Phase Linear 4000 Resurrection

[Geezer]

By DCP do you mean a DC protect circuit?
I did buy the board and will put that together too....

I have the stuff, may have paid too much for it so I am going to give it a shot to get working. Probably wont sell for much as is so worth it to try. I do have a DBT, DMM and Oscilloscope. No high DC on the 700 but no sound either!

 

[WOPL Sniffer]

By DCP do you mean a DC protect circuit?
I did buy the board and will put that together too....

I have the stuff, may have paid too much for it so I am going to give it a shot to get working. Probably wont sell for much as is so worth it to try. I do have a DBT, DMM and Oscilloscope. No high DC on the 700 but no sound either!

You are well on your way my friend.

 

[marcok]

I am a relative novice so forgive what may be a stupid question. I did not see it in either service manual.

is there a parts list published for all of the caps on the 4000 preamp?

And also for the 700? Would like to recap both, starting with the 700, it is an early one.

 

[marcok]

I have restored 2 Pl 4000 s and now they work well .
It' possible , but it' a long and boring job.
Your unit is the 3rd version ( ambience instead of SQ logic ) and
many issues were fixed by PL .
Read carefully service manual ( rev 6 -81 ) before starting .
Ciao
Marco

 

[marcok]

To restore a PL 4000 simply follow the famous motto :
divide and conquer !
Start with the minimun config : tone board and logic board .
In this config it's only a line preamp .
Some considerations :
- 1st version of mother board and front panel are a disaster and there
were replaced after S/N 2000
- Caps value is only 35 V before S/N 5000 and after there were replaced with 50V
- After S/N 10000 mother board and front panel board were soldered together
to avoid shorts and bad contact .
- RCA connectors are time bombs and must be replaced in all version
to avoid bad contact and low level distorsion .
Replace with the type with 2 plastic washers and use 2 short wires .
- The relay for switched outlet is undersized and it must be replaced
with a stronger model or you can short the two legs together if
the contacts are still in good condition
At this point , if you have a stable config , insert the other boards and
check every special function .
It's not as difficult as it seems !
The long and boring job is the the RCA connectors.
Ciao
Marco

 

[Geezer]

Thanks all. Marco, been to Milan and what a beautiful city. Will be happy to replace all of those RCA, as a couple are missing and several broken. Great info on removing boards to just leave the basics, was wondering about that.

Just finishing up another project and I"ll be cracking into these.

Still puzzled and intimidated by such high DC on the RCA outputs on the 4000 but we'll see how it goes! Will most likely tackle 700 first so I'll be putting together a parts list.

Encouraging that even though they were hoarded by a repair guy/engineer they appear to be unmessed with except for the addition of the 1/4 inch phono jacks to replace the RCA for inputs as well as being drilled for phono speaker outputs.

 

[marcok]

Read between the lines of the service manual !
There are many versions . I suggest the last : rev. 6-81
For RCA connectors use a type like this : https://anasounds.com/produit/anasounds-sommercable-rca-female-connector-red/
Ciao
Marco

 

[WOPL Sniffer]

Thanks all. Marco, been to Milan and what a beautiful city. Will be happy to replace all of those RCA, as a couple are missing and several broken. Great info on removing boards to just leave the basics, was wondering about that.

Just finishing up another project and I"ll be cracking into these.

Still puzzled and intimidated by such high DC on the RCA outputs on the 4000 but we'll see how it goes! Will most likely tackle 700 first so I'll be putting together a parts list.

Encouraging that even though they were hoarded by a repair guy/engineer they appear to be unmessed with except for the addition of the 1/4 inch phono jacks to replace the RCA for inputs as well as being drilled for phono speaker outputs.

High DC On the preamp RCA output connectors??? That would be amazing since the DC Power supply in the 4000 only makes about 12-15 and we've seen + and - VDC on the IC's at anywhere from 7-12 .The Peak Unlimiter has a couple 30-ish VDC in a couple places. What do you consider "High" DC?

By 1/4" Phono Jacks, do you mean Headphone jacks/Accessory output on the front are 1/4" to drive an amp, or head phones or???? The old 700's (and the newer style 400/700's may or may NOT have 1/4" headphone style jacks already installed on the back so getting the signal from the pre to the amp was easy. By the way, what is a Phono speaker Output

 

[WOPL Sniffer]

Oh, on a side note, pro 700's, some 700 series II's and even a few 700B's had the 1/4" headphone/guitar jacks on the back. I don't have enough exposure to the early 700's to know if they did or not. Since there are 2 sets of RCA's on the back it's possible somebody has done it or maybe even the factory. Once I found out that the early 700's weren't easy to WOPL, I skipped them.

 

[Geezer]

I’ll take some pics to show. I did get a new DMM so I will check with my old one to in order to double check. But I was showing 28 VDC on the RCA outs. Not .28 or 2.8 but 28 Volts!
I will verify with a couple different pieces of equipment and take a pic to show.
Also, the phono speaker outs on this particular ones are not stock… the holes that were drilled are not the way I would like and it is marked with that Dymo tape that was so popular back then… I believe the phono inputs that replaced the RCA were done at the same time.

What does WOPL stand for? I assume I know the PL but WO?

 

[WOPL Sniffer]

I’ll take some pics to show. I did get a new DMM so I will check with my old one to in order to double check. But I was showing 28 VDC on the RCA outs. Not .28 or 2.8 but 28 Volts!
I will verify with a couple different pieces of equipment and take a pic to show.
Also, the phono speaker outs on this particular ones are not stock… the holes that were drilled are not the way I would like and it is marked with that Dymo tape that was so popular back then… I believe the phono inputs that replaced the RCA were done at the same time.

What does WOPL stand for? I assume I know the PL but WO?

White Oak Phase Linear

 

[Geezer]

Crazy... Regarding the 4000, I noticed the 28v on the outputs because to test it I fed a 1k signal into it to test on scope. Then noticed the numbers were strange. Also showed on DMM. Checked again last night, and no longer the case...

No sound passes, but when plugged into scope, does randomly jump around when tapping with a chopstick so will be happy to reflow all of the connections.

 

[WOPL Sniffer]

Crazy... Regarding the 4000, I noticed the 28v on the outputs because to test it I fed a 1k signal into it to test on scope. Then noticed the numbers were strange. Also showed on DMM. Checked again last night, and no longer the case...

No sound passes, but when plugged into scope, does randomly jump around when tapping with a chopstick so will be happy to reflow all of the connections.

I think you were seeing things. They don't put out 28V on the output and just fix itself. What kind of meter and scope do you have. I was contacted by a guy putting my reproduction Sansui amp boards into his 5000A and he said the Bias wouldn't adjust. I got him on the phone and walked him through the procedure and it turns out, his $6 multimeter from China wasn't worth the plastic it was made from. Plus, he really didn't know how to check current with it anyway. You put a 1K signal into it but you didn't say what the amplitude of the signal was.

 

[George S.]

Joe's rule #1, check your test equipment.

 

[Geezer]

Oh, absolutely anything is possible!
The new meter is Fluke 77 (first nice DMM) but just got it so I may have been off in READING it.
The O-scope is as cheap as it gets, bottom of the barrel import. My other DMM is a cheap Amazon, not as cheap as the one they give away at HF, but just a couple notches up.

I am definitely a novice and learning, it is very possible, even likely that I was doing plenty wrong.

 

[WOPL Sniffer]

Oh, absolutely anything is possible!
The new meter is Fluke 77 (first nice DMM) but just got it so I may have been off in READING it.
The O-scope is as cheap as it gets, bottom of the barrel import. My other DMM is a cheap Amazon, not as cheap as the one they give away at HF, but just a couple notches up.

I am definitely a novice and learning, it is very possible, even likely that I was doing plenty wrong.

Yeah, when you are troubleshooting a broke peice of gear and using a broke peice of test equipment, and throw in a couple beers and what could possibly go wrong. I love them Fluke 77's and 89's. stick a battery in them and the run forever.

 

[Geezer]

Yes, I was glad to come across a deal on one... but just a hobby so have been using what I have on hand. Saw Fluke at a pawn shop and seized the opportunity.

But I think it is much more likely operator error (me) rather than the equipment I was using... but having a hell of a lot of fun learning and making things headed for the landfill sing again.

Incredibly rewarding and fun to show off to friends and family that come over. Most of them want one too after hearing and seeing it. Hope to be able to do the same with these PL pieces... but these I am keeping

 

[Geezer]

Was not ready to tear into this yet but had to go sneak a look to double check! This was on both channels but could only hold one at a a time and phone for picture. This is from the preamp out jacks.

 

[WOPL Sniffer]

Take a thousand pictures and it's time to start soldering. As was already posted, wick off the old cracked and corroded solder and get new stuff applied. With the thousand pictures, you'll be able to ALMOST get it back together correctly.

 

[WOPL Sniffer]

you never did answer what the amplitude of the 1K signal you put in was.