Have a QX4000 in need of repairs

[ChopperCharles]

I have a QX4000 that needs repairs. The unit has sentimental value, I know it's not the best out there. I plan to use it for my garage or basement (haven't decided yet), but it was my fathers and he was really dejected when he fired it up after 10 years of storage and it didn't work anymore. I tried replacing the power transistors, but no dice (It's more broken now... before i did that it put out *some* sound).

Do you guys have any idea what could be wrong, or recommend a place I can send it to for repair?

Thanks.

Charles.

 

[mtgc]

Sorry to hear about your problems. This forum has a sub-forum that might have some information that could help you.

Go here: https://www.quadraphonicquad.com/fo...7-Vintage-Equipment-Repairs-amp-Modifications

Good luck,

MTGC (Michael)

 

[geotex]

Those Pioneers are not particularly collectible and lighter-weight (cheaper to ship) than a Sansui, so probably would bee a whole lot more cost effective to buy a working one on e-pay and slide it into your case.

 

[w.a.reid]

if it has nostalgic value - and is a "must keep and must fix" item - as always ...chris ready in PA can and will get it done and right - [email protected]

take care
w.a.r.

 

[ChopperCharles]

I figured out the problem in the QX4000. Something on the muting board fried (keeps speakers from popping when you turn system on or off), and it was never supplying power to the amps. Jumpered output pin to 50v source, and it worked! So I've ordered every part on the board except resistors - which all checked out. New caps, transistors, and diodes. Just going to replace everything on the board (not many parts at all).

I did buy another QX4000 on eBay, and I compared voltages meticulously until I found the problem. The one off of eBay has a bit of an issue with the front right channel though. it's louder and bass-heavy, so I'm going to recap the power amps and either use it in the garage or return it to the eBay ether.

Charles.

 

[ChopperCharles]

So, fixed my QX4000. One of the diodes on the muting board was fried, which prevented the 8v AC sensing voltage from triggering the transistors and allowing power to flow. Had to replace the entire left channel amp board, as my friend pulled up a trace. Whatever transistors he used weren't up to snuff, because all four blew within a short while after powerup. So swapped the entire board out with one from the eBay amp. Now i have an almost perfectly working amp.... it needs the tuner aligned, it doesn't get terribly good reception. (eBay amp got LOTS better fm reception). But hey, I can use it now, and it sounds amazing!

Charles.