testing a crossover

Are you measuring the resistance across IP- and IP+ on the PCB? It looks to me like IP+ routes to two resistors (2.2Ω and 3.3Ω), there's lots of clearance between the tracks and no obvious short. So even if there were a problem further down the line you'd expect to see at least 1.3Ω across the inputs. It's rare for resistors to fail closed circuit so I wouldn't go looking there just yet.
The 2.2Ω is in series with the 12µ cap which will block DC, I can't work out what the 3.3Ω connects to under that big cap, but I still can't see how there'd be 0Ω across IP- & IP+. I'm sure I'm missing something.
I can see fibres on the PCB conductors but assume they're hot glue or stuffing material. Even so I'd start by cleaning up the copper connected to IP- & IP+ and measuring the resistance across those if you haven't done so already. I'd also check the multimeter by measuring a known value e.g. a resistor that's out of circuit. You wouldn't believe the number hours I've wasted going down a rabbit hole only to find I've measured something wrong or missed something obvious.

I'm sure you'll get there in the end with the help of some others here... good luck.

fiesta75 and imhififan are on the money with their advice... but I'd hold fire with the soldering iron until you've got a little more to go on.
IP+ and IP- should be open circuit at DC (OL), although you may need to leave the probes in place a few seconds while the caps charge.
If you're still getting 0Ω across IP+ & IP- then it's most likely a short somewhere between the input terminals and the copper pours that sit directly under IP+ & IP- on the PCB, you should be able to check this visually.
If that doesn't turn up anything then it might be time to reach for the iron.

Yup, I don't disagree and that's good advice. I'm mainly interested to see what the cause is... it's a weird one.

I can guess, but that would be uncalled for and premature

Is that in response to me?.. don't know what you mean. Only point I was trying to make is if you change lots of things at the same time sometimes it's difficult to know what the original problem was and so you learn nothing along the way.

resistance between IP POS And IP neg  -OL

Okay, so that checks out... as long as when you put the whole lot back together you still get open circuit at DC across the HF/Mid posts all is as it should be and there's no DC load on your amp.

mid speaker cable going to driver,dead short.no driver connected

Actually looking again you should be getting around 2.2Ω across the Mid driver outputs. I'd look at the photos again, but they're not there any more. The area to inspect is the bottom half of the board when orientated like the schematic.

between mid pos and neg 2.7 ohms

Okay... before you said that you were getting 0Ω across the MF +/- outputs with the driver disconnected. Is this the same measurement? If it is then it's close enough not to worry about for this exercise. As imhififan said:

The MF measurement should equal to the DC resistance of the 2.5mH inductor + 2.2Ω.".

Take into account there's a bit of tolerance on those resistors as well as the accuracy of your meter.

Not sure what 0.22mH is and also 2.5mH inductor +2.2 ohms,i know what the inductors are but not sure on mH.

Although the inductors will have some DC resistance you can pretty much ignore it for the purposes of this excercise as long as you're in the ball park of the resistor values.

Also i have found that one of the capacitors has a dead short short when tested in dioode mode,{still soldered into pcb},on both x-overs, when the rest show OL,not sure if that has a bearing on anything, just throwing it out there.

If that's the 6µF cap then the reading is correct as it's in parallel with the 2.5µH inductor which will have very low resistance at DC.

If I've understood you correctly then the tests don't seem to have turned up any results that would cause the amplifier to fail.
Maybe someone else will spot something I've missed... or maybe the tech didn't find the real fault in the amp when it was sent in the first time.

Okay... I think I am having trouble following. Also there might be a bit of confusion around resistance (DC) and impedance (AC). When you read the resistance across the loudspeaker terminals it has very little to do with the nominal impedance of the speakers (this is even true if you measure across the driver itself). You have a high pass filter on both the mid (12µF) and the tweeter (4.2µF) so if everything is working correctly you should get an open circuit when you attempt to measure resistance across the loudspeaker posts with everything connected.

I’ll tell you what I think I’ve understood and you put me right if I’ve misunderstood:

1) Original test with everything assembled showed 0Ω resistance across the MF/HF +/- terminals on the back of the speaker.
2) Those terminals connect directly to IP+ and IP- on the crossover PCB.
3) With the crossover disconnected the DC resistance between IP+ and IP- was open circuit.
If points 1-3 are correct and you’ve put it back together and measured 0Ω across the loudspeaker terminals then there’s a short somewhere between the terminals and where the wires connect to IP+ and IP-.

4) With everything disconnected from the crossover you measured the resistance across the copper you have marked M+ and M- and got 0Ω.
5) According to the schematic M+ and M- should be connected (at DC) via 2.5µH inductor (of negligible DC resistance) and a 2.2Ω resistor.
6) On your most recent test you measured 2.7Ω.
If point 4 was true then you’d most certainly have overloaded your amp and would have got no sound from the driver... however the most recent measurement shows no such problem.

between the HF+ and LF+ terminals should be 0.0 ohms

do you mean open circuit?.. Not being snarky, just checking :-).

You have made me think of something though... if you forgot to take the shorting plate/wires off the loudspeaker posts when switching to a bi-amp config you could get enough current flowing between the two amplifiers to blow one of them.

@erik_squires 

Dude, you should have followed my advice and you'd be done by now. :)

The best way I know of to test a crossover is to generate an impedance graph. You can use DATS V2 (or is it now up to V3) or you can build a jig and use Room EQ Wizard’s app for this.

How is that advice?.. it's not going to help anyone who doesn't already know what they're doing.

ps was that pragmasi or eric which posted the equation post ?

That was me re-posting Eric's advice to point out how it wasn't very helpful.

Pragmasi-im really sorry,but there are no open circuits

Absolutely nothing to be sorry about at all... would just be good if we could help you fix this.

shorting links on speaker binding post havent ever been used,to go from bi-wire to normal two wire

Shame... thought I was onto something there... how do you connect the terminals when running from one amplifier?

It'd be useful if you could describe where you're measuring the short circuits using the references you've added to the PCB with a sharpie.

Would be great if we could all help you get to the bottom of this.

1) Original test with everything assembled showed 0Ω resistance across the MF/HF +/- terminals on the back of the speaker.
2) Those terminals connect directly to IP+ and IP- on the crossover PCB.
3) With the crossover disconnected the DC resistance between IP+ and IP- was open circuit.
If points 1-3 are correct and you’ve put it back together and measured 0Ω across the loudspeaker terminals then there’s a short somewhere between the terminals and where the wires connect to IP+ and IP-.

totally correct

Okay, that should narrow it down a bit and you can stop worrying about the crossover. If you only get the short when the loudspeaker is reassembled then you're looking for something between the crossover PCB and the loudspeaker inputs. If you disconnect the crossover you should be able to track it down... what are the binding posts on the loudspeaker mounted to, plastic or could it be anodized aluminium?

If you measure the resistance across the loudspeaker posts which include connection to the bass driver (or full range) then you will measure some resistance that is greater than 0Ω which is made up of the crossover components and the voice coil resistance of the bass driver only. You are not measuring the impedance of the loudspeaker, in fact an impedance measurement doesn't mean anything unless you know the frequency you are measuring at.

In your configuration you should see open circuit for MF/HF and some resistance across LF. Which you do when the crossover is disconnected from the speaker terminals.
If I understand you correctly it is only when you put the loudspeaker back together that you read 0Ω across the MF/HF. If that is correct then you have a short which is upstream of the crossover i.e. the loudspeaker terminals, connecting wires etc.
If the MF/HF connectors really are a dead short then your amplifier would fail immediately... actually it should go into overcurrent protection but I digress.

Something doesn't add up.

1) You measure 0Ω across the MF/HF terminals of both speakers.

2) When you had everything disconnected you measured open circuit across IP+ & IP-. That is what you would expect.

Knowing that, it should be simple with the crossover disconnected to measure the resistance across the loudspeaker terminals to locate the short. If there's not one then the short was either at the point the wires connected to the crossover or items 1 & 2 listed above are incorrect.

The fact that both speakers measure 0Ω at the MF/HF terminals implies that you're not looking for a stray wire or small solder bridge but a mistake or failure on both speaker inputs. That's why something like connecting the amplifier outputs incorrectly seemed like a likely scenario... although I know you've ruled that out.