Hot Rod Deluxe low power amp output

[Tone Meister]

I am on a series of shows and have been unable to get back to the amp, so this problem is not yet completely solved. The power amp is now healthy, but the preamp still has below normal output.

Hope to get back on the amp by July 12 or 13.

[Pedro Vecino]

"The schematic I posted in my first post is consistent with this amp, no discrepancies so far".
"Just play tested the amp with a known good speaker cabinet and the power loss is obvious. The amp works and switches channels just fine and is quiet and sounds ok, but clearly it is not producing full power."
"Connecting the PREAMP OUT into another amp produces a weak signal. However, connecting the preamp of another amp into the POWER AMP IN produces full power from the power amp."

Sorry for the delay in responding.
If the amplifier is exactly identical to scheme of first post it will be impossible to respond with the typical volume levels of a HR Deluxe.

Original schematic:



Oldest units are manually corrected in this way:



Later units have already adapted with correct circuit board, without bridges or added components.
This scheme corresponds to a HR Deluxe III. The mentioned elements are well represented in the new schematic.



Your amplifier may have some unknown problem but if the circuits of cathodes 2 and 3 are not identical to the latter scheme (or the previous correction, which is the same) is impossible to have the original behavior in gain and volume.

[ElectricBlue]

Thanks for the welcome. I'll start a new thread. The area is Colorado. I'm sure their are other places, I could find for faster turnaround, but I'm not familiar with the side of the business. But if this is SOP, I will do things myself - probably why I have this situation. Again, thanks for the welcome mat, I'll start a new thread. EB

[Tone Meister]

Pedro, isn't that is the same mod I ran across in THIS HOT ROD DEVILLE THREAD? That is where the 47 uF cap was added in parallel with the R10 1.5K across V1B which will drive the tone controls harder. Also, the bright switch has been moved to the cathode of V2A. Comparing the annotated schematics brings me to that conclusion as they are both early USA-built amps.

If that is the case, then I won't do anything else. The power amp is definitely healthy, but the preamp doesn't produce the amplitude I'm used to from these amps. It works well and sounds fine, so I'm gonna let the turd dry unless someone recommends the bypass mod.

[52 Bill]

The power amp is definitely healthy, but the preamp doesn't produce the amplitude I'm used to from these amps. It works well and sounds fine...

If you are satisfied that the amp is working normally, then you're done. If you think that it should be brought up to current specs, then add the mod and see if that makes it sound better to your ears.

[Tone Meister]

If you are satisfied that the amp is working normally, then you're done. If you think that it should be brought up to current specs, then add the mod and see if that makes it sound better to your ears.

You may recall that I didn't care for the Deville that was modded this way. It was a bit too thick and added too much gain across the board for my own tastes, so I'm gonna call it a day.

[Pedro Vecino]

What I have tried to explain is that the old schematic we have seen many times has never matched the real amplifier.
I have prepared at least fifty units (in Spain is a very popular amp in amateur, semi-pro circles) and none has matched this old schematic.
Differences between units of H.R. Deluxe / Deville over time (you can see in the third scheme corresponding to H.R. Deluxe III) are others and less abrupt.
Without 47uF capacitor in the second cathode, besides losing gain on both channels, also lose liveliness, electric character or whatever you want to call. Despite developing volume sounds duller. You might find an intermediate step putting in series with the electrolytic a 1K2 or 1K5 resistor. Sometimes I have use it but the amplifier uses this capacitor.

[ElectricBlue]

Welcome to the place.

It's really easier to start a new thread, especially as I don't think this is (quite) dead yet. Your issue may superficially seem the same but the cause could be quite different. Are you saying one of the main big electrolytics is microphonic? If so, then replace it.

Fix my problem. The main electrolytics was the problem. Now it just needs better tubes. My first tube amp, (not sure about the last) taught me a very simple lesson. No matter how much I hear about you want/need a tube amp - I don't. I"m looking for something mainly clean and reliable, at least to an certain degree. Cut through when necessary with good tune. My next purchase will be Solid-State. That's the era I come from, that's the amp era I started with, and will probably end. The SS amp's are a lot better today. Good Luck - Will talk again.

[marfu]

Hello !
I have one HOT ROD DELUXE , in Curitiba , Brazil.

Serial 120563.
Made in USA.

Have original Mod.