Non working GC

[ShieldJaguar]

Hi ppl,
Built a GC using Brian's LM3875 kit, have checked + double checked my wiring but it still doesn't work.
I think the problem is the trafo/rectifier, so i was wondering can i use batteries?
I've built several headamps using 9/18v split supplies can i adapt one of these for testing purposes?
These split supplies ie. +9v 0v -9 how would i connect them, Brians board has
+V -V +PG -PG
Any help would be appreciated as the GC has sat unfinished for a while
btw i'm a newcomer so nothing technical guys.

Thanks

[rnoble]

You don't have a multi-meter? Start from your mains supply. Test everything - find out where you're losing power with the meter.

[sek]

Hi,

Originally posted by ShieldJaguar
Built a GC using Brian's LM3875 kit, have checked + double checked my wiring but it still doesn't work.

It's very unlikely that Brian's kits don't work. As rnoble pointed out, you should make sure that your power supply works. After all, you won't benefit from a working kit without a working supply...

I've built several headamps using 9/18v split supplies can i adapt one of these for testing purposes?

It depends on your trafo and on the way you populated the recrifier boards. And only if they can supply high enough current. If the BrianGT amp 'accidentally' starts to work with them, they could be overloaded in a very short time.

These split supplies ie. +9v 0v -9 how would i connect them, Brians board has +V -V +PG -PG

+PG and -PG are the two connectors for transformers with independent secondary windings. These are only kept separate on the rectifier boards. As you can see on the amplifier boards, they connect via the copper area in front of the chip.

Brian gives detailed instructions on how to connect a +V 0 -V supply to the rectifier board in his PDF manual. In short: you would have to unsolder and repopulate your rectifier boards, that's why you don't want to try it.

Also, a +-9V supply won't work, the LM3875 doesn't (safely) power up from such a low voltage.

But you can try to use two separate split supplies on your kit. All you would have to do is let each of the two look like one transformer output winding.

If you think of your split-supply's outputs in series, the are 18V supplies (between their respective +9V and -9V connectors). If you feel safe enough to try it, you can connect one supply with it's +9V to the kit's +V and with it's -9V to the kit's PG+. Then the second supply's +9V goes to PG- and it's -9V to the kit's -V. Please make a drawing of that to be sure.

What trafo do you use? Can you probably post a photo from it's label and output wires? Also the way you tried to connect it to the rectifier board?

Sebastian.

[Nuuk]

If you haven't done so already, try reading this ! And as stated above, check your PSU before connecting it to the map circuits to see that you have the correct rail voltages.

If you need help, draw out exactly how you have built your PSU and we may be able to spot the problem.

[ShieldJaguar]

Hi ppl,

Thanks for the posts.
Left it alone for a couple of days, guess what -next time i look. i'd wired the trafo up wrong.
Its now up+running sounds great too.
Thanks to everyone for their help+ thanks to Brian&Peter for the kit!

[Nuuk]

Left it alone for a couple of days, guess what -next time i look. i'd wired the trafo up wrong.

Thanks for coming back and revealing that. It is a good example to new builders, as well as the more experienced, not to overlook the obvious!

How does it sound?

[ShieldJaguar]

Originally posted by Nuuk
How does it sound?

Bit hard to judge at the mo' SirNuuk, as i'm running off the headphone output of my iPod, cos i built it purely as a poweramp.
Next project?

[Nuuk]

Next project?

Take your pick. CDP, pre amp or speakers.