WOPL dual 500

[laatsch55]

Nice work Glen!!

 

[Northwinds]

Man, that looks like a bitch to work on. Looks like a pile of wire piled on a pile of wires

 

[grapplesaw]

Man, that looks like a bitch to work on. Looks like a pile of wire piled on a pile of wires

Gee Ron I thought was pretty clean
Here is what looked like at the start

 

[WOPL Sniffer]

More photos

Damn, your mouser bill for transistors has got to be crazy.

 

[grapplesaw]

So powered it up to low rail voltage - 80v rail or 160v across caps.

no D.C. Offset to speak of, like .05mv on either channel

Bias is screwed up, I will expand below

I ran the amp up the AP to 1 watt output or 2.7 volts. This is hard to get good numbers at this setting but it was the lowest THD+N I have ever seen on any of my amps - please see photos below. I will check the AP settings as it is not set correctly , currently on average

so I did not do anymore than that tonight.

Left bias could only get down to .380 v at full atdjustment and the right could only get any higher than .075 mv max

i will have open it up and check the wiring. Lots of possibilities from resistors , bad solder or bias transistors. I did the revision to the board Joe sent me so I will check out those modifications as well.


edit: left Bias good. Meter set wrong no issue , operator error!!
Right still only .09mv so will check connections for Bias transistor leads screw terminals

 

[NavLinear]

Fantastic job Glen. You have a one of a kind amp - or is that a pair of a one of a kind. The backplane is quite busy but you did a very nice job in getting everything routed well. You'll need to let us know how they sound compared to the upgraded 700s - cool stuff.

 

[grapplesaw]

Fantastic job Glen. You have a one of a kind amp - or is that a pair of a one of a kind. The backplane is quite busy but you did a very nice job in getting everything routed well. You'll need to let us know how they sound compared to the upgraded 700s - cool stuff.

Thank you Dennis. I guess I have looked at it long enough that I can get to any thing easily. I can fold the back plane away from the chassis to get at everything.

 

[grapplesaw]

Right bias is 70mv max with bias transistor in circuit and well over 500mv with it disconnected.

The mistery is I checked both the wiring connection , color code of wires to actual pin out and with my transistor tester on both high and low and checks put ok. Although it test good I will make a new bias transistor assembly and exchange that tonight.

I will I'll check for short on Phoenix connector pins as well. Could be over soldered.

Any ideas anyone?

 

[grapplesaw]

I have removed wire 6 and 7 to Q6 and bias transistor

checked R21 and R20 R9 and R31 all good

Checked D1-D4 all good

voltage is
6.7 at collector
2.5v olts at base
1.4 volts at emitter

somewhere voltage is leaking in close to the collector

more to come

 

[grapplesaw]

I have checked it over. Looks good to me. Please look and see if anything is different between channels

 

[Gepetto]

I have checked it over. Looks good to me. Please look and see if anything is different between channels

Do you have a solder splash between anode of D3R and D2R?? Topside of board.

 

[laatsch55]

I can't see anything bud....

 

[grapplesaw]

Do you have a solder splash between anode of D3R and D2R?? Topside of board.

Thank you Joe

The board is looking Ok for the whole.
the Diodes are not shorted
here is photo front and back

if I remove bootstrap wire 10 on the good channel I get same incorrect voltage. I have verified wire 10 is correctly attached to the back plate and has no resistance between test port on Control board and base wire for outputs. Curios what is going on.

Can the C-18 47uf100v cap be a place to look at ?
i wait you comments.

 

[Gepetto]

I have removed wire 6 and 7 to Q6 and bias transistor

checked R21 and R20 R9 and R31 all good

Checked D1-D4 all good

voltage is
6.7 at collector
2.5v olts at base
1.4 volts at emitter

somewhere voltage is leaking in close to the collector

more to come

Hi Glen
The emitter voltage should be negative if you have 0.000 at the output. Something to check.

Seems like the bottom half is possibly not pulling at all Glen.

 

[grapplesaw]

Hi Glen
The emitter voltage should be negative if you have 0.000 at the output. Something to check.

Seems like the bottom half is possibly not pulling at all Glen.

Ok I will check out the other half. That does seem like a good possibility.
Will report back with better data

 

[Gepetto]

Ok I will check out the other half. That does seem like a good possibility.
Will report back with better data

Seems like the negative side base connection to your lower half of the output totem pole is suspect. Something to check.

 

[laatsch55]

Flyback diode in backwards??

 

[Northwinds]

Gee Ron I thought was pretty clean
Here is what looked like at the start

I meant that that is a lot of stuff packed in. I admire you being able to take this monster and bring it back to life. Maybe someday I will come across one!

 

[grapplesaw]

I meant that that is a lot of stuff packed in. I admire you being able to take this monster and bring it back to life. Maybe someday I will come across one!

Ron your assessment was correct the first time. It is Busy and caused my latest miss adventure.

So Joe nailed it. A bad solder joint. All hail Joe!!

one solder pin joint on the first driver was questionable. As you see from the photo a well hidden spot. Wil resolder of all pins it is running perfectly at this time. We will see what testing does to it.

 

[laatsch55]

Well shit, that only took a day!! Good job Glen!!