Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: americanflyer302 on November 03, 2011, 09:33:08 am

Title: Kay 703 Clone or Change?
Post by: americanflyer302 on November 03, 2011, 09:33:08 am: Hi everyone. It has been a LONG time since I was here and am glad to be back.

I came across a Kay 703 cabinet and speaker for 15 bucks at a pawn shop and picked it up for a project. The cabinet is in nice condition and the speaker does not seem original. The sheet metal chassis is missing but I could fabricate another...which is where my question comes in. Should I clone and rebuild the original 703 circuitry or turn it into a frankenamp Kay 703 with a 59 champ circuit inside or something else?

If I go the original Kay design, does anyone know the correct speaker for the Kay or know where I can get one?

Thanks for your suggestions and ideas.

Chris.
Title: Re: Kay 703 Clone or Change?
Post by: chuggy on November 03, 2011, 12:08:14 pm: Your re-creation will have player but not vintage or collector value. The Kay has substantially less volume than a tweed Champ. Which sound do you want? The Kay has no power transformer but needs an isolation transformer (which costs less) for safety. The Kay has an alnico speaker and speaker mounted tiny output transformer. There are at least two versions of the Kay 703 that use entirely different tubes. I have a Kay 703 and can send you pics if desired.

Jim R
Title: Re: Kay 703 Clone or Change?
Post by: americanflyer302 on November 03, 2011, 12:46:07 pm: Jim,
Thanks so much for the post. OK, I am going to keep the Kay original and would love some good pictures of the chassis wiring etc.. Even some dimensions of the chassis sheet metal would be great. I really appreciate it and will update and post pics on this thread as I progress.

Chris.

Pics would be best emailed to: chris_s@efn.org
Title: Re: Kay 703 Clone or Change?
Post by: americanflyer302 on November 03, 2011, 10:18:39 pm: Jim,
Is it possible to get some good pics of the layout and wiring so I can wire and route it like original.
Thanks,
chris
Title: Re: Kay 703 Clone or Change?
Post by: americanflyer302 on November 06, 2011, 11:50:30 am: Jim,
You still around! :w2:
Title: Re: Kay 703 Clone or Change?
Post by: chuggy on November 06, 2011, 09:42:42 pm: Pics here-

https://picasaweb.google.com/jimjimdr/Kay703

Big tranny hanging down is an added isolation tranny.

Jim R
Title: Re: Kay 703 Clone or Change?
Post by: jojokeo on November 07, 2011, 02:35:33 am: Here's the 703-C version w/ diff tubes that I did several years ago if this helps any? People make a big deal out of the tranny situation but tens of thousands were used back in the day and I've never heard on the news, "guitar player dead from playing his amp...film at 11..." - Caution!: play at your own risk. :l2:

* if you feel the need to add safety btwn yourself with whatever amp that you may ever play there's something that you can do w/ your guitar's ground: add a 220k/1/8watt resistor paralleled w/ a small ceramic .001uF/1kV cap btwn the ground. This will help keep you from making the 11 o'clock news.
Title: Re: Kay 703 Clone or Change?
Post by: sluckey on November 07, 2011, 07:16:16 am: The 703 (not the 703C) uses more common tubes and has a PT that provides isolation between chassis/strings and the power line. It's safe just as it is. The series filament string is powered directly from the line but has no connection to chassis.
Title: Re: Kay 703 Clone or Change?
Post by: americanflyer302 on November 07, 2011, 10:01:18 am: Thanks for all the replies guys! I had to hit ctrl+C to get the page to refresh properly and display all of the responses. :w2:

Anyway, thanks for the pictures too. I really like the idea of using the early version with more common tubes...I already have plenty of the common tubes but none of the odd tubes in the 703-c. Jim, what tube lineup is in your 703? It looks like octal tubes used? I thought these kay amps used all mini tubes like the 35w4, 12au6,50c5 etc..

Thanks again for the great pics guys.

Chris.
Title: Re: Kay 703 Clone or Change?
Post by: sluckey on November 07, 2011, 10:42:50 am: 703 uses 12AU6 (7-pin mini), 50L6 (octal), and 35Z5 (octal). I meant to post this schematic earlier...

http://www.el34world.com/charts/Schematics/files/kay/kay703.pdf (http://www.el34world.com/charts/Schematics/files/kay/kay703.pdf)
Title: Re: Kay 703 Clone or Change?
Post by: Cups on November 07, 2011, 12:37:41 pm: Where would I find an isolation transformer? I have a Lark amp without a power tranny. I did some searches on ebay and the transformers posted didn't look right.
Title: Re: Kay 703 Clone or Change?
Post by: sluckey on November 07, 2011, 12:50:25 pm: AES has them...

http://www.tubesandmore.com/scripts/foxweb.dll/catalog@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?PAGE=SUBCAT&SEARCH_TREE01=TRANSFORMERS&SEARCH_TREE02=05_HAMMOND&SEARCH_TREE03=07_LINE (http://www.tubesandmore.com/scripts/foxweb.dll/catalog@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?PAGE=SUBCAT&SEARCH_TREE01=TRANSFORMERS&SEARCH_TREE02=05_HAMMOND&SEARCH_TREE03=07_LINE)
Title: Re: Kay 703 Clone or Change?
Post by: jojokeo on November 07, 2011, 01:46:46 pm: you can get the iso trannies for $12 at Mouser. I believe this will work fine - http://www.mouser.com/ProductDetail/Triad-Magnetics/N-51X/?qs=sGAEpiMZZMvwUzoUXIIvycT6np3HRZBQgJXqMV3aswI%3d (http://www.mouser.com/ProductDetail/Triad-Magnetics/N-51X/?qs=sGAEpiMZZMvwUzoUXIIvycT6np3HRZBQgJXqMV3aswI%3d)