PL400 Series 2 problems...maybe

[WOPL Sniffer]

Imaginge your friends surprise when a short time after getting them back from you, they take out his prized speakers or even better, start his kitty kat on fire.

 

[gene french]

i have 2 4 fins that i did complete wopl upgrades...including ps caps and leds...

i have 4 8 fins that have been recapped including ps caps and leds ... but retained the original control boards..

one 4 fin had a pl400c control board...early model...i finally got it up...but after a few months it started giving problems...i wanted a wopl ... so i upgraded it..

i purchased an 8 fin and a parts only 4 fin from a member here...i restored the 8 fin...and added a second wopl as the parts 4 fin was not worth the effort ..looks like lightning hit it...melted traces off the board...marvin knew this one personally...

all but those two were bought from ebay...in various stages of performance and or nonperformance.....it was fun for me to get them up and running...with help here...all are in service except a working spare....i keep a rebuilt pl14 ready for any problems that could arise...so far...no problems with the "stock" units...and my units are played from 8am to 5pm daily...

i was determined not to give up...hang in there...

 

[laatsch55]

So are you saying that you don't know if the Idle current can simply be referenced off of the emitter resistors ?


No..
Hook up each side of the 10 ohm bias resistor on the back wall. Set bias doing that.

 

[wattsabundant]

So I feel like pisssing everybody off by saying it amazes me how something 40 plus years old that's full of junk parts still works. How many TV's and microwave ovens lasted that long. Look at all your high priced gadgets in your drawer that failed after a few years.

I don't question that dropping a chunk of change to do the upgrades has its benefits. For those persons with limited funds there are options. I've seen my fair share of PL14 boards with front end transistors causing 80 VDC on the output and I've fooled around with bias transistors when the bias was too high.

It is possible to change the front end transistors (Q1-Q4) on a PL14 and change out the electrolytics on the board. Change out the electrolyics on a PL 36 board and do the service bulletins. If you run all of the tests in the service manual and don't get to out of control, like when you visit Lee, it will likely hold up until there is cash to do the more expensive upgrades.

I don't care what mods and upgrades are done, if it doesn't get ventilation, it's going to fail if you run it hard. Keep in mid that an amp runs hottest at half of it's rated output. A couple 12 volt 4" muffin fans pointed at the heatsinks can make a difference. Wire two of them in series so they run at half their rated DC voltage and they'll be quiet and help with thermal stability.

 

[laatsch55]

LOL!!!!!!

 

[wattsabundant]

Imaginge your friends surprise when a short time after getting them back from you, they take out his prized speakers or even better, start his kitty kat on fire.

If I recall correctly there is a speaker protection circuit to help prevent speaker damage should an amp fail. Somebody sells a custom version for 400's and 700's on EBAY. I think Sniff uses a similar one on his 700's. As for the cat, I hope the covers are installed over the exposed outputs. Same for inquisitive kids.

 

[J!m]

If you can’t swing a proper rebuild there are many options.
One is to trawl eBay for a low cost mosfet amp that sounds decent. Hafler made a bunch for example.

Then sell the PL junk and probably have money left over for fresh zip cord.

It’s like building a drag car and complaining about fuel costs… if you wanna play, you gotta pay.

 

[gene french]

some of you guys are very harsh and super critical of a fellow member that simply wants his original 400 repaired and or recapped using stock boards...
really dont understand why...i thought this was a vintage audio support forum...
i dont think there are any rolls royce or Bentley cars parked in your driveways...sell you crappy car and get yourself a real car...makes about as much sense as some of this audio advice...
live and let live...
good words to live by...

 

[Hexis22]

some of you guys are very harsh and super critical of a fellow member that simply wants his original 400 repaired and or recapped using stock boards...
really dont understand why...i thought this was a vintage audio support forum...
i dont think there are any rolls royce or Bentley cars parked in your driveways...sell you crappy car and get yourself a real car...makes about as much sense as some of this audio advice...
live and let live...
good words to live by...

I understand many of the comments can come across as harsh, but believe the intentions are well founded.

After seeing dozens of of these amps up close and personal, some people hundreds, I have witnessed some very scary 40 year old factory construction that are just one fault away from destroying your speakers or entire home, not to mention hack repair jobs.

It is very difficult to visually inspect and repair every single potential fault with the factory design and construction.

 

[gene french]

If you can’t swing a proper rebuild there are many options.
One is to trawl eBay for a low cost mosfet amp that sounds decent. Hafler made a bunch for example.

Then sell the PL junk and probably have money left over for fresh zip cord.

It’s like building a drag car and complaining about fuel costs… if you wanna play, you gotta pay.

there are over 200 classes and 15 catagories in nhra drag cars...not everyone wants to be or can afford the aa top fuel cars ...
does this mean the other 199+ classes cant enjoy or participate in the sport of drag racing???
cmon man...

 

[gene french]

I understand many of the comments can come across as harsh, but believe the intentions are well founded.

After seeing dozens of of these amps up close and personal, some people hundreds, I have witnessed some very scary 40 year old factory construction that are just one fault away from destroying your speakers or entire home, not to mention hack repair jobs.

It is very difficult to visually inspect and repair every single potential fault with the factory design and construction.

everything has flaws...even the most expensive audio equipment using the best of parts can and will fail eventually...i have never seen lifetime warranties on any....these units were developed to put power in the average home that did not call for the home owner to refinance the house to own one...evidently successful as they are still in demand 50 years later ...
nostalgia....
some prefer it...
we all cant be ken fritz...if i got that name right...
ease up a bit...there are varying opinions and budgets and desires...
a little respect goes a long way....

 

[J!m]

I never raced top fuel.

Race fuel is still expensive. Generally 6-8 times “super” at the pump.

All I’m saying is: no, I don’t have a Ferrari in my driveway because I can’t afford it. I don’t buy a fire damaged shit box for my driveway and restore it over a few decades.

Just trying to provide some outside perspective. These amps are “legendary” because of their performance AT THE TIME and continue to demand top dollar for what we now know to be a sketchy circuit assembled by u see-qualified people adhering to safety and testing far eclipsed by modern standards.

If you want it, go for it, but understand if you personally are not building it your house may burn down.

 

[J!m]

Further to this: if you are “repairing” to original spec and providing for a customer, you had better lawyer up and have the customer sign a legally binding document fully indemnifying you from any consequential damages. Seriously.

 

[gene french]

I never raced top fuel.

Race fuel is still expensive. Generally 6-8 times “super” at the pump.

All I’m saying is: no, I don’t have a Ferrari in my driveway because I can’t afford it. I don’t buy a fire damaged shit box for my driveway and restore it over a few decades.

Just trying to provide some outside perspective. These amps are “legendary” because of their performance AT THE TIME and continue to demand top dollar for what we now know to be a sketchy circuit assembled by u see-qualified people adhering to safety and testing far eclipsed by modern standards.

If you want it, go for it, but understand if you personally are not building it your house may burn down.

its called progress...happens daily with nearly all...
some prefer the 1970 mopars and which could never compare to todays safety and performance designed cars....guess thats why a 70 hemicuda convertable can fetch a tremendous amount of money...BECAUSE OF ITS PERFORMANCE IN ITS DAY...but still be left in the dust by a hellcat...
not everyone wants the hellcat...
i wouldnt worry too much about the cuda burning down the garage...nor do i worry about my stock 400s burning down my house...
its constructed of steel, cement, and block...
lol

 

[gene french]

Further to this: if you are “repairing” to original spec and providing for a customer, you had better lawyer up and have the customer sign a legally binding document fully indemnifying you from any consequential damages. Seriously.

a mechanic could be held liable for repairing your pinto or corvair....interesting...

 

[Hexis22]

Although the initial outlay may stretch some people’s budget, I can relate as I was there at one point, this amp once updated is one of the best performing amps for the dollar you will find.

Also, once fully updated by myself or others on this site, you will not find a better warranty…

 

[J!m]

a mechanic could be held liable for repairing your pinto or corvair....interesting...

Absolutely. Dad paid huge sums in liability insurance in the 80’s. I can imagine what is costs today…

 

[J!m]

I’ll stop now but any of you independents doing repairs and not total rebuilds are risking everything for a few bucks in your pocket.

 

[gene french]

Absolutely. Dad paid huge sums in liability insurance in the 80’s. I can imagine what is costs today…

maybe held responsible for his work performed ..i doubt he could be held responsible for the design flaws not recalled or factory corrected...cmon man...lol

 

[gene french]

I’ll stop now but any of you independents doing repairs and not total rebuilds are risking everything for a few bucks in your pocket.

everyone takes the same risk every time they perform a service...hence the need for liability insurance ...in all fields...ask aircraft companies about devastating product liability...mr. piper is still being sued these days for the piper cub...designed over 70 years ago...it never ends...