Phase Linear 700B and 4000 pre amp help

[Gryph0n]

ive had these in the garage for years and was wondering if there is any light or info anyone can shed on these and know where to get easy parts for these to help bring them back to life?

 

[Zach C.]

Lots of stuff out there

carveraudio and thecarversite both have free manuals. stereomanuals sells high quality reproduction manuals.

there is a lot of talk about 700B refurbs at phoenixaudiotape forums.

whiteoakaudio and wattsabundant sell repair and upgrade parts/ kits.

The 4000 doesn't get a lot of lovin' but many folks dig the 700B despite it's rep. for self destruction. I'm pretty new to this gear, but it seems that if you read the manual and FUSE YOUR SPEAKERS, you'll be very happy with them. I own both, but don't have the 700B in my system yet. Just ordered a output (DC protect/ delay) relay kit from wattsabundant. My 700B needs other work too.

Plan on doing considerable refurbishment on both units to get them reliable. Every electrolytic cap in my 4000 was bad, and there's a lot of them.

Zach

 

[Gryph0n]

i hope the caps arent he problem with my 4000. im going to look thru Mouser's inventory but it sucks because they are down he street from me but i have to still order from a warehouse. but thanks on the info. from what i know the 700B is just fuses that i know of

 

[laatsch55]

carveraudio and thecarversite both have free manuals. stereomanuals sells high quality reproduction manuals.

there is a lot of talk about 700B refurbs at phoenixaudiotape forums.

whiteoakaudio and wattsabundant sell repair and upgrade parts/ kits.

The 4000 doesn't get a lot of lovin' but many folks dig the 700B despite it's rep. for self destruction. I'm pretty new to this gear, but it seems that if you read the manual and FUSE YOUR SPEAKERS, you'll be very happy with them. I own both, but don't have the 700B in my system yet. Just ordered a output (DC protect/ delay) relay kit from wattsabundant. My 700B needs other work too.

Plan on doing considerable refurbishment on both units to get them reliable. Every electrolytic cap in my 4000 was bad, and there's a lot of them.

Zach

86 If i remember correctly.

 

[laatsch55]

i hope the caps arent he problem with my 4000. im going to look thru Mouser's inventory but it sucks because they are down he street from me but i have to still order from a warehouse. but thanks on the info. from what i know the 700B is just fuses that i know of

GENERALLY, if a 400 blows a fuse, AND, it is not a violent separation as evidenced by the deposition pattern on the inside of the glass is done from overdriving and doesn't necessarily take any thing else.
Now if a 700 blows a fuse, dont do anything else till you build a Dim Bulb Tester. The failure casade that can happen with a 700 can get out of hand real quick and get very frustrating.

Now , with all that being said, a PL amp can exhibit a positive rail "latchup" to the speaker outputs just fom turning them on sometimes. Due to the unstable nature during power up the bias on Q1,Q2 could go the other way if he output section outran the input section. A drift in values over time, or powering on after an extended time when the caps were VERY dead would also do it. The cure was to power down and back up and hope the residual cap charge could sway the vote.Joe at White Oak Audio has ben studying the weak points of t his design and have addressed these and he's workig on the rest. The original PL folks knew it was happening and to their credit electrolytic cap behvior is undertood much better now than then, they had identified the problem but were unable to cure it, THE REALLY INSANE part, 2-1N4148 soldered in a back to back configuration and soldered to the l eads of C6 on the back of the board(either Joe's or a stock PL 14) solved that conundrum, for good.
Good Luck with your fix Sir, on some of mine that had to be what it was, shitass luck.

 

[Zach C.]

Minor hijack? (or not, really)

...Joe at White Oak Audio has ben studying the weak points of t his design and have addressed these and he's workig on the rest.

laatsch55,

Do you know of a place where there is a round up of design improvements that Joe has done with his new boards? I've looked around and I can't find one. Of course, there's random comments such as you made in this thread, but I can't find a "complete" list anywhere. I was surprised that this isn't on the White Oak site. The site says that it's a great board, but does not go into any detail such as: "changed this aspect of the original board due to...etc, etc."

My board is fine (ish) as far as I can tell so far, and I was trying to decide if this is a "must have" for my amp.

Thanks!

Zach

 

[Zach C.]

86 If i remember correctly.

That sounds about right.

One of these quickly becomes your best friend!

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=372-202

Zach

 

[Gryph0n]

you guys wouldnt know the exact fuses that go into the 700b because i have been given alot of different answers. my dad says 5A AGX and i been told AGX style but i saw on a regular 700 manual (which all i could find) was 8A AGU

 

[Fhamre]

The info is in the manual page 5 and on the back of the unit by the fuse holders. Supply AGX-5 ,Line AGC-10. It says for AGX you can use any fast blow 1" plus or minus 1/8" with the same rating and for AGC any fast blow 1 1/4" plus or minus 1/8",same rating.

 

[Gryph0n]

here are some pictures of the board front and back. i don't know anything or what to look for on this and i noticed the red and blue wires looked like they should be connected to something but i would like some info on this

 

[laatsch55]

The wires not connected to the board are the excess wires not needed for the single channel connection from using a two channel cable. That is a PL 36 board I take it? As that is the only drive board that had an input IC on it.

 

[laatsch55]

Joe's board can replace the PL 36, it takes some good wire grouping habits to do so ,but it is doable.

Fred, the PL's will swallow an AGC IF and it's a big IF------you pull on the tab on the inside of the amp with some VERY grippy needle nose. The 8 amp rail fuses are recommended for sine wave testing as the 5 amps can nusiance blow on the current sharing and protect circuit tests.
Not to mention any square wave testing you may do, and whatever you do don't let your hand slip on the sig generator during square wave testing. I have a sig generator that will output a 12 volt square wave, and when inputted to the 700's with full gain on the volume pots can make a mess of the pre-driver and output section, as I did on Gibsonian's 700. Took me a week to straighten out that mess.

 

[laatsch55]

That sounds about right.

One of these quickly becomes your best friend!

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=372-202

Zach

I have a home-built desoldering apparatus, when i get home I'll post some pics of it. VERY effective.

 

[laatsch55]

Sorry guys, am in Phoenix till the 6th so I haven't been checking e-mails.

 

[d3imlay]

The service manuals are like electronics troubleshooting 101. I've posted them in digital docs forum If you keep the stock boards there are some updates on them.