Jerry's "Gonna Rebuild me PLWO 1000" thread

[jbeckva]

Going to use those terminal blocks on both the main and dc protect pcb's... Rewire all grounds and whatnot for the common/star ground approach... replace the sockets... probably replace the regulator IC that got so hot with the old DCP board. Replace emitter R's with new 1 percenters (soon as I can find the .27's).. replace the MPS8099's (? those bias trannies.. since my bias has always been a bit on the high side.. ). That should do 'er, I think.?

 

[jbeckva]

Oh yeah.. new pots too...

 

[laatsch55]

Bias trannies are 2N3403's, Regulator is a TIP31C, Q4 is an MPSA93, Q3 a 2N5087 or TIS 93, Q1,2 are TIS 97's.

Save the 2N3403's, we'll use the heatsinks for a sub tha Joe has come up with.

 

[jbeckva]

Ok, got the care package! Thanks man!

Now time to strip it all down. By chance does anyone have a good wiring diagram with the PLWO pcb wired in, or do I need to create one?

Off to the store to get some supplies and whatnot, then time to start...

 

[Gepetto]

Preserve the old metal strap from the 2N3403. Knock the original flanged TO-92 2N3403 out by a gentle tap on the open end of the strap. Use cyanoacrylate (Loctite 444 or equivalent) to lightly glue the 2N5088 substitutes into the original metal 2N3403 strap. It is not essential but helps with the heat transfer. We use the same technique to adhere thermocouples for doing temperature measurement work.

 

[jbeckva]

Bias trannies are 2N3403's, Regulator is a TIP31C, Q4 is an MPSA93, Q3 a 2N5087 or TIS 93, Q1,2 are TIS 97's.

Save the 2N3403's, we'll use the heatsinks for a sub tha Joe has come up with.

Ah, thought that "regulator" was a 220 package IC, not so eh? So the TIP31C is a good sub for the MJE15030G that's in there currently?

Got the PCB off.. takin pics... yep, there's going to be a LOT of solderin going on here...

 

[laatsch55]

Yedp, that's OEM anyway. It will also take the 15028, 15030, 15032

 

[jbeckva]

That's cool. Well, I placed me Mouser order for the terminal blocks, heat sink grease, new bias trannies, and a few other odds n ends.

Question tho... I'm looking again at the DCP and mounting it right on the speaker terminals, but I think those terminals are a wee bit too big on the contact/inside. Is the DCP really designed for the stock terminals? i.e. should I just leave it where it is?

 

[laatsch55]

It is designed for the stock termionals, the ones in yours AREN"T stock. Should have sent som e to ya, I have a few.

 

[mlucitt]

Lee knows this amp, but for the rest of us, post some pictures - please!

 

[jbeckva]

Pics a comin'!

 

[laatsch55]

So is grandma , but she's 85.

 

[jbeckva]

Hehe.. they will be soon. But hey.. got a question here... in between each double bank of outputs seems to be three terminal points, right? One ties all .33's, the other ties all the .27's - I get that. What about the one in the middle? Is that just distributing and tying the common/ground on the caps to the chassis?.. and two points at that?? Why is there a wire that goes from the star ground on the caps... to the first tie point (terminated to chassis ground).. then to the 2nd tie point (again, terminated to chassis ground)? Esoteric, of functional?

 

[Gepetto]

Hi Jer
Those 3 position barrier strips are for 2 purposes.
1. They tie the actual metal chassis to the DC starpoint ground at these 2 points
2. These serve as a ground for the small bypass caps (usually about 0.33uF polyester caps) that Phase put on the plus and minus rails for the right bank of output devices. I think Phase was trying to tame oscillations and this was one of the methods that they used for that. The right channel runs have a longer length of wire from the plus and minus source origination and the inductance of these wires can be countered by putting these small bypass caps where they did. Not a bad design practice. Not all amps had these caps installed, I have noticed.

 

[laatsch55]

Another question to ask Ed.

 

[jbeckva]

Ok, after doing some documenting, here's where we are at.

Right side's torn down, getting ready to start mounting the new sockets and rewiring. I am going to do all point to point here - less chance of shortin' stuff and whatnot..

Driver board with new term blocks and sportin' a new '220 Q (old one got really HOT with the original DCP boards, so I'm not taking chances here..)

The aftermath... what a mess... heheh

 

[jbeckva]

Half the sockets mounted with the driver/base buss completed. Figured I would go with 1 percent 10 ohm bias resistors...

Nice n easy going... no rushing... or things can go pOOf when the power's applied (Lee.. no.. I will use a DBT and variac.. hehehe).

 

[jbeckva]

Crap crap crap... Looks like I am going to need to get some 150 ohm resistors. I just measured 'em.. anywhere between 140 and 283 ohms! Wow.. the 140 I can probably live with, but 283??

(placing order with der-mouser place... )

 

[laatsch55]

Lookin good Jer. Were the 6-32's too long??

 

[laatsch55]

Was the epoxy hard to get off??