My New Early Model Phase Linear 400 w/ 4 Fin Heat Sink

[punchback]

I’m the proud owner of a new “old” PL400. It seems that it is an early model with a 4 fin heat sink configuration. It also has fuse type lamp to illuminate the meters from the top. This meter illumination apparently prevent me from using the White Oak Audio LED upgrade. Let me know if there is a way to make it work with my PL400. It is operational and has the stock (12pcs) PL909 and (4 pcs) SJ2741? The front panel is rough and has some sort of clear splatter on it. My wild ass guess is the splatter might be floor wax??

I’m looking for suggestions as to what is a must do upgrade. So far the following is what I plan. Let me know if I’m missing anything.

1. It seems that most everyone upgrades the power rail caps to ~15,000uf @ 100V. I know that WOA offers a kit where they stack 2 caps to accomplish that but I’m not a fan of that look. I’m kind of looking at the following caps from Mouser. I’m not sure exactly what to look for in a cap such as this… Would it be better to get a 105°C cap (80-ALS80A163KF100) or a cap with a higher ripple current and little lower ESR (871-B41458B9159M000)? Both are almost the same size as the currently installed stock capacitor. Or is there some other reason to get one over the other?
2. If I upgrade the caps I’ve read where that puts a strain on the bridge with all of the inrush current when it’s turned on. Should I upgrade the bridge? The current bridge is a 200V 30A (MDA990-3) with a date code from 1971. The next step up in current rating at Mouser is only 35A and the next step from that is 50A (905-KBPC5006T)
3. It goes without saying that I’ll be installing the Watts Abundant speaker protection board.

Future Upgrades

1. The front face plate is a little rough. I’ll be attempting to clean it up. I see where someone on eBay sells a reproduction. Has anyone used this reproduction and been happy?
2. Eventually I’d like to install the WOA control board.

Alan

 

[avionic]

Get in touch with Laatsch55 over at phoenix. Lee has done quite a few of the WOPL's
https://forums.phxaudiotape.com/forums/wopl-building.68/

http://audiokarma.org/forums/index.php?members/laatsch55.33651/

 

[mbz]

If you plan to use it before fitting the spkr protection then certain fit the back to back diode to prevent the latch up
condition. Certainly the pheonix guys have you covered.

 

[punchback]

I definitely intend to install the speaker protection but must admit I'll be tempted to run it before I've done that. I've read about that diode mod to protect from latch up. I found the post below from laatsch55. Does back to back mean in parallel?

Soldering two 1N4148's back to back on the back of the board to the leads of C6 will prevent random latch up of the positive rail voltage to the speaker outs. So if you change C6 leave about 3/16's of lead sticking out.

Any opinions on the caps or bridge?

 

[mbz]

yes, in parallel across C6

 

[mbz]

Any opinions on the caps or bridge?

I have 2-3? PL400's in the shed waiting refurb.
I will WO one however I will use United Chemi-Con SMH series, I like these in the larger amps..
They are snap in so they will need some work, screws would help but the specs on those
caps is not great. UCC also make a 105C KMH if you must, however the SMH specs are better.

 

[punchback]

the specs on those caps is not great. UCC also make a 105C KMH if you must, however the SMH specs are better.

Help me understand how the UCC SMH is a better cap. To my untrained eye the specs look comparable... I'd rather have the screw terminals.

 

[Gibsonian]

You can run as long as you fuse the speakers. I ran a stock 700 for years that way, with associated full rail issues occurring, and speakers always protected.

 

[mbz]

Looks like I've been talking b.s again

Quick compare of the data sheets, not really comparing apples
but best I could do.



The UCC-KMH has lower ESR (20%) than the SMH, the 105C rating trade-off is with the ripple.

The TDK B414 appears to be the pic with ESR/Ripple

Certainly screw terminals are very desireable

Will try and keep b.s to a minimum.

 

[GlasgowGrip]

@mbz: Maybe not apples to apples... wouldn't you usually want to consider ripple current at the same operating temperature to be fair? I believe a 105C-rated cap will generally state a lower ripple current than a similar size and capacitance 85C-rated cap. Often the datasheet will provide a table of multipliers showing how ripple current can be increased at various lower operating temperatures. Although I'm looking at a UCC KMH datasheet now and that table seems to be missing. Hmmmm...

 

[Artie]

It seems that most everyone upgrades the power rail caps to ~15,000uf @ 100V. I know that WOA offers a kit where they stack 2 caps to accomplish that but I’m not a fan of that look.

Alan

Just my 2-cents worth, but I think that's a fairly well proven mod. And, it IS on the inside where know one will see it. Whatever you decide, good luck with this project. I have a broken 400 II that I'm hoping to also do the WOA mods to.

 

[punchback]

I found some Kemet caps that fit perfectly.
They happened to be 16K uF 100V but the choices narrow down at that size with screw terminals.

 

[punchback]

I ultimately built and installed both the White Oak Audio and the Wattsabundant speaker protection. I had a little problem when I started the WOA board. The problem was there are two transistors that monitor the temps of the output transistors. Mine were wired with the colors in the wrong sequence. I found out when the dim bulb didn't go dim when it was supposed to. I thought I had assembled the WOA board wrong. I spent an hour or more going over it with a fine tooth comb. I happened to check the wiring with one of those ebay transistor checkers and found the wiring mix-up. Everything is good now.

 

[Gibsonian]

How is the amp sounding now?

 

[punchback]

The amp sounds great. I've recently bought a PL 2000 preamp that I'm in the process of updating.

 

[Gibsonian]

Nice. I had a 2000 a few years backk and wish I'd of kept it. No upgrades, just recapped and sounded pretty good. With modern opamp upgrade am guessing could go up a notch or two. I have two WOPL's, both build by Lee L. A 700 quasi and a 400 full comp.