Jer's PLWO to be... (Jer vs the 700, Round 2... it's "Personal" this time)

[Skratch]

If you are using Don's DC protect it comes with standoffs and binding posts that clear everything

 

[laatsch55]

If the person sending the DC PCB had remembered to send it with....yes....but alas I didn't. That makes twice for the Jer.

 

[laatsch55]

Ahh, another dilemna.. Hey guys - does a 700 series 1 have those speaker output posts on the backside that are *shorter* than the 700B? Seems I'm going to have to do the "jer's standoff" again with the DCP... the posts on the speaker outputs don't clear the fuse holders.

(pics later.. eat now.. sammy time... )

Uh, if I had remem,bered to send them , it would have cleared the fuseholders. 1/4 inch hex, 1" long. 4-40 threads.

 

[jbeckva]

No probs... we have the technology...

 

[laatsch55]

It's the application that gets me sometimes.

 

[jbeckva]

Well it was a lot of wranglin, but the DCP's in there and the speaker posts are all wired up (man did I cut those wires CLOSE.. literally!).

I'm bushed for the evenin'... but hmm.. todo...

1. Finish wiring the DCP (EY... question.. I see there are a few "grounds" on the terminals... I have the two "big" grounds covered so I don't think I need to wire those up. But there is a ground that looks to be the ground for the DCP circuit itself. Do I just wire that right to the same place i.e. the speaker grounds??)

2. Wire the inputs... Got the old switch and whatnot stripped out. I put both pairs back in, but only ONE is going to be connected (and direct coupled, at that).

3. Replace the caps

4. Wire the PLWO board up

5. Do the outputs. Hey Lee.. did you mean to send me the RCA410's for drivers instead of the MJ15024's? Figured I'd skip the ones I have in since they too are RCA 410's.. hmm.. maybe not.. ??

Then Pray to the PLWO god... heheh

 

[laatsch55]

1. Finish wiring the DCP (EY... question.. I see there are a few "grounds" on the terminals... I have the two "big" grounds covered so I don't think I need to wire those up. But there is a ground that looks to be the ground for the DCP circuit itself. Do I just wire that right to the same place i.e. the speaker grounds??)

Run a separate ground from each speaker out to the star ground. The ground for the relay coils goes to the star ground also.I'll post a schematic for the DCP.

 

[laatsch55]

Joe has said the RCA-410's have more gain.

 

[mlucitt]

So, a little off topic but I didn't want to start a new thread for one post...

I was going through the PL 400 amps that have been neglected. This one had some caps replaced this morning (thanks Lee!) and a new WOA board, but I could not get the bias to come in high enough. Also, it popped (more like a "crack") on power up the first time, but I could not find any burnt parts. Also, one of the rail fuses was bad (but looked good!!!) and I don't know if it was like that before (I don't test my fuses).

Here's what I found when I did some poking around; I couldn't see one of the drivers "legs" and I noticed the connector pad was lifted slightly.

Wow, these are tough amps! After straightening the leads, the amp was powered up and the bias adjusted right up to 350mv. The DC offset is 15mv on both channels. I should have replaced the driver but it was a new MJ15024G and I am just too cheap to replace it if it works. I can't believe I got in a hurry and installed that transistor like that, at least it wasn't torqued down hard enough to break the lead or permanently short it to the chassis.

 

[laatsch55]

I had replaced all the TO-3 sockets on Kalebs 400, and the pin alignment was so critical if you torqued a littlwe hard it would blow the pin clip out the back of the socket rendering it useless. The pins on TO-3's have to be the most forgiving pins made.

 

[jbeckva]

Lord knows those sockets got me in trouble with the other 700, big time. A big lesson in time and patience!

(just like these caps and moving der wiring around.. which I am doing now... )

 

[jbeckva]

Joe Lee n Mark...

Why in the (bleep) did they make that cap "barrier" (the plate where the BR is mounted and gets screwed on between the caps and the terminals) out of conductive metal?? Those insulators... that's just way too close for my comfort with upwards of 106 volts coming off the BR.. going to think of another better way working with what I have.

(tomorrow tomorrow... I'll listen to you, tomorrow... you're always a daaay awaaaaaaay... heheh)

 

[jbeckva]

ps.. glad I pondered for awhile, then measured things with an ohmmeter... -100 was dead short to ground through the plate.

 

[laatsch55]

Every 700 Ser I I've done Jer the plate gets isolated.

 

[mlucitt]

I guess that's why they got rid of the plate. But it was the early Ser 1, mine is a Ser 1 and it has no plate, the Ser II never had a plate, right? Good catch on the negative side grounding. That -100V is just as violent as the +100V when it gets close to earth.

 

[jbeckva]

Got the tophats straightened out and reseated. Measured good!

Then the "dangerous part" - Hooked up to the variac with the rail fuses pulled. +/- 106V... no current leaking from what I can see on the variac's meter.

And.. the DCP did "the click"!!! Yay.. progress... let me go steal the camera.

 

[jbeckva]

Documenting the progress. Caps in... DCP in and wired up... inputs stripped of "schtuff" and rewired direct.

Tomorrow we should be powering up. Need to wire in the WO board first.

Going to test first with the outputs unchanged to verify the WO board function.

 

[jbeckva]

Oh.. and wow... even after 15 mins with no power, still about +/- 92 volts. That's a good caution to think about when messing with these guys!

Why were there never any bleeder resistors for these monsters? Just wondering!

 

[mlucitt]

I've never seen one up close, are the plates on top of the caps made of metal? And they are grounded? Maybe PL was trying to isolate the 60Hz from the rest of the amp? The later amps did not use them, maybe Lee could do a side-by-side comparison of an early amp and a later Series I around 60Hz to see if there is a greater amount of hum at the inputs/outputs without the plate. Who knows, maybe we will all be scrambling to get/make/buy plates in the future.

Lee, how do you isolate them?

 

[jbeckva]

Oh.. and wow... even after 15 mins with no power, still about +/- 92 volts. That's a good caution to think about when messing with these guys!

Why were there never any bleeder resistors for these monsters? Just wondering!

I should HEED my OWN advice here - Was getting ready to mount the bias trannies... POW WHAP!!! The + Cap when right ta ground... (luckily nothing was between that I can see!) After what.. 7 hours... that cap still had a good 70 volts on it!!!

(next step.. make a bleeder rod/resistor.. asap... )

I need coffee... badly.. heheh