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Pioneer QX-949A 'Scope" lamp replacement

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BobC63

New member
Joined
Oct 21, 2019
Messages
4
Location
Lehi, UT
Hello all -

I recently procured a Pioneer QX-949A that is in overall very good shape other than needing the usual cleaning and Deoxit treatment.

One issue I have noticed is that only 1 of the 4 "scope" lamps lights up / seems to be operational. For the record, I do get sound to all 4 channels, it seems to just be blown bulbs in the "scope".

Does anyone have any information / guidance on how best to remove the 'scope' mechanism from the chassis? It seems that in order to even replace the 4 light bulbs in the "scope" it must be removed and the bulbs themselves are actually hard wired in place...? YouTube has not been very helpful; a fair number of videos about this receiver but nothing related to scope repair, etc.

My first post here on QQ, and my first piece of quad equipment - been a vintage (stereo) audio hobbyist for a few years now. Hopefully I can get this big beauty back to fully functional, and start enjoying some sweet quadraphonic sounds!
 

BobC63

New member
Joined
Oct 21, 2019
Messages
4
Location
Lehi, UT
Yes, thanks, I actually have already downloaded and printed the service manual out (Was fortunate that the original User Manual came with the receiver). Schematics on it are rather complex, not much guidance on the actual "how to" remove the scope apparatus and access the bulbs. I'm hoping someone here may have actually done this repair themselves and might have some tips..?
 

Circular Vibes

1K Club - QQ Shooting Star
Since 2002/2003
Joined
Mar 12, 2003
Messages
1,575
Location
Ottawa, Ontario, Canada
Looking at page 43 of the service manual seems to indicate that two screws on the left side of scope and one on the top will remove the scope after you disassemble the top wood case, bottom metal plate and removing the face by removing screws and knobs. Then according to page 44, you remove two screws from the front of the scope to remove it from the bezel plate. Page 102 seems to show part number AAw-021, the "4-CH Level Indicator" is a whole unit. the lights appear to be running on 7.5 volts AC. Doing a search on ePay I see sellers using 3mm LEDs in the receiver. I suspect you will just have to disassemble it and see if you can retrofit new grain of wheat 8 volt incandescent bulbs or LEDs. There are a lot of internal parts on the auction site but no 4CH level indicators which leads me to think they go first or at least very commonly.
 

BobC63

New member
Joined
Oct 21, 2019
Messages
4
Location
Lehi, UT
Thanks, that actually helps quite a bit! First time I have been able to see what the 4 Channel Level Indicator looks like disassembled... Right now I am assuming that the level indicator mechanisms all still work, and it's just 3 dead bulbs. Either way, now I can study the indicator unit ahead of time and figure out where to clean it up, how to access the sub-assemblies, etc. before I actually tear into the receiver. Sweet!
 

BobC63

New member
Joined
Oct 21, 2019
Messages
4
Location
Lehi, UT
OK, so I finally had the opportunity to tear into my QX-949A. Disassembly was fairly easy (thanks for the help, QQ!) and I was able to replace all 4 of the 4- Channel Level Indicator bulbs (even though 1 bulb still worked I figured why chance it, change them all). Those little aperature covers, though - Wow, what a real PITA they were. In hindsight, I should have never taken the "scope" apart, and simply unscrewed the lamp board from the back of the scope. Those aperature covers are not much more than paper-thin aluminum, and they literally fall out if you just brush up against them. And a huge pain to put back in properly; each side has a tiny 'flap' that has to be tucked into the aperature motor itself -which is not fixed and constantly moves back and forth with every touch of your finger, LOL.
Anyway, got the new lamps installed, put everything back together... and not quite as good an outcome as I hoped. All 4 lamps are lit in the display - and CHannel 1 and 2 work beautifully now.... but the Channel 3 and 4 aperture motors are not functioning properly. Channel 3 appears to stuck fully "open" (fully lit end to end) and Channel 4 is stuck fully "closed" (center point dot lit but length does not change with VU input). Not sure if stupid aperture covers are perhaps not moving freely (#4), or perhaps came loose and fell off (#3)...or if the little motors themselves are not responding correctly, Has anyone ever actually done any work on those little motors? They look rather complex and, unless someone here tells me they have successfully repaired one... I will probably just leave things alone for awhile.
IMG_6442[1].JPG
IMG_6444[1].JPG
IMG_6446[1].JPG
Do NOT Touch these little sh*ts!!!
 
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