Transformer modification on vintage amps

[HuxLux]

Hey guys!

Been looking at this 1989 Gallien-Krueger 800RB.

As the amp is from Australia, which is where I live, it seems as though the transformer has been modified in some way so that it is plug and play in our country. You can see this in the labels that have been stuck on the fuse and IEC cable area. The current owner has no knowledge of this, I would say it happened many years ago.

I do not doubt that the amp works as it was serviced some years ago, evidenced with a test tag sticker.

Does anyone have experience and/or knowledge about doing this to vintage amps? Particularly old solid state ones.

Do you think the transformer would have been swapped or rewound? Not sure if this is a silly question.

Should I expect any issues because of this? Any difference in sound?

Should I ask for them to send me a photo of the internals?

Thanks for any advice or wisdom!

 

[Wasnex]

Different transformers were used over the production of the 800RB. The schematics I found show a 240V transformer and a dual voltage 110-220V transformer.


The 240V transformer only has one primary winding, so it can't be changed to 120V. There was probably a 120V transformer as well. Some of the pages are missing from the service manual.


The dual voltage transformer has two primary windings. For 110V the windings are wired in parallel. For 220 they are wired in series.

 

[HuxLux]

Different transformers were used over the production of the 800RB. The schematics I found show a 240V transformer and a dual voltage 110-220V transformer.


The 240V transformer only has one primary winding, so it can't be changed to 120V. There was probably a 120V transformer as well. Some of the pages are missing from the service manual.


The dual voltage transformer has two primary windings. For 110V the windings are wired in parallel. For 220 they are wired in series.

View attachment 7234202

Thanks for your reply!

So, do you think an aftermarket transformer was put in this 800rb?

 

[agedhorse]

It’s probably a factory 240V transformer. I would want a picture to verify.

This was not uncommon for US export models to AU/NZ.

 

[markjazzbassist]

definitely aftermarket, these came with an attached power cable, as you see that was removed for an IEC and the fuse added there.

 

[Stewie]

My 800RB had a modern style IEC cord. Can’t remember if there was a fuse next to it

 

[Wasnex]

Thanks for your reply!

So, do you think an aftermarket transformer was put in this 800rb?

It's possible, but I doubt it.

 

[agedhorse]

definitely aftermarket, these came with an attached power cable, as you see that was removed for an IEC and the fuse added there.

No, that was stock for one of the later versions, when they were transitioning from fixed cordset to IEC. I have seen quite a few like this.

 

[nickonbass1]

Hey guys!

Been looking at this 1989 Gallien-Krueger 800RB.

As the amp is from Australia, which is where I live, it seems as though the transformer has been modified in some way so that it is plug and play in our country. You can see this in the labels that have been stuck on the fuse and IEC cable area. The current owner has no knowledge of this, I would say it happened many years ago.

I do not doubt that the amp works as it was serviced some years ago, evidenced with a test tag sticker.

Does anyone have experience and/or knowledge about doing this to vintage amps? Particularly old solid state ones.

Do you think the transformer would have been swapped or rewound? Not sure if this is a silly question.

Should I expect any issues because of this? Any difference in sound?

Should I ask for them to send me a photo of the internals?

Thanks for any advice or wisdom!

Hi,
I've had two 800RB's & a 400RB which were on US (110-120V) voltages converted to UK (240V) with no issues.
I brought them back to the UK from US. These old classic GK's are not that common in the UK.

Swapped out the original transformers for more efficient & lighter toroidal versions - which I would think is an actual improvement on the original.
In fact, I sold one of the 800RB's to someone in Australia

If the transformer has been changed & it was a proper job, should be no issues or change in power/sound etc... and if it was replaced with a toroidal transformer the amp will be lighter & less prone to IEM too.

 

[HuxLux]

Hi,
I've had two 800RB's & a 400RB which were on US (110-120V) voltages converted to UK (240V) with no issues.
I brought them back to the UK from US. These old classic GK's are not that common in the UK.

Swapped out the original transformers for more efficient & lighter toroidal versions - which I would think is an actual improvement on the original.
In fact, I sold one of the 800RB's to someone in Australia

If the transformer has been changed & it was a proper job, should be no issues or change in power/sound etc... and if it was replaced with a toroidal transformer the amp will be lighter & less prone to IEM too.

Thanks for sharing your experience!

Great to hear that the amp will likely still sound like it is supposed to!

So far, the seller has been unwilling to open the amp up and take a photo for me. Do you think I should push them on this before I buy it? Would that be a non negotiable for you?

Seeing as it has been serviced, tested and tagged by an audio repair business, you would assume that the modification has been done to a high enough standard?

 

[agedhorse]

I would want to verify, especially because this is a safety related issue.

 

[nickonbass1]

So far, the seller has been unwilling to open the amp up and take a photo for me. Do you think I should push them on this before I buy it? Would that be a non negotiable for you?

Seeing as it has been serviced, tested and tagged by an audio repair business, you would assume that the modification has been done to a high enough standard?

TBH some people are a bit loathe to take things apart, or are not confident to do so. I know I am, unless something's not working or needs tweaking/fixing.
For me personally, that wouldn't be a deal breaker as long as the amp works OK.
Guessing the amp's too far from you to have a look at?
If you have some concerns then maybe have a video call with the seller, and get him to power it up & show you it's working OK.

If it has been serviced & modded by a proper audio repair business as you say, I personally wouldn't be too worried.
They may have even recapped it too, which would also be a bonus.

Just out of interest how much is the seller asking for it?
I sold a 800RB to a chap in Australia for about £400 plus shipping back in 2017. He wanted it as apparently these amps are uncommon in AU.

 

[agedhorse]

I would worry about a “re-cap” as well, I see plenty of examples of poor quality work replacing perfectly caps.

 

[HuxLux]

TBH some people are a bit loathe to take things apart, or are not confident to do so. I know I am, unless something's not working or needs tweaking/fixing.
For me personally, that wouldn't be a deal breaker as long as the amp works OK.
Guessing the amp's too far from you to have a look at?
If you have some concerns then maybe have a video call with the seller, and get him to power it up & show you it's working OK.

If it has been serviced & modded by a proper audio repair business as you say, I personally wouldn't be too worried.
They may have even recapped it too, which would also be a bonus.

Just out of interest how much is the seller asking for it?
I sold a 800RB to a chap in Australia for about £400 plus shipping back in 2017. He wanted it as apparently these amps are uncommon in AU.

Thanks for your insight!

Yeah, I don’t really blame him for not wanting to open it up. I’ve left him hanging since he said no while I think about my options. We will see if he changes his mind.

He’s asking $1400aud (670gbp) which too much. I would be willing to pay around $1000aud (480gbp). If the modification has been done well, it is in very good Knick for a “horizontal switch” model. I’ve seen that they can often be missing knobs and switches.

I would say they are somewhat rare here, but I’m not 100% sure.

 

[nickonbass1]

Thanks for your insight!

Yeah, I don’t really blame him for not wanting to open it up. I’ve left him hanging since he said no while I think about my options. We will see if he changes his mind.

He’s asking $1400aud (670gbp) which too much. I would be willing to pay around $1000aud (480gbp). If the modification has been done well, it is in very good Knick for a “horizontal switch” model. I’ve seen that they can often be missing knobs and switches.

I would say they are somewhat rare here, but I’m not 100% sure.

Yeah, try & barter with the seller, get the price down if you can. They seem to sell for £450 - £500 here in the UK when they occasionally come up for sale.
I found all three of mine cheap from pawnshops & Craigslist when out on business trips in the states years ago & carried them back in my baggage
If it's been done by a good audio electronics engineer & been 'Tag & Tested' (equivalent of 'PAT' testing here in UK) for safety compliance should be OK.
Swapping out the transformer is not really a difficult job for a competent electronics engineer.
However, as it's an old amp would advise getting someone to at least give it look inside if you get it.
Good luck with getting it!