Bare Knuckle Pickups Forum

Forum Ringside => Tech => Topic started by: sgmypod on May 09, 2012, 11:07:45 PM

Title: want to change amp from 6v6 to el84, having to simplify
Post by: sgmypod on May 09, 2012, 11:07:45 PM

aimed at amp blokes, would like valve, bases etc everything to do, is it possible obviously will have 6v6  or el84 in but have the two valve bases permanently connected. have provided schematic and drawing

Title: Re: want to change amp from 6v6 to el84(leaving orig valve base in so can swap back)
Post by: jpfamps on May 09, 2012, 11:20:02 PM

We built a single ended amp with switchable EL84/ 6V6.

I think we used a DPDT switch to simultaneously lift the cathode on the unused valve and switch the filament supply off. This was with both valves connected to the OT.

By doing this we avoided having the unused valve on and wearing out, and avoided any switching of high voltages.

I could probably generate a schematic.

Title: Re: want to change amp from 6v6 to el84(leaving orig valve base in so can swap back)
Post by: sgmypod on May 10, 2012, 07:37:26 PM

cool how much schematic and parts

Title: Re: want to change amp from 6v6 to el84(leaving orig valve base in so can swap back)
Post by: jpfamps on May 11, 2012, 05:19:25 PM

I've composed a schematic and will try to remember to bring it into the workshop where I have internet access.

Title: Re: want to change amp from 6v6 to el84(leaving orig valve base in so can swap back)
Post by: HTH AMPS on May 11, 2012, 06:43:50 PM

It'd be cheaper to buy an Epi Valve Junior, strip out the guts and wire it PTP.

The Harley Benton ones are the same, but slightly cheaper.

Title: Re: want to change amp from 6v6 to el84(leaving orig valve base in so can swap back)
Post by: sgmypod on May 11, 2012, 07:57:43 PM

Would have thought that would be more, would'nt I need to buy new trannies for them

Title: Re: want to change amp from 6v6 to el84(leaving orig valve base in so can swap back)
Post by: jpfamps on May 12, 2012, 11:49:12 AM

Here's the schematic.

The resistors marked in blue probably aren't needed, and I wouldn't include them.

I've not included the screen grid circuit and guestimated the cathode resistor values etc.

Title: Re: want to change amp from 6v6 to el84(leaving orig valve base in so can swap back)
Post by: sgmypod on May 13, 2012, 12:12:48 AM

Thanks frank, could you supply bits

Title: Re: want to change amp from 6v6 to el84(leaving orig valve base in so can swap back)
Post by: sgmypod on June 03, 2012, 11:53:40 AM

frank i have run out of, space and skill. so am going to just swap out 6v6 for the el84 (obviously swapping pins)
so with bits you sent  need swapping on the original schematic 
6v6 C9 22uf 25v  (el84 100uf)
6v6 R9 470R 2w  (el84 150ohm)
6v6 R8 10k           (el84 1k)
6v6 R10 470r       (el84 10k)

am i correct or miles out (as say will connect pins correctly on top of this)

Title: Re: want to change amp from 6v6 to el84, having to simplify
Post by: sgmypod on June 06, 2012, 12:14:04 PM

Was slightly out, thanks frank