Thanks! Trevor for all these great videos! In this vid, you took the time to explain how you converted the original AC incandescent lamps to DC diode lamps. Then you took the time to show how you use ohms law in real life. I will be saving this bid for future reference. Now onto part three for the final conclusion. lol
This thing is really built with design over-engineering I doubt we'll see again in the home audio arena. These 70's pieces are awesome; really appreciate your time sharing this one!
Thanks for watching Craig. It's always amazing to open one of these up and have a look. The attention to detail in design, production and materials can't be found in today's gear
They were built at a time when there were so many possibilities and everyone wanted better quality with lots of options. Music production was surpassing all previous standards and people wanted to experience it for themselves at home and designers were really making a name for themselves by creating highly desirable and stylish equipment ! These pieces were designed to last and be serviced and that is part of why they fell out of fashion, they were expensive, heavy and cumbersome and required a dedicated room or listening space to get the most from them, not ideal for the average living room and certainly not novice friendly.
The folding straw dispenser on the newer D5 spray cans is atrocious, constantly leaking from the folding joint and applying far too much spray with a cap press (xraytonyb goes on a rant about this, and rightfully so). I've found it best to insert a thinner diameter flexible straw/hose into the original rigid straw which serves to neck-down the flow dispensed and provide a means to insert the flexible end easily into just about any location. Your patience and attention to detail is terrific.
Hello, I like how you can explain everything perfectly, even for people who don't know anything about it, you're really busy, you have a lot of experience, they watch you 24 hours a day, maybe :-) Thanks for you !!
@@SDsailor7 It depends. in power supply circuits it's generally ok to bump up the capacitance to help filtering (within reason). In tuned circuits or in timing circuits it's a definite NO to changing capacitance value. That would change the characteristics of the circuit. For signal coupling or DC blocking, it might not be advised to change values because there will be no gains to talk about or it may change how the signal passes through.
I don’t envy you working on equipment as complicated at this. Such a lot of capacitors rather you then me LOL. But great work very impressive thanks for sharing. Best regards Chris
I see that the new big capacitors only have two leads each instead of four. Why do the other big capacitors have four leads each? instead of two like the new ones? anyone know? Thank you
@@TrevorsBench Ahh, something new I did not know, I think you had mentioned that the new ones connected directly to the board I forget the term you used. Thank you for taking the time to answer back
@@TrevorsBenchI recently bought a Pioneer QX 747 and mine has 6 fuses on the power supply board maybe is due to the year it was made. It has one 3amp and 5 1 amp fuses. I already have the receiver looking like yours. Those amplifier boards were a pain to remove! You were not kidding when you said that about the engineers that designed it. Mine also went into speaker protection after about 30/40 minutes of use. I will be referring to this video alot to guide me. Hope you don't mind me asking questions from time to time. Thank you
Hi Trevor.....I have a technical question for you and it is not related to this specific receiver but I think you will know the answer as I watch all your videos. My friend Joe and I are working on a Pioneer SX-828 and have found the left channel output transistors are fried. The transistors are 2SA680 and 2SC1080. What I am wondering is whether I can use MJ15022G and MJ15023G to replace the defective transistors. If not, what should we use. Thanks in advance for your help....Tim Of course we will be replacing both left and right channel transistors.
I am not getting sick of watching the video in fact i find it fascinating! and you explain things so well. So what will happen if you don't set the bias? and the dc balance? will it damage anything or affect the performance of the receiver? anyone know?
DC balance is set to zero to prevent DC on the speakers. We want as little of that as possible. The bias is set to point where the amplifier is happy. Too low and there will be distortion in the signal. Too high and there will be wasted power in heat which can cook components and possibly lead to overheating or meltdown. The bias is measured across the output devices emitter resistor and is usually somewhere around 10mV to 25mV. The service manual will give you the value and procedure for setting the DC balance and bias
Yes, I used 47uF and I installed it back on the lighting board where I mounted the diode. It's under the black plate that protects the dial cord out of sight
I have a QX-949 and I want to remove the faceplate but there are two lock screws on the tuner knob that require an allen key.....when you removed the one on the 747 you are working on, were they metric or imperial allen keys you used as I assume they will be the same? Thanks in advance for your help.
I took your advice thanks and picked up a set of Allen keys that have both but metric it was like you said....thanks, I have new faceplate installed and it is beautiful again. One of the people who owned it before me tried to remove the knob without loosening the screws and bent the shaft and broke the glass. Some peoples kids eh??...lol @@TrevorsBench
Thanks! Trevor for all these great videos! In this vid, you took the time to explain how you converted the original AC incandescent lamps to DC diode lamps. Then you took the time to show how you use ohms law in real life. I will be saving this bid for future reference. Now onto part three for the final conclusion. lol
This thing is really built with design over-engineering I doubt we'll see again in the home audio arena. These 70's pieces are awesome; really appreciate your time sharing this one!
Thanks for watching Craig. It's always amazing to open one of these up and have a look. The attention to detail in design, production and materials can't be found in today's gear
They were built at a time when there were so many possibilities and everyone wanted better quality with lots of options. Music production was surpassing all previous standards and people wanted to experience it for themselves at home and designers were really making a name for themselves by creating highly desirable and stylish equipment !
These pieces were designed to last and be serviced and that is part of why they fell out of fashion, they were expensive, heavy and cumbersome and required a dedicated room or listening space to get the most from them, not ideal for the average living room and certainly not novice friendly.
Really nice that you give a medium line receiver a restoration. Actually in its own way couldn't buy anything close today.
Thanks
You're very thorough! What you did with the volume pot was awesome 🤙
Thank you for your time and sharing with us your expertise 💯💕
Thanks, sometimes we can't find proper replacements and need to work with what we've got
The folding straw dispenser on the newer D5 spray cans is atrocious, constantly leaking from the folding joint and applying far too much spray with a cap press (xraytonyb goes on a rant about this, and rightfully so). I've found it best to insert a thinner diameter flexible straw/hose into the original rigid straw which serves to neck-down the flow dispensed and provide a means to insert the flexible end easily into just about any location. Your patience and attention to detail is terrific.
Thanks, The D5 spray does have it's advantages in some applications but for the most part, I'll stick to using the D100 concentrate
I agree on that D5, it sucks! unfortunately they dont make the old style anymore 😞
Hello, I like how you can explain everything perfectly, even for people who don't know anything about it, you're really busy, you have a lot of experience, they watch you 24 hours a day, maybe :-) Thanks for you !!
Thanks for watching Luke. I try to make my videos so maybe they can be helpful for some one in the future
@@TrevorsBench 😇😇😇🤗
@@TrevorsBench Can you go higher on the microfarads on capacitors like you did? or only on at certain times?
@@TrevorsBench What size are the original light bulbs of the "scope"?
and voltage? will it be in the service manual?
Thank you
@@SDsailor7 It depends. in power supply circuits it's generally ok to bump up the capacitance to help filtering (within reason).
In tuned circuits or in timing circuits it's a definite NO to changing capacitance value. That would change the characteristics of the circuit.
For signal coupling or DC blocking, it might not be advised to change values because there will be no gains to talk about or it may change how the signal passes through.
Hmmmmmmmmmm, like the idea doing a row of caps, doing just 1, then coming back to finish. Did not know that 4 channel Test record existed.
Seems like those solid core wires would snap easily.
I don’t envy you working on equipment as complicated at this. Such a lot of capacitors rather you then me LOL. But great work very impressive thanks for sharing. Best regards Chris
I use finger nail polish remover with acetone in it to remove the glue.
A great device, the only thing that bothers me are the cheap connections for the speakers.
Yes, but remember, this thing was built shortly after Pioneer moved away from those horrid proprietary bladed speaker plugs.
@@TrevorsBench I think the part for that was AKM 003. I have a stereo with those and someday going to rework to something more standard
I see that the new big capacitors only have two leads each instead of four. Why do the other big capacitors have four leads each? instead of two like the new ones? anyone know?
Thank you
Some larger caps will have dummy leads for extra support from the board. They are not connected to anything internally
@@TrevorsBench Ahh, something new I did not know, I think you had mentioned that the new ones connected directly to the board I forget the term you used.
Thank you for taking the time to answer back
@@TrevorsBenchDid you ad heat sink compound to both sides of the clear plastic washers?
Thank you
@@TrevorsBenchI recently bought a Pioneer QX 747 and mine has 6 fuses on the power supply board maybe is due to the year it was made. It has one 3amp and 5 1 amp fuses.
I already have the receiver looking like yours. Those amplifier boards were a pain to remove! You were not kidding when you said that about the engineers that designed it. Mine also went into speaker protection after about 30/40 minutes of use.
I will be referring to this video alot to guide me. Hope you don't mind me asking questions from time to time.
Thank you
NICE JOB TREVOR
Thanks Tina
Paint stripper works good
Do you have a wrapping and un-wrapping tool to remove the wires? Does amazon sell them?
ost of the time i have to fight with the capacitors to remove them.
Hi Trevor.....I have a technical question for you and it is not related to this specific receiver but I think you will know the answer as I watch all your videos. My friend Joe and I are working on a Pioneer SX-828 and have found the left channel output transistors are fried. The transistors are 2SA680 and 2SC1080. What I am wondering is whether I can use MJ15022G and MJ15023G to replace the defective transistors. If not, what should we use. Thanks in advance for your help....Tim Of course we will be replacing both left and right channel transistors.
I am not getting sick of watching the video in fact i find it fascinating! and you explain things so well. So what will happen if you don't set the bias? and the dc balance? will it damage anything or affect the performance of the receiver?
anyone know?
DC balance is set to zero to prevent DC on the speakers. We want as little of that as possible. The bias is set to point where the amplifier is happy. Too low and there will be distortion in the signal. Too high and there will be wasted power in heat which can cook components and possibly lead to overheating or meltdown. The bias is measured across the output devices emitter resistor and is usually somewhere around 10mV to 25mV. The service manual will give you the value and procedure for setting the DC balance and bias
I believe CD-4 needs a compatible stylus to work proper? Does the Pioneer decode CD-4??
Where do they sell those switches that he cleaned and lubricated? anyone know?
Thank you
Did you end up using the 47uF capacitor on the scope, and where did you install it?
Yes, I used 47uF and I installed it back on the lighting board where I mounted the diode. It's under the black plate that protects the dial cord out of sight
@@TrevorsBench Just so I’m clear, I’d attach the positive lead to the pin connected to the diode cathode, and negative lead to the ground plane?
@@djezembarqmail yes, that's right
@@TrevorsBench Thx, and love your videos!
Great video, I appreciate the math on the LED conversion. Can you let us know the part number for those push on push off switches? Thanks
If you go to digikey and search for F4UEE and F2UEE you will see them in both gold and silver plated
I have a QX-949 and I want to remove the faceplate but there are two lock screws on the tuner knob that require an allen key.....when you removed the one on the 747 you are working on, were they metric or imperial allen keys you used as I assume they will be the same? Thanks in advance for your help.
They would be metric, slightly different sizes between the two.
Thanks....when you say slightly different sizes between the two...do you mean the 747 and 949 or the two screws on the tuner knob??
@@TrevorsBench
@@timcorner2821Between metric and imperial. You can't interchange the two because you could strip the hex socket and be in a world of hurt
I took your advice thanks and picked up a set of Allen keys that have both but metric it was like you said....thanks, I have new faceplate installed and it is beautiful again. One of the people who owned it before me tried to remove the knob without loosening the screws and bent the shaft and broke the glass. Some peoples kids eh??...lol
@@TrevorsBench
How do I contact you for a repair on my Pioneer QX747.
I'm not taking in shipped in items at the moment, I'm backed up with work, sorry
@@TrevorsBench Thanks for the reply. Do you know of anyone else that can do it?
HA!...I did the exact same silly mistake with the volt meter....left in current reading, ending up in a short... D'OH!!!
Hahaha. At least the protection was tested and I know it's working
Great, thanks.
Thanks for watching Jan