Pickup/selector and PSU issues with my newly acquired '79 Series 1

[Clarky]

Well my '79 Series 1 arrived and its in beautiful condition. Only thing is the bridge pickup does not appear to have any output. The pickup selector seems to have two (not one) standby positions and in the two 'on' positions it just selects the neck pickup so that when I turn down volume on the neck pickup there is no sound at all. Its the same whether I use external power supply unit (but see below) or batteries. Perhaps its the pickup selector switch which is at fault rather than the bridge pickup or electronics? Has anyone ever encountered this and do you have any advice here?  PS I have emailed the seller but not heard back yet.

Separately the external PSU worked fine at first although again I could only hear the neck pickup. After a while though it started screeching and was also quite hot. Now it has a US plug and I had to use a UK mains adaptor so maybe this is the reason (I am an electronics numpty). Anyhow I unplugged it and then - a few minutes later - reattached it. Result: no sound at all from the bass (but I continue to get sound if I use normal jack and batteries, albeit just the neck pickup still). Again, any advice would be gratefully received here thanks.

Has somewhat tarnished my first day with what is an exceptionally beautiful bass.

[keith_h]

For that era bass the 1/4 inch jack is wired in stereo so you will only hear one pickup if you use a mono cable. There is information on rewiring the bass or making cables in the Series I/II FAQ section. To test both sides you can use a TRS to TR Y-cable.

http://club.alembic.com/index.php?board=23.0
 
The power supply is for 110/120 volt systems. The older ones do not have a voltage selection switch and can only be changed by rewiring the transformer taps. When you say adapter does it step down the voltage or just adapt the plug? If it is the later I'm afraid you have damaged the power supply. If the bass is still working with batteries you probably didn't damage anything there with the over voltage. Here is a link to the DS-5 transformer voltage selection drawing. There is also a link to the original thread that has a picture of the transformer. At this point I would not plug the bass into the power supply until I could take voltage measurements and verify its functioning correctly.

http://club.alembic.com/index.php?topic=230.0
http://club.alembic.com/index.php?topic=2122

So try out the bass on batteries with the Y-cable and let us know the results.

[Clarky]

Thank you for your detailed reply. Regarding the PSU I did simply use a plug adaptor and so it appears I have indeed damaged it 😐 Is the unit now completely dead or is it repairable?

Regarding the stereo jack input, thank you for this information. Can I ask if such thing as a stereo-enabled cable/lead exists so I could simply plug this into my bass to receive both pickup signals?

[keith_h]

Yes it is repairable. e-mail me at the address in my profile and I can send you a schematic. A local tech should be able to handle the rest from there.

[Clarky]

Thanks Keith I have emailed you.

Is it possible a lead can be wired for stereo at the 1/4 jack input of the bass and simply plug into the single input of an amp? If so, can such a lead be bought commercially or does it have to be custom made by an electronics whizzkid?

[JimmyJ]

Mark,

Sorry you've run into issues right away.  The seller should have made it clear about the PSU, that is a drag.  Do not plug it in again without an old-school step-down mains transformer with 120V output.  You can still find those around and you don't need a large one as the instrument doesn't draw very much current.

Regarding the stereo 1/4" jack; if you have put in fresh batteries you could do a quick test by plugging in a pair of headphones to see if the bridge p/u is passing audio.  Now most headphones are not the proper load on the output circuit so the sound may not be clean or respond correctly to the volume controls, but just as a test you should be able to hear something in both ears as you switch the p/u selector.

Assuming you DO hear audio, then then there are 3 ways to proceed: 

Version 1 is to find (or have made) a stereo Y-cable.  Stereo 1/4 plug on the bass end splitting into two mono 1/4" plugs on the output end. One of the mono outputs will be the neck p/u and the other the bridge p/u.  I don't know where in London you might find this but here's a slightly funky one on Amazon.co.uk as an example:
https://www.amazon.co.uk/kenable-6-35mm-Stereo-Jacks-Cable-Black/dp/B003OSX8ZO/ref=sr_1_3?ie=UTF8&qid=1534779396&sr=8-3&keywords=stereo+y+cable+1%2F4%22

Version 2 is to have a stereo-mono "summing" cable made.  This involves putting a couple small summing resistors into the stereo plug (you can't just join the two outputs directly together).  If you have a pal who solders this isn't a bad option - but it limits you to using this ONE cable so don't lose it!

Version 3 is to have your soldering friend help you modify the bass internally.  (I've done this to mine just for the convenience of being able to use a standard guitar lead into any amp...)  The info on this is here: http://club.alembic.com/index.php?topic=270.0

Let us know about any further results.  In the meantime play that bass acoustically to get the feel of it.  It looks like you got yourself a great axe!

Jimmy J

[StephenR]

Sweet looking bass!

You can get a stereo to mono cable similar to the one at the link below. The company is in the USA but it shouldn't be that hard for you to find someone in the UK that makes custom cables.
https://tinyurl.com/ybtjk6wm

You may be best off if you just have the 1/4" jack re-wired for mono output unless of course you plan on running the bass in stereo using the batteries and 1/4" jack. If you wire the 1/4" jack for mono you will still be able to get stereo output via the external power supply. The one thing you should be aware of when using batteries is that they are not going to last very long. I always use the power supply but others in the club have mentioned only getting 20-25 hours out of each set of batteries in a Series bass. You don't want the batteries to go on a gig, the sound goes from normal to ragged to dead very quickly with no warning.

[keith_h]

I've sent the schematic. Here is a link to a discussion about the transformer voltage conversion for a German customer. About halfway down is an update by rjw. That is Ron Wickersham the guy that designed all this. Its sandwiched by a couple of posts by JimmyJ. 

http://club.alembic.com/index.php?topic=22433.msg226283#msg226283
I see Jimmy beat me to the Y-cable. He also mentions using headphones. I always forget about that method guess that's why he's here to keep the rest of us honest. 

[keith_h]

Thanks Keith I have emailed you.

Is it possible a lead can be wired for stereo at the 1/4 jack input of the bass and simply plug into the single input of an amp? If so, can such a lead be bought commercially or does it have to be custom made by an electronics whizzkid?

The conversion from stereo to mono output on the 1/4 inch jack whether done in the bass or via the cable requires the installation of summing resistors.
In the Series I/II FAQ section Mica has posted how to wire a cable from the stereo 1/4 inch TRS plug to mono 1/4 TR plug.

http://club.alembic.com/index.php?topic=275.0
For the connector the FAQ section also has instructions here.

http://club.alembic.com/index.php?topic=270.0

[Clarky]

JimmyJ, Stephen and Keith. Thank you so much for all your advice.

 I will check the bass output on bridge p/u with headphones later today. In the mean time I have found a local amp technician who can fix the DS5 with the help of Keith's schematic.  I may also buy a Bayou Alembic summing stereo to mono cable as a backup (I do like the idea of rewiring to take all guitar leads but on the other hand I am reluctant to modify a beautiful piece of history!)

You have all been so helpful. Thanks!

[gtrguy]

Uh, did you switch the pickup jacks around on the PF6 card to check if the pickup that doesn't work will work when it is switched? Don't plug it into the dummy PU spot.

[Clarky]

I appreciate the input gtrguy but (as I have unfortunately established) I am a numpty with electronics and I am not confident of doing more damage if I start playing with the internal controls.

[Clarky]

Update: the DS5 power supply unit is back from the amp technicians and converted to UK/EU voltage

The good news: I can now get sound from my Series 1

The not so good:

- whether I take the lead from the Bass/mono or Treble output of the DS5 to my amp, the first two (nearest to me) positions of the pickup selector switch are completely silent (not just the first).
- Furthermore any sound from the bass in the other two pickup selector positions is totally silenced if I wind down the volume on the neck pickup. The controls for the bridge pickup appear to do absolutely nothing.

So, unless I am getting this completely wrong, it appears I only have a functioning neck pickup?

I have stereo to mono lead on order but it won't arrive for several days (thanks to UK customs) so I cannot double check that way.

[StephenR]

One thing I notice when looking at the picture in your first post is that there may be something wonky with your pickup selector. Can't tell from the picture what position it is in but on my 78 Series bass in standby position (both pups off) the point on the switch points down toward the floor (6 o'clock). When only the front pickup is selected the point on my switch is at 11 o'clock. In the picture yours is at 12 o'clock. I suspect there is something up with your pickup selector switch, not the pickups themselves or the electronics. Your switch could be rotated just slightly or it could be flipped upside down but I don't think it is normal for it to point straight up like that. Have you checked the wiring to the switch itself?

I can't remember if you posted a picture of the electronics cavity in one of your threads about the bass, if not, a picture may provide some clues. A picture of the wiring for the switch would be helpful, too.

[Clarky]

Thanks. The previous owner changed the direction of the pickup selector switch as he said he caught his hands on it when slapping. However he also assured me that the electronics were in full working order when he packed the bass up for delivery to me. I will see what happens if I re-angle the selector switch. Appreciate your advice!