Jet City JCA50H - Headfirst Mod DIY Guide
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- เผยแพร่เมื่อ 26 ก.ค. 2024
- Full walk-through, and some intro tones for the Headfirst mod to the JCA50H as demoed in this clip, and another video on this channel. See headfirstamplification.com/am... for downloadable schematic, pictures and DIY etc.
0:00 - Intro
1:58 - Crunch Channel
4:25 - Overdrive Channel
9:30 - Hi res pics, mod instructions
headfirstamplification.com - เพลง
I've got a jet city 100 that Is pretty much a slo 100 now from caps, pots, transformers etc.. and it sound just as tight as the 50. Killer video bud! Keep it up!
Great tones, and thanks for sharing and going through what you did!
Yes some very nice tones on display here!
Another really cool video man! I’ve got a modded JCA50 myself so this was really interesting.
Thanks Dan, glad you enjoyed it man!
Very cool Jason thanks heaps for doing this!
Thanks for this Jason.
Uffffff! Maravilloso! Increíble video. Gracias Jason!! Monster en mi jca22h, same preamp of 50h. Thks thks thks!
Awesome!!
Thank you for the explanation!
You're welcome!
love the t shirt
Amazing video and MOD..., Does it work with the same schematics and components for jca22h ?
RAGE AGAINST THE MACHINE HELL YEAH
Noticed there is a capacitor missing on c26? Is this part of the mod? My stock jca50 has a cap there.
Is it normal that sound flubbs out with mv past 1 oclock? Mine gets oversaturated and sound like shit, and i find that around 12 o clock is sweet spot.
So is this the SLO mod specifically or is it some values and parts you found really improve the amp?
Hi, it's more taking it to the Suhr SE100 think - the Aldrich mod.
I am wanting to do this mod but it looks like the website/schematic isn’t available anymore. Is there a place i can find that?
It's still there. On the Mods page.
I have done this Mod to my JCA50h and now the Gain of the normal Channel bleeds in the Overdrive Channel. Is there a solution ?
the problem is r42...a solution could be to add a relay that disconnects the potentiometer from ground
MODS (for reference):
C32 - Replace with 2.7k||.68u 50V electrolytic capacitor (negative toward the word C32
R49 - REMOVE
R46 - Leave 220k 1W carbon film resistor in place and add a 120pF 500V Mica capacitor in parallel
R45 - Leave 2.2k 1W carbon film resistor in place and add a .68uF 50V capacitor in parallel (neg toward “FS” node)
C30 - Add a 2.2n 630V MP polyester film capacitor
R42 - JUMP
R39 - Add 220k 1W carbon film resistor with 500pF 500V Mica capacitor in parallel
R38 - Replace with 10k 1W carbon film resistor
C21 - Replace with 1n 1kV ceramic capacitor
R35 - Replace with 470k 1W carbon film resistor
R36 - Replace with 470k 1W metal film resistor
C22 - Replace with 500pF 500V Mica capacitor
C20 - Replace with 4.7n + 220k 1W carbon film resistor (cap toward R33-side)
R32 - Replace with 10k 1W carbon film resistor + 2k7 1W carbon film resistor in parallel (toward R33 node) to a 330nF 400V polypropylene capacitor with the 10k/330n leg going to the R32 pad toward the potentiometer
R30 Replace with a 470k 1W carbon film resistor
R24 - Replace with a 33k 1W carbon film resistor
C14 - Replace with a 220pF Mica 500V capacitor
Drill 3/8” hole to the left of the 4ohm speaker jack and add a 24mm Alpha 1M-B potentiometer to back of the amp (DEPTH)
Connect Pin 2 and Pin 3 of 1M-B pot
Add wire from 1M-B pot to Pin 3 to Output of 4 ohm jack
Add 10nF 630V polyester cap and connect between Pin 1 and Pin 2 of 1M-B pot
Connect red wire from “FB” on PCB to Pin 1 of pot
*** A Couple notes...I pulled the Service Manual schematic. Not sure who provided, but note C29 is showing .2uF, which is WAY too big. Can't see it in any of the shots Jason put, but is a blue cap. Should be at most .022uF (22nF).
Also, Jason communicated to jump R42, and C28 is a 250p "bright" cap. However, according to the schematic, C28 is in parallel with the 1M that was in R42, so if we jump R42, C28 is in parallel with C30 coupling cap going into Pin 3of VR9, but getting bypassed by the jumper, so not doing anything and not set up as a bright!
To do it right, remove C28 also and add the bright cap between Pin 3 (input) and Pin 2 (output) of VR9.
On the Depth Mod, if I'm running 8 ohms will I still connect to 4 ohm jack? Great tutorial btw!
Thanks. Yes, as connecting directly like this is independent of which jack you actually use for your cab.
M8 you have anything for the JCH20??? Ty
Not yet
@@HeadfirstAmps ok friend ty, I'm subd so I will know when and if you do, and have no problem throwing ya paypal $ for any help. I'm a tad late to the party I'm sure, been looking on line ect. Thanks M8...
any JCA20H mods?
Not yet, but I'm sure one of those will feature at some point!