Hammond 290CAX wiring for Princeton 6G2 using the Rob Robinette lay out version 8 need help PT primaries wiring

[Ronecatt62]

hello all new guy here I have built a 6G2 from the lay out I found here on the forum "Rob's version 8" I am using a Hammond 290CAX with the 275V option. my question is how do i wire the Primaries to the DPST switch. the colors of the primary wires are different from Rob's layout.I have orange and brown and white and black wires which colors go where on the switch. I tried orange and brown paired together and black and white paired together to the switch like in Rob's lay out but got nothing when switched on . I just don't have the experience to figure out what i am doing wrong.I am only getting voltage to 1 set of windings on the DPST switch not sure what the heck i am doing wrong.please go easy on me I'm trying but need expert help . any suggestions on my wiring problem would be greatly appreciated. thank you .

 

[printer2]

You have a 120/240V transformer (290CAX) and you have a 120V transformer (290AX) datasheet. The datasheet for your transformer,

https://www.hammfg.com/files/parts/pdf/290CAX.pdf

Get back to us if you need more help.

 

[King Fan]

hello all new guy here I have built a 6G2 from the lay out I found here on the forum "Rob's version 8" I am using a Hammond 290CAX with the 275V option.

Welcome. Yikes, I don't know who labeled that 'Rob's version 8' but I'm guessing Rob bears no responsibility -- it looks a lot like one I drew, just following his examples on similar amps. That musta been before I started adding my name and posting disclaimers like "this may contain errors."

Is the image you shared a diagram of your PT, though? If so, your *primaries* are both black, and they're interchangeable. Edit: Oh, I see Printer figured it out.

 

[King Fan]

Sorry, got called away from this earlier. Here's a pic of the primary wiring for the 290CAX shared by TDPRI member @zook back in 2019.... Yeah, the US version is on the right. You can wire neutral to the orange/white pair and hot to the brown/black pair. Does that make sense?

Also, I built this amp six years ago and mostly made the drawings just to document it for my own reference. I find my files go up to a version 10. So I added some disclaimers and cautions to that. Here's a PNG and I'll stick a PDF below -- but let me emphasize this wasn't drawn or shared as a guide to building an amp.

Finally, I'd strongly discourage you from just trying high voltage stuff to see if it works. As Printer says, ask questions if there's something you don't understand.

 

[Uncle Daddy]

As a side note, I've used 2 of these PTs, and with 240v mains I couldn't get anywhere near 60% max PD with the suggested 10k bias pot and 27k tail resistor (using EH 6v6gt tubes) with the 275v taps. 18k put the sweep right in the middle.

Edit- KF's drawing has 15k- that works too. The 27k is on other drawings going around.

 

[Ronecatt62]

You have a 120/240V transformer (290CAX) and you have a 120V transformer (290AX) datasheet. The datasheet for your transformer,

https://www.hammfg.com/files/parts/pdf/290CAX.pdf

Get back to us if you need more help.

oh geez thank you I posted the wrong transformer diagram. I do have the correct one thank you for clearing this up .

 

[Ronecatt62]

hello again all, thank you for the support. 6g2 amp is up and running ! I did voltage checks and added 5y3 rectifier tube checked voltages all good, added pre amp tubes voltage check was good.then added output tubes hooked up speaker and powered on amp. on my bias pro i have plate voltage of 301 volts and plate current is 28 mv with a slight adjustment on bias pot .amps sounds good but there are a few issues i am not able to figure out with volume pot turned all the way down i get a buzz like its grounding out, but when i turn it up past 1 it goes away...? I also have some bleed over from tremolo when foot switch is not conected .I was also woundering if i need a centertap off of pilot light will this help with some low level hum.? any sugestions on how to trouble shoot volume pot issue and tremolo bleed over and center tap would be great . thank you all

 

[Uncle Daddy]

The diode mod on the trem intensity pot did a lot for trem breakthrough on my 6g2.

 

[Uncle Daddy]

The Hammond PT has a center tap for the heaters; you don't need the resistors off the pilot light.

 

[Uncle Daddy]

If you have the diode inplace and are still getting trem breakthrough, you can try adding these black snubber caps one at a time to see if it goes away. One of my builds had an issue with crossover distortion between the volume and trem pots when either was maxed out; adding the cap to the left of the 3 trem caps fixed it.

 

[King Fan]

I also have some bleed over from tremolo when foot switch is not conected

Do you mean when it's not plugged in, or when it's switched off? IIRC the 6G2 trem remains on when the footswitch is unplugged, so folks who want to remove the footswitch and have no trem simply build a shorted jack.

 

[Ronecatt62]

tremolo switch is plugged in sorry for not explaining better . not much bleed over now it was a cold solder joint on plug seems to be ok now . I am still having some issue with volume pot when its turned all the down I get a loud buzz but when I turn it up very slightly it goes away? bad pot? its a cts 1meg lin. pot. Any suggestions on the volume pot issue once that's cleared up i think it good to go amp sounds great tremolo is nice too . thank you .

 

[Ronecatt62]

The Hammond PT has a center tap for the heaters; you don't need the resistors off the pilot light.

ok good to know thank you for the info . learning a lot from everybody much appreciated!

 

[Ronecatt62]

The diode mod on the trem intensity pot did a lot for trem breakthrough on my 6g2.

have this mod installed thank you .

 

[King Fan]

I am still having some issue with volume pot when its turned all the down I get a loud buzz but when I turn it up very slightly it goes away? bad pot? its a cts 1meg lin. pot.

This seems to come up sometimes. I found this old thread where our wise friend @Lowerleftcoast explains the pot construction issue and helps a member through a few different fixes, one of which works.

Hum only at volume 0 5F2A

5F2A build, hums at zero but as soon as you inch the volume knob up it goes dead quiet and the amp works perfectly. Voltages look good, measuring the 2nd half of V1 (pin 6 or 8) eliminates the hum completely with the DMM on the pin, measuring all B+ voltages quiets the hum and gets quieter the...

www.tdpri.com

I'm guessing you know something about amps — I’m impressed your startup went so well, and I’m interested you chose a linear volume pot.

 

[Lowerleftcoast]

@Lowerleftcoast explains the pot construction issue and helps a member through a few different fixes

A grid stopper might work for this. Worth a try.

 

[Ronecatt62]

well I have tried to get the 6g2 to function but have come to the conclusion that I have no business building amps. I would like to thank everyone who offer advice. I tried and came close but failed. I tossed the amp in the trash tubes and all and am going back to hobbies I am better suited to. thank you again for the warm welcome. signing off Ron.