David's Phase Linear 700B Thread

[Phase Linear Phanatic]

The Huge Hum monster is gone. I have spent the day incorporating Joe's ground scheme at that corner of the amp. I didn't want to do it, but it was gnawing at me. In my last photo here, I show that I cut that white/black/green wire that was connecting from the last triple solder block on the back wall, over to the normal mode/direct coupled switch. Along with a two 220k ohm resistors. My new RCA connectors have a ring with a solder tab that sits flush with the RCA outer shell and against the floating copper plate. I used that tab to add in the 220K ohm resistors as shown in Joe's photo. If you put your face REAL close to the speaker; (and I mean within 1/8 of an inch, you can hear a hum). But its the same hum, if not quieter than my other two factory phase Linear's. So I am ok with this. Now.................to clean up, organize, and get these things fully working.

 

[Gepetto]

Nice Dave, did you delete the Normal/Direct switch?

 

[Phase Linear Phanatic]

Nice Dave, did you delete the Normal/Direct switch?

Lol! No Joe. I just pushed it out of the way to get a clear shot of my work in progress at the floating RCA rail. It's a good thing I ordered spare jacks! I plugged her in to the preamp and speaker wires and all was well. I unhooked it all and put it in that stack to take a picture. Powered it up and got a huge meter swing to the red line then back to normal? The others don't do that. Of course, neither did THIS one before I moved the white wire to star ground on 5L, cut that white/black/green wire that was going into the switch at the ground nut, and deleted the resistors on the switch. And added them to the RCA's? Noting though...... All amps were on infinite load. No connections. Thank goodness no speakers were hooked up? Wonder what I done botched up now?

 

[laatsch55]

Were you in direct or normal when the big swing happened??

 

[laatsch55]

Can't see where the shielding or ground wire from the low signal cables go to the copper bus bar on the RCA's, am I just not seeing them???

 

[Phase Linear Phanatic]

Can't see where the shielding or ground wire from the low signal cables go to the copper bus bar on the RCA's, am I just not seeing them???

Lee, the amp swung while in normal mode. And i took that photo before i soldered the braided signal cables coming from the pots and WOAPL board, onto the floating copper bar in between the RCA jacks. Was trying to get a clear photo of progress befor i did that. I mafe sure that braided wire was not touching anything. Should be fine. Would no longer having two 220k ohm resistors in place at the switch account for this variance? As i stated, i eliminated them and left only the caps on the switch.

 

[laatsch55]

That's a question for Joe. I know if the shield and ground aren't on the copper bus plate and the 220K are, that presents the ground with a lot of opportunities for grounding besides there. Did it do it more than once? Try it two or three times, see if you get the same result.

 

[Phase Linear Phanatic]

That's a question for Joe. I know if the shield and ground aren't on the copper bus plate and the 220K are, that presents the ground with a lot of opportunities for grounding besides there. Did it do it more than once? Try it two or three times, see if you get the same result.

The shield wires are on the copper buss plate. Along with the 220k ohm resistors as shown in Joe's photograph in the last post of the old thread "bulk capacitor replacement procedures". You say "if the shield and ground wire arent on the copper buss plate............" Well what do you mean by the ground wire on the buss plate? Isn't that the solid wire you had me cut a while back? The RCA outer shell is not supposed to be ground is it? Because it is isolated with two plastic grommets between the chasis, then met by the resistors and braided wire. That bar is NOT connected in any other way.

Although what if that shell 'touched' the inner ring somehow of the chassis while going through the holes? That feeds back to the braided wire at the meters and could cause a huge swing? All I know is I did what you suggessted. Turned it off and then back on again. about two times. Both times I got a swing and then BAM. The Left side supply fuses blew up! Both blackened to a crisp!!

Now I'm pissed. I followed my instructions carefully. WT *^$@!

 

[laatsch55]

Welcome to my world. In firing up Lyle's I have rail voltage on the speaker outs, can happen to anybody. Post some pics of the inside again. Let's see what's up.

 

[laatsch55]

Left side ---plus or minus rail??

 

[laatsch55]

Hook your dmm up with the negative lead on the collector bus bar, the positive on the top emotter, tell us what ya get in ohms....

 

[jbeckva]

Allow me to interject here...

Just reminding a few people about this grounding deal with the 700's, and how I went through the same confusion.. I finally said the heck with it and did what I thought worked best, and by golly that's what happened. No hum.. no noise.. nothing.

David - if you do not care about the norm/direct switch functioning and want to bypass it, refer to this post here.. If not, well... I dunno man.

http://forums.phxaudiotape.com/show...ot-Personal-quot-this-time)?p=53969#post53969

In it is the diagram I created and proposed. BUT.. NOTE... what I ended up doing was eliminating the ground plate altogether, so ignore the connections on the far right where I showed (asked) "L/R gnd tabs together and wire to star gnd??".

The whole concept is based on the tip from Joe about how the grounds for the RCA's should float and be totally isolated from the chassis. This MAY or MAY not help you, David with your current issue however - so *in addition*, I would strongly suggest both looking very carefully (again) for possible shorts "in the guts" as I like to call it (maybe you moved an emitter resistor a lil too much... I speak from "experience" there... ). Also do a sanity resistance check with the rail fuses pulled - just a quick check to make sure your mica's on the TO-3's are not compromised. Note the "with the rail fuses pulled".. that is essential to not have false readings.

Disclaimer YMMV... I'm not there.. I don't see your 700 with my own two eyes...

 

[Phase Linear Phanatic]

Just reminding a few people about this grounding deal with the 700's, and how I went through the same confusion.. I finally said the heck with it and did what I thought worked best, and by golly that's what happened. No hum.. no noise.. nothing.

David - if you do not care about the norm/direct switch functioning and want to bypass it, refer to this post here.. If not, well... I dunno man.

http://forums.phxaudiotape.com/show...ot-Personal-quot-this-time)?p=53969#post53969

In it is the diagram I created and proposed. BUT.. NOTE... what I ended up doing was eliminating the ground plate altogether, so ignore the connections on the far right where I showed (asked) "L/R gnd tabs together and wire to star gnd??".

The whole concept is based on the tip from Joe about how the grounds for the RCA's should float and be totally isolated from the chassis. This MAY or MAY not help you, David with your current issue however - so *in addition*, I would strongly suggest both looking very carefully (again) for possible shorts "in the guts" as I like to call it (maybe you moved an emitter resistor a lil too much... I speak from "experience" there... ). Also do a sanity resistance check with the rail fuses pulled - just a quick check to make sure your mica's on the TO-3's are not compromised. Note the "with the rail fuses pulled".. that is essential to not have false readings.

Disclaimer YMMV... I'm not there.. I don't see your 700 with my own two eyes...

I know you're not Jer. And the wifey is fed up with my little project turned "big mess". I can't do 60hr work weeks and then play in the basement for two days then go back to 60's without ignoring her. So we are BOTH out of patience. That's why I am exploring my options to have someone more skilled than I, WITH proper parts and eqpt, look at at. If not to just fix the problem, but to upgrade the rest of the internal componentry as well. And YES this means fixing Mila's work. I don't want it there unless it is beneficial. But I do not have the proper scopes or testing eqpt. Perhaps this is why this amp has been repaired so many times in the past. Based on what I have seen internally? I mean.........The -20db switch was even torn out when I got the thing and wired together and defeated? SOMETHING was bypassed for SOME reason? And if Mila's work has anything to do with it...........then by golly..................it's upgrade time boys. My little hobby is now intended for a more skilled party.

I have a stand in older generation 700B OR a "measily" 400 I can use in it's place. No biggie. I'm just gonna miss my WOAPL upgrades for a while. But it's for the best.

 

[Phase Linear Phanatic]

Gentlemen...................behold the idiot that I am. I opened the baby up and saw a slightly melted green wire near the back of the left channel din rail on the tri-block against the back wall. Follow that over?.........and yep. Leads to the blown Left channel fuses. Did I mention somebody had 8 AGX in there by the way? That's a no-no unless you are running in direct coupled mode or test benching? Yep, blew those to a black crisp. Supposed to be 5 amp. Well.........investigate further and what have we here? A big FAT blob of SOLDER lying right across the left most Driver transistor and the din rail! AHHHHHHHHHHHHHHH!!!!!!!! I cleaned up but didn't see it? Consider it removed now. But no spare fuses? So robbed some 5 AGX out of my PL 400. Still get needle swing upon turn on on the right side though, so damage may have already been done. That's as far as I can go. Sending it out for refurb anyway.

By the way. I have an excellent PL 400 for sale at the moment worked on by ED. If anyone's interested?

 

[laatsch55]

Dave I'm backed up for quite awhile and have a project with Joe coming up. If you want it before the end of the summer, Jer is your man...

 

[Phase Linear Phanatic]

Dave I'm backed up for quite awhile and have a project with Joe coming up. If you want it before the end of the summer, Jer is your man...

Prior to your post, I followed up with Joe on replacing the emmitors. Figuring out the ground scheme, and possibly replacing the transistors. If I have to, maybe he can get a relay protect circuit from Don. I know you all are busy. And that is why I have tried to fix this myself. I'm just not properly trained or equipped. Since a lot of Joe's parts are in there, that seems fitting that with the WHOLE amp at his disposal, he can somehow figure the Mila thing out with the use of his boards? Maybe it will spark a whole NEW debate about Mila Modded PL's? The offer is gracious of Jer. I prefer NOT to delete any switches or bars. Its just the way I desire to keep the amp. Upgraded componentry is all I require. And making it work in harmony with what already existed. Stay tunned folks.......Joe will have his initial weigh in on this in a few days. At least we will have a proper starting point. Then it's anybody's guess where it goes from there?

 

[jbeckva]

The offer is gracious of Jer. I prefer NOT to delete any switches or bars. Its just the way I desire to keep the amp. Upgraded componentry is all I require. And making it work in harmony with what already existed.

And you think I can't do that, why?

Hmmm indeed. Well, good luck with it then. Offer stands for anyone else here in need of a good PLWO'ing. I'll be working on that 400 in the meantime, but that one's almost done..

 

[Phase Linear Phanatic]

And you think I can't do that, why?

Hmmm indeed. Well, good luck with it then. Offer stands for anyone else here in need of a good PLWO'ing. I'll be working on that 400 in the meantime, but that one's almost done..

As stated, you proposed a solution involving removing the switch and ground bars. I do not want to change the design or function of this. You said it was the only solution to your issue? And you also said that if I did not want to do this; that you didn't know what to tell me then? Sooooooo I opted for the man who MADE the boards themself? Now if you have a solution that does NOT involve dissecting the original functions, then please, by all means. The project is yours? Your parts only offer is very generous? I just wanted to be clear about what you stated in solving the ground scheme issue and how I want it to end up? I don't see any reason why Joe's board cannot "play nice" with a tiny switch or rail? That's why you guys are engineers and I am a technician. (With improper tools mind you). Its your project Jer if you can make adequate time? I'm really not opposed? Maybe it's because I am not worthy of your craftsmanship........

 

[laatsch55]

Dave , the Mila mods have to go. They were unreliable and caused pre-mature amp failure.
Jer, do you have a Don's 700 DCP?? If not I'll get one on the way. With 1B05's as outputs your risking taking out a lot more than just outputs. New 21196's are 3.50 each. Cheap[ insurance, plus they are audio rated parts (meaning quieter)
Tell Jer what you want to keep like it is and turn him loose on the rest, you won't get a better deal than that.

 

[jbeckva]

I think you misunderstood me a little. I went into my mod work with my 700's already ripping the switch out because I'm going to keep it in DC mode and any superfluous (again, only to me alone knowing what I am going to do with it) circuitry like the switch would be bypassed - my own "purist" approach on a unit that was mine to work on and I listen to daily. The switch was gone even before completing the build and testing it. I had hum and ground issues even with it out of the circuit, for which both grounding analysis AND taking into account the level controls (again, make sure they are NOT wired with the wiper adjusting the input side) was how it was overcome. Now the "3rd extreme" is to bypass the level controls altogether, but even I haven't been quite sold on that concept.. but that to me is also an option - to discuss and not assume, if you catch my drift.

If I was working on a unit from another owner, and they specified the switch to stay in and function as it should, well there wouldn't be any argument past one quick "Are you sure?" question, explaining the pro's and con's. After all, it's not my amp to make that decision.