Mk IV rebuild question

New here and just getting started on some working Mk IV's after completing a new build (from an unbuilt 1976 PAS3 kit) PAS3 with the ZMods and upgrade supplies. I can only find new design Mk IV boards on Curcio's site. Are there any others?? Also - dumb question - what do you all use to polish old Dynaco chassis???

Hi --- Roy at the Tubes4HiFi website used to have VTA Mk4 Boards available, but I don't see them listed now. You might send a message to Roy at info@tubes4hifi.com and see what he says.
Stew

Thanks stewdan. I know that Mk IV's are very similar to half of a ST-70, and I could probably make my own boards from Bob's designs for them, but Curcio's kits and capacitor replacement boards are reasonable and are drop in.

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Peter, thanks for the reply. I had already checked dynakitparts and triode. Dynakitparts only has the stock boards for the IV. Triode only shows their boards for the Mk II and III. Not sure the B+ voltages are the same between the III and IV - I know they are between the ST-70 and the IV. I missed the Parks Audio site - very interesting, but is more for the person that likes to take it from scratch a bit more than I wanted. I'll probably go with Joe Curcio's dual triode drop in board kits and cap replacement kits. I want to keep the GZ34 rectifier. I'll post some pics after everything is done.

As far as polish, I found a general metal polish at a home show that works well. I've used Flitz before and it is a bit agressive. Chrome polish for autos also works well, but has more petroleum in them - so more conductive/flammable.

Mike

Mike,
Shannon Park's MK IV upgrade board is very good...He provides a BOM for all the parts and a manual for installation and setup. Great online support through his DIYtube forum.

Don't expect much support from Curcio....

Kevin @ Dynakit

I agree with Kevin, don't use the Curcio boards, they are poorly made and poor support.
I usually send my customers to Shannon Parks site for MK4 boards, unless they want to use my MK3 boards,
but I have traces where the mounting holes would need to be which would need to be cut, isolated, and jumpered.
I sold them for a couple years, but selling 1 or 2 pair a year wasn't worth the trouble.
Here's the link for Shannon's boards . . . . http://www.diytube.com/phpBB2/viewtopic.php?f=11&t=923

I hate to disparage Curcio's MkIV boards as I used them on mine. The PCB quality isn't the greatest out there. Also, If you go with the driver upgrade board AND the cap upgrade board you will have lots of fun integrating the two as Curcio completely failed to consider this in his documentation. Both upgrades assume the amp is stock. I found myself scratching my head a lot during the builds.

The upside is that Curcio's circuit does sound very good.

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Thanks to all for the replies and advice. Especially to corndog for the excellent photos - if mine are that "photogenic" when done, I'll put some pics up.

It looks like I may have made a less than optimum decision - I went with Curcio's stuff, although I could probably still cancel the order. I did have several back and forth emails with Joe about modifying non-stock Mk IV's, and he was prompt to answer. I eventually decided to put my Mk IV's back to stock and check their performance. After 15 years of being idle, they started up, biased ok, and played fairly well.

I hope this all works out, when I ask for advice, I should probably take it https://2img.net/i/fa/i/smiles/icon_pale.gif . If I'm not happy with the quality of the boards or parts from Curcio, I could send them back and just use the capacitor upgrade with Shannon's input boards.

I'll post my experiences once the project is complete.

Mike

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My .02....

I've used both the Curcio and tubes4hifi stuff over the years. Both vendors have been great to answer questions when needed. As for integration of different kits, not a totally unknown situation. My ST70 had the Curcio cap board mod, and then I went for the VTA drive board this year. After conferring with both Joe and Roy, both gave me the same answer of what to change where (there was a resistor change required). It's the nature of the beast, multiple mods have to be thought thru.