Ultra T401 LW - UK Vintage Radio Repair and Restoration Discussion Forum

Davewantsone · 13th Sep 2019, 9:07 am

I have recently repaired this receiver and it works very well on MW and SW with only a short length of wire for an aerial. I have read other comments on this forum that the LW is not very good and this is the case with my set. I have noticed however a difference between the actual wiring in the set and the circuit diagram around the LW coil. See picture. The bottom end of the secondary of the LW coil does not go to the 0.05 uF capacitor but on the set is wired to earth. THe MW and SW coils do go to the capacitor. The primary of the LW coil does not go to earth but like the MW and SW coils goes to the 470pF capacitor. No one has altered these connections on the set. The circuit is from the CD (VRSD).Are these connections correct or is the circuit diagram correct?

ms660 · 13th Sep 2019, 11:08 am

With LW selected measure the resistance between the control grid of the mixer to chassis, if it's zero to low the coils have been wired incorrectly so far as I can make out.

That part of the schematic in the Belgian manual agrees with the one you have posted.

Lawrence.

Davewantsone · 13th Sep 2019, 3:34 pm

The LW coil is clearly soldered to chassis at the same point that the 0.05uF capacitor. To correct it I would need to desolder the coil from chassis and connect a wire from this coil to the other end of the capacitor which goes to the low end of the SW coil? Has anyone actually got a radio that is wired as per the circuit diagram?

ms660 · 13th Sep 2019, 3:51 pm

Can't see why they would want to defeat the AGC to the mixer on LW.

I would do the resistance test from the mixer's grid to chassis when switched to LW to confirm...

Lawrence.

Davewantsone · 14th Sep 2019, 9:40 am

Well I rewired the LW coil as per circuit diagram, with the result it worked slighty worse with breakthrough of Radio 5 on the HF end of LW. So I will put it back to how it was originally. (all the LW trimmers work). The 470 kHz IF trap is set OK.
I am more than happy with MW and SW. so I will leave it at that.

Davewantsone · 15th Sep 2019, 6:40 pm

LW is now perfect. I unsoldered L7 and fitted a ferrite rod witk LW coil, all background noise has gone and now have a clear R4 signal!

13th Sep 2019, 9:07 am	#1
Davewantsone Hexode Join Date: Dec 2011 Location: Wigan, Greater Manchester, UK. Posts: 291	Ultra T401 LW I have recently repaired this receiver and it works very well on MW and SW with only a short length of wire for an aerial. I have read other comments on this forum that the LW is not very good and this is the case with my set. I have noticed however a difference between the actual wiring in the set and the circuit diagram around the LW coil. See picture. The bottom end of the secondary of the LW coil does not go to the 0.05 uF capacitor but on the set is wired to earth. THe MW and SW coils do go to the capacitor. The primary of the LW coil does not go to earth but like the MW and SW coils goes to the 470pF capacitor. No one has altered these connections on the set. The circuit is from the CD (VRSD).Are these connections correct or is the circuit diagram correct? Attached Thumbnails

13th Sep 2019, 11:08 am	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Ultra T401 LW With LW selected measure the resistance between the control grid of the mixer to chassis, if it's zero to low the coils have been wired incorrectly so far as I can make out. That part of the schematic in the Belgian manual agrees with the one you have posted. Lawrence.

13th Sep 2019, 3:34 pm	#3
Davewantsone Hexode Join Date: Dec 2011 Location: Wigan, Greater Manchester, UK. Posts: 291	Re: Ultra T401 LW The LW coil is clearly soldered to chassis at the same point that the 0.05uF capacitor. To correct it I would need to desolder the coil from chassis and connect a wire from this coil to the other end of the capacitor which goes to the low end of the SW coil? Has anyone actually got a radio that is wired as per the circuit diagram?

13th Sep 2019, 3:51 pm	#4
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Ultra T401 LW Can't see why they would want to defeat the AGC to the mixer on LW. I would do the resistance test from the mixer's grid to chassis when switched to LW to confirm... Lawrence.

14th Sep 2019, 9:40 am	#5
Davewantsone Hexode Join Date: Dec 2011 Location: Wigan, Greater Manchester, UK. Posts: 291	Re: Ultra T401 LW Well I rewired the LW coil as per circuit diagram, with the result it worked slighty worse with breakthrough of Radio 5 on the HF end of LW. So I will put it back to how it was originally. (all the LW trimmers work). The 470 kHz IF trap is set OK. I am more than happy with MW and SW. so I will leave it at that.

15th Sep 2019, 6:40 pm	#6
Davewantsone Hexode Join Date: Dec 2011 Location: Wigan, Greater Manchester, UK. Posts: 291	Re: Ultra T401 LW LW is now perfect. I unsoldered L7 and fitted a ferrite rod witk LW coil, all background noise has gone and now have a clear R4 signal!