tchuck
Super Member
Hey guys/gals,
So, I have these two Sansui 7070s that I just love to death. Well, one of them I love to death and the other is a parts unit I found locally for a song, but I love it symbolically for what it used to be and for it's future contributions. Namely keeping the other one up and running. Anyway, I've been reading a lot lately about capacitors and in light of the realization that the electrolytics in my beloved 7070s are nearing the end of their lifespans, I've decided to embark upon an epic recapping project. Specifically I'd like to replace all of them in both units. Having never done anything of this magnitude before, I'm very much still in the researching stage...or at least I was until I found these:
I'm not really clear on the electrical effects of over-sizing these caps by this much (the original 7070 parts are 50V 10,000uf) and honestly if I didn't have a complete backup receiver I wouldn't have even considered it. Things being as they are I had a beer last night and warmed up the soldering iron...
Here are the original caps, snug in their homes:
My backup baby under the knife:
Old vs new:
Emptiness:
Now some of you may be thinking "wow, those new caps are big!" and the more astute among you may be thinking "wow, those caps are WAY TOO big!" Well, you're both right. In addition to being larger in height and diameter, the terminals are farther apart and offset differently. Ergo, I had to massage the Mc terminals a bit in order to match the spacing. Observe:
Sansui
McIntosh post modification
Note the spacing doesn't match on the micrometer dial. That's because the terminal slots on the board allowed for a slightly larger spacing. Considering I'm already in sketchy territory by bending them at all, I elected to utilize that extra room and bend them as little as possible.
About this time I'm thinking to myself "Ha! This is going to be soooo easy!" I bent the third post (a soldering lug) over and installed the cap with the bent terminals. So far, so good. I crack beer #2 and test fit cap #2. That's when my elation ends. The second cap is nowhere close to fitting due to the offset posts. The orientation is such that the soldering lugs face each other, and on the 7070 board there isn't room for these huge cans. The only way I can see that it could work is for the terminals to be swapped so that the "big half" faces away from the other cap, or if the offset was reversed which would have the same effect on the orientation. I drown my sorrows in beer #2 and hatch a plan.
Enter beer #3 and capacitor mod #2.
These are two small picture hangers bent into a suitable shape and attached to the bent terminals of the second cap with plumbing solder at their base, and electrical solder at their ends. I had to use three heat sinks for each post in order to heat up the components enough to work while not bearing close witness to a small chemical explosion, but it worked. Contrary to how it looks in the pic, the connections are very solid and electrically sound. The result is that installed location is moved over about an inch, which is the perfect amount to fit it next to the first one. Elation resumes.
I stuck a couple bumpers on the exposed portions of the frankencap and reinstalled it on the board.
This first installation of the story does have a happy ending, but I have to warn you it gets a little hairy here...
As I said before, all of this is being done on my backup receiver, and I'm three stout beers deep in the late evening by this point, so I'm not being as careful and methodical as I could have been. I made sure that the new caps were secure in their new locations, plugged in the receiver to my variac set to 30V, clicked it on and went upstairs to hang out for a bit. I came back down to check after about 20min - everything looked good - and bumped up the variac to 70V. I heard the relay engage so I plugged in a couple of random full range drivers I have lying around. ie, a set I wouldn't miss. After 10 or so minutes of uneventful "burn-in" time I gently bumped up the variac to 120V and ever so slightly turned the volume knob. What happened next made my heart sink. From the speakers I expected to hear beautiful music I in fact heard the most horrible muted scratchy sound I've ever heard out of any speaker. The volume knob was practically unresponsive, the power meters didn't move at all. Ugh. I turned everything off and went to bed a very disappointed dude. :tears:
I went back down tonight - sober - to inspect my work and see if I made any stupid mistakes that might be obvious to my fresh eyes. This is what I found:
As you can see, in my drunken haste last night I inadvertently soldered over the "moat" between the + terminal of caps #1 and #2, which had created a short that also blew three out of the four fuses on the main board.
Fortunately all it took was removing the solder bridge and replacing the three fuses for everything to return to normal. I performed the DC output and bias adjustments in the FSM and am more than happy to report that it sounds GREAT! I'd have to swap in exact replacements on my other 7070 in order to say whether the Mc caps are in fact an improvement but in it's current condition my "backup" unit sounds WAY better than the other one ever did! I'm definitely going to swap the Mc powered main boards now so i can test it on some real speakers. Needless to say this was a big success. Especially for me personally considering my huge lack of experience or electrical knowledge. 
Cue banana:
I haven't ordered the rest of the caps yet. My tentative plan is to get Elna Silmic II caps for everything in the signal path, but beyond that I haven't really decided. Any suggestions?
So, I have these two Sansui 7070s that I just love to death. Well, one of them I love to death and the other is a parts unit I found locally for a song, but I love it symbolically for what it used to be and for it's future contributions. Namely keeping the other one up and running. Anyway, I've been reading a lot lately about capacitors and in light of the realization that the electrolytics in my beloved 7070s are nearing the end of their lifespans, I've decided to embark upon an epic recapping project. Specifically I'd like to replace all of them in both units. Having never done anything of this magnitude before, I'm very much still in the researching stage...or at least I was until I found these:
I'm not really clear on the electrical effects of over-sizing these caps by this much (the original 7070 parts are 50V 10,000uf) and honestly if I didn't have a complete backup receiver I wouldn't have even considered it. Things being as they are I had a beer last night and warmed up the soldering iron...
Here are the original caps, snug in their homes:
My backup baby under the knife:
Old vs new:
Emptiness:
Now some of you may be thinking "wow, those new caps are big!" and the more astute among you may be thinking "wow, those caps are WAY TOO big!" Well, you're both right. In addition to being larger in height and diameter, the terminals are farther apart and offset differently. Ergo, I had to massage the Mc terminals a bit in order to match the spacing. Observe:
Sansui
McIntosh post modification
Note the spacing doesn't match on the micrometer dial. That's because the terminal slots on the board allowed for a slightly larger spacing. Considering I'm already in sketchy territory by bending them at all, I elected to utilize that extra room and bend them as little as possible.
About this time I'm thinking to myself "Ha! This is going to be soooo easy!" I bent the third post (a soldering lug) over and installed the cap with the bent terminals. So far, so good. I crack beer #2 and test fit cap #2. That's when my elation ends. The second cap is nowhere close to fitting due to the offset posts. The orientation is such that the soldering lugs face each other, and on the 7070 board there isn't room for these huge cans. The only way I can see that it could work is for the terminals to be swapped so that the "big half" faces away from the other cap, or if the offset was reversed which would have the same effect on the orientation. I drown my sorrows in beer #2 and hatch a plan.
Enter beer #3 and capacitor mod #2.
These are two small picture hangers bent into a suitable shape and attached to the bent terminals of the second cap with plumbing solder at their base, and electrical solder at their ends. I had to use three heat sinks for each post in order to heat up the components enough to work while not bearing close witness to a small chemical explosion, but it worked. Contrary to how it looks in the pic, the connections are very solid and electrically sound. The result is that installed location is moved over about an inch, which is the perfect amount to fit it next to the first one. Elation resumes.
I stuck a couple bumpers on the exposed portions of the frankencap and reinstalled it on the board.
This first installation of the story does have a happy ending, but I have to warn you it gets a little hairy here...
As I said before, all of this is being done on my backup receiver, and I'm three stout beers deep in the late evening by this point, so I'm not being as careful and methodical as I could have been. I made sure that the new caps were secure in their new locations, plugged in the receiver to my variac set to 30V, clicked it on and went upstairs to hang out for a bit. I came back down to check after about 20min - everything looked good - and bumped up the variac to 70V. I heard the relay engage so I plugged in a couple of random full range drivers I have lying around. ie, a set I wouldn't miss. After 10 or so minutes of uneventful "burn-in" time I gently bumped up the variac to 120V and ever so slightly turned the volume knob. What happened next made my heart sink. From the speakers I expected to hear beautiful music I in fact heard the most horrible muted scratchy sound I've ever heard out of any speaker. The volume knob was practically unresponsive, the power meters didn't move at all. Ugh. I turned everything off and went to bed a very disappointed dude. :tears:
I went back down tonight - sober - to inspect my work and see if I made any stupid mistakes that might be obvious to my fresh eyes. This is what I found:
As you can see, in my drunken haste last night I inadvertently soldered over the "moat" between the + terminal of caps #1 and #2, which had created a short that also blew three out of the four fuses on the main board.
Fortunately all it took was removing the solder bridge and replacing the three fuses for everything to return to normal. I performed the DC output and bias adjustments in the FSM and am more than happy to report that it sounds GREAT! I'd have to swap in exact replacements on my other 7070 in order to say whether the Mc caps are in fact an improvement but in it's current condition my "backup" unit sounds WAY better than the other one ever did! I'm definitely going to swap the Mc powered main boards now so i can test it on some real speakers. Needless to say this was a big success. Especially for me personally considering my huge lack of experience or electrical knowledge. Cue banana:
I haven't ordered the rest of the caps yet. My tentative plan is to get Elna Silmic II caps for everything in the signal path, but beyond that I haven't really decided. Any suggestions?
