Preamp on my APX-4A

APX series guitars are designed with a focus on playability. Their thin bodies and cutaways that provide greater access to the upper frets, offer smoother switching between electric and acoustic instruments.

Moderators: parametric, Derek, Buzzard, Saul

User avatar
Pegotico
Posts: 7
Joined: Sat Oct 15, 2016 1:38 am

Preamp on my APX-4A

Unread post by Pegotico » Sat Oct 15, 2016 8:30 pm

Hi everybody!

I have a problem with my preamp which stopped working after connecting it to a friend's amp. It doesnt turn on so I'm assuming the problem is the preamp.

I have a friend who can fix it if there is a way of getting the schematics for the preamp. I checked with Yamaha and they don't have the part available anymore. Can I get the schematic?

Also which preamp would be a good solution for my guitar? Im assuming I would have to also buy the pickup? I don't want something expensive and would hope to find something around the same size as the original to avoid modding the guitar if possible.

thanks in advance!

Peg

User avatar
Buzzard
Specialist Moderator
Specialist Moderator
Posts: 1665
Joined: Wed Sep 04, 2013 7:38 pm
Contact:
Denmark

Re: Preamp on my APX-4A

Unread post by Buzzard » Mon Oct 17, 2016 9:41 am

Hi Pegotico, Welcome to the Yamaha Forums. :D

Your preamp should turn on when a (mono) plug is inserted into the guitar output jack.

If nothing happens, make sure that the battery terminals are clean and adjusted to ensure connectivity.
:idea: Battery connection is often the reason for malfunction. :idea:

I only have workshop manual for the following preamps: System 20 , System 20s and System 21 (from Yamaha APX-5 and up)

Yamaha usually can and will deliver the schematics for vintage equipment.

Best Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: http://www.yamahamusicians.com/forum/vi ... =24&t=7004 :idea:

User avatar
Pegotico
Posts: 7
Joined: Sat Oct 15, 2016 1:38 am

Re: Preamp on my APX-4A

Unread post by Pegotico » Tue Oct 18, 2016 5:42 am

Hi Peter

Thanks for the reply!! I will contact Yamaha and see if can get my hands on the schematics.

Do you have any recommendations(plan b) in case plan A fails? as to which preamp would be a good replacement.

User avatar
Buzzard
Specialist Moderator
Specialist Moderator
Posts: 1665
Joined: Wed Sep 04, 2013 7:38 pm
Contact:
Denmark

Re: Preamp on my APX-4A

Unread post by Buzzard » Tue Oct 18, 2016 3:46 pm

Plan A : Make sure the battery connects properly.

Plan B : Get wiring diagram (form Yamaha).

Plan C : find another preamp to substitute the old one. Fishman makes some good but expensive ones.

In any case, have your friend check that the battery connections are in perfect shape, before going any further.

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: http://www.yamahamusicians.com/forum/vi ... =24&t=7004 :idea:

User avatar
Pegotico
Posts: 7
Joined: Sat Oct 15, 2016 1:38 am

Re: Preamp on my APX-4A

Unread post by Pegotico » Tue Nov 08, 2016 5:25 am

Hi Peter

Last week I went ahead and call Yamaha and they sent me the wiring diagram. So if anyone needs it let me know.

Ive been so busy lately as I'm going on vacation soon... I took out the guitar jack and amp out. For some reason the cables on jack broke and had to solder cables on jack again. Note that guitar jack is not in good condition. Im a little confuse here, but lets move on. I tested with soldered guitar jack and battery connected to pre amp and it didn't work. I think I may have solder cables incorrectly. I connected it based on post number eight

viewtopic.php?f=93&t=8168

If this is the correct way white= ring and red=tip then jack is messed up..


(I haven't call my friend as I was just going to ask him for help if there was something wrong with the pre amp. He has little to no time because of his job so I prefer to ask him for stuff I can't solve.)

TEST 2

I connected the battery directly to the pre-amp and use another guitar jack (With this jack, I would have to make a larger hole which I would prefer not to) and everything is working!!! Im so happy that there was sound coming from the amplifier.

SO I think I have 2 issues. One is the battery holder (probably cleaning it not sure if this would help) and the other the guitar jack. I don't want to make holes, so I need some help on buying a new one.

Second question.. Based on what I've read when using an active preamp, it has to be a stereo jack. Is this assumption correct?

Mono: Used in most acoustic and electric guitars with passive pickups.
Stereo: Used in acoustic and electric guitars with stereo outputs or active electronics.
TRS (tip-ring-sleeve): Used with active electronics, active pickup systems, or acoustic-electric guitars with two independent sound sources (such as an under-saddle transducer and onboard mic).
Power: This is usually a stereo or TRS jack attached to a preamp.

I think I would get the switchcraft stereo guitar jack.

http://www.switchcraft.com/Category_Mul ... Parent=952

This is the one or at least similar style jack the guitar has

http://www.switchcraft.com/productsumma ... ?Parent=72

There are several options (double open circuit and double close circuit). I would assume the correct one is double open circuit. Is this correct?


Last do you have any recommendations on guitar jacks? Are this better? If yes, which one will work?

http://www.neutrik.com/en/audio/plugs-a ... cal-jacks/

sorry for the long post! :)

User avatar
Buzzard
Specialist Moderator
Specialist Moderator
Posts: 1665
Joined: Wed Sep 04, 2013 7:38 pm
Contact:
Denmark

Re: Preamp on my APX-4A

Unread post by Buzzard » Tue Nov 08, 2016 8:27 pm

Looks like you have the problem(s) sorted, well, at least almost. :wink:

You actually had it working with the battery connected directly, and the plug replaced.

at this link: viewtopic.php?f=93&t=8168&p=43772#p43772 showing the color codes on MY AEX-500N, tip is red , ring is white , and sleeve is Black.

Clean up your battery holder and ALL its connections, and if your original plug is broken, replace it.
(try getting one that doesn't require any modifications of your guitar body)

Neutric plugs are high quality, but, basically ANY stereo plug should do the trick.
If you want Neutric, this one can be used: http://www.neutrik.com/en/audio/plugs-a ... ks/nj3fd-v

The ORIGINAL plug should be available from Yamaha.

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: http://www.yamahamusicians.com/forum/vi ... =24&t=7004 :idea:

User avatar
Pegotico
Posts: 7
Joined: Sat Oct 15, 2016 1:38 am

Re: Preamp on my APX-4A

Unread post by Pegotico » Wed Nov 09, 2016 1:43 pm

Buzzard wrote:
The ORIGINAL plug should be available from Yamaha.

Regards
Peter
They dont. :(

At least US site.

Only parts they have available for my guitar is the TRUSS ROD, STRAP BUTTON, TUNING MACHINE and NUT.

So I bought the switchcraft 12B (got it fast because didn't have to order it online) and hole in my guitar is slightly smaller, it wont go in... This is a surprise as I thought this was standard.

I also tried to google original part which is QC195400 with no luck.
Attachments
20161109_083732.jpg

User avatar
Buzzard
Specialist Moderator
Specialist Moderator
Posts: 1665
Joined: Wed Sep 04, 2013 7:38 pm
Contact:
Denmark

Re: Preamp on my APX-4A

Unread post by Buzzard » Wed Nov 09, 2016 4:08 pm

Hmm 8O

If the hole is too tight to fit the new plug, make it bigger.

You can use a tapered drill bit for wood, or a round file,
but be gentle, you cannot easily replace the wood you have removed.

BEFORE you do that, make sure that everything works with the new plug.

:idea: a few pictures of your repair process can help others. :idea: :D

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: http://www.yamahamusicians.com/forum/vi ... =24&t=7004 :idea:

User avatar
Miks
Specialist Moderator
Specialist Moderator
Posts: 1323
Joined: Fri Oct 31, 2008 1:00 am
Contact:
Germany

Re: Preamp on my APX-4A

Unread post by Miks » Wed Nov 09, 2016 5:17 pm

Buzzard wrote:BEFORE you do that, make sure that everything works with the new plug.
Yes, I second that! Strongly recommended - and IF all works good and IF you're smart immediately buy another one (or two...) of those jacks as a spare - you'll never know :wink:
My (key related) gear (in alphabetical order):
Kawai: K1 II
Korg: M1 (up'd to EX, w/ 'Cool Blue'), M1REX (w/ 'Cool Blue'), Poly-800
Roland: D-50, D-110, D-550, PG-1000
Yamaha: AW1600, DX7IID (w/ 'Cool Blue'), EX5R, RM50, RX5, SY99 (w/ 'Cool Blue'), TG500, TX-802, YMM2
Sector101: SYEMB05 (5x), SYEMB06 (3x), EXFLM2 (1kit), MCD Sweet16 (1x), WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade


http://rescuer-uslar.de/
https://www.facebook.com/Rescuer.Uslar/

User avatar
Pegotico
Posts: 7
Joined: Sat Oct 15, 2016 1:38 am

Re: Preamp on my APX-4A

Unread post by Pegotico » Sun Jan 29, 2017 12:08 am

Miks wrote: and IF you're smart immediately buy another one (or two...) of those jacks as a spare - you'll never know :wink:
I did buy two just in case one failed because of how cheap they were (usually try to do that whenever possible), but I don't see how just buying one makes me less smart. I take that is as some kind of expression which probably i didn't get. Anyways thanks!:)
Buzzard wrote:Looks like you have the problem(s) sorted, well, at least almost. :wink:

at this link: viewtopic.php?f=93&t=8168&p=43772#p43772 showing the color codes on MY AEX-500N, tip is red , ring is white , and sleeve is Black.

Regards
Peter
Turns out it wouldn't work. To my surprise tip is white, ring is red and sleeve is black. That was the only way it worked. Sorry it took me so long to answer.

Will upload some picts. Its working great!!!!

User avatar
Buzzard
Specialist Moderator
Specialist Moderator
Posts: 1665
Joined: Wed Sep 04, 2013 7:38 pm
Contact:
Denmark

Re: Preamp on my APX-4A

Unread post by Buzzard » Mon Jan 30, 2017 9:21 pm

Pegotico wrote:To my surprise tip is white, ring is red and sleeve is black. That was the only way it worked. Sorry it took me so long to answer.
Will upload some picts. Its working great!!!!
I'm a bit surprised that your guitar isn't following the color code, but if it works, leave it as it is. :wink:

Rock on.
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: http://www.yamahamusicians.com/forum/vi ... =24&t=7004 :idea:

jraward
Posts: 1
Joined: Tue Jul 11, 2017 2:23 pm
Great Britain

Re: Preamp on my APX-4A

Unread post by jraward » Tue Jul 11, 2017 2:27 pm

Buzzard wrote:
Mon Oct 17, 2016 9:41 am
Hi Pegotico, Welcome to the Yamaha Forums. :D

Your preamp should turn on when a (mono) plug is inserted into the guitar output jack.

If nothing happens, make sure that the battery terminals are clean and adjusted to ensure connectivity.
:idea: Battery connection is often the reason for malfunction. :idea:

I only have workshop manual for the following preamps: System 20 , System 20s and System 21 (from Yamaha APX-5 and up)

Yamaha usually can and will deliver the schematics for vintage equipment.

Best Regards
Peter
Hey!

I've this same issue with my APX-5A - would you be able to send me the schematics so I can fix please?

Thanks,

James

User avatar
Buzzard
Specialist Moderator
Specialist Moderator
Posts: 1665
Joined: Wed Sep 04, 2013 7:38 pm
Contact:
Denmark

Re: Preamp on my APX-4A

Unread post by Buzzard » Tue Jul 11, 2017 4:03 pm

This service manual should cover: APX-5 , APX-6 , APX-6 L , APX-6 N , APX-6 S , APX-7

APX6 n-SYSTEM20_20L_21_SM.pdf
(336.59 KiB) Downloaded 22 times
Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: http://www.yamahamusicians.com/forum/vi ... =24&t=7004 :idea:

Post Reply

Return to “Yamaha APX Guitar Forum”

Who is online

Users browsing this forum: No registered users and 1 guest