Anyone know of any good specialists? Preferably in the West Midlands area as I prefer not to post, but guess I can't be choosy! Thanks.
Pioneer A400 Refurb
- Thread starter Sizzers
- Start date
ive done my fair share of mods and refurbing of the three A400's i own- can i help? plus i live in the west midlands, just near worcester.
Hi! I guess I've had this amp about 4 months or so and there's nothing intrinsically wrong with it that I'm aware of.
Externally it's unblemished: there's a little bit of crackle on the pot just past 9 o'clock but that isn't a problem, and there's quite a bit of hum on 2 of the line inputs, but apart from that it's perfect.
I was going to sell it now I've got my Marantz but I get the distinct feeling it's something I might regret later, so I thought it would be a good idea for it to get a once over to get the niggles sorted out.
Externally it's unblemished: there's a little bit of crackle on the pot just past 9 o'clock but that isn't a problem, and there's quite a bit of hum on 2 of the line inputs, but apart from that it's perfect.
I was going to sell it now I've got my Marantz but I get the distinct feeling it's something I might regret later, so I thought it would be a good idea for it to get a once over to get the niggles sorted out.
hello again, i can asure you that you will regret selling the a400 in favour of the marantz! the a400(unmodified)can, IMHO, still hold its own against any current amp under £500. I would spend a bit of time doing an a/b comparison with it and the marantz before doing anything silly.
also, if the mods dont mind forwarding you my email address (please), we can get in touch outside of this forum if you would like me to spruce up the internals of your a400.
cheers,
chris
also, if the mods dont mind forwarding you my email address (please), we can get in touch outside of this forum if you would like me to spruce up the internals of your a400.
cheers,
chris
I have no intention of selling it, it was just a thought having bought the Marantz but I knew I would regret it which is why I'm looking for a bit of a refurb.
I have a bedroom set-up and I find the Marantz better for late night, low volume listening. The idea is to get a proper rack so I can house both amps and switch between the two, using the Pioneer at more neighbour friendly times! The Pioneer is a great amp, no question, but the Marantz is still pretty damned good and works perfectly for late night listening.
I have a bedroom set-up and I find the Marantz better for late night, low volume listening. The idea is to get a proper rack so I can house both amps and switch between the two, using the Pioneer at more neighbour friendly times! The Pioneer is a great amp, no question, but the Marantz is still pretty damned good and works perfectly for late night listening.
Hi Guys,
Just caught this tread, I'm currently modifying my Pioneer A400. I had it from new in 1990, and can't bear to let it deteriorate!
Can I just ask what caps are best to replace the decoupling capacitors, what have any of you guys used that improved matters?
Also I'm not too sure which ones these are? Any pointers as to where these are and their value ratings would be much appreciated. I do have a schematic for the A400.
I've already carried out a few tweaks, I've replaced the Elna PSU Caps amongst other things and readjusted the bias up to 180ma, (I believe Tom Evans turned the Bias up to 200ma, bet that runs the amp quite hot!)
It's sounding much better now than it has of late, but I think replacing the decoupling caps won't hurt at all. (If I knew where they are located on the board and what the ratings are.)
Thanks for reading.
Just caught this tread, I'm currently modifying my Pioneer A400. I had it from new in 1990, and can't bear to let it deteriorate!
Can I just ask what caps are best to replace the decoupling capacitors, what have any of you guys used that improved matters?
Also I'm not too sure which ones these are? Any pointers as to where these are and their value ratings would be much appreciated. I do have a schematic for the A400.
I've already carried out a few tweaks, I've replaced the Elna PSU Caps amongst other things and readjusted the bias up to 180ma, (I believe Tom Evans turned the Bias up to 200ma, bet that runs the amp quite hot!)
It's sounding much better now than it has of late, but I think replacing the decoupling caps won't hurt at all. (If I knew where they are located on the board and what the ratings are.)
Thanks for reading.
Hi Tesler, sorry for the late reply ive been to egypt on holiday. regarding the decoupling capacitors i have done some research(because im just an amateur learning as i go) and found that they are marked as c201 and c202 on the schematics. if you loo at the schematics you will see those caps are the only ones in the signal path. the stock caps are 2.2uF/50v so if you are replacing them make sure to keep the capacitance the same and the voltage (rating) same or higher. if you study the schematics you will also see that there are many resistors directly in the signal path so you may want to consider upgrading them.
i hope this helps.
i hope this helps.
Hi ifitsoundsgoodlistentoit.
Hope the holiday was good? Sun not to hot?
Thanks for your reply, I looked on the Schematic and yes I have now found the caps and resistors on the circuit board, fairly simple components to change. I find the A400 a joy to work on by the way!
Can I just ask where you source all your components from?
Again, thanks for your pointer.
Cheers,
Tesler
Hope the holiday was good? Sun not to hot?
Thanks for your reply, I looked on the Schematic and yes I have now found the caps and resistors on the circuit board, fairly simple components to change. I find the A400 a joy to work on by the way!
Can I just ask where you source all your components from?
Again, thanks for your pointer.
Cheers,
Tesler
hi Tesler / all A400 owners
How did you get the schematics for the A400? I got my A400 when it was first launched. It was my first amp and brought me hours of joy in those undergrad days. Appreciate it if you could point me in the right direction where to get the schematics. I would love to try my hand at a DIY upgrade of the amp.
Appreciate all your pointers.
How did you get the schematics for the A400? I got my A400 when it was first launched. It was my first amp and brought me hours of joy in those undergrad days. Appreciate it if you could point me in the right direction where to get the schematics. I would love to try my hand at a DIY upgrade of the amp.
Appreciate all your pointers.
Dr Beat:
hi Tesler / all A400 owners
How did you get the schematics for the A400? I got my A400 when it was first launched. It was my first amp and brought me hours of joy in those undergrad days. Appreciate it if you could point me in the right direction where to get the schematics. I would love to try my hand at a DIY upgrade of the amp.
Appreciate all your pointers.
Yes, go to this website http://www.hifiengine.com/manuals/pioneer/a400.shtml
Just register, log in, and download. It's in two parts, A400x and A400.
Pages 6-9 refer to the A400
All the Best.
hi Tesler / all A400 owners
How did you get the schematics for the A400? I got my A400 when it was first launched. It was my first amp and brought me hours of joy in those undergrad days. Appreciate it if you could point me in the right direction where to get the schematics. I would love to try my hand at a DIY upgrade of the amp.
Appreciate all your pointers.
Yes, go to this website http://www.hifiengine.com/manuals/pioneer/a400.shtml
Just register, log in, and download. It's in two parts, A400x and A400.
Pages 6-9 refer to the A400
All the Best.
Tesler:Hi ifitsoundsgoodlistentoit.
Hope the holiday was good? Sun not to hot?
Thanks for your reply, I looked on the Schematic and yes I have now found the caps and resistors on the circuit board, fairly simple components to change. I find the A400 a joy to work on by the way!
Can I just ask where you source all your components from?
Again, thanks for your pointer.
Cheers,
Tesler
Hi Tesler, holiday was great thanks. Your welcome - im just glad im able to help others out. I have been the recipient of much helpful advice via this and other audio forums so its always nice to be able to return the favour.
You say that the A400 is easy to work on but it can start to get tricky when you are soldering as parts of the pcb become almost inaccessible due to the chassis layout. You should be very careful when removing components from the pcb as the soldering points are quite delicate and if you havent removed every last bit of solder then you can rip them off the board.
In fact if you are going to be doing a lot of work on the pcb then i would recommend removing it from the amp altogether. This will allow unimpeded access and you will be better able to see what you are doing. If you do this i would recommend getting some "helping hands" from maplins - i'll try and post a photo of what they are so you will understand...
I use the hificollective for all my components and have just ordered a heap of Elna Cerafines to replace the existing caps (except the PSU caps which are Mundorf Mylitic SI) in my A400GTE. I have tried Elna Cerafines in my Creek OBH21SE headphone amp and was very happy with the results.
I have also ordered some Ansar Supersound Polypropylene Caps from Crinklewood Electronics on a recommendation from another forum. These caps are supposed to be superb for use in the signal path so im going to use them as the coupling caps. They cost £3 each so it wont break the bank and it will be interesting to see how they compare to a) the stock caps and b)the elna cerafines.
if you are looking to replace the resistors in the signal path then i you can try the TAKMAN Metal Film Resistor available from hfc, these are what i used and they are quite cheap.
goodluck
Hope the holiday was good? Sun not to hot?
Thanks for your reply, I looked on the Schematic and yes I have now found the caps and resistors on the circuit board, fairly simple components to change. I find the A400 a joy to work on by the way!
Can I just ask where you source all your components from?
Again, thanks for your pointer.
Cheers,
Tesler
Hi Tesler, holiday was great thanks. Your welcome - im just glad im able to help others out. I have been the recipient of much helpful advice via this and other audio forums so its always nice to be able to return the favour.
You say that the A400 is easy to work on but it can start to get tricky when you are soldering as parts of the pcb become almost inaccessible due to the chassis layout. You should be very careful when removing components from the pcb as the soldering points are quite delicate and if you havent removed every last bit of solder then you can rip them off the board.
In fact if you are going to be doing a lot of work on the pcb then i would recommend removing it from the amp altogether. This will allow unimpeded access and you will be better able to see what you are doing. If you do this i would recommend getting some "helping hands" from maplins - i'll try and post a photo of what they are so you will understand...
I use the hificollective for all my components and have just ordered a heap of Elna Cerafines to replace the existing caps (except the PSU caps which are Mundorf Mylitic SI) in my A400GTE. I have tried Elna Cerafines in my Creek OBH21SE headphone amp and was very happy with the results.
I have also ordered some Ansar Supersound Polypropylene Caps from Crinklewood Electronics on a recommendation from another forum. These caps are supposed to be superb for use in the signal path so im going to use them as the coupling caps. They cost £3 each so it wont break the bank and it will be interesting to see how they compare to a) the stock caps and b)the elna cerafines.
if you are looking to replace the resistors in the signal path then i you can try the TAKMAN Metal Film Resistor available from hfc, these are what i used and they are quite cheap.
goodluck
Thanks for the advice!
Just to let you know, I do already have a couple of sets of helping hands, very useful indeed and I also have one of those lights that you clamp to a desk, you know, like an angle poise lamp but with a magnifying glass with fluorescent light inside.
I know what you mean about delicate soldering points. I have completely removed the PCB from the amp along with the heat sink so all components are easily accessible; the only thing left in the chassis is the transformer. I have taken this opportunity to re-solder any dry joints (usually where the headphone socket is soldered to its board and Phono socket PCB mounts) and generally given the amp a good cleanup.
I tried HF' Collective and my capacitors arrived today; the service from them is superb by the way.
I went for the Nichicon FG series; I'll let you know what the results are when I reassemble the amp and test.
Cheers.
Just to let you know, I do already have a couple of sets of helping hands, very useful indeed and I also have one of those lights that you clamp to a desk, you know, like an angle poise lamp but with a magnifying glass with fluorescent light inside.
I know what you mean about delicate soldering points. I have completely removed the PCB from the amp along with the heat sink so all components are easily accessible; the only thing left in the chassis is the transformer. I have taken this opportunity to re-solder any dry joints (usually where the headphone socket is soldered to its board and Phono socket PCB mounts) and generally given the amp a good cleanup.
I tried HF' Collective and my capacitors arrived today; the service from them is superb by the way.
I went for the Nichicon FG series; I'll let you know what the results are when I reassemble the amp and test.
Cheers.
Hi guys,
I've aquired an A400 off eBay with a view to gaining some experience in construction/modification.
I'm curious as the what effects adjusting the bias has on the amp, and how it is done?
I have studied the schematic, and with the help of this thread have found the area I need to be looking at. I've noticed the trim pots VR201 and VR202 feeding into the array of output transistors on each channel. Is this where the bias would be adjusted from? Or would it be the emittor resistors, R269 and R270?
Are there important things to consider when doing this, componants that may not be able to handle to increased current etc?
I've aquired an A400 off eBay with a view to gaining some experience in construction/modification.
I'm curious as the what effects adjusting the bias has on the amp, and how it is done?
I have studied the schematic, and with the help of this thread have found the area I need to be looking at. I've noticed the trim pots VR201 and VR202 feeding into the array of output transistors on each channel. Is this where the bias would be adjusted from? Or would it be the emittor resistors, R269 and R270?
Are there important things to consider when doing this, componants that may not be able to handle to increased current etc?
HI Westlito and welcome to the forum.
Firstly you really need to be careful when doing this as you can fry the amp or electrocute yourself. I will post the following guide which i found a different forum but i take no responsibility if anything goes wrong:
"Right you have to be DEAD careful doing this, as you could blow your output transistors.
This is one of the things Tom Evans does for the a400gte. he sets it to 200ma
the other is 2 multilayer ceramic coupling capacitors
and the final is a dc servo, ( adjusts the dc in the feedback loop)
Erno Borbely is the inventor of this circuit.
open here up.
You switch it on, play music thro it for 10 mins, get it warm.
no kids or pets when doing this, don't touch anything metal inside, and use rubber gloves if you are ham fisted.
Use a multimeter on the dc volts setting, very low reading, place the leads across the big white resistor close to the ouput stage. and measure the voltage across it.
You ideally want about 150-200 milliamps flowing through this resistor, and the japs run them quite low, maybe 20-50 milliamps.
You get the current by dividing your measured volts by the resistor value. (simple ohms law)
say the resistor is 0.33 ohms, and the volts is ( v ), then this is the dc bias current that keeps the transistors slightly on to prevent crossover distortion.
your current= Volts ( v ) / resistor value.
So work out the new volts for the new current of 150 milliamps, this is
volts= current x resistance.
=150 milliamps x value of white resistor.
You need to tweak the little variable resistor with a philips no 2 screwdrive, insulated handle, stanley very good, VERY VERY carefully indeed, increase a little literally a millimeter at a time, DONT turn it all the way or its goodbye amp. Little minute turns WHILST the voltmeter is clipped on the resistor, and you will see the voltage rise, tweak until it gets to the desired value above, and repeat for the other channel.
You amp will run hotter, more in class A, and the sound may improve. You can do this with any amp with a pot but you need to be sure the pot is for this, and not dc offset, or anything else.
In the a400 its ok.
You must be careful, as if you do it too much, current= fried, and you will set your transistors on fire if you are to heavy handed and turn it all the way.
Also, don't go above 200milliamps, as the heatsinks can't take a large class A current.
Write again if in doubt and be careful, if you are, its easy.
If you go ahead, let me know the value of the white resistor, and the measured volts across it first, to be on the safe side.
And it have to settle a little, you may need to turn the pot, leave a minute, turn a little more, or back, it hovers until it settles.
Its only a 5 minute job and dead easy."
Firstly you really need to be careful when doing this as you can fry the amp or electrocute yourself. I will post the following guide which i found a different forum but i take no responsibility if anything goes wrong:
"Right you have to be DEAD careful doing this, as you could blow your output transistors.
This is one of the things Tom Evans does for the a400gte. he sets it to 200ma
the other is 2 multilayer ceramic coupling capacitors
and the final is a dc servo, ( adjusts the dc in the feedback loop)
Erno Borbely is the inventor of this circuit.
open here up.
You switch it on, play music thro it for 10 mins, get it warm.
no kids or pets when doing this, don't touch anything metal inside, and use rubber gloves if you are ham fisted.
Use a multimeter on the dc volts setting, very low reading, place the leads across the big white resistor close to the ouput stage. and measure the voltage across it.
You ideally want about 150-200 milliamps flowing through this resistor, and the japs run them quite low, maybe 20-50 milliamps.
You get the current by dividing your measured volts by the resistor value. (simple ohms law)
say the resistor is 0.33 ohms, and the volts is ( v ), then this is the dc bias current that keeps the transistors slightly on to prevent crossover distortion.
your current= Volts ( v ) / resistor value.
So work out the new volts for the new current of 150 milliamps, this is
volts= current x resistance.
=150 milliamps x value of white resistor.
You need to tweak the little variable resistor with a philips no 2 screwdrive, insulated handle, stanley very good, VERY VERY carefully indeed, increase a little literally a millimeter at a time, DONT turn it all the way or its goodbye amp. Little minute turns WHILST the voltmeter is clipped on the resistor, and you will see the voltage rise, tweak until it gets to the desired value above, and repeat for the other channel.
You amp will run hotter, more in class A, and the sound may improve. You can do this with any amp with a pot but you need to be sure the pot is for this, and not dc offset, or anything else.
In the a400 its ok.
You must be careful, as if you do it too much, current= fried, and you will set your transistors on fire if you are to heavy handed and turn it all the way.
Also, don't go above 200milliamps, as the heatsinks can't take a large class A current.
Write again if in doubt and be careful, if you are, its easy.
If you go ahead, let me know the value of the white resistor, and the measured volts across it first, to be on the safe side.
And it have to settle a little, you may need to turn the pot, leave a minute, turn a little more, or back, it hovers until it settles.
Its only a 5 minute job and dead easy."
Hello,I found this recent post very interesting and jump in to ask if anyone here can help.
I bought a few months ago an A400, good overall conditions, but it's some weeks that I'm hearing the right channel is louder than the left one (voice not just in the middle, drums always on the right) and some very light sound cracks occasionally occurs.
Can someone well experienced try to argue what's happening to my beloved amp?
I suppose I have to engage some good techn here in italy but I would have some clues before.
Can it be the case to upgrade some other components too?
thanks a lot
Angelo
I bought a few months ago an A400, good overall conditions, but it's some weeks that I'm hearing the right channel is louder than the left one (voice not just in the middle, drums always on the right) and some very light sound cracks occasionally occurs.
Can someone well experienced try to argue what's happening to my beloved amp?
I suppose I have to engage some good techn here in italy but I would have some clues before.
Can it be the case to upgrade some other components too?
thanks a lot
Angelo
cstanwhf
Well-known member
gUtto:
Hello,I found this recent post very interesting and jump in to ask if anyone here can help.
I bought a few months ago an A400, good overall conditions, but it's some weeks that I'm hearing the right channel is louder than the left one (voice not just in the middle, drums always on the right) and some very light sound cracks occasionally occurs.
Can someone well experienced try to argue what's happening to my beloved amp?
I suppose I have to engage some good techn here in italy but I would have some clues before.
Can it be the case to upgrade some other components too?
thanks a lot
Angelo
Check the volume control knob. On the knob, there is actually two controls which allow you to adjust the volume for left and right channel individually.
You can try to make sure they are set to the same level. Turn both control anti clockwise to minimise both left and right channel.
Then just turn the knob at the edge clockwise, which will increase both left and right volume at the same time.
If still not balance, adjust both knob until the volume is balance. Then use the edge to adjust the volume from then on.
Hello,I found this recent post very interesting and jump in to ask if anyone here can help.
I bought a few months ago an A400, good overall conditions, but it's some weeks that I'm hearing the right channel is louder than the left one (voice not just in the middle, drums always on the right) and some very light sound cracks occasionally occurs.
Can someone well experienced try to argue what's happening to my beloved amp?
I suppose I have to engage some good techn here in italy but I would have some clues before.
Can it be the case to upgrade some other components too?
thanks a lot
Angelo
Check the volume control knob. On the knob, there is actually two controls which allow you to adjust the volume for left and right channel individually.
You can try to make sure they are set to the same level. Turn both control anti clockwise to minimise both left and right channel.
Then just turn the knob at the edge clockwise, which will increase both left and right volume at the same time.
If still not balance, adjust both knob until the volume is balance. Then use the edge to adjust the volume from then on.
Thanks cstanwhf,
I already act like that to have the sound balanced
I'm afraid it's now something to do with the power amplifier components, and I I'll have to repair it soon, as one of the channels will fails...
I'm hoping it's only a knob fail !
I already act like that to have the sound balanced
I'm afraid it's now something to do with the power amplifier components, and I I'll have to repair it soon, as one of the channels will fails...
I'm hoping it's only a knob fail !
cstanwhf
Well-known member
There was a post previously where you can download a copy of the A-400 service manaul.
If you are brave can have a go.
Otherwise, better to refer to a qualified technician.
Do not have the link now. Will post it after work tonight.
If you are brave can have a go.
Otherwise, better to refer to a qualified technician.
Do not have the link now. Will post it after work tonight.
cstanwhf
Well-known member
Hi ifitsoundsgoodlistentoit
I have an A 400 and had cover off to DeOxit the volume control. I noticed the 2 big black ? capacitors at the back had a white foam / glue at the bottom. I wondered if this was a fault and if they were leaking some insulation. BUT amp works fine?
I got on web to search and joined this site today because I saw your photo of an open A400 with what appears to be the same stuff around the capacitors in your top photo.
Can you tell me if they are leaking or are some sort of assembly glue?
Absolute beginner, Brett. Thanks.
I have an A 400 and had cover off to DeOxit the volume control. I noticed the 2 big black ? capacitors at the back had a white foam / glue at the bottom. I wondered if this was a fault and if they were leaking some insulation. BUT amp works fine?
I got on web to search and joined this site today because I saw your photo of an open A400 with what appears to be the same stuff around the capacitors in your top photo.
Can you tell me if they are leaking or are some sort of assembly glue?
Absolute beginner, Brett. Thanks.
1Analouge:
Hi ifitsoundsgoodlistentoit
I have an A 400 and had cover off to DeOxit the volume control. I noticed the 2 big black ? capacitors at the back had a white foam / glue at the bottom. I wondered if this was a fault and if they were leaking some insulation. BUT amp works fine?
I got on web to search and joined this site today because I saw your photo of an open A400 with what appears to be the same stuff around the capacitors in your top photo.
Can you tell me if they are leaking or are some sort of assembly glue?
Absolute beginner, Brett. Thanks.
Hi 1A,
it's the same with mine; it surprised me a lot when I first opened my A400 but it seems very common.
About my unbalanced volume, I found that a simple very light rotation of the back knob of the volume control solves the problem: I mean no other music quality issues reported, it seems like the knob rotation solves it all.
Thanks for the link to the service manual
Bye
A
Hi ifitsoundsgoodlistentoit
I have an A 400 and had cover off to DeOxit the volume control. I noticed the 2 big black ? capacitors at the back had a white foam / glue at the bottom. I wondered if this was a fault and if they were leaking some insulation. BUT amp works fine?
I got on web to search and joined this site today because I saw your photo of an open A400 with what appears to be the same stuff around the capacitors in your top photo.
Can you tell me if they are leaking or are some sort of assembly glue?
Absolute beginner, Brett. Thanks.
Hi 1A,
it's the same with mine; it surprised me a lot when I first opened my A400 but it seems very common.
About my unbalanced volume, I found that a simple very light rotation of the back knob of the volume control solves the problem: I mean no other music quality issues reported, it seems like the knob rotation solves it all.
Thanks for the link to the service manual
Bye
A
Hi,
I have just bought a Pioneer A400, and noticed that you are in the West Midlands.
I would be interested in geting it serviced/modded - what sort of services do you offer, and what's the damage to the old wallet?
Cheers,
John.
I have just bought a Pioneer A400, and noticed that you are in the West Midlands.
I would be interested in geting it serviced/modded - what sort of services do you offer, and what's the damage to the old wallet?
Cheers,
John.
Correct Service in Derby were well recommended to me.
As of October last year they charged £30 for a full diagnostic and report, and if there was any work that needed doing that was then deducted from any further costs. A friend of mine was going to drop it in for me at the beginning of the year as he had some work up there, but the snow put paid to that!
As of October last year they charged £30 for a full diagnostic and report, and if there was any work that needed doing that was then deducted from any further costs. A friend of mine was going to drop it in for me at the beginning of the year as he had some work up there, but the snow put paid to that!
01159 563434
Facebook
Twitter
Instagram