Nelson Pass said:
I got it.. it just took some tweeking.. I do need to cycle it ONE MORE TIME.. and I am guessing I will need that 4amp fuse.. but only to go from cold start.. with a variac. I guess I will go it with no fuse once I run it for a bit. I was just being really conservative in my adjustments.. I ended up right around 75mv while its at temp..
Man 45c is DAMN hot.. the room its in is warm now which is nice since its damn cold in colorado right now!
Yeah it is a great feeling knowing I can fix either of my two amps now.. but unfortunately I have the bug.. I want to build you Aleph 3.... I read the sterophile review on it and its too tempting...
Would this be a poor choice for a 1st project?
Also; for those following this thread.. a little bias tip.. if you are using your hands AND a temp gauge remember, when you do the 5 second test with your hand the actual temp of the heat sink will drop a few degrees! It left me scratching my head a few times until I figured out what was going on!
The Aleph 3 will be child's play after this. Amongst other things, the bias is built into the circuit; you don't have to adjust a thing.
Grey
Grey
GRollins said:
Cool I am going to start researching...
I'm playing the 400a now.. it sounds pretty damn good even thru my old JBL's..
I still havent gotten the nerve to connect to my vandersteens but I will after a few more hours..
So to wrap this thread up... I'd like to thank all you guys for your patience and for offering your wisdom and experience up for absolutely free (although I think I offered some entertainment value in exchange 😉 )
I hope this thread helps someone else troubleshooting a class A solid state amp as I suspect much of what has been discussed here will play over into many other amplifiers..
this has been an experience I will never forget and I will use these skills even as basic as they are in many ways.. even just reading a specification listing of an audio product will now be a new experience for me..
So Steve, Grey, Chris and all the others who have helped out.. oh yeah and that Pass dude.. he was sorta helpful too.. 🙂 I am pretty sure I'll be running into most of you soon... as I am really motivated to build an amp now..
so I wont say goodbye.. just thanks!
Joe
Joe,
There are circuit boards available for the Alephs. That will simplify your life considerably.
Grey
There are circuit boards available for the Alephs. That will simplify your life considerably.
Grey
I know that Nelson for one was hoping that this thread would be useful to others in the future.
I'm sure the other contributors do too. Apogee certainly deserves credit for "adopting" you in the beginning.
I know I've learned a lot about how to approach a repair like this, from everyones input. I can see that you will be a good member here, and I am certainly pleased with your newfound addiction!!!😀
Hi Joe,
I'm deeply pleased that things worked out well. Now you have something to be very proud of. The value of your amplifier has been greatly enhanced in your eyes (and mine). A little sweat and experience.
Build your next project and start a thread on it.
-Chris 😉
I'm deeply pleased that things worked out well. Now you have something to be very proud of. The value of your amplifier has been greatly enhanced in your eyes (and mine). A little sweat and experience.
Build your next project and start a thread on it.
-Chris 😉
Thanks guys... playing it thru my vandersteens now... boy is it different than my newer model. I have not formed an opinion yet. I did notice it has very little gain to it.. I am guessing this was a customer driven change in my newer 400a. I don't mind turning my preamp up all the way.. hehehe although; it wont play nearly as loud as the newer version.. but I dont need the volume. MIght be fun to "fix" this by comparing to my newer version and maybe upgrading it a bit... nah; I think I will leave it be what it is (was).. The bias seems dead on.. 5 seconds and I would rather not hold on so much anymore.. and nice and even channel to channel.. I did good 🙂
I think my next amp will need to be newer technology just so I know what has been accomplished..
I can't decide.. the pass amps are all so interesting!
Hey Steve! Where are you? Its done!!! 🙂
I think my next amp will need to be newer technology just so I know what has been accomplished..
I can't decide.. the pass amps are all so interesting!
Hey Steve! Where are you? Its done!!! 🙂
Not as much gain as your other one?
Have to turn your preamp up all the way?
Hmmm...I don't like this. Methinks there's still a bug in the works, somewhere.
Do both channels play at the same volume?
Grey
Have to turn your preamp up all the way?
Hmmm...I don't like this. Methinks there's still a bug in the works, somewhere.
Do both channels play at the same volume?
Grey
Congrats!!!
Hi Joe,
Just now had a chance to catch up. GREAT JOB SO FAR!
Sorry, I've been so scarce!
Unfortunately, I agree with Grey that something isn't right if you're being forced to run your preamp wide open...
Perhaps something was damaged in the front end that caused the amp to oscillate, fry the zobel network and blow the outputs.
The sensitivity should be the same as your other amp. This would also explain the sound difference between the amps. They should sound very, very similar. Again, you shouldn't need to run anything wide open.
Sorry to send bad news, but you're getting close... Stick with it...
I wouldn't go hooking it up to the Vandersteens just yet...
Did you check the small signal transistors on the boards?
Pay particular attention to where the input lead (from the rca jack) enters the board. Follow the hot lead where it's soldered in and then follow the trace to the base of one of the transistors. I'd be very interested to know if this one is good. Also check the resistors and any diodes around it.
Hi Joe,
Just now had a chance to catch up. GREAT JOB SO FAR!
Sorry, I've been so scarce!
Unfortunately, I agree with Grey that something isn't right if you're being forced to run your preamp wide open...
Perhaps something was damaged in the front end that caused the amp to oscillate, fry the zobel network and blow the outputs.
The sensitivity should be the same as your other amp. This would also explain the sound difference between the amps. They should sound very, very similar. Again, you shouldn't need to run anything wide open.
Sorry to send bad news, but you're getting close... Stick with it...
I wouldn't go hooking it up to the Vandersteens just yet...
Did you check the small signal transistors on the boards?
Pay particular attention to where the input lead (from the rca jack) enters the board. Follow the hot lead where it's soldered in and then follow the trace to the base of one of the transistors. I'd be very interested to know if this one is good. Also check the resistors and any diodes around it.
Well; I played it for about 5 hours last night.. and the Vandersteens seemed to have survived.
I have a cold, but what I noticed is:
1. Less of a full sound
2. Possibly more of a airy sound (which I am dieing for)
3. Way, less potential volume, like 60%
4. Less bass, significantly less bass (incorrect 9800mfd filter caps?)... I can't decide if I like that aspect as I can hear more detail in the mids..
5. Way more mids.. had to turn down the mid networks on the vandys.
6. The power meters are WAY more active and act similar to the volume knob position on the preamp. Almost linear depending of course on the material I am playing from the CD player. Come to think of it, I think I might be dissapointed in the volume when I start to play my vinyl.
Remember, Mr. Pass said there were changes made to the input boards on later models.
You guys didnt mention the subsitution of power Mosfets so I am guessing they have little or no impact here.
I remember looking at the small transistors and noting they seemed right IN CIRCUIT.. but I cant say I tested in detail.
Oh and the channels are damn close in balance.
When I first started listening I was dissapointed.. I didnt hear a full sound.. but as the night went on (no alcohol involved) I started to hear more detail and more airy sound.. which I was thrilled about.. and I was wondering if it was the bias or the electrolytics that might transform my newer 400a..
So even if its broke, I am not sure I want to fix it yet. 🙂 But my curiosity is going to get the best of me.. so I will start troubleshooting...
I'll do what you suggest Steve and report back.. but any more feedback would be helpful based on this post.
j
P.S. BOTH CHANNELS ARE BROKE?? hmmmmmmm??????
P.S.S. I only "have" to run it open if I really want to rock.. like party mode.. which is pretty rare.. although occasional when the girlfriend is gone and usually involves only myself and Mr. Ozzy Osbourne. So dont get the wrong impression.. but 1/2 to 3/4 would be enough on the newer amp.
another ps. I'm ordering the filter caps today.. I was waiting to make sure the investment was worth it.. remember... they are "wrong" 9800 and should be 15000 based on what I hear.. and I am going higher based on the creators advice..
I have a cold, but what I noticed is:
1. Less of a full sound
2. Possibly more of a airy sound (which I am dieing for)
3. Way, less potential volume, like 60%
4. Less bass, significantly less bass (incorrect 9800mfd filter caps?)... I can't decide if I like that aspect as I can hear more detail in the mids..
5. Way more mids.. had to turn down the mid networks on the vandys.
6. The power meters are WAY more active and act similar to the volume knob position on the preamp. Almost linear depending of course on the material I am playing from the CD player. Come to think of it, I think I might be dissapointed in the volume when I start to play my vinyl.
Remember, Mr. Pass said there were changes made to the input boards on later models.
You guys didnt mention the subsitution of power Mosfets so I am guessing they have little or no impact here.
I remember looking at the small transistors and noting they seemed right IN CIRCUIT.. but I cant say I tested in detail.
Oh and the channels are damn close in balance.
When I first started listening I was dissapointed.. I didnt hear a full sound.. but as the night went on (no alcohol involved) I started to hear more detail and more airy sound.. which I was thrilled about.. and I was wondering if it was the bias or the electrolytics that might transform my newer 400a..
So even if its broke, I am not sure I want to fix it yet. 🙂 But my curiosity is going to get the best of me.. so I will start troubleshooting...
I'll do what you suggest Steve and report back.. but any more feedback would be helpful based on this post.
j
P.S. BOTH CHANNELS ARE BROKE?? hmmmmmmm??????
P.S.S. I only "have" to run it open if I really want to rock.. like party mode.. which is pretty rare.. although occasional when the girlfriend is gone and usually involves only myself and Mr. Ozzy Osbourne. So dont get the wrong impression.. but 1/2 to 3/4 would be enough on the newer amp.
another ps. I'm ordering the filter caps today.. I was waiting to make sure the investment was worth it.. remember... they are "wrong" 9800 and should be 15000 based on what I hear.. and I am going higher based on the creators advice..
Hi Joe,
The size of your filter caps will not have an effect on the amount of bass you are hearing (within reason). Your 9,800 uF caps are not the cause.
Have a look at the caps on the signal board. Transistors must be measured out of circuit.
-Chris
The size of your filter caps will not have an effect on the amount of bass you are hearing (within reason). Your 9,800 uF caps are not the cause.
Have a look at the caps on the signal board. Transistors must be measured out of circuit.
-Chris
anatech said:
There are 2 caps that I did not replace that are very small but might be lytics.. so I will take a close up pic tonight and send.. all the others I think are mica's.
hmmm.. could I have installed a cap backwards? I THINK they were all bi-polar.. hmmmm..
Edit: so I know this is hard to see.. but the red indicated the two I did not replace that I maybe should have.. the violet indicates caps I replaced and only the large one was replaced with a polar cap (and I know I got it right).. the yellow indicates caps I thought were mica and did not replace..
All the large resistors were replaced after this photo.. hmm maybe I got those wrong? I better go check.
Guys, remember this is both channels.. its highly unlikely that something broke the same on both sides right?
Attachments
Well guys, I am really sorry.. today I went home for lunch and decided to listen again.. this time it sounded very much like my other 400a.. and the volume control seemed to operate about the same...
So, while I do have a cold I dont think that was it.. what I am suspicious of is my preamp.. currently its an old HK solid state unit.. and I had turned it off several days, well, weeks ago to pull my newer 400a out and inspect it. Well I turned it on JUST before listening to the repaired 400a thru the vandersteens... and I am thinking maybe I did not realize that this preamp needs a good amount of time to warm up?? (I normally leave it on 24/7)..
So let me play some more and see what I find..
I do have another question though: Is it common to see fuses at the speaker outputs like this amp has? It seems weird to go from a fast blow 5amp hair width fuse to bi-wire 12 guage cables. Is this something Threshold's attorney's added to the schematic or is this a legitimate component to be in this position?
J
P.S. WOW.. Mouser ships FAST!
So, while I do have a cold I dont think that was it.. what I am suspicious of is my preamp.. currently its an old HK solid state unit.. and I had turned it off several days, well, weeks ago to pull my newer 400a out and inspect it. Well I turned it on JUST before listening to the repaired 400a thru the vandersteens... and I am thinking maybe I did not realize that this preamp needs a good amount of time to warm up?? (I normally leave it on 24/7)..
So let me play some more and see what I find..
I do have another question though: Is it common to see fuses at the speaker outputs like this amp has? It seems weird to go from a fast blow 5amp hair width fuse to bi-wire 12 guage cables. Is this something Threshold's attorney's added to the schematic or is this a legitimate component to be in this position?
J
P.S. WOW.. Mouser ships FAST!
Hi Joe,
No comment. 😉
I would replace those caps. Possibly bypass them with a film type as well.
-Chris
No comment. 😉
I would replace those caps. Possibly bypass them with a film type as well.
-Chris
anatech said:
Understood 😉
"Those caps" ; the ones I am suspecting might be lytics or all of them?
Hi Joe,
If you have not replaced the electrolytics on the board yet, do so. Replace any electrolytics with film caps where possible, ceramics with Mica or something equivalent.
Yes, them are those I was talking about.
-Chris 😀
If you have not replaced the electrolytics on the board yet, do so. Replace any electrolytics with film caps where possible, ceramics with Mica or something equivalent.
Yes, them are those I was talking about.
-Chris 😀