part substitution on the diytube st70 board

knowledge base for the classic Dynaco ST70

part substitution on the diytube st70 board

Postby guitarpsych » Sat Apr 21, 2007 8:29 am

mouser.com doesn't have this part

part#
2 C3,C4 220pF 5982-15-500V220 $0.78

Is there another part that would work just as well?
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Postby TomMcNally » Sat Apr 21, 2007 9:15 am

Handmade Electronics has them ... his minimum order is $ 14 or something,
so you'll need to grab a few other things.

https://www.hndme.com/productcart/pc/viewCategories.asp?idCategory=25

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Postby guitarpsych » Sat Apr 21, 2007 9:21 am

That is definitely the problem! Having to order from multiple sources. That's why I'm hoping there might be another slightly different value that would work well here that I could order along with everything else at mouser.com.

But thanks for the link. Maybe I'll switch the entire order to that location.
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Postby mesherm » Sat Apr 21, 2007 11:23 am

I have 6 of them in my parts drawer. Email me your address and I will tape a pairof them on a piece of pasteboard and slip them in an envelope to you no charge.
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Postby erichayes » Sat Apr 21, 2007 1:40 pm

Hi All,

Try 5982-10-500V220. A little more expensive ($1.40) but in stock.
Eric in the Jefferson State
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Postby Slartibartfast » Sun Apr 22, 2007 11:24 am

Just curious here,

Does Antique Electronic Supply not have all the parts needed? What is the attraction to Mouser?

Thanks,

Robert
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Postby TomMcNally » Sun Apr 22, 2007 1:29 pm

Robert ...

Mouser is the way to go when building a DIYTube amp ... Shannon supplies what they refer to as a BOM (Bill of Materials) and all you
have to do is cut and paste it on their website and the parts are on
the way. The smaller "boutique" vendors don't carry the precise
values needed, and don't have the vast array Mouser has.

When building an amp ... I use these vendors ... they are all good
for what they specialize in ... Mouser, Triode, Antique, Tubezone,
Angela, Handmade, Euphonia, and ApexJr

... tom
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Postby Uncle Ned » Thu May 03, 2007 11:59 pm

There's no DC voltage on this part, you can use the 50 volt 220 pf polystyrene that's listed in the Mouser catalog instead. I'm a bit partial to polystyrene myself (it's the next best thing to teflon or a vacuum), so that's what I supply with the kits I sell.
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Postby dhuebert » Tue May 29, 2007 8:10 am

Further to the subject of sustitution:

Can anyone suggest Hammond replacement transformers for the ST70? Hmmm, sounds like sacrilage, don't it? It's just that I'm thinking of scratch building and don't have an old ST70 to upgrade and Hammonds are easy to get here in Winnipeg.

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Postby Uncle Ned » Tue May 29, 2007 9:03 am

1650N is the logical choice for the output (same primary Z and similar size as A470), 156R for the choke. Hammond doesn't make a power transformer similar to the PA060 but you could use a 715 with choke input, or better still, make a couple of MkIV knockoffs instead with 273 or 274BX... a replacement power transformer for a Fender Super Reverb would work as well as the 273BX, and it's got a convenient bias tap...
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Postby dhuebert » Wed Aug 15, 2007 8:33 am

Hammond doesn't make a power transformer similar to the PA060


You're right, I would want 350V CT @ 250 mA to be comfortable.

Can you recommend a source for a PA060?

better still, make a couple of MkIV knockoffs instead with 273 or 274BX


I have Shannon's board for the ST-70 and want an amp like the ST-35 with more oomph for the garage. So 6L6s with ~ 425V b+ would do it I think. I already have a pair of eiclones for the house. (they could use more power as well)

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Original board update parts

Postby Clik2media » Thu Jan 22, 2009 11:55 pm

Any suggestions for a complete list of modern replacement parts for an original ST-70 board. much appreciated

Mike
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Re: Original board update parts

Postby Brinkman » Fri Jan 23, 2009 9:28 am

Clik2media wrote:Any suggestions for a complete list of modern replacement parts for an original ST-70 board. much appreciated

Mike


A pair of quality NOS 7199s
wirewound resistors for the plate load resistors
wirewound resistors for B+ stepdown resistors
carbon comp resistors for grid stopper resistors
all remaining resistors should be metal film type
all resistors should be hand-matched into pairs (corresponding to stereo channels)
Negative feedback caps could be silver mica
coupling caps could be film/foil or paper in oil type

BTW, the only thing above that's really "modern" are the metal film resistors. I am not a fan of the stock board because most of the energy spent doing the above will not be noticeable when the sound is that congested. IMO, a driver board upgrade frees up the "true" sound of an ST-70 which is the pleasant sound of the Dynaco output transformers.

Good luck!
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