Aguilar DB728 Voltage Conversion (100V to 240V)

[The Funk]

Hi all. It’s been many years since I’ve posted anything.

I have recently purchased an old Aguilar DB728 tube power amp from Japan, which is set to 100V operation. I live in Singapore now which uses UK-style 240V power. I know I could get a step-down/step-up transformer to use with this but I was wondering if there is a simple way to change the voltage setting in the power amp.

I have an old Aguilar DB680 which I purchased many years ago from the US. I took it to a tech back when I lived in London, who changed it to 240V operation - I think by just changing a fuse but I did not ask him.

I also have an old Aguilar DB659 which I purchased from the US a couple of years ago. Aguilar tech support told me how to change the voltage setting to 240V operation and it only involved moving an internal part around and swapping in a different value fuse.

The old Aguilar tech support now seems to be general Korg tech support so I’m not getting any answers from them other than to take it to a tech. I am not sure if there are any techs over here in Singapore I would trust with it - and if it is as simple as the DB659 was, then I would be able to follow any instructions and do it myself.

Does anyone have any knowledge of how to do this?

Many thanks!

[The Funk]

It seems the potentially lethal stuff is hidden away underneath this top layer, for relatively quick and safe valve changes.

[Bill Fitzmaurice]

It's possible that the power transformer has dual primary windings that will allow it. A schematic would probably show if that's the case. Singapore is a tech center, so finding someone knowledgeable shouldn't be difficult. 

[The Funk]

Thanks, Bill. I’ll ask around for recommendations over here.

[Owen]

I bought a Boogie D-180 which had been imported from the US. It came with step down transformer. I asked all sorts of people about ditching the transformer. No one wanted to know. Eventually I thought to ask my brother, the electrical engineer. He opened it, took a different tap off the transformer and it was all good. Moral of the story was find someone who actually wants the job. 

 

I am fully aware that I am using words I do not understand on the technical front here. 

[scalpy]

I have no clue, but am just jealous of the racks of my dream kit you own! Enjoy!

[BassmanPaul]

Try eMailing Aguilar Customer Service and ask them if it is even possible.  Some countries don't allow changeable primaries in their Electrical Code.

[three]

You have some dream amps there! I’m not sure this is much help but my first (of three!) DB750s was a US import. Aguilar were happy to provide a new power module/switch for a very modest fee - a quick install and easy solution. This was a very long time ago and Agi were extremely responsive back then. I’d try agi customer service as Bassmanpaul suggests. There may be a direct number too somewhere - I remember getting direct communications from Dave and Alex back in the day (not sure that will happen in the Korg era). Good luck - a massively impressive power amp

[Stoneham]

Does the bottom of the amp have a removable panel? Or is everything accessed from the top?

The mains toroid is the one under the black cover, there's a good chance it has additional primary taps to convert to 240V.  It's a job for a tech though, there could be very high voltages inside there!

[Owen]

3 hours ago, Stoneham said:

additional primary taps to convert to 240V.  

YES!!! I remembered the "tap" word correctly. Check me out with my tech speak. 

[Bill Fitzmaurice]

Where voltage conversion is concerned it's far more likely that it's done with dual primaries rather than multiple output taps. When there are multiple output taps that's usually to provide more than one voltage supply, as in one for the tube B+, one for the tube heaters, and in the case of hybrid SS/valve amps three for the SS voltage rails, +,- and earth. 

https://www.electronics-tutorials.ws/transformer/multiple-winding-transformers.html

[bremen]

On 02/09/2023 at 21:36, BassmanPaul said:

Some countries don't allow changeable primaries in their Electrical Code.

Really? 

[sandy_r]

On 31/08/2023 at 18:41, The Funk said:

Hi all. It’s been many years since I’ve posted anything.

I have recently purchased an old Aguilar DB728 tube power amp from Japan, which is set to 100V operation. I live in Singapore now which uses UK-style 240V power. I know I could get a step-down/step-up transformer to use with this but I was wondering if there is a simple way to change the voltage setting in the power amp.

I have an old Aguilar DB680 which I purchased many years ago from the US. I took it to a tech back when I lived in London, who changed it to 240V operation - I think by just changing a fuse but I did not ask him.

I also have an old Aguilar DB659 which I purchased from the US a couple of years ago. Aguilar tech support told me how to change the voltage setting to 240V operation and it only involved moving an internal part around and swapping in a different value fuse.

The old Aguilar tech support now seems to be general Korg tech support so I’m not getting any answers from them other than to take it to a tech. I am not sure if there are any techs over here in Singapore I would trust with it - and if it is as simple as the DB659 was, then I would be able to follow any instructions and do it myself.

Does anyone have any knowledge of how to do this?

Many thanks!

 

Hi

Aguilar schematics are rare beasts - maybe to stop people messing with life-changing energies?

 

I think I read somewhere that Aguilar would release a schematic, but only to an approved Tech (seems reasonable)

 

On the schematic for the DB750 they have certainly adopted the same approach you experienced on the DB659 (and possibly similar to that other amp you had re-configured for Mains supply voltage)

 

The schematic shows a double primary (which could be connected in series for 240V type supplies, or in parallel for 110/120V)

 

Interestingly, no Mains voltages are shown on the schematic - and the User Manual for the DB728 does mention alternative mains voltage operation and respective Fuses, so the evidence is in your favour

 

I'd recommend identifying a well-established and respected local Tech who would be willing to do this task, and either they or you contact the appropriate Aguilar representative organisation to request the relevant tech info is provided into safe hands

 

HTH

 

 

Edited September 26, 2023 by sandy_r

[BassmanPaul]

If the transformer details are correct then if the amp is wired for 100V operation then BLK should also be connected to BRN. Similarly GRA should be connected to FIO. these two connections should go out to the mains in.

 

Essentially the power transformer has two primaries. both having 0, 100 & 120.  volt taps.

 

For 100V use the two 100V primaries are wired in parallel. BLK to BRN to line of the mains and GRA to FIO to the neutral of the mains

 

For 120V use the 120V primaries are wired in parallel. BLK to BRN to the Line of the mains and ORA to WHT for the neutral side.

 

For 240V use the two full primaries wired in series so Mains line  in to BLK and neutral to WHT. The ORA and BRN should be linked to complete the circuit.

 

This is a job for a tech and not something that an owner should attempt. You only have one life and you should try to keep it going. 

 

 

 

Edited September 10, 2023 by BassmanPaul

[dclaassen]

I have a Fender which is set up for US 110v...I just use a transformer...no fuss

[BassmanPaul]

Traditionally the US has been 117V not 110V. Here in Canada we operate at 120V.

 

Why go to the expense and weight of a transformer when the amp is capable of 240V operation with a simple, for a Tech, reconnection of the mains wiring?

 

[BassmanPaul]

10 hours ago, dclaassen said:

I have a Fender which is set up for US 110v...I just use a transformer...no fuss

IIRC to change the operating voltage of a Fender amp you have to change out the power transformer to a 240V primary version.

[dclaassen]

21 minutes ago, BassmanPaul said:

IIRC to change the operating voltage of a Fender amp you have to change out the power transformer to a 240V primary version.

Yup

[agedhorse]

On 08/09/2023 at 10:28, BassmanPaul said:

Traditionally the US has been 117V not 110V. Here in Canada we operate at 120V.

 

US and Canada are 120V +/-10%. 

[dclaassen]

Usually referred to as 110v by us old American boomers…:)

[BassmanPaul]

9 hours ago, agedhorse said:

US and Canada are 120V +/-10%. 

Yes I know - I did work I the electricity Generating field after all.

 

I still see US schematics and books referring to 117V mains. 

[agedhorse]

110V, 115V, 117V are all legacy voltages dating back decades. 110V DC was the original Edison standard, 110V AC was the Tesla standard. Between WW1 and the 1960's, the voltage crept up until 120/240V became the defacto standard for the US and Canada. Some designers never changed their 115V or 117V templates, so you do see these referenced from time to time.

[BassmanPaul]

Thank you for that clarification/reminder Andy.  When I arrived in Canada we were already at 120/240V. I had forgotten about the Edison and Tesla standards.

 

[The Funk]

On 07/09/2023 at 03:24, BassmanPaul said:

If the transformer details are correct then if the amp is wired for 100V operation then BLK should also be connected to BRN. Similarly GRA should be connected to FIO. these two connections should go out to the mains in.

 

Essentially the power transformer has two primaries. both having 0, 100 & 120.  volt taps.

 

For 100V use the two 100V primaries are wired in parallel. BLK to BRN to line of the mains and GRA to FIO to the neutral of the mains

 

For 120V use the 120V primaries are wired in parallel. BLK to BRN to the Line of the mains and ORA to WHT for the neutral side.

 

For 240V use the two full primaries wired in series so Mains line  in to BLK and neutral to WHT. The ORA and BRN should be linked to complete the circuit.

 

This is a job for a tech and not something that an owner should attempt. You only have one life and you should try to keep it going. 

 

 

 

Thanks, Paul. What you’ve described there is beyond me so I will try an amp tech here. I’ll post an update once I have one.

[Chienmortbb]

On 14/09/2023 at 18:04, BassmanPaul said:

Edison and Tesla standards.

Damn that Musk!