Dynaco ST-70 Startup

[David_NC]

I finally finished 'restoring' my ST-70 last night. I replaced all the caps, most resistors, and the selenium rectifier. All that's left is to replace the rusty hardware (aka screws) on the chassis, which I'll do tonight. This is leading up to the scary part - powering it on for the first time, setting bias, and making sure it works properly. It was suggested that I buy a cheap set of tubes for this part, since mine has the original Dynaco and Tung Sol tubes in it. I see Electro-Harmonix and JJ are about the cheapest brand name EL34's that I can find. Are there any others I should be considering? I have 7199's and will use 6U8A on an adapter at first. I don't think I missed anything that's needed to get this back into shape.
Here are some pics of it from last night. I see I still need to remove my labels (AKA blue painter's tape), clean the chassis, and neaten it up in general a bit. I'll rewire the switch and fuse so that they are both on the hot line. I'm not sure sure I like having the neutral switched. Once it passes the preliminary tests, and I get some listening time in on it, I'll replace the stereo/mono switch with a volume pot and perhaps move the RCA jacks to the rear. Somebody replaced them in the past and drilled the front chassis, so it's not gonna look good there without doing something.

 

[bbqjoe]

I finally finished 'restoring' my ST-70 last night. I replaced all the caps, most resistors, and the selenium rectifier. All that's left is to replace the rusty hardware (aka screws) on the chassis, which I'll do tonight. This is leading up to the scary part - powering it on for the first time, setting bias, and making sure it works properly. It was suggested that I buy a cheap set of tubes for this part, since mine has the original Dynaco and Tung Sol tubes in it. I see Electro-Harmonix and JJ are about the cheapest brand name EL34's that I can find. Are there any others I should be considering? I have 7199's and will use 6U8A on an adapter at first. I don't think I missed anything that's needed to get this back into shape.
Here are some pics of it from last night. I see I still need to remove my labels (AKA blue painter's tape), clean the chassis, and neaten it up in general a bit. I'll rewire the switch and fuse so that they are both on the hot line. I'm not sure sure I like having the neutral switched. Once it passes the preliminary tests, and I get some listening time in on it, I'll replace the stereo/mono switch with a volume pot and perhaps move the RCA jacks to the rear. Somebody replaced them in the past and drilled the front chassis, so it's not gonna look good there without doing something.

You could always fill the RCA holes with a couple of lights, or some toggles that do or indicate absolutely nothing, you know, just for the eye candy, and to keep a future owner guessing.
I wish you good luck.

 

[David_NC]

You could always fill the RCA holes with a couple of lights, or some toggles that do or indicate absolutely nothing, you know, just for the eye candy, and to keep a future owner guessing.
I wish you good luck.

LOL toggles that switch on indicator lights!

 

[Dave451]

Looking good! As for tubes, I worked on a Fisher SA-300B that had EH EL34's and thought they sounded quite good. The Tung Sol EL34B's sounded terrific in a Scott 272. Neither will break the bank; the EH's are quite economical, in fact. Good luck with the start up and enjoy the ST-70.

 

[Lavane]

I wonder why someone drilled a second set of jack holes in the front? There is already a set of jack holes on the front.

 

[David_NC]

I wonder why someone drilled a second set of jack holes in the front? There is already a set of jack holes on the front.

Most likely due to the fact that the originals were really close, and many RCA plugs are too big to fit. I'd have considered doing the same, but not like that! I've got a friend with access to a CNC machine, and I may just get him to make me a plate to cover all that up, especially since I'd like to move the RCA plugs to the back anyway.