Pioneer QX 8000A worth saving?

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steveaustin

New member
Joined
Nov 28, 2010
Messages
5
Hello,
This is my first post on the Quadraphonic Corner and looking forward to absorbing some advice from people with the same interest and passion that I have for these old quads!

I bought a very nice looking Pioneer QX 8000A off of E-bay that was listed as "works great..I am listening to this unit as I write this listing".Well...it did come on and 2 out of the four channels were working!

I took the QX 8000A to an electronics repair shop that was recommended by a co-worker to get an evaluation.Got a call back from the shop and was told that a number of things needed to be done to bring her back to life.First all about 7 bulbs were burned out,no big deal,pots were dirty and needed cleaning,no big deal,tuning dial string needed adjusting,no biggie and then the bad news...the capacitors on the QX boards were dried out and needed replacing.He also told me that it would be a HUGE job to replace the caps in the QX boards and that he would charge around $500.00 to do it.Of course I said no...(kinda sounds like he just didn't wanna mess with it to me).He then said that he could "jump" the two amplifiers with an RCA cable at the tape record and monitor plugs and keep the selector in "2 channel" mode and I would have 4 strong sounding speakers.Well...I agreed and got it back a couple of months ago....been sounding pretty good until last night.
I went to listen to some vinyl and noticed that no sound was coming from the right rear speaker.I checked speaker connections,speaker fuse,changed speakers,with no difference.I turned off the Quad in dissapointment and left the room.I went back several hours later and tried it again.IT WORKS NOW!!!!!...for about 2 minutes and then the right rear channel slowly fades out with distortion and finally dissapears.All other speakers are loud and clear....
Could jumping of the amplifier have caused this?Why has just one speaker on the same side quit playing if the amps are jumped together?
I would really like to keep this quad because when it is working it sounds amazing.I would even consider paying hundreds to get her recapped if that would do the trick.
Any help would be appreciated:banana:
 
First of all, welcome to the wonderful world of quad. You will find this forum chock full of folks with detailed knowledge of all facets of the phenomonem known as quadraphonic sound.

Now, to your QX unit. First of all, I would have recommended that you not have the channels strapped. This almost always leads to problems. If you can, unstrap the jumpers and let the amplifiers work as originally designed. I would secondly have questioned the repairmans conclusion as to the capacitors "drying out". I know caps go bad over time, but the QX had very high quality caps installed and I don't think they could have been all bad.

A bit of background on me. I love old tube electronics and have several tube receivers including a Zenith Walton among others along with a plethora of quadraphonic equipment. One of the tricks we old time tube types use is to reform capacitors. We do this by slowly bringing up the line voltage to the unit in question over a number of days (with the unit turned on, of course). This will usually allow the capacitors to reform and regain a lot of their previous performance parameters. You will need a quality variable transformer capable of handling the wattage requirements of your unit. Plug the unit into the varialble transformer, with said transformer set on about 15 or so volts. Then, over the course of the next few days, slowly bring up the voltage to operating perameters. I have found that this will succeed in bringing back capacitors to operating parameters about 75% if the time. Of course, it is not 100%, but I think well worth the effort, because your repairman was right in at least one aspect, it is a real pain in the posterior to replace all the capacitors in your QX unit.

I am not sure I would spend a ton of money on this unit. Yes, it is a good unit, but you can find better units at reasonable prices with a bit of research on EFlay and other places. Sometimes Forum members will offer up their units for sale.

Again, welcome to this wonderful world of 4 channel sound. I am sure other Forum members will chime in with their opinions as to your situation.

Good luck,

MTGC (Michael)
 
Thank you for the warm welcome and thank you for taking time to answer my post.

Yes...for the record,I asked the repairman if jumping the two amplifier sections would harm another channel one day and he said no.Just my luck....
I believe that I read that you could jump the two amplifiers with a "jumper",but obviously not a good idea in my case.

Well...I have done some research on my QX800A over the internet and talking to repair shops in the area and I believe that I have come to a conclusion....time to look for another reciever.This thing keeps dropping channels and I am scared to put any more money into it,only to have it take a dump again!

I would love to try and fix this unit myself,but I do not have the experience to troubleshoot bad components.I took the chassis out of the wood cover yesterday to have a look.My God....I have never seen so many PCB's and wires crammed into such a small space.I now see the reason for the high cost of labor on these things.

Does anyone have a suggestion for a different Pioneer receiver that would be more dependable and a little easier to work on?

Thanks guys...I'm gonna go put the QX back together and listen to it in 2 channel I guess......someone help!
 
One reason you are dropping channels could be as simple as dirty contacts in your switches. Give all he pots and switches a dose of De-Oxit and see if that helps the problem. Don't give up on this unit yet, these things were built like a battleship.

MTGC (Michael)
 
Michael,

I think I found something that is linked to the problem....tell me what you think.

Like I said,the right rear channel cuts out after about 2 min. of play from completley cold.After the channel faded out listening to the QX a while few minutes ago I started messing with the controls like you suggested and when I got to the rear bass knob and touched it alot of static in the right rear speaker.The right rear speaker ONLY.I can get the right rear channel to work for a few seconds by turning the rear bass control all of the way to the left and wiggle it a little.The left rear speaker loses it's bass when the bass knob is turned to the left but there is popping in the right rear ONLY and then after a little wiggling...music from right rear!

What do you think...could it be just that there is crud and build-up in the rear bass control....or could there be something on the tone control board that is faulty.Is the bass control "stacked"?I guess what I am trying to ask is.....is there two separate riostats in the bass switch...one for the left side and one for the right....that is the only reason that I can think of that would allow the bass to be controlled on the left rear speaker while the right rear speaker crackles and pops when the knob is turned.

Please let me know if I could possibly moving in the right direction.

BTW...I took off the amp "jumpers" and I just switched the intercouple switch.....I am confused as to why the "repairman" put them on there in the first place....everything still works the same....

Steve
 
I absolutely believe you are moving in the right direction. Get yourself a can of De-Oxit (From EBay or other sources). Turn the unit off and give all your switches and controls a shot of this contact cleaner and work the controls through their entire range several times. Let the unit sit for about 15 minutes and then turn it back on. I am willing to bet that you will see a remarkable difference. As further info, sometimes it takes a couple of doses of De-Oxit to fully clean really grimed up contacts, but usually a single application is sufficient.
Good idea also to remove those jumpers. Also, it is not a good idea to place this unit in "double stereo". This essentially stacks the four amplifier boards into stereo operation and there have been reports of this setup damaging the amplifier boards.
Rheostats in this unit are stacked. When you get the cover off so that you can see them, you will see the stacking arrangement. There is a small opening in all these potentiometers where you can place the De-Oxit tube to get the cleaner inside the pot. Also, the switches have the same arrangement, but you really have to look closely in some cases.
Good luck and let usnow how you are progressing.


MTGC
 
I will also just chime in here to encourage you to keep at it.

It sounds like you are on your way to getting it funtional again. DeoxIT is wonderful stuff.

Doug
 
Deoxit it is! I had a feeling that mr. repairman did a "quickie" on my QX! Although he did get all of the scratchy out of the pots,but now it is time to make them function correctly...
I beleive that this unit came from a smokers home.The dust that has accumulated on the chassis and some of the parts have a yellow nicotine color to it.This may be why the pots are such a pain to clean....dust and tar!
Thanks guys for all of the help and encouragement! This is the next best thing to having someone over your shoulder....which is a great thing in this situation!
Jumpers are gone!Not sure why you would want to "double stack" amps like that.The "repairman" that I used is lucky right now.....I moved from central US to the North East....:howl
Steve
 
I have cleaned up more than my share of units from smokers homes and they invariably are coated in a mixture of oily residue and dirt. Can you imagine what that crud must do to the human lungs?
You will probably have to go multiple cleanings to get all that crud off. I have found that goof-off works well and doesn't seem to damage the finish of parts being cleaned and for electronics, of course De-Oxit.
Once you get this unit cleaned up, you will probably want of get a bottle of lemon oil and give the wooden case multiple doses. This will prevent splitting and will also hide imperfections and make the cabinet look a lot better.
Please keep us updated as to your progress.

MTGC
Michael
 
"He then said that he could "jump" the two amplifiers with an RCA cable at the tape record and monitor plugs and keep the selector in "2 channel" mode"

This is strapping the amps?

I have a QX-8000A and I'm interested if someone could explain how to do this? How does jumping the tape record and monitor plugs strap the amps together?

I understand strapping can cause issues but is this a proper strap? Or is it a hack?
 
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