JTM 45/100 - Build story

[Xplorer]

George probably did it right, but the letters on the mustards can't be an indication of this outer side foil actualy ... it varies, from what i know.

Yeah Karlis, but the previous parts were equal in pleasure ^^

[Xplorer]

Damn !!! I measured the rida 33uf at about 41-42 uf !!!
Should i continue with them ?

[BoogieEngineer]

Damn !!! I measured the rida 33uf at about 41-42 uf !!!
Should i continue with them ?

That makes the sound a little stiffer, but not by much I guess. I'm not too anal so I would use them and not have the delay

[Xplorer]

i have two old RS 32uf which measure ..... 32 uf !

[VintageCharlie]

The original RS would have been off nominal value by even more = more authenticity
but 10uF is quite a lot for modern caps.

[Xplorer]

Are they gonna stick to the right value maybe once they'll receive some current ( as they're new ) ?

i'm not sure what to do.
ordering some F&T black or something ?

[BoogieEngineer]

Are they gonna stick to the right value maybe once they'll receive some current ( as they're new ) ?

i'm not sure what to do.
ordering some F&T black or something ?

I remember Neil told me not to bother with F&T stuff for whatever reason he has. Never try them though

[neikeel]

Hi Adrien

Want to part with those 32uFs?

I have 6 and need 2 more

[neikeel]

Are they gonna stick to the right value maybe once they'll receive some current ( as they're new ) ?

i'm not sure what to do.
ordering some F&T black or something ?

I remember Neil told me not to bother with F&T stuff for whatever reason he has. Never try them though

F&T are not bad, but if you can get RIFAs I would stick with those.

[Xplorer]

i don't like to have such specs. But what should i do ? i haver no idea of how it would transform the sound compared to an original.

i also noticed that the 0,056uf 1000v red cap is measured 0,082uf.

[VintageCharlie]

Larry says it's recommended to reform even new electrolytics, as they often have been held for a couple of years in storage, etc. There are Larries instructions on the forum as to how to do that with the caps installed in the amp already - that's supposed to be the most secure way to do it.

As for the mustard orientation - to be honest, i don't remember which end had to go where, but it is explained in the aiken link mentioned here. As i don't have a scope, i connected each cap between ground and hot wire of an audio cable, which i put into my pc's soundcard. I put the cable of a 100w table lamp underneath the cap, while the lamp was turned on / this increased some noise in the signal i heard from the sound card. You have to tap the cap with fingers, then switch the hot and ground wires (orienting the cap the other way) and tap again. One of the sides will be slightly louder, noisier - mark the lead wire of that end to know which one it was.

[VintageCharlie]

Adrien, the Erie snubber cap i used also was a bit off spec (the only part in the amp that was off nominal value bvy more than 3% ), but i don't think that it really matters much in that spot. The grey RS and red Erie caps are notorious for their unreliability and off spec values.

[Xplorer]

thanks. Yes i discussed with Dom who explained to me what was confusing to me;
actualy it seems that there's no need to put the AC cable near the cab.
needed : a gain meter ( i think i'll try with cubase , my amp going into the sound card through an spl transducer ) , and a jack plugged into the amp on one side and the two wires connected to each side of the cap. then tap on the yellow part of the mustard ( i made a confusion with the leads of the cap ) , to see in which configuration it produces more noise ( 4-7 db ) . when you know which configuration produces the most noise : mark the lead side which was connected to the tip of the jack : this is the outer foil.

then, on a 45/100, the two V1 caps have the outer foil toward the tube side of the amp.
the two V2 caps, toward the knobs side.
The next 0,022uf and 0,1uf go toward the knobs also.
the two last 0,1uf go toward the tubes.
the presence cap 0,1uf has the outer foil directed to the ground .

[BoogieEngineer]

So what effect would you have if you had them in reverse direction?

[Xplorer]

more noise ! but this isn't supposed to be a very big deal. Just want to make it right if i can.