Duskstalker
New Member
Hello,
I've read through alot of "C4" content on this board and there is huge competence in this board to be found on that topic - so I figured it would be a good idea to ask for assistance for my C4. I believe its the north-european version (I'm located in Germany).
I've got a C4 laying around (got stored away in the 90's and forgotten), which is in a pretty good shape (outside and inside) - but appears do be "dead"silent. I was told it was defect and when tested with a pair of headphones theres only a very slight indication of music (cd player input in both aux and tuner) with both volume and headphones volume is turned up pretty high.
I build speakers, so im confident with the soldering iron - but I've got only a veeery basic understanding of amplifier electronics. But since the C4 often has cold solder joints I was confident I could give it a shot.
I opened the C4 and reflew (reflowed?) the small board with the heatsinked voltage regulators and found that to be oddly satisfying - I always wanted to learn how to do small repairs and recapping on amplifiers, why not start here.
On a side note: All 3 buttons glow yellowish on my version - and as far as i know they should actually be red / green / green. I guess there should be some colored/coloring plasticdomes on those lightbulbs?!
The problems with my C4:
It only puts out the slightest volume over the headphones, which made me assume something is broken in the signal way - right channel is way louder than left - which is basically dead completely.
So, like said, I opened the C4 and it looked quite clean inside - little dust, little flux stains, no visible damage on the main boards, no bulged or defect capacitors - at first glance. I started reflowing the first little board with the heatsinked voltage regulators - it didn't solve the issue, but its only 20% of all solder points.
Today I pulled out the headphone board because i suspected the ribbon cables, the connector on the small one was really loose.
And there i found that alot of the capacitors on that board have corroded feet - something ive not spotted anywhere else on the board. Im pretty sure that this is number 1 culprit for the non existent audio output via headphone. this poses the question whether there actually is a problem on top of that - so i'll have to replace those first.
To my surprise I found a readily compiled recap set for the C4 on ebay consisting of nichicon fine gold / muse - which bought instantly. So i guess ill recap that thing?! Some seem to prefer Elna on certain spots on the board, but this will have to do it for me - nich gold / muse seems pretty good.
On these forums I found the information that I should go ahead and replace the 2SC458 transistors with the
KSC1845FTA - i found these pieces and they're fairly cheap - but i have no idea how much of these i'll need - does anyone have a number? Do they have the same pin out as the original ones?
Another thing would be the 2x 1n4148 diode to replace the VD1212 varisors - I found multiple parts that have that part number. What do I need? Normal or ultra fast diodes? 100mA? 150 mA? 300mA? 75V 100V? 150V?
There is one part on that board that worries me, tho - its the 3rd big heatsinked voltage regulator between the rods for the input and phono selector switches.
The heatsink was glued to the pcb, but ripped itself loose, solder seems ok, I'll reflow it anyway. i guess these things can die, too? are there parts to replace it, in case this regulator overheated and died? - there are signs of heat on the resistor and the "switch-rod" next to it - the resistor does measure something, but i dont know whether thats the resistance for another trace or the actual resistor.
I tried to remove one of the rods to unscrew the heatsink, but the rod secured in 3 places - thats where i stopped today.
I guess it would be easier to unsolder it to apply new thermal paste? Should I reglue it? Thermal resistant silicone to secure it back? Or not glue it at all and handle with care?
I'll get my new caps sometime next week and I really hope I can make some progress with these.
I'll happily provide pictures, but I just couldn't get some today.
Thanks alot for reading through that wall of text and your help!
I've read through alot of "C4" content on this board and there is huge competence in this board to be found on that topic - so I figured it would be a good idea to ask for assistance for my C4. I believe its the north-european version (I'm located in Germany).
I've got a C4 laying around (got stored away in the 90's and forgotten), which is in a pretty good shape (outside and inside) - but appears do be "dead"silent. I was told it was defect and when tested with a pair of headphones theres only a very slight indication of music (cd player input in both aux and tuner) with both volume and headphones volume is turned up pretty high.
I build speakers, so im confident with the soldering iron - but I've got only a veeery basic understanding of amplifier electronics. But since the C4 often has cold solder joints I was confident I could give it a shot.
I opened the C4 and reflew (reflowed?) the small board with the heatsinked voltage regulators and found that to be oddly satisfying - I always wanted to learn how to do small repairs and recapping on amplifiers, why not start here.
On a side note: All 3 buttons glow yellowish on my version - and as far as i know they should actually be red / green / green. I guess there should be some colored/coloring plasticdomes on those lightbulbs?!
The problems with my C4:
It only puts out the slightest volume over the headphones, which made me assume something is broken in the signal way - right channel is way louder than left - which is basically dead completely.
So, like said, I opened the C4 and it looked quite clean inside - little dust, little flux stains, no visible damage on the main boards, no bulged or defect capacitors - at first glance. I started reflowing the first little board with the heatsinked voltage regulators - it didn't solve the issue, but its only 20% of all solder points.
Today I pulled out the headphone board because i suspected the ribbon cables, the connector on the small one was really loose.
And there i found that alot of the capacitors on that board have corroded feet - something ive not spotted anywhere else on the board. Im pretty sure that this is number 1 culprit for the non existent audio output via headphone. this poses the question whether there actually is a problem on top of that - so i'll have to replace those first.
To my surprise I found a readily compiled recap set for the C4 on ebay consisting of nichicon fine gold / muse - which bought instantly. So i guess ill recap that thing?! Some seem to prefer Elna on certain spots on the board, but this will have to do it for me - nich gold / muse seems pretty good.
On these forums I found the information that I should go ahead and replace the 2SC458 transistors with the
KSC1845FTA - i found these pieces and they're fairly cheap - but i have no idea how much of these i'll need - does anyone have a number? Do they have the same pin out as the original ones?
Another thing would be the 2x 1n4148 diode to replace the VD1212 varisors - I found multiple parts that have that part number. What do I need? Normal or ultra fast diodes? 100mA? 150 mA? 300mA? 75V 100V? 150V?
There is one part on that board that worries me, tho - its the 3rd big heatsinked voltage regulator between the rods for the input and phono selector switches.
The heatsink was glued to the pcb, but ripped itself loose, solder seems ok, I'll reflow it anyway. i guess these things can die, too? are there parts to replace it, in case this regulator overheated and died? - there are signs of heat on the resistor and the "switch-rod" next to it - the resistor does measure something, but i dont know whether thats the resistance for another trace or the actual resistor.
I tried to remove one of the rods to unscrew the heatsink, but the rod secured in 3 places - thats where i stopped today.
I guess it would be easier to unsolder it to apply new thermal paste? Should I reglue it? Thermal resistant silicone to secure it back? Or not glue it at all and handle with care?
I'll get my new caps sometime next week and I really hope I can make some progress with these.
I'll happily provide pictures, but I just couldn't get some today.
Thanks alot for reading through that wall of text and your help!
