Help repairing Ampeg 1540 Crossover

[J M Fahey]

Hi, I have this dead Ampeg 1540 crossover , the one in the "fridge size" box with 1x15"/4 ohm spk and 4x10" + Horn ; which can be biamped (2 x 4 ohm separate inputs) or run full range (two parallel 8 ohm input/link jacks)
It´s been messed up beyond repair, no pad switch, missing pads, rusty worn jacks, the works, but the components themselves (power resistors, capacitor, coil, even the lamp) are healthy.
If I can have the Xover schematic I can draw, etch and build a new board using available switching jacks and those old components.
Thanks.

[Enzo]

Here you go. I can make a gray scale copy if this is too dark.

[J M Fahey]

Hi Enzo, thanks a lot.
Can´t believe it, I thought : "well, I´ll check in a week or so ....", but you answered in 26 minutes !!!! (twenty-six, no kidding).
And that includes searching your undoubtedly vast library, scanning and posting exactly what´s needed.
The scan is fine, I just needed the schematic.
Although relatively simple, tracing it "from the board" was very frustrating, because the complex switching: in/out , series/parallel, joining/separating grounds, etc. was made through unreliable cracked rusty contacts, and, besides, I can´t get those same jacks in Argentina, so the next best solution was making a new board using pin-incompatible plastic "Marshall jacks".
The 6-pin connector pinout wasn´t clear either, because the cabinet is unavailable for me to test (long story).
Again, thanks a lot.

[Enzo]

26 minutes? Darn, I'll try harder next time.

[brash]

Any ideas how I can just straight wire the 4 10's and one 15 straight at 4 ohms?

Thanks,
Jeff

[Enzo]

I can think of no way to wire five drivers for 4 ohm total. At least not if the drivers are of common impedances like 4 ohms or 8 ohms.

[52 Bill]

Originally Posted by Enzo

I can think of no way to wire five drivers for 4 ohm total. At least not if the drivers are of common impedances like 4 ohms or 8 ohms.

If the four 10's are 8 ohms, series parallel them to give you 8 ohms, then parallel them with a single 8 ohm 15 inch.

[Enzo]

Duh...

Having a senior moment, I guess.


You are right, but the speakers would then not share power equally. I was trying to come up with some way they would see equal power. But I guess that arrangement would electrcally be the same as a 4x10 cab and a 1x15 cab stacked.

His drivers are already 4 ohms though. Can;t get 4 ohms from five 4 ohm drivers.