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HELP! Capacitor specs for Sonic Frontiers SFC-1 Control Amplifier

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devilsindetails

devilsindetails

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Joined 2011
Hey Gang....I have a Sonic Frontiers SFC-1 Control Amplifier (4x EL34, 1x12AT7, 2x12AU7) that requires new main caps (circled in red on the attached pic).

While I have the voltage specs for these (450v) I have no idea how many uF.

There are no spec markings on the exterior of these huge can caps, save for a manufacturing number of 658 9302 319.

Anyone out there have any experience with these. Lots of owner's manual information but no service manual or schematics.

Thanks Leo
 

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devilsindetails

devilsindetails

Member
Joined 2011
Gets the typical "thump" at speaker output after startup delay (signal output for five seconds) and then thumps again cutting out one channel, then another thump cutting out the other channel.

That seems to tell me the caps are energizing and discharging too quickly on startup and then losing whatever capacitance they have entirely. Yes ? No?
 
devilsindetails

devilsindetails

Member
Joined 2011
Thanks...got an e-mail from Chris Johnson but these caps remain a bit of a mystery...they are guessing somewhere between 1200-1500 uf at 350 volts but as these puppies will be tres-expensive I would like something a little more definitive. I know I can up the voltage capacity without any harm but the uf ratings would seem to be more critical to determine exactly.
 
T

ticknpop

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Joined 2005
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The cap value in uf isn't critical 1200-1500 uf range is fine. These caps would be less than $20.00 each at Digikey. I'd do the rest of the smaller electrolytics at the same time. Try to find a 105 C cap for longer life of the same value and physical diameter. Panasonics are a good bet.
 
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M Gregg

M Gregg

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Joined 2010
devilsindetails said:
Gets the typical "thump" at speaker output after startup delay (signal output for five seconds) and then thumps again cutting out one channel, then another thump cutting out the other channel.

That seems to tell me the caps are energizing and discharging too quickly on startup and then losing whatever capacitance they have entirely. Yes ? No?
Click to expand...

Have you measured the power rails when this happens?
I would have thought that bad caps would cause hum and /or short..


Regards
M. Gregg
 
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devilsindetails

devilsindetails

Member
Joined 2011
Braga said:
Hi,
They look exactly the same as the SFS 40 power amp. main caps.
Value is 1700uF/300 V x 2 in series.
Click to expand...

Yes you were right. Once I removed the caps the values were marked on the IC board. Replaced them with 1500uf/300 V x 2 in series but after working flawlessly for about 6 hrs...then a new problem and new symptoms....distortion ( mid-pitched motorboating) both channels.....
 
devilsindetails

devilsindetails

Member
Joined 2011
DF96 & M Gregg. Thks...for some reason I missed any notifications about your responses to this thread...as you know from previous posts I am (was) relatively inexperienced with Tube (Valve) DIY'selfing and have been working with that little SE EL84 Amp, which I used to replace my Sonic Frontiers Amp after it commenced acting so strangely.

I'll follow the investigative avenues you both suggest.....thanks again fellows!
 
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