Guys and Gals......

The transformers that I put into my US 110v Bboxes, or my Japanese 100v Bboxes have a current of 0.8 Amps (800mA)

Now, what would be the minimum amperage I could put in my domestic Jap GF 305 (GF 9191)?

Why? 'Cause I found in a 2 euro store a transformer at "Only 2 Euros"!!!!!!!!

BUT..... IT IS ONLY 0.3 Amps (300mA) would that be strong enough (I think not, but it does not hurt asking)?

Thanks!

well i would say it will be very hot may not work altogether may see it light up but no sound or very distorted,,i would say 800 should be the minimum to me

Thought so........

How about 500mA ???????

i have worked with 500ma before and it does work sometimes it depends the box to test the radio on some but still it may not be that reliable but i have used it in a emergency when did not have anything else

An easy rule is that power rating ant 110V or 220V is the same as DC. You can't create power, or loose power (ok, loose a little)
Them if you know the operating DC of the BBX with the original tranformer while runing AC, then you know the amperage.

If your BBX takes 22W from mains, and DC voltage is about 12V, the transformer is 2A.

Less amperage would work, but this would depend of the power demand. The transofrmer sizing MOST match the worst case, I guees, Both channel driven at max power while tape deck is operating, and dial ligth on ... you mean .. all on.
And main filter is little lie ... when power demand is continuos ... it won't help you.

If the amperage is less, the DC voltage will fall and raise copying the audio wave. Many things like motors suffer a lot when the DC voltage isn't the excepected .. and also that would shield spped variations.

Conclusion,

Put a transformer that at least provide the same amperage as the original.
When I serviced my CF580, I put a bigger one.
Since old tranfsformers were big .. you have enough place to fit an oversized one.

let me refrase just for incase the 500ma is for test purpose but in reality i will always try to match when possible but have had luck using from doner boxes with simular ratings success is correct and we know that as well but if you where to test a box i have used smaller transformer.. well actully i have one here a jvc m70 that i bought with burned up power ic and bad transformer all i had at the time was a tranformer out of a panny 5090 9v but since i needed to test the box it works the tape plays and radio plays,m70 are rated for 15v but since thats all i had i used that.. so yes success the correct way is to match the correct one but if the only thing you have is that until you get the right one then it will work

if you use less than the OEM amperage --
then - at best, you lost your 'headroom'

and at worst --you get NO power, or big heat -or damage

You are rigth in using little power transformer for service purposes.
In fact, since you said that I used this tip to fix my burned RX-DT680, otharwise I would have damaged another thing while trying to put some good IC (the shop sold me a fake and burned one )

What maked me laugh was the question of the 300mA trnaformer(not what you said ramon, Ok I most have used the quote to that post to avoid missreadings ) .

quote:

Originally posted by ramon:
let me refrase just for incase the 500ma is for test purpose but in reality i will always try to match when possible but have had luck using from doner boxes with simular ratings success is correct and we know that as well but if you where to test a box i have used smaller transformer.. well actully i have one here a jvc m70 that i bought with burned up power ic and bad transformer all i had at the time was a tranformer out of a panny 5090 9v but since i needed to test the box it works the tape plays and radio plays,m70 are rated for 15v but since thats all i had i used that.. so yes success the correct way is to match the correct one but if the only thing you have is that until you get the right one then it will work

thats cool success you where ok and what brian brought up was a good topic as you know how hard to work on boxes without a service manual and to really trouble shoot this stuff most of the time is hard, and what i have been able to at least match up a transformer,but i always start out with a smaller transformer unless i have the correct one to make sure the box really works,my only concern is the volume becomes distorted not having enough juice

Well...... I ordered a 1Amp transformer, that should be more than enough.

I know the more juice the better (Original 2 Amps sounds correct.... that is the fuse they have in it.... Oh well, 1 Amp will do, I do not make these babies blare!)