Prince Royal schematic

[Blind Lemon]

Anybody have a schematic for TH Prince Royal. I have one on the bench and am thinking the problem is in the boost circuit. Very low output.


TIA


BL

[pompeiisneaks]

I don't kno of them myself, and it seems there's only a 'king royale' in the schematics library: http://el34world.com/charts/Schematics/files/top_hat/tophat_kingroyale.pdf

But maybe the king is similar to the prince?  The schematic is obviously one someone did by hand...

Hope that helps anyway? 

[sluckey]

Let's see some pics Blind Baby. I always want to call you Blind Melon Chitlin' for some reason.   

[Blind Lemon]

Steve how you doin? You missin the agency I bet.


I'll send some pic's when I get home from work. 


BL


https://www.google.com/search?q=top+hat+prince+royale&client=safari&hl=en-us&biw=1024&bih=672&tbm=isch&source=lnms&sa=X&ved=0ahUKEwin9buDppbNAhVB_IMKHfEtCM8Q_AUICCgB&dpr=2

Just did a search for image. Third row 2nd over. It's a SE EL84 with an EF86 front end. Boost board on the left.
That will have to do until I get back to the house.

[pompeiisneaks]

Sorry that image is so small that my bad eyes can't make much sense of it :(

If you can get some good high res ones that would be great.

~Phil

[Blind Lemon]

Sorry for the delay.

[Blind Lemon]

More:

[Blind Lemon]

again:

[Blind Lemon]

Last:

[SILVERGUN]

Do you always have low volume or just when you switch in the boost?

[Blind Lemon]

Low all the time. Got a schematic?

[SILVERGUN]

No...sorry
 
Looks like they tacked a boost pedal on the front end.
 
I'd bypass it and see if you still have low volume....it'll help you rule out the boost circuit.

[Blind Lemon]

thx

[Blind Lemon]

Here's what I know. When I disconnection the power and input into the boost peddle the amp works. (Fine?) The plate of the EL84 is running at a lower V than the suppressor grid. (A=266 vs G3 =279) So it's running in triode. (?)

I hate peddles. Guess I'll pull it out and draw it up. The sand is a J201.

[pompeiisneaks]

Well, I can't see the underside of that booster, but the likely candidates for problems would be one of those three electrolytics, the one radial and two axials.

Depending on how old they are, they could be dead/dying.  Otherwise the rest of the circuit should be pretty simple stuff and running at pretty low voltages.  If the pnp/npn went out, it wouldn't boost at all I'd think (Or I'm guessing that's whats there, but it could be a jfet etc?)

~Phil

[Blind Lemon]

First pic above. Built in 2002 by Bobby. (?)

It make no noise with the boost on and with it off you can just hear it very faintly.

[HotBluePlates]

... The plate of the EL84 is running at a lower V than the suppressor grid. (A=266 vs G3 =279) So it's running in triode. (?) ...

Did you mean "G2" (screen grid)?

Your hand-drawn circuit shows G3 connected to the EL84 cathode (which is an internal connection). Pin 9 would be G2.

The drawn schematic also shows the screen at the opposite side of the OT as the EL84 plate; that equals pentode-mode. Triode-mode would be plate & G2 on the same side of the OT winding.

Since the plate & screen grid ultimately tie to the same filter cap (according to the drawn schematic), but the plate has the d.c. resistance of the OT in the way, it would be natural for the plate voltage to be lower than the screen voltage. Doesn't really matter to the tube in this case.

[2deaf]

From the symptoms and the photo's, I would say that the gate of the J201 jFET is connected to the input at all times.  The jFET may have failed with the gate shorted or nearly shorted.

With the switch on "Boost", what is the resistance across the input jack with a phone plug inserted?  Try reversing the DMM leads and see what resistance it reads like that.

 

[Blind Lemon]

See if this looks right. Not sure what kind of diode that is.

HBP - You are correct, I was mistaken. G2 not G3.

[Blind Lemon]

I had some 201's, so while I had the little board out I ut out the old one and soldered in a new one.

BINGO