Langrex have 2SA872E if you need them. They are pricey on Ebay, but you could try calling and seeing if they sell them for less if you buy direct. I've bought loads of NOS semis and valves from them. They are a trustworthy firm and have probably had the stock for decades.
You can modify the toplogy to use them, but if they're not Laterals, you're talking about a completely different amp. You might as well adopt a design that's intended for them. You will need to think about bias tracking (for one example) , so simply using non-lateral parts in this design is not a straightforward sub.
Hi Guys, regarding my GA28F in my active sub-woofer, it is now regularly blowing a fuse in the power supply ( 3 x fuses in 3 months). It seems to blow the fuse on powering up. I have uprated the original fuses I were using from 2A to 3.15A Time-Lag but these are still blowing after a few weeks of use. I have replaced all the capacitors which has improved the sound quality and is currently sounding better than ever. I didn't replace any resistors. To control the volume, I am using a 200k pot wired as a voltage divider across the input and 0V. The size of the capacitors in my power supply I beleive are 1 Farad (C12 and C13). The speaker is 8-Ohm 150Watt AES. Does anyone have any ideas why this could be happening and what I can do to solve the issue. Many thanks
A 1-Farad capacitor? You sure about that? Is it designed for motor-starting?
Where are the fuses located? Typical rail fuses will be after the caps. If they are before, then it's no wonder that they're being blown!
NB - you will get better SNR if you change the 200K pot for a 10K.
edit - large filter caps mean soft-start circuit is obigatory. You will risk turning your rectifiers into recti-fryers (and they can float across the room like little fireflies - do be warned). Not only that, but your transformer's lams will soon turn into a vibrating mass with that sort of inrush current.
White Dragon was writing at the same time!
Where are the fuses located? Typical rail fuses will be after the caps. If they are before, then it's no wonder that they're being blown!
NB - you will get better SNR if you change the 200K pot for a 10K.
edit - large filter caps mean soft-start circuit is obigatory. You will risk turning your rectifiers into recti-fryers (and they can float across the room like little fireflies - do be warned). Not only that, but your transformer's lams will soon turn into a vibrating mass with that sort of inrush current.
White Dragon was writing at the same time!
On startup the capacitors in the power supply appear to almost be a dead short, until they start to charge.
Happens very quick but regardless start up surge is pretty normal.
Over time it will beat up the bridge rectifier over time.
If it is a new problem the rectifier might be a little tired or the caps.
This is why slow blow fuse is used as well for startup surge.
You can also add a CL60 or proper thermistor before the transformer to reduce surge.
Or a relay soft start. If the transformer isnt massive below 330 VA.
Thermistor is fine, although some will scream and whine about them.
Happens very quick but regardless start up surge is pretty normal.
Over time it will beat up the bridge rectifier over time.
If it is a new problem the rectifier might be a little tired or the caps.
This is why slow blow fuse is used as well for startup surge.
You can also add a CL60 or proper thermistor before the transformer to reduce surge.
Or a relay soft start. If the transformer isnt massive below 330 VA.
Thermistor is fine, although some will scream and whine about them.
1 Farad seems rather large, likely a mis guess. could be 1000u little small or 10,000u about right, but will be a big surge on startup.
If it really is 1 farad. then yes the rectifier is probably been tortured to death and about to go. meanwhile blows fuses.
And even 10,000u would be pretty abusive on a rectifier without soft start.
If it really is 1 farad. then yes the rectifier is probably been tortured to death and about to go. meanwhile blows fuses.
And even 10,000u would be pretty abusive on a rectifier without soft start.
I have used relays for soft-start on 1.5KVA toroidals. Why not? The main consideration is current rating for the resistors that bypass the relay... Don't skimp on them!
1 Farad is the sort of cap you'll find at an automotive supplies shop!
1 Farad is the sort of cap you'll find at an automotive supplies shop!
