# Partial Schematic Arc/Pine 5W Amp w. Tremolo



## ruddy_canuck (Feb 7, 2015)

I've had an old Arc 5W 2x12 combo for years, swiped it from my brother when he joined the army in the 80s.
It's given me my share of problems and the occasional shock (2 prong plug).
Someone did a custom paint job on the chassis so I have no idea what the model number is... 

I ripped the "head" out years ago, put new speakers in the cabinet and used it as, well a cabinet.

I finally sat down to repair the "head" and put a chassis ground and 3 prong plug on it. I traced out the schematic but some of the caps are mystery caps and the pots markings aren't the easiest to read, and one has been replaced with what I can only hope is the correct value pot.

The spot where the tremolo pot is grounded is obviously a poorly done repair but it seems to be correct, the circuit works.

So, since I have never seen a schematic for my amp I am posting an incomplete schematic of my specific amp here - this is my own personal effort and might not me 100% accurate.

It is a 6AV6, 6AV6, 12AX7, 6V6, 5Y3 amp. They used 2 6AV6's but only 1/2 the 12AX7... weird... maybe I'll add a high gain channel.

<See post farther below for the corrected Schematic>


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## ruddy_canuck (Feb 7, 2015)

I always liked how this amp sounded, a kind of vintage love child of a Fender, a Marshall and a barrel of scotch. I replaced the old decrepit 6v6 & 12AX7, tried a few different dual triodes (from vintage to new and 12AY7 up to 12AX7) and a new 5751 and really brought it alive. I'm going to have to ditch that 2 6AV6 design at some point, rewire it to run a single more "normal" 12AX7 family tube instead.


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## jb welder (Sep 14, 2010)

No control over amount of trem?
You have half a 12AX7 unused? Suggest using it for the input triode, and leave the trem as 6AV6. No audio through the trem tube anyway, and if you made it 12AX7 you wouldn't want to combine it with an audio stage as you might get crosstalk between the 2 halves of the tube.
That will leave you with a socket spot for whatever you want to add.


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## Church-Audio (Sep 27, 2014)

ruddy_canuck said:


> I always liked how this amp sounded, a kind of vintage love child of a Fender, a Marshall and a barrel of scotch. I replaced the old decrepit 6v6 & 12AX7, tried a few different dual triodes (from vintage to new and 12AY7 up to 12AX7) and a new 5751 and really brought it alive. I'm going to have to ditch that 2 6AV6 design at some point, rewire it to run a single more "normal" 12AX7 family tube instead.


I would also get the heater off ground and create a virtual center tap on the heater with 100ohm 1 watt resistors.


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## ruddy_canuck (Feb 7, 2015)

jb welder said:


> No control over amount of trem?
> You have half a 12AX7 unused? Suggest using it for the input triode, and leave the trem as 6AV6. No audio through the trem tube anyway, and if you made it 12AX7 you wouldn't want to combine it with an audio stage as you might get crosstalk between the 2 halves of the tube.
> That will leave you with a socket spot for whatever you want to add.


Nope, no depth. I thought about adding it but honestly I don't use enough tremolo to warrant it. Plus I have a great custom tremolo pedal and a Fender Super Reverb with fantastic vintage opto tremolo/vibrato.

I found it very weird that they used the 6AV6 as the input triode then used only half of the 12AX7. I suspect they had a "standard" version that they then modified it for tremolo, reverb etc... There are two more empty mounting holes in the chassis, one is sized for a 9 pin socket, the other is the smaller 7 pin single triode socket size as well as some hidden control holes. I know they made the same amp with and without reverb, I could try and find their specific design or slide in a vintage Fender setup... hmmm... if I add a 12AT7 to drive a reverb tank I wonder if I can get away with 1/2 12ax7 (or a single 6AV6) for gain recovery. 



Church-Audio said:


> I would also get the heater off ground and create a virtual center tap on the heater with 100ohm 1 watt resistors.


Dang! I didn't notice that when I traced that out, but I was focused more on the audio path, so I'm going to double check it's sitting on ground like that, if it is, I'm going to fix it right away. Could be the source of the hum bug I've been trying to kill.


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## ruddy_canuck (Feb 7, 2015)

ruddy_canuck said:


> There are two more empty mounting holes in the chassis, one is sized for a 9 pin socket, the other is the smaller 7 pin single triode socket size as well as some hidden control holes.


My mistake, there is only one smaller hole that I could probably put another 9 pin socket into. They other hole is huge - probably for a smoothing cap (mine has a single 40u-40u dual cap) or possibly but not likely a power tube.



ruddy_canuck said:


> Dang! I didn't notice that when I traced that out, but I was focused more on the audio path, so I'm going to double check it's sitting on ground like that, if it is, I'm going to fix it right away. Could be the source of the hum bug I've been trying to kill.


YES - this is the case - I am going to change it over later today. Die hum bug, die!

I think it is a model 209. Will try and remove the "after market" paint from the control panel to see what's underneath...


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## ruddy_canuck (Feb 7, 2015)

Thank you eagle eye Chris Church.

I'm out of large 100 watt resistors, not even any 1/2 watt. (Wondering where this useless pack of 1/4 watt 100s came from... darn you digikey!)

So I put a pair of 1/2 watt 220s in instead, ran all new wiring to the heaters, adjusted some of the routing of the signal wires and the Hum Bug is dead!
I'm getting a little bit of hiss, but that's probably from the NOS 6AV6 that I have in there. I had already ordered a few more of these odd little tubes so I can swap them around, still haven't decided what to do with that unused 1/2 of the 12AX7.


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## Church-Audio (Sep 27, 2014)

If your in Hamilton go to nutech electronics on park dale they have tons of resistors in stock including 100 ohm 1% 1 watt that I use all the time. Good place to gor for some small caps and resistors. And it's good to support local businesses.


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## fraser (Feb 24, 2007)

Church-Audio said:


> If your in Hamilton go to nutech electronics on park dale they have tons of resistors in stock including 100 ohm 1% 1 watt that I use all the time. Good place to gor for some small caps and resistors. And it's good to support local businesses.


+1
its great having a place like that nearby.
if they dont have what youre looking for, let them know and theyll stock it.


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## ruddy_canuck (Feb 7, 2015)

fraser said:


> +1
> its great having a place like that nearby.
> if they dont have what youre looking for, let them know and theyll stock it.


Thanks guys, I often drive out to Sayal in Burlington but I'm not a huge fan of that place which is why I've been ordering in. Will give Nutech a try.

Found a mistake on my schematic where the Pre-Amp section and Tremolo section go into the power tube.
This one is correct.


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## fraser (Feb 24, 2007)

> Thanks guys, I often drive out to Sayal in Burlington but I'm not a huge fan of that place which is why I've been ordering in. Will give Nutech a try.


its not a huge place, and you wont find tubes or tube related things there-
but resistors, caps, switches, jacks, pots etc they have.
a little pricier than buying online, but in a pinch they are great.
i live only a few blocks away so its pretty handy.


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## TeleToons (Aug 13, 2014)

+1 on Nutech
Like Frazer said, wee bit pricey but good folks. Returned a wonky DMM there with no problem. Have bought off shelf and had them order stuff too.


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## Church-Audio (Sep 27, 2014)

Make sure you check that 170 ohm cathode resistor and replace that cap as well remember when replacing a cathode bias filter cap keep some distance between the two or the cap will eventually dry out from the heat. Check out ted webers bias calculator page for the chathode bias calculator it's a great way to get the amp dialled in just right.


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