case,
and there are some questions about thermistors i should use.
Attached File:
This is something I DO NOT KNOW IF IT REALLY WORKS FINE,
How should i calculate those Thermistors ?
TH1 should be ok i think, but how about TH2 + TH3 ?
Please correct me, if there is something wrong.
You seem to be using 3 thremistors where one would do the job.
I dont think you need TH1 just connect it to earth for safety.
If you put TH1 in series with mains you dont need TH2.
Those thermistors are calculated for you. Check the bottom of your schematic you posted and it tells values and part numbers for all of them.
When you fire it up you can use your variac but you can use this as well
http://www.antiqueradio.org/dimbulb.htm
This is the dim bulb tester they were talking about and it has saved a few of my amps.
500w is more than enough.
Uriah
When you fire it up you can use your variac but you can use this as well
http://www.antiqueradio.org/dimbulb.htm
This is the dim bulb tester they were talking about and it has saved a few of my amps.
500w is more than enough.
Uriah
Nelson
My Aleph30 clone when used with the Krell 7b pre-amp sounds exceptional with 1 meter long Newform ribbons. I find it extremely musical. With a 600 VA transformer the control is outstanding. I rate it as one of the musical amps I own.
I am collecting parts for the F5 and Aleph J for a possible bi-amp scenario. It would be interesting to see how a F5 with just two output devices per channel will compare,
Regards and many thanks for putting the design within the public domain.
Jozua
My Aleph30 clone when used with the Krell 7b pre-amp sounds exceptional with 1 meter long Newform ribbons. I find it extremely musical. With a 600 VA transformer the control is outstanding. I rate it as one of the musical amps I own.
I am collecting parts for the F5 and Aleph J for a possible bi-amp scenario. It would be interesting to see how a F5 with just two output devices per channel will compare,
Regards and many thanks for putting the design within the public domain.
Jozua
Jozua said:
To be clear, the F5 is _not in the public domain - it remains copyright First Watt (as far as I know). All we've been granted is use of the design for personal DIY use. But I certainly join you in the chorus of thanks to Mr. Pass for his generosity and for all his contributions to the community.
-j
Hi,
power just the mains side with ONLY the transformer connected through a bulb tester.
Switch off.
Add the rectifiers and ONE bank of smoothing.
Test again.
Progressively add each bank of smoothing and retest.
Now add one channel of amplifier and test.
Add the second channel and test.
Remove the bulb tester.
Power the whole amplifier from your Variac.
Start it up at low voltage and gradually bring up the voltage.
Periodically check the cap voltages.
When up to full voltage start increasing the bias current on one amplifier. Get is approximate, but on the low side.
Start biasing the second amplifier, again to the low side of final.
Remove the Variac.
Power up again and finalise the bias setting.
Check output offset and output mVac.
When you are happy, connect your source and recheck the offset and mVac.
Finally connect some cheap speakers and have a listen.
power just the mains side with ONLY the transformer connected through a bulb tester.
Switch off.
Add the rectifiers and ONE bank of smoothing.
Test again.
Progressively add each bank of smoothing and retest.
Now add one channel of amplifier and test.
Add the second channel and test.
Remove the bulb tester.
Power the whole amplifier from your Variac.
Start it up at low voltage and gradually bring up the voltage.
Periodically check the cap voltages.
When up to full voltage start increasing the bias current on one amplifier. Get is approximate, but on the low side.
Start biasing the second amplifier, again to the low side of final.
Remove the Variac.
Power up again and finalise the bias setting.
Check output offset and output mVac.
When you are happy, connect your source and recheck the offset and mVac.
Finally connect some cheap speakers and have a listen.
Start up
What a nice advice!
Thank you AndrewT.
I think i should warm it up first was mentioned.
To let it run for 1h to 2h or so,
at just 0.4V instead of 0.59V (R11 and R12),
before setting it at final adjustment.
There is one thing i don't understand at this time:
Well DC-Offset ist measured in V DC i think,
but since i'm a "caveman",
i do not know what mVac means,
and what i have to do with it.
Just measure it at same connection as V DC with V AC?
As low as possible?
Thank you guys!
What a nice advice!
Thank you AndrewT.
I think i should warm it up first was mentioned.
To let it run for 1h to 2h or so,
at just 0.4V instead of 0.59V (R11 and R12),
before setting it at final adjustment.
There is one thing i don't understand at this time:
Well DC-Offset ist measured in V DC i think,
but since i'm a "caveman",
i do not know what mVac means,
and what i have to do with it.
Just measure it at same connection as V DC with V AC?
As low as possible?
Thank you guys!
Re: Start up
mVDC means millivolts DC.
A millivolt is a thousandth of a volt.
Sisyphism said:What a nice advice!
Thank you AndrewT.
I think i should warm it up first was mentioned.
To let it run for 1h to 2h or so,
at just 0.4V instead of 0.59V (R11 and R12),
before setting it at final adjustment.
There is one thing i don't understand at this time:
Well DC-Offset ist measured in V DC i think,
but since i'm a "caveman",
i do not know what mVac means,
and what i have to do with it.
Just measure it at same connection as V DC with V AC?
As low as possible?
Thank you guys!
mVDC means millivolts DC.
A millivolt is a thousandth of a volt.
no,pro said:
there is always a DC voltage at the output and there is always an AC voltage at the output. It depends on whether one has the equipment to measure these voltages.
Both can be well below 1mVdc and below 1mVac.
adding the source instead of shorting the input is very likely to increase one or other or both.
It is always worth checking before connecting the speakers.
My dmm have a full scale reading of 200mVdc and 200mVac (over a very restricted bandwidth).
I have a resolution of 0.1mV on both scales. These can be bought very cheaply with tolerance of better than 0.5%.