Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Planobilly on December 08, 2016, 01:47:09 pm

Title: Unexpected high voltage at output transformer Fender Deluxe clone SOLVED Thanks
Post by: Planobilly on December 08, 2016, 01:47:09 pm

Hi guys.

This is a Mission Amp Deluxe clone. With no tubes in the amp except the 5y3s rectifier I measure these voltages.

407 VDC at standby switch.

520 VDC at pin 3 of the output tube when I turn on the standby switch.

523 VDC at the first 16uf filter cap.

(http://i.imgur.com/twVzvcB.png)

(http://i.imgur.com/PNnlNb9.jpg)

(http://i.imgur.com/zaemuwV.jpg)

Have any idea what could cause these voltages. The AC voltages on the power transformer measures close to the datasheet.

The amp came to me with a burned eyelet board (5K1-2W had burned the board). I made a turret board replacement with the same layout. I installed all new components except the filter caps and one .022 cap (pin 1 V2) The only other difference in the schematic is the power transformer has a center tap for the 6.3 heater so no 100 ohm to ground resistors.

Thanks,

Billy

Title: Re: Unexpected high voltage at output transformer Fender Deluxe clone question
Post by: sluckey on December 08, 2016, 02:34:26 pm

Quote from: Planobilly on December 08, 2016, 01:47:09 pm

Hi guys.

This is a Mission Amp Deluxe clone. With no tubes in the amp except the 5y3s rectifier I measure these voltages.

407 VDC at standby switch.

520 VDC at pin 3 of the output tube when I turn on the standby switch.

523 VDC at the first 16uf filter cap.

Have any idea what could cause these voltages. The AC voltages on the power transformer measures close to the datasheet.

That's what you should have with no tubes to put a load on the power supply.

Title: Re: Unexpected high voltage at output transformer Fender Deluxe clone question
Post by: Planobilly on December 08, 2016, 03:16:59 pm

Thanks,

I will continue on and install tubes and continue the testing.

Thanks,

Billy