A15 MKII no sound

I apologise for writing in English.

Hi Martin, I have built the Madamp A15 MkII and I'm getting no sound or even hum. I have checked continuity from the 8 ohm socket to speaker, the DC resistances of the output transformer primary and secondaries which are correct. However ALL the voltages (with tubes installed) are outside tolerance - B+ is 306 v, + on rectifier is 344 v, pin 6 on V4 is 208 v etc. The heater voltage seems correct at 7.03 VAC.

The B+ voltage going to the preamp board is dropped at R36 to 289 v and all test points are similarly over-voltage by 20% +. Nothing is getting hot. I have checked and double checked the wiring but obviously I've done something wrong! I can send all the test point voltages if it helps.

Help! Thanks, Brian

Zitat von eBernd;325288

Hi Brian,

two questions - it's just for preparing the search for the error:

1. What is your measured mains voltage?
2. Do all heaters visibly work?

Bernd

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Hi Bernd, thanks for your quick reply. The mains voltage is 235 VAC and all the heaters are glowing as expected.

Regards, Brian

Zitat von eBernd;325321

Hi Brian,

what about the voltages across R51 and R52 (35 mV)

May be a wrong wiring of the OT will hinder the currrent in the output stage...

Bernd

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Hi Bernd - thank you for drawing my attention to R51 and R52 where I found my mistake - I had not grounded pin 4 on either V5 or V6. Very embarrasing! The amp works perfectly now - thank you for your help. Brian.