Jer's PLWO to be... (Jer vs the 700, Round 2... it's "Personal" this time)

[Skratch]

Makes one hell of a noise

 

[jbeckva]

Yea it does! Well, off to the shack I guess. Getting some wirewounds, alligators, and a new (bleep)'in meter.. Looks like the one I've had for 15 years or so finally bit the big one.

 

[mlucitt]

Cut an old test lead in half, one with a clip on one end. The other end can be 1/2" of bare wire. Solder in a 1-5 Watt 25 Ohm resistor and wrap it in heat shrink. Make this a religion every time before you reach in and you won't get those "pops". It has saved me a few times. Oh make sure power is off or that resistor will let you know all about it. Lee, how many times has discharging produced a small spark for you (meaning enough current to kill you)?

 

[jbeckva]

Yep, got a couple of 50 ohm 10 watt wirewounds. They will definitely come in "handy" (as in... saving my hand from being charred off hehe)

 

[laatsch55]

Cut an old test lead in half, one with a clip on one end. The other end can be 1/2" of bare wire. Solder in a 1-5 Watt 25 Ohm resistor and wrap it in heat shrink. Make this a religion every time before you reach in and you won't get those "pops". It has saved me a few times. Oh make sure power is off or that resistor will let you know all about it. Lee, how many times has discharging produced a small spark for you (meaning enough current to kill you)?

Every time and that has been a nemisis of mine.The bleed resistor I use is 75 ohm 10 watt. If you turn it on with the resistor hooked up it will smoke in 2.8 seconds, yep, done it enough to have timed it.
And another thing. I was putting in the .33 uf 100 volt mylars on the backwall one day and had the power switch "OFF" but the wire going to the Thermodiscs was not on the "Open" side. Shorted the minus rail to the AC in........Wasn't pretty.

 

[laatsch55]

Makes one hell of a noise

It got soooooo bad here one night Jani thought I had taken a .38 Special and discharged it in the house, should have seen that girl fly down them stairs, only to find me trying not to laugh, that wasn't pretty either.

 

[jbeckva]

I have an idea for a contest.. the "Sparky Award"...

(I'd probably win too hehe).

Ok, got the bias trannies wired at the transistor ends and have mounted them onto the chassis. It's time for a smoke - next is wiring in the WO board itself!!

AND THEN... !!!

 

[jbeckva]

Board's in... input's hooked up... The last solder joint "done"....

(I better go smoke... )

 

[jbeckva]

Ok, nothing blew up on me .. hehe (whew)..

Offset... 5mv / 5mv

Bias... 400 / 400mv (Seems to run a lil higher than I would expect?).. Is this ok or what can I do to lower it a little bit?

Hookin up some loads and buttoning it up ... yaaah!

 

[laatsch55]

Good Job JER!!!! Let it cook for about 15 minutes then bring thje bias down to 385MV.

 

[jbeckva]

Best I can do is 395? Pot's all the way over CCW

I do still have the XPL's in for drivers... that make a diff?

 

[jbeckva]

Ahh.. checked again.. looks like it's going down a lil bit... let me let 'er burn for a few more mins eh?

 

[mlucitt]

It will run fine at 395mv, maybe a little warm but not bad. Mine did the same thing on one channel and I found the values for R19 and R62 had been switched. But you have it on both channels, unusual. The factory spec is 350mv with the XPL's as outputs, but I would not think having them as drivers would make much of a difference. Do you have any RCA410's?

 

[Gepetto]

What are you using for bias transistors Jer (Q6 location, mounted on the backwall?)

 

[laatsch55]

5088's Joe.

 

[jbeckva]

Running the rca 410's with the xpl's...

Verdict so far... 1K output at clipping.. 488 watts. Not too shabby considerin' the outputs are orig. and the caps are a wee shy...

Time for the FINAL and real test... putting it up and listening!!

 

[jbeckva]

Going to let it sit and cool for another 10 mins first.. then recheck the bias. Should it be "nominal" when idle for that long and it's had a chance to cool down?

 

[jbeckva]

Shit I have goosebumps... jeezus holy moley! Those meters are barely moving too, and it's well good and loud enough.

time to get louder... shponglin' time!!!

 

[jbeckva]

Ow that hurt... heheh

 

[laatsch55]

Ya don't want to set the bias right after a mach 8 demonstration. let it cool then stabilize while idling.