Alembic Guitars Club
Alembic products => Owning an Alembic => Troubleshooting => Topic started by: Clarky on August 20, 2018, 05:48:19 AM
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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.
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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
(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=230.0)
http://club.alembic.com/index.php?topic=2122 (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.
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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?
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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.
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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?
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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 (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 (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
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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 (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.
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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 (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. ;)
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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 (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 (http://club.alembic.com/index.php?topic=270.0)
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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!
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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.
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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.
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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.
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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.
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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!
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Make sure your power supply is in the mono switch position or you are using the bass/mono output. What you are describing is what happens when your bass is coming out stereo but you are using a mono output. The knob placement on the switch should have no impact.
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Sorry Mica, thanks for clarifying about the pickup selector but I am confused. Apologies if I am saying something totally rookie here, but there is no switch on my DS5. The front panel has two 1/4 outputs (Bass/Mono and Treble) as well as the 5 pin input. So how do I select the power supply for mono switch position?
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Use the bass/mono output on the DS-5 if you want the mono output. There are indeed a few versions.
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Apologies but that is what I was doing (using bass/mono output; and separately trying the treble output). Am I creating a stereo/mono mismatch in so doing? If so how can I work around this please?
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Clarky I have one of those un switched PSU boxes that I use with my 1980 S1 and I get both pickups out of the mono and get individual outs if I use a jack in both sockets. Like yours my old S1 still has the stereo jack. One of the members here George Price (geepee) lives somewhere in London so it might be worth contacting him to see if you could meet up to try your bass through his DS-5 just to see if there is problem with your PSU or your bass. Failing that I'm in London on a seminar next week either Thursday and Friday or Friday only so I could bring my switched one for you to try depending on what time we both have free during the evening before my train back. I also have a PJB headphone amp that I could bring if that would help.
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Thank you for the kind offer JV, although I will be away when you are down in London. I think I need to try out the stereo to mono lead which I have on order (hopefully I will get it by the weekend or early next week at latest, before I head off). Then I can work out whats going on (I think!)
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If you use both outputs you simply get one pickup per output - you will of course need to use 2 amplifiers.
If you want to use a mono amplifier, just use the bass/mono out out on its own. It sounds like you have the operation under control.
You can test the 1/4" output wiring by plugging stereo headphones directly into it. You should hear one pickup in each ear. If you can do this test, please post back with your results.
For the 5-pin output, you will need to test with another unit as Vince describes, or take it to a service person to test. I can send you a schematic if you need it. I suppose we need to confirm that the 1/4" output is working properly, and then figure if the 5-pin cable or the DS-5 is preventing one pickup from getting to your amplifier.
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Ok, the stereo to mono cable arrived and - as I feared based on the 'headphone test' - the situation is the same. Neck pickup sounds great and can be selected from positions 3 and 4 of the selector switch. Bridge pickup is totally silent so position 2 of the selector switch produces no sound whatsoever. At least this isolates the issue to the bass, not the DS5. However, I do not know where to go next? If it helps I have taken pictures of the electronics which I will attach in my next post.
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Pics
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"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."
Sounds like either the selector switch or you have a dead pickup.
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Hi gtrguy, thanks for your reply. Unfortunately I have no electronic understanding at all so talk of the PF6 card and switching things around terrifies me! I would likely damage the instrument due to my lack of understanding.
Guess I am going to have to take this to a technician (hope there is one in London who knows how to work on Alembic electrics ...) if there is no simple fix
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Reverse where the red and blue labelled pickups are plugged into the card. Then report if the position of the functioning pickup changes, stays the same, or if everything is dead. You can plug them back in regular when you've completed the test. This will let us know if the preamps card or one of the pickups is the culprit.
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Hi Mica, I just did what you suggested and swapped the red and blue inputs on the back of the card (not as hard as I had imagined, gtrguy, sorry!) - the result is that the functioning pickup remains the neck pickup, no change at all.
What does this mean? Thanks
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It means the problem is with the bridge pickup, not with the card.
Bill, tgo
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It means the problem is with the bridge pickup, not with the card.
Ok thanks. So what are my options here? New pickup or get wiring/electronics checked out by a technician?
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Sure sounding like you need a new bridge pickup. Switching where the pickups are plugged in on the card confirmed that the problem isn't the card/electonics. If it were my bass I would be happy that the problem is one pickup not something with the electronics themselves. Suggest you give Mica a call between the hours of 11 AM and 4 PM PST to order a pickup. Remember to ask if you can get one with the older style pickup cover (minus the gold logo) so the new pickup matches the old one cosmetically.
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Thanks for the advice Stephen.
Have to say that this whole saga has rather deflated the excitement at buying my dream bass. Just hope I can get it working in the near future without too much additional cost 😐
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It's a cool bass! Getting it up and running will make you fall in love with it and it probably just needs a new pickup.!
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Before buying a new pickup, you might want to check the external hookup wires on the old one. You most likely have a broken wire, either inside the pickup, or one of the external hookup wires. If the break is internal, the pickup is dead and you will need a new one. If the break is along one of the external wires, it is a relatively easy to fix and a lot less expensive. Any decent luthier or electronics tech should be able to quickly diagnose the problem if you don't feel confident you can do it. And don't be too bummed, it will all seem worth it once you get the bass up and running.
Bill, tgo
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I removed the bridge pickup and the green wire that connects it to the preamp/electronics seems to be intact. In which case its looking highly likely that its a dead pickup. I have dropped Mica an email to find out what a replacement would cost.
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A quick check with a VOM meter will tell you if the pickup is good.
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Thanks gtrguy. I am not able to get to technician for a couple of weeks so will follow up as and when. Meanwhile Mica has been in touch with me about obtaining a replacement pickup set - should the technician confirm its the pickup at fault.
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Update: the guitar technicians say the pickup is not dead, which is good news. They think they have localised the issue to a chip on the board which they are ordering in from Europe, so will take a few days to arrive. Fingers crossed, this will solve the problem and at considerably lower cost than pickup replacement(s).
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After several false starts (and 2 months ...) the chip arrived from Europe and the technicians installed it on the board. The good new is the bridge pickup works again! There is a but, though, as there is some hiss which gets more audible as you turn the filter control clockwise. However, it can be controlled by keeping the volume on the pickup off max, not using 'full' filter position and using the amp volume instead. I have been without the bass for so long I am not inclined to take it back for further tinkering so will see how I get on.
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Update: I tweaked the trim controls and the hiss is virtually inaudible now ;D
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Update: I tweaked the trim controls and the hiss is virtually inaudible now ;D
Great news! Gain structure is so important.