Hi to all and good evening. My name is Allan and I love stereo gear mostly antiques. I have a small collection not much . But love them.
I have a pioneer a-9 which gives the random loud pop sound on the left channel . I feel sure it could be the 5 legged differential input transistors in the equalizer board . I twisted wiggled all PCB boards to find a loose connection . Opened the system from below as well so I could see all solder clearly visibily .
I read many forums . Most common problem of them are related to differentiatial input transistors on the equalizer board . But it could be anything.
I plan on changing the differential input transistors. Before that I have a question . Would this affect the bais settings in the system as if that's disrupted other failure could happen .
Appreciate the help .
I have a pioneer a-9 which gives the random loud pop sound on the left channel . I feel sure it could be the 5 legged differential input transistors in the equalizer board . I twisted wiggled all PCB boards to find a loose connection . Opened the system from below as well so I could see all solder clearly visibily .
I read many forums . Most common problem of them are related to differentiatial input transistors on the equalizer board . But it could be anything.
I plan on changing the differential input transistors. Before that I have a question . Would this affect the bais settings in the system as if that's disrupted other failure could happen .
Appreciate the help .
Before you change any parts, it may be worthwhile to re-solder some components. Just a quick touch up.
Ok that sounds good too . Will have to take off the equalizer board anyway . I did wiggle the 5 legged input transistors while the pop occurred . But then I wouldn't pop . Everything seems firm . But I will take into consideration resolder.
Thanks adason
Thanks adason
Other option is old leaky capacitors...
I generally do not see the reason to replace active part unless its broken.
I generally do not see the reason to replace active part unless its broken.
How would one know they are leaky ?. Would the top look expanded sort of like even a bit ? I did check all capacitor s. They seem all well flat on their tips . No sign of leakage . The bass and treble control board as well as the other balance control board seen very greasy and dirty . It's like oil grease and black dirt mixed . It's strange only on those boards it's greasy . The entire PCB and everything on it for those two board only is greasy and dirty . I feel it's impossible to clean . But I am sure that is not the cause because there is an option called " line straight " when u put this button on the bass treble and balance cannot be used . It's like direct sound . But still the problem persists . I don't know why those two boards are dirty and greasy . The other boards are dirty too but not greasy and dirty
+1
exactly the same trouble with a hk citation 24 .
i checked all transistors with no result and i finish to find 1 capacitor in perfect
visual condition but fully leaky to the lcr meter ...
That's good to know . I will check the capacitor s through a multi meter and keep posting results . Thanks allot
Electrolytic capacitors contain fluid electrolyte, sealed only with a rubber plug. Thus they have a limited life, only guaranteed for a finite period at their rated maximum duty which is typically only 1,000- 3,000 hrs. In many applications though, the duty is light, occasional or the product may be unused for decades. The life of the cap then becomes simply related to age and possible damage to the "forming" of the anode by abuse. Commonly, after 20 years they begin to fail with some degree of predictability. After 40 years, good quality types may still be OK but from a service point of view, it's then high time they were all replaced.
Two meanings of leaky caps; physically leaky, as in electrolyte leaking from the lead exits, or around the rim, then electrically leaky, as in passing some DC current when there is an internal fault. If you want to know all about components and failure modes, Wikipedia is there. This reference is really comprehensive and helpful: Aluminum electrolytic capacitor - Wikipedia . BTW, you can't test caps with a simple multimeter!
Cheapo parts testers you find in the dozens on Ebay are not suitable for testing large capacitors. You can buy a real ESR meter and learn how to use it to save money on caps over several projects but not worth the expense for only the odd need. Once you know the duty and age of components that have limited life, the decisions are simpler anyway.
The A9 amplifier was produced around 37 years ago so you can see that there is a fair chance of capacitor problems unless someone before you has already addressed them. As implied in Adason's suggestion, the soldering on mass produced PCBs can be bad right from the start. It may not become a problem until many years of thermal cycling have taken place but intermittent faults like noises and dropouts are legion. A dab with the iron and maybe the tiniest spot of 60/40 flux to connections on the PCBs is easy. If you know the general location of the fault, it doesn't take long either.
I couldn't say what the greasy layer on the PCBs is, but it seems likely that someone before you may have tried to fix the problem with "the mechanic in a can" or just the wrong type of service product that left a deposit behind. A greasy film may also darken by absorbing airborne dust, soaking into the phenolic board etc. You could try a relatively safe solvent like isopropyl alcohol or methylated spirit with a small wipe test first so petroleum based grease/oil deposit will require a related solvent like white spirit but this could also soften the print which identifies the components. Test first.
Needless to say, using flammable solvents in the home, particularly an air conditioned one or an apartment, is a no-no nowadays. Consider your circumstances and experience before trying something out of your comfort zone. PCB cleaning can also be done by scrubbing with hot water and strong detergent but this requires disconnecting the boards, removing, and fully drying afterward. Sometimes this can't be done without unsoldering leads but make a sketch of where they connect first.
Pray that there's no problem with the input dual fet(s). There are expensive pulls and fakes around but any you see on Ebay are unlikely to be genuine parts though they may seem to function acceptably. The issues are not only parameters like Idss but the match between the devices. That's what makes genuine parts essential even if unobtanium. If you have sound, don't touch without a very good reason
Two meanings of leaky caps; physically leaky, as in electrolyte leaking from the lead exits, or around the rim, then electrically leaky, as in passing some DC current when there is an internal fault. If you want to know all about components and failure modes, Wikipedia is there. This reference is really comprehensive and helpful: Aluminum electrolytic capacitor - Wikipedia . BTW, you can't test caps with a simple multimeter!
Cheapo parts testers you find in the dozens on Ebay are not suitable for testing large capacitors. You can buy a real ESR meter and learn how to use it to save money on caps over several projects but not worth the expense for only the odd need. Once you know the duty and age of components that have limited life, the decisions are simpler anyway.
The A9 amplifier was produced around 37 years ago so you can see that there is a fair chance of capacitor problems unless someone before you has already addressed them. As implied in Adason's suggestion, the soldering on mass produced PCBs can be bad right from the start. It may not become a problem until many years of thermal cycling have taken place but intermittent faults like noises and dropouts are legion. A dab with the iron and maybe the tiniest spot of 60/40 flux to connections on the PCBs is easy. If you know the general location of the fault, it doesn't take long either.
I couldn't say what the greasy layer on the PCBs is, but it seems likely that someone before you may have tried to fix the problem with "the mechanic in a can" or just the wrong type of service product that left a deposit behind. A greasy film may also darken by absorbing airborne dust, soaking into the phenolic board etc. You could try a relatively safe solvent like isopropyl alcohol or methylated spirit with a small wipe test first so petroleum based grease/oil deposit will require a related solvent like white spirit but this could also soften the print which identifies the components. Test first.
Needless to say, using flammable solvents in the home, particularly an air conditioned one or an apartment, is a no-no nowadays. Consider your circumstances and experience before trying something out of your comfort zone. PCB cleaning can also be done by scrubbing with hot water and strong detergent but this requires disconnecting the boards, removing, and fully drying afterward. Sometimes this can't be done without unsoldering leads but make a sketch of where they connect first.
Pray that there's no problem with the input dual fet(s). There are expensive pulls and fakes around but any you see on Ebay are unlikely to be genuine parts though they may seem to function acceptably. The issues are not only parameters like Idss but the match between the devices. That's what makes genuine parts essential even if unobtanium. If you have sound, don't touch without a very good reason
Great insight Ian . Yes I just counted the years the other day . Around 37 years . It's come a long away for this system as well as all the other antiques in the world .
I plan on working on the bass treble PCB and the balance tone PCB as they are drenched in the oil along with dirty . I suspect the technician may have spilt something on those boards by accident . Because I know how clean my system is from the insides and it funny how only that section is Oily . I had uploaded a video on youtube where I was manually trying to create the pop sound by adjusting the bass control knob only . (It does not happen when I adjust the treble and balance control just the bass )
I am willing to desolder take our the boards and do a thorough cleaning . Do you think when oil seeps in the controls that random pop can occur ?
YouTube
I am willing to desolder take our the boards and do a thorough cleaning . Do you think when oil seeps in the controls that random pop can occur ?
YouTube
I don't recall anything as bad as contaminants seeping into a pot. but I doubt that's the problem. Simply operating the controls would tell you from the mechanical wiping noise produced, if there was a bad contact or potential noise source in there. A tone defeat switch (I think it's called Line/straight on this model) eliminates the tone controls so, given that you operated the bass control to induce the noise, see what happens when there isn't a bass or any tone control in circuit. It does point to the tone control circuits and possibly some coupling caps in there but I need to study the schematic.
The video your link took me, was by Aiden.M. and dated 1st of Feb. Was that correct? It shows a pulse of signal with each operation of a the source selector switch. However, that's only when the bare shaft was gripped - not when a knob was fitted. That means the pulse of noise was conducted to the sensitive signal input circuits by the operator. Other than the grounding method of the switch hardware there, It may not be much of a problem at all.
Another video shows pulses following the switch or other control operations after a delay of a second or so. That's not random but likely related to signal coupling, decoupling or power supply caps in the various preamplifier sections.
A truly random noise problem does need specific details and help from instruments like an oscilloscope to help narrow down the location. Often, the closer you get to a fault, the easier it is to see but don't assume that because operating a control induces a fault, that the control is faulty - that would amount to shooting the messenger.
The video your link took me, was by Aiden.M. and dated 1st of Feb. Was that correct? It shows a pulse of signal with each operation of a the source selector switch. However, that's only when the bare shaft was gripped - not when a knob was fitted. That means the pulse of noise was conducted to the sensitive signal input circuits by the operator. Other than the grounding method of the switch hardware there, It may not be much of a problem at all.
Another video shows pulses following the switch or other control operations after a delay of a second or so. That's not random but likely related to signal coupling, decoupling or power supply caps in the various preamplifier sections.
A truly random noise problem does need specific details and help from instruments like an oscilloscope to help narrow down the location. Often, the closer you get to a fault, the easier it is to see but don't assume that because operating a control induces a fault, that the control is faulty - that would amount to shooting the messenger.
Yes you're right . Both those videos are the ones I posted . Yes correct you are . That makes sense .the bass control is not the culprit. The issue is definitely seen in other video , where there is randon static pops without touching the system much . That's true I will have to Trace the problem study the schematic.
Tapping to the top of the capacitors, with unit powered on, worked for me... 😉
Anyway, IF you love so much your old units (as I do), replacing critical capacitors for better ones will make a big difference in sound.
Best wishes,
M.
Anyway, IF you love so much your old units (as I do), replacing critical capacitors for better ones will make a big difference in sound.
Best wishes,
M.
Thanks maxlorenz . I did tap most of them . Not all though . . I tried some weird stuff today . I kept the unit in the sun for about 10-15 mins . Took it back in the house and powered it up . It only made a static pop after about 20 mins and it's been on for like 5 hours now . No pops . Then I switched it off . I cooled it down with the air-condition drift over it . And then powered it up again switched off the AC . Ran the system for 2 hours no pop sound came . Note it wasn't very hot sun rays. But it was hot. I know I am doing some ridiculous experiments . . Happy Easter .
I really wouldn't mind getting a freeze spray . But on Amazon here it's like 53 USD and some are even 63 USD . With that type of money I can send it to a tech and get the problem fixed and it would cost me less than 16 USD . That is hopefully if it does not involve the output transistors cause those are expensive to change along with labour . Had them replaced once .
How much are frreeze sprays supposed to cost ? I find it difficult to find in stores here . The system seems really silent. Not a single pop since I had placed it in the sun today for 15 mins with direct sun rays hitting it . Of course it was with the cover on . Yesterday the pops were very frequent. After intervals of breaks every time I used to switch ON the system within 3-4 mins statics and loud pops 3-4 times then randomly after half and hour then at anytime later. This is how I test the system . I run it for an hour and switch it off . Let it cool after one hour again repeat the same process . Today for some reason it's not there . These things are just unpredictable. Still waiting for that random pop to occur. I know it is there . I take lots of time in testing . I am never in a hurry to change parts which may not necessarily be the culprit . Dont know if that is a good thing .
How much are frreeze sprays supposed to cost ? I find it difficult to find in stores here . The system seems really silent. Not a single pop since I had placed it in the sun today for 15 mins with direct sun rays hitting it . Of course it was with the cover on . Yesterday the pops were very frequent. After intervals of breaks every time I used to switch ON the system within 3-4 mins statics and loud pops 3-4 times then randomly after half and hour then at anytime later. This is how I test the system . I run it for an hour and switch it off . Let it cool after one hour again repeat the same process . Today for some reason it's not there . These things are just unpredictable. Still waiting for that random pop to occur. I know it is there . I take lots of time in testing . I am never in a hurry to change parts which may not necessarily be the culprit . Dont know if that is a good thing .
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Thanks for that . I have some new update .
I switched my speakers to the speaker B out . Most of the time it was connected to speaker A on the amplifier . I am aware both these relays have separate relay boxes . Am I right ? However the pop sound is same on speaker B as well . But speaker B has another small issue . So I played a piece of music through speaker B as my speaker wires were connected to B . The music sound dint come until I raised the volume a little higher . So on low volume levels that is less than moderate the left speaker sometimes gives no sound and at very low volumes both speakers don't give sound . Only when I raise the volume little higher then music sound comes out of both speaker or else it just not getting the signal even though the speaker B button is ON .
Do you think my suspect is the speaker relays regarding the pop ?. But if the speaker relays have separate boxes how is it possible both boxed relays give the same pop static sound only on the left channel which occurs randomly?
I also noticed one thing . Leaving the system OFF over night about 8-9 hours then switching it ON in the morning the loud pop occurs immediately after 1 min of power up . Before the pop arrives you can here small low level scratching noise on the left channel then it pops !
My speaker relays boxes are covered with dust . They are transparent boxes, I know for sure cause I cleaned it with a cotton bud . I think dust may have got into the relay . Because speaker relay B function is weird like how I explained.
I switched my speakers to the speaker B out . Most of the time it was connected to speaker A on the amplifier . I am aware both these relays have separate relay boxes . Am I right ? However the pop sound is same on speaker B as well . But speaker B has another small issue . So I played a piece of music through speaker B as my speaker wires were connected to B . The music sound dint come until I raised the volume a little higher . So on low volume levels that is less than moderate the left speaker sometimes gives no sound and at very low volumes both speakers don't give sound . Only when I raise the volume little higher then music sound comes out of both speaker or else it just not getting the signal even though the speaker B button is ON .
Do you think my suspect is the speaker relays regarding the pop ?. But if the speaker relays have separate boxes how is it possible both boxed relays give the same pop static sound only on the left channel which occurs randomly?
I also noticed one thing . Leaving the system OFF over night about 8-9 hours then switching it ON in the morning the loud pop occurs immediately after 1 min of power up . Before the pop arrives you can here small low level scratching noise on the left channel then it pops !
My speaker relays boxes are covered with dust . They are transparent boxes, I know for sure cause I cleaned it with a cotton bud . I think dust may have got into the relay . Because speaker relay B function is weird like how I explained.
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The need to raise volume above a certain threshold before you hear it, means dirty relay contacts - a typical fault of any ageing amplifier that uses relays to switch the output. Some relays can be cleaned by gently prising off the cover and burnishing the contact faces with little strips of card but often, if the relay case is sealed, you'll need to replace it with one that matches the type (number of poles and contacts), footprint and terminal locations exactly.
You wont find the original type but you may find an equivalent among the several Japanese manufacturers still making them, probably in China. I think Element 14 and RS have a wide range that might cover the type needed but of course, you need to find to find as much detail as you can from the service manual and actual measurements of the pin spacings, overall dimensions, and the coil voltage too. Important ratings are the DC contact voltage and current. These need to be the same or better than the original part
Replacement isn't going to be easy but its the real cost of buying old, untested hifi equipment.
You wont find the original type but you may find an equivalent among the several Japanese manufacturers still making them, probably in China. I think Element 14 and RS have a wide range that might cover the type needed but of course, you need to find to find as much detail as you can from the service manual and actual measurements of the pin spacings, overall dimensions, and the coil voltage too. Important ratings are the DC contact voltage and current. These need to be the same or better than the original part
Replacement isn't going to be easy but its the real cost of buying old, untested hifi equipment.
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