50W Stereo Kit amp runs for 1 min, clips then turns off.

[lanchile]

So in the data sheet it says Vpin7 − V− ≥ 9V. Mine is around 5V and falling. This is an issue. The V- being positive is also an issue. Where do I go from here?

pin 7 is ground!!!

 

[Al600]

I've done the measurement and it seems that they are 31.5V and -3.7V. There is obviously something not right here. When the amp is first started these values both climb towards positive until settling at the above values.

 

[lanchile]

can you post a picture of board and connections?

 

[lanchile]

do you have a center tab like this?

 

[lanchile]

or this set up!

 

[lanchile]

Fuses checked. The results are not good. The positive rises on startup to around 32.5V and the negative starts at about -7V and rises to about -3.5V. This is the problem. No idea what next.

you are missing the V- voltage!!! Does your transformer have a CT? Did you check the Bridge rectifier if it was connected the right way? the ~ is for the AC from transformer and the - and + are for the V- and V+ voltages

 

[Al600]

Here're some new photos. I also took out the componants for the 15V rail. Bridge rectifier is the right way around. The V- voltage is indeed missing, no idea why.

 

[lanchile]

ok...lets get organized here. Where is the Center tab of the transformer that is suppose to be in the middle of connection?
also did you measure those two wires coming in (secondaries) to power supply?

 

[Al600]

Not sure what a centre tab is. Sorry but this is my first kit. The wires going to the power supply from the transformer are delivering 26V AC.

 

[lanchile]

CT is the center tab of transformer look the pictures and look your schematic it says CT that means center tab from transformer.

 

[Al600]

Just looking at the kit manual. The transformer has 1 primary coil and 2 secondarys both providing 25V and 6A. Should I be using both of the secondary coils or just the one. I'm measuring 25V between the 2 outer pins of the power supply input.

 

[Al600]

Here's the link to my transformer. Does it have a centre tab because I can only make out 2 seperate secondary coils.
Altronics - Your One Stop Audio Visual & Electronics Supplier

 

[AndrewT]

Have you bought a 230:25-0-25Vac transformer?
or
did you buy a 230:0-25, 0-25Vac transformer?

edit,
the altronics eventually downloaded.
You have bought a 240:0-25, 0-25Vac transformer.
This is a dual secondary transformer.

 

[Al600]

I'm honestly not sure. Can you tell from the link I posted? Should I be connecting the 2 secondary coils in series to make 50V or just use one 25V coil?

 

[lanchile]

I'm honestly not sure. Can you tell from the link I posted? Should I be connecting the 2 secondary coils in series to make 50V or just use one 25V coil?

use one secondary! White/orange or red/black. also check that bridge rectifier (position)

 

[Pixo]

I'm honestly not sure. Can you tell from the link I posted? Should I be connecting the 2 secondary coils in series to make 50V or just use one 25V coil?

looking at the toroid, it's got two secondaries - red & black is one secondary, while white & orange is the other.

 

[lanchile]

Have you bought a 230:25-0-25Vac transformer?
or
did you buy a 230:0-25, 0-25Vac transformer?

edit,
the altronics eventually downloaded.
You have bought a 240:0-25, 0-25Vac transformer.
This is a dual secondary transformer.

Andrew, I do not think this X has a CT!

 

[Al600]

Ok. So I'm using one secondary and the rectifier is correct. From the toroidal schematic you posted earlier perhaps I need to use both of the secondary coils to power the rectifier?

 

[lanchile]

Ok. So I'm using one secondary and the rectifier is correct. From the toroidal schematic you posted earlier perhaps I need to use both of the secondary coils to power the rectifier?

Nope! you just need one secondary for this amp, but you will need the center tap.

 

[AndrewT]

He has bought a Dual Secondary transformer.

If the instructions only specify a Centre Tapped transformer then he must convert the Dual Secondary to Centre Capped.

Should I order the funeral director now, or wait till he stops posting?