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Old 8th October 2019, 01:36 PM   #16091
tooppy is offline tooppy  France
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Quote:
Originally Posted by Dennis Hui View Post
Where did you source the caps originally?
From Mouser.
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Old 8th October 2019, 01:41 PM   #16092
tooppy is offline tooppy  France
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I just change the cap, look at measures, seems good (considering I am looking at the right ones (zero at the output - around 50v at the PSU but obviously less - and maximum possible at R8 or R7), I let it cook and see later again tonight.
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Old 8th October 2019, 01:43 PM   #16093
Dennis Hui is offline Dennis Hui  Canada
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If they're from Mouser then I would expect they are genuine; more likely you just
had one that was damaged (perhaps in transit)?
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Old 8th October 2019, 01:48 PM   #16094
tooppy is offline tooppy  France
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Quote:
Originally Posted by Dennis Hui View Post
If they're from Mouser then I would expect they are genuine; more likely you just
had one that was damaged (perhaps in transit)?
It can happen, no big deal, Mouser don't sell purposely deficient items !
As I knew these things happen, I ordered more items than needed.
For example I have a spare rectifer , fuses , Jfets, resistors and still one more of these caps.
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Old 8th October 2019, 03:37 PM   #16095
Baobei is offline Baobei  United Kingdom
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Just finished assembling my F-5, but I keep blowing the fuses when powering up (I don't have a Variac, so full on...). I tested the power supply before connecting the boards and it ran without a problem. I re-checked all the connections and P1 and P2 are all the way anti-clockwise (until they make this clicky sound). P3 is not installed as I don't have the measuring equipment.

See some pictures attached. Any idea where the problem could be?
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File Type: jpg IMG_6913.jpg (864.3 KB, 169 views)
File Type: jpg IMG_6916.jpg (836.5 KB, 170 views)
File Type: jpg IMG_6917.jpg (836.6 KB, 163 views)
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Old 8th October 2019, 04:51 PM   #16096
zjjwwa is offline zjjwwa  Poland
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F5 power amplifier
Quote:
Originally Posted by Baobei View Post
Just finished assembling my F-5, but I keep blowing the fuses when powering up (I don't have a Variac, so full on...). I tested the power supply before connecting the boards and it ran without a problem. I re-checked all the connections and P1 and P2 are all the way anti-clockwise (until they make this clicky sound). P3 is not installed as I don't have the measuring equipment.
See some pictures attached. Any idea where the problem could be?
Did you try to power it up via a series old-tech filament bulb/halogen_lamp, of a wattage higher than the whole amplifier? The "soft-start" concept to fill up the filter capacitors, under load?
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Old 8th October 2019, 05:23 PM   #16097
Dennis Hui is offline Dennis Hui  Canada
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Baobei,

Are you using a slow blow fuse?

Can you please measure the resistance across R6 and R5? Are they close to zero?
If not, turn the pots P1 and P2 in the opposite direction until they are close to zero.
Then try powering up again.

Dennis
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Old 8th October 2019, 06:07 PM   #16098
6L6 is offline 6L6  United States
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Quote:
Originally Posted by Baobei View Post
I re-checked all the connections and P1 and P2 are all the way anti-clockwise (until they make this clicky sound).
As Dennis says, measure ohms across R6 and R5 and adjust the pots in whatever way is necessary to make that reading zero or very little. The pots don't necessary turn "down" by being turned anti-clockwise.
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Old 8th October 2019, 09:45 PM   #16099
Baobei is offline Baobei  United Kingdom
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Thanks a lot guys! Measured R5 and R6 and it looks like I did turn them the wrong way around...

Add that to my list of silly beginner's mistakes.

I'll try biasing again when I can find time later this week hopefully.
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Old 8th October 2019, 11:14 PM   #16100
flamethrower1 is offline flamethrower1  United States
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Quote:
Originally Posted by 6L6 View Post
As Dennis says, measure ohms across R6 and R5 and adjust the pots in whatever way is necessary to make that reading zero or very little. The pots don't necessary turn "down" by being turned anti-clockwise.
This is going to be helpful to me as I did not zero mine before I mounted them.
Anyway, looking forward to you getting yours going and your listening impressions
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