First Gainclone...

[w00t1985]

Hey ya'll...starting to order the parts that I'll need to build my first gainclone. First, I've got some mur860 diodes on the way for the rectifier. Heard those are good performers. Also, have this transformer on the way. 625VA 25V+25V. Should be pretty good, eh?

Questions though...
I'd found some before, but can't see to come accross them again. I'm having trouble finding, and not totally sure what to get, as far as a socket to use for the mains connection, also unsure about a fuse, and power button. I have plenty of extra computer power cords around, so a socket that would use that would be cool. If it's ok, I could prolly pull one out of an old computer PSU to use? I'd rather purchase a quality one though.

As for the power button, something like this would be cool to use:
Illuminated Push Switch.
My question is, since it says its a momentary switch. So how would I wire that up? Would something like this work better:
Rocker Switch
But then that is rated for 12V... Unsure

Other than that, am I forgetting anything for the PSU? I'd like to get that done with first, then move on to the amp stage. Also, the PSU will be in a separate chassis from the amp, so what should I use as an umbillical cord?

Thanks for the help...
w00t!

[ofb]

forget the 12vdc switches. you can get the second style that you showed in 120vac. mouser has them, and likely digikey too, as well as your local parts supply house.

the computer-style power socket you're referring to is the IEC style, and yes that's fine. again, mouser & digi have a selection of these. also you can get them with the fuse holder built in. that might be a real good idea for your first box. 120vac is not something you want to mess up with. you want to be quite sure you've got things wired right.

for the umbilical and for not forgetting things in the psu, head over to the decible dungeon. you have read right throught it all at least once, right? it's very helpful.

[Nuuk]

A momentary switch is one that only makes contact while you press it in.

So I suggest sighting your GC in between your speakers if you want to listen in stereo!

I am also wondering about your turn on thump with that massive transformer!

[w00t1985]

Originally posted by Nuuk
A momentary switch is one that only makes contact while you press it in.

Yea, I know it only makes contact while I press it, so I wasn't sure how I'd wire it to keep things on...But I found a nice looking rocker switch at Mouser.

So I suggest sighting your GC in between your speakers if you want to listen in stereo!

Confused...

I am also wondering about your turn on thump with that massive transformer!

Well I can include the circuit to do the soft start, can't I? I mean, for the larger VA it wasn't much extra cost, so I figured why not have more than too little...

Like I said, I found a good switch at Mouser, but am having a bit of trouble navigating the site to find the IEC socket with fuse. These big warehouse sites are too confusing I tell you

Ah well, maybe I'll just request the printed catologue, that way I can have a picture of everything...

[ofb]

yeah, get the catalogue. mouser has an excellent catalogue. digi's isn't as nice, but their website's Search is better. an evening with the catalogues open and the computer on will give you a much better idea of what's available to you.

[w00t1985]

Awesome, thanks for the help. Hopefully that catalogue will get here soon since some of the other stuff is already on the way. May also have to head down to the local RatShack to see what they have in stock...

[Sandy H.]

As an aside with regard to the momentary switch use, I built a test circuit using a tactile momentary switch to trigger a flip-flop whose output went to a transistor to power the coil of a relay. The flip-flop was configured to act as a latch.

The test circuit worked, but all of my calculations were a mile off. That kind of ticked me off so I haven't actually made the 'real' circuit. I'm a mechanical engineer and the EE classes I took obviously taught me enough to get in trouble, but that's a while ago too. I'm sure I just butchered Kirchoff's law here or there.

Anyway, I guess my point was that it is possible to use the momentary switch in at least one method. Other options for the circuit could include the use of a timer or similar to allow delayed turn-ons for multiple relays etc.

But RatShak will also likely have a 120V rocker etc.

Sandy.

[w00t1985]

Well, a push button has to be possible, it's what computers use to turn on. That's what that one was designed for, and it looks pretty cool. Maybe I'll just ask my EE teacher in class on tuesday, see if he has a good solution.

Also, are there any major benefits to useing a full bridge rectifier on each rail? I've seen some designs use dual rectifiers, one between positive and ground, and another between negative and ground. I wasn't thinking and ordered four MUR860 diodes, and they just came today. Would it really be worth the extra $15 to order four more?

Thanks

[Sandy H.]

Check into JK flip flop on google and it'll show what I did. For kicks, I might drag it back out this weekend and figure out my calculation errors and design the real version.

I built a bench supply and used a center tap transformer with only 1 rectifier. I imagine you could do the same thing with the GC and MUR diodes, but I'm not sure the BrianGT board will work without some jumpers. If nothing else, you can grab a rectifier locally and try it first.

Sandy.

[BlackDog]

Originally posted by w00t1985
Well, a push button has to be possible, it's what computers use to turn on. That's what that one was designed for, and it looks pretty cool. Maybe I'll just ask my EE teacher in class on tuesday, see if he has a good solution.

I believe a latching relay might be the easist way to implement this. Whatever happens, you'll probably need another transformer to drive the "switch on" circuits.

Also, are there any major benefits to useing a full bridge rectifier on each rail? I've seen some designs use dual rectifiers, one between positive and ground, and another between negative and ground. I wasn't thinking and ordered four MUR860 diodes, and they just came today. Would it really be worth the extra $15 to order four more?

With a dual sendary transformer, it's definitely worth using two bridges if you can.
The alternative involves tieing the two secondary outputs together to create a virtual earth (and connecting that in turn to mains earth), and connecting the bridge across the remaining secondary leads.

Steve