Mark embarks on the path of complete WOPLness

[Gepetto]

Embarrassed- what an easy and obvious fix. Told you I was a bonehead!



White for left and red for right still follows convention, though- but you shouldn't have two conventions in the same resort.

The other recommendation is to always closely pair an AC run parallel with its associated return wire

 

[MarkWComer]

Great training for taking NOTHING for granted....

I hold that truth to be self-evident!

 

[MarkWComer]

Backplanes mounted and wired, on to the next phase...

Waiting for a capacitor drain resistor to come in the mail from RadioShack.com, then it's on to giving it a little current.

36 minute video, couldn't seem to pare it down to any less- my apologies.

<iframe width="560" height="315" src="https://www.youtube.com/embed/bMgOW11qVa4" frameborder="0" allowfullscreen=""></iframe>

 

[Gepetto]

I see you enjoyed the Heyco pliers Mark

 

[MarkWComer]

I see you enjoyed the Heyco pliers Mark

Never heard of 'em before! Damned expensive little gadget for what it is, too!

 

[laatsch55]

Works a helluva lot better than needle nose...

 

[ksrigg]

So Mark..............How much longer do you think it will be til you can fire up the WOPL? A little testing, and then button her up? I'm ready to hear what you think...and knowing you built her..that is priceless. What speakers do you use?

 

[MarkWComer]

So Mark..............How much longer do you think it will be til you can fire up the WOPL? A little testing, and then button her up? I'm ready to hear what you think...and knowing you built her..that is priceless. What speakers do you use?

Getting anxious myself!

There's not much left to do now, first row of transistors installed, still waiting for my discharge resistors to come in the mail.

Right now I'm dealing with a few family issues, my Brother In Law has an infected foot and can't get around, my nephew just had a toe amputated from diabetic ulceration, so free time has disappeared. Just cut their lawn today (3 acres takes a few minutes). So all that on top of my own ongoing stuff.

The speakers are a pair of ADS L1290 that I bought way back in the mid 1980s, sound good- but I'm also getting the urge to do a DIY project for homebuilt Klipsch LaScalas. I'm playing a few choice well-known LPs through the Denon amp to take note of the sound I'm getting with it in order to make a better comparison to the PL- and I hope to be blown away by it.

I don't want to take too much credit for building myself, though- without Joe's kits and reading the posts of previous upgraders, I wouldn't have the cerebral horsepower to do this. All I've done is follow an instruction sheet with purchased components. Sure, I assembled, but I can't call this a completely 100% DIY job.

 

[Gepetto]

Never heard of 'em before! Damned expensive little gadget for what it is, too!

Maybe the next Phoenix countdown should be for those pesky Heyco pliers

 

[ksrigg]

I saw some #29 going for $9.99 on eBay. Should have bought them in case I get your name for Secret Santa this year, Mark!!! Hell, I may get them just in case......

 

[MarkWComer]

Mark the way you check out your backplane work before you attach the control board is as follows (and I will be adding these bring up instructions to the backplane assembly notes soon):

With the connections to the control board all taped off so they do not short out to anything (both the bottom row of 10 wires and 3 bias connection wires per channel).
Install the bottom row of transistors starting from the transformer, NPN, PNP, NPN, PNP. Remove the one wire to the upper left backplane 6-32 screw by removing the securing nut and floating this wire in the air. Install rail fuses. Check for infinite resistance between chassis ground and the transformer cases. If not debug. (you will get a reading between DC ground bus bar and these cases, you meter will be charging up the bulk caps)
Connect a ~10K resistor between the output and ground test point on each backplane.
Install rail fuses
Bring up on DBT and Variac to 60VAC in on the AC input. Make sure all is good and no smoke is coming out. Measure that you have B+ and B- voltages present at the respective test points and B- at PAD12 and B+ at PAD 11 on each back plane board.

Check that you have 0V at the output test point.

Take the Variac all the way up and repeat.

Next, before doing anything else, power the amp down and fully DISCHARGE the bulk caps using a 1K 2W resistor (any value close to 1K will do) down to a level below 1V.

Then you are good to proceed to the next assembly step if this is all good.

You're a little vague on a couple points here:
Check for infinite resistance between chassis ground and the transformer cases. I have infinite resistance between the "floating wire" and transformer case, but full continuity between the transformer case and the ground screw that this wire connects to. Between the screw and transformer case, I'd fully expect continuity- how could it be otherwise since the screw is connected to an all metal case with a metal transformer bolted onto it?

Measure that you have B+ and B- voltages present at the respective test points and B- at PAD12 and B+ at PAD 1 What voltages am I looking for at these points? Voltages measured against the ground TP on the backplane board, the ground strap, or the connecting screw? Or against pad 11 as positive and pad 12 as negative? (Recognized: these are power supply to the control board...)

Check that you have 0V at the output test point. Again- zero volts at this TP, measured against what as ground?

Do I leave that ground wire disconnected throughout all the test procedures- or do I reconnect it after verifying zero continuity?

 

[laatsch55]

All voltages referenced from chassis ground except voltages taken from test points on the backplanes, then use the backplane groundpoint for reference.

 

[laatsch55]

There's a typo in Joe's instructions. No resistance between TRANSISTOR CASES and ground. Not TRANSFORMER CASES and ground. The transformer case is grounded so no sense in that...

The transistor cases in question being the outputs...

 

[laatsch55]

B+,B- are rail voltages, so 80 volts +/-

 

[MarkWComer]

All voltages referenced from chassis ground except voltages taken from test points on the backplanes, then use the backplane groundpoint for reference.

OK- That makes sense. Output measures 0v against the ground TP on the backplane, B-/B+ measured against the chassis ground.

There's a typo in Joe's instructions. No resistance between TRANSISTOR CASES and ground. Not TRANSFORMER CASES and ground. The transformer case is grounded so no sense in that...

The transistor cases in question being the outputs...

Ahh.. transistor cases! Y'know- that saves me from doing the vodka and razorblade tango! You can't have metal-to-metal contact with zero continuity...

B+,B- are rail voltages, so 80 volts +/-

-80/+80 is measured, of course, after the variac is up to 120VAC.

Still: What voltages am I looking for at pad 11/12? Whatever I get will be what I get- there's no pot for adjustment, and these are the power supply for the control board.

 

[laatsch55]

Pad11/Pad 12 are rail voltage...80

 

[MarkWComer]

Pad11/Pad 12 are rail voltage...80

English makes absolutely no sense at all sometimes...

When do I reconnect the lug to the ground stud?

 

[laatsch55]

Anytime after doing power supply checks, which is what you just did...you are now ready for the control board..

 

[MarkWComer]

Anytime after doing power supply checks, which is what you just did...you are now ready for the control board..

Don't jump my gun! I haven't done the power supply checks yet- I needed to clarify these steps first. I won't attach the control board until after all transistors pass the PS check, then it's on to bias and checking offset voltage with the control board connected.

Collectors (transistor cases) show no continuity, BTW. At least not in this first row of transistors. I expect that none of them will. VOM also shows continuity between the columns of collector connections, resistance between rows (this is to be expected, of course).

 

[laatsch55]

Yep. I would not install anymore outputs until I had the control board installed. With one row of outputs installed it's easier to chase control board wiring problems if need be. After the power supply and the backplanes check good I would install the control board, set bias, check DC offset then continue with installing rows of outputs.