Bush VHF 54 radio with no F.M. - UK Vintage Radio Repair and Restoration Discussion Forum

Dick Glennon · 7th Apr 2018, 6:36 pm

I have acquired a lovely Bush VHF 54. It works on all bands except vhf (fm). There is a very healthy click when I change to VHF. As I stream across the band there is changes in volume where our local stations should be but no voice coming through. I have an outdoor FM. Aerial and I wonder if I could use it to increase gain. All suggestions welcome. Dick.

ThePillenwerfer · 7th Apr 2018, 8:32 pm

It's worth checking that the wires haven't come off in the aerial plug. You could also try swapping the two EF80s 'round.

David G4EBT · 7th Apr 2018, 8:58 pm

A good place to start if you don't already have it, would be to download the 17-page Bush data from the Radio Service Data link at the top RH of the page. (NOT the 4-page Trader Sheet #1252). The VHF front end uses two EF80 valves: V1 is the wideband VHF amplifier; V2 is the VHF oscillator/mixer. The ratio detector is the two diodes in V5 (EABC80). Then look at the specified voltages around V1 & V2, on the circuit, and measure what you find around those valves to compare the results with the circuit to see if there are any anomalies such as low anode voltages due to resistors having gone high in value. If you have known good EF80 spare valves, substituting them will either prove that either one or both of the existing valves are duff, or if it makes no difference, will point to problems elsewhere.

As you've got an outside aerial, it makes sense to connect it, because the added gain might show that the set is working, but at faint volume. That could be due to out of spec resistors, valves on their way out, misalignment (especially if their are signs of tampering). If attaching an outside aerial doesn't bring in any signals on VHF, that means they're not finding their way through the RF/IF/Detector stages to the audio stage. Another possibility (if lady luck is shining on you), is open-circuit switch contacts - a squirt of Servisol/Deoxit might cure that.

Bear in mind that the set is over 60 years old, and it's unrealistic to expect to not have to do some in-depth diagnostic checks and probable replacement of out of spec components. Certainly even though the set is working on the AM bands, if not already changed, C56 - the audio coupling cap ought to be changed, and maybe C58 too. You may need to decide if you just want to 'get it going' or do some restoration work on it to keep it going reliably into the future.

Just some initial thoughts to start the ball rolling.

Good luck with it Dick.

Kevin Hoyland · 13th Apr 2018, 6:30 am

Morning Dick.
The email you sent me will not work. I have tested 2 EF80 Valves for you and I will post them ASP. Please have a look at the photo of the VHF top end you will see 3 brown hunts capacitors in There they need to be replaced .

Kevin

Kevin Hoyland · 26th Apr 2018, 12:27 pm

Hello Dick.
Sorry its taken a long time to get back to you. Please see the photos of the under side of the VHF54.
Kevin.

Boater Sam · 26th Apr 2018, 12:54 pm

A Know Fault.

There is a ceramic trimmer in the FM box that goes s/c to ground out the ht to the FM frequency changer valve.
See
https://www.vintage-radio.net/forum/...d.php?t=116281

If you search for "Bush FM trimmer" in the search box you will find many more similar.
Not saying that this is your fault but it is possible.
Sam.

Dick Glennon · 2nd Aug 2018, 2:46 pm

Hi again, I have been looking at the F.M sub-chassis. The capacitors (Hunts) have all been replaced. One of the mica capacitors is reading 6pF instead of 4.7pF. It says plus or minus 20 percent. Would this be OK? Also can I read the voltages on the EF 80's with the valves taken out?

Thanks again, Dick.

ms660 · 2nd Aug 2018, 2:52 pm

Only with fly leads connected otherwise there won't be a lot to read.

I think you might mean measure the voltages on the valve sockets.....You can do that no problem.

Lawrence.

Boater Sam · 2nd Aug 2018, 3:16 pm

I have done several of these, C50 can be duff, be sure to connect it the same way round, and the diodes in the EABC80 can be low emission. They have separate heaters from the triode.
Also bear in mind that on FM the ECH81 acts as the first IF amplifier, I have had some that are happy as the AM frequency changer but get fussy when asked to be an FM IF amp.

My previous about trimmer cap TC1 is a red herring when the FM head is 2 EF80s.

crackle · 2nd Aug 2018, 7:30 pm

Quote:

Originally Posted by Dick Glennon

Hi again, I have been looking at the F.M sub-chassis. The capacitors (Hunts) have all been replaced. One of the mica capacitors is reading 6pF instead of 4.7pF. It says plus or minus 20 percent. Would this be OK?

I wouldn't worry, I would be surprised if your capacitance meter, if it is a DMM type, can read that accurately anyway.

Mike

Sideband · 2nd Aug 2018, 9:16 pm

Quote:

Originally Posted by Dick Glennon

Also can I read the voltages on the EF 80's with the valves taken out?

No...it would tell you nothing. Why would you want to do it anyway? The voltages on the circuit are given with the valves drawing normal current. With the valves out, any reading taken would be meaningless.

Dick Glennon · 2nd Aug 2018, 9:23 pm

Hi again, There is a discharge of some kind on top of L 3 (slightly tacky). It has not spilled down the sides, but it is also at the base of the valve holders. It has remained tacky all this time. It is now brown/black in colour. The adjusting core in L3 is very loose. Regards Dick.

ms660 · 2nd Aug 2018, 9:36 pm

Quote:

Originally Posted by Sideband

Quote:

Originally Posted by Dick Glennon

Also can I read the voltages on the EF 80's with the valves taken out?

Thanks again, Dick.

No...it would tell you nothing. Why would you want to do it anyway? The voltages on the circuit are given with the valves drawing normal current. With the valves out, any reading taken would be meaningless.

Not always....

Lawrence.

Dick Glennon · 7th Aug 2018, 9:21 pm

Hello again, I now have very faint stations coming in on VHF. This is with the lamp limiter and its own Aerial. I have only replaced the resistors in the FM end. Any more advice?

Dick.

7th Apr 2018, 8:32 pm	#2
ThePillenwerfer Octode Join Date: Mar 2011 Location: Sheffield, South Yorkshire, UK. Posts: 1,453	Re: Bush VHF 54 radio with no F.M. It's worth checking that the wires haven't come off in the aerial plug. You could also try swapping the two EF80s 'round. __________________ "Experts are only good at one thing: explaining why something will not work!"

7th Apr 2018, 8:58 pm	#3
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,766	Re: Bush VHF 54 radio with no F.M. A good place to start if you don't already have it, would be to download the 17-page Bush data from the Radio Service Data link at the top RH of the page. (NOT the 4-page Trader Sheet #1252). The VHF front end uses two EF80 valves: V1 is the wideband VHF amplifier; V2 is the VHF oscillator/mixer. The ratio detector is the two diodes in V5 (EABC80). Then look at the specified voltages around V1 & V2, on the circuit, and measure what you find around those valves to compare the results with the circuit to see if there are any anomalies such as low anode voltages due to resistors having gone high in value. If you have known good EF80 spare valves, substituting them will either prove that either one or both of the existing valves are duff, or if it makes no difference, will point to problems elsewhere. As you've got an outside aerial, it makes sense to connect it, because the added gain might show that the set is working, but at faint volume. That could be due to out of spec resistors, valves on their way out, misalignment (especially if their are signs of tampering). If attaching an outside aerial doesn't bring in any signals on VHF, that means they're not finding their way through the RF/IF/Detector stages to the audio stage. Another possibility (if lady luck is shining on you), is open-circuit switch contacts - a squirt of Servisol/Deoxit might cure that. Bear in mind that the set is over 60 years old, and it's unrealistic to expect to not have to do some in-depth diagnostic checks and probable replacement of out of spec components. Certainly even though the set is working on the AM bands, if not already changed, C56 - the audio coupling cap ought to be changed, and maybe C58 too. You may need to decide if you just want to 'get it going' or do some restoration work on it to keep it going reliably into the future. Just some initial thoughts to start the ball rolling. Good luck with it Dick. __________________ David. BVWS Member. G-QRP Club member 1339.

13th Apr 2018, 6:30 am	#4
Kevin Hoyland Heptode Join Date: Feb 2009 Location: Rotherham, South Yorkshire, UK. Posts: 559	Re: Bush VHF 54 radio with no F.M. Morning Dick. The email you sent me will not work. I have tested 2 EF80 Valves for you and I will post them ASP. Please have a look at the photo of the VHF top end you will see 3 brown hunts capacitors in There they need to be replaced . Kevin Attached Thumbnails

26th Apr 2018, 12:27 pm	#5
Kevin Hoyland Heptode Join Date: Feb 2009 Location: Rotherham, South Yorkshire, UK. Posts: 559	Re: Bush VHF 54 radio with no F.M. Hello Dick. Sorry its taken a long time to get back to you. Please see the photos of the under side of the VHF54. Kevin. Attached Thumbnails

26th Apr 2018, 12:54 pm	#6
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Bush VHF 54 radio with no F.M. A Know Fault. There is a ceramic trimmer in the FM box that goes s/c to ground out the ht to the FM frequency changer valve. See https://www.vintage-radio.net/forum/...d.php?t=116281 If you search for "Bush FM trimmer" in the search box you will find many more similar. Not saying that this is your fault but it is possible. Sam.

7th Apr 2018, 6:36 pm	#1
Dick Glennon Hexode Join Date: Oct 2006 Location: Edenderry, Republic of Ireland. Posts: 428	Bush VHF 54 radio with no F.M. I have acquired a lovely Bush VHF 54. It works on all bands except vhf (fm). There is a very healthy click when I change to VHF. As I stream across the band there is changes in volume where our local stations should be but no voice coming through. I have an outdoor FM. Aerial and I wonder if I could use it to increase gain. All suggestions welcome. Dick.

2nd Aug 2018, 2:46 pm	#7
Dick Glennon Hexode Join Date: Oct 2006 Location: Edenderry, Republic of Ireland. Posts: 428	Re: Bush VHF 54 radio with no F.M. Hi again, I have been looking at the F.M sub-chassis. The capacitors (Hunts) have all been replaced. One of the mica capacitors is reading 6pF instead of 4.7pF. It says plus or minus 20 percent. Would this be OK? Also can I read the voltages on the EF 80's with the valves taken out? Thanks again, Dick.

2nd Aug 2018, 2:52 pm	#8
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Bush VHF 54 radio with no F.M. Only with fly leads connected otherwise there won't be a lot to read. I think you might mean measure the voltages on the valve sockets.....You can do that no problem. Lawrence. Last edited by ms660; 2nd Aug 2018 at 3:02 pm.

2nd Aug 2018, 3:16 pm	#9
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Bush VHF 54 radio with no F.M. I have done several of these, C50 can be duff, be sure to connect it the same way round, and the diodes in the EABC80 can be low emission. They have separate heaters from the triode. Also bear in mind that on FM the ECH81 acts as the first IF amplifier, I have had some that are happy as the AM frequency changer but get fussy when asked to be an FM IF amp. My previous about trimmer cap TC1 is a red herring when the FM head is 2 EF80s. Last edited by Boater Sam; 2nd Aug 2018 at 3:19 pm. Reason: added

2nd Aug 2018, 9:23 pm	#12
Dick Glennon Hexode Join Date: Oct 2006 Location: Edenderry, Republic of Ireland. Posts: 428	Re: Bush VHF 54 radio with no F.M. Hi again, There is a discharge of some kind on top of L 3 (slightly tacky). It has not spilled down the sides, but it is also at the base of the valve holders. It has remained tacky all this time. It is now brown/black in colour. The adjusting core in L3 is very loose. Regards Dick.

7th Aug 2018, 9:21 pm	#14
Dick Glennon Hexode Join Date: Oct 2006 Location: Edenderry, Republic of Ireland. Posts: 428	Re: Bush VHF 54 radio with no F.M. Hello again, I now have very faint stations coming in on VHF. This is with the lamp limiter and its own Aerial. I have only replaced the resistors in the FM end. Any more advice? Dick.