The preamp in a friend's acoustic guitar doesn't seem to work. It's a B-Band T35, and I have tried fresh battery etc.
The tuner doesn't light up (I have tested plugging a cable in to make sure it doesn't need a cable in to operate), and no sound comes out through an amp.
I suspect it is just a matter of replacing the unit, but anything else to try before we do that?
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Acoustic guitar preamp not working...
Moderator: Spike
Acoustic guitar preamp not working...
It's a bugger getting inside the horn when you've got the array supports in place, isn't it!
- Mottlefeeder
- Junior Member
- Posts: 677
- Joined: Sun Sep 23, 2007 4:37 pm
- Location: Warrington
If you have access to a multimeter, you could check the resistance between the two battery contacts (with and without a guitar lead plugged in) An open circuit would indicate a faulty connection in that area, and no change when you plug a lead in might indicate a fault in the output jack socket.RichardH wrote:The preamp in a friend's acoustic guitar doesn't seem to work. It's a B-Band T35, and I have tried fresh battery etc.
The tuner doesn't light up (I have tested plugging a cable in to make sure it doesn't need a cable in to operate), and no sound comes out through an amp.
I suspect it is just a matter of replacing the unit, but anything else to try before we do that?
David
Yamaha RBX 765 5-string fretted
Ibanez EWB205WNE 5-string fretted acoustic
Ashdown MiBass550
Hartke HA4000
BFM Jack 10 - (2)
Homebrew 1x10
Homebrew Battery Amp
Ibanez EWB205WNE 5-string fretted acoustic
Ashdown MiBass550
Hartke HA4000
BFM Jack 10 - (2)
Homebrew 1x10
Homebrew Battery Amp
Hmmm - that was helpful David.
I have pulled the battery box/jack socket assembly.

With the multimeter I am getting a connection between B- from the battery box and the GND of the 4 pin connector (which goes off to the preamp etc).
I am not getting anything from B+ on the battery and B+ on the 4 pin connector, whether or not I have a jack plug in the socket (I am assuming that the battery is switched out when no lead is connected).
When the jack is disconnected we get
TAG1 > BATT-
TAG1 > B-
TAG2 > OUT
TAG3 > SW
BATT+ > NOTHING
When a jack socket is connected, I get signal thus:
TAG1 > BATT-
TAG1 > B-
TAG1 > SW
TAG1 > TAG3 (if mono jack inserted)
TAG1 > jack sleeve
TAG2 > OUT
TAG2 > jack tip
TAG3 > SW
TAG3 > TAG1
TAG3 > jack ring (if stereo jack inserted)
BATT+ > NOT CONNECTED
...so it would seem that the jack is not switching the +ve supply through to the 4 pin connector.
I have pulled the battery box/jack socket assembly.

With the multimeter I am getting a connection between B- from the battery box and the GND of the 4 pin connector (which goes off to the preamp etc).
I am not getting anything from B+ on the battery and B+ on the 4 pin connector, whether or not I have a jack plug in the socket (I am assuming that the battery is switched out when no lead is connected).
When the jack is disconnected we get
TAG1 > BATT-
TAG1 > B-
TAG2 > OUT
TAG3 > SW
BATT+ > NOTHING
When a jack socket is connected, I get signal thus:
TAG1 > BATT-
TAG1 > B-
TAG1 > SW
TAG1 > TAG3 (if mono jack inserted)
TAG1 > jack sleeve
TAG2 > OUT
TAG2 > jack tip
TAG3 > SW
TAG3 > TAG1
TAG3 > jack ring (if stereo jack inserted)
BATT+ > NOT CONNECTED
...so it would seem that the jack is not switching the +ve supply through to the 4 pin connector.
It's a bugger getting inside the horn when you've got the array supports in place, isn't it!
...I ran a lead round from the BATT+ to the B+ terminal on the 4 way connector, and it works! It seems that the tuner operates with the lead disconnected, but I think that is switched at the preamp end, so when tuner off the battery is disconnected.
Result! Thanks to David for encouraging me to have a tinker!
Result! Thanks to David for encouraging me to have a tinker!
It's a bugger getting inside the horn when you've got the array supports in place, isn't it!
- Mottlefeeder
- Junior Member
- Posts: 677
- Joined: Sun Sep 23, 2007 4:37 pm
- Location: Warrington
You're welcome. Glad you got it sorted.RichardH wrote:...I ran a lead round from the BATT+ to the B+ terminal on the 4 way connector, and it works! It seems that the tuner operates with the lead disconnected, but I think that is switched at the preamp end, so when tuner off the battery is disconnected.
Result! Thanks to David for encouraging me to have a tinker!
Yamaha RBX 765 5-string fretted
Ibanez EWB205WNE 5-string fretted acoustic
Ashdown MiBass550
Hartke HA4000
BFM Jack 10 - (2)
Homebrew 1x10
Homebrew Battery Amp
Ibanez EWB205WNE 5-string fretted acoustic
Ashdown MiBass550
Hartke HA4000
BFM Jack 10 - (2)
Homebrew 1x10
Homebrew Battery Amp
The normal way of switching active preamps of all types is to connect the battery negative to the ring and the preamp negative/ground supply to ground, so the negative side is switched and the positive side is a permanent connection - or, in this case, permanent disconnection.
Coitum volaticum non dono
Yes, that is what I realised in my tinkerings. Just wondering as the tuner operates without the lead plugged in, but I suspect that is intentional, and the battery is only being used when the tuner is switched on.
It's a bugger getting inside the horn when you've got the array supports in place, isn't it!