ultra t401 help please - UK Vintage Radio Repair and Restoration Discussion Forum

waspman · 29th Sep 2009, 9:29 pm

I am new to radio repair with a VERY LIMITED electronic knowledge and am trying to repair a ultra t 401.It works but has VERY low volume I have replaced c 21 (a f coupling capacitor ) and the output transformer seems ok.The on off volume control is reading 2 meg ohms on the outer tags and varies from0.2 to 2 meg on the centre and left tag if that makes any sense.I am lucky and have a t401 that works and the volume control on that varies from 30 to0.9 meg on centre tag to left tag so I am assuming that might be the problem.Any help locating a replacement gratefully received.Or any other suggestions as to the problem would be helpful.While I am here is there anywhere local to Poole Dorset that I can go to increase my electronic knowledge. Many Thanks

howard · 29th Sep 2009, 11:34 pm

Hello,

Have a look at the write-up of the restoration of my Ultra T401 to get an idea of what might need doing to it ....

https://www.vintage-radio.net/forum/...highlight=t401

The switched volume potentiometer should be 1 meg ohm so maybe a replacement of the wrong value has been fitted at some time. If so change it but that alone probably won't fix your T401.

I suggest you change all the wax capacitors, there aren't many in this set. Then check the HT, mine measured 194 volts at the smoothing capacitor. If your second T401 works well, then swap over the valves to see if that helps.
Be careful when removing these valves, grip them by their bakelite bases, not the glass envelopes and prize off the top clips by twisting a screwdriver blade between the clip and the base of the connector on the top of the valve.

Let us know how you get on.

Howard

waspman · 30th Sep 2009, 8:34 pm

A great writeup of your restoration thanks for advice Howard.
Sorry but my first post was only part of the story,my ultra with the volume problem was my first attempt at a restoration
It was in a bad state the case was ok, one knob missing, valve VP41 was broken ,rusty chassis, wires in a bad state ect.
I got a new set of valves changed all the wax capacitors except c21 (missed this one) and the electrolytics, cleaned and painted the chassis, renewed wires above the chassis.
Cleaned the case renewed the mains lead.
After all this got a sound not loud but a good result for me
With my lack of knowledge there was no more I could do so I moved onto next project intending to come back when I had more experience.

After getting another t401 with a broken case smashed glass but works well I have gone back to the first.
The switched volume potentiometer is a 1 meg but must be faulty so I will try to get a replacement.
By the way using the good t401 tested all the old valves and all were ok.

waspman · 30th Sep 2009, 10:48 pm

Success I fitted a V24 standard potentiometer - Log switched
- Resistance (Ω): 1M from bowood web site showed no wats or volts for item but nothing to lose so fitted it and hey presto radio working fine.
All I need now is case, glass, 2 knobs back and I will have 2 ultra,s The second one is a Ultra ET 4012 so probably a later model. The voltage selector is internal on this model and the station dial is different too.

29th Sep 2009, 9:29 pm	#1
waspman Retired Dormant Member Join Date: Jul 2009 Location: Poole, Dorset, UK. Posts: 5	ultra t401 help please I am new to radio repair with a VERY LIMITED electronic knowledge and am trying to repair a ultra t 401.It works but has VERY low volume I have replaced c 21 (a f coupling capacitor ) and the output transformer seems ok.The on off volume control is reading 2 meg ohms on the outer tags and varies from0.2 to 2 meg on the centre and left tag if that makes any sense.I am lucky and have a t401 that works and the volume control on that varies from 30 to0.9 meg on centre tag to left tag so I am assuming that might be the problem.Any help locating a replacement gratefully received.Or any other suggestions as to the problem would be helpful.While I am here is there anywhere local to Poole Dorset that I can go to increase my electronic knowledge. Many Thanks

29th Sep 2009, 11:34 pm	#2
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: ultra t401 help please Hello, Have a look at the write-up of the restoration of my Ultra T401 to get an idea of what might need doing to it .... https://www.vintage-radio.net/forum/...highlight=t401 The switched volume potentiometer should be 1 meg ohm so maybe a replacement of the wrong value has been fitted at some time. If so change it but that alone probably won't fix your T401. I suggest you change all the wax capacitors, there aren't many in this set. Then check the HT, mine measured 194 volts at the smoothing capacitor. If your second T401 works well, then swap over the valves to see if that helps. Be careful when removing these valves, grip them by their bakelite bases, not the glass envelopes and prize off the top clips by twisting a screwdriver blade between the clip and the base of the connector on the top of the valve. Let us know how you get on. Howard Last edited by howard; 29th Sep 2009 at 11:49 pm.

30th Sep 2009, 8:34 pm	#3
waspman Retired Dormant Member Join Date: Jul 2009 Location: Poole, Dorset, UK. Posts: 5	Re: ultra t401 help please A great writeup of your restoration thanks for advice Howard. Sorry but my first post was only part of the story,my ultra with the volume problem was my first attempt at a restoration It was in a bad state the case was ok, one knob missing, valve VP41 was broken ,rusty chassis, wires in a bad state ect. I got a new set of valves changed all the wax capacitors except c21 (missed this one) and the electrolytics, cleaned and painted the chassis, renewed wires above the chassis. Cleaned the case renewed the mains lead. After all this got a sound not loud but a good result for me With my lack of knowledge there was no more I could do so I moved onto next project intending to come back when I had more experience. After getting another t401 with a broken case smashed glass but works well I have gone back to the first. The switched volume potentiometer is a 1 meg but must be faulty so I will try to get a replacement. By the way using the good t401 tested all the old valves and all were ok.

30th Sep 2009, 10:48 pm	#4
waspman Retired Dormant Member Join Date: Jul 2009 Location: Poole, Dorset, UK. Posts: 5	Re: ultra t401 help please Success I fitted a V24 standard potentiometer - Log switched - Resistance (Ω): 1M from bowood web site showed no wats or volts for item but nothing to lose so fitted it and hey presto radio working fine. All I need now is case, glass, 2 knobs back and I will have 2 ultra,s The second one is a Ultra ET 4012 so probably a later model. The voltage selector is internal on this model and the station dial is different too.