A
Anonymous
Guest
So... I just did a build pictorial for a guy I built an amp for. I thought I'd share it so folks could what goes into building a Henning Cherry Bomb. Anyway... let's get into it. Enjoy and feel free to ask questions if you want!
The first thing I do is put the transformers and choke onto the chassis. I also put in the chassis mounted power tube sockets. Obviously I have to route the transformer wires and put in the grommets so the wires don't get cut by the chassis. I also put in the impedance selector and the power on light. If you look at the pictures, I also add some grounding tabs at the feet of the power transformer and you can see there is no powder coating on the chassis there. I'll be running ground wires to those tabs from various places. Those ground tabs don't quite fit on the transformer screws so I have to shave them down a bit... Kind of a pain, but it works.
I also assemble all the parts for the amp from my inventory and put all the metal stuff into that magnetics tray so I don't lose stuff. Works great!
Notice as well that I have the boards already populated. I have a person that works for me that is just incredible at doing the PCBs - does the work much better than I ever could, that is for sure. Attention to detail is amazing - I've never had a board with a misplaced part or any functionality issues. I still have like 15 sets of boards complete for more amps and because of how quickly and accurately this person works, I can get 10 new sets in 3 weeks or so - pretty amazing!
Here are some pics:
Next I start cutting the power transformer leads and twisting them as required to keep them neat and get them set for routing to the power supply (PSU) board. The unused leads are capped and twist tied. This way if someone wants another international voltage, it is no problem to take off the PSU, unsolder some wires and route the new ones:
Now I wire in the power and standby switches and the IEC plug:
I've now wired in the fuse holders and everything is now complete for the PSU board to be put in. You can also see that I twisted the output transformer wires and installed the EFX loop board.
Now I've installed and wired in the PSU board and also wired in the output transformer to the impedance selector and speaker outputs:
OK, now time for the main board to go in. You have to be a bit careful when doing this to make sure that the LEDs line up right and don't get trashed when putting in the board. No problems!:
Here's a bit more detail around the speaker outputs, impedance selector, output transformer - all now connected to the main board:
Now, I finish wiring in the switching jacks. It's a bit complicated, but I have to wire these in to test that the switching is working. I also wired the power supply board to the main board and the main board to the EFX board (you can see the new wires connecting the MIL-STD screw connectors I use on each board - I don't think anyone else is doing this in the amp world!). What's cool about this is once that is all done, I can test the heater and switching supply voltages to make sure the tubes will heat up and that all the switching works.
Here is a shot of the finished wiring for the switching jacks from two views:
And here is a closeup of the complexity of wiring the jacks. I use heavy gauge bare wire to link the three switching jacks so it is ROCK solid:
Here is a shot of the wiring of the main board to the EFX board - just 4 wires, but, allows me to do the heater testing. What is cool is that I use these MIL-STD screw connectors everywhere so that servicing the amp is a breeze - to take out the main board, I just unscrew all the flying leads instead of having to unsolder everything:
OK, now to test the switching. I powered up the amp and you see the big amber main power light is lit and it is a little tough to see, but the green LED indicating the PLEX channel is active is lit:
Now I change the CHANNEL SELECT switch and the amber LED lights indicating the ROD channel is active:
Now I check the SOLO function and you can see (kinda) that the SOLO red LED is lit (it kinda looks amber though in the picture though - was red in person!
Finally, I test the EFX loop switch and see that the blue LOOP LED is lit. I can also hear that the relays are clicking when I switch, which means the boards are good and the switching works!:
Finally, I turn the amp off, pop in the preamp tubes, turn it back on and checked that they all lit up. This picture doesn't show it really, but maybe you can kinda see the orange glow on some of the tubes. They actually all lit up as expected in person, so the DC heaters are working. Measured the AC heaters for the power tubes and the DC heater voltages for the preamp tubes and those are in range. The 6V supply for the LEDs and relays is right as well. The DC heaters and how we did the layout make this one of the quieter higher gain Marshall-style amps you will hear, even cranked!
Next, I wire in the power tube sockets to the main board. This is a really time consuming activity because it is a total of 32 1.5" wires that have to be cut and stripped on both ends (and then tinned) as accurately as possible so it looks good and makes good connections. There isn't a lot of room so you have to be really careful and take your time so as not to burn the board or any other components with the iron. Everything went well and here are a few pics so you can see the job. All solid, tight connections and it looks cool too!:
And one final pic that shows the current status of the whole amp:
Ok, now on to the the hard stuff! The shielded wiring... Definitely the most time consuming part of building the amp. There are 13 shielded wires that have to be put in the amp...
Here is a shot of a just constructed shielded wire:
Here is building the shielded input connection for the input jack:
And here are various views of all the completed shielded connections, including the long shielded wire between the main board and the effects board:
Next I wire in the rest of the pots that don't require shielded wire! Here are a few of pics of the completed wiring. Very consistent wiring and it all looks good and is very solid:
Wired up the footswitch as well. Totally heavy duty case and PCB/aerospace connector wiring:
Popped in the tubes and took a few pics before burn in and testing!
At this point, I do the burn in. I'm not a psycho about this like some people. What I do is just bring up the voltage in 5V increments on my variac over a couple hours until we are at full voltage to make sure everything is cool. I don't want to bring the full power on right from the start just in case of an issue. No problems here though. Next I biased up the amp (~38 ma for this amp with a 461.7 V B+). Here's a pic after biasing. Note the speaker cable coming out of the speaker out. It is connected to my dummy load at 16 ohms. Once the power tubes are in, you always have to make sure you have a load or risk power tube and output transformer damage. When you are just playing a finished amp, it usually isn't an issue because the cab is always connected, but when doing a build, you want to really make sure you don't forget when testing! At this point, I test all the voltages to make sure everything is cool. Everything was perfect in this case!:
Now, onto my favorite part! Firing up the amp and testing it out with a guitar for the first time. I alway set the amp to my standard settings for each channel and master and at first I keep the overall master on the back pretty low.You can't see it but it is actually on (so is my whole rig!) in the second and third pics. I hooked the guitar into my W/D/W rig of doom, plugged in my trusty Music Zoo Nitro Relic Charvel and took it off standby. Checked the PLEX channel first, then the ROD, then the SOLO boost master. Sounds killer to me! The line out is working as verified by the two wet cabs firing and sounding great. All the SATURATION switches and the INTERNAL PLEX JUMP switch work as expected. The footswitch and cable work as well (Note that when the footswitch is hooked up the LOOP, SOLO, and CHANNEL SELECT switches on the front of the amp are disabled. When you disconnect the footswitch, they work). Anyway... wanked around for awhile digging' the tones and also checked it without the two wet cabs - sounds like it should... Here's a few pics of the amp and footswitch wired into my rig:
So... next I need to check out the EFX loop and make sure it works in both Series and Parallel mode. I also need to do some VERY loud (
) testing to make sure it sounds great cranked. That's it!
BTW - you might notice that the second EL34 from the left is a lot taller than the other three. At first I though I was losing it, but I measured them and sure enough, the tube is a little more than a quarter of an inch taller. It is the weirdest thing I've ever seen, but this is a matched quad (plate currents are exact) and everything checks out. Not sure what the deal is, but the tubes are ace and sound great.
Steve
The first thing I do is put the transformers and choke onto the chassis. I also put in the chassis mounted power tube sockets. Obviously I have to route the transformer wires and put in the grommets so the wires don't get cut by the chassis. I also put in the impedance selector and the power on light. If you look at the pictures, I also add some grounding tabs at the feet of the power transformer and you can see there is no powder coating on the chassis there. I'll be running ground wires to those tabs from various places. Those ground tabs don't quite fit on the transformer screws so I have to shave them down a bit... Kind of a pain, but it works.
I also assemble all the parts for the amp from my inventory and put all the metal stuff into that magnetics tray so I don't lose stuff. Works great!
Notice as well that I have the boards already populated. I have a person that works for me that is just incredible at doing the PCBs - does the work much better than I ever could, that is for sure. Attention to detail is amazing - I've never had a board with a misplaced part or any functionality issues. I still have like 15 sets of boards complete for more amps and because of how quickly and accurately this person works, I can get 10 new sets in 3 weeks or so - pretty amazing!
Here are some pics:
Next I start cutting the power transformer leads and twisting them as required to keep them neat and get them set for routing to the power supply (PSU) board. The unused leads are capped and twist tied. This way if someone wants another international voltage, it is no problem to take off the PSU, unsolder some wires and route the new ones:
Now I wire in the power and standby switches and the IEC plug:
I've now wired in the fuse holders and everything is now complete for the PSU board to be put in. You can also see that I twisted the output transformer wires and installed the EFX loop board.
Now I've installed and wired in the PSU board and also wired in the output transformer to the impedance selector and speaker outputs:
OK, now time for the main board to go in. You have to be a bit careful when doing this to make sure that the LEDs line up right and don't get trashed when putting in the board. No problems!:
Here's a bit more detail around the speaker outputs, impedance selector, output transformer - all now connected to the main board:
Now, I finish wiring in the switching jacks. It's a bit complicated, but I have to wire these in to test that the switching is working. I also wired the power supply board to the main board and the main board to the EFX board (you can see the new wires connecting the MIL-STD screw connectors I use on each board - I don't think anyone else is doing this in the amp world!). What's cool about this is once that is all done, I can test the heater and switching supply voltages to make sure the tubes will heat up and that all the switching works.
Here is a shot of the finished wiring for the switching jacks from two views:
And here is a closeup of the complexity of wiring the jacks. I use heavy gauge bare wire to link the three switching jacks so it is ROCK solid:
Here is a shot of the wiring of the main board to the EFX board - just 4 wires, but, allows me to do the heater testing. What is cool is that I use these MIL-STD screw connectors everywhere so that servicing the amp is a breeze - to take out the main board, I just unscrew all the flying leads instead of having to unsolder everything:
OK, now to test the switching. I powered up the amp and you see the big amber main power light is lit and it is a little tough to see, but the green LED indicating the PLEX channel is active is lit:
Now I change the CHANNEL SELECT switch and the amber LED lights indicating the ROD channel is active:
Now I check the SOLO function and you can see (kinda) that the SOLO red LED is lit (it kinda looks amber though in the picture though - was red in person!
Finally, I test the EFX loop switch and see that the blue LOOP LED is lit. I can also hear that the relays are clicking when I switch, which means the boards are good and the switching works!:
Finally, I turn the amp off, pop in the preamp tubes, turn it back on and checked that they all lit up. This picture doesn't show it really, but maybe you can kinda see the orange glow on some of the tubes. They actually all lit up as expected in person, so the DC heaters are working. Measured the AC heaters for the power tubes and the DC heater voltages for the preamp tubes and those are in range. The 6V supply for the LEDs and relays is right as well. The DC heaters and how we did the layout make this one of the quieter higher gain Marshall-style amps you will hear, even cranked!
Next, I wire in the power tube sockets to the main board. This is a really time consuming activity because it is a total of 32 1.5" wires that have to be cut and stripped on both ends (and then tinned) as accurately as possible so it looks good and makes good connections. There isn't a lot of room so you have to be really careful and take your time so as not to burn the board or any other components with the iron. Everything went well and here are a few pics so you can see the job. All solid, tight connections and it looks cool too!:
And one final pic that shows the current status of the whole amp:
Ok, now on to the the hard stuff! The shielded wiring... Definitely the most time consuming part of building the amp. There are 13 shielded wires that have to be put in the amp...
Here is a shot of a just constructed shielded wire:
Here is building the shielded input connection for the input jack:
And here are various views of all the completed shielded connections, including the long shielded wire between the main board and the effects board:
Next I wire in the rest of the pots that don't require shielded wire! Here are a few of pics of the completed wiring. Very consistent wiring and it all looks good and is very solid:
Wired up the footswitch as well. Totally heavy duty case and PCB/aerospace connector wiring:
Popped in the tubes and took a few pics before burn in and testing!
At this point, I do the burn in. I'm not a psycho about this like some people. What I do is just bring up the voltage in 5V increments on my variac over a couple hours until we are at full voltage to make sure everything is cool. I don't want to bring the full power on right from the start just in case of an issue. No problems here though. Next I biased up the amp (~38 ma for this amp with a 461.7 V B+). Here's a pic after biasing. Note the speaker cable coming out of the speaker out. It is connected to my dummy load at 16 ohms. Once the power tubes are in, you always have to make sure you have a load or risk power tube and output transformer damage. When you are just playing a finished amp, it usually isn't an issue because the cab is always connected, but when doing a build, you want to really make sure you don't forget when testing! At this point, I test all the voltages to make sure everything is cool. Everything was perfect in this case!:
Now, onto my favorite part! Firing up the amp and testing it out with a guitar for the first time. I alway set the amp to my standard settings for each channel and master and at first I keep the overall master on the back pretty low.You can't see it but it is actually on (so is my whole rig!) in the second and third pics. I hooked the guitar into my W/D/W rig of doom, plugged in my trusty Music Zoo Nitro Relic Charvel and took it off standby. Checked the PLEX channel first, then the ROD, then the SOLO boost master. Sounds killer to me! The line out is working as verified by the two wet cabs firing and sounding great. All the SATURATION switches and the INTERNAL PLEX JUMP switch work as expected. The footswitch and cable work as well (Note that when the footswitch is hooked up the LOOP, SOLO, and CHANNEL SELECT switches on the front of the amp are disabled. When you disconnect the footswitch, they work). Anyway... wanked around for awhile digging' the tones and also checked it without the two wet cabs - sounds like it should... Here's a few pics of the amp and footswitch wired into my rig:
So... next I need to check out the EFX loop and make sure it works in both Series and Parallel mode. I also need to do some VERY loud (
) testing to make sure it sounds great cranked. That's it!BTW - you might notice that the second EL34 from the left is a lot taller than the other three. At first I though I was losing it, but I measured them and sure enough, the tube is a little more than a quarter of an inch taller. It is the weirdest thing I've ever seen, but this is a matched quad (plate currents are exact) and everything checks out. Not sure what the deal is, but the tubes are ace and sound great.
Steve
