Selecting my next 18w mod project

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yello
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Selecting my next 18w mod project

Post by yello »

I am pondering another 18w build, this time modding a vintage amp rather than a scratch build.

I have several amps on hand that are good prospects: a Filmosound projector amp, a Hammond organ amp, and the one I think I might choose this time which is an old phonograph amp:

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Tube layout is the same as my recent 18w build (EF86 Lite 2P) - ef86, 12ax7, el84 x2, ez81. It appears to me to be a Mullard 5-10 style amp circuit, and has Schumacher PT/OT.

Here is a schematic I found for it:

Image

Updated, here is the official schematic that came with it:

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Last edited by yello on Thu 06/23/22 9:55 am, edited 1 time in total.
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Re: Selecting my next 18w mod project

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Which is that? Not the stereo with one OT.

I have several old organ amps I acquired for iron and tubes. And one of these days I'm gonna use them. 3 were for EL84, 2 were for 6L6...

I've even bought aluminum chassis for the day when I finally get around to it, CE Distribution blank chassis, pretty affordable but you have to drill all the holes.....
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Re: Selecting my next 18w mod project

Post by Bieworm »

Unit_1 wrote:
Wed 06/22/22 7:55 pm
Which is that? Not the stereo with one OT.

I have several old organ amps I acquired for iron and tubes. And one of these days I'm gonna use them. 3 were for EL84, 2 were for 6L6...

I've even bought aluminum chassis for the day when I finally get around to it, CE Distribution blank chassis, pretty affordable but you have to drill all the holes.....
I always use chassis blanks. I buy them for 18€...well 24€ nowadays. Damn Ukrain situation!!!
https://www.tube-town.net/ttstore/tt-ch ... -x-65.html
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yello
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Re: Selecting my next 18w mod project

Post by yello »

Unit_1 wrote:
Wed 06/22/22 7:55 pm
Which is that? Not the stereo with one OT.

I have several old organ amps I acquired for iron and tubes. And one of these days I'm gonna use them. 3 were for EL84, 2 were for 6L6...

I've even bought aluminum chassis for the day when I finally get around to it, CE Distribution blank chassis, pretty affordable but you have to drill all the holes.....
Yeah, a phonograph type amp but mono. I have a blank chassis laying around, but its a little small, and this one already has the right layout, just need to remove/change parts to the circuit I want. Should be a fun challenge

I found the schematic that came with it, better than the handwritten one as it has more info:

Image
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Re: Selecting my next 18w mod project

Post by yello »

And here are some shots inside it:

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Image

Image

Image

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Re: Selecting my next 18w mod project

Post by zaphod_phil »

What a rat's nest! :o
good luck for straightening it out :)
Those old transformers are really valuable, as well as some of the old signal caps Just remove the hissy carbon-composition resistors.
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yello
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Re: Selecting my next 18w mod project

Post by yello »

Finally got around to doing a little work on this project amp. Took it on vacation with me:

Image

Removed the cap cans, took out the V/T controls, deleted extra ins/outs. Just left transformers, sockets, plus bulk of circuit for now. Will likely swap sides, putting controls and input on "back" and power, fuse, etc. on "front."

Next I will ponder what circuit to put inside. Maybe the same ef86 18w as my previous build, maybe something else...
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Re: Selecting my next 18w mod project

Post by JMPGuitars »

You might want to try the Lite 2b(ish) if you haven't done that one. Very similar to your EF86 Lite2P, but with a 12AX7 preamp instead.
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yello
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Re: Selecting my next 18w mod project

Post by yello »

JMPGuitars wrote:
Thu 09/01/22 4:20 pm
You might want to try the Lite 2b(ish) if you haven't done that one. Very similar to your EF86 Lite2P, but with a 12AX7 preamp instead.
You read my mind, that is what I have been considering!
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