UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 30th Jan 2006, 1:48 pm   #1
kevinb
Pentode
 
kevinb's Avatar
 
Join Date: Dec 2005
Location: Leicestershire, UK.
Posts: 208
Default Bush FM motorboating.

My Bush VHF54 works ok on AM but on FM it motorboats if you turn volume up. I have tried all valves and previous suggestions, any help would be appreciated.

Last edited by Darren-UK; 12th Jul 2007 at 12:53 am. Reason: General tidying.
kevinb is offline  
Old 30th Jan 2006, 1:52 pm   #2
Hunts smoothing bomb
Octode
 
Hunts smoothing bomb's Avatar
 
Join Date: Oct 2005
Location: Wimborne, Dorset, UK.
Posts: 1,352
Default Re: Bush VHF54 FM Problems

Hi,

I had a set that did this and I changed the caps in the FM section around the UCC85/ECC85, also the small value electrolytic in the FM discriminator circuit and the set plays very well to this day.

Regards
Lee
__________________
Lee
Hunts smoothing bomb is offline  
Old 12th Feb 2006, 11:37 pm   #3
twynham
Diode
 
twynham's Avatar
 
Join Date: Sep 2005
Location: Cheshire
Posts: 5
Question Re: Bush VHF54 FM Problems

I've just fixed my one tonight... Wasn't getting anything on FM either, other than some rude noises and the TI blowing its top from the 25v+ being delivered by the EABC80.

Had already replaced the FM Electrolytic. Then bit the bullet and completely rebuilt the FM front end last night to no particular avail.

Tonight, replaced decoupling caps C39, C40, and C41 around the IF amp (V4). Absolute sods to get to. Complete change of personality. Radio 4 now coming in *loud and clear* with 2ft piece of wire stuck in the RF input.

I guess the IF was unstable at the higher frequency.

Twynham 3, Hunts 0.

Good luck!!
__________________
--
Stewart Twynham
twynham is offline  
Old 20th Feb 2006, 10:29 pm   #4
TimS
Pentode
 
TimS's Avatar
 
Join Date: Jun 2005
Location: Edinbane, Isle of Skye, UK.
Posts: 180
Default Re: Bush VHF54 FM Problems

Is "motorboating" a "put.....put.....put...." sound?

I'm getting something like that on my VHF61 (FM only, and it doesn't start until a few moments after VHF is selected).

Is the VHF54 similar to the VHF61?

-- Tim.
TimS is offline  
Old 26th Feb 2006, 3:05 pm   #5
Jim - G4MEZ
Tetrode
 
Jim - G4MEZ's Avatar
 
Join Date: Feb 2006
Location: Newport Pagnell, Buckinghamshire, UK.
Posts: 85
Default Re: Bush VHF54 FM Problems

I have the same problem on my VHF64. +27V across the discriminator reservoir etc. I found that if the VHF and MW (or LW but not SW) keys are held down simultaneously it bursts into life on VHF. As far as I can see, doing this removes the 27V of VHF AGC from the second IF amp and tames it down a bit, perhaps stopping it from taking off.

Not sure if you can play the same trick on other Bush VHF series as an aid to fault-finding but loading down the anodes of the IF Amps with a highish value resistor (or even an AVO) will damp it down.

I'm off to change all the decouplers around the IF stages and see if it cures it.

Jim
Jim - G4MEZ is offline  
Old 6th Mar 2006, 7:44 pm   #6
PaulR
Octode
 
PaulR's Avatar
 
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 1,975
Default Re: Bush VHF54 FM Problems

Get rid of all those Hunts caps - you know it makes sense!! My VHF 61 works a treat now they have all gone!

Paul
PaulR is online now  
Old 6th Mar 2006, 7:50 pm   #7
Jim - G4MEZ
Tetrode
 
Jim - G4MEZ's Avatar
 
Join Date: Feb 2006
Location: Newport Pagnell, Buckinghamshire, UK.
Posts: 85
Default Re: Bush VHF54 FM Problems

Quote:
Originally Posted by PaulR
Get rid of all those Hunts caps - you know it makes sense!! My VHF 61 works a treat now they have all gone!

Paul
Seconded. In my VHF64 I found all the anode and screen decouplers on the Mixer/1st FM IF and the two IF stages either O/C or a few pF.

It may be my imagination but the brown Hunts seem worse than the black ones. It seems too that a Hunts that has an easy life (e.g. decoupling the heater chain or AGC line) seem to live forever. Those running close to their rated voltage seem to die quickest. Again, it may be my imagination..

Jim
Jim - G4MEZ is offline  
Old 6th Mar 2006, 10:45 pm   #8
Paul Stenning
Administrator
 
Paul Stenning's Avatar
 
Join Date: Dec 2002
Location: Cardiff
Posts: 7,287
Default Re: Bush VHF54 FM Problems

Thirded, from dealing with several Bush VHFxx sets (in particular the VHF61 and VHF80).
__________________

Paul Stenning
Forum Admin/Owner and BVWS Committee Member
Paul Stenning is offline  
Old 7th Mar 2006, 5:05 pm   #9
jay_oldstuff
Octode
 
jay_oldstuff's Avatar
 
Join Date: Jan 2005
Location: Hyde, Greater Manchester, UK.
Posts: 1,074
Default Re: Bush VHF54 FM Problems

It's all my VHF54 needed to bring FM crashing back in be warned though some are a swine to get at

These sets do sound good on FM when working so its worth persevering with.

Jay

Last edited by Darren-UK; 12th Jul 2007 at 12:51 am. Reason: General tidying.
jay_oldstuff is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 10:22 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.