Tubeworks RT-300 low volume

[jmaroto]

Hi;
Recently a friend of my gave me his old Tubeworks RT-300 stored for quite some years. The amp turns on without a problem, but have pretty low volume for a 300W amp; I have a 50W Peavey amp and sounds much louder than the Tubeworks.
Checking the internals found that the PCB had some routes fixed in the past( the fixes look correct to the schematic), most of the components test well with my DMM, what notice a little strange is that the transformer secondaries deliver 97 ACV to the power stage, but in the diode rectifier convert to +/- 65DCV to the power rails K135 and J50. Tested the Preamp section with a signal tracer and there's no drop of signal in the different control pots neither the EFX send/receive, so I keep the four A2D 6A4 diodes of the rectifier suspects even when tested good for short or open.
Does anyone have some experience with old Tubeworks similar to this or maybe have some ideas where I can check to repair the low volume problem?

[52 Bill]

...what notice a little strange is that the transformer secondaries deliver 97 ACV to the power stage, but in the diode rectifier convert to +/- 65DCV to the power rails K135 and J50.

I think that your rectifier diodes are fine.

Without the schematic, I'm only guessing here, but I would imagine that the ac secondary has a center tap that is grounded making each half about 48 volts ac, which when rectified would get your 65 volts dc.

[jmaroto]

You're correct Bill, the transformer have 3 secondaries, one for power rails 97ACV and center tab, one for the Preamp stage 30ACV plus center tab and one for the pream tube heaters 6ACV


This is the schematic I received from Genz Benz, stating this model was build before they acquired the brand so cannot provide with support.

[J M Fahey]

Thanks.
Can you post a larger image? This one is unreadable.

Worst case upload whatever file you received from Factory, without even opening it, as-is.

I suppose itīs a .PDF and you sent us a screen capture image, but you can straight attach a PDF to your post, see "manage attachments" when you answer.

[jmaroto]

Hi Fahey;
This is the file I received, even when it's a pdf there's not a lot of improvement.
Tubeworks RT3175-3300.pdf
I redrew it but as the resolution in original wasn't so good I can't assure the accuracy.

[glebert]

Since you have an effects loop have you tried injecting a signal into the receive, either from another device or just plugging a guitar in there? Similarly you can test the preamp signal by sending to another amp or mixer.

[jmaroto]

Hi Glebert, I already tried testying the signal routing with a signal tracer, no droping or lost in the pot controlers or the EFX Loop.