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Can we have a G.S.G. documentation designated for just 45 tubes. I am temp to buy a board to build a 45 amp but need an easy to follow instruction before I order the board, transformers, parts, etc....

There are various tips/tricks on how to make it work but i am not technical enough to be able to pick up and understand the information.

Many thanks.

Three things that would be need to be done is double the value of cathode resistor from 900 ohms to 1800 ohms and the output transformer needs to be a 5k primary impeadance .Also the filament voltage need to be 2.5 volts instead of 6.3 .

The three 2.7 k resistos in the cathode would change to 5.4 k ohm .
The nearest standad value would be 5.6 K ohm which would be 1866 ohms .

What Mark said and the following link:
http://www.diytube.com/phpBB2/viewtopic.php?t=5499

I haven't heard any reports on this build yet, so you might want to wait until everything is confirmed working.

Shannon

Thanks Shannon. Please post update when you have it.

You may want to review my 15-Aug-2012 post at this link also:

http://www.diytube.com/phpBB2/viewtopic ... bff6fc8e5d

Keith

Keith,

That is very helpful. I am able to understand your instruction except "Power supplied to the primary windings of the filament transformers and the EDCOR also passes through MF72-120D15 inrush current limiters."

How do you connect/hook up this. I can not see the MF72-120D15 in your gut/s picture.

If I follow this exact instruction, will I be able to complete the 45 amp. Thanks.

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The Amplifier uses 2 Hammond 166M2 filament transformers to supply 2.5 VAC to the 45 tubes. The center tap on the secondary winding for each filament transformer connects to pin 5 on J3 or J4 on the GSG board. D1 through D8 are not populated. Likewise, C11 through C14, R19 and R20 are not populated since the Hammond 166M2 transformers supply filament power.

The Amplifier uses 4.3k resistors for R15a, R15b, R15c, R16a, R6b and R16c. The parallel combination of 3 resistors per channel makes a bias resistance of 1.43 K.

The amplifier uses an EDCOR XPWR106 (275-0-275V @ 175ma & 6.3V @ 4A) power transformer. Since there is only one 6.3 V winding it is necessary to put a jumper wire from J3-1 to J4-1 and J3-2 to J4-2 to supply 6.3 volts to the 6SL7 and 6AX5-GT.

A second Hammond 156R choke replaces R17a and R17b. With the EDCOR XPWR106 power transformer, the power supply section produces 300 volts at B+

Plates from the type 45 tubes connect to the 5 K-ohm taps on the James transformers.

Power supplied to the primary windings of the filament transformers and the EDCOR also passes through MF72-120D15 inrush current limiters.

The link below shows a diagram of the 120 VAC circuit:

http://www.diytube.com/phpBB2/album_pic.php?pic_id=174&sid=40e15c102e6e793aad4116782733f6a4

My goal for the 15-Aug-2012 post was to document all the changes to the original 6B4G GSG design that are needed to build a duplicate of 45 GSG I use every day.

Keith

Thanks Keith.