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Old 25th September 2013, 12:24 AM   #3821
flg is offline flg  United States
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Quote:
Originally Posted by RonD2 View Post
3.9 and 4.1V
3.9V + 4.1V is not 16.5V ???
But, it sounds close to correct
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Old 25th September 2013, 12:26 PM   #3822
RonD2 is offline RonD2  United States
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Well, whatever it is, has finally fully manifested itself as I can no longer get past the slowly re-glowing light bulb on either of the boards.

I need to put these aside for a while. Too frustrating!
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Old 25th September 2013, 10:19 PM   #3823
Itsmee is offline Itsmee  England
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Quote:
Originally Posted by RonD2 View Post
3.9 and 4.1V
That sounds about right.

Quote:
Originally Posted by RonD2 View Post
....I need to put these aside for a while. Too frustrating!
Don't give up yet Ron, your almost there.

Quote:
Originally Posted by RonD2 View Post
....I can no longer get past the slowly re-glowing light bulb on either of the boards....
Thats because your trying to bias the amp with the bulb tester still connected, remove it then re-bias the amp (turn the bias down first before powering up), job done.

Last edited by Itsmee; 25th September 2013 at 10:22 PM.
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Old 27th September 2013, 04:51 PM   #3824
RonD2 is offline RonD2  United States
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Predictably, Itsmee, you are correct. Both boards seem to be working fine. They are mounted in the chassis and have been running stably for 40 minutes.

I think I knew when this build went bad, that it would drive me to the edge before working.

I have begun a final assembly (given this build, probably not THE final assembly) with the BA-3 front end. Picture below.

I have tested each of the BA-3 and F4 channels one at a time and all were stable (950mV for BA-3, 185mV for F4). Connecting them all together for the first time. This should be fun….
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File Type: jpg F4-BA-3.1.jpg (151.1 KB, 410 views)
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Old 27th September 2013, 06:16 PM   #3825
Itsmee is offline Itsmee  England
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Give yourself a pat on the back, well done mate and don't give up the building, you will get a lot of satisfaction from it once you have got over the frustrating bits
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Old 3rd October 2013, 08:18 AM   #3826
qwertyl is offline qwertyl  United Kingdom
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Quote:
Originally Posted by Andrzej Sochon View Post
Hello,

I would like to share grounding idea of my ballanced f4. Peter Daniel helped me, thank you very much, Peter, so I hope attached drawing will help some of novices too.

Wishing Nelson quick and full recovery,
Andrzej
How do you implement this grounding assuming standard F4 with diyAudio PCBs? Should the ground pin of XLR be connected directly to the ground on PSU board? Or to the ground on one of F4 boards? Or should I introduce another star point somewhere?
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Old 9th October 2013, 12:07 PM   #3827
RonD2 is offline RonD2  United States
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I have been listening to the F4/BA-3 for over a week now and am very impressed with the sound. It has stable 200 mV bias and 2 mV offset after playing for hours.

I do have a problem with turn-on though. Two times out of maybe 12 power-ons, both fuses blow. Both times it was first turn on in the morning after being off all night. In both cases, after immediately replacing the fuses, it starts normally.

The fuses are ceramic, 2.5A, slow blow. I have 66K mF per rail and the BA-3 connected to the power supply. I am using SL22-10005 thermistors (10R) and have installed bleeders but do not have a cap across the primaries.

Is this an inrush problem?
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Old 9th October 2013, 12:12 PM   #3828
6L6 is offline 6L6  United States
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Inrush? Yes.

Use 3.0A fuses. If those don't hold increase to 3.5A
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Old 9th October 2013, 12:19 PM   #3829
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Yes sounds like the in-rush current on the power supply. The more caps you have the greater the current spike at switch on.
When you turn it off and then turn it back on in a short period of time the caps still have a lot of charge in them so the in rush current is low, but if you leave it off for a while the caps will completely drain causing the big current spike on switch on.

The Thermistor should help though if you have connected it properly.
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Old 9th October 2013, 03:37 PM   #3830
RonD2 is offline RonD2  United States
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Quote:
Originally Posted by 6L6 View Post
Inrush? Yes.

Use 3.0A fuses. If those don't hold increase to 3.5A
Thought so. Will give 3.1A fuses a try.

6L6, you're up early!
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