Phase Linear 400 output substitute

audiogymp

Active Member
Hi

I recently bought a PL400 needing attention. One channel has original drivers and outputs (RCA 410 and XPL909). The other channel has some different components - Drivers are SJ2741 and the outputs are a mix of four PL909 and two MJ15024 - not good.

Arrived with no main fuse. On DBT (with fuse) it draws too much current. Measurements indicated that three of the connected outputs on one channel were conducting C-E (one measured alright out of circuit). Unsurprisingly, these were on the channel with mixed output devices. With the three removed, the current draw looks normal on DBT.

It looks like I can fix the amp by replacing outputs on the on the bad channel. It looks like I would need four PL909 to do this. They don't appear to be easy to come by. Also, the XPL909 on the good channel have green writing, which I have read is a bad sign.

There are threads that suggest that MJ15024 or MJ21195/MJ21196 can be used as outputs. But it also looks like the choice of outputs may depend on whether the circuit in the PL400 is full complimentary or quasi complimentary. The PCB in my amp appears to be the PCB 14A type.

I would appreciate it if someone could tell me whether the amp is full or quasi complimentary and whether there is a commonly available output device I could use. This may be crazy-talk but the 2N3055 is cheap and convenient to get and looks like it might be compatible, save for the low VC of only 100V.

Any suggestions?

Thanks.
 
All of the TO-3 xsistors in your amp are NPNs so it's quasi.. Get any of the ON Semis, MJ15024, MJ21194 or 96, replace all six, you could even use those for drivers also. The mod to full comp isn't very complicated if you have some experience. If you move the drive board around in your repairs be careful of the leads to the bias xsistor they tend to break at the xsistor. While the 2N3403 is still avaiable you'll have to do some searching.

Craig

Just checked Mouser and they have plenty of the 2N3403.
 
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I probably have some 909's and 410s

If your going Full Comp, don't mess around, get the White Oak Audio back planes (for Full Comp) and Rev E control board as well as the dimlay protection circuit. The build is not easy by any measure and you need some fancy equipment for measurements. Also wire routing is very important for no noise so it's meticulous work to get a WOPL sounding correct. The back planes eliminate the TO3 circuitry completely. You use MJ 25s and 26s. Once done, not many amps can hang with them, especially for dynamic output/reserve headroom. I had a 400's meters buried to the firewall and it sounded glorious
 
Thanks to all for the generous assistance.

And thanks for the warning about the 2N3403 - I'll see if I can stabilise the leads while moving the PCB from now on.

At this stage I am looking to get the amp going in more or less stock form. I've read about the White Oak mods and that's something I'll be looking at down the track, although I don't have fancy equipment (the high points are my ancient thirty buck CRO and a Chinese component tester circuit elegantly housed in a plastic food container). As for experience, I still seem to be learning a fair bit from each repair.

I've read that the 410s are the best sounding drivers, so I am planning to get some replacements. They would need to come from the States, so Northwind's offer of parts might be a sensible option. Failing that, the MJ21196G appears to be the most cost effective replacement option if I need to replace the outputs in number.

I've worked on quasi and full complimentary circuits and thanks to the explanation I now understand the words for them. As I understand it, the even/odd numbered transistors are complimentary NPN and PNP pairs (for full complimentary circuits), so I stick to the even numbers here as I just need NPNs.

I was thinking of building inexpensive speaker protection based on this Chinese circuit -

http://www.ebay.com.au/itm/2-channe...580107?hash=item1c3f175d4b:g:IykAAMXQrhdTSOtM

It wants 15-24V AC, which doesn't occur in the PL400, so I might build it as an outboard unit with a separate power supply. Is this a bad idea?

Thanks again, Jon
 
21996's are the beefiest of the choices and are most durable. I have those in my 400 and 700. Your idea for DC protection for outs is bad only cause the Watts Abundant unit is so easy to use with your amp. Have fun and good luck!
 
21996's are the beefiest of the choices and are most durable. I have those in my 400 and 700. Your idea for DC protection for outs is bad only cause the Watts Abundant unit is so easy to use with your amp. Have fun and good luck!

I second this but would correct the part number (MJ21196 ;) ). Slap those in there and be done. If the amp is the series one then all the transistors in the back can be replaced with those. White oak boards are awesome but a big step for full comp. I did it and never regretted the change.

And please just use the watts abundant protection relay. Excellent quality for the money.
 
I second this but would correct the part number (MJ21196 ;) ). Slap those in there and be done. If the amp is the series one then all the transistors in the back can be replaced with those. White oak boards are awesome but a big step for full comp. I did it and never regretted the change.

And please just use the watts abundant protection relay. Excellent quality for the money.
Can someone tell me how to get hold of a watts abundant speaker protection board??? I've messaged the watts abundant website contact email 3x in the last 6 weeks with my PayPal info hoping I could order one.
 
i have a fully WOPL'd PL 400 mk II and it is fanstastic- worth going all the way for
Did you go full complimentary or quasi-complimentary...or actually wasn't the series 2 already full comp?? I'm planning on going wopl'd eventually, right now I am just looking to get it as good as I can while keeping it mostly stock. I don't think mine has any more then maybe 24hrs on time if that. I got it out of the original box and it still had that "new/old" electronic smell lol. Kinda like opening a brand new amp out of the box in grammas basement next to a box of old clothes lol
 
I have two 400 Series 2 and both were QC. One is now WOPL QC and the other WOPL FC. The FC sounds better but the QC is still excellent. Both have the Watts Abundant board.
 
Make sure you also check at least the drivers, predriver, VAS, diodes, and replace all the electrolytics on the amp board.
 
Did you go full complimentary or quasi-complimentary...or actually wasn't the series 2 already full comp?? I'm planning on going wopl'd eventually, right now I am just looking to get it as good as I can while keeping it mostly stock. I don't think mine has any more then maybe 24hrs on time if that. I got it out of the original box and it still had that "new/old" electronic smell lol. Kinda like opening a brand new amp out of the box in grammas basement next to a box of old clothes lol

full comp, back plane, etc. the whole nine yards
 
Have you tried to reach Watts Abundant thru Phoenix?
No I have not, do you know the link to go thru?? I already got a DC protection board thru ebay but I would love to get the watts abundant one for when i eventually go Whiteoak'd (gonna slowly get everything I need before I actually switch it to a WOPL400.
 
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