Apogee said:
I remember checking them soldered in and they seemed ok.. diodes.. yes I thought I did.
It guess I thought we were just shooting for replacing the electrolytics, the emitter resistors and the power tranis...
should I pull the board now and check all this by removing them or should I try a input and speaker?
okay, one step at a time.
First, ground the input and put your voltmeter on the output terminals.
Slowly, bring up the power while watching for dc at the output.
We want to make sure it can sit there at 120v and is stable before you hook anything up to it.
Don't worry about the bias right now.
Let's just see if it will idle...
First, ground the input and put your voltmeter on the output terminals.
Slowly, bring up the power while watching for dc at the output.
We want to make sure it can sit there at 120v and is stable before you hook anything up to it.
Don't worry about the bias right now.
Let's just see if it will idle...
I;m sorry I couldnt help myself.. I hooked it up...
ITS ALIVE!!!!!!!!!!!!!!!!!!!
The beatles white is cranking right now!!!!!!!!!!
Whoo hooo!!!!!!!!!!!!!!
I am just playing it thru a crappy old speaker.. but it seems to be playing fine..... 5 minutes maybe so far... I better go back and feel the heat sink...
You guys are the BEST!!!!!!!!!!!!
ITS ALIVE!!!!!!!!!!!!!!!!!!!
The beatles white is cranking right now!!!!!!!!!!
Whoo hooo!!!!!!!!!!!!!!
I am just playing it thru a crappy old speaker.. but it seems to be playing fine..... 5 minutes maybe so far... I better go back and feel the heat sink...
You guys are the BEST!!!!!!!!!!!!
Congrats!
I'm a bit more conservative than you...
I'm just glad the magic smoke stayed in...
You did mention that you liked smoke tests... LOL!
Glad it's working...
Again, congrats and good job!
I'm a bit more conservative than you...
I'm just glad the magic smoke stayed in...
You did mention that you liked smoke tests... LOL!
Glad it's working...
Again, congrats and good job!
Apogee said:Congrats!
I'm a bit more conservative than you...
I'm just glad the magic smoke stayed in...
You did mention that you liked smoke tests... LOL!
Glad it's working...
Again, congrats and good job!
I had to know! Well; its now playing very quietly thru an old JBL studio monitor.. and it sounds wonderful.. no distortion.. no noise that I can hear of yet.. I have an old tube preamp on it so I just hear the hum from that..
So I wonder should I just adjust the bias as it warms up then? and also; can I go ahead and connect the other side up and see how it compares?
I think I will just pause for now.. LOTS accomplished! The fuse was blown on the speaker output anyway.. so I had to use the other side fuse.. (dont have any).. BTW.. do I need an audio grade fuse??
Okay.. thanks again guys!!! Even if its not quite right at this point this is a major achievment to have a complete beginner nail it on the first try.. although.. that aligator clip thing is weird..
Joe
EDIT: Still playing.. been like 20 minutes I think.. heat sink is about as warm as my other 400a is by now.. just warm.. maybe 120 degrees? Just a guess.. seems even too.. (my other 400a heats up more on the rear (pnp's?).. at first and then evens out..
Sounds as good as this old JBL stuidio monitor has sounded thru my other 400a (sorta dead.. LOL)..
Got the tripod out for this one...
Here she is warming up for the 1st time in who knows how long?!!
If you look close you can see the left channel lit up 😉
Here she is warming up for the 1st time in who knows how long?!!
An externally hosted image should be here but it was not working when we last tested it.
If you look close you can see the left channel lit up 😉
Bias adjustment
You mentioned in a previous post that you have a technical document addressing biasing.
Why not either retype it or scan it in its entirety and post it here so everyone has it for reference?
Then we can work on dialing yours in...
You mentioned in a previous post that you have a technical document addressing biasing.
Why not either retype it or scan it in its entirety and post it here so everyone has it for reference?
Then we can work on dialing yours in...
Re: Bias adjustment
Okay; I figured out where I found them.. see the PDF files the gentleman posted here.. http://www.diyaudio.com/forums/showthread.php?s=&threadid=55055&perpage=10&highlight=&pagenumber=2
I dont know what the source is though.. so not sure if its accurate..
I remember Jon saying to just hook onto an emitter and note voltage.. adjust slowly until you get the thing cooking to the point where you can hold onto for 5-10 seconds and then you want to let go I guess.. see to me; uncomfortable is REALLY relative.. Mr. pass seems to mention this over and over and over in the forums though..
BTW.. Playing for an hour now.. SOUNDS GREAT!!!!
Apogee said:
Okay; I figured out where I found them.. see the PDF files the gentleman posted here.. http://www.diyaudio.com/forums/showthread.php?s=&threadid=55055&perpage=10&highlight=&pagenumber=2
I dont know what the source is though.. so not sure if its accurate..
I remember Jon saying to just hook onto an emitter and note voltage.. adjust slowly until you get the thing cooking to the point where you can hold onto for 5-10 seconds and then you want to let go I guess.. see to me; uncomfortable is REALLY relative.. Mr. pass seems to mention this over and over and over in the forums though..
BTW.. Playing for an hour now.. SOUNDS GREAT!!!!
Glad it's still playing...
Keep in mind that you won't feel the bias heat changes instantly. The heatsinks will slowly build temp. That's why the service info talks about checking at one hour intervals.
You check it at the emitter resistors. Just clip on each side of one of the resistors and measure the voltage drop.
In a previous post, Jon mentioned to adjust to "Bias at 150 mv. Increase to 200mv as desired."
I also remember Nelson mentioning 160mv.
The factory spec on the link you posted shows 90mv. (if memory serves, you have .68 emitter resistors) That could by why they are barely running warm. Threshold might have cooled the amps down to increase component life.
So, now you have your starting point.
You'll want to meter set to the DC mv setting....
Please be careful! You have to do this with the unit idling, no input or output hooked up.
MAKE SURE YOU DON'T ACCIDENTALLY GROUND YOUR TEST LEADS!!!
GO SLOWLY Small steps win the race here...
Keep us posted.
Keep in mind that you won't feel the bias heat changes instantly. The heatsinks will slowly build temp. That's why the service info talks about checking at one hour intervals.
You check it at the emitter resistors. Just clip on each side of one of the resistors and measure the voltage drop.
In a previous post, Jon mentioned to adjust to "Bias at 150 mv. Increase to 200mv as desired."
I also remember Nelson mentioning 160mv.
The factory spec on the link you posted shows 90mv. (if memory serves, you have .68 emitter resistors) That could by why they are barely running warm. Threshold might have cooled the amps down to increase component life.
So, now you have your starting point.
You'll want to meter set to the DC mv setting....
Please be careful! You have to do this with the unit idling, no input or output hooked up.
MAKE SURE YOU DON'T ACCIDENTALLY GROUND YOUR TEST LEADS!!!
GO SLOWLY Small steps win the race here...
Keep us posted.
Apogee said:
Wait.. so; I must ground the meter anywhere and then measure voltage before and after any emitter resistor and then subtract the high from the low? Or do I actually clip in on each side of the resistor?
Yep.. and its sounding a little better I think as it warms up.. If it is at temp now I would think it should be hotter.. I can grab it and hang on with no wanting to let go.. see, this is so relative!!!
I will wait for your response though.. not gonna smoke this thing at this point!!!!
Have Neil Young unplugged playing right now 😉
EDIT: My emitters are .22.. red red silver is what was installed! Is this wrong you think?? I just checked my photo: yep what I removed was red red silver. ..22.
EDIT: My covers are not on either.. I better leave it right here for now.. it might be just right when the cover is on!
EDIT: I just realized something.. if a person follows this thread; ANYONE can rebuild a 400a.. I mean even if the input board is bad; all you have to do is replace the drivers in addition to what we talked about here.. and I am guessing this is rare; and it would be a real noisy amp is what the symptom would be?
EDIT: This is not to discount the pro's out there... I mean this took a fair amount of time.. and I am only half done.. AND I am not saying this thing is tuned perfectly either.. Its just simply playing at this point.
Just pick an emitter resistor and clip on each end of it. Make sure you have your meter set properly before you clip on, and again, make sure you don't short anything.
You will get a voltage reading in mv.
Let us know what the reading is...
Again, no input and no speaker hooked up.
Yes, you will have to kill Neil Young...
You will get a voltage reading in mv.
Let us know what the reading is...
Again, no input and no speaker hooked up.
Yes, you will have to kill Neil Young...
Hi Steve,
Hey Joe,
You got your amp working. That's great!
-Chris
Oh please do! Even his lyrics are terrible.
Hey Joe,
You got your amp working. That's great!
-Chris
Hi Steve,
I can not for the life of me figure out how such an infantile, vocally challenged, over expressive wanna-be musician was able to get into a recording studio!
He comes on the radio and the station gets changed. My wife and I both race for the channel selector. Simple as that. The fact that he is Canadian is a huge embarrassment to the majority of Canadians.
Just my personal viewpoint.
-Chris 😉
I can not for the life of me figure out how such an infantile, vocally challenged, over expressive wanna-be musician was able to get into a recording studio!
He comes on the radio and the station gets changed. My wife and I both race for the channel selector. Simple as that. The fact that he is Canadian is a huge embarrassment to the majority of Canadians.
Just my personal viewpoint.
-Chris 😉
Apogee said:Oh, Chris....you blaspheme the musical master?????????
Especially, another Canadian???
HAHAHA.. I am really not a Neil Young fan.. I just thought this CD was nice and warm sounding.. just perfect for a little break in time 😉
Okay.. got it.. I will do the adjustment when I am feeling a little more hmmmm less tired 🙂 Not tonight. 🙂
I need to order some more silicone heat sink goo for the other side.. I noticed the gold is worn off the rca jacks.. gotta find a source for those.. any hints?
Yeah Anatech!! I got it running, with lots of help from YOU.. a thousand thank yous!
I gotta say; its really sounding wonderful.. I was going to use this as a biamp for my main system.. but it sounds so nice thru my JBL stuidio monitor I might just move it into the bedroom.. this would be a treat to lay in bed and listen to 🙂
I can't wait to back to back this against my newer model too.. just too hear the difference.. be interesting.
Gaads the guitars are just popping out of the speaker right now.. and its hard to do that with JBL's.. they are real pigs to drive. Amazing.. I am using a STOCK Eico HF88 tube preamp from the 60's.. all orginal caps even.. I was scared to refurbish this unit before this project.. NOW I am all over it... (soon as the Porsche is done).. 🙂
Guys; should I do this right and replace the two 9800 MFD caps? I hear they are pricey... digi-keys site is down now so not sure..
EDIT: Neil Young admits he has to rely on his roadies to tell him if his guitar is in tune.. he can't hear the difference.. explain a few things???
Obviously you guys have never seen him in concert. I suppose The Stones and Dylan are also not any good... LOL!
Buy these for input jacks:
CARDAS- 53446 GRFA S THICK Female jack, gold/rhodium (7/16") - chassis $16.95/pr
Go here:
http://www.partsconnexion.com/catalog/connectors_files/sheet001.html
While you're ordering, I'd consider upgrading the wire from the boards to the speaker terminals and possibly the power supply as Jon suggested while you're at it. Consider doubling up the 11.5 gauge Cardas stuff here:
http://www.partsconnexion.com/catalog/wire_files/sheet001.html
May as well do the input stuff as well with high quality smaller gauge stuff.
You might also consider buying a 1 lb roll of the quad eutectic Cardas solder here. Don't buy the lead free stuff:
http://www.partsconnexion.com/catalog/soldertoolscleaner.html
CARDAS- 60155 Cardas 1 lb roll Solder 20 awg $44.95
Also just a good source for nice parts:
http://www.partsconnexion.com
I'm not sure I can keep contributing to this thread now that I know how you guys feel about Neil...
Do you know that he still continues to record all analog (and releases on vinyl) because it sounds better????
I've also seen him tuning his guitar on stage so I'm not sure I believe the tuning comment.
Blasphemers...
I guess Madonna must be real music... LOL!
Buy these for input jacks:
CARDAS- 53446 GRFA S THICK Female jack, gold/rhodium (7/16") - chassis $16.95/pr
Go here:
http://www.partsconnexion.com/catalog/connectors_files/sheet001.html
While you're ordering, I'd consider upgrading the wire from the boards to the speaker terminals and possibly the power supply as Jon suggested while you're at it. Consider doubling up the 11.5 gauge Cardas stuff here:
http://www.partsconnexion.com/catalog/wire_files/sheet001.html
May as well do the input stuff as well with high quality smaller gauge stuff.
You might also consider buying a 1 lb roll of the quad eutectic Cardas solder here. Don't buy the lead free stuff:
http://www.partsconnexion.com/catalog/soldertoolscleaner.html
CARDAS- 60155 Cardas 1 lb roll Solder 20 awg $44.95
Also just a good source for nice parts:
http://www.partsconnexion.com
I'm not sure I can keep contributing to this thread now that I know how you guys feel about Neil...
Do you know that he still continues to record all analog (and releases on vinyl) because it sounds better????
I've also seen him tuning his guitar on stage so I'm not sure I believe the tuning comment.
Blasphemers...
I guess Madonna must be real music... LOL!
Hhehehe I swear; I heard a live interview with him and thats what he said.. he said one time they had to STOP him live in concert!
AND I did see him live 3 yrs ago ar Red Rocks in Colorado.. and he had a great show.. I've just never been a fan of his lyrics... he's a bit too much of a hippie for me...
And vinyl kicks a$$.. so I agree with him there..
Okay on the connectors.. and wires.. I'm gonna do the whole deal... do this right.. One thing I dont get about this design is he ran the input cables across the top of the big caps.. when he could have run them straight back .. so the input cables criss-cross eachother if you look at the phots you will see what I mean.. He MUST have done that for a reason.
what about this cap? Only $25.00 each.. I assume 9600 MFD would be close enough?
http://rocky.digikey.com/WebLib/Cornell Dublier Electronics/Web Data/CGS Type.pdf
Seems like since I am this far I might as well get it done?
AND I did see him live 3 yrs ago ar Red Rocks in Colorado.. and he had a great show.. I've just never been a fan of his lyrics... he's a bit too much of a hippie for me...
And vinyl kicks a$$.. so I agree with him there..
Okay on the connectors.. and wires.. I'm gonna do the whole deal... do this right.. One thing I dont get about this design is he ran the input cables across the top of the big caps.. when he could have run them straight back .. so the input cables criss-cross eachother if you look at the phots you will see what I mean.. He MUST have done that for a reason.
what about this cap? Only $25.00 each.. I assume 9600 MFD would be close enough?
http://rocky.digikey.com/WebLib/Cornell Dublier Electronics/Web Data/CGS Type.pdf
Seems like since I am this far I might as well get it done?
I just looked at the pic; my guess is the wires are long so the channel bank could be tilted outward for servicing. Beyond that, I'd bet there's not much rhyme or reason. You could shorten them a little if you wanted, just don't overdo it in case you have to service it.
What are the caps for? Main filter caps? If so, no they're not big enough. Might as well go larger as it will help with bass response and provide better filtering. You could easily double the current value. Also make sure to go the same or larger on the voltage rating.
Check out the caps that MJR just bought in the Adcom thread as a possibility. They should be just about right, although I couldn't put anything labeled Adcom inside a Threshold amp... You could just slice off the covers though...
Also, I think I was editing my last post at the same time you were typing and I added a little bit to it.
I suppose his hearing could be damaged...he's only been playing on stage for 40 years...!
Yeah, he's a hippie, but did you see Greendale? Who else do you know besides Queen, The Who, Joe Jackson and Pink Floyd that has written a rock stage show or even attempted it?
What are the caps for? Main filter caps? If so, no they're not big enough. Might as well go larger as it will help with bass response and provide better filtering. You could easily double the current value. Also make sure to go the same or larger on the voltage rating.
Check out the caps that MJR just bought in the Adcom thread as a possibility. They should be just about right, although I couldn't put anything labeled Adcom inside a Threshold amp... You could just slice off the covers though...
Also, I think I was editing my last post at the same time you were typing and I added a little bit to it.
I suppose his hearing could be damaged...he's only been playing on stage for 40 years...!
Yeah, he's a hippie, but did you see Greendale? Who else do you know besides Queen, The Who, Joe Jackson and Pink Floyd that has written a rock stage show or even attempted it?
Congrats barchetta!!11!! 
I appprove totally of you taking your time now that you are sooo close.
I think I need to get an old classic amp too. I have a new camera w/ macro so I'm ready!
I appprove totally of you taking your time now that you are sooo close.
I think I need to get an old classic amp too. I have a new camera w/ macro so I'm ready!
