Pioneer SA-508 - Fluoroscan Tube Giving Up Ghost?

[Machineghost]

Hi there folks!

I have a Pioneer SA-508 Amplifier here with me with an odd problem.

Recently a friend of mine asked me to check out her Pioneer stack as the tuner was acting up. I brought all over to my place and did the usual service. Afterwards I fired up the gear to check the function. Tuner - OK... Amp... NO-KAY.

On the amp the audio is 100% but the fluoroscan meter is giving me grief.

The right channel segments of the tube only "fire up" when the amp pushes past 0.3 on the scale. I have jiggled the pots, checked the caps, measured the voltages with no remedy.

What can be the fault?

 

[markthefixer]

What you need to do is see whether or not the segments are being told to turn on (voltmeter readings).

Mono operation is your friend here... then compare what's coming out of the signal preconditioner IC TA7318.

It could be the comparator IC, or the signal preconditioner IC feeding garbage to one side.

I assume you recapped the display board.

There should be other markings between the left (lower) and right (upper) bars, so if the tube is having problems, these other markings should also be affected.

Basically, if I were really motivated, I would swap the two comparator/driver IC's (ha12010) and see if that made a difference.

 

[Machineghost]

MTF...

Well, I did check all the caps and all is 100%. Signals from amp section is also both 100% using a 1kHz sine signal on both channels.

Signals from Q1 is both balanced so no problem there. Must be a comparator then. Swapping them? I dont think so... I am scared that I'll f&*%k up the PCB as the tracks lift easily I have found.