I want to White Oak a Phase Linear 700B

[ksrigg]

Now I have the bright idea of attempting the re-build of a Phase Linear 700B. I recently bouht in on eBay for the Buy It Now price of $450.00. I think it was a really good price and it stayed up on eBay with no takers for several days. I just couldn't stand it, and pressed the But It Now buttton.

Anywy, cosmetically it is in very good condition. I'd give it a solid 8...probably a 9 if you look inside the chassis. Most of the red marks are present on the majority of the solder connections. I'll let you all be the judge. Below are the pictures. It was produced on October 13, 1973. I just hope it wasn't a Friday.

I would appreciate any comments on the amp. I plan to install all the available upgrades and replacements. Jo is building a Rev C PCB and a LED board. Lee has provided me with some storage caps....(look at the ones in the amp) and I have emailed Don about the DCP for this amp. I also have, or have ordered from Mouser, all the driver and output transistors, BR, by-pass csps for the R, gold plated RCA'sand all the other stuff I am forgetting.

Below are pictures....let me know what you think. Encouragement is good I finally got a 400 to work after doing the conversion on three 400's. I gotta get this on right the first time.

 

[ksrigg]

And some more....................

 

[Gepetto]

Looks like you got a couple of spare rolls of masking tape to boot Sutton. Wrapped around those replacement caps

 

[mlucitt]

Yes,
It looks like almost all the electrolytic capacitors have been changed. also some of the small signal transistors. What were the driver and output transistor types?

Mark

 

[laatsch55]

From where that ceramic is on the foil side she might have been an oscillator.

 

[laatsch55]

What's with the zoebel network on the backwall??

 

[laatsch55]

With the ZN there it is was bypassed to chassis ground instead of output ground first. I don't think she was real quiet.

 

[Gepetto]

You don't see too many 700Bs with the 14A board in them.

 

[laatsch55]

Nope, looks stock too , when ya look at the board tie in puddles.

 

[laatsch55]

No stranger to a hack is she?

 

[Gepetto]

That is the second PL17A board I have run into within a week as well. The -20dB wafer switch needs to be have the wiring slightly altered to work properly with the White Oak light board. It is reverse of the PL17 board. An easy wire swap.

 

[ksrigg]

I'll get the details on the transistors in the morning, but they are all RCA drivers and Phase Linear outputs. Two of the 180ohm resistors read bad, several fuses fried, and the drivers associated with them have a black X marked on them along with an output or two. The loooong caps were 120 volt caps. I'll get some more pics of the transistors etc. tomorrow as well. The amp is super clean on the inside.

 

[ksrigg]

The Zobel network you are talking aobut on the back wall, Lee...........is it the two maroon resistors and teal colored capacitor? Would I simply remove it from the circuit in it's entirety? And Joe, what will jneed to be changes for meter attenuation switch? Reverse some wiring at the PCB? I will be using the PCB you are making for me...the Revision C one..Anything else that anyone sees which needs to be removed or changed?

 

[laatsch55]

Yes it is those 2-ten ohm ,3 watt resistors and the teal colored capacitors. Don's board has em built into it so they can go. What are going to do with the old board??? I use them for trading material for otherwise unobtainable Phase parts.

 

[ksrigg]

There are two Zobels...One between banks one and two and one between banks three an four on the bakwall. I just desolder or sut them out. right? There is something at the inputs as wel. Looks factory, but what is that? Having not seen Don's DCP for a 700B, I'm guessing they fit on the top of the four speaker post like the one for the 400?

The old PCB is yours..I'll send it out as soon as I get the one from Joe to replace it. Any other mods for the Rev C board, or guinea pigs needed?

Oh, someone asked about the drivers and ouputs...they are RCA 410 for the drivers and Phase Linear branded..XPL909 7335 for the outputs. What are they really? The storage caps are (were) Philips 9,000UF 125 VDC and 1 3/4" X 5 7/8". Will the 35,000UF 125 VDC ones from Apex, JR. throw circuit breakers in the house, or will they be useable? I know they are almost double the capacity of the 20,000 UF ones I got from you, but could a person tell (hear) the difference? Steve also has some 8,000 UF 100VDC snap-ins for something like 3 or 4 dollars each. He swears they are actual brand name. I'm going to probably get a few for use ina 400 down the road sometime...How can you tell if they are name brand or knock offs? I may be able to post a picturs sometime, and Joe, throw in a couple of pairs of Experimenter's Kits for the 400 capacitors..I'm going to get eight of the snap ins...

 

[Skratch]

Looks like they put the zobel network between the output banks instead of on the speaker terminals. Also Sutton I would put two .33uf 200 volt film caps from the B+ to ground and the other one from B- to ground on that 3 terminal strip between the right output bank

 

[soundude]

ksrigg, if you go to my 700B adventure, I have pics of my 700B with Don's DCP board and Joe's board and Alex's jr's adcom caps..lee suggested to also replace the BR with a 35A but all I could find in my area was a 50A same size as the 35...Just so you know you could have fuse problems when you cycle the 700 on from when the caps drain...always popped the ten amp so wound up using a 8a delay fuse not a slow blow. the inrush gets over 30amps charging those caps... hope you are doing a total reconstruction of that amp...worth it!!

 

[laatsch55]

Sutton , those XPL 909's with a date code of 7335 means they were Delco DTS 411's built in the 35th week of 1973.
Post a pic of the caps and we should be able to tell. 70,000 uf should not trip a 20 amp breaker, there is enough delay in a commercial breaker to ;last through the charge up, but as Johnny D has said the mains in fuse may have to be dealt with differently.

 

[laatsch55]

Looks like they put the zobel network between the output banks instead of on the speaker terminals. Also Sutton I would put two .33uf 200 volt film caps from the B+ to ground and the other one from B- to ground on that 3 terminal strip between the right output bank

+1

 

[laatsch55]

The reason I begged for the board is I have an ongoing deal with ED Blackwood for all the old PL stuff we replace. That's how I got the original power switch, and it's our fellow members who benefit, I have plenty of parts.