dynaco SCA-35 start up

[k**rkleclaire]

Curious, I have a dynaco SCA-35. I am familiar with a slow warm up on a variac with a tube-rectified unit but the SCA-35 has diodes. Hmm?
I’m not really interested in reforming the caps as I plan on recapping I only want to check the PT. Just disconnect the leads and go for it? Any advice?
Thanks,
Kirk

 

[kansei]

What I usually do is as follows (this may not be the best way, but here it is)

- remove all tubes first (you can clip the diodes to be extra safe, they probably need to be replaced anyway)
- connect to variac and bring up to about 50v
- leave at 50v for a few minutes, watch and smell for smoke, listen to noises of shorted items
- measure voltage coming out of the PT, should be about half of normal (remember, you're at 50v on the variac)
- test all the tubes on the tube tester
- disconnect power, then plug all tubes back in, connect "test" speakers and RCA inputs
- turn up the variac until the filaments glow, you should hear something out of the speakers unless there's a catastrophic failure
- viola!
- now, recap then test again

 

[k**rkleclaire]

What I usually do is as follows (this may not be the best way, but here it is)

- remove all tubes first (you can clip the diodes to be extra safe, they probably need to be replaced anyway)
- connect to variac and bring up to about 50v
- leave at 50v for a few minutes, watch and smell for smoke, listen to noises of shorted items
- measure voltage coming out of the PT, should be about half of normal (remember, you're at 50v on the variac)
- test all the tubes on the tube tester
- disconnect power, then plug all tubes back in, connect "test" speakers and RCA inputs
- turn up the variac until the filaments glow, you should hear something out of the speakers unless there's a catastrophic failure
- viola!
- now, recap then test again

Thanks....I'm going to give it a try...then put in a parts order
Kirk