Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Voxbox on February 09, 2011, 04:55:44 pm

Title: AC30 Layout
Post by: Voxbox on February 09, 2011, 04:55:44 pm: Hiya,

Anyone got a component layout for an early sixties AC30? (1963 AC30/6 with separate retro-fitted top boost on the back panel)

Its a bit of challenge even tracing the wiring!
Must have been even harder to build.
Thanks

Cheers
Title: Re: AC30 Layout
Post by: FYL on February 09, 2011, 05:36:47 pm: AFAICT only schemos are available...
Title: Re: AC30 Layout
Post by: Katie 77 on February 10, 2011, 01:10:24 am: http://www.thevoxac30guide.com/
Title: Re: AC30 Layout
Post by: Voxbox on February 10, 2011, 02:42:57 am: Thanks Katie!
Title: Re: AC30 Layout
Post by: archaos on February 10, 2011, 05:53:18 pm: Quote from: Voxbox on February 09, 2011, 04:55:44 pm
Hiya,

Anyone got a component layout for an early sixties AC30? (1963 AC30/6 with separate retro-fitted top boost on the back panel)

Its a bit of challenge even tracing the wiring!
Must have been even harder to build.
Thanks

Cheers

Unfortunately, the "Service Engineer's Guide to the VOX AC30 Valve Amplifier" doesn't have any component layout for the AC30 with retro-fitted TB on the back panel ; it only haves one component layout for the AC30/6 with integral TB on the control panel (p.23).
Title: Re: AC30 Layout
Post by: bakerlite on February 11, 2011, 06:12:03 pm: I just fixed one of these
The "L"Plate top boost mod is documented in that book - with a page dedicated to it and where to insert into the circuit
You have to cross reference that with the circuit applicable to your amp before it was modded

After all, at that time they came from the factory - unmodded - and the L plate was an after thought

I cannot imagine there is an authentic component layout for the amp with L plate mod as they never designed one - if i'm making any sense!

basicaly you have to view the original ac30/6 schemo and layout and refer to the L plate mod schemo too - there is no layout drawn for the mod but in fairness there are only about 8 components in it so you should be good to go

fwiw the components in the L plate top boost mod are subjected to some degree of heat over time as it is crammed in there - i had disintegrasted capacitors and a few drifted resistors in there - also look out for the black small cyclindrical "hunts" capacitors in the main boards - all of mine were pretty destroyed and apparently t'internet seems to say that they are notorious for going.
Title: Re: AC30 Layout
Post by: kagliostro on February 12, 2011, 12:11:11 pm: This isn't the original layout

but who is interested can use as to have the Top Boost version of the Vox AC30

https://taweber.powweb.com/store/6v30_schem.jpg

https://taweber.powweb.com/store/6v30_layout.jpg

Sometime ago I verified the schematic with the original Vox and is pretty close

Kagliostro
Title: Re: AC30 Layout
Post by: Voxbox on February 22, 2011, 05:20:12 pm: Yep bakerlite, I can verify that all the Hunts are pretty much done as they are either leaking DC or cracked open. Putting 150V caps in a 166V circuit aint smart :shocked: and it's a 48 year old amp....

FYI the latest version of the book does have the non-TB layout as I just bought it. Dont really need the TB Boost layout as you say. Again it's a rat's-nest of a layout but at least you can see how everything is connected, but I'm not looking forward to replacing the cathode cap as it seems that was the first component soldered in there and everything else was put in around it or on top of it! :sad:
Title: Re: AC30 Layout
Post by: bakerlite on February 22, 2011, 05:42:16 pm: hehe
when i first looked inside the ac30 i thought

"how on earth can one make such a mess and still sound so great"

what are you going to replace your hunts with?

enjoy!
Title: Re: AC30 Layout
Post by: Voxbox on February 24, 2011, 03:43:15 am: I've replaced the two Hunts in the TB circuit with Mallory 150 series, 400V jobs so they should last.....
I've yet to look around for a replacement for the 500pF one thats used for an anode cap in the bright pre-amp.

Silver micas?
Title: Re: AC30 Layout / 500pf
Post by: overtone on February 24, 2011, 05:44:10 am: I really like to use the old domino block micas for that one. Look for Lemco, El Menco etc, but watch out for the voltage ratings, many are too low.
To me the modern silver micas sound too edgy. It depends what you want to use the amp for. The modern silver micas will probably help you cut through the band mix some more, if you get my drift.

best,
tony
Title: Re: AC30 Layout / 500pf
Post by: archaos on February 24, 2011, 07:31:42 am: Quote from: overtone on February 24, 2011, 05:44:10 am
I really like to use the old domino block micas for that one. Look for Lemco, El Menco etc, but watch out for the voltage ratings, many are too low.
To me the modern silver micas sound too edgy. It depends what you want to use the amp for. The modern silver micas will probably help you cut through the band mix some more, if you get my drift.

best,
tony

+ 1 !

I have installed El Mencos from Alessandro, http://www.alessandro-products.com/main.php?p=parts (http://www.alessandro-products.com/main.php?p=parts) & they are excellent.