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The PM665-VXi refurbish project

wkloppen

Member
Joined
Mar 9, 2021
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Hello Gents,....got my hands on PM665-VXi from Romania. Planning to refurbish it just like 640-VXi and 645-VXi. Threads and pics can by found on this sub-forum.
Measured the DC offset and Idle current and they were a bit off. Luckily you can adjust both DC and Idle on it so after adjustments I got

DC Offset:
CH-1: 2 mv
CH-2: 1 mv

Idle current:
CH-1: 27.8 mv
CH-2: 28.1 mv

So that's the starting point. The amp sounds good but not a immediate difference compared to my refurbished 645-VXi (daily driver). We'll see after the refurbishment:)
Thinking of buying this upgrade set with the nice Nicichon caps besides doing all the swithes, the fusible resistors and probab ly some resoldering as well. At least a nice project for the winter. ...Yes it's still wet and cold in the Netherlands:).
Will use this thread posting pics of the process.....
WhatsApp Image 2023-01-20 at 12.32.06.jpeg


WhatsApp Image 2023-01-20 at 12.41.21.jpeg
Capture.PNG



CU

Willem
 

The Judge

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Joined
Apr 17, 2019
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I have found the PM665 Vxi manual is wrong regarding the bias setting. The 28 mV setting in 8 Ohm mode will not get 50 mV at the check TP´s. You may either set 28 mV in the 4 Ohm mode OR set 50 mV in 8 Ohm mode to get around 50 mV at the confirmation TP´s.
With the 0,27 Ohm emitter resistors this will give 92 mA idle current in 8 Ohm speaker mode.

Compare with the PM665 unit that has 0,33 Ohm emitter resistors and 50 mV setting (75 mA idle current).

HTH
 
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