another project looms - HH performer

[Bushbaby]

This is the first time I've had to look at the circuitry inside.........oh dear, what i have I taken on??

   
   
   

[Bushbaby]

Even with the charred zeners, this is what the orginal board should have looked like

   

[AlanBeckett]

It looks like some Plonk believed the Ratings of those Resistors and Zeners, plus 'Modifications not authorised by the Manufacturer'.
Shouldn't be too difficult.

Alan

[Bushbaby]

Hi Alan
I agree. I'm more concerned about the botch job on the circuit board - lots of excess solder!

rob

[AlanBeckett]

That Bus-bar may not be too bad once you've scrubbed off all the old Flux.

Alan

[Bushbaby]

Hi All
I really do think I'm going to need some help with this one as I really does appear that someone has done a terrific botch job. I will have to post the schematic on the private lounge to see what everyone thinks when I post some of the circuit pics.

Now I know why it was only £25!!

Regards

Rob

[Bushbaby]

These are the photos from this evenings investigation. The board does appear to have suffered badly from scorching. The electrolytic caps dont appear to be the correct values at all.

                       

[pwdrive]

The values of C9 & C10 in the schematic you posted show 100uf so far as I can make out, the larger ones that are fitted will reduce the ripple to a certain extent.

I would up rate the two zeners and their feed resistors.

Good luck with it.

[Bushbaby]

what zeners would you go for and I take it that I need to up rate the wattage of the resistors (1/2 watt metal film). Should I be overly concerned about the polyester caps?? The smoothing caps are 6800uF rather than 4700uF which seem a bit high - any issues??

Thanks

Rob

[pwdrive]

If it were mine I would go 5 watt for the zeners and the feed resistors and mount them at least 6mm off the PCB, thing is to get it up and running then troubleshoot any problems as they show up, did it work before you started digging around?

Lawrence