PL700 Series II Lessons Learned

mlucitt

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#1
My first foray into a complete rebuild of a PL700 Series II was quite a learning experience, I have been a PL700B guy until now. This rebuild included a new chassis, 120V/240V selector switch, WOA Backplane Kits, WOA Control Board Kit, WOA Cylon LED Board Kits, WOA bulk capacitors, new power switch, and DC Protect Board including new input and output connectors.

I learned you can put a heatsink in upside down and the amp will still pass a bias test:
Upside Down Heatsink.jpg

I learned not to test the temperature of the output devices with your hand if you touch two rows at a time:
Ouch Voltage.jpg

I learned not to let my 250 Watt soldering iron get too close to the bulk capacitors:
PL700 Cap Burn.jpg

But, I also learned that when I applied power for the first time, the initial bias value was 335mV and it was an easy adjust to get to 350mV, the DC offset was 0.000V, and the Cylon LEDs need the -100V reference (rail fuses uninstalled) or all the segments will light up very brightly:
PL700 Alive.jpg

Overall, the 80 hours of work on this amplifier were very satisfying. However, hearing some Shpongle at mach 10 made it even more satisfying. They call it "Burning in" but it is really the technician saying "Oh, yeah..."
 
Last edited:

laatsch55

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#3
My first foray into a complete rebuild of a PL700 Series II was quite a learning experience, I have been a PL700B guy until now. This rebuild included a new chassis, 120V/240V selector switch, WOA Backplane Kits, WOA Control Board Kit, WOA Cylon LED Board Kits, WOA bulk capacitors, new power switch, and DC Protect Board including new input and output connectors.

I learned you can put a heatsink in upside down and the amp will still pass a bias test:
View attachment 43618

I learned not to test the temperature of the output devices with your hand if you touch two rows at a time:
View attachment 43619

I learned not to let my 250 Watt soldering iron too close to the bulk capacitors:
View attachment 43620

But, I also learned that when I applied power for the first time, the initial bias value was 335mV and it was an easy adjust to get to 350mV, the DC offset was 0.000V, and the Cylon LEDs need the -100V reference (rail fuses uninstalled) or all the segments will light up very brightly:
View attachment 43621

Overall, the 80 hours of work on this amplifier were very satisfying. However, hearing some Shpongle at mach 10 made it even more satisfying. They call it "Burning in" but it is really the technician saying "Oh, yeah..."

Learned a lot eh??
 

mlucitt

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#4
What pots did you end up deciding on for the level controls?
They were supplied by the customer, sent directly to me from Viet Nam, country of origin listed as Japan; originally cited as being manufactured by TDK, upon receipt I discovered they were actually made by TKD. They fit the chassis because I provided minimum clearance dimensions to the customer. They are stepped attenuators. Specification sheet attached.
Model P-2511S (50db 100K Ohm Audio taper). 6mm shafts, so they require replacement knobs. Actually, not too bad, don't know how they'll last.
Anyone need some perfectly good Phase Linear OEM 100K potentiometers???
 

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wattsabundant

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#5
...and if the gator clips make contact to the chassis while still on the output screws there will be a substantial arc flash. If you got across 200 VDC you're lucky to be alive.
 

Vynuladikt

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#7
It was a one-handed slip maneuver, and it didn't tingle. More like a circular saw was cutting through my hand.
Yep, 120 from the outlet will bite ya hard but 200 hits you like a sledgehammer. Don't ever let it be from one hand to the other. That can end it all very quickly.
 

mlucitt

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#9
This was 200 VDC. Had it been hand to hand there would have been a funeral.
Always keep one hand in my pocket when checking these babies, the USN taught me that trick. 216.9 VDC actually. Anyone have some output transistor covers for PL400 or PL700? I have learned you only need to cover two rows (the positive rails or the negative rails) in order to avoid the shock.
 

WOPL Sniffer

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#13
I don't use them because they hold in the heat. It's easier to keep your hands out of the back of the amp while it's in use. This is akin to working on your car while it's running. Work SMARTER, not harder
 

Wheel-right

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Man, Ya shoulda been here yesterday
#17
Wondering why a person wants to feel up his amp while its being used. Many ways to get off but that ain't one I'm interested in...
 
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