Ibanez IBZ3

[Ghost_Bass]

Hi

I have this guitar amp with a blown transformer for a few years and now i would like to fix it to lend it to a starting guitarist.
Can someone please tell me what voltage i should choose when buying a new one (230V in, how much out?)? There are three wires coming out of the transformer into the PCB.
Some very nasty pics, if needed i can take close ups of any part with a better camera if you need but not until monday when i'll get it again:
[attachment=61440:PICT0880.JPG]
[attachment=61441:PICT0881.JPG]
[attachment=61442:PICT0882.JPG]
[attachment=61443:PICT0883.JPG]

I cuted the brown and dark blue wires going into the back of the transformer to take it out and get it into a electronic store but they didn't know wich voltage it was to give me a replacement. It's a 24W amp.

Thanks in advance!

Edited October 15, 2010 by Ghost_Bass

[Alien]

Check the voltage rating of the 2 large capacitors on the PCB. If you aim for a transformer voltage of around 2/3 to 3/4 of this value then you'll be in the right ballpark.

You'll need a transformer with a dual secondary coil, which will usually be listed as +/- ##Volts or 2x##Volts.

Check the maximum power requirement on the back of the amp, and make sure the power rating of the transformer is the same as that or a bit more.

It's not a perfect solution, but if the transformer's blown and you can't get a schematic it's about the best you can do.

HTH

A

[Ghost_Bass]

Thank you very much! I'll do that!

Cheers

[Ghost_Bass]

Hi, just did what you sugested and here are my findings. I ask you just one last help to confirm my values and sugest the best option.

[quote name='Alien' post='989538' date='Oct 15 2010, 06:42 PM']Check the voltage rating of the 2 large capacitors on the PCB. If you aim for a transformer voltage of around 2/3 to 3/4 of this value then you'll be in the right ballpark.[/quote]

Each cap has 25V, so i'll be aiming for something betwen 16.6V and 18.75V. I don't realy know the voltages available in the market. Would a 16V be enough or should i look for something with 18V?

[quote name='Alien' post='989538' date='Oct 15 2010, 06:42 PM']You'll need a transformer with a dual secondary coil, which will usually be listed as +/- ##Volts or 2x##Volts.[/quote]

I know what those are, just one doubt - is there a specific order to connect the two red wires (shown in the picture in the 1st post) or they can be connected any way - i supose the black is ground and has to be left in the middle position!

[quote name='Alien' post='989538' date='Oct 15 2010, 06:42 PM']Check the maximum power requirement on the back of the amp, and make sure the power rating of the transformer is the same as that or a bit more.[/quote]

Done that! It's 250mA.

[quote name='Alien' post='989538' date='Oct 15 2010, 06:42 PM']It's not a perfect solution, but if the transformer's blown and you can't get a schematic it's about the best you can do.

HTH

A[/quote]

Your explanation is the best help i had in a couple of weeks of searching. Mailed Ibanez and they simply confirmed my "love" for that make not ansewering me! Great customer service!...

If from what i've posted here if you can advise me a suitable transformer i'll be much apreciated. From what i've learned from you i'm looking for something like:

+/-16V with 0.25A(min) or +/-18V with 0.25A(min)

Do i have this right?

Thanks

[Alien]

[quote name='Ghost_Bass' post='992257' date='Oct 18 2010, 02:40 PM']Each cap has 25V, so i'll be aiming for something betwen 16.6V and 18.75V. I don't realy know the voltages available in the market. Would a 16V be enough or should i look for something with 18V?[/quote]
I'd look for an 18V unit. The next commonly available value below this is likely to be 15V.

[quote name='Ghost_Bass' post='992257' date='Oct 18 2010, 02:40 PM']I know what those are, just one doubt - is there a specific order to connect the two red wires (shown in the picture in the 1st post) or they can be connected any way - i supose the black is ground and has to be left in the middle position![/quote]
The two red wires can be connected either way round. The black is not a ground as such (although it is probably connected to ground at some point), it is the common connection between the two secondary coils.

Secondaries can be connected in series or parallel, in the same way as batteries (except with AC Voltage instead of DC). In this case, they are connected in series.

[quote name='Ghost_Bass' post='992257' date='Oct 18 2010, 02:40 PM']Done that! It's 250mA.[/quote]
250mA is the current drawn from the mains grid. If this is multiplied by the Voltage of the mains grid you will get the power required.
So, 0.25A x 230V = 57.5W (strictly 57.5VA, but that starts to get a bit complicated). A transformer rated at around 50VA should be fine for an amplifier like this one.

[quote name='Ghost_Bass' post='992257' date='Oct 18 2010, 02:40 PM']If from what i've posted here if you can advise me a suitable transformer i'll be much apreciated. From what i've learned from you i'm looking for something like:

+/-16V with 0.25A(min) or +/-18V with 0.25A(min)

Do i have this right?[/quote]
Close! I would say you should look for a 50VA transformer with +/-18V secondaries.

If you have access to RS, then this one should work OK.

[url="http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0504640"]http://uk.rs-online.com/web/search/searchB...t&R=0504640[/url]

Andy

[Ghost_Bass]

Thanks for the reply, technical info and advise. You've been very helpfull!
I'll look in a local store first but if i can't find any at least i know i can send one from RS.

Cheers
Marco