Bush vhf70 - UK Vintage Radio Repair and Restoration Discussion Forum

HoraceBatchelor · 29th Oct 2020, 6:09 pm

Hello everyone, for the last couple of weeks I 've been working on a little restoration work on a Bush vhf70, got it looking great, and it really does sound ok. Then just before putting it back in its cabinet, one last job. Change that tatty looking flex. Done, now give it a final trial. The next few sentences have been left out in case I may offend someone. You're right, after sounding fab, it's stopped working. I'm finding it very hard not to "let rip" and tell you what I'm really thinking but for fear of getting banned I wont....

The on off switch is the culprit it seems. Can anyone help me out. With either having one in a drawer somewhere that's going spare, or knowing where I can pick one up. Or maybe advice on any alternative switch that will do the job just as well. I will be much obliged, even if it's only someone showing me some sympathy.

I know I won't be the first to experience this sort of thing and I certainly won't be the last. But why do the gremlins work in this way?

Al (astral highway) · 29th Oct 2020, 6:16 pm

Gremlins ! You’ve got to love them.

Have you tried cleaning the switch contacts with a suitable solvent? Even if it’s enclosed you can usually get something where it’s needed.

And are you sure of the integrity of your connections?

Techman · 29th Oct 2020, 7:11 pm

Probably just one of the pole contacts gone o/c. It may recover if you can get some Servisol 10 switch cleaner into it. Failing that, just have it as a single pole switch and arrange it so that the remaining good pole switches the 'live' only and hard wire the neutral.

You can probably buy a new replacement from one of the usual suppliers.

Nuvistor · 29th Oct 2020, 8:15 pm

Bowood have controls. The manual states it is semi-log, the Bowood ones are log , not sure if it would make any difference worth noting.
https://www.bowood-electronics.co.uk...-log-switched/
Choose the correct value 470k.

Gabe001 · 29th Oct 2020, 9:20 pm

I had a similar problem on a Philco recently and posted the same question. There's usually a small hole at the back. Squirting copious amounts of servisol in the hole and working the switch a few times fixed it for me. Alternatively you could try opening the switch up. There are some good threads on how to get these fixed without having to replace them.

Gabriel

G8UWM-MildMartin · 29th Oct 2020, 10:14 pm

I have had that happen when changing mains leads and it was due to some of the original flux flowing down the hollow rivet from the tags into the switch. Sometimes just reheating the joints while operating the switch frees it off.

HoraceBatchelor · 30th Oct 2020, 10:25 am

Thanks for the advice everyone, much obliged. I'm beginning to think the excessive heat when de-soldering a stubborn connection, as Martin said, as welded things together inside the switch. Ah well, you live and learn.

60 oldjohn · 30th Oct 2020, 12:04 pm

A bit late now but when trying to remove wire from a switch I cut as much of it off as possible including solder with a decent pair of wire cutters. Then apply heat and poke remaining wire out of the hole with a dental pick. This greatly reduces the heat / time taken to a few seconds.

John.

29th Oct 2020, 6:09 pm	#1
HoraceBatchelor Triode Join Date: Mar 2019 Location: Wigan, Lancashire, UK. Posts: 32	Bush vhf70 Hello everyone, for the last couple of weeks I 've been working on a little restoration work on a Bush vhf70, got it looking great, and it really does sound ok. Then just before putting it back in its cabinet, one last job. Change that tatty looking flex. Done, now give it a final trial. The next few sentences have been left out in case I may offend someone. You're right, after sounding fab, it's stopped working. I'm finding it very hard not to "let rip" and tell you what I'm really thinking but for fear of getting banned I wont.... The on off switch is the culprit it seems. Can anyone help me out. With either having one in a drawer somewhere that's going spare, or knowing where I can pick one up. Or maybe advice on any alternative switch that will do the job just as well. I will be much obliged, even if it's only someone showing me some sympathy. I know I won't be the first to experience this sort of thing and I certainly won't be the last. But why do the gremlins work in this way?

29th Oct 2020, 6:16 pm	#2
Al (astral highway) Dekatron Join Date: Nov 2006 Location: London, UK. Posts: 3,496	Re: Bush vhf70 Gremlins ! You’ve got to love them. Have you tried cleaning the switch contacts with a suitable solvent? Even if it’s enclosed you can usually get something where it’s needed. And are you sure of the integrity of your connections? __________________ Al

29th Oct 2020, 7:11 pm	#3
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: Bush vhf70 Probably just one of the pole contacts gone o/c. It may recover if you can get some Servisol 10 switch cleaner into it. Failing that, just have it as a single pole switch and arrange it so that the remaining good pole switches the 'live' only and hard wire the neutral. You can probably buy a new replacement from one of the usual suppliers.

29th Oct 2020, 8:15 pm	#4
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Bush vhf70 Bowood have controls. The manual states it is semi-log, the Bowood ones are log , not sure if it would make any difference worth noting. https://www.bowood-electronics.co.uk...-log-switched/ Choose the correct value 470k. __________________ Frank

29th Oct 2020, 9:20 pm	#5
Gabe001 Octode Join Date: Oct 2019 Location: Stockport, Greater Manchester, UK. Posts: 1,641	Re: Bush vhf70 I had a similar problem on a Philco recently and posted the same question. There's usually a small hole at the back. Squirting copious amounts of servisol in the hole and working the switch a few times fixed it for me. Alternatively you could try opening the switch up. There are some good threads on how to get these fixed without having to replace them. Gabriel

29th Oct 2020, 10:14 pm	#6
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: Bush vhf70 I have had that happen when changing mains leads and it was due to some of the original flux flowing down the hollow rivet from the tags into the switch. Sometimes just reheating the joints while operating the switch frees it off.

30th Oct 2020, 10:25 am	#7
HoraceBatchelor Triode Join Date: Mar 2019 Location: Wigan, Lancashire, UK. Posts: 32	Re: Bush vhf70 Thanks for the advice everyone, much obliged. I'm beginning to think the excessive heat when de-soldering a stubborn connection, as Martin said, as welded things together inside the switch. Ah well, you live and learn.

30th Oct 2020, 12:04 pm	#8
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,987	Re: Bush vhf70 A bit late now but when trying to remove wire from a switch I cut as much of it off as possible including solder with a decent pair of wire cutters. Then apply heat and poke remaining wire out of the hole with a dental pick. This greatly reduces the heat / time taken to a few seconds. John. __________________ My favourite text message "I'll be there in five minutes, if not read again"