Mark goes at it again... just bought a PL700/II!

DC circuit arrived yesterday from Don, raising a hypothetical question:

Suppose did leave the zobel intact on the DC board?

Just how badly would I throw off the impedence balancing, and what would I burn up in my amp?

(Electronically it makes no difference, but) Is there a benefit to use the zobel on the DC board instead of the backplane board since it’s physically “closer†to the speaker terminals? (That question is moot and I know it.)

Just a mad scientist question, I’m not going to experiment to find the answer since I’m asking people with a higher pedigree in this field!
 
MarkWComer said:
DC circuit arrived yesterday from Don, raising a hypothetical question:

Suppose did leave the zobel intact on the DC board?

Just how badly would I throw off the impedence balancing, and what would I burn up in my amp?

(Electronically it makes no difference, but) Is there a benefit to use the zobel on the DC board instead of the backplane board since it’s physically “closer†to the speaker terminals? (That question is moot and I know it.)

Just a mad scientist question, I’m not going to experiment to find the answer since I’m asking people with a higher pedigree in this field!
Click to expand...

The closer the zoebel is to the output circuit, the better Mark. That way it absorbs the inductance of the wires from the backplane board output wires as well as the speaker wire inductance. If it was not for the wiring inductance leading from the output of the amp to the speakers, the zoebel would not be in there. The zoebel is not needed for stability.
 
Gepetto said:
The closer the zoebel is to the output circuit, the better Mark. That way it absorbs the inductance of the wires from the backplane board output wires as well as the speaker wire inductance. If it was not for the wiring inductance leading from the output of the amp to the speakers, the zoebel would not be in there. The zoebel is not needed for stability.
Click to expand...

AHA! So it does make a difference!

My knowledge increases... thanks!
 
Does anyone know the Mouser part number for the Sil-Pads? I bought the wrong thing last time, they had an extra hole, potential spark opportunity.

While I'm at it: How about a recommendation for the bridge rectifier? If I'm gonna gut from the basement to the penthouse, may as well do the rectifier as well...
 
Another fun thread Mark :glasses1:

As to your remark about not needing 500wpc, you can never have too much power :twisted:, seriously, headroom is your friend! My Summits are rated that they only need 300 and I'm glad I have 500 on tap for those surprise peaks you forgot were coming, especially with Shpongle :iconbiggrin:

And she is a looker :love5:!!!!
 
And while you are at Digi-Key, get a 800-1200 volt, 50 amp stud mount bridge rectifier..,.
 
stuwee said:
Another fun thread Mark :glasses1:

As to your remark about not needing 500wpc, you can never have too much power :twisted:, seriously, headroom is your friend! My Summits are rated that they only need 300 and I'm glad I have 500 on tap for those surprise peaks you forgot were coming, especially with Shpongle :iconbiggrin:

And she is a looker :love5:!!!!
Click to expand...

Yup- no argument! But here’s what I notice- the amp does NOT get “tired.†I dont know how to explain that, but I think it’s not only because I’m not really cranking at full output, but the excessively large capacitors store enough juice that when the transients do hit, the amp recovers the reserve that much faster. The largest amp I’ve had in the past was 120wpc (Realistic STA-2300) and after a while of putting it through its paces, it just seemed “tired,†less able to keep volume, and unable to cope with the demands of high energy transients (I have a lot of 12†45RPM club remixes- and they’re pretty dynamic!).

I was very much into CDs when I had that receiver, before they were making “remixed†CDs and pushed everything up into the top 20db of the digital dynamic range- and the wider dynamics of those original CDs really made the issue obvious. I’ve gotten rid of the polycarbonate and went toward vinyl because I like the sound of “analog flaws†much better.

Yeh... a “looker!†It took a long while for a 700/II to show up that didn’t look like it was dragged behind a truck!
 
That was in the parts database in the WOPL archives...
 
So... again another ridiculously long hiatus... more apologies for my protracted absence. It seems that I have rotating hobbies, just now off-ramping from my 16mm movie projectors and miscellaneous other bullshit.

Winter is pretty much done here in the south, emerging from my hibernation, and put in my order for the driver circuit and capacitors.

Printing all my previous stuff from the PL400 to put into a binder as a sort of "service manual," and starting to do the same for the 700. Having a refresher view of the amp, looking at 4 RCA 410s at the bottom of the totem, 20 OnSemi 21196s. Not sure I want to use the existing NPNs even if it saves some bucks, don't know what abuse this baby has endured. DAMN! A hell of a lot of thermal grease from the last surgery! Surprised to see that the previous surgeon used SilPads instead of mica in conjunction with the grease, and I'm considering using 2 SilPads for each transistor (opinions?).

I also see that this massive beast may have been DROPPED, the transformer isn't perfectly square. It works, if I loosen the bolts and try to shift it back I worry that I may impinge a few windings. The sucker is heavy, no surprise if it was dropped (my Bell & Howell 1540 FilmoSound was also dropped, bent rewinds and bottom plate...).

Well- merging two hobbies, found the photocell output for the soundtrack reader and thought it may be an opportunity to plug that into a preamp for higher fidelity. Decided it was a bad idea- for places on the film where the soundtrack area is clear film, I would be presenting DC directly into the preamp and subsequently the power amp. Bad idea, I'd rather burn out the 15w built-in than risk the Phaser. (opinions?).

Here's to equinox and emergence into life!
 
Howdy Mark; I need a 16mm projector. Ebay is my only option here in boonie land. Recommendation's?
My wife was a high school teacher & I grabbed a bunch of cool films when the school was just dumping them.
A lot of early American industry stuff like mining & steel production.

Thanks Brad


Oh...How's the health?
 
Bradrock said:
Howdy Mark; I need a 16mm projector. Ebay is my only option here in boonie land. Recommendation's?
My wife was a high school teacher & I grabbed a bunch of cool films when the school was just dumping them.
A lot of early American industry stuff like mining & steel production.

Thanks Brad


Oh...How's the health?
Click to expand...
Bell & Howell 1500 series- they're indestructible tanks- except for one thing- the worm gear! Every one is guaranteed to be cracked, and it's a royal bitch-in-heat to replace. They're (nylon?) on an aluminum core. You can get replacements, but then you need a set of bristol wrenches and retaining ring tools. Funny that the replacements are much higher quality than the originals. When you get them broken down that far it's a good idea to clean the shutter cam and the shuttle (the pull-down claw) and relubricate. After all that, make sure the shuttle retracts fully to disengage the sproket holes or your film will just go up and down at the gate while the sprockets are trying to pull the film forward. LOTS of adjustments.

I've replaced the worm gears on three projectors. Masochism can be an art...

Avoid the 2500 series- plastic cases, can't get replacement case parts and you don't wanna super-glue them together if you need to replace the drive belt (another bitch-in-heat scenario!).

Eiki bought out B&H, they're slot-load, reasonably reliable (or so I hear, no experience with them...). I have a hard time expecting a slot-load to be unthreadable in mid-reel.

Another goodie is the Singer/Graflex 16, but don't run it in reverse- there's no bottom sprocket and the shuttle pulls the film from the sound drum flywheel, hard on the film. It's a semi slot-load.

Photo: severely cracked worm gear.

DSC_0896.JPG

Photo: how far you have to breakdown to get to the worm gear.

DSC_0893.JPG

Health has been great! A little concern over retinal edema, no worries. A1c has been <7% consistently for the last 2 years, but the pharmacist bitches at me about not refilling my Rx on time. Still need to quit the tobacco.
 
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