UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Superstar 6900N V6

SiriusHardware · 24th May 2020, 6:21 pm

Thanks for all the useful contributions since I last looked in. Just spent a little bit of time reading through. Thanks especially to Mike W for those detailed thoughts on the likely standing current we should expect through the output MOSFETs.

So where were we: Power to finals connected, power to driver not connected, bias supply links J3 and J4 out?

I'm assuming crackle's super PSU must have an ammeter built in, so we'll make the initial observations just using that.

Crackle, leave the power link (L11) for the driver MOSFET out for now.

If, during the following observations, the radio draws anything like 11A, unkey immediately and if it keeps on drawing heavy current after you unkey, slam the power straight off at the PSU.

Can you reinstate bias supply link J3 ONLY, key the radio in SSB TX with zero audio input, roger beep off, and observe and record the current drawn in SSB TX mode?

Then, remove J3, fit J4, and repeat the above measurement.

24th May 2020, 6:21 pm	#91
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,570	Re: Superstar 6900N V6 - Fault with SSB mode Thanks for all the useful contributions since I last looked in. Just spent a little bit of time reading through. Thanks especially to Mike W for those detailed thoughts on the likely standing current we should expect through the output MOSFETs. So where were we: Power to finals connected, power to driver not connected, bias supply links J3 and J4 out? I'm assuming crackle's super PSU must have an ammeter built in, so we'll make the initial observations just using that. Crackle, leave the power link (L11) for the driver MOSFET out for now. If, during the following observations, the radio draws anything like 11A, unkey immediately and if it keeps on drawing heavy current after you unkey, slam the power straight off at the PSU. Can you reinstate bias supply link J3 ONLY, key the radio in SSB TX with zero audio input, roger beep off, and observe and record the current drawn in SSB TX mode? Then, remove J3, fit J4, and repeat the above measurement.