Oops ... thanks ! Indeed foolish of me and will rotate vents above pcba as designed 🙏🙏
PS: guess I now know why I change the 12 cover screws to Philips head ones 😅
PS: guess I now know why I change the 12 cover screws to Philips head ones 😅
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Hey Dan, how is your journey so far ? As you dun even have to spend on outside repair shop to recap, I strongly recommend you to do so and do consider same high temp hybrid polymer ones and upsized mundorf caps.
Cheers.
Change ALL capacitors !
In my 400xi, ALL were measured moderately to severely bad.
It was a timebomb. Now it is as new.
No signs of overheating in the past.
Clean the PCB professionally.
Long story short: do the total refresh if you want to use it for another 20 or so years.
It's worth it !
At least it is to me.
Cheers!
In my 400xi, ALL were measured moderately to severely bad.
It was a timebomb. Now it is as new.
No signs of overheating in the past.
Clean the PCB professionally.
Long story short: do the total refresh if you want to use it for another 20 or so years.
It's worth it !
At least it is to me.
Cheers!
Elco juice ? Think (and hope) just dust due to open ventilation and mentioned distortion seems to indicate cap issue that a bit of cleaning (before recap) to know all ok and then recap will be fine ... like me was and do keep us posted on expected good news. Cheers. 🤞🤞
Cannot think of any better input coupling caps than Nichicon ES bipolar that we are both using .. refined, clear and yet organic as well as available cheaply. Only issue is that it is 85c rated and not 105c that I wish for to be used for all new cap replacement in this rather hot amp ... but changing in another 5-10 yrs will not be too difficult since on top preamp pcba 🥳🥳
Thank you for sharing. Do you have the circuit schematic of Krell KAV-280p? Can you share it?
Attachments
Hey, all, even though I had the schematic, it took me this long to take care of mine lol. I wish I had taken more pictures.
I see that some people mentioned that they replaced some of the transistors. Does anyone have an opinion on that? I would like to know, if it benefits the amp, transistors should be replaced, and what the replacements should be. I am a strong believer in upgrading through transistors that give lower noise and such. Generally when I rebuild an amplifier from the 70s, I put as many low noise transistors in it as I can. Anyways, for all the polar capacitors on top (68uf 16v) I was planning on using Nichicon KA as someone else did previously in this thread. I ordered a couple hundred, but I kind of wanted to get going on the project so instead I put in 100uF 25v Nichicon Fine Gold. For the nonpolar (47uF 25v) I used Nichicon ES.
Pretty much all of the through capacitors measured just fine, but I figured if I’m tearing into this, I’m going to do them all anyway. I replaced the 3300uF 35v with Nichicon… KW I think.
I forgot to get photos of the bottom side, but all of the 47uF 63v were replaced with Panasonic FR of the same value, all nonpolar replaced with Nichicon ES and then all of the polar 47uF capacitors were replaced with Nichicon KA. I increased the size of the filters, going as tall as I could. I literally don’t think I can even go a millimeter taller. But everything fits perfectly fine. Went from 54,400 uF to 65,600 uF. Not a huge jump, but healthy enough. I also put some thermal compound underneath the two bridge rectifiers and took care of all of the capacitors on the face plate.
First power up
I now have it playing some music on some throwaway speakers. Just running it through its pieces prior to hooking up good speakers. Running great for what it is on small 3 inch drivers.
A couple of questions: are there any instructions on adjustments? Bias? Anything?
And secondly, if there are any recommendations asked to transistor replacement, please let me know.
Also, I have not decided yet, but I am considering replacing all of the front LEDs and the numeric display with all white. I think that would look kind of nice on a black face with white lettering.
Dan
I see that some people mentioned that they replaced some of the transistors. Does anyone have an opinion on that? I would like to know, if it benefits the amp, transistors should be replaced, and what the replacements should be. I am a strong believer in upgrading through transistors that give lower noise and such. Generally when I rebuild an amplifier from the 70s, I put as many low noise transistors in it as I can. Anyways, for all the polar capacitors on top (68uf 16v) I was planning on using Nichicon KA as someone else did previously in this thread. I ordered a couple hundred, but I kind of wanted to get going on the project so instead I put in 100uF 25v Nichicon Fine Gold. For the nonpolar (47uF 25v) I used Nichicon ES.
Pretty much all of the through capacitors measured just fine, but I figured if I’m tearing into this, I’m going to do them all anyway. I replaced the 3300uF 35v with Nichicon… KW I think.
I forgot to get photos of the bottom side, but all of the 47uF 63v were replaced with Panasonic FR of the same value, all nonpolar replaced with Nichicon ES and then all of the polar 47uF capacitors were replaced with Nichicon KA. I increased the size of the filters, going as tall as I could. I literally don’t think I can even go a millimeter taller. But everything fits perfectly fine. Went from 54,400 uF to 65,600 uF. Not a huge jump, but healthy enough. I also put some thermal compound underneath the two bridge rectifiers and took care of all of the capacitors on the face plate.
First power up
I now have it playing some music on some throwaway speakers. Just running it through its pieces prior to hooking up good speakers. Running great for what it is on small 3 inch drivers.
A couple of questions: are there any instructions on adjustments? Bias? Anything?
And secondly, if there are any recommendations asked to transistor replacement, please let me know.
Also, I have not decided yet, but I am considering replacing all of the front LEDs and the numeric display with all white. I think that would look kind of nice on a black face with white lettering.
Dan
Hi Dan, Nice ! Especially Nichicon ES for bipolar input coupling ones 👍👍
A couple of photos for the display and leds which may help you since I am just having its 24 resistors swapped to fine tune its brightness .. just note that the plastic len for the display is dark red and I had modded blue ones for all except mute led when you are considering white one.
No planned transistor swap and cannot help you on that nor done any biasing as my repair workshop and another online owner reported not needed .. dunno enuff to advise.
Cheers.
Richard
A couple of photos for the display and leds which may help you since I am just having its 24 resistors swapped to fine tune its brightness .. just note that the plastic len for the display is dark red and I had modded blue ones for all except mute led when you are considering white one.
No planned transistor swap and cannot help you on that nor done any biasing as my repair workshop and another online owner reported not needed .. dunno enuff to advise.
Cheers.
Richard
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Awesome, that’s great to know. Are the original lights still red even though they have a red lens? I’ve been running it pretty loudly and it seems like he’s doing just dandy. Has anyone done any adjustments to theirs after doing the work? I’m guessing especially after replacing transistors, it would be a good idea.
Dan
Hi Dan,
Yes they are and forgot to include their photos that will be much clearer.
First changed blue led despite usually dimmer due to higher drive current turned out way too bright and already blue plastic len .. hence the needed resistors swap and also one possible cause of burn out segments of original stock red display.
Cheers.
Yes they are and forgot to include their photos that will be much clearer.
First changed blue led despite usually dimmer due to higher drive current turned out way too bright and already blue plastic len .. hence the needed resistors swap and also one possible cause of burn out segments of original stock red display.
Cheers.
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Thank you, kind of freaked me out at first cause I saw that you said that there are 25 V capacitors on the front panel and I know I only installed 16v. So I ran downstairs to just double check and my front panel definitely only had 16 V
I have quite a lot to do, so I’m gonna probably just run it with red LEDs for a bit. Thank you for the tip on the resistors I’ll swap to white and maybe even put a diffused panel in front.
Dan.
I have quite a lot to do, so I’m gonna probably just run it with red LEDs for a bit. Thank you for the tip on the resistors I’ll swap to white and maybe even put a diffused panel in front.
Dan.
Haha .. you saw wrong .. not capacitors but resistors for the display .. 3 more in my case for the leds.
For front panel e capacitors, mine are certainly 25v ones of 1000uf Nichicons originally but perhaps 16v in yours are fine if stock or found needing update/upgrade or simply run of 16v ones in mine.
Cheers.
For front panel e capacitors, mine are certainly 25v ones of 1000uf Nichicons originally but perhaps 16v in yours are fine if stock or found needing update/upgrade or simply run of 16v ones in mine.
Cheers.
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