F5 power amplifier

[Zen Mod]

check mounting of outputs

torque , goo

[Rush]

Originally Posted by uvellani

I am having a problem on one of the channels. This was working fine for over a year when all of a sudden one channel developed this problem. I changed the adjustment pots based on suggestion from this forum, and it worked for a few days of extended testing and listening. But now it's doing it again. The bias voltage on the output resistors dropped from .575 to about .400 at first but now it is all over the place. The other channel is rock-steady.

Do you think the thermistors themselves could be a problem? I know, I know. I could change them and see. But unfortunately, due to the beauty of my chassis layout, I have to take out the power supply and the big caps out first to get at the amp board. So iterative troubleshooting is a bit of a pain. Some pointers would be helpful.

Thanks
UV

Could it be a slow oscillation?

Rush

[bobodioulasso]

Bah, next chassis vill be more serviceable i presume.

[wengtech]

i have a good quality of toroidal transformer with 2x36vac 500va
and i want to use them in my F5
questions:
1. is that possible to regulating the 2x36vac into 2x18vac without loosing the current? anyone have the schematics for this?
2. if regulating is possible, should it placed before the filter caps (the 15000uf), or after?

thanks.

[labjr]

Originally Posted by wengtech

i have a good quality of toroidal transformer with 2x36vac 500va
and i want to use them in my F5
questions:
1. is that possible to regulating the 2x36vac into 2x18vac without loosing the current? anyone have the schematics for this?
2. if regulating is possible, should it placed before the filter caps (the 15000uf), or after?

thanks.

How many primary windings are there? What country do you live in?

[wengtech]

primary 0-220-250
secondary 0-36-55 0-36-55
addition 18-0-18

shown on my toroidal transformer.

[labjr]

I was hoping you lived in USA. Looks like that isn't the case. Regulating the rails for an amplifier is a project in itself. I would say you're better off buying the correct transformer and putting that one aside for another project.

[wengtech]

i am in indonesia.
i just hoping not to be redundant.
if i saw at the F5 manual, said the regulated supply like zen variation #3 or #5 are good to applied on F5.

and i found on googling this kind of circuit:


but don't know yet is that a good schematic or not.

[Floric]

Hi,

I don't know that schematic, could work. But you would need adequate heatsinks for it. In fact you need twice the heatsinking capability than the original amp for your amp+ps.

At least here in europe the main factors for the costs on an amp like this are the heatsinks and the transformer. I think you will get a cheaper and better amp if you buy an adequate transformer.

Best regards

Flo

[AndrewT]

One cannot easily regulate AC voltage.
We generally adopt converting the AC to DC and regulate to the required voltage.

Starting a project with the wrong transformer is silly.

Buy the correct transformer, or select a project that will work properly with the transformer you have.

BTW,
you have 19Vac tappings on your transformer, but the VA available is ~18% of the total. i.e. 90VA from each of the two 19Vac windings, (if the wire to the 55Vac taps is the same as the wire in the remainder of the winding).