WOPL 400 Build

laatsch55 said:
Mounting the outputs does get tedious doesn't it??
Click to expand...

Yes, but when they click in place, it sure is satisfying.

2nd row in and tested. I think I may be listening to some music tomorrow!
 
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Fantastic graph, But just to clarify the blue trace of voltage is 10v per division ? .... Am I reading 15 V ? Is the probe set @ -10 ?
Im relatively new to the scope setup....

M
 
Mohawk said:
Fantastic graph, But just to clarify the blue trace of voltage is 10v per division ? .... Am I reading 15 V ? Is the probe set @ -10 ?
Im relatively new to the scope setup....

M
Click to expand...
The voltage trace was taken with a 10:1 probe so it is actually 100V/division. When I captured the image the scope was fresh out of the box and I hadn't learned how to set up probes yet. For $350 this 4 channel storage scope is a bargain. However I don't like it for looking at audio waveforms as the trace is to fat. Consequently I still have an analog scope for that. Also, anybody who wants to try looking at line voltages should be using isolated probes.
 
And I just managed to snap a lead on one of the transistors on the control board while trying to straighten it after bumping. It's labeled MPS A42 E27. Not real pleased with myself...
 
You are not the first to do that. Cut the leads and remove one at a time...
 
wattsabundant said:
The AGC fuse protects the transformer and bridge rectifier. The smallest fuse that doesn't blow due to inrush current would be fine.

I have inserted a scope photo of the inrush current on a 700II. A 700B would be the same. The amp has 15,000uf caps. The yellow trace is the current at 50A/division. The bluish one is input voltage. Notice how the input voltage collapses at turn on. The peak current on the first cycle is just short of 150A. The voltage recovers after about 4 cycles. Now, is there any question why the switch could fail?

View attachment 40793
Click to expand...
This represents 1/5 second...

Re: The yellow trace. With 15,000µf caps, is the ripple eventually eliminated completely, or is there any residual?
 
MarkWComer said:
This represents 1/5 second...

Re: The yellow trace. With 15,000µf caps, is the ripple eventually eliminated completely, or is there any residual?
Click to expand...
When the load goes up, the current ripple peaks will reappear. Load dependent. The caps are charged in a matter of ~64msec upon power up (about 4 line cycles)
 
All output transistors are in and tested. I just need to do that repair and attach the front wires. Tuesday can't come fast enough!

Does the short black cable from the front panel go to the ground? That's what it looks like it goes to, but I want to double check.
 
If it’s the ground for the power to the LED meters, it should attach to the copper bus. Check near your input jacks, too- originally there was a bus wire connecting to the chassis, remove it. There should be ONLY ONE chassis ground, a wire from the copper bus to a ring terminal to the top stud protruding through the left backplane board.
 
Any thoughts on using inrush current limiters, say 20 amp limiters? Could soften the blow to the switch & transformer. It'll drag out the time until those caps are charged, but I don't see an issue with that. Also, how about a zero crossing detector for turn-on? Might help to suppress the arc across the switch.
 
MarkWComer said:
Good idea, but I’d rather see a higher voltage rating. 125v is probably good enough, but I wonder if a power surge from a lightning storm would overpower it.
Click to expand...
I thought the same thing, and sure enough, they make one rated at 250VAC/600VDC, see here:
https://www.mouser.com/ProductDetai...OuLeU%2BQv17kdzKETcwFlKKKjZztZZnWBoPYez0xBQ==

But the one, above, rated at 250VAC does not comply with UL1414/CSA-C22.2 No. 1. Meaning is is not suitable for use "across the line" applications. I have never read those references, but I will download them and read them the next time I am suffering from acute insomnia.

With reference to a power surge from a lightning storm - From articles in Windpower Engineering & Development, we learn that lightning bolts carry from 5 kA to 200 kA and voltages vary from 40 kV to 120 kV. The outcome also is unpredictable—a strike that occurs a mile away can generate 70 V in electrical cables, and another can generate 10 kV from 160 yards away. So, no device can protect our precious audio devices from a direct or indirect hit.

The real purpose of these "Quencharc" devices is to protect the contacts of the power switch (or relay) from arcs, sparks, and transients to extend the operating life of these devices. If you are looking for protection from power surges, that is a different product. These come to mind:
https://www.bestbuy.com/site/audioq...rotector-black-silver/6320328.p?skuId=6320328

or,

https://www.techhive.com/article/3281455/apc-surgearrest-performance-p12u2-review.html

Finally, you can add the optimum surge protection inside the equipment yourself by installing (3) 130VAC Metal-Oxide Varistor (MOV) sacrificial devices across the AC lines, (1) from Line to Neutral, (1) from Neutral to Ground, and (1) from Line to Ground. These are good and new:
https://www.mouser.com/ProductDetai...=sGAEpiMZZMuQmL5N8IqpX5jFkXwxQwBHR4M7hA/ej5U=

or
https://www.mouser.com/ProductDetai...GAEpiMZZMuQmL5N8IqpX5jFkXwxQwBHlHxvukv%2BFo8=

Sorry for the long-winded explanation...
 
mlucitt said:
I thought the same thing, and sure enough, they make one rated at 250VAC/600VDC, see here:
https://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/254M06QD150?qs=/ha2pyFaduiT2OuLeU%2BQv17kdzKETcwFlKKKjZztZZnWBoPYez0xBQ==

But the one, above, rated at 250VAC does not comply with UL1414/CSA-C22.2 No. 1. Meaning is is not suitable for use "across the line" applications. I have never read those references, but I will download them and read them the next time I am suffering from acute insomnia.

With reference to a power surge from a lightning storm - From articles in Windpower Engineering & Development, we learn that lightning bolts carry from 5 kA to 200 kA and voltages vary from 40 kV to 120 kV. The outcome also is unpredictable—a strike that occurs a mile away can generate 70 V in electrical cables, and another can generate 10 kV from 160 yards away. So, no device can protect our precious audio devices from a direct or indirect hit.

The real purpose of these "Quencharc" devices is to protect the contacts of the power switch (or relay) from arcs, sparks, and transients to extend the operating life of these devices. If you are looking for protection from power surges, that is a different product. These come to mind:
https://www.bestbuy.com/site/audioq...rotector-black-silver/6320328.p?skuId=6320328

or,

https://www.techhive.com/article/3281455/apc-surgearrest-performance-p12u2-review.html

Finally, you can add the optimum surge protection inside the equipment yourself by installing (3) 130VAC Metal-Oxide Varistor (MOV) sacrificial devices across the AC lines, (1) from Line to Neutral, (1) from Neutral to Ground, and (1) from Line to Ground. These are good and new:
https://www.mouser.com/ProductDetail/Bourns/GMOV-20D131K?qs=sGAEpiMZZMuQmL5N8IqpX5jFkXwxQwBHR4M7hA/ej5U=

or
https://www.mouser.com/ProductDetail/Bourns/GMOV-14D131K?qs=sGAEpiMZZMuQmL5N8IqpX5jFkXwxQwBHlHxvukv%2BFo8=

Sorry for the long-winded explanation...
Click to expand...
Put a big ass MOV across the line - neutral.
 
And then it's a crapshoot. I've had lightning literally blow up100hp pump panels. Lightning is a bassaaaaaaaad mo fo...
 
laatsch55 said:
And then it's a crapshoot. I've had lightning literally blow up100hp pump panels. Lightning is a bassaaaaaaaad mo fo...
Click to expand...
Yes it is Lee. Nothing can really protect against a lightning strike of any real magnitude.
 
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