Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Bruce on January 12, 2019, 03:29:33 pm
-
Looking for advice..updating amp new caps pt24 heyboer,ot deluxe reverb extra one collecting dust.. Should I use the 2 diode set up ? ,or use pre fab bridge rectifier,.do you think one is better than the other ?..With the bridge rectifier I have to lose the center tap off the pt ,with the two diodes you use center tap ?
-
I'd leave it 2 diode, plus, no muss no fuss with the CT, and the next tech won't get confused :icon_biggrin:
-
Be careful! If this is the TP24 sold by allen amps...
TP24 power transformer requires a full-wave-bridge type solid-state rectifier. It does not support a tube rectifier.It is rated 120V to 280V at 200mA with a 6.3V center-tapped heater winding rated 4A. It will support a power supply rated approximately365V DC at 150mA DC. This is sufficient for a pair of EL34s in fixed bias or a pair of 6L6s in cathode bias or a single ended amp usinga big 6550/KT88 power tube - plus 3 or 4 preamp tubes. It also has a pair of brown leads rated 20V at 100mA. This makes it a great bolt-inupgrade for the Blues Jr.™ (same color code leads, too) where a little higher B+ voltage and better voltage regulation are desiredfor more headroom or where 6L6/EL34 power tubes are to be installed for a more powerful amp. 2" by 2-1/2" mounting centers means it willfit a Champ™ or Princeton™ chassis. 2-5/8" tall above mounting surface. 3.8lbs. 10" Unistrand pretinned leads. A great projecttransformer that is compact and powerful and produces a more reasonable B+ voltage making it suitable for many cathode biased, single-endedand EL84 based circuits. Made in the U.S.A! Add $10 for push on connectors for a Blues Jr.™ amp.
-
looked at schematic only :think1:
I was just gonna accept failure, but this haunted me :laugh:
requires a full-wave-bridge
no CT?
I went hunting for a drawing of both tp24 heyboer and allen amps, it was like a seachengine 20min run-around.
-
Thanks for responding,I am trying to overbuild bullet proof it ..Love this little amp,cool with a 12” speaker .I am not looking for great tone just clarity,it sounds like a monster with the fractal thru it ...2 diodes make a full wave but bridge rectifier I have not used,are there any benefits for bridge over full wave .
-
For any given transformer... a bridge will give you twice as much B+ as a full wave two diode rectifier. You cannot arbitrarily interchange a bridge and a two diode rectifier.
-
Thanks Sluckey ..When you say twice as much B+ ,do you mean say 310 on the power transformer,to 620 from the same pt ,? I don’t get it ..I will stick to the 2 diode setup but I don’t really understand how 2 more diodes get you twice the vdc thanks
-
here's a page that does a pretty good comparison
https://www.elprocus.com/full-wave-bridge-rectifier-versus-center-tapped-full-wave-rectifier/
-
> Should I use the 2 diode set up ? ,or use pre fab bridge rectifier
As Sluckey says: use the diode affair that the PT was *designed* for.
It is not a mix/match kind of choice. As designed it gives 300V 80mA. FWB would give 600V 40mA. Been there done that, nearly blew-up some huge 450V caps.
Get two good diodes. You "can" use half a FWB, but there's no advantage, and considerable possibility of mistake (fwooom!).
-
> understand how 2 more diodes get you twice the vdc
The 2-diode affair uses *half* the winding, alternately.
The FWB uses the *full* winding. Obviously twice the voltage.
On a Clean Sheet: The difference is: do you want to pay for a more-turns 3-lead PT, and just two diodes? Or do you want a simple PT and a 4-diode rectifier? Side-effects include diode voltage and current rating and wiring labor. (And in vacuum rectifiers, cost of cathode-stuff.)
With a lump of iron In Hand, do how it was used before.
And in this case I don't see that a working MusicMaster needs any PT or rectifier "upgrade". There's no problem here.
-
Thanks so much