6G3 PT

[dude]

Looking to build a 6G3 head, want to use a Hammond AO43 chassis, gutted using the original OT and PT. The OT would work fine for 6v6s but the PT @ 315-0-315 is a little high in voltage for the 6G3 which 290/300 would be better suited. If l use the AO-43 PT with about 30volts higher than the original 6G3, 375v B+, would l lose the 6G3’s crunch at higher volumes? Just looking for opinions. I would assume l could lower rail voltage to PI and preamp but the plates would be about 400v from experience with that PT on 6v6’s.

[HotBluePlates]

Looking to build a 6G3 head, want to use a Hammond AO43 chassis, gutted using the original OT and PT. The OT would work fine for 6v6s but the PT @ 315-0-315 is a little high in voltage for the 6G3 which 290/300 would be better suited. ... about 30volts higher than the original 6G3, 375v B+ ...

The schematic is lying to you.

There were 3 different power transformers used in the 6G3 Deluxe:  125P2A, 125P17A, 125P23B

I have a 1962 Deluxe with the 125P17A.  With 120v input it delivers 333-334v AC to the rectifier plates, and with the GZ34 puts 419v DC at the 1st filter cap, and 400-405v DC at the 6V6 plates (depending on OT winding resistance & current-draw).

My amp's PT is lower-voltage than the first-version amps using the 125P2A.  I know a guy who owns one of those & uses a 5Y3 rectifier rather than a GZ34 just to keep the voltage down a bit.  His amp puts 448v on the 6V6 plates with a GZ34 @ 121vac and 415v with a 5Y3.

I previously owned a 1963 Deluxe as well, with the 125P23B transformer (as well as a 1964 Deluxe Reverb that used the same part).  With that PT, there was just-under 400v DC on the 6V6 plates with a GZ34 and 120v AC input.


Don't worry, your PT will serve just fine in that amp!

[dude]

The schematic is lying to you.

Don't worry, your PT will serve just fine in that amp!

Ok, thank you, those Fender Brown Face Deluxe’s look mighty fine, l had one once but like a lot of us let it go back in the late 70’s, for too cheap. I really miss that amp, l’m jealous,  . 
I have another PT l could use, older Allen #TP40D, choice of 325-0-325 or 341-0-341, also has a 50v bias tap, a plus. And 3A @5v so could use a 5u4G, fits in the chassis too, 180mA, info on PT says 120vac,60hz 1.75 ohms. So, the listed voltages are 120ac wall, l assume.
Opinion again, use the #TP40, and if so what AC volttage…? I have 120 @ the wall, good old stock matching 6V6’s. What would you do..?

[HotBluePlates]

I have another PT l could use, older Allen #TP40D, choice of 325-0-325 or 341-0-341 ...
Opinion again, use the #TP40, and if so what AC volttage…?

The 325-0-325v secondary looks mighty-close to the "333v" my 6G3 delivers to the rectifier plates.  I would pick that one.

325v x 1.414 = ~460v so you might want 500v rated caps.  The 475v or 500v F&T caps Hoffman carries will both work (I think I have 475v F&T caps in my 6G3).

[dude]

Thanks for the advice, l’ll use the TD40, 325ac. Also have an Allen TO30D OT, Deluxe upgraded OT, 30 watts, 7k ohms w/8 and 16 sec’s, 6v6’s @ 7k or 3.5k..? I would think 7k is best?
I think David Allen had Hammond make his iron but not sure, the new owner at Allen Amps says, due to production not selling any iron..

[Brownie]

I believe Allen got Heyboer to make his iron. At least Heyboer made irons for the Blues Jr.

[HotBluePlates]

... Also have an Allen TO30D OT, Deluxe upgraded OT, 30 watts, 7k ohms w/8 and 16 sec’s, 6v6’s @ 7k or 3.5k..? I would think 7k is best?

The push-pull Princeton uses 8kΩ, the Deluxe Reverb uses 6.6kΩ.  I haven't tried to measure the primary impedance of my 6G3.

"30 watts" sounds like someone installing 6L6s into their 6V6-amp.  Such a scenario would make sense to drop to 3.5kΩ to double-current and double-wattage with the same power supply voltage.  I think I would leave the 3.5kΩ alone unless you're using 6L6s (and want a loud amp to be louder).

[dude]

Right and thanks, OT is only 7k primary with 8 and 16 ohm sec.  l’ll use secondary @ 8 or 16 ohm to match speaker for 7k.  l’ll use a 50k biasing pot incase l decide to try 6L6’s or even EL34’s (tying pin 8 and 1). For the bigger bottles, l’ll use 8 ohm into 4 ohm cab or 16 into 8, (3.5k primary), since this will be a head cab. I’ll use just one high and low inputs, with a switch for both channels, should be a nice head. I’ll post pics when l get it finished, have to draw up a layout for that narrow Hammond AO43 chassis. Thanks again for comments.

[WimWalther]

If you use a Hammond A0-43 chassis with the stock PT, but sub a 5Y3 In for the stock 5U4, you'll get a B+ of ~330V with a pair of EL84 biased up around 80-85%.

Or that's what I'm finding with my current project. And a pair of 6V6 should be a very similar load.

[dude]

Or that's what I'm finding with my current project. And a pair of 6V6 should be a very similar load.

I have built a 6v6 Plexi with the AO43 PT, never tried a 5Y3, but a 5AR4 puts about 400v on the plates, 5U4G about 375v, so l would assume a 5Y3 would be about 360v. A different amp than your 6G2 with EL84’s. I guess EL84’s draw less current than 6v6s.
The schematic for the 6G3 l was looking at stated much lower voltages, so the questions. Hope you got your EL84 Princeton issues fixed, how does it sound..?

[HotBluePlates]

... with a pair of EL84 ... a pair of 6V6 should be a very similar load.

... I guess EL84’s draw less current than 6v6s. ...

I agree that EL84 draw should be similar to 6V6, as they're both "12w class tubes."

If anything the EL84's total draw would be a little higher, due to the non-aligned screen grid & consequently the higher screen current.

OTOH, I have some US-made 6BQ5s that are actually beam-power tubes rather than true pentodes.  I've observed both coming from the same manufacturers (though perhaps different factories under the company's banner).  Perhaps these "beam power 6BQ5s" are 6AQ5 guts on a 9-pin base, but with whatever grid-pitch & spacing change was needed to get the 6BQ5's higher Gm.