Pine amplifier Model 209

[dmeek]

I have this old Canadian-made amp for which I traced the schematic just because I like tracing schematics.
What I found is the strangest tube circuit I've ever seen.
Can anyone explain what V1 is doing?

I haven't powered the amp up yet, it needs filter caps.
Customer says it makes a big hum.

https://music-electronics-forum.com/...1&d=1556227955

[The Dude]

Are you sure it's drawn right? Or, maybe someone miswired it? Or, maybe the wrong tube is in the socket? I can't see how it would do anything the way it's drawn. Aside from other issues, the plate and cathode are connected together.

[dmeek]

The wiring looks original see the last photo, V1 is on the left, V2 on the right.
Could be a wrong tube type but they all look original. This amp hasn't been messed with much if at all.

For the record here are some photos


https://music-electronics-forum.com/...1&d=1556155610

https://music-electronics-forum.com/...1&d=1556155610

https://music-electronics-forum.com/...1&d=1556155610

https://music-electronics-forum.com/...1&d=1556155823

[dmeek]

I've come to the conclusion that this is a "do-nothing" circuit. With the diode of V2 it is a string of
two back-to-back diodes and the 6.8M resistor, both ends being grounded.

Why?

A) They wanted to increase the tube count for marketing purposes.
B) The chassis was meant for a different model and they had to use the extra tube socket.
C) An inside joke at the factory.

Or it could be:

D) Interstellar Mojo Wave Condenser and Input Stage Direct Injector for increased mojosity (pat pending).

[Enzo]

A) They wanted to increase the tube count for marketing purposes.

Nah, no one would bother doing this. No one would look at a super simple amp like this and worry about tube counts.

B) The chassis was meant for a different model and they had to use the extra tube socket.

Nah, if ther was already a spare socket, they would just leave it unwired.


If I had to guess, I might look at hum abatement. Try disconnecting the resistor and see if hum increases. Or for that matter, just pull the end tube and see if hum increases.

[The Dude]

Don't think for a moment I understand what the intention was, but I was thinking a similar thing (hum abatement). Except, I was thinking RF or high frequency abatement via the tube and that .03 cap. Still, just a SWAG on my part.

[Enzo]

My notion, and it is no more than that, was that the extra tube resistor and cap might inject just enough hum to counter some existing hum at opposite phase.


Yes, it seems to me there would be simpler means.

[g1]

Not sure if you guys are talking about the same thing, but the only thing that stuck out to me was that it connects to one of the diodes of the working tube.

[dmeek]

I'm not familiar with the 6AV6 but it seems to me that with the cathode grounded a signal on the pin 5 anode would not affect the triode.
Also to support my point about the tube count here is a scan from an old Eaton's catalog (Eaton's was a Canadian department store like Sears)


https://music-electronics-forum.com/...1&d=1556311400



Eaton's sold Symphonic and Vagabond brands. Who sold Pine and Lifco?

[Bloomfield]

The 6AV6 is a single triode with very similar specs to the 12 AX7, so you can refer to those datasheets for most specs.

[g1]

Eaton's sold Symphonic and Vagabond brands. Who sold Pine and Lifco?

I realize you're probably asking about retailers, but you might be interested in this info about some of the Canadian amp manufacturers and their CSA numbers.
http://web.ncf.ca/ac151/

[dmeek]

I sent him some Keil info a few years ago. He seems to be mainly interested in Lifco. Lifco and Pine were both from Montreal but not connected as far as I know.

[Mark Hammer]

My first rig, purchased 2nd hand in 1967 or so from a guy in Montreal (my friend's big brother), was a 4-pickup Kent Videocaster and a Symphonic amp with volume, tone, tremolo and a 12" speaker. He probably bought it from Eaton's himself, but later replaced it with a wonderrful brown tolex Deluxe Reverb and a baby blue Watkins Rapier. The Symphonic was likely the "six tube" one in the scanned catalogue page, though I don't remember dual volume controls, just the 4 input jacks. No recollection of what the tube complement might have been, though I suspect it would have been a dual 6BQ5 output pair. It wasn't necessarily loud enough to compete with my bandmate's Vox Buckingham, but I would goose it with an unusual booster pedal. I'd plug my guitar into the mic preamp of my Roberts tape recorder (also tube-based) and feed the line out to the guitar amplifier. It was the very definition of "wooly".

[Alley_Cat_Jack]

You ever get this thing figured out? Just picked up one myself yesterday that needs repair.

[vintagekiki]

https://www.guitarscanada.com/threads/partial-schematic-arc-pine-5w-amp-w-tremolo.69033/#lg=thread-69033&slide=0

https://www.guitarscanada.com/threads/partial-schematic-arc-pine-5w-amp-w-tremolo.69033/