Mark embarks on the path of complete WOPLness

MarkWComer said:
I used part of it for the ground to the DC protection board- looks like I screwed up in the wire allocation...

I need to find another 20" of the 18g wire. Should be commonly available, right?
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no pm me your address Mark
 
Well... haven't had much free time, overdue for some video posting.

Bottom row of transistors are in, I don't read any continuity between collectors and chassis ground, but I do read 145kΩ between both collectors of the 21195s and the star ground. Is this good or what did I screw up? Don't have a schematic to show if there's anything between those collectors and ground (I'm sure there must be...).

(Proprietary information anyway...)
A little foggy on some details. Please be precise in your answer because I'm a bonehead:

So- the power chain- variac plugs into wall, DBT plugs into variac, amp plugs into DBT: verify please! (Doesn't make sense to have DBT before the variac...)
This stage is done before the DC protect circuit and control board are installed: verify?
Before the other transistors are installed, check rail voltages and test point values on backplane boards: verify?
DC offset is done with first row of transistors or after all are done?
After all transistors are in and successful powerup, bias is done- but there's a bias TP on backplanes and PL14-20- check both?
 
MarkWComer said:
DAMN that shit's expensive!!!
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Yes - this wire type can be expensive so look around. Joe purchase some and has it available and I have an ass ton of it too. I think you can get a good deal from either of us if you're interested. BTW - I've enjoyed your videos so keep them coming.
 
No need to check both bias points. The control boards came out before the backplanes and Joe being Joe......

I plug the dbt into the variac. You're right about it not making sense otherwise. 145k between collectors and ground is about right. Does that figure climb steadily?

You've checked the power supply and all is well?
 
laatsch55 said:
No need to check both bias points. The control boards came out before the backplanes and Joe being Joe......
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Thinking of the future! Good designer...

laatsch55 said:
I plug the dbt into the variac. You're right about it not making sense otherwise. 145k between collectors and ground is about right. Does that figure climb steadily?
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Yes, the value increases steadily.

laatsch55 said:
You've checked the power supply and all is well?
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Still at the nervous intrepid stage- wanted to verify a coupla things before proceeding.

THANKS!
 
laatsch55 said:
You've checked the power supply and all is well?
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Crap... guess what...

I made all the electrical connections from the backplanes: B+, B-, fused and unfused, before checking power supply. No significant changes have been made to any power supply components from a previously working amp except for removing the caps to make room to work.

Eh... Should be okay...
 
NavLinear said:
BTW - I've enjoyed your videos so keep them coming.
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Editing now, looking for some pictures to insert, cut out a lot of dead space to reduce the playing time. I'm trying to make these short enough to keep attention, but not omit anything important.

The goal is to help people like myself who really don't have a great electronics assembly background do these upgrades successfully without turning their voice coils into flaming projectiles. I put lots of subtitled annotations in these videos to make sure I make specific points as clear as possible.

Are you familiar with the old Bell & Howell 16mm "FilmoSound" movie projectors? There's a failure prone part- a worm gear- that's really complicated to replace. I tried to do a series on those, but was stuck with Windows MovieMaker at the time. PIA! Using iMove on a Macintosh now- so much easier.
 
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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.
 
laatsch55 said:
The bass is the reason I didn't keep the amp. It exhibits less control over the lows compared to a WOPL...I guess I'm just spoilt...
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I owned the POA2200 and 2400 which were basically the same amps just older models of the same design. And while well built (toroidal transformer, nearly complete dual channel layout) reliable amps, with crazy good looking specs: s/n ratio over 125 Db, slew rate or rise time >500 micro seconds, super wide frequency response, they just didn't sound that remarkable.
 
Gibsonian said:
...they just didn't sound that remarkable.
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laatsch55 said:
Amen Scott, that was my basic assessement....
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Well, not to knock a generous lottery win, but yeah- but why is that so? Why do amps sound so different? It's supposed to increase a small current to a much larger one without altering the waveforms- and that's all it's supposed to do! Believe it or not, the old Realistic STA-2300 I had feeding my A|D|S L-1290s sounded superb to me- and it was a mutt-brand Radio Shack goober.

In the meantime, the Denon is a reasonably good stand-in during the last stage of WOPLification of the PL400, so I'm at least not completely tuneless for the duration. To coin a new term, it works imperfectly fine...
 
Still a few quandaries over the wiring...

Run my AC wires on top: But this is a Series II with sensitivity controls on the front panel! The input signal wires run from the input jacks up to the wire harness to a pair of pots, and then go to control board inputs. Hmmm... There's an AC supply from the rectifier to the Watts Abundant board that runs on top. Will I get a 60Hz hum when the cabinet is screwed together and speakers connected?

<iframe width="420" height="315" src="https://www.youtube.com/embed/OuCDgTDRoyc" frameborder="0" allowfullscreen></iframe>

Additionally: This cable run defies the "unified ground." Ground for signal input via the backplane boards, and also ground for the shielding of the run to the sensitivity controls seems to be in conflict.

Meter wiring error: Well, DAMN! Every other ground wire is white, why should there be this one exception? I looked at the extracted electronic point-to-point skeleton and saw that the white wire is for signal to the left output meter! Caught in time- good thing.
 
Yes Mark
PL violated their normally white ground scheme when they connect the meter works. This has been violated on the Series 1 amps with analog meters too.

On on your AC run along the top, that is the best place for them. DO NOT TYWRAP THE SIGNAL INPUT WIRES TO THESE AC WIRES. Rather TYWRAP the AC wires together and keep close to the chassis bend. TYWRAP the signal runs and form them to exit directly toward the front panel and then down to the controls.

Got it?
 
Gepetto said:
On on your AC run along the top, that is the best place for them. DO NOT TYWRAP THE SIGNAL INPUT WIRES TO THESE AC WIRES. Rather TYWRAP the AC wires together and keep close to the chassis bend. TYWRAP the signal runs and form them to exit directly toward the front panel and then down to the controls.

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

Gepetto said:
Yes Mark
PL violated their normally white ground scheme when they connect the meter works. This has been violated on the Series 1 amps with analog meters too.
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White for left and red for right still follows convention, though- but you shouldn't have two conventions in the same resort.
 
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