Boss HF-2 question - fault?

Kalimna

Greetings folks,
Ive just received a Boss HF2 flanger from an ebay purchase. It's one of the earlier made in Japan pedals.
Doing a quick check (using a battery), i am loving the sound but the Res (?resonance/feedback) control pot is a bit crackly and i get the flanging whooshing sound without any plucking of guitar strings. I.e - pedal on (controls at top middle), guitar plugged in and run into a Blackstar TVP. If the res control is turned much past top middle, i get the whooshing without a guitar signal.

Does this sound normal for this pedal (crackling aside)?
Is replacing the crackly pot likely to improve things?
Anything else that might be wrong?

Cheers in advance,
Adam

Johnnyseven

I would have thought if the pedal is on you would get some kind of flanging noise whether your guitar is plugged in or not, so I think this is normal. If you're getting some flange when in bypass though I would say there is an issue.

JezWynd

With the Resonance turned up you'll hear some whoosh. The pedal sounds best when the Resonance is kept in check anyway, so it's not an issue.

Try some contact cleaner on the crackly pot, may be an easy fix.

Kalimna

Thanks for the replies - to be clear, the pedal doesnt produce any sound at all when in bypass, there is an appropriate (and quite nice) flanging sound throughout the rotation of the first three knobs. It is just when the 'res' control is turned past 12 o'clock, the pot is crackly, the guitar signal almost disappears to be replaced with an oscillating whiney sound.
I had a look inside and dont see any obvious signs of blown components (to my very rookie eyes), but the split shaft of the res pot has snapped one part of the split off. So maybe there has been some damage to it.

If contact cleaner doesnt fix the issue - do you happen to know where I could locate some of the small Boss pedal pots? Specifically a reverse log 50k? (from a schematic I found online).

Many thanks,
Adam

lasermonkey

It might be worth re-soldering the res pot, if it may have taken a knock. Otherwise, it's possible that the internal resonance trimpot is either out of calibration or faulty.

JezWynd

Kalimna said:

 It is just when the 'res' control is turned past 12 o'clock, the pot is crackly, the guitar signal almost disappears to be replaced with an oscillating whiney sound.

No it definitely shouldn't do that. The resonance sound can be heard even when guitar is not being played but not to that extent. iirc the sound gets quite 'brittle' if the resonance is cranked up but it shouldn't replace the guitar. As @lasermonkey suggests, it could be a trimpot has been misadjusted.

Kalimna

Ok. Thanks for the further input.

Mr Monkey, when i had a peek inside, i noticed 3 trimpots including the one labelled 'res'. If i was to adjust this, is there anything i should be aiming for? Or is it a case of adjust, see if it works, adjust some more, repeat?
Your help is much appreciated,

Adam

ICBM

I think the Res one is safe to adjust - it's intended to set the resonance just below the point of self-oscillation when the control is turned up full. Don't fiddle with the other ones.

It sounds like the pot is damaged though - if it makes a poor contact it will probably cause the resonance to go to above full, which is why it whines. Adjusting the trimmer probably won't fix that. Try cleaning the pot first, and replace it if that doesn't work - although that make be easier said than done, those little specialist pots are hard to get...

Johnnyseven

Contact Boss direct, you can get spares from them.

Kalimna

Thanks ICBM and Johnny7. I'll contact Boss and see if they can help. I know the HF2 is a while out of production, but the pot itself doesnt sound too unusual.

Cheers,
Adam

ICBM

Kalimna said:

I know the HF2 is a while out of production, but the pot itself doesnt sound too unusual.

You wouldn't think so, but it can be remarkably hard to get the exact combination of value, taper (especially if it's reverse Log), body size, shaft type and PCB footprint that you need for things like this… if Boss have them you're OK though.

Kalimna

Actually, I had meant that it was probably something Boss would have even if the pedal is out of production. But I do take your point.

As it happens, the pots are not PCB mounted - they are wired in. So if Im unable to locate another direct replacement I can always make do with another internal trim pot. I am after a working pedal more than something cosmetically perfect.

Cheers,

Adam

Kalimna

A very brief follow up to my Boss flanger.
It seems, as ICBM alluded to, that nowhere in the universe stocks the 9mm C50K pot needed. So, following a squirt of contact cleaner the crackling went a little, I decided to have a go at removing the metal case from the pot and giving it a direct clean on the taper. Hey presto, smoother rotation and no crackling.
No improvement on the self-oscillation, though. So, with the backplate off, a fresh battery in and pedal plugged into my trusty Blackstar TVP15 (not, it would seem, a great pedal platform), I had at the res trim pot. Voila, gentle flagging with no crackle or oscillation.

Thanks chaps,

Adam

Jalapeno

HF-2 is the Hi-Band Flanger - it'll be a bit wooshy, mine is - turn it of when not needed