Kevin's PL400 Upgrade

[laatsch55]

To follow what, the return of Christ??

 

[kevin]

Id say the rebirth of this amp is going to be close !!!!! LMAO !!!! Cant believe i said that !!

 

[mlucitt]

I received the DC Output Protect Relay Boards from Don today. I guess we could say we were waiting for those. Once that baby is in and wired, here is what we have left to do:
o Reinstall the wiring on the bias transistors and glue them down to the amp chassis
o Install the new 1200 Volt 35 Amp Bridge Rectifier
o Install the new Power Cord Jack
o Prep the Wires and Install the WOA Main Board
o Wire the new WOA Light Board
o Install the WOA Main Capacitor Kit and Bypass Caps
o Test and Burn-In

Mark

 

[laatsch55]

IS THAT ALL????????? How'd the body work go??

 

[mlucitt]

The chassis is still a work in progress. I have to bend a little and step back and take a look, then bend a little more, etc.

 

[laatsch55]

Tedious, very tedious.

 

[kevin]

Hey Mark And LEE.... Let me change the subject just a sec and ask yall a question. I have developed a hum in my stereo that was never there before. It started when I hooked up a halfer p-500 about a month ago. Its Suttons amp and Dont think thats the problem cause its not even plugged in anymore... lol. I run amps and pre amp and the hum is in center channel ... sub... and rear. Any Ideas ??????

 

[mlucitt]

If any of the AC plugs are the two-prong variety turn them over one at a time in the outlets and see if that helps. It is only a possibility but it costs you nothing. If that does not help, you will have to find out if it is inside one of the components or outside. Sometimes you can take a "noisey" device such as a neon light and hold it next to a cable and see if the hum gets louder, you will know when you find it. If that does not help you may have a bad cap or resistor in one of the units and those are very difficult to find (without shocking yourself or blowing something up).

Lee can chime in, he is an expert here...

Mark

 

[Gepetto]

Kevin
If you have any connection in your system to broadband cable, that is a usual culprit that has to be isolated. If not that, if you have more than one piece of equipment with a 3rd prong safety ground plugged in, that will lead to ground loops and hum. The usual remedy there is to only have one piece of equipment with the 3rd prong safety ground connected and to float the others.

 

[laatsch55]

Mark, THAT was the expert.

 

[kevin]

Cool... Thanks yall. Ok Mark I did try turning the plug over on the halfer... didnt help. What about this.... This is the first winter that I have ran an infra-red heater in that room. I thought about that. But when i move it up-stairs I still got the hum. My down stairs is just pretty much my stereo room, I only have a 100 amp breaker box on the down stairs, Now.... I know very little about electronics but im pretty good with electricty. Could i have a weak breaker. Im pretty sure all my stuff is running on one 30 amp breaker.... Just a thought. Gepetto.... yes i am running broadband cable.... but i have been for years and this only started a month or so ago... how do I isolate it as you say ???? Now .... do I cut the third prong of all but one of my stuff... And what do you mean about floating the others.... I really thank yall for your help. O yea... Mark !! can not wait to see what you find on that halfer Sutton sent you... What ever it is my other one has the same problem... Ive hushed now....

 

[laatsch55]

Does the Hafler have a cooling fan?? I've had some fans inject noise into the music signal for some reason or other through the AC line. I don't quite understand it, but I quit using that fan and it quit. Have you isolated your equipment from the catv stuff?

 

[laatsch55]

And don't worrty about "hushing", very few problems get solved in silence.

 

[kevin]

LOL.... Yea it has one.... But hell I dont even have it plugged up anymore... Ive got a pioneer pre amp and im running my center channel off it. Ive got a denon avr-3000 reciever briged and just using it as a amp on the rear.... My sub has a plate amp. AND SOME DAY I WILL HAVE I WILL HAVE A BAD ASS PL ON THE FRONT.... LOL.... Ive really not done alot of trouble shooting on this but its starting to really bug me so im gonna pull it all out and find it real soon.... Ive been wanting to ask yall about this for a week or so and wasnt sure where to ask so yesterday i just chimed in here....... And by the way Lee sutton tells me your an oil man.... Ive worked in the coal industry most of my life... Ran a D11 dozer for years... also done alot of welding.... love to mig weld alluminum.... Now.... Im selling cars.... lmao...

 

[ksrigg]

Kevin,

I used to have a heck of a problem with ground loops until I finally tracked it down to my TV cable company. I know you have cable and not DirecTV, so I'd try with your cable unplugged from you system and see if that could be it. I finally had to install a grounding rod, like a lightening rod in the ground, and that got rid of the problem. Can't remember exactly WHAT got earth grounded, but that was the fix...

 

[laatsch55]

Yep im in the oil bidness, a few coal mines around here. Gotta check your braiin at the gate every morning so i don't hang there much.

 

[mlucitt]

Don't cut any prongs off of your AC power cables, just buy an adapter that allows you to plug a three prong plug into a two prong outlet and make sure the ground wire or tab is not making contact with the screw that holds the cover plate on (use the bottom outlet). That is another easy fix if you have three prong plugs. If that does not work, you may have a bad cap and you will just have to replace them until you get the bad one or replace all of the electrolytic caps at once and hope for the best. Of course if you see one leaking, there is your culprit.

See this one? The white crud leaked out and dried, it might be corrosive.
[attachment=0:1o61nkl3]Bad Cap.jpg[/attachment:1o61nkl3]

These can cause problems if they are connected to the power supply.

 

[mlucitt]

Kevin, I did get that Hafler P500. There were 1000 dead spiders in it and all their old real estate. I am quite certain everthing in that amp is original, no tracks in the dust. I want to clean it up and test it at a few different frequencies to see if it might be a specific cap or connection point (right or left or both). You probably have some bad old original caps and I will just replace all of the electrolytics and test it again. If it both channels, it's probably the preamp board. The thing is a brute. Do you have others that are acting like this? I'll try and see if this one fix can be applied to others.

Your packing was great. The outer box split open, probably in the rain but the inner box was fine. The back pieces of sheet metal that stick out to protect the fuses and such are bent, I'll bend them back. One of the fuse holders had a chip off the cap, I couldn't find the piece, it might have been that way.

All the fuses are good and that is always a good sign. But you need new power supply caps. At 20,000 uF and 100 VDC they will not be cheap...
They look to be 2 1/2" D and 5 1/2" H. Those ratings will probably result in a smaller cap these days or we could look for 22,000 or even 25,000 without going any bigger (there is no room anyway).

Mark

 

[kevin]

First off gotta give that great packing job to Mr Sutton.... He would be the daddy of that great job.... lol. Yea Lee ive got one just like that doing the same thing... If i remember right one channel was ok.. the other one didnt work at low volume.. and seems like the clipping light came on the bad channel at low volume as well . Im going to dive into my stereo on Sunday and try to find that hum.... I really thank all yall for your help.... and nope... im not going to cut any prongs.

 

[mlucitt]

I got the Bench Mule together and I learned something very interesting. If you break the connection (can be a short wire or a low value resistor) between the input ground and the output ground (like many say you should do) and you don't provide a path for the WOA board to chassis ground - you will have reduced DC rail voltage on the speaker outputs. The reason I broke the connection was to eventually install the Wattsabundant DC Output Protect Board and his instructions have you break the connection and run the input ground back to the STAR ground (good idea) but I forgot to do that part. I figured the inputs were grounded to the common on the board but in this amp, that wire runs from the board back to input ground not the STAR ground, unlike the other PL400 I have.

At least I can check boards now, Lee yours are the first up.

[attachment=0:3qdf6phk]Mule.jpg[/attachment:3qdf6phk]

BTW, this is a new WOA board with bias dialed in at 300mV without touching the bias adjustments hardly at all. The DC offset was .013 and .010 right and left. A nice one.