Bush VTR103 unstable and quiet - UK Vintage Radio Repair and Restoration Discussion Forum

stevekendal · 9th Nov 2020, 1:14 am

As found, it works on FM, but really quiet.
AM is really unstable, especially Medium Wave.
Tapping the AF transistors doesnt provoke any extra noises or improvements. Any thoughts please?

AC/HL · 9th Nov 2020, 1:17 am

Is this a VTR103?

stevekendal · 9th Nov 2020, 1:36 am

Yes

Cobaltblue · 9th Nov 2020, 9:08 am

Title updated.

Cheers Mike T

coopzone · 9th Nov 2020, 1:59 pm

What sort of unstable? Suddenly make a noise, has a low rumble all the time. Drifts of channel? Try to cut the problem in half if you can. By that i mean if you have an audio amplifier of some sort (i use a cheapo lm386 board of ebay) connect it to the volume control and see if the problem is now through the amp, if so you now know it's not the audio section.

Also if the problem with unstable vanishes on VHF, just Quiet then it's more likely to be an IF problem or mechanical switch issue, it's always worth cleaning the switches very well.

I would also be inclined to replace the electrolytes - especially the ones around the audio output. i can't recall of hand but i think there is a 200uf in the final output stage, if thats duff the audio will be low and sometimes distorted.

tim.norris · 13th Nov 2020, 3:46 pm

Hi, These are quite complex for their time , there are 3 dreaded AF117 transistors and the LW/MW mixer/oscillator also acts as the first IF amplifier on VHF . I would zap/swop the af117s as a matter of course , you can fit the AF 12..... series but they are fiddly due to the shorter legs ! . The VHF tuner inside the metal can has an AF114 RF amp and an AF115 self oscillating mixer these are a pain to swop you will need hands like a midwife ,though if these fail there`s usually no FM at all. I also swop the red and yellow plesseys on sight , there`s one under the speaker on the rear as well, you can hollow them out and fit new inside on the ones that show . FM performance is ok but not earth shattering even when working ok . be careful cleaning the rotary wave change switch its very fickle and easily damaged. Is yours the brown or rarer blue rexine version ? Hope this helps , Tim

9th Nov 2020, 1:14 am	#1
stevekendal Heptode Join Date: Mar 2004 Location: Kendal, Cumbria, UK. Posts: 625	Bush VTR103 unstable and quiet As found, it works on FM, but really quiet. AM is really unstable, especially Medium Wave. Tapping the AF transistors doesnt provoke any extra noises or improvements. Any thoughts please? __________________ Knobs and tubes rule ok

9th Nov 2020, 1:17 am	#2
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Bush TR103 unstable and quiet Is this a VTR103?

9th Nov 2020, 1:36 am	#3
stevekendal Heptode Join Date: Mar 2004 Location: Kendal, Cumbria, UK. Posts: 625	Re: Bush TR103 unstable and quiet Yes __________________ Knobs and tubes rule ok

9th Nov 2020, 9:08 am	#4
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,874	Re: Bush VTR103 unstable and quiet Title updated. Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

9th Nov 2020, 1:59 pm	#5
coopzone Hexode Join Date: Jan 2018 Location: Cannock, Staffordshire, UK. Posts: 268	Re: Bush VTR103 unstable and quiet What sort of unstable? Suddenly make a noise, has a low rumble all the time. Drifts of channel? Try to cut the problem in half if you can. By that i mean if you have an audio amplifier of some sort (i use a cheapo lm386 board of ebay) connect it to the volume control and see if the problem is now through the amp, if so you now know it's not the audio section. Also if the problem with unstable vanishes on VHF, just Quiet then it's more likely to be an IF problem or mechanical switch issue, it's always worth cleaning the switches very well. I would also be inclined to replace the electrolytes - especially the ones around the audio output. i can't recall of hand but i think there is a 200uf in the final output stage, if thats duff the audio will be low and sometimes distorted.

13th Nov 2020, 3:46 pm	#6
tim.norris Hexode Join Date: Feb 2012 Location: Blackburn, Lancashire, UK. Posts: 282	Re: Bush VTR103 unstable and quiet Hi, These are quite complex for their time , there are 3 dreaded AF117 transistors and the LW/MW mixer/oscillator also acts as the first IF amplifier on VHF . I would zap/swop the af117s as a matter of course , you can fit the AF 12..... series but they are fiddly due to the shorter legs ! . The VHF tuner inside the metal can has an AF114 RF amp and an AF115 self oscillating mixer these are a pain to swop you will need hands like a midwife ,though if these fail there`s usually no FM at all. I also swop the red and yellow plesseys on sight , there`s one under the speaker on the rear as well, you can hollow them out and fit new inside on the ones that show . FM performance is ok but not earth shattering even when working ok . be careful cleaning the rotary wave change switch its very fickle and easily damaged. Is yours the brown or rarer blue rexine version ? Hope this helps , Tim