Bush VHF 64 - UK Vintage Radio Repair and Restoration Discussion Forum

ian rose · 24th Apr 2021, 9:44 am

Hello all
In my example of the above set the electrostatic tweeter is offering only very low level audio. HT voltage is as spec and earthing is good.
My question is; what value of capacitance should the speaker be when disconnected and up to spec?
Regards
Ian Rose

G6ONEDave · 24th Apr 2021, 10:39 am

If the tweeter is OK then possibly R34 has gone high or C64/C67 have become leaky and are causing the tx primary to effect the response by acting as a parallel resistance across the tweeter.

Dave

Leon Crampin · 24th Apr 2021, 12:38 pm

Carefully dismantle the tweeter. The foam will be rotten, leading to a loss of preload on the contacts, which may also be tarnished. A Forum search will provide useful information.

Leon.

mark pirate · 24th Apr 2021, 3:12 pm

These Grundig tweeters suffer from foam rot, as Leon has said, it will require disassembly to replace the foam & clean the contacts.
I have not done one for a few years, but I don't think it was too difficult.

Mark

ian rose · 25th Apr 2021, 11:56 am

Thank you Leon, Mark and Dave.
Will inspect foam as you suggest.
Regards
Ian Rose

Edward Huggins · 25th Apr 2021, 1:07 pm

If you can't fix it, don't mess about with this, as these can sound very harsh.
Fit a nice 3" cone tweeter via 2.2uf cap in the same baffle cut opening.
It will sound really sweet.

ian rose · 25th Apr 2021, 5:44 pm

Thanks Edward --- good idea
Ian

MurphyNut · 26th Apr 2021, 12:23 pm

If the electrostatic tweeter is the same one used on the Bush record players of the time the link below shows how to repair them, it's very comprehensive.

https://www.vintage-radio.net/forum/...d.php?t=174153

Tractionist · 29th Apr 2021, 12:25 am

This is a very 'quiet' tweeter - but Leon is quite right ... they are pretty easy to service.

24th Apr 2021, 9:44 am	#1
ian rose Pentode Join Date: Aug 2010 Location: Isle of Wight, UK. Posts: 224	Bush VHF 64 Hello all In my example of the above set the electrostatic tweeter is offering only very low level audio. HT voltage is as spec and earthing is good. My question is; what value of capacitance should the speaker be when disconnected and up to spec? Regards Ian Rose

24th Apr 2021, 10:39 am	#2
G6ONEDave Octode Join Date: Dec 2019 Location: Owston Ferry, North Lincolnshire, UK. Posts: 1,701	Re: Bush VHF 64 If the tweeter is OK then possibly R34 has gone high or C64/C67 have become leaky and are causing the tx primary to effect the response by acting as a parallel resistance across the tweeter. Dave __________________ Quote "All is hyperthetical, until it isn't!" (President Laura Roslin, Battlestar Galactica)

24th Apr 2021, 12:38 pm	#3
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,870	Re: Bush VHF 64 Carefully dismantle the tweeter. The foam will be rotten, leading to a loss of preload on the contacts, which may also be tarnished. A Forum search will provide useful information. Leon.

24th Apr 2021, 3:12 pm	#4
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Bush VHF 64 These Grundig tweeters suffer from foam rot, as Leon has said, it will require disassembly to replace the foam & clean the contacts. I have not done one for a few years, but I don't think it was too difficult. Mark

25th Apr 2021, 11:56 am	#5
ian rose Pentode Join Date: Aug 2010 Location: Isle of Wight, UK. Posts: 224	Re: Bush VHF 64 Thank you Leon, Mark and Dave. Will inspect foam as you suggest. Regards Ian Rose

25th Apr 2021, 1:07 pm	#6
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,327	Re: Bush VHF 64 If you can't fix it, don't mess about with this, as these can sound very harsh. Fit a nice 3" cone tweeter via 2.2uf cap in the same baffle cut opening. It will sound really sweet. __________________ Edward.

25th Apr 2021, 5:44 pm	#7
ian rose Pentode Join Date: Aug 2010 Location: Isle of Wight, UK. Posts: 224	Re: Bush VHF 64 Thanks Edward --- good idea Ian

26th Apr 2021, 12:23 pm	#8
MurphyNut Heptode Join Date: Apr 2016 Location: Croxley Green, Hertfordshire, UK. Posts: 979	Re: Bush VHF 64 If the electrostatic tweeter is the same one used on the Bush record players of the time the link below shows how to repair them, it's very comprehensive. https://www.vintage-radio.net/forum/...d.php?t=174153 __________________ Clive

29th Apr 2021, 12:25 am	#9
Tractionist Heptode Join Date: Apr 2016 Location: Cheltenham, Gloucestershire, UK. Posts: 875	Re: Bush VHF 64 This is a very 'quiet' tweeter - but Leon is quite right ... they are pretty easy to service. __________________ Red to red, black to black. Throw the switch and stand well back!