PL 400 meters

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calman46

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Hello all, I installed the white oak control board, LED board (needs tweaking ) new PS caps,protection relay kit, and bridge rectifier and output transistors in my PL 400 . Is there a "fix" for the sluggish meters ? I'm using the amp with a pair of Snell CV and a McIntosh C33. The room its in is to small to crank it but the combo sounds great. Thanks
 
If I remember right they are not going to be fast. I could be wrong. Mine aren't quick. What sources do you have? We like to play with sources also. LOL
 
calman, that's just the way they are. They are not "fast attack" and "slow decay".
 
I was hoping maybe there was a fix for it . My Spec 4 VU meters really dance . I have to go back in my PL400 to adjust those LED's ,to get rid of the shadow bar on the meter scale.
I have only use the 400 with the C33 pre and Snell CV's so far . But like everybody else in this hobby I have more than one of everything .
 
I had scanned the meter drive circuit schematic from my Spec 2 service manual and e-mailed it to Joe, hoping he would take the hint. I also like Pioneers approach to meter drives, they appear to me to be very accurate to what i'm hearing.
 
I talked to Joe about the meters also. I understand that it was a poor choice in meters by Phase Linear .
 
The meter drive circuit has at least, if not more to do with their behavior.
 
so its possible? Joe did mention trying a resistor change .I never did it as it was untested . All my emails with him are on a dead hard drive .This all to place some months ago . I might be able to get the hard drive spinning an see what info I have.
 
I think that was to calibrate them to a known level.
 
Hey guys

Sorry, have been busy and missed this thread.

The resistor change can be accomplished but it will change the full scale sensitivity of the meter. For example the PL700B uses a 22K in series with a 1.8K resistor when the meter sensitivity switch is in the 0dB position. When this switch is in the -20dB position then the 22K resistor gets shorted out by the switch and it is just the 1.8K resistor in series with the meter. In the -20dB position, the meters are quite responsive. This shows that the series resistor selection has a lot to do with the visual appearance of the meter response.

The PL400 uses a series 13K resistor. If you do not run you amps at high volume levels then you should find a resistor that is smaller than 13K in value that suits your style. Like the PL700B, I would not be inclined to take this value less than 1.8K. These meters are basically ammeters so unlike a meter that has been set up as a volt meter, the value of this resistor CANNOT go to zero or else you will fry the meter movement windings.

I doubt that anyone on this forum is using the meters for anything but eye candy so the calibration is not important. I have put meter sensitivity charts up on this forum in the WOPL section.

Joe
 
I finally got to this . I used a 6.8K resistors in place of the 13k meter/LED board resistors. With the volume at 10 o'clock the meters do their slow swing thing at the -7 mark. I'm using a pair of Snell CV which are easy to drive and with the volume only at 10 (and its loud now) I think I'll stay safe with 6.8k . Now for the shadow caused by the LED's . It appears most if not all the light comes from the top of the LED . I was thinking about opening up the meter and putting in some kind of reflector above the LED's. I tried putting the LED straight in and it did nothing , but I had to start some where . When I had the board separated from the meters I held a small mirror over the top of the LED's and it lit up the area around pretty good . Can you open the meters ?
 
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Yes, if very carefully handled, the lens assembly snaps off the body of the meter.
 
Make sure you have 2-4 very small straight bladed scewdriver,. When releasing the tangs try and leave the screwdriver in place until the tang clears the depression.
 
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