Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on March 25, 2023, 10:22:38 am

Title: PT repurpose
Post by: joesatch on March 25, 2023, 10:22:38 am
Can a Hot Rod 40 PT be re-purposed to drive 4 x 6V6 and 3 12ax7 ?
Title: Re: PT repurpose
Post by: sluckey on March 25, 2023, 10:35:27 am
Is that a Ford or Chevy?
Title: Re: PT repurpose
Post by: joesatch on March 25, 2023, 10:36:59 am
building a delorean
Title: Re: PT repurpose
Post by: sluckey on March 25, 2023, 10:44:10 am
If you want a better answer you need to provide accurate info. I've never heard of a "Hot Rod 40". What do you really want to know?
Title: Re: PT repurpose
Post by: acheld on March 25, 2023, 10:45:16 am
LOL.   I was going to ask which carb you're running -- Edelbrock, Weber, or what. 

36958?
Title: Re: PT repurpose
Post by: joesatch on March 25, 2023, 10:52:32 am
equivalent of this PT. I could also go with 4 x EL84.
Title: Re: PT repurpose
Post by: sluckey on March 25, 2023, 10:59:58 am
Let me put it another way... WTF is a "Hot Rod 40"?
Title: Re: PT repurpose
Post by: tubenit on March 25, 2023, 11:05:26 am
Look at the voltage on the PT you suggested and ask yourself how will you rectify it?   Then look at the maximum rating for EL84 plate voltages.


Also look at the ma rating on EL84's.


With respect, Tubenit
Title: Re: PT repurpose
Post by: mresistor on March 25, 2023, 11:10:34 am
Guess he's talking about a Fender Hot Rod Deluxe.  2 x 6L6  40W  would be cool if he presented some PT specifications for the replacement PT for that amp. 


This may or may not be the one he is refering to.   https://www.tubesandmore.com/products/transformer-fender-power-hot-rod-deluxe
Title: Re: PT repurpose
Post by: acheld on March 25, 2023, 11:10:47 am
Time for you to learn some math.   Data comes straight from data sheets. 

6V6 in PP -- Plate current is 92mA per pair.  So, 180mA current draw on your HT rail.   The small tubes draw what, 2mA? negligible.   That is well within a 290UX range.

Heaters:   6V6 draw about 450mA per tube, so 1.8A.  12AX7 about 300mA per tube (parallel), so 0.9A.  So, about 2.7A altogether, well within a 290UX range as well.

What rectifier?   What willl you use the additional 39V secondary for?

Title: Re: PT repurpose
Post by: joesatch on March 25, 2023, 11:25:32 am
FWB rectification.
Title: Re: PT repurpose
Post by: sluckey on March 25, 2023, 11:28:42 am
Guess he's talking about a Fender Hot Rod Deluxe.
You think? Why not a Hotrod Deville? Or a hotrod Ford?

My point is that he could be accurate/specific with his info rather than throw out something ambiguous. Then we would not have to painfully drag the info out of him.
Title: Re: PT repurpose
Post by: joesatch on March 25, 2023, 11:34:22 am
sorry folks. i figured everyone here was familiar with the Hot Rod 40 probably the most popular amp sold today. I will be more forthcoming in the future.
Title: Re: PT repurpose
Post by: sluckey on March 25, 2023, 11:41:12 am
The Hot Rod 40 is a modified 1940 Ford coupe. Everyone knows that. It doesn't even have a PT. It does have a posi-traction rear end.

Title: Re: PT repurpose
Post by: mresistor on March 25, 2023, 12:06:57 pm
The Hot Rod 40 is a modified 1940 Ford coupe. Everyone knows that. It doesn't even have a PT. It does have a posi-traction rear end.


It's a re-purposed PT cruiser..    (and because a HR DeVille is a 60W amp) 
Title: Re: PT repurpose
Post by: PRR on March 25, 2023, 12:49:50 pm
...i figured everyone here was familiar with the Hot Rod 40....

Don't assume we are as smart as we are beautiful.

However Google agrees with you. Even though Fender never made "40" part of the model name, amps out-number Fords 10:1 in a Google search, and nothing else comes close.
Title: Re: PT repurpose
Post by: joesatch on March 25, 2023, 01:30:44 pm
looking for advisement on this PT. It's not much of an iron. Other 40 watt PT's are twice as heavy and much thicker. What is the implication of such a measly PT?
Title: Re: PT repurpose
Post by: sluckey on March 25, 2023, 01:46:24 pm
Light weight probably doesn't mean much on a 1/4 mile track. Could be a loser at a NASCAR event.
Title: Re: PT repurpose
Post by: joesatch on March 25, 2023, 01:48:16 pm
what is less strain on this PT  four 6V6 or four EL84 ?
Title: Re: PT repurpose
Post by: sluckey on March 25, 2023, 02:12:31 pm
You'll be changing 84s more often than Dale Jr. changes plugs at Talladega.
Title: Re: PT repurpose
Post by: mresistor on March 25, 2023, 02:31:56 pm
what is less strain on this PT  four 6V6 or four EL84 ?


Why do you want to us 4 power tubes? 
Title: Re: PT repurpose
Post by: joesatch on March 25, 2023, 02:33:35 pm
because i'm building a stereo power amp
Title: Re: PT repurpose
Post by: tubenit on March 25, 2023, 02:42:33 pm
Quote
what is less strain on this PT  four 6V6 or four EL84 ?


Did you look up the voltage on the PT you provided a link for?  Then did you multiply that by 1.4 if you're using solid state rectification to get a wild guesstimate at what voltage you're looking at?  OR did you look at the B+ node A voltage on the schematic you posted?  What did it say for voltage on node A?

Then did you look up the maximum voltage rating for the plates of the EL84's?   

I understood you were asking for help regarding the use of the PT?  Correct?  I gave you a tube data sheet to help you find the answer.

I'm trying to help you out here, but you're going to have to do some work on this on your own.

Respectfully, Tubenit
Title: Re: PT repurpose
Post by: joesatch on March 25, 2023, 02:50:59 pm
i'll research it. I really come here in case someone has done this and has a gotcha to stop me in my tracks.

(https://gifdb.com/images/file/michael-scott-ok-hzw1544kgvqywji3.gif)
Title: Re: PT repurpose
Post by: sluckey on March 25, 2023, 03:11:08 pm
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