Power switch mod?

[MusicSteve]

How did you build it?

I posted it on Genes Thread Lol.
I did Modify the Board I increase the resistance of Thermistor Resistor NTCI to Make it go slower until its full on. I started using Ailexpress since I started having problems w E-bay.
I bought this one because they were about the same prices so why not buy the higher wattage one.
https://www.aliexpress.com/item/2251832708166686.html?spm=a2g0o.cart.0.0.6de138danxsSyM&mp=1

 

[MusicSteve]

My off on Switch (typical)
but is hooked to a Power strip, My whole system turns on w the Denon AVR
Other option are w Remote control (Current is a factory)

 

[Oldskoolfan]

did you power up???

Not till a tech goes through it first. I don't have the test equipment to do it right.

 

[mlucitt]

I bought this one because they were about the same prices so why not buy the higher wattage one.

And it has a lightning arrestor Gas Discharge Tube (GDT)!

Funny how we all think alike sometimes.

 

[MusicSteve]

And it has a lightning arrestor Gas Discharge Tube (GDT)!
View attachment 68853
Funny how we all think alike sometimes.

Is that good or bad?

 

[Oldskoolfan]

I posted it on Genes Thread Lol.
I did Modify the Board I increase the resistance of Thermistor Resistor NTCI to Make it go slower until its full on. I started using Ailexpress since I started having problems w E-bay.
I bought this one because they were about the same prices so why not buy the higher wattage one.
https://www.aliexpress.com/item/2251832708166686.html?spm=a2g0o.cart.0.0.6de138danxsSyM&mp=1

I ordered the soft start board. Got it from Ali express. Ebay wanted twice the price.

 

[mlucitt]

Is that good or bad?

Those GDTs are what we use in our HAM radio antennas and switch boxes. The tubes have a small gap surrounded by an ionizing plasma gas. The tubes are connected to the protected line and ground. If a strong enough voltage spike (think lightning) hits the line, the gas ionizes and creates a conduction path across the gap, shorting the voltage to ground or through a resistor. As soon as the voltage decreases, the gas goes back to its original state and the tube no longer conducts.
They are good for a few shots, but easily replaced after they do their job.
To have one in a Soft Start Board is a bonus. It may never get used, but it is nice to know its there.

 

[wattsabundant]

I developed a triac board for the 700's that is controlled by the original power switch. The goal was to preserve the original power switch in the 700B's which are near unobtanium. In the development process I captured a lot of inrush currents at turn on. Typical peak current during the first cycle was 100-125 amps. The highest recorded current was just shy of 150 amps. Downside? The triac has about a 1 volt drop across it which reduces output power at least a couple watts. Upside? never worry about failed power switch.

 

[VSAT88]

Yes, I really liked the triac idea. Came close to putting that mod to use on my Kenwood KR 9600 when I built it. Was gonna go back in and try it but someone wanted it worse than I. That was a beautiful unit and had a wonderful sound.

 

[Vintage 700b]

I developed a triac board for the 700's that is controlled by the original power switch. The goal was to preserve the original power switch in the 700B's which are near unobtanium. In the development process I captured a lot of inrush currents at turn on. Typical peak current during the first cycle was 100-125 amps. The highest recorded current was just shy of 150 amps. Downside? The triac has about a 1 volt drop across it which reduces output power at least a couple watts. Upside? never worry about failed power switch.

I highly recommend Don's Triac Board. I built all 3 of my 700b's with one, and they are straightforward, neat installations.
After installing the first one, I wouldn't build the others without it. Like the OutPut Relay Speaker Protect board Don sells, it flat out works.

 

[laatsch55]

And it's quiet. Before Don sold any, I put one on my 700 and measured noise....it was actually quieter with the triac than without....

 

[VSAT88]

WOPL 700 is what like 1000 watts? Don said it reduces the output power about two watts or so? Man you talk about a deal breaker now I would only have a 998 watt amp. Lol. Triac sounds like a damn good way to go.

 

[Oldskoolfan]

I forgot about my thread on my first PL400 so I'll update.
Had it evaluated before any mods. Tech gave it a clean bill of health. Minor offset adjustments and away we went.
First two steps were transformer isolation and power cap replacement. All went well except I missed the nylon washers between the transformer and aluminum cap support.
Next was Don's DCP board...piece of cake. After that, replaced all output transistors and drivers. Recapped the control board. Back to the shop for testing. No hiccups, no clipping till 220 watts on the o'scope. Max output 225/228 watts into 8 ohms. Me so happy! Got it home and gave it a real world test. Powered up a pair of SM 155's and put on Al Stewart's "Year of the Cat". I couldn't get over 20 watts. The music was so loud and clear and full! The sax was absolutely clean with no distortion.
I have since added Joe's LED light mod. Ordered a rotary selector switch so I can mount it to the faceplate to select meter sensitivity.
I've since bought another 400 in desperate need of TLC. It's been previously hacked on. 4 different types of output trans. Only 1 column isn't mismatched.
The control board is just...scary. magic smoke leaked out of it at least once. Not gonna play, that gets the WO treatment. Gonna try and squeeze a backplane in the budget too if I can.
BTW, anybody know if it's possible to get a faceplate repainted or maybe laser etched....
...I'm addicted, ain't I?

 

[gene french]

I forgot about my thread on my first PL400 so I'll update.
Had it evaluated before any mods. Tech gave it a clean bill of health. Minor offset adjustments and away we went.
First two steps were transformer isolation and power cap replacement. All went well except I missed the nylon washers between the transformer and aluminum cap support.
Next was Don's DCP board...piece of cake. After that, replaced all output transistors and drivers. Recapped the control board. Back to the shop for testing. No hiccups, no clipping till 220 watts on the o'scope. Max output 225/228 watts into 8 ohms. Me so happy! Got it home and gave it a real world test. Powered up a pair of SM 155's and put on Al Stewart's "Year of the Cat". I couldn't get over 20 watts. The music was so loud and clear and full! The sax was absolutely clean with no distortion.
I have since added Joe's LED light mod. Ordered a rotary selector switch so I can mount it to the faceplate to select meter sensitivity.
I've since bought another 400 in desperate need of TLC. It's been previously hacked on. 4 different types of output trans. Only 1 column isn't mismatched.
The control board is just...scary. magic smoke leaked out of it at least once. Not gonna play, that gets the WO treatment. Gonna try and squeeze a backplane in the budget too if I can.
BTW, anybody know if it's possible to get a faceplate repainted or maybe laser etched....
...I'm addicted, ain't I?

you have no idea...
lol

 

[J!m]

I think Joe has replacement face plates… maybe WOPL sniffer too/instead?

 

[George S.]

Cool! 400 WOPLs are amazing machines. Joe has this all figured out. Check his WOAD website for faceplates.

 

[George S.]

https://forums.phxaudiotape.com/threads/thicker-pl400-faceplate-with-new-analog-meters.10834/

 

[mlucitt]

Old School,
You think the PL400 with the original control board sounded good? Wait until you hear a PL400 with the WOA Rev G1 Control Board! Adding the Backplane Board Kit moves it up another notch.
You have stepped upon the slippery slope.

 

[Oldskoolfan]

CALLING DON!!!! Found a thread on that site which shall remain nameless about using a triac for power switching. Then I get back to this thread and find that Don has developed a triac board for the 700.
So Don, have you got one (or three) that can go in a 400? Seems that would make installing a switch mod MUCH easier.

 

[VSAT88]

You talking about that Kenwood KR-9600 thread over at Audiokarma? I read through that whole thread when I restored my 9600. They showed how to do the triac trick. That was the only part of that thread I didn't do. Knowing I was selling it at the time I said fuck it. No need going any further. That was one bad ass unit.