crooner
Tube Marantzed
Hi Guys and Gals!
I've always been interested in learning how to stuff twist lock caps with modern miniature electrolytics. It respects the classic appearance of the unit being restored.
My first patient is a mint cosmetic condition factory wired Dynaco SCA-35 integrated amp from 1965. Frequently, SCA's are "updated" with all sorts of modern caps and PCB boards. I wanted to have a daily driver and also preserve the originality of the unit as much as possible.
I was checking the web and also some very useful posts by AK member "Kcin", on how to proceed with stuffing the cans.
I ended up going with the hacksaw approach instead of the pipe cutter to open the cans. Yeah, it's a little crude but if done carefully the results are quite acceptable. The employee at the Home Depot messed up a can I brought over when he attempted to use the pipe cutter. Not encouraging. But of course, YMMV.
I reused the original Aerovox cans but used NOS bottom twist lock rings from other cans. I was able to reuse the phenolic wafer and tabs from one can. The other came from a NOS donor. I drilled holes on the phenolic wafer to guide the leads to to the tabs.
I stuffed the cans with Nichicon low impedance 105 degree 450V electrolytics. Had to determine the best compromise between physical dimensions and capacitance. High capacitance is useful but the caps may be too large to fit inside the can.
For the dual can, I went for a pair of 82 uf radial units. The original spec is 50 uF. Just the right size to fit comfortably inside the can.
The quad can required a little more ingenuity to fit all four caps. The values chosen were 68uF@ 450V for the three high voltage sections and 150uF @ 50V for the cathode bypass.
Everything was epoxied in place and clamped for 4 hours to ensure a good fit.
As you can see from the pics, the results are very encouraging!
Aside from rebuilding the cans, I replaced the two silicon rectifiers with high speed SF4007 units and added an inrush limiter.
Everything else looks as stock as it gets.
As for the tubes, the original Dynaco branded RCA 7199s and Telefunken 12AX7s tested excellent. Unfortunately one of the original RCA 6BQ5's was a dud, so I ordered a cheap matched quad of Sovtek EL84s for now.
Tonight I'll do the smoke test and post my findings!
I've always been interested in learning how to stuff twist lock caps with modern miniature electrolytics. It respects the classic appearance of the unit being restored.
My first patient is a mint cosmetic condition factory wired Dynaco SCA-35 integrated amp from 1965. Frequently, SCA's are "updated" with all sorts of modern caps and PCB boards. I wanted to have a daily driver and also preserve the originality of the unit as much as possible.
I was checking the web and also some very useful posts by AK member "Kcin", on how to proceed with stuffing the cans.
I ended up going with the hacksaw approach instead of the pipe cutter to open the cans. Yeah, it's a little crude but if done carefully the results are quite acceptable. The employee at the Home Depot messed up a can I brought over when he attempted to use the pipe cutter. Not encouraging. But of course, YMMV.
I reused the original Aerovox cans but used NOS bottom twist lock rings from other cans. I was able to reuse the phenolic wafer and tabs from one can. The other came from a NOS donor. I drilled holes on the phenolic wafer to guide the leads to to the tabs.
I stuffed the cans with Nichicon low impedance 105 degree 450V electrolytics. Had to determine the best compromise between physical dimensions and capacitance. High capacitance is useful but the caps may be too large to fit inside the can.
For the dual can, I went for a pair of 82 uf radial units. The original spec is 50 uF. Just the right size to fit comfortably inside the can.
The quad can required a little more ingenuity to fit all four caps. The values chosen were 68uF@ 450V for the three high voltage sections and 150uF @ 50V for the cathode bypass.
Everything was epoxied in place and clamped for 4 hours to ensure a good fit.
As you can see from the pics, the results are very encouraging!
Aside from rebuilding the cans, I replaced the two silicon rectifiers with high speed SF4007 units and added an inrush limiter.
Everything else looks as stock as it gets.
As for the tubes, the original Dynaco branded RCA 7199s and Telefunken 12AX7s tested excellent. Unfortunately one of the original RCA 6BQ5's was a dud, so I ordered a cheap matched quad of Sovtek EL84s for now.
Tonight I'll do the smoke test and post my findings!
