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

[M Gregg]

Originally Posted by DF96

Sounds more like protection circuitry than reservoir caps.

I agree,

Is there any regulation in this amp..could be cutting out on overcurrent or thermal overheat?

Regards
M. Gregg

[M Gregg]

Originally Posted by devilsindetails

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?

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

[M Gregg]

The only other thought,

I guess the heaters remain on during this fault?


Regards
M. Gregg

[KAMonnig]

Take a look at the assembly manual/schematic for the Assemblage ST-40. Looks like the power amp part is essentially the same

[devilsindetails]

Originally Posted by Braga

Hi,
They look exactly the same as the SFS 40 power amp. main caps.
Value is 1700uF/300 V x 2 in series.

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]

Originally Posted by KAMonnig

Take a look at the assembly manual/schematic for the Assemblage ST-40. Looks like the power amp part is essentially the same

Thanks...no the cap values, among many others, are quite a bit different. But thanks again....

[devilsindetails]

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!