Power transformer wire grouping help

[geoff 1965]

get a 2W 220K metal film resistor so you can add a bleed to the dual can capacitor,for safety this bleeds the voltage from the capacitors to ground when you switch the amp off.

[davemojo]

get a 2W 220K metal film resistor so you can add a bleed to the dual can capacitor,for safety this bleeds the voltage from the capacitors to ground when you switch the amp off.

ahah ok here I need to understand what do you exactly mean by adding 2w 220k metal film resistor.

Where do I exactly need to put it ? Please? As you may understand my knowledge with electronics is limited and I am learning while doing it.

Could you further clarify ?

[davemojo]

get a 2W 220K metal film resistor so you can add a bleed to the dual can capacitor,for safety this bleeds the voltage from the capacitors to ground when you switch the amp off.

ahah ok here I need to understand what do you exactly mean by adding 2w 220k metal film resistor.

Where do I exactly need to put it ? Please? As you may understand my knowledge with electronics is limited and I am learning while doing it.

Could you further clarify ?

I have used so far in general in this build carbon composite resistors, but other mentioned that it means noise. However the original was built with carbon composite, so question is how true and how bad is the noise you get?

I am sure it depends also on how well is the amp built and what specific technique are used to reduce the noise.

It seems that film resistors are better choice, maybe on my next build I'm going to use metal resistors.

[geoff 1965]

https://18watt.com/files/JMPGuitars_18_ ... Layout.pdf
have a look at this layout,the 220K goes between the first positive and negative lugs of the 32/32uf capacitor.negative goes to ground so when you switch off the voltage stored in the capacitor bleeds off.

[davemojo]

https://18watt.com/files/JMPGuitars_18_ ... Layout.pdf
have a look at this layout,the 220K goes between the first positive and negative lugs of the 32/32uf capacitor.negative goes to ground so when you switch off the voltage stored in the capacitor bleeds off.

Very easy cool got it. In other words is going to discharge that capacitor off to the ground, got it ! Thanks

[davemojo]

https://18watt.com/files/JMPGuitars_18_ ... Layout.pdf
have a look at this layout,the 220K goes between the first positive and negative lugs of the 32/32uf capacitor.negative goes to ground so when you switch off the voltage stored in the capacitor bleeds off.

Would this kind work? Metal Oxide 220 kOhm that is what I found at Tonefactory?

[geoff 1965]

metal oxide will be okay,you want 2 watt rating.
looking at the layout did you notice the difference with the grounds in the mains/power section to the stewmac layout?

[davemojo]

The instructions don’t match the schematic,
The blue & orange wires are’nt used so either cut them short and seal the ends with heatshrink or solder to an unused isolated tag.
Black is mains negative and white is mains positive “240V”
Ez81 rectifier filament are grey & pink,
The yellow and green/yellow are your centre taps for the heater filament and HT so they are soldered to ground at your star ground point.

Sorry more questions, since I fee unsure:

In my case now I must run the black wire to the mains switch and the white toward the fuse holder which is than bridged to the power inlet, correct?

See picture to check what I exactly mean since the power transformer leads are not matching what I am following as a guide

[davemojo]

metal oxide will be okay,you want 2 watt rating.
looking at the layout did you notice the difference with the grounds in the mains/power section to the stewmac layout?

The resistor is 2 watt. In stewmac the ground is on the 3 lugs ground attached on the corner of the power transformer and this is how I did it, so I guess I should run the wire from the capacitor can to this 3 lugs ground, or shall I attach a ground on the V6 pot on the screw nut?

[geoff 1965]

add a pic of your mains socket & fuse,first you need to determine the orientation of the mains lugs i.e. which is positive and negative,also if you have a solder lug i would ground the mains socket seperately close to its mounting.
been trying to find any feedback on this stewmac with no success,i don't have the tremolo circuit in either of my amps but i know from watching other builds you have to be very careful with both grounding and lead dress or you will have problems.
transformers can vibrate so the mounting bolts are not ideal grounding points,as a rule the preamp & pots ground seperately close to the input jacks,the power section/transformer centre taps/dual capacitor have a star ground point and the mains input has a seperate grounding point.
you have to be careful working from layouts

[davemojo]

add a pic of your mains socket & fuse,first you need to determine the orientation of the mains lugs i.e. which is positive and negative,also if you have a solder lug i would ground the mains socket seperately close to its mounting.
been trying to find any feedback on this stewmac with no success,i don't have the tremolo circuit in either of my amps but i know from watching other builds you have to be very careful with both grounding and lead dress or you will have problems.

As you can see the black and the white are the mains one is positive one is negative. Not sure which one is which.
at this point looks like the black goes to mains switch and the white goes to fuse holder and from there with a jumper to power inlet.

I also ran the yellow from stand-by switch to pin 3 of V6. In addition one more wire a jumper from lug left on mains switch down to the other lug of the power inlet.

[geoff 1965]

i would run a wire from the negative mains lug to the tag pointed out on pic,then you wire one of the pilot light leads and the black transformer wire to the same tag. if you move the other tag strip to the cap mounting bolt "see pic" you can use that as your star ground point.

0b15481c-0029-4cc4-843c-b8d712923e00.jpg

[davemojo]

i would run a wire from the negative mains lug to the tag pointed out on pic,then you wire one of the pilot light leads and the black transformer wire to the same tag. if you move the other tag strip to the cap mounting bolt "see pic" you can use that as your star ground point.
0b15481c-0029-4cc4-843c-b8d712923e00.jpg

Thank you, I am getting a little lost I didn't realize that the power transform wire were different , I thought they would be all the same color for all power transformer versions.

Now I can do what you said but this will change everything else and will not allow me to continue on my own.

I need to understand the black and the white on my transformer to what stewmac color do match? In order to try to continue using that same schematic.

I noticed that all USA schematic have the power transfer colors do not match the power transformer I bought here at Tonefactory

Is the way you proposed better technically speaking?

[davemojo]

i would run a wire from the negative mains lug to the tag pointed out on pic,then you wire one of the pilot light leads and the black transformer wire to the same tag. if you move the other tag strip to the cap mounting bolt "see pic" you can use that as your star ground point.
0b15481c-0029-4cc4-843c-b8d712923e00.jpg

Ok I understood the way you proposed is actually a different method to achieve the same.

However the white wire on my PT is the 240v which is basically what stewmac has in black/white 120v which basically is not matching or they have the black/red which is the 240V, so in other words the white is the match for the black/white or red/black in stewmac, so based on that I can follow that schematic.

I understand your point, for you it may be very easy for me isn't strugling a lot, so... let's hope I can make something working fine

[geoff 1965]

the confusion is just different wire colours on the PT, if you wire the negative like shown it will be good.then you can wire the positive lug to the fuse holder lug as shown "in red" then from other fuse lug to the power on/off switch,when you run lengths of ac wire push it into the corner of the chassis tight around then up to the switch.then you can wire the white transformer lead and second pilot light wire to the second switch lug.
the unused blue & orange wires can be cut short and soldered to the isolated tag "see pic" and you can earth the mains with a lug at point shown "green"
this is just helping you with mains/PT wiring and relocating the ground points is good practice,it won't affect the rest of the build but it's up to you to decide.

0b15481c-0029-4cc4-843c-b8d712923e00.jpg

[davemojo]

the confusion is just different wire colours on the PT, if you wire the negative like shown it will be good.then you can wire the positive lug to the fuse holder lug as shown "in red" then from other fuse lug to the power on/off switch,when you run lengths of ac wire push it into the corner of the chassis tight around then up to the switch.then you can wire the white transformer lead and second pilot light wire to the second switch lug.
the unused blue & orange wires can be cut short and soldered to the isolated tag "see pic" and you can earth the mains with a lug at point shown "green"
this is just helping you with mains/PT wiring and relocating the ground points is good practice,it won't affect the rest of the build but it's up to you to decide.
0b15481c-0029-4cc4-843c-b8d712923e00.jpg

Yes, I got it now and I understand the first option you offered may go that way, tomorrow I can dedicate some hours and go ahead with the project. I really don't know how to thank for your patient on helping out and clearing out any doubt, again thanks

[davemojo]

Hey All

I made some progress this is how far I got so far.

[Bieworm]

Hey. Nice to watch the progress. It isn't advisable to solder the pots bodies to ground. It's easy to damage the pots like that. Watch the grounding tips in Josh’s signature. Look at photos of Josh’s builds. Trust me, you'll benefit from this on the end results.
You might wanna look into the determination of the orientation of the caps too,not only the electrolytic caps. There is an outer foil side in every cap. But you need a scope for that ...or d@mn good ears...
This is not a major problem, but it's still better practice.
Don't worry... take it slow and thourough.
Ok, now I'll stop being verbose

[TriodeLuvr]

Hey All

I made some progress this is how far I got so far.

Unless I'm mistaken, you've connected the grounds on the jacks to the chassis through those pot shells. That's begging for a ground loop. I would clean all that up before continuing. It doesn't benefit the amp for the shells to be connected into the circuit; they'll act as shields just because they're mechanically attached to the chassis.

Jack

[davemojo]

Hey. Nice to watch the progress. It isn't advisable to solder the pots bodies to ground. It's easy to damage the pots like that. Watch the grounding tips in Josh’s signature. Look at photos of Josh’s builds. Trust me, you'll benefit from this on the end results.
You might wanna look into the determination of the orientation of the caps too,not only the electrolytic caps. There is an outer foil side in every cap. But you need a scope for that ...or d@mn good ears...
This is not a major problem, but it's still better practice.
Don't worry... take it slow and thourough.
Ok, now I'll stop being verbose

My soldering technique isn't great but I paid some attentions on soldering over the pot.
I agree with all of you since it makes sense ground loop hum, sure but why the orginal 18 watt use similar schematics as soon as i can I will send here a picture of the 74x Amp 18 watts my friend owns one, I also seen other schematics doing the same soldering on pot shell.

Some other schematic don't and discourage this practice