PL700 B planning

Ohioriver

New Around These Parts
Joined
Jan 30, 2022
Messages
28
#1
I posted here the other day and have to say thank you to everyone. I am very excited to have found this community of Phase Linear focused folks! I have been reading and digging into my new to me PL700B. On some levels it may be better than expected when I purchased it. Below is a list of what I have found so far. Please correct any miss statements. I am a mechanical engineer and a car nut, but a neophyte when it comes to electronic repairs. I can repair the visual problems found on a board or component that have smoked, but I am not an electrical component technician like I found with in this community. I have a Fluke MM but no Oscope. Thanks in advance for an and all help.

Good
1. Face plate is nice
2. All UV meters light
3. 700B faceplate lights (2 out of 3 bulbs)
4. All original from a design (some might not see this a good but I think it cool)
5. Orginal RCA 410 CV 514 driver transistors
6. It doesn't appear to have previous board repairs/hot spots
7. Bob Carver Phase Linear 700B Serial Number 3210. Just cool. Anyone know when this amp would have been born?

Bad
1. The output transition are a mixture. Some Fairchild PL909 540 and MJ21194G BM1306 MEX (assuming the MEX is Mexico). I have read that mismatch transistors are bad but don't know what bad means? If transistors are the same ratings why would it matter???? Also some of the F PL909 are 540 and some a label Hong Kong? Are they different?
2. The left channel UV meter bounces when turning on the first time. The right meter doesn't not move when the left bounces that first time. I haven't hook the amp to a speaker yet, so I don't know about scratching or anything else really.
3. I pots are very scratchy feeling. Who knows when they were clean/lude

Unknowns
1. It has Sangam DCM Capacitors 9,800 MFD 100VDC I have not clue what the age would be? What was original cap in these amps?

For some background I have previous owned and loved a PL400. I was always very happy with the sounds. quality and power. I did fry it once in a party environment and buzzed the speakers. I now understand from reading that I was sending DCV direct to the speakers. Those NHT 2.5 are long gone now. I see why there is now a protection relay upgrade.

I am currently reengaging in hifi. I am wanting to plan if I should use this amp (as a 700B) with a little updates or go White Oak. If I go to White Oak do I go full White Oak or just control board. I am leaning towards using it at least for a while as a pl700B and then maybe upgrading. He is the current plan.

Current Plan
1. Test the output transistors and make them all consistent. Is there a recommendation. Should I put back in OLD F PL909 or is there an upgrade before go to the full White Oak back plan. That is above my pay grade.
2. Clean the potentiometer with contact cleaner
3. Replace back light bulbs
4. Install Watts Abundant output protection relay before using them with reference speakers. I may play with some cheap good will stuff.
5. Clean the unit well and start to give it hell!

Please comment on what you all think and see.
 

NeverSatisfied

Chief Journeyman
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Nov 3, 2021
Messages
915
Location
Houston Texas
Tagline
Play the Game, don’t be the Game
#2
Your to WOPL or restore question has been asked many times and from what I have seen the response is almost unanimously to gut it and go full WOPL.
Ultimately it’s really down to your budget and abilities. To me a stock repaired/restored amp is a wonderful sounding amp. From my limited experience the WOPL is a little better sounding but the main advantage is that it is basically a new amp and therefore able to take more rigorous use than an antique. The DC protection board is an absolute must obviously. If, like me you drive vintage speakers at sane levels then a stock amp is more than enough. Having the reliability of a new amp and some sonic improvements are moving me over to the WOPL camp but I will keep some of my amps stock for the nostalgia.
That’s my 2c, regardless which way you go, this great group will help you along the way, enjoy and post the journey.
 

Skratch

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Dec 27, 2011
Messages
1,126
Location
Huntley Il.
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Life is short, so take your time
#3
What you have is a hodge podge of different outputs and sounds like an amp that has gone DC before and was incorrectly repaired. If you plan on keeping it for the long haul I would go full WOPL with the DC protection, if your on a tight budget get a new driver board and 20 MJ 21196 outputs with the DC Protection relay
 

Ohioriver

New Around These Parts
Joined
Jan 30, 2022
Messages
28
#4
The budget is always a consideration, because I hadn't heard of White Oak until the last month. It doesn't seem like upgraded amps are selling well in the resell market. That doesn't mean that it isn't a great upgrade. Although before I drop $2K in a $700 amp I think I would just buy an old Mcintosh. Please don't think I am being contrarian. I also really liked the 400 I had beforehand. Bob Carver has been an "audio idle" for me when I was younger. Twenty plus years ago no-one made any upgrades to phase linear the only option was to repair and replace. Why, replace the control board if it functioning other than new design or components past their life? How ofter has an "good" old original designed PH been a/b tested to WOPL? I just have to plan before I drop $2K in a upgrade that I might not tell the difference.

I do think that this amp hasn't been repaired correctly and that is why I am thinking about "lite restore". Even if I gutted the whole thing I think I will step through the restoration. Is this the right area for restoration questions?

Anyone know if my caps would be original?
 

NeverSatisfied

Chief Journeyman
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Messages
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Tagline
Play the Game, don’t be the Game
#6
The budget is always a consideration, because I hadn't heard of White Oak until the last month. It doesn't seem like upgraded amps are selling well in the resell market. That doesn't mean that it isn't a great upgrade. Although before I drop $2K in a $700 amp I think I would just buy an old Mcintosh. Please don't think I am being contrarian. I also really liked the 400 I had beforehand. Bob Carver has been an "audio idle" for me when I was younger. Twenty plus years ago no-one made any upgrades to phase linear the only option was to repair and replace. Why, replace the control board if it functioning other than new design or components past their life? How ofter has an "good" old original designed PH been a/b tested to WOPL? I just have to plan before I drop $2K in a upgrade that I might not tell the difference.

I do think that this amp hasn't been repaired correctly and that is why I am thinking about "lite restore". Even if I gutted the whole thing I think I will step through the restoration. Is this the right area for restoration questions?

Anyone know if my caps would be original?
I have and am currently doing an A/B test with a 400s2 and have a thread on it. I will be doing the same with a D500. The how much better it sounds is subjective but the WO conversions test better on the bench from what I have read.
I don’t think many on here care much about resale value of their amps, not saying it shouldn’t be a consideration, just that many love the brand, it’s history and it’s sound. There are many fine amps in the $2k to $3k range and you will find believers for all of them. If you can afford the money and have the time, I personally don’t think it would be wasted on your 700 but if your interest in Phase Linear is just minor, then buy whatever pulls on your heart strings and enjoy the music.
 

George S.

Veteran and General Yakker
Joined
Feb 18, 2020
Messages
4,539
#7
I agree. I finally have the Phase Linear system I always wanted. All 3 amps are full WOPL. I learned a lot by building them and will never sell them so it matters not at all what they cost. I have little interest in some of the other brands of gear I have. It's all good gear, just not all Phase Linear.
 

George S.

Veteran and General Yakker
Joined
Feb 18, 2020
Messages
4,539
#9
Oh, and let's not forget Joe and his company WOAD. The man knows what he's doing and produces supurb upgrade kits for the amps. I'm not a audiophile or have owned a lot of different amps, but I have faith my amps will be pounding long after I'm gone. To me a WOPL is far superior to the original due to Joe's design and modern parts. Hell, just pick up a WOAD circuit board and look and feel the quality. The originals and engineering were not that good.
Sitting here now listening to BTO digital files at low volume, just amazingly good sound, no need to turn it up loud to hear it.
 

Geegz

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Messages
349
Location
Atlanta, GA
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---there is no replacement for displacement
#10
I would go full WOPL but if your hesitant to jump in the deep end I would 2nd Skratch’s recommendations but at a bare minimum with the addition of new power caps as well, the outputs on the stock amps are now going on 40-50 years and are very unreliable. If you add up what the minimum parts are your at $600-$800 (approx) depending on if you build the driver board yourself or request one to be built and ready to drop in, and if your planning on installing yourself.

Watts Abundant DC protect board
Pair of new Power capacitors
20 output transistors
20 new sil-pads
White Oak driver board
 
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