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Using TSE 45 to drive a GM70 (or other big power tube)

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Tubelab_com

Tubelab_com

Member
Joined 2005
tubelab.com
You need a method of connecting the 45 to the GM70. The usual coupling capacitor / bias resistor will work but will not be optimum. Big tubes like the 211, 845, GM70, and 833A need a low impedance drive source, with a low DC resistance path to the bias source. These attributes are needed for low distortion and good overload recovery.

The usual method is to replace the OPT with a driver transformer that matches the 45 to the grid circuit of the tube being used. That works if a good quality transformer is used.

I chose to replicate the drive circuit that is currently in use between the 5842 and the 45 on a small PC board using larger parts to handle the higher voltages present. My circuit design is here:

845SE
 
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cotdt

Member
Joined 2005
Can the TSE 45 PCB be used as driver stage for GM70/845? I would just replace the 45's 10ohm resistor with a CCS? GM70 would then just be a drop-in replacement for 845 in that circuit except with 20V heaters.

Is there a PCB for Powerdrive or a universal power supply that you sell?
 
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jrobson

Member
Joined 2011
robsoncnc.com
cotdt said:
Can the TSE 45 PCB be used as driver stage for GM70/845? I would just replace the 45's 10ohm resistor with a CCS? GM70 would then just be a drop-in replacement for 845 in that circuit except with 20V heaters.

Is there a PCB for Powerdrive or a universal power supply that you sell?
Click to expand...

Hi

I'm researching something similar... In another post George said he doesn't have any powerdrive PCB's.

Essentially yes you remove the OPT's, R18&R29 and plug in a powerdrive circuit at T2-2 and T3-2.
On the schematics the 845SE also has +150V going into both 2SK2700's, where in the TSE board it is connected to B+... This should still be ok I think? The second powerdrive 10M45's are set for 91ohms which is about 30 something ma...
Other than that you need a good power supply.... I've posted a GM70 one on another thread that you can use to get going...
 
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