Vox Jaguar organ power supply : rebuild original or redesign? - Page 1
Forum section: electronics / projects

author: Organ Bender
author_rank: Contributor
timestamp: August 27, 2025, 03:04:19 pm
content: Hi all,I need help finding out what modern parts to use to rebuild this power supplyORBuilding a better version of itI am restoring a Vox Jaguar vintage transistor organ. This model is the DIY kit that was sold by Heathkit back in the days. The unit is missing the original (0, -15V) power supply, which has been replaced by a 12V kit. The organ is functioning as is, but I am confident it would be a good idea to make it run in the voltage it was intended to. It would be an opportunity to learn new stuff about power supplies as well.Rebuild original?Now, since the original power supply have been stripped out (still have its chassis though) and that the internet won't provide all the information, I need help identifying what Diode and Zener Diode were used, and finding the modern equivalent.Also, I am not exactly sure what specs to look for for the transfo in terms of VA.All I have is the attached schematic and a couple pictures.Build a better design?Is the original circuit good enough? Any suggestions for a better design are welcome. As soon as it can fit about the same space.Schematic and 1st pic sourcehttps://www.voxshowroom.com/uk/organ/V304_PS.html2nd pic source :https://www.reddit.com/r/synthdiy/comments/140nbj7/are_these_proper_modern_diode_replacements_vox/Complete schematic :https://www.voxshowroom.com/ct/schematics/V304_Jaguar.pdf

author: floobydust
author_rank: Super Contributor
timestamp: August 27, 2025, 05:01:40 pm
content: Welcome to the forumsFor the original parts, I would consider:1N5352B15V 5W zener.1N54043A 400PIV rectifier. A 1N4004 would work but might be a bit on the small side for ripple current.Would add a bleeder resistor say 5k ohm across the output so there are no sparks when plugging in the connector if the caps have any stray charge beforehand.A retromod power supply would be a full wave rectifier and LM7915 or LM7815 or LM317 etc. IC regulator and a couple protection diodes. You want low hum and noise as well as good regulation.The transformer size you'd have to measure it or I'd use a Hammond166J14with a full wave bridge rect. to get around 20VDC for the regulator IC input (at light load).

author: Seekonk
author_rank: Super Contributor
timestamp: August 27, 2025, 05:25:23 pm
content: That design is a 150ma supply. A tint little $2 switching supply can do that with far less heat. Add some extra capacitance to the output. I hardly think noise will be a problem. So for three bucks you are done.

author: floobydust
author_rank: Super Contributor
timestamp: August 27, 2025, 05:43:46 pm
content: Nobody puts in a buck converter SMPS into a classical analog musical instrumentYou'd need extra EMI filtering to keep the noise very low, like the original.I think this organ is sensitive to the exact voltage, for the oscillator pitch as well. There is a -6V rail too.If you're on the cheap, then an Ali/eBay 'LM317 board' with AC input/bridge rectifier would work, it has the bigger heatsink i.e.https://www.aliexpress.com/item/1005008867851379.htmlbut their shipping prices have gone crazy high it seems.

author: Seekonk
author_rank: Super Contributor
timestamp: August 28, 2025, 06:03:05 pm
content: Classic, VOX was junk when it was new. I was repairing transistorized organs back in the 60's. Plenty of audio equipment has SMPS power supplies.

author: themadhippy
author_rank: Super Contributor
timestamp: August 28, 2025, 07:49:22 pm
content: QuoteAnd said equipment has been designed and tested to work with a smps

author: floobydust
author_rank: Super Contributor
timestamp: August 28, 2025, 08:24:36 pm
content: Quote from: Seekonk on August 28, 2025, 06:03:05 pmVOX was junk? Tell The Beatles, Queen, The Animals, The Doors, Iron Butterfly etc.Are you recommending Casio or Radio Shack?No keyboards were really reliable in the 60's as costs had to be kept down. If that's what you mean by "junk". Modern VOX is junk though, some soulless OEM doing the designs and I thought Korg owns them.It's not designed nor has the components to deal with SMPS hash and harmonics in the MHz. You could add filtering and debug the swooshing and heterodyning noises, but this takes a lot of time.Are you talking about using "$3.00" wall-wart or buck-converter board? Because most of the cost of OP's project is in the power transformer, if a new one is to be used."150mA" but it's rated as a 15W mains load. Maybe the 12V supply could do 15V?

author: TimFox
author_rank: Super Contributor
timestamp: August 28, 2025, 10:03:31 pm
content: Here's an eBay example of an old-fashioned linear regulated DC supply for 15 V @ 150 mA.https://www.ebay.com/itm/286197460040?_skw=15V+150mA+power+supply&epid=170011720&itmmeta=01K3SB5FD1ZFFN00G8FM2NE5ZW&hash=item42a2b2ac48:g:EyUAAOSwk25nT1kp&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1fCfizuBMH8giqjPUHDsovjijiXyi4IBK%2B5x1bKfiaNy7LZpeG9NLD%2FKXT6KHSCul2mpc%2BDDqe8Nwq8CTUEzCrg%2FbMeAxPZK2ohHYZbyr32%2FF8YsA7IgU5d79%2Fc8kqlI1u20q9tmXUQa9yPrXoa48xBURVqCk2sn%2BnIa%2F278DKaL5teQu7ySp0efT5MyV6jmyaJAIBgzgSh1dTL659ttFJsKXl9NARhgVcb693Pn%2FAwAoJNPQ0kNYW1xbXSpnWGzhT%2FcMGo1rCNZJ1CEgT%2B2kefyh4qMy7ZG7juqqU127dDCA%3D%3D%7Ctkp%3ABk9SR9b2laueZg&pfm=1I can't vouch for the seller, but I was happy with those Lambda power supplies years ago.

author: Seekonk
author_rank: Super Contributor
timestamp: August 30, 2025, 05:56:22 pm
content: Oh my gosh, the sky is falling. Half wave rectification and a zener. That sure sounds like they cared about regulation. EMI is a little issue easily dealt with. I know I get confused sometimes thinking I am actually on an electronics board where people know electronics. I spent a lot of time in high end audio, I knew Saul Marantz. What made the musical side classic was bad design. Back a while I was selling General Instrument GT109 germanium transistors. This was about the tail end of germanium production. The leakage of these were so low they looked like silicon. People who made fuzz boxes told me that of over a hundred germanium types the tested that these were the best. A little added noise isn't a problem, it is a feature. I'm more of a looks original, works better. I hadn't thought about the days of working with bands in a long time.Today's joke. What do you call a bass player without a girlfriend.Homeless.

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: August 30, 2025, 08:18:56 pm
content: I had heard the same joke about a drum player.Back on topic. Part of the sonic signature of those early musical instruments were hum, noise and distortion. Like good wine, it gives them “character”.Of course, relative to modern devices, they are crap.But I can’t think of Ray Manzarek playing Light my Fire or Doug Ingle playing In-a-Gadda da Vida on a modern synthesizer.

author: floobydust
author_rank: Super Contributor
timestamp: August 30, 2025, 09:28:20 pm
content: Quote from: Seekonk on August 30, 2025, 05:56:22 pmWow you've met the late greatSaul Marantza few people here also claim that.But it doesn't increase your knowledge of electronics anymore than meeting a Kardashian makes you more prettyNone of his vintage products I've repaired use a buck-converter SMPS. If you know of any let me know, to see how he did the EMI filtering.Countless problems guitar players have powering their effects pedals with 9VDC SMPS. Y-cap aside, it can be done with extra EMI filtering -but a linear PSU is easy.A zener shunt regulator, 1/2 wave rectifier was par for the course in 1967 where semiconductors were expensive, to keep BoM costs down.VOX could have added 3 diodes and a transistor etc. regulator. The Jaguar Heathkit was $350 in 1968 or $3,250 in today's dollars. It was already expensive, near colour TV prices. A Heathkit IO-17 scope was $80.My position, keep it simple - a linear power supply and have no drama. The buck-converter saves no dollars either.A 15VDC medical grade (no Y-cap) wall-wart could also work for a power supply I think.

author: Zoli
author_rank: Frequent Contributor
timestamp: August 31, 2025, 06:40:56 am
content: Quote from: floobydust on August 30, 2025, 09:28:20 pmOT:I've opened up(curiosity) a 5V/3A medical SMPS brick; it has two Y-caps, one from primary, one from secondary./OT

author: trobbins
author_rank: Frequent Contributor
timestamp: September 02, 2025, 04:59:42 am
content: Hum may have influenced the choice of half-wave rectifier, so as to avoid 100/120Hz ripple being audible - depending on speaker sensitivity.A 1N4002 or UF4007 would suit, as the peak diode current would be way below a '1A' diode's rating, given the small power transformer. A modern 1000uF 35V e-cap would also be an improvement if you lay out the wiring appropriately.The 15Vdc loading appears to be below a nominal 100mA, given the 33R dropper to the zener, but that assumes the zener is meant to fully regulate against all variations, and makes some power transformer assumptions.The photo indicates the size restrictions for the transformer - can you confirm you still have the internal metal enclosure for that power supply?The original diode was by International Rectifier - akin to a 2E4 - its shape is very recognizable.I can only see one e-cap in that sample photo - was that a dual cap part ?Can you identify any stock power transformers that may suit the physical size and winding voltages you are after? Some power transformers for diy may come with multiple secondary windings, and anything within a volt or two of 20Vac may be fine (given mains voltage, and winding resistances, and zener headroom).One 'issue' is that you are going to connect parts to mains AC voltage, and mains AC is also part of the wiring loom and connectors. You may be safer to use a compliant plugpack with linear supply that provides a regulated 15Vdc at say 0.2-0.5A. That should remove possible hassles with protective earth noise loops with other connected audio equipment, and keeps mains wiring out of your device, and avoids having to construct an internal clone supply.

author: Haenk
author_rank: Super Contributor
timestamp: September 02, 2025, 06:37:17 am
content: The easy way: Go with an Aliexpress LM337 board:https://de.aliexpress.com/item/1005005866096878.html(random example, *plenty* of other offerings)and add a random 18-20V wall wart transformer.Ignore the positive rail. That's an extra, might be useful for "something" in the future.

author: Organ Bender
author_rank: Contributor
timestamp: September 03, 2025, 05:35:58 pm
content: Sorry to come back to this so late, I was kind of expecting some email notifications for your replies. So many, that's encouraging!Quote from: floobydust on August 27, 2025, 05:01:40 pmMeanwhile, I got to talk to a guy on Reddit who did rebuild his own unit and he said he used exactly that with great success. I'm still not sure if I will go for the rebuilt though.Quote from: floobydust on August 27, 2025, 05:43:46 pmThe oscillators pitches are not sensitive to voltage fluctuation. I've test the unit using my variable power supply, going from 12 to 15V and the only thing noticeable was the output volume. Since the -6V is a simple voltage divider, I don't see any concern for finding the right parts.Quote from: UnijunctionTransistor on August 30, 2025, 08:18:56 pmYou should see the mechanical design of this thing, it is really crapy. But, hey!, it sounds so good!Quote from: floobydust on August 30, 2025, 09:28:20 pmThe more I read the comments and the more aim to go simple, as you say. If I don't go with the original rebuild, I will look for something I don't have to add parts to. So no buck converter.Quote from: trobbins on September 02, 2025, 04:59:42 am- Yes, I still have the metal enclosure.- Yes, the cap is a dual- I've found a not too expensive 20vac transformer about the same size. Didn't buy it yet.

author: Organ Bender
author_rank: Contributor
timestamp: September 03, 2025, 06:08:56 pm
content: Thanks for all of your replies.This gives me some more perspective. I wish I knew more about power supplies design!The more I know, the more I think I will go with buying some linear power supply. I really like the idea of keeping vintage instruments "original" but the more I read, the more I see that rebuilding this one can be a waste of time, with all the great modern products readily available. This would have been different if I only had to replace a couple parts.I had a look at this one, it seems to fit the requirements and is easy to install. Tell me what you think.https://www.digikey.ca/en/products/detail/mean-well-usa-inc/PS-05-15/7705816?_gl=1*1r6tmpe*_up*MQ..*_gs*MQ..&gclid=Cj0KCQjwzt_FBhCEARIsAJGFWVmZl8Y7_ytNWXPZdzBpv74Otgm0xbyaOMrA1hzkuQFAFZLQ-_Vwfj0aAp4BEALw_wcB&gclsrc=aw.ds

author: TimFox
author_rank: Super Contributor
timestamp: September 03, 2025, 06:41:08 pm
content: That MeanWell supply is a switch-mode unit, not a linear supply.MeanWell is a reliable manufacturer.

author: Organ Bender
author_rank: Contributor
timestamp: September 03, 2025, 07:49:34 pm
content: Thanks for pointing out. I did ask google for a linear supply

author: TimFox
author_rank: Super Contributor
timestamp: September 03, 2025, 08:05:53 pm
content: It was hard to force DigiKey’s search to linear supplies: they’re all expensive.Probably better to find obsolete units on eBay, like the discontinued Lambda United I cited above.The decent switcher might well work, and it’s safer than building one from scratch.

author: Organ Bender
author_rank: Contributor
timestamp: September 03, 2025, 10:57:59 pm
content: Agree, Mouser was easier to convince in the linear search. And I was surprised too how expensive they are.I will look at the Lambda again.But now I am puzzled, if only I had an smps in hand to test it...

author: Organ Bender
author_rank: Contributor
timestamp: September 05, 2025, 05:23:19 pm
content: Quote from: TimFox on September 03, 2025, 08:05:53 pmI looked at the Lambda link you gave. The problem I see is how to attach it inside the organ.Then I saw there is a lot of psu made by Condor, like this one. It is a bit more than I need, but looks interesting. There is also a +/-15v 0.4A model at about the same price.https://www.ebay.ca/itm/314111553149?_skw=condor+power+supply+15v&itmmeta=01K4DDGPVPGCHMWV6DPHNJVBN0&hash=item492281ee7d:g:3W4AAOSwqrli~UiW&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1fIPjLZhoa6gYFSmcgRBBUbpG0P5N1mJQfBr%2F4ktajTUevoRa0kLJjMHgwn89O%2BpcdFgKlDdeiba8pgRpcsua%2Ft%2BrNcvstg3Kkgd8iPfIEE3I1w%2FlgtVtMqUkAEtsxwIY2oyF2oKRcnsQhhsFXLzkWs7PbWqjjvBBL0PSg4ue7xyL1o9orW4v7C5eV%2BGpfBhRZDa2e8XWZKFn6Jl0kUKDT5dMrQdy1KQMsuhmQdQolDdwCR8nOuuD8huAvk5JqbHMwrOLo0Ri0MF6DxAkL2Z4v9wB2LRNVvMDLSOIN4a9Zh5w%3D%3D%7Ctkp%3ABk9SR_jtwq2jZgWhat do you think?

author: Kofen
author_rank: Regular Contributor
timestamp: September 05, 2025, 07:18:29 pm
content: So I am late to this thread and have only skimmed it, sorry if I missed something.But IMHO I would just rebuild the original power supply. Is it the best? No, are there other sources for noise and hum in the organ? Yes indeed.But we are using them and have used them for a long time, trying to spend money to improve one part might not yield the results you want.I spent 13 years or more in the past servicing these kind of musical gear, I would fix it "like new", with current circuitry and have fun with it. My own continental was fully serviced years back, works great, all original expect for quite a few parts needing replacement(A lot of the divider caps on the oscillator boards tend to crack). There is also worth looking into the grounding if you are really bothered by the hum after recap and refurb as a lot comes from ground loops.But if you like a project, go ahead, but please make it easy to reverse and keep the original parts as they are getting a bit sparse and futher buyer might want it in stock configuration(There is lot of superstition and "voodoo" feelings when it comes to vintage music gear).They where built in a time where requirements were less strict, it is fine for most part, you do get some issues from time to time with getting it to comply with modern gear, but there are ways to deal with it.EDIT: If it is lacking fuses and protection on the mains, that should of course be updated so it is safe, but thats that I think as a first go.

author: Organ Bender
author_rank: Contributor
timestamp: September 05, 2025, 08:44:23 pm
content: Hi KofenThanks for the encouragements! I'm glad to have someone who worked with these organs in the conversation.Quote from: Kofen on September 05, 2025, 07:18:29 pmYeah, I am aware of the superstitions!My first thought was to keep it original, then I thought it might be more complicated, but then, I am beginning to think that the original might be more simple and perhaps cheaper. I kind of change my mind with each new comment...I have most of the parts list. The only thing I need to confirm is the power rating of the transformer.With 20V secondary outputting 150mA, a 3VA should be fine, right? Or should I get a little more, like 5VA maybe?Can someone confirm that?

author: themadhippy
author_rank: Super Contributor
timestamp: September 05, 2025, 08:50:17 pm
content: Quote3va is right on the limit,5va will give a bit of headroom

author: Kofen
author_rank: Regular Contributor
timestamp: September 05, 2025, 10:27:55 pm
content: Quote from: Organ Bender on September 05, 2025, 08:44:23 pmTransformer rating I can't remember, but when it comes to service, the definatly cheapest way is to just refurb the power supply. Power transformer is fine no? First would would be to replace the caps, do you need to replace the zeners? Are they out of spec?

author: Organ Bender
author_rank: Contributor
timestamp: September 06, 2025, 07:14:59 pm
content: Quote from: Kofen on September 05, 2025, 10:27:55 pmThere is nothing left of the original power supply, except for the fuse holder! It has been replaced some 40-50 yeas ago, maybe (it does have Ge transistor in it!), with a 12v power supply kit.Quote from: themadhippy on September 05, 2025, 08:50:17 pmGreat! Thanks a lotNow let's shop for some parts

author: Organ Bender
author_rank: Contributor
timestamp: October 03, 2025, 01:41:01 pm
content: Updates on the project!I finished rebuilding the power supply. It works great but, yes, a bit noisy. The output jacks were picking up a lot of 60Hz, being just aside from the transformer, as you can see on the picture. So I ended up moving it away from the rest of the circuit. It improved things quite a bit, i.e. now, instead of having a 60Hz buzz, it is more like a sine wave hum. It is more quiet, but still it remains noticeable when played through an amplifier.So I tried all I can think of to try and eliminate the hum, like even moving the output jacks away and add a high pass filter on the output. This does not change much.Any idea what I could try next?Would adding a filtering stage to the power supply help? If yes, how should I implement it?

author: floobydust
author_rank: Super Contributor
timestamp: October 03, 2025, 08:26:27 pm
content: Soldering connection at the filter cap's (-) needs to be redone. I don't see any solder sticking there. It would cause hum.It looks wired wrong, at the octal socket? Mains Neutral (white wire) does not go right next to the -DC out (red wire) on the schematic. Maybe check the socket pinout.I think Vox wanted more spacings for the mains high voltage and used pins 2,7 blank for that. If the socket is missing pins/stubby etc. you might be able to remove one and move it over.Not connecting the IEC ground pin, it makes me squirm but this was a 2-prong power cord device. I put heatshink over all mains connections just for safety.So it's noisier than the old 12V PSU was?

author: Organ Bender
author_rank: Contributor
timestamp: October 08, 2025, 06:16:35 pm
content: Quote from: floobydust on October 03, 2025, 08:26:27 pmGood observation. I soldered it properly with no change in the noiseQuote from: floobydust on October 03, 2025, 08:26:27 pmHere I had to move the -15 wire because its lug was broken. I rigged it bypassing the power switch, so I can confirm the spacing does not have a significant impact.Quote from: floobydust on October 03, 2025, 08:26:27 pmThe new one is a bit quieter than the old 12V. At least!And I will of course put some heat shrink when I reassemble it for good!I also tried different ac outlet, different amps and power cords. What next?

author: Organ Bender
author_rank: Contributor
timestamp: October 14, 2025, 05:04:28 pm
content: Hi againFor those interested, this is the conclusion to this little saga, I finally solved the hum problem. It was because of a little rewiring I did at the beginning of the build. I did change the primary side of the circuit in order to have the Hot going to the fuse first and then to the switch. Isn't it the safe way to wire a power supply? So I ended up just reverting it back to '60's security standards and the hum was gone. Only a subtle vintage noise remains, which is totally acceptable.Here is the part's list I used for reference, may it be useful for someone :Triad Magnetics 20V, 5VA power transformer (part #237-1643-ND at Digikey)1N5352BG zener diode1N5404G rectifier diode

author: floobydust
author_rank: Super Contributor
timestamp: October 15, 2025, 04:48:55 pm
content: Thanks for the update. Good you found it because the PSU looked good and should not be causing hum so it was a bit puzzling.You always want the fuse first on Hot/Line/hazardous live. It's common sense and the safety standards demand it. It typically comes in and goes to the fuseholder tip first.There is no fuse on Neutral permitted, because if it blows you still have unfused Hot inside there and granny's house can still burn down.Why? Because a short to anything should blow the fuse. If Hot has no fuse, then the fault current is the branch circuit's limit, the 15A circuit breaker which is a bit much for the smaller wiring.But the Hot wire is a source of AC hum when nearby audio circuits.Keyboards put the on/off switch at the back, so that wire is away from any sensitive circuits.I don't know where the wires run in this Vox.

author: Organ Bender
author_rank: Contributor
timestamp: October 15, 2025, 05:50:46 pm
content: Quote from: floobydust on October 15, 2025, 04:48:55 pmThis is what I usually do. But the way it is setup, there is no way to have the fuse on the hot without going nearby the signal wires.Quote from: floobydust on October 15, 2025, 04:48:55 pmThe AC wires go all the way to the control board, at the On/Off/Vol switch potentiometer