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Aguilar DB728 Voltage Conversion (100V to 240V)

The Funk

By The Funk,
in Amps and Cabs

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The Funk Proficient

The Funk

Posted
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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!

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Owen Grand Master

Owen

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Posted

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. 

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three Veteran

three

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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

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Stoneham Explorer

Stoneham

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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!

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Bill Fitzmaurice Veteran

Bill Fitzmaurice

Posted
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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

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sandy_r Experienced

sandy_r

Posted
Posted (edited)
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 by sandy_r
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BassmanPaul Mentor

BassmanPaul

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Posted (edited)

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 by BassmanPaul
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agedhorse Mentor

agedhorse

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Posted

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.

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The Funk Proficient

The Funk

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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.

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