Of course Lasse, we're just talking. Civilized deliberation is scarce these days but is necessary to come up with optmial solutions!
!
I'm really not convinced about the sideways mounting possibility... It involves drilling holes in the stock pcb large enough to pass tie-wraps and one would need two tie-wraps for a stable mounting - 4 holes per position and some will inevitably have to pass through existing traces, exposing the copper underneath the conformal coating. Then there's the need to solder thick wires to the board; these will represent a risk of lifting the traces off the pcb with any movement. Since the contacts will be under the caps the wires will have to be formed in a fancy way and then connect to snap-in terminals which are not designed for to receive wires. The pins will protrude from the sides, a risk even if they are covered with shrink tubing. The more I think about it the more dodgy it sounds.
Plus the little 3900uF caps have three times the endurance of the 22mF, are rated for higher temperature, and everyone say multiple caps in paralllel sound better than a single one. Twice the price but worth it I think in the long run - I'm not the kind of guy who regards re-capping as a hobby 😎
Plus the little 3900uF caps have three times the endurance of the 22mF, are rated for higher temperature, and everyone say multiple caps in paralllel sound better than a single one. Twice the price but worth it I think in the long run - I'm not the kind of guy who regards re-capping as a hobby 😎
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Are these too tall?
https://mou.sr/3ekTwLY
looks like there is quite an array of 22,000 uF caps @50V
https://www.mouser.com/c/passive-co...capacitance=22000 uF&voltage rating dc=50 VDC
Given going with a 5 x 4.7mF, the daughterboards will need to be mechanically secure (for transport), I suggest them should have some short pillars glued on around the circumference to keep them from moving - given the solder pins are soldered with definite pressure on the boards these should act as solid support.
And yes using each side of the daughterboard as a plane is good, little chance of frying a trace if the caps are accidentally shorted out (on the daughterboards at least!). Standard 1oz PCB copper is 0.5 milliohms per square - planes are very low resistance!
And yes using each side of the daughterboard as a plane is good, little chance of frying a trace if the caps are accidentally shorted out (on the daughterboards at least!). Standard 1oz PCB copper is 0.5 milliohms per square - planes are very low resistance!
I'll do like when soldering large electrolytics, put small dabs of electronics grade silicon around the circumference. I wait one day for complete hardening before flipping the board to solder. Advantage over pcb glue is that the dabs can be unglued by applying a bit of force underneath with a scraper.
Received my fancy little daughter boards from JLCPCB this week. Looks good, fits nicely on the amp's main board. At less than 5 canadian bucks for 5 pieces delivered, it's not worth doing proto boards anymore and one could never get that level of finished product by hand.
Caps are sorted into a matched quad, ready to solder ! The caps are mostly on the lower side of their tolerances, groups are 17.65mF total instead of the theorical 19.5mF (3.9mF x 5). Surprising for fresh caps (mfg date week 35 of 2023), but then that's only -8% of spec. The original caps were 22mF, a drop of almost 20%... Now I'm confident that 30+ years of electrolytic capacitor technology improvements will compensate for this reduction in total capacity. Or am I being too optimistic? Alas I may not be able to complete the mod before the second week of 2024... Damn holidays! 😎
Caps are sorted into a matched quad, ready to solder ! The caps are mostly on the lower side of their tolerances, groups are 17.65mF total instead of the theorical 19.5mF (3.9mF x 5). Surprising for fresh caps (mfg date week 35 of 2023), but then that's only -8% of spec. The original caps were 22mF, a drop of almost 20%... Now I'm confident that 30+ years of electrolytic capacitor technology improvements will compensate for this reduction in total capacity. Or am I being too optimistic? Alas I may not be able to complete the mod before the second week of 2024... Damn holidays! 😎
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EPILOGUE - Introducing the "Revolver" mod
So for posterity here it is folks, the completed project. As you might have guessed, the mod gets its name from the arrangement of the caps on the daughter boards, akin to a five-round revolver barrel 😎 For anyone wondering if a daughter board could be a viable alternative to a capacitor gone unobtainium, this proves that it definitively can be.
BEFORE
AFTER
From another angle...
BEFORE
AFTER
These Rega clamshell cases are pretty crammed and one needs to isolate the metallic case of the capacitors, especially the negative rail ones, to avoid them shorting to the grounded case during dissassembly. This is because my method to dissassemble them involves turning the case upside down and the main PCB isn't secured to anything once you unscrew the U-bar over the output transistors in the middle left above; so being the tallest parts of the board the caps can touch the case. Thankfully the isolators of the original caps were removeable so I salvaged and glued them to the top of the new caps with electronics grade silicone. Kills the look a bit but this is necessary safety.
What about the sound you might ask? Like I mentioned in the previous post the new caps are mostly on the lower side of their tolerances, groups are 17.65mF total instead of the theorical 19.5mF (3.9mF x 5). The original caps were 22mF, a drop of almost 20%... I was hoping that five pieces in parallel combined with 35 years of electrolytic capacitor technology improvements would compensate for this reduction in total capacity; and I wasn't disapointed.
Now it is unfair to compare tired old 1990's caps to fresh 2023 stock. However this amp has been my main amp and I listened to it most every day for the last 20 years and all I can say is that I don't recall it sounded as good. Definitively foot-tapping factor improvement. Really percussive and deep bass; but the whole tonal balance has changed to a more "enveloping" soundstage. All in all it brings new life to this old timer of an amp.
This was the most challenging part of the complete amp re-capping project because of the odd form factor of the parts - I'm happy it is done with satisfactory results. Plus these puppies are rated 10000 Hrs @ 105°C so I should be done for a good while.
Now only have the other 45 capacitors to replace 😱 At least the rest are of standard form factors... Thanks to all for your input and suggestions.
- Joris
So for posterity here it is folks, the completed project. As you might have guessed, the mod gets its name from the arrangement of the caps on the daughter boards, akin to a five-round revolver barrel 😎 For anyone wondering if a daughter board could be a viable alternative to a capacitor gone unobtainium, this proves that it definitively can be.
BEFORE
AFTER
From another angle...
BEFORE
AFTER
These Rega clamshell cases are pretty crammed and one needs to isolate the metallic case of the capacitors, especially the negative rail ones, to avoid them shorting to the grounded case during dissassembly. This is because my method to dissassemble them involves turning the case upside down and the main PCB isn't secured to anything once you unscrew the U-bar over the output transistors in the middle left above; so being the tallest parts of the board the caps can touch the case. Thankfully the isolators of the original caps were removeable so I salvaged and glued them to the top of the new caps with electronics grade silicone. Kills the look a bit but this is necessary safety.
What about the sound you might ask? Like I mentioned in the previous post the new caps are mostly on the lower side of their tolerances, groups are 17.65mF total instead of the theorical 19.5mF (3.9mF x 5). The original caps were 22mF, a drop of almost 20%... I was hoping that five pieces in parallel combined with 35 years of electrolytic capacitor technology improvements would compensate for this reduction in total capacity; and I wasn't disapointed.
Now it is unfair to compare tired old 1990's caps to fresh 2023 stock. However this amp has been my main amp and I listened to it most every day for the last 20 years and all I can say is that I don't recall it sounded as good. Definitively foot-tapping factor improvement. Really percussive and deep bass; but the whole tonal balance has changed to a more "enveloping" soundstage. All in all it brings new life to this old timer of an amp.
This was the most challenging part of the complete amp re-capping project because of the odd form factor of the parts - I'm happy it is done with satisfactory results. Plus these puppies are rated 10000 Hrs @ 105°C so I should be done for a good while.
Now only have the other 45 capacitors to replace 😱 At least the rest are of standard form factors... Thanks to all for your input and suggestions.
- Joris
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