# JHS Mini Bomb Boost Issues, need help



## vadsy (Dec 2, 2010)

A friend gave me a cute little boost pedal that was acting up. The problem seems to be that once the pedal is engaged the signal goes nearly dead until you turn clockwise and reach the top 90-95% of the sweep, after that the signal comes back but with little or no boost. It's a little hard to tell if it does anything at all except cut the high end a bit, just seems to pass the signal through but only when pretty much fully open. I thought a bad pot so after a quick spray of contact cleaner didn't do anything I disconnected and metered it. Seems fine on the meter, smooth upswing all the way up to 950-960K. New pot didn't fix the issue either.
What could it be?


----------



## Cups (Jan 5, 2010)

Check to see if all connections to the pot are good. You measured the resistance of the pot while rotating the pot? Both ways?


----------



## vadsy (Dec 2, 2010)

Connections were good. Measured both ways and between different terminals.
Weird thing is that a brand new pot does the same thing.


----------



## Cups (Jan 5, 2010)

Is it a SHO boost replica? Does it crackle when rotated?


----------



## vadsy (Dec 2, 2010)

I'm not sure if it's a replica but given JHS reputation, I wouldn't be surprised.
No crackles.


----------



## mhammer (Nov 30, 2007)

Purportedly uses a JFET so I'm thinking more in the zone of the Stratoblaster.

One possibility is that the stompswitch is slightly buggered up and doesn't conduct the output until its high. So, does bypass provide exactly what you expect? When in boost mode, do you get appropriate continuity between the switch lugs? I'm not saying it IS the switch. But you can drive yourself nuts checking every other aspect of the circuit/pedal _except_ the switch, so it's helpful to be able to say "Nope, it's not that".

There is a small blob of grease inserted into the switch during assembly. It not only holds parts in place during assembly, but also damps "switch chatter" and bouncing, once assembled. Sometimes, during installation, the switch lugs are overheated, the grease liquefies, and flows along the contacts, acting as an insulator. In some instances, that can appear to make the switch entirely non-functional. While in other instances, it simply acts as a sort of high-resistance path. As always, this:


----------



## vadsy (Dec 2, 2010)

I actually thought about the switch as it is the only other moving part in the pedal, you know what moving parts eventually do...
Everything works fine in bypass and the switch 'feels' fine and meters fine but it might be worth a venture to isolate and eliminate that possibility as well.
I'll give it a shot tomorrow.


----------



## mhammer (Nov 30, 2007)

This can sound farfetched, but keep in mind that the little rocker contacts inside are always touching the "common", but either touching the "bypass" lugs or the "engaged" lugs. Depending on what is in contact with what when excess heat is applied, it is not unreasonable that the grease could have flowed so as to have NO effect on quality of bypass contact, but imposed a high-resistance barrier to continuity in the effect setting.

As always, I'm not saying that's what it necessarily is, but it is within the realm of possibilities and should at least be checked off the list.


----------



## vadsy (Dec 2, 2010)

I follow you and agree that it needs to be checked and eliminated from the list of possible issues.


----------

