What do you consider a small electrolytic?
This amp and several others of mine have dates codes that put it in the late 70's
From other sites I've read that ALL the electrolytics caps of any size (mfd) and voltage should be replaced with out any hesitation. A former service tech states to buy only 105 degree C caps for added life span.
I have about 20 components ranging from early 70' to late 1990's, Needless to say I'm not looking forward to replacing hundreds of caps but who am I to argue...
This amp and several others of mine have dates codes that put it in the late 70's
From other sites I've read that ALL the electrolytics caps of any size (mfd) and voltage should be replaced with out any hesitation. A former service tech states to buy only 105 degree C caps for added life span.
I have about 20 components ranging from early 70' to late 1990's, Needless to say I'm not looking forward to replacing hundreds of caps but who am I to argue...
when using 105C caps, measure their ESR first.... i've noticed that 105 degree caps generally have a higher ESR than 85 degree caps.
the NTE replacement for the 4558 is probably ok, but the replacement for the TL072, you don't know what you're getting (TL082, LF353) for noise performance.
as for the very large caps, it's difficult to do a good ESR test on them. one way to do it would be to feed a 10V 200hz sine wave (hint, use an amplifier for this) through a 10 ohm resistor into one of these caps and read the residual across the cap with an oscope. for a 15000uf cap. the voltage residual without ESR would be 54mV. for electrolytics though, you may want to couple the output of the amp through a much larger cap (150,000uf) so that you can DC bias the cap under test and keep it from going into conduction on negative half cycles. the DC bias supply (12V would be plenty) can be coupled through a high resistance (100ohm to 1k) to isolate the DC supply from interfering with the measurement. if these show ESR much more than a half ohm replace them (0.5 ohm would show up as 0.5 V of signal across the terminals of the cap, since 10V through 10 ohm would be sourcing 1A).
the NTE replacement for the 4558 is probably ok, but the replacement for the TL072, you don't know what you're getting (TL082, LF353) for noise performance.
as for the very large caps, it's difficult to do a good ESR test on them. one way to do it would be to feed a 10V 200hz sine wave (hint, use an amplifier for this) through a 10 ohm resistor into one of these caps and read the residual across the cap with an oscope. for a 15000uf cap. the voltage residual without ESR would be 54mV. for electrolytics though, you may want to couple the output of the amp through a much larger cap (150,000uf) so that you can DC bias the cap under test and keep it from going into conduction on negative half cycles. the DC bias supply (12V would be plenty) can be coupled through a high resistance (100ohm to 1k) to isolate the DC supply from interfering with the measurement. if these show ESR much more than a half ohm replace them (0.5 ohm would show up as 0.5 V of signal across the terminals of the cap, since 10V through 10 ohm would be sourcing 1A).
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Guys
Great info here ! I have wanted an APT amp since I saw them new.
Well the good news is I have one coming, looks good in the photos, the current owner describes it as having a fuzzy channel. Im guessing a re cap and tune up will fix the issues.
Well I hope so, but I wont know till it arrives....
bob
Great info here ! I have wanted an APT amp since I saw them new.
Well the good news is I have one coming, looks good in the photos, the current owner describes it as having a fuzzy channel. Im guessing a re cap and tune up will fix the issues.
Well I hope so, but I wont know till it arrives....
bob
Thanks guys.
Im going to give it a going over, replacing all the small caps, touching up the solder connections, clean or replace the relay. re grease the output transistors. I figure Ill go over it carefully. 2, 80k caps..yeah big money there. I have an ESR checker, hoping they test out.
Anyone out there have a copy of the service manual?? Checking all my usual sources cant find a pdf, let alone a paper manual.
bob
Im going to give it a going over, replacing all the small caps, touching up the solder connections, clean or replace the relay. re grease the output transistors. I figure Ill go over it carefully. 2, 80k caps..yeah big money there. I have an ESR checker, hoping they test out.
Anyone out there have a copy of the service manual?? Checking all my usual sources cant find a pdf, let alone a paper manual.
bob
Guys
I received my APT amp today ! Serial 1900, revision 7 as far as I see.
What im finding so far, for some reason the mono/stereo bridge switch is missing.
It appears that the board has been jumpered, so first thing is to replace the missing switch.
Firing the amp up, no fireworks both protection lights come on, one fades out in a few seconds the other takes a good 10-15 seconds to fade out.
I hear the relay click about 5 seconds after firing it up.
Connected up a pair of speakers, input into the amp, I get one channel seems ok, noticing the indicator for this side glowing green. Sound is clean and strong.
The second channel very distorted output, the indicator for this channel does go green with a very low signal, but quickly goes red with anything but a very low level signal. As if the channel is going into overload. again the sound is very distorted sounds to me like an output is gone.
I need to track down a service manual to properly trouble shoot this guy, but I thought I would ask, any ideas.
bob
I received my APT amp today ! Serial 1900, revision 7 as far as I see.
What im finding so far, for some reason the mono/stereo bridge switch is missing.
It appears that the board has been jumpered, so first thing is to replace the missing switch.
Firing the amp up, no fireworks both protection lights come on, one fades out in a few seconds the other takes a good 10-15 seconds to fade out.
I hear the relay click about 5 seconds after firing it up.
Connected up a pair of speakers, input into the amp, I get one channel seems ok, noticing the indicator for this side glowing green. Sound is clean and strong.
The second channel very distorted output, the indicator for this channel does go green with a very low signal, but quickly goes red with anything but a very low level signal. As if the channel is going into overload. again the sound is very distorted sounds to me like an output is gone.
I need to track down a service manual to properly trouble shoot this guy, but I thought I would ask, any ideas.
bob
Uncle Jed is the expert on this amp.
I can only guess what may be wrong, but I'd start with a signal generator and a scope and start from the input and trace the signal path to the output. or maybe the other way around. It's probably a failed transistor. My guess is the output stage. As long as you have it apart, replace all the caps except for the 2 80K mfd psu caps, they are quality parts and should last another decade.
BTW: what did you pay for the amp? ideas what they are selling for these days? fyi: I paid about $200 ea for my stack.
I can only guess what may be wrong, but I'd start with a signal generator and a scope and start from the input and trace the signal path to the output. or maybe the other way around. It's probably a failed transistor. My guess is the output stage. As long as you have it apart, replace all the caps except for the 2 80K mfd psu caps, they are quality parts and should last another decade.
BTW: what did you pay for the amp? ideas what they are selling for these days? fyi: I paid about $200 ea for my stack.
Guys, Im not sure what happened. I undid the protection board to have a look, I saw added caps on the board, so was making a list of parts that I thought I was going to need.
Well lo and behold I re attached the board and thought Id do a check on the offset.
Well firing it up it seemed to behave normally.
So I tried her again and it seems to be working fine. both channels are clean strong and clear. Dang she has some juice..... Im going on and replacing the missing bridge switch. and doing a recap to start out with on the protection board.
Sitting here now, listening to music through the APT she is driving a set of Pioneer monitors 6 ohm load, with ease.
Damn..... I guess it was an earth connection on the protection board. I suppose reflow all the connections on the board also.
bob
Well lo and behold I re attached the board and thought Id do a check on the offset.
Well firing it up it seemed to behave normally.
So I tried her again and it seems to be working fine. both channels are clean strong and clear. Dang she has some juice..... Im going on and replacing the missing bridge switch. and doing a recap to start out with on the protection board.
Sitting here now, listening to music through the APT she is driving a set of Pioneer monitors 6 ohm load, with ease.
Damn..... I guess it was an earth connection on the protection board. I suppose reflow all the connections on the board also.
bob
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Hi folks--
I'm new here, just finding the forum tonight while Googling the Apt Power 1.
I wasn't sure if I should start a new thread for my simple question, but then saw Bob's comment about a fuzzy channel and request for a service manual. While I don't have a service manual, I should probably have the original owner's manual that came with the Amp somewhere if that will help, I just have to find where it is! As I recall, there was a fold-out schematic (although, that could have just been the pre).
Now to the question part of my reply: We had a power outage tonight, with a couple rapid surges at the beginning of the outage. When the power came back on, I've now got a fuzzy left channel. The red overload signal for the left channel is on, while the right channel remains green.
I should tell you that while I appreciate good electronics, I know diddly about it! So, does anyone know of someone who repairs these? It might also be a good time to also replace the caps at the same time, I guess.
I've had my amp and pre-amp since 1980.
Thanks, guys.
Ron Hildebrand
Uncle Jed is the expert on this amp.
I can only guess what may be wrong, but I'd start with a signal generator and a scope and start from the input and trace the signal path to the output. or maybe the other way around. It's probably a failed transistor. My guess is the output stage. As long as you have it apart, replace all the caps except for the 2 80K mfd psu caps, they are quality parts and should last another decade.
BTW: what did you pay for the amp? ideas what they are selling for these days? fyi: I paid about $200 ea for my stack.
Ron
Uncle Jed is the expert here, Hopefully we can get our amps up and running.
bob
Guys
I dont want to be a bum, anyone out there have a list of the transistor types in the APT, I have a schematic but it dosen't list the types.
I figure if im going to rebuild this beast I better get silicon ready.
The outputs no problem.
Oh yeah I have another APT 1 on the way soon, similar symptoms.
bob
I dont want to be a bum, anyone out there have a list of the transistor types in the APT, I have a schematic but it dosen't list the types.
I figure if im going to rebuild this beast I better get silicon ready.
The outputs no problem.
Oh yeah I have another APT 1 on the way soon, similar symptoms.
bob