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5e3 Newbie could use a little advice


 
3/28/2005 7:56 PM
Frenster
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5e3 Newbie could use a little advice
Hi, I just received my Mission 5e3 kit and am a newbie to amp building. I have a few questions that would help my build.  
 
 
 
I'll start with this. How long should the leads be from the board? I don't want to make them too long for fear of running out of wire, and I don't want to make them to short so that they don't reach their destination. Is there a good rule of thumb on this?  
 
 
 
Great board, btw.
 
3/29/2005 4:02 AM
James P
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Frenster  
 
You don't need to make the flying leads too long as the chassis is small and wiring is a tight fit. I cut mine about 4" and then cut and solder to fit. If you use the method of putting the heater wires above the sockets ala Victoria Amps, you can leave the wires this length and tuck them around the chassis, other wise it's probably better to trim them to the proper length to minimise the AC from the heaters getting into your signal path. Make sure that any heater wires that need to cross others do so at 90 degrees to minimise noise entering the circuit. Don't run them along other wires.  
 
Regards  
 
James P
 
3/29/2005 4:53 AM
Frenster
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Thanks, James. Like I said, I'm a complete novice at this so forgive my ignorance while I learn and the coming stupid question.  
 
 
 
Which are the heater wires?
 
3/29/2005 5:05 AM
James P
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Frenster  
 
The heater wires are the 6.3v (green, although not always - If it's a mission kit they should be) secondaries coming from the transformer. These are what supply power to the cathode filament in the valves in order for the valve to work. Secondaries are called this becuase they are the wires coming from the tranny after the voltage has been changed(Transformed. The wires going into the transformers (both mains and output ones) are called primaries - these supply the neccessary elements for the transformer to 'transform' the power to what is required.  
 
By the sounds of it, you should read up on a few things before attempting to build the amp. I know how tempting it is to get stuck in, but some patience to familiarise yourself with how things work and why, as well as safety procedures will benefit long term, especially regarding your health. I cannot emphasise enough how important it is to know that these amps will contain 350vdc+ enough to kill twice over!!!  
 
Be careful - believe me, the rewards ARE worth it.  
 
Hope this helps  
 
James P
 
3/29/2005 6:51 AM
James P
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Sorry, I forgot to add that you also have heater wires for the rectifier. These are different than the rest as they have different power requirements. The heaters for the 5Y3GT require only 5vac to run but this runs at around 2A current (a lot!!) whereas the other valve heaters run in ma (milliamps - a 1000th of an amp). These heater wires are still secondaries though.  
 
When dealing with valves the first number is USUALLY the heater voltage needed to run the valve. i.e. 5Y3GT = 5vac, 12AX7 = 12.6vac but because the valve is a 'dual' triode (basically two triode valves in one case) each half needs to be supplied seperately = 6.3vac  
 
Regards  
 
James P
 
3/29/2005 12:40 PM
Frenster
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Thanks, James. I'm taking it real slow and reading as I go. I understand the safety precautions like letting the caps drain before going in. I'm a pretty quick study, and I have a strong attention to detail, so I'll plod on and ask questions as I go. Thanks for the quick lesson. I cleared up a lot for me.
 
3/29/2005 12:27 PM
Tim
I had the same worry, but there was plenty of wire to complete the kit.  
 
I just set the board in the chassis and wrote down rough estimates of how mush extra I needed to leave to route the wires. I added an extra inch or two to that estimate to be safe.  
 
It turned out that nearly all of my wires were WAY too long, but I never ran out of wire. Some were actually so long that I was able to re-use the wire I cut off in other areas of the kit!  
 
I still haven't finished the chassis wiring page (work's been hectic), but there's some other details of my build available here:  
 
http://home.comcast.net/~tklein8488/5E3  
 
---  
Tim
 
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