Another ST-70 upgrade - completed...

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Yeah, nothing that you haven't heard or seen before. Upgraded with Shannon's board with new sockets, inputs, power cord, and wiring job etc. The amp was fuctional when I got it and was semi-decent to look at, but the chassis needed some help. So, I found a formula that worked for me for polishing up a dull chassis: gently scrub with Fast Orange or any other pumice using a cotton rag. This really helps get rid of that dull look. What a difference it makes! Dry first then spread an ample amount of Turtlewax Chrome Polish. It will form a white film as it dries, which can be buffed to shine. Repeat a few times. The polish can be purchased for 2.5 bucks at Kragen (so called in California). This thing really does it's job. No gimmicks. Polish a few times again with Bluemagic polish to leave protective layers (optional). Tried as my tennis wrist would allow, there was no getting rid of pitted spots. Everything else looks ok.

I do still like to replace those biding posts in the back with something more user-friendly and better looking. Any recommendation for sourcing? Not looking for any audiophile stuff that costs as much as the amp.

This was a fun project. More so than ST-35 mostly due to the fact that handwiring was involved. I was going back and forth between the original manual and DIYTUBE's. I got confused and paralleled pin 1-8 of EL34s and common grounded them through a 15.6 ohm resistor like the original. I did get 1.56 V. I rewired and it's back to 500 mV + biased to "PP perfection". Yellow_Light_Colorz_PDT_06

The amp sounds pretty darn good with those hodge-podge tubes that came with the amp. Speaking of which, is it so critical to have matching tubes if they can be biased individually through DIYTUBE board?

Here are some pics:

http://www2.snapfish.com/slideshow/AlbumID=162235906/PictureID=3274140767/a=86879691_86879691/t_=86879691

http://www2.snapfish.com/slideshow/AlbumID=162235907/PictureID=3274144396/a=86879691_86879691/t_=86879691

http://www2.snapfish.com/slideshow/AlbumID=162235908/PictureID=3274144431/a=86879691_86879691/t_=86879691

[mesherm]

Part of the problem in replacing the speaker terminals on the ST70 is that the slot in the chassis is narrow. It is not easy to find good sturdy 5-ways that will fit in the slot. What I do is replace the speaker terminals with a piece of fiberglass circuit board, phenolic board or even acrylic about 1/8 inch thick. Then I drill holes 3/4 inch apart and install banana jacks since all my speakers have double banana plugs on them. I like the flush fit of banana jacks since there is less chance of accidentaly breaking binding posts off.
It is not critical to have matched pairs and quads when you can individually adjust each tube's idle current.
Speaking of tube bias, you have installed separate cathode resistors for each EL34 right? Its common to replace those 15.6 ohm resistors and install 10 ohm 1% resistors on each EL34 cathode.

[EWBrown]

I found that the dual "banana" 5 way binding posts will fit the slots very nicely, just center them in the slot. Yes, there is some vacant "air" at each side of the bananas, but that's of no real consequence (for me). The best ones for this are the somewhat beefier ones from AES, and not those whimpy little ones from the RatShark.

This also works for ST35, with the original chassis.

Maybe not the most elegant of solutions, but it works for me Yellow_Light_Colorz_PDT_02 Yellow_Light_Colorz_PDT_06

/ed B in NH

[TomMcNally]

I like these things ...

http://www.diytube.com/phpBB2/viewtopic.php?t=1193&highlight=gold+terminals

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That's tight! Where could I get my hands on those, Tom!? -Min

[TomMcNally]

The guy sells on eBay:

http://cgi.ebay.com/Speaker-fork-Adapter-for-Marantz-8B-Marantz-9-marantz-2_W0QQitemZ190117872563QQihZ009QQcategoryZ32838QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[kheper]

Handmade Electronics sells them as well.

https://www.hndme.com/productcart/pc/vi ... oduct=1456