First post, my “new” 18W

[JMPGuitars]

I like capacitance charts like this: http://www.electronicsteacher.com/capacitor-chart.php

The code guide shows the relevant codes, so you can figure out the logic behind the numbers, and then you don't need to check the chart as often.

[Skydog6653]

I installed the new components yesterday. What are the style/type of resistors on the jacks, tubes, & pots? V1 has 4/33.8K R's, V2 has 1/470KR. Each High input jack has a 1M R. The V&T pots on the Marshall channel share a 100 K R. The V pot on the TMB channel has a 83 K R. Should I retain this setup as is? @Geoff 1965 which cap does the 25uf 50V take the place of? The amp still has a noticeable hum to it that goes up with the V knob. It did not squeal but when I put it on standby there was a “microphonic” pop. Sorry, I don't know how else to describe it. I feel like I'm getting there!

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[JMPGuitars]

Your ground scheme is still a little off. The pots and preamp section should be grounded near the input jack. It should not be grounded near the power amp section or transformers. Non-insulated wire should only be used on the buses. It should not be used free floating from the pots to the ground as it is currently. Make sure your pots and inputs are only grounded once, and all together via/near the input jack.

See my post for more info, and associated layout here: viewtopic.php?f=4&t=25372

Thanks,
Josh

[geoff 1965]

hello skydog,
the resistors on the jacks and tube sockets are carbon film and should be okay,i've circled in "white" where the capacitor 25uf/1K5 resistor go,check the wire goes to pin3 of V1 and remember the positive side of the capacitor goes to the tube socket.
there is a couple of area's you need to address, if you replace the large corbon comp resistor with a new carbon film 8K2 like you've done on the other side "circled" that will make the power section good.
also the green 8K2 next to the 1K's was a wirewound B+ dropper and it looks like you've replaced it with a 1W carbon film,you need to put the wirewound back in there or use a new 2 or 3 watt metal film.just check the turrets i've circled in "red" are not joined together,it's hard too see on the pic.
also check the sozo cap has a good connection to both turrets,what wattage is your soldering iron?

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[Skydog6653]

I am waiting on a replacement iron for my Hakko 936. I was trying to get by with a 30W China special. I know some of the joints look bad. I'm going to remelt them with the new iron.

[geoff 1965]

sound's good,remember to use your heatsinks when you reflow the turrets.we can look at your channel 1 tonestack & input grounding then.

[Skydog6653]

Thanks, guys.

[geoff 1965]

just try this for a temporary fix and see if it helps with the hum,cut the wire and resolder i've arrowed on the pic,this will seperate the bias ground from the rail. check with your multimeter for continuity to the chassis from both the turrets marked before powering up the amp.

F6FB6D7A-00E7-43A3-91B0-EA00F31B5009 (1).jpeg

[JMPGuitars]

just try this for a temporary fix and see if it helps with the hum,cut the wire and resolder i've arrowed on the pic,this will seperate the bias ground from the rail. check with your multimeter for continuity to the chassis from both the turrets marked before powering up the amp.
F6FB6D7A-00E7-43A3-91B0-EA00F31B5009 (1).jpeg

Don't do this. The power amp/bias ground is fine, but it should go to the star ground. The power section/bias grounds should never go to the pots.

[geoff 1965]

i was using this "richie" revised TMB layout from the downloads Josh,it has a bus rail showing grounding from the power section/pots and the bias on a seperate ground point.that's what i meant by "temporary fix" to see if seperating the bias ground affects the hum.

18_Watt_TMB (1).pdf

[JMPGuitars]

i was using this "richie" revised TMB layout from the downloads Josh,it has a bus rail showing grounding from the power section/pots and the bias on a seperate ground point.that's what i meant by "temporary fix" to see if seperating the bias ground affects the hum.
18_Watt_TMB (1).pdf

It's better to stick with the modern scheme, especially when chasing hum. Cleaner is always better.

[Skydog6653]

The schematics and pdf's are great and very helpful. Does anyone have any “gut shots” pics of a similar amp with the grounding done correctly? Geoff 1965, earlier you had suggested using a 2W 220 K metal film resistor to bleed a cap. I can't find one listed anywhere. Where would that install? Also, I can't find a 2 or 3 watt 8K2 metal film resistor for the B+ voltage. I do still have the original green one. I'm preparing an order to include 12 awg bare bus wire, and 22 awg black stranded wire. I can't thank you guys enough for all the help. When I'm not stressing out over it, it's actually very relaxing!

[JMPGuitars]

The schematics and pdf's are great and very helpful. Does anyone have any “gut shots” pics of a similar amp with the grounding done correctly? Geoff 1965, earlier you had suggested using a 2W 220 K metal film resistor to bleed a cap. I can't find one listed anywhere. Where would that install? Also, I can't find a 2 or 3 watt 8K2 metal film resistor for the B+ voltage. I do still have the original green one. I'm preparing an order to include 12 awg bare bus wire, and 22 awg black stranded wire. I can't thank you guys enough for all the help. When I'm not stressing out over it, it's actually very relaxing!

Look at my layout again: files/JMPGuitars_18_Watt_Lite_2b_Layout.pdf

The 220K goes on the cap can, same as my layout.

Here's a wirewound resistor 8.2K/3W.

You can use wirewound or metal film or metal oxide there. I usually use Vishay/Dale or Xicon.

Thanks,
Josh

[geoff 1965]

if you get some grounding washers "small washer with a solder lug" with the wire you can use them for a star ground.
the bleed resistor goes across the positive & negative terminals of the dual can capacitor "see layout"

18W_LITE2B_LAYOUT_BrownNote_TRANS_FINAL_v1.1 (1).jpg

the valvestorm layout you posted shows a star ground and is closer to your layout than the lite2 so have a look at both for the grounding.
you're getting there!

[crgfrench]

I can't find a 2 or 3 watt 8K2 metal film resistor for the B+ voltage.

Use metal oxide for your 2 & 3 watt resistors; tube depot has them for fifteen cents each.

[Skydog6653]

Question, guys; when I first power up the amp, the V4 EL84 glows brightly for an instant, then dims down to match the other (V5 EL84) power tube. Is this normal, or is it indicative of an issue. The tube in question is a new JJ.

[JMPGuitars]

Question, guys; when I first power up the amp, the V4 EL84 glows brightly for an instant, then dims down to match the other (V5 EL84) power tube. Is this normal, or is it indicative of an issue. The tube in question is a new JJ.

It's not normal at all, and it's a fault in different batches of JJ tubes. I don't recommend JJ EL84 tubes at all. I posted this video 6 years ago: https://www.youtube.com/watch?v=21G6TkukwY8

Obviously they've still got issues if your tube is new.

Thanks,
Josh

EDIT: I use new issue Tungsol, Mullard, or TAD for EL84s.

[crgfrench]

Simple test to see if it's the tube or the circuit: swap tubes in sockets 4 & 5 and see what happens

[Skydog6653]

Problem moved to socket 5, so it's the tube; JMP, it behaves just like the one in your video.

[JMPGuitars]

Problem moved to socket 5, so it's the tube; JMP, it behaves just like the one in your video.

Return the set if you can and get a different brand.