Kevin's PL400 Upgrade

[wattsabundant]

And how does this relate to Kevin's PL400 upgrade? I'm just sayin' (and running for cover).

There is never a wrong time to talk safety. I promise you some day someone at these forums is going to lose an eye, get burned, or get killed because not enough people bring up the safety issue.

 

[mlucitt]

I'm not knocking safety, I'm just trying to keep the thread on topic. Nothing is stopping you or anyone else from starting a new thread on safety. I'm sure we would all visit that thread, in fact it may be more valuable and have more impact if it was a stand alone thread rather than buried here in Kevin's PL400 Upgrade thread.

I guess I'm saying that at least an acknowledgement that the thread was hijacked or a request to post off topic content would have been nice. But to quote my tongue-in-cheek comment and then admonish me about safety is a bit over the top. I have seen my fair share of electrical or electronic accidents and I am a certified Navy Safety Inspector having completed over 40 hours of classroom training and a year of on-the-job experience. I was in that role for 14 years, I still have both eyes, ten fingers, and all my teeth. You have made your point about safety, thank you.

 

[kevin]

Hold on now..... Ive not said a word and on this safety topic and Lee hits me right in the head with the " coal mine '' hammer..... LMAO ..... Yep, Ive worked in coal most of my life but my ass has never been underground. But yea Lee how those guys under there stay alive is beyond me...

 

[laatsch55]

Kevin all coal out here is surface mined. They have about 70-90 feet of overburden and there is 75-150 of coal underneath that. I did spend a year underground in an iron ore mine for CF&I steel in Guernsey, Wy. 800 feet under, one thing about it, when the lights go off down there that's DARK!! How's that for off-topic.

Mark, one of the charms of this place is not having to follow proper forum protocol. I'd hate to have to think about starting another thread every time I wanted to be a smartass or totally irreverent. But if you would like your threads treated that way, I can honor that.


NOTICE!!!! This thread has been officially hijacked for no particular reason., other than humor.

 

[mlucitt]

As long as you were thinking about powerful audio amplifiers while you were sitting in the dark it's OK. BTW, what do all of you men do down there when the lights go off? And I hear that the lights go off all the time...

Hey, one or two hijacks is fine, but when you start to make a career out of it, sheesh.

(Humor is never a hijack)

 

[kevin]

Wow Lee.... What a ratio.... We go 300 feet here for 4 feet of coal... Now.... Im going to sit back and read. Yall just know this.... I look forward to getting on here and reading everything yall say.... Mark... I promise not to get off subject anymore.... lmao.... And thank you for the great job on the amp....

 

[Gibsonian]

I think Harry Connick said that safety is just danger out of place.

 

[laatsch55]

Safety as a practice is fine, as an institution, it thinks way too much of itself. Mark, when you lose power underground it's a long climb out.

 

[mlucitt]

Speaking of losing power, we should not have that problem when the big bass notes hit. Look what came in the mail today:
[attachment=0:1eb6jiie]Joe's Cap Package.jpg[/attachment:1eb6jiie]

I will assemble the caps and install this package in Kevin's amp. Then the testing starts, woohoo!

 

[mlucitt]

The caps are assembled but the fit in the original PL400 clamps is not to my liking. I think I will explore some 40mm clamps and maybe I can reuse two out of three original mounting holes.

Thoughts from the safety gallery?
[attachment=3:lbmkcr7r]Caps 1.jpg[/attachment:lbmkcr7r]

BTW, this is how to assemble these, at least my method. Solder the boards to the top cap with a piece of manila folder in between the cap and the circuit board (Joe told me about that little trick) to get the proper clearance.
Like this:
[attachment=2:lbmkcr7r]Cap Spacers.jpg[/attachment:lbmkcr7r]

Once the boards are soldered in place, cut the support wire to the length of the caps plus 1/2". Then solder the wire in place on the top cap like so:
[attachment=1:lbmkcr7r]Cap Assembly.jpg[/attachment:lbmkcr7r]

Once the wires are soldered on the top cap, insert two or three pieces of manila folder between the bottom of the top cap and the bottom circuit board to prevent the sharp cut terminals from gouging the bottom of the cap. I turned the assembly over and soldered the wires from the bottom of the lower circuit board.

Be sure you have the insulating sleeve tubing on or you will have to start over. Also make sure the caps are aligned + to + and - to - or you will be sad.

I added a bypass cap to the upper assembly but make sure the wires don't stick out the bottom.
[attachment=0:lbmkcr7r]Final Cap Assembly.jpg[/attachment:lbmkcr7r]

16,400 uF of capacitor storage on each side for a total of 32,800 uF for the amp. Joe, I like it. I thought the wires were pulled tight to hold the caps together. Now I see the rigidity of the larger gauge (16 GA) is what holds the caps in position relative to each other.

 

[laatsch55]

Pre3tty trick setup. I like the way the 22,000 uf's fit in the 700's tranny recess, like a glove.

 

[mlucitt]

Kevin's PL400 lives!
I had an initial setback the first time I applied power to this amp. Driver transistors only installed. The dim bulb did its job and went super bright as I dialed up the variac power. I pulled the B+ and B- fuses and the lamp stayed dim all the way up to 120VAC. I put the B+ fuse in and it was fine, so I had a problem on the B- side. I disconnected B- from the board on terminal 12L and that had no effect, still had massive current draw from the PS.

With the power off and disconnected I checked D15 on both Right and Left channels, I didn't have to check D14 because that diode is associated with the B+ voltage.
The D15 diode on the Right channel checked fine but the D15 diode on the Left side indicated .003 Ohms resistance in both directions. I removed it and it was shorted.

I replaced the Left channel D15 1N4004 diode and powered up the amp with no problems. Now we know why this amp had no fuses in it when it arrived in the shop.

The DC offset was .011 VDC on the Left channel and .013 on the Right channel. I set the bias to .350 on both channels and I will re-adjust after I install the MJ21196G output transistors. This amp has rail voltages of +/- 82.4 VDC so it should perform well.

Here is a picture of the amp (one channel loaded at 200Hz 1.5V input):

 

[kevin]

WOW..... Thats about all I can say... Im sure your getting sick of me saying THANK YOU !!!!! Just talked to Sutton yall. He was in a cab in Califorina. He will be back on line Tuesday.

 

[laatsch55]

I haven't had one show up with one of those diodes bad. They seem to be pretty robust.

 

[Skratch]

Mark I always replace all the resistors and diodes in the output section. I've had open .22 resistors on 1 that I rebuilt, almost all the 40 year old amps that we pick up have had work on the outputs at one time, very few virgins. I use MO on the emitters and MF on the 150 and 10 ohm 1 watt vishays on the others. Takes a little more time but it is like buying insurance

 

[mlucitt]

Skratch, agreed - the carbon composition resistors are past their life expectancy in my book and are always suspect. I wiggle them around to see ithey are cracked or brittle and then check them with the digital VOM. The nice thing is that they can't short, they just open and then it is usually not catastrophic. This amp had very little work done on it if any and it appeared that the diodes and resistors were original, but you are right; this is the exception and not the rule.

Lee, this is the first bad 4004 I have seen, they ARE robust little dudes. Wanna buy a used one real cheap?

 

[Skratch]

I am going to be doing a 400 and I am going to check the current sharing with the old emitter resistors and compare them to the new MO resistors when finished with the same outputs and driver board. The only thing I am going to do is change emitters and check current. Then I am going to upgrade the rest of the amp. Driver board , PS supply caps, outputs, bias transistors and then check the current sharing again.

 

[mlucitt]

Skratch, that will be a very good test. We don't have much Before and After quantitative testing here on the forum. For one thing the main boards are less than a year old. Also, we get so excited we just forge ahead without making any measurements; then those tend to be qualitative and subjective, "It sounds so much better." Joe did some B/A testing on components and more rigorous testing like that is always a good thing.

For your current sharing do you shutdown each time and use clips or insulated probes on a live amp? If I can get the board out of the way, just probing seems to work. But do we need the board attached at all? Wouldn't the current sharing be the same with the board in or out? I always did it on a complete and working amp, but you have made me think about this...

How are the faceplates coming?

 

[Skratch]

I use clips on a live amp with 30 volts on the outputs. Bias at .380. The face plates are here but my guys have not got then in the CNC's yet. Paying customers first. We just bought out 2 competitors and consolidated all the mold making here, working 24/6 to keep up.

 

[laatsch55]

Skratch, what are you going to measure or test when you do the current sharing comparison. Run a known voltage, check resistance then calculate current, or unsolder each resistor and run your meter in series? What are you trying to quantify? Forced current shari ng is not a hard task to bring about, Just wondering what you are hoping to see when you compare.


BTW- I'm seriously persuing an Audio Precision One analyzer. Then I shall be able to quantitative the shit outta things. May take 5K to get it headed this way.