Phase Linear 4000 Restoration

marcok

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#41
Thank for your effort , Ed
Too many discrepancies beetween devices and papers .
Now the situation is little more clearly .
I bet a coffee that the second versions of mother board and
front board were introduced , included new circuit of active equalizer, after S/N 2500.
My father has the original manual supplied with PL 4000 S/N 34xx,
so at this point I dont know what circuit there is inside .
A real big mess .
Any way the most important thing is that the 2 my father's units work well
after recapping , replacing connectors and cleaning .
Ciao
Marco
 

oldphaser

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#42
Marco,

I just acquired an early Edmonds, Washington version of the 4000 owner manual. In it is a single page "Phase Linear 4000 Addendum" I have never seen before which talks about a number of things including the following:

I. "PHONO PLUGS: The phono plugs with extra long center connectors will not work properly with the Phase Linear 4000 unless the following precaution is observed. Squeeze the outer connector slightly with pliers and insert into the preamp jacks 2/3 of the way. These nonstandard "RCA type" phono plugs appear on some European equipment."

II. UTILIZATION OF THE TAPE MONITOR PATH FOR AUXILIARY EQUIPMENT: Equalizers such as the Bose Equalizer should not be inserted into the Tape Monitor path of the 4000. The equalizer must be installed between the preamp and the power amp. This rule applies to any accessory equipment that normally would connect in the Tape Monitor path if the unit: (1) Does not have unity gain, and (2) Does not have flat frequency response.

A tape recorder, a Dolby processor, or a DBX expander may be used through the Tape Monitor path if desired. An active equalizer or a graphic equalizer must not be used through the Tape Monitor path. "If these precautions are not observed impaired operation of the Autocorrelator may result."

The addendum also goes into discussion about "OUTPUT MAIN" as well as "CARTRIDGE LOADING ADJUSTMENTS" for specific manufacture model cartridges.

I haven't had the time yet to compare this to latter owner's manuals to see what parts were incorporated into them.

I wonder if you have ever seen any of these "extra long center connectors" used "on some European equipment". And if so have they caused the RCA jacks to crack or break?

Ed
 

marcok

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#43
Ed ,
the SME 2 male plugs were longer ; you had to shorten them to have
the right ground connection .
In my father's manual it's written and it was a well known issue .
Cracks or breaks are due to fragile plastic and the lateral pressure when you insert
every kind of RCA plugs . ( approx after 20 / 30 years ) .
Furthermore there's another design issue :
the RCA female connectors are not secured to rear panel , but only to mother board .

Ciao
Marco
 

marcok

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#44
Summary of PL 4000 issues found in my father's units ( S/N 3xxx and 4xxx ):
- rear connectors
- difficult cleannig switches
- bad contacts betweeen mother board and front panel board
- bad contacts between peak unlimiter board and mother board
( big board with a little connector in the center )
-caps wrong ( only 35V ; necessary 50 / 63 V) ( fixed after S/N 5000 )
- Pcb board tracks of all boards very fragile .
2nd version of mother board and front panel board is O.K.
Ed ,
can you confirm ?

Ciao
Marco
 

marcok

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#45
Design curiosities ( not issues ) of Phase linear 1st series :
-PL 4000 volume pot is linear .
Carver added a 39 KOhm to modify it in a log pot .
There is also a 56 Ohm between pot and ground . I don't understand why .
-PL 400 ( board 400 C version ) has a cap at the input .
That means that is not a Direct Coupled amp. Why ?
Other board versions has no cap .
-PL 400 sensitivity is too high ( I added a 3 dB att . at aux output of PL 4000 )
-PL 5000 tuner has no hi blend filter ( I added a flat blend filter replacing mono stereo switch
with a 22 KOhm pot , without destroying anything )
Misteries in Edmonds and Linwood .
I introduced these little modifications to have the max. performances .
Furthermore I added a 510 Ohm 5W resistors at the output of PL 400
to avoid thump at the power up .
Only for Infinity RS series or for Watkins woofers , but it' s written on service manual .
Ciao
Marco
 

oldphaser

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#46
Ed ,
the SME 2 male plugs were longer ; you had to shorten them to have
the right ground connection .
In my father's manual it's written and it was a well known issue .
Cracks or breaks are due to fragile plastic and the lateral pressure when you insert
every kind of RCA plugs . ( approx after 20 / 30 years ) .
Furthermore there's another design issue :
the RCA female connectors are not secured to rear panel , but only to mother board .

Ciao
Marco
Marco,

Lots of comments and questions from your (3) posts. It will take a while to reply to them all.

I took a look at my (2) 4000 series 1 (Lynnwood Washington) owner's manuals and indeed they incorporated the comments about the "extra long connectors". However, I didn't see anything about the "UTILIZATION OF THE TAPE MONITOR PATH FOR AUXILIARY EQUIPMENT" as is noted in my previous post. The list of manufacturer's and models under "cartridge loading adjustments" is more extensive in the addendum (noted in my previous post) than Phase Linear had in the subsequent owner's manuals.

Yes Phase Linear had problems with the RCA jacks in the 4000 series 1 preamp as well as the 2000's. By the time of the series 2's they used a different type of RCA jack which had a plastic body and which was also secured with a screw on the back of the chassis. The 4000's that I have seen people add RCA jacks by mounting them to the back panel tend to be a bit ugly. Also a bit harder to service down the road. The original jacks also had shorting capability when not in use. If my memory serves me correct if you take a look at the jacks and the circuit board traces and you will see the inputs have a shorting capability when not in use. The tape 1, tape 2, main and auxiliary outputs do not.

Phase Linear also used (2) different models of RCA jacks. One has a round hump. The other is square.

So how might mounting RCA jacks (like a Switchcraft 3501FR?) directly to the rear panel affect the performance of the preamp? Could there potentially be some ground loop issues if the jacks aren't isolated (say with fibre washers)? Is there enough clearance between the center distance of the holes for any style of RCA jack? Without the shorting capability (or using a male shorting plug) could there be an increase in the signal-to-noise ratio, crosstalk or RFI? I don't know all the answers.

By the way, I have approximately 100 new old stock original RCA jacks. So I am good to go for a while.
 

oldphaser

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#47
Summary of PL 4000 issues found in my father's units ( S/N 3xxx and 4xxx ):
- rear connectors
- difficult cleannig switches
- bad contacts betweeen mother board and front panel board
- bad contacts between peak unlimiter board and mother board
( big board with a little connector in the center )
-caps wrong ( only 35V ; necessary 50 / 63 V) ( fixed after S/N 5000 )
- Pcb board tracks of all boards very fragile .
2nd version of mother board and front panel board is O.K.
Ed ,
can you confirm ?

Ciao
Marco
Marco,

Yes there were problems with the rear connectors (RCA jacks) cracking and breaking.

The early 4000's that used Molex connectors between the front panel pc board and motherboard had issues. Most of these units did not have the slide out bottom cover like the later units had which also made them more difficult to work on. These units had a bottom plate which is one piece with the sub-front panel.

My neighbor Dean stopped working on these earlier units many years ago. His comment was that even if he fixed all the problems he could guarantee that the problems would come back later. As a matter of fact when a customer brought an early unit (less than S/N 1500 or so) he would walk them over to my house and have me trade them a newer 4000 that had already been gone through by Dean and I. I would also give them a $100 credit for their old 4000. Eventually I had a pile of these that Dean would no longer work on. Needless to say, just before I moved from the Seattle area to Connecticut (where I am now) I sold them all as-is on ebay.

Later units after S/N 1500 used 90 degree headers soldered directly between the motherboard and front panel pc board which eliminated the problem. NOTE: Neither Dean or I had any spare 90 degree headers to install.

All of the other 4000's have issues as well because of the Molex connectors between the daughter board and motherboards. The solder joints on all the Molex connectors on the motherboard and daughter (plug-in) boards also need to be redone. Additionally all of the potentiometers and switches need to be cleaned/lubricated.

I hate mechanical connections!

Even though, in general I do not recommend replacement of all electrolytic capacitors in audio components, I would say that with the Phase Linear 4000 series 1's and 700 series 1's (with the PL10171 pc board) and 400 series 1's (with the PL400C pc board) that the electrolytics should be replaced. NOTE: Some brand were better/ more reliable than other. As an example the Nichicon's were among the best Phase Linear used. However the 4000's did use some IEC brand that we had issues with (see service bulletin noted below). The 700 and 400 pc boards noted above used brands of electrolytics that Phase Linear stopped using by approximately 1974 and many of the pcb electrolytic capacitor issues we see today don't appear with the models after 1974. The exception being the 100uF caps when an amp has failed. The power supply caps used in their amplifiers has also been an issue with certain brands as well. As an example, Temple, FAO, and STM come to mind.

The last Phase Linear service bulletin that Dean ever issued is concerning the electrolytic capacitors and is the 6/00 (June 2000) bulletin released on the web site I shared with him. https://web.archive.org/web/20080705234211/http://www.hometown.aol.com/phasetek/capbull.html This bulletin also describes the power supply capacitors and the 50/63 V caps you mention above.

I would recommend for anyone servicing a 4000 series 1 preamplifier that you obtain the 6/81 revision of the service manual.

I haven't had too many problems with pcb traces. Then again I don't use temperatures exceeding 700F or place the tip in contact longer than approx 2 or 3 seconds.


Ed
 
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marcok

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#48
I confirm everything .
For replacing caps ( 80/ 100V ) my hif guru helped me with desold station not to destroy the tracks .
For new rear connectors is sufficient to insert a male plug shorted into phono inputs .
See Yamaha and Pioneer .
Anyway now phono 2 are hi level inputs in my units .
Rear connectors must have two plastic washers , so no ground loops .
Thank you again ,Ed .
The most important thing is that the conclusions are the same .
Ciao
Marco
P.S: we have studied very well the lesson :toothy8::toothy8::toothy8:
 

BlueCrab

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#49
Has anyone come up with a better way to physically stabilize the daughter boards besides using pieces of foam? As long as you don't move them too much, I suspect the current method is okay, but transporting these units must be a nightmare. I'm not too wild about having foam jammed in between boards or between the top and the boards. Particularly as that foam ages and degrades.
 

oldphaser

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#50
When Dean worked on Phase Linear 4000's he would send a set of unpackaging instructions along with the preamp.
 

marcok

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#51
You are right , but I have not to transport my father's units .
Anyway I have an idea ( not tested ) :
use a small drop of silicone or hot glue on the lateral sides of the connectors .
In case of issues is very easy to remove the boards .
You could try with the peak unlimiter board , that is the most critical situation .
First I would test the hot glue .

Ciao e let us know .
Marco
 

BlueCrab

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#52
Following up on my earlier statement that the PL4000 does not have flat response from 20Hz to 20kHz (PL specifications state 20 to 20kHz +/- 0.5dB), I ran a frequency response test on the PL30 Tone Decoder daughter board in my version of the preamp. (Note: I don't have the PL03 Tone Amplifier version, but I suspect the results would be nearly the same). I fed a sine wave into the Aux inputs, measured the signal as it arrived on the PL30 card and measured the signal as it left the board (but prior to the phase decoding portion of the board), so essentially measuring the frequency response of just the op amp circuit that gives control to the Active Equalizer switch on the front panel. Response begins to roll off above 50Hz and is down about 2.3dB at 20Hz from mid-band gain. Both channels exhibit the same performance. This is to be expected given the majority of that roll off is due to the input capacitor to the op amp - C2 & C6, both of which are 0.1uF and give a reactance of just less than 80k at 20Hz. As a test, I replaced these capacitors with 2.2uF capacitor and obtained nearly flat response from 20Hz to 20kHz and would indeed meet the specifications.

I plan to add the missing RC network for the Active Equalizer in the future and run some further tests to see the effect of it in conjunction with the change to C2 & C6.

Below shows my results along with the schematic of that portion of the PL30 card.
 

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BlueCrab

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#53
Marcok,

I've given some thought to your proposal to add some hot glue or silicone to the sides of the connector. The problem is really that the top of the daughter boards are unsecured - allowing the top to vibrate and consequently put stress on the connector and ultimately the solder junctions. Adding glue or sealant at the bottom on the connector will not alleviate the vibration. The top of the boards needs to be secured somehow. As long as the unit is not moved often, this is not a problem. My unit has blocks of foam glued to the top casing and those blocks provide the mechanical securing the boards need. I'm not certain that the foam was installed in all the units from the factory. The foam is a $2 fix; it does the job, but I worry about the long term consequences of this foam as it naturally degrades.
 

marcok

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#54
I consider the foam a bad solution , not only for deterioration , but for me it doesn't work well .
I have suggested to use a " small drop " . Silicone is elastic enough .
Anyway at the first control of my father's PL 4000s I will test this solution on Peak unlimiter board .
Tandberg cassette decks have the daughters boards secured with plastic clips on an inner top panel.
Impossible to use here .
Ciao
Marco
P.S: all 4000s have the foam inside.
 

Gepetto

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#56
Tin plate to tin plate is just a bad connector idea for low level signals. Gold to gold is the norm for low level signal reliability.
 

marcok

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#57
Joe , you are right , but it's only a mechanical solution to secure mother and daughters.
What do you about rhodium ? It's very expansive .
Condider that an RCA female connector ( gold plated ) is approx . 2 € each
and the same in rhodium is 7€ . For me the difference is the number insertions .
Ciao
Marco
 

oldphaser

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#59
I just purchased another 4000 series 1 service manual which I had never seen before.
It pre-dates all the other service manuals I have including the "fast field service manual" which I thought was the first.

The cover states "for serial numbers 1053-2000 thru 1000 forward".
This service manual is 8-1/2" x 14". (I have seen no other Phase Linear service manuals in this format).


Here are a few things I saw in this version....
1.) The disassembly procedure includes photos of an early 4000.
2.) There is some text throughout that is also different than later versions.
3.) Earlier versions of schematics are shown.
4.) "Calibration and alignment procedures" are also different.
5.) There are interconnect schematics and flow diagrams that none of the later revisions have.
6.) It includes some "troubleshooting - service hints" section that the later service manuals also don't have.

I only wish that this version as well as the "fast field service manual" and 6/76 revision and service bulletins were all incorporated into the 6/81 revision.

Someday, when I get a scanner that can do 8-1/2" x 14" (better yet 11" x 17" for my other doc's), I will scan this version and post it.

Ed
 

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