PL 4000 issues and solutions

marcok

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Joined
Jun 9, 2014
Messages
988
Location
Milan Italy
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I'm very curious about any tech item
#1
1) serial number
2) new connectors
3) Phono 2 Riaa inverter circuits
4) wrong pcb on volume pot ( this causes bad contacts and shorts between mother board and front board )
Fixed with an isolation paint for pcb
5) internal wiring of new connectors

I hope it could be helpfull .

Ciao
Marco
 

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marcok

Chief Journeyman
Joined
Jun 9, 2014
Messages
988
Location
Milan Italy
Tagline
I'm very curious about any tech item
#3
No , me !
My guru made the recap , since it's necessary to have a desoldering unit not to destroy the pcb tracks of the boards.
( they are very fragile ) .
Furthermore he helped me to understand how to fix bad conctacts between mother board and front panel
and how to clean the switches .
I changed all the RCA s , I added the RIAA inverter on phono 2 and an attenuator on Aux outputs to drive
PL 400 .
I made these modifications on two units .
Ciao
Marco
 

marcok

Chief Journeyman
Joined
Jun 9, 2014
Messages
988
Location
Milan Italy
Tagline
I'm very curious about any tech item
#4
It must be noticed that that problem of the pot was known from Phase Linear .
I have the first release of service manual of PL 4000 , where it's written :
"In case of bad contacts check the connector expecially near volume pot ."
In the second realease (ncomplete ) ,the only that you can find in the web ,there's no evidence of this issue ,
but they speak about a wired version of the connections between mother board and front panel board .
( never seen ). At the the begining you think about the switches , but moving them you push
the male connector located on front board . It took me and my guru much time to understand this issue .
Another critical point is the connection between the peak unlimiter board and the mother board ,
due to the little connector put in the center of this board . Infact they used a piece of sponge ,
located on top cover , to lock it .

Ciao
Marco
 
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