Author Topic: Pickup Response (thread moved from AB&G section) (Read 759 times)

ttc · « **on:** August 07, 2009, 04:52:02 PM »

I have recently bought a 1978 Series I on which the bridge pickup is much, much softer than the neck pickup.

That is, if both pickup volumes are set to max, and I switch the selector from standby to bridge pickup, it is very soft. If I continue to both pickups, the volume jumps enormously. If I continue to neck pickup it is only slightly less loud.

I have adjusted both sensitivity screws at the back panel to full response, but this has no effect on the difference I am describing.

Is anyone aware of why this might be?

Many thanks for your help.

Best regards,

TTC

keith_h · « **Reply #1 on:** August 07, 2009, 05:04:20 PM »

It's normal in mono mode. When both pickups are selected the preamps for each pickup are additive.

Keith

David Houck · « **Reply #2 on:** August 09, 2009, 06:27:38 AM »

The difference in perceived loudness between the neck pickup and bridge pickup, if trim pots, volume controls, filters and Qs are all set the same, may be a difference in pickup height. If the bridge pickup is close to the strings and the neck pickup is much lower, a common setup, then the bridge pickup will be louder. You can compensate by adjusting the trim pots to get the balance where you want.

tmoney61092 · « **Reply #3 on:** August 09, 2009, 11:39:49 AM »

try keeping the bridge trim pot all the way , and make the neck trim pot less, that should help equal out the volumes, best of luck to you

~Taylor Watterson

David Houck · « **Reply #4 on:** August 09, 2009, 12:05:32 PM »

Thanks Taylor, I read it backwards.

TTC; to follow up on Keith's comment, are you using the quarter inch jack or the five pin jack?

ttc · « **Reply #5 on:** August 10, 2009, 06:56:11 AM »

Many thanks for these helpful posts.

Dave, I am using the 5-pin through the blue box into a small practice amp.

Regards,

TTC

David Houck · « **Reply #6 on:** August 10, 2009, 08:11:50 AM »

When the selector is set to both, turn the neck volume all the way down and the bridge all the way up. Now do the opposite. Is the difference between the neck pickup output and the bridge pickup output the same as when selecting the pickups individually with the selector switch?

ttc · « **Reply #7 on:** August 15, 2009, 10:07:40 AM »

Dave,

Sorry to take so long to respond. I tried your tip and the selector switch seems to make no difference to the response. I.e.: bridge pickup selected response equals response when both pickups are selected but neck pickup volume is off, and the reverse.

Can I conclude that the trouble is in the bridge pickup wiring?

TTC

David Houck · « **Reply #8 on:** August 15, 2009, 12:01:23 PM »

Here's the next test. Go here and here and determine which pickup connectors you have. If you have the coax connectors, follow the instructions for disconnecting the pickup lead from the pc card. If you have the two-pin connectors, grasp the housing and not the wire to gently pull the connector from the pc card. The test here is to switch the bridge and neck pickup leads (leave the hum canceling pickup lead where it is). With the pickup leads switched, has the problem moved from the bridge pickup to the neck pickup, or is the bridge pickup still weak?

slawie · « **Reply #9 on:** August 15, 2009, 08:21:01 PM »

Is the distance from the pickup face to the string the same for both pickups?

It does matter. Keep the distance the same.

slawie

ttc · « **Reply #10 on:** August 17, 2009, 07:33:32 AM »

Slawie--the bridge pickup (very faint) is closer to the strings than the neck pickup (much louder).

Dave--many thanks for your help; I will let you know the results.

Thanks to all,

TTC

ttc · « **Reply #11 on:** August 17, 2009, 05:46:08 PM »

Dave,

I changed the connectors as you recommended, and the problem was reversed: the neck pickup was very faint and the bridge pickup responded well. (The bass has the coaxial connectors, by the way.)

Many thanks,

TTC

David Houck · « **Reply #12 on:** August 17, 2009, 06:26:50 PM »

Let's check the jack. Carefully put the pickup leads back to where they originally were. Unplug the five pin cable from the bass. Checking first to make sure you have fresh batteries installed, plug a set of headphones into the quarter inch jack. (This test assumes the quarter inch jack is stereo and hasn't been modified to be mono.) If everything is working correctly, you should hear the neck pickup in one ear and the bridge pickup in the other. Is the problem still the same?

ttc · « **Reply #13 on:** August 18, 2009, 07:38:24 PM »

Dave,

I replaced the leads, put new batteries in, and plugged some headphones into the quarter-inch jack.

The signal through the headphones was exceedingly faint. The neck pickup signal came in soft but unmistakable through the left ear, but there was no response from the bridge pickup through the right ear. I rechecked this several times, by isolating the bridge pickup using first the selector switch and then by using the volume knobs.

As an aside, I was surprised at how faint the headphone signal was, even with new batteries and for the (working) neck pickup. Could this be another problem as well?

Many thanks for all your help.

TTC

(Message edited by ttc on August 18, 2009)

David Houck · « **Reply #14 on:** August 18, 2009, 08:23:01 PM »

Teige; we're making progress, but this is about as far as I can be of much help. Hopefully, Mica or one of the more electronics-savvy members will notice this thread and step in (which is why I moved the thread here where it's more likely to draw that kind of attention).

If you have a multimeter, it seems to me that the next step would be to test the signal coming from the PF-6 card to the controls (the ribbon cable splits with the neck signal going one place and the bridge signal going another). If the signals are the same, then the PF-6 card is fine, if they are not the same, then the problem is in the PF-6 card. However, I don't know enough to tell you how to do that test. If the PF-6 card tests fine, then you would continue testing the circuit on each side until you find the point where they differ. But again, that's beyond my skill level. My guess is that Mica or one of the others will be better able to quickly zero in on the problem or suggest the next action to take.