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basser
New
Username: basser

Post Number: 7
Registered: 10-2008
Posted on Wednesday, August 19, 2009 - 7:49 am:   Edit Post

Hello again to all Alembic lovers!

I've noticed that there are 3 trim pots (2 in blue and 1 in green) on the other side of my PF-6B preamp card where the hum balance and gain controls are. The trim pots are visible when the preamp cavity is opened, while the card is still attached to the plate. (Please find attached JPG file for your review.)

It would be much appreciated if you experts out there could kindly provide some information on what those trim pots are for and how to control it (or better not make adjustements).

Many thanks,

Andrew


PF-6B Preamp Card
jacko
Senior Member
Username: jacko

Post Number: 2379
Registered: 10-2002
Posted on Wednesday, August 19, 2009 - 7:57 am:   Edit Post

Hi Andrew.
I think you'll find that they're all blue. These are the trimpots used to control the 'amount' of signal coming from each pickup. There's an FAQ thread here.

Graeme
davehouck
Moderator
Username: davehouck

Post Number: 8601
Registered: 5-2002
Posted on Wednesday, August 19, 2009 - 8:13 am:   Edit Post

Graeme; on a PF-6, the trim pots you've referenced are on the the other side of the card and are available for adjustment through the holes in the cover plate. I don't think the trim pots pictured above are the same thing.
georgie_boy
Senior Member
Username: georgie_boy

Post Number: 913
Registered: 8-2005
Posted on Wednesday, August 19, 2009 - 8:28 am:   Edit Post

Looks decidedly odd to me!!??
mica
Moderator
Username: mica

Post Number: 6332
Registered: 6-2000
Posted on Wednesday, August 19, 2009 - 8:35 am:   Edit Post

NOOOOOOOOOOOO
Do NOT adjust these trimmers. These are part of the calibration for the high frequency noise cancellation network and are not user servicable. In fact, they are usually covered with strong stickers to discourage fiddling.
basser
New
Username: basser

Post Number: 8
Registered: 10-2008
Posted on Wednesday, August 19, 2009 - 8:55 am:   Edit Post

Mica and Dave,

Thank you very much for your prompt support and advice. I've been reading lots of other materials from you and it is sure helpful a lot.
And thanks to other members as well!

Should I cover the trimmers with stickers/tapes or would it be OK as current?

Andrew
mica
Moderator
Username: mica

Post Number: 6335
Registered: 6-2000
Posted on Wednesday, August 19, 2009 - 9:16 am:   Edit Post

Only need to cover them if you ask someone else to service your bass or if you sell it.
jazzyvee
Senior Member
Username: jazzyvee

Post Number: 1612
Registered: 6-2002
Posted on Wednesday, August 19, 2009 - 10:13 am:   Edit Post

Is that all the electronics for the Series bass or are there more hidden in the body somewhere else apart from the control cavity where the knobs are.?
Jazzyvee

(Message edited by jazzyvee on August 19, 2009)
mica
Moderator
Username: mica

Post Number: 6336
Registered: 6-2000
Posted on Wednesday, August 19, 2009 - 10:21 am:   Edit Post

There aren't any hidden electronics in a typical Series I or II bass or guitar. All electronics have access panels so repairs are possible.
jazzyvee
Senior Member
Username: jazzyvee

Post Number: 1613
Registered: 6-2002
Posted on Wednesday, August 19, 2009 - 10:36 am:   Edit Post

I'm just surprised you get all that sound from apparently so few components.

I plan to give you a call in a bit Mica once I finish my dinner.

Jazzyvee
basser
New
Username: basser

Post Number: 9
Registered: 10-2008
Posted on Wednesday, August 19, 2009 - 3:13 pm:   Edit Post

Dear Mica,

Thank you again for the clarification.

It's always great to know that your ultimate builder is there for you!

Andrew
jacko
Senior Member
Username: jacko

Post Number: 2380
Registered: 10-2002
Posted on Thursday, August 20, 2009 - 12:54 am:   Edit Post

Oh dear. I'm hanging my head in shame now. Just as well Dave and Mica were on the ball or my mistake could have caused untold suffering ;-(

Graeme

p.s. They still all look blue to me ;-)
georgie_boy
Senior Member
Username: georgie_boy

Post Number: 915
Registered: 8-2005
Posted on Thursday, August 20, 2009 - 4:19 am:   Edit Post

I'd never seen the circuit board with the calibration fitted either!
Now we all know what to look for.

G
davehouck
Moderator
Username: davehouck

Post Number: 8604
Registered: 5-2002
Posted on Thursday, August 20, 2009 - 7:35 am:   Edit Post

That's ok Graeme; let me get you a beer.
jacko
Senior Member
Username: jacko

Post Number: 2385
Registered: 10-2002
Posted on Thursday, August 20, 2009 - 7:51 am:   Edit Post

One of these days I'll be in a position to take you up on that Dave ;-)

graeme
terryc
Senior Member
Username: terryc

Post Number: 1009
Registered: 11-2004
Posted on Friday, August 21, 2009 - 3:43 am:   Edit Post

Maybe they should colour them yellow as they do on the only parts you should touch inside the engine compartment of a car ie screen washer fluid, oil, radiator etc.

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