Mk 3 question

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Mk 3 question

Postby TerrySmith » Tue Jun 28, 2005 4:06 pm

Does anyone know the size of a MK 3 driver board?

I am so pleased with the sound of this ST-70 board(s) on my MK-4's, I may build a pair of MK-3's with the modified boards!!
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Postby EWBrown » Thu Jun 30, 2005 5:59 am

I have an A.S.L. MKIII replacement board here, dimensions are 3 7/16W X 4 5/16 L, mounting holes are 3 1/8 X 3 3/8 inches.

HTH

I'm in process of building up a single MKIII clone (no original Dynaco parts whatsoever) for use in a guitar amp project. I decided later to go with iron and driver board, from Uncle Ned at Triode Electronics, and the cap board from "tubes4pro" , the A431 OPT just arrived yesterday.

The chassis is from E-bay, a seller there has new MKIII chassis in two different versions, one is a copy of the original, the other is set up for using a cap board, and 5 way binding posts for the speaker outputs. I chose the latter. Very niely made.

/ed B in NH
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Re: Mk 3 question

Postby Shannon Parks » Thu Jun 30, 2005 6:52 am

TerrySmith wrote:Does anyone know the size of a MK 3 driver board?

I am so pleased with the sound of this ST-70 board(s) on my MK-4's, I may build a pair of MK-3's with the modified boards!!


Hi Terry,

Some side-by-side pix:
www.diytube.com/forumpix/1.jpg
www.diytube.com/forumpix/2.jpg
www.diytube.com/forumpix/3.jpg
www.diytube.com/forumpix/4.jpg
www.diytube.com/forumpix/5.jpg
www.diytube.com/forumpix/6.jpg

I actually do have some MKIII prototype PCBs lying around, but they needed some cuts-n-jumpers (don't think I kept my documentation either) to rev up to the ST70 design. That is what Thermion has in his Mark IIIs and loves them.

Terry - if you do want to try this, I can cut the boards at work on our shearer and give you a discount price, too!

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Postby EWBrown » Thu Jun 30, 2005 10:36 am

Those boards are too nice to cut up Yellow_Light_Colorz_PDT_11 but it's a neat trick anyway...

The ASL board uses the original 6AN8 circuit, which I never really liked using a "plinker" like that. The ones I settled with are fromUncle Ned @ Triode, they use a 12AU7 as a almost-SRPP driver and 12AU7, or 6CG7, 6DJ8, 6N1P, etc as the phase splitter, the boards have jumpers to change the filament connections. Now I have everything to complete one MKIII. Yellow_Light_Colorz_PDT_08

/ed
Last edited by EWBrown on Thu Jun 30, 2005 12:32 pm, edited 2 times in total.
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Another Idea...

Postby Shannon Parks » Thu Jun 30, 2005 12:08 pm

I can also suggest using the Kara Chaffee circuit from the March 2001 audioXpress using the original pcb. It's the same modified Mullard concept.

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Postby EWBrown » Thu Jun 30, 2005 12:31 pm

Originally , I was going to use an OPT that I got indiredtly (via another e-bay seller) from the infamous and ill-fated HWT, it was essentially a 6600 ohm P-P version of the MKIII OPT, along with an HWT power trannie and the aforementioned ASL 6AN8 board.

The HWT power trannie had too much mechanical AC generated buzz, the OPT was developing a nasty rust problem, even though it had never been used or expose to "rust" generating condition, and I just wasn't too enthralled with the 6AN8.

Hit "reset" and start over... Yellow_Light_Colorz_PDT_19

If the new build one works out as nicely as I hope (and expect) then I'll go ahead and make a second one. Up to that point, it'll serve as a test bed. Maybe I'll even try the 2"/3 of an ST70 board" trick Yellow_Light_Colorz_PDT_10

/ed B in NH
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THANKS!

Postby TerrySmith » Thu Jun 30, 2005 4:30 pm

Thanks for the help Ed & Shannon! Ever since I saw the new MK-3 chassis on ebay last sunday, the gears in my head have not stopped turning. I will opt for the improved version with binding posts, etc. Now that I see shannons board can fit, it sealed the deal!

It's nice to know you can build a MK-3, ST-70, etc with all new parts!
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Postby EWBrown » Fri Jul 01, 2005 6:56 am

I went for the "new" style chassis as well. He also has un-punched MK3 and ST70 chassis listed.

That chassis was the final "push" I needed to get back on this project, at least the hard metalworking part is already done.

The buzzy and rusty HWT iron may eventually end up on a "test bed" chassis or breadboard, it should be OK for protoryping and repairing driver boards and haywired circuits.

/ed B in NH Yellow_Light_Colorz_PDT_05 Yellow_Light_Colorz_PDT_07 Yellow_Light_Colorz_PDT_06
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Postby ashok » Fri Jul 01, 2005 9:31 am

Is this the ST-70 chassis?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50593&item=5784071644

I did not see any pre-punched ST70 chassis from the seller.

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Postby EWBrown » Fri Jul 01, 2005 11:32 am

That's the one... I think he's had pre-punched ST70s previously, but they weren't cheap, around $140. He'll probably list them again sometime.


The ironic thing, is that these chassis alone cost more $$$ than did the entire kits when they were produced nearly 40 years ago.
But, then, 1965 Dollars went a lot further than do 2005 Dollarettes...

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Postby ashok » Fri Jul 01, 2005 1:36 pm

An email to the seller elicited the response that he will have pre-punched ST70 chassis in 2-3 weeks.

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Money Calc

Postby Shannon Parks » Fri Jul 01, 2005 2:04 pm

EWBrown wrote:But, then, 1965 Dollars went a lot further than do 2005 Dollarettes...


How much further you ask?

http://www.westegg.com/inflation/index.html

"What cost $100 in 1965 would cost $595.81 in 2005."

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Re: Money Calc

Postby Shannon Parks » Sat Jul 02, 2005 6:23 am

separks wrote:
EWBrown wrote:But, then, 1965 Dollars went a lot further than do 2005 Dollarettes...


How much further you ask?

http://www.westegg.com/inflation/index.html

"What cost $100 in 1965 would cost $595.81 in 2005."

Shannon


For fun, lets go back to 1960.

Gallon of Gas:
What cost $.31 in 1960 would cost $1.96 in 2005.

First Class Stamp:
What cost $.04 in 1960 would cost $0.25 in 2005.

Dozen Eggs:
What cost $.57 in 1960 would cost $3.61 in 2005.

Gallon of Milk:
What cost $.49 in 1960 would cost $3.11 in 2005.

RCA 21" color TV:
What cost $495 in 1960 would cost $3136.69 in 2005. Hmm - that plasma TV doesn't sound like such a bad deal after all. Yellow_Light_Colorz_PDT_03

Dynaco 70 Kit:
What cost $99.95 in 1960 would cost $633.36 in 2005.

Factory Built ST70:
What cost $129.95 in 1960 would cost $823.46 in 2005.

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Postby EWBrown » Tue Jul 05, 2005 5:53 am

Let's see.... In 1960, a decent car cost around $2000.

Candy bars were 5 cents, and a bottle of Coke was a dime.
Those Hostess fruit pies, twinkies, etc were a dime.
Comic books were a dime.

Baseball cards (usually 5) came with Topps Bubble Gum, for a nickel.
Yes, I used to collect them back in early 60s, and all of them were tossed out when we moved in 1964. Including Mickey Mantles, etc. Yellow_Light_Colorz_PDT_13

Depending on your location in the US, gasoline was around 25 cents
per gallon, and "price wars" often brought the price down even further.
Heating oil was around a dime per gallon.

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