Ashdown Evo II 500 Blowing FS1 & FS2

[The Dude]

Ok. Looking through the schematics you linked, there is another version. I believe I was looking at the wrong one. My apologies. I believe the correct page does not have the zener diodes. It instead has 7815 and 7915 regulators. Do you have the regulators? They are IC4 and IC10. If so, are either of those shorted. Again my apologies for the wild goose chase.

[The Dude]

Sorry, I was typing while you posted. Yes, I see the regulators in your pics, so see my post above.

[BassRepair]

Maybe I am looking at the wrong set of schematics. The ones in this picture shows the Z1 and Z2.

https://imgur.com/seXf5ku

Regardless, I do see the two regulators next to IC5(which has the heatsink). I can't see the designation in the pictures but I assume those are the ones you mean?

In the pictures the metal heatsink bits look a bit discolored. I'll check them for shorts.

[The Dude]

Yes, I believe we were both looking at the wrong schematic. The correct one is page one of this........ I think.

ashdown abm500 preamp.pdf

[BassRepair]

Alright, that one you just linked looks like it's only the EQ board.

Although, the date on that one says Feb. 2002 and the stamp on my board says March 2002.

Getting closer, I think.

[The Dude]

Lower right of page 1 is the low voltage supply circuit on the .pdf I uploaded in post #19. I'm pretty sure that's the circuit- looking at your pictures. (scroll up to the first page)

[BassRepair]

I see the issue. I was looking at the post/pdf on my phone and it only opened the 2nd page. On my desktop, I can see the whole thing now. Yes, that looks like the right schematic now. Thank you for that!

Okay, so I am looking at IC4 and IC10 for shorts. Will there be anything visual I can spot? As I mentioned above, the Fin/heatsink on both looks a little discolored on the edge(I think visible in the pictures).

[The Dude]

Parts don't always show visual signs of being bad. You'll have to check leg to leg on each regulator and see if you measure shorts. I would check both +&-15V regulators for shorts. You may as well check the 12V regulator for shorts also (IC5). For the 12V regulator, you'll have to either unsolder it or temporarily remove the tube (easier) so you're not measuring across the filament (which will show as near shorted).

[BassRepair]

Forgot to add this. Here is a pic of the burnt traces. They seem to start(or end) at one central junction point but one goes to the black wire "To Power Amp"(black dot) and the other seems to connect to one of the transformer wires(red dot).

https://imgur.com/wr8GVgz

[The Dude]

Aside from finding the short, you'll have to rebuild/run jumper wires from any traces that have burned up. It looks like some are completely gone.

[BassRepair]

That's no issue. As I mentioned above, I've already run two jumpers replacing those traces. Now to find that damned short.

[Jazz P Bass]

I see a burnt ground trace.
PL1/ middle pin.
That cabling goes to the front panel tone control.
That blue jumper goes to the power transformer center tap which is also ground.

[BassRepair]

I have removed IC4 and IC10.

IC4(7815) with 9V in is reading about 7.4V on the output and is getting hot.

IC10(7915) with 9v is reading .4V on the output.

I'm not sure if I should be using less or more voltage so I just used a fresh 9V battery which reads at about 9.4V.

[Enzo]

OK, several things.

First, a 15v regulator cannot function with only 9v input, it needs over 17v input.

Second, remember a 7815 has leg order in, ground, out. The 7915 had leg order in, out, ground. SO if you are assuming the third leg is output on that 7915, you are actually measuring its ground. Try the center pin.

Further remember the 7915 is a NEGATIVE regulator, so it needs -9v in, not 9v. And remember that means connecting the battery + terminal to the end leg, not center. (And keeping in mind that 9v needs to be twice as much)

If your 7815 Vreg is getting hot, either it is severely overloaded, or it is defective. In my shop, time is money, and I find it a lot faster to sub in a different IC than to spend time testing the existing one. They cost half a dollar, and I charge a dollar a minute labor.

https://www.jameco.com/z/MC7815CTG-O...20_876547.html

SO I would sub in a new part, either that cures it or it lets me know the Vreg is not the issue.

[BassRepair]

OK, several things.

First, a 15v regulator cannot function with only 9v input, it needs over 17v input.

Second, remember a 7815 has leg order in, ground, out. The 7915 had leg order in, out, ground. SO if you are assuming the third leg is output on that 7915, you are actually measuring its ground. Try the center pin.

Further remember the 7915 is a NEGATIVE regulator, so it needs -9v in, not 9v. And remember that means connecting the battery + terminal to the end leg, not center. (And keeping in mind that 9v needs to be twice as much)

If your 7815 Vreg is getting hot, either it is severely overloaded, or it is defective. In my shop, time is money, and I find it a lot faster to sub in a different IC than to spend time testing the existing one. They cost half a dollar, and I charge a dollar a minute labor.

https://www.jameco.com/z/MC7815CTG-O...20_876547.html

SO I would sub in a new part, either that cures it or it lets me know the Vreg is not the issue.

Thanks for the info! I guess I was misreading the tech sheet on those parts. Regardless, I will look at just swapping them out and going from there.

Thanks again and I will update!