Bush VHF64 - ECC85 gobbler? - UK Vintage Radio Repair and Restoration Discussion Forum

monoman · 13th Sep 2009, 11:12 am

Hmm, I'm without FM again. AM is OK but I never listen to anything on that. Looks like I'll be on my third ECC85 in 6 months. Anyone else experienced this "luck"?

Brian.

Leon Crampin · 13th Sep 2009, 11:21 am

Not really, but there are plenty of East European and Russian ECC85s around which are not long lived. You could check R1 and its associated decoupler C2 (Bush service sheet numbers) if it's the RF section which is failing.

Finally, change the screening can to a blackened one. This results in a very noticable reduction in valve temperature and helps to reduce frequency drift (although the Bush VHF boxes are not bad in this respect).

Leon.

paulsherwin · 13th Sep 2009, 11:24 am

ECC85s are well known for their short lives, but your experience has been particularly bad.

It would be worth checking that the heater voltage is what it should be.

Paul

Nickthedentist · 13th Sep 2009, 12:11 pm

Quote:

Originally Posted by paulsherwin

It would be worth checking that the heater voltage is what it should be.

and, I suppose, that the mains voltage selector is on the right setting.

Sideband · 13th Sep 2009, 2:37 pm

I've not had a lot of trouble with ECC85's. I'm wondering if the apparent short life is a 'recent' problem. I have several radio's with ECC85's. One is a Stella 160 with all originals...something like 45 years old. Then there is a Fergy 383A with an original and finaly a Baird 301 with an ECC85 that's been in there over 20 years. Admittedly these don't get used every day and probably less than once a month but I seem to remember that our old Fergy 383A that we used to have in the 60's never failed on FM and was still working when we got rid of it.

Leon could be right about Eastern European versions that are not made to the same standard as the originals.

Rich.

paulsherwin · 13th Sep 2009, 2:46 pm

Quote:

Originally Posted by Richard_Newman

I've not had a lot of trouble with ECC85's. I'm wondering if the apparent short life is a 'recent' problem.

Several radios which I've restored have arrived with fairly tired ECC85s and worked much better after these were replaced. These were 60s production Mullard, Telefunken etc. I've no way of knowing how many hours they'd done though, and they did still work after a fashion.

I don't know of a special quality ECC85 variant (there's no E85CC) and wonder if the construction pushed the boundaries somehow. The heater consumption is higher than you'd expect for a twin triode.

Paul

monoman · 13th Sep 2009, 3:44 pm

The one that appears to have failed is branded "Ferranti" so gawd knows where that came from. Got a Mullard on the way and crossed fingers.

Am I correct in thinking that the FM module must be removed from the set in order to access the innards for testing?

Brian.

monoman · 15th Sep 2009, 7:40 pm

With the tested yellow-print Mullard in I have music again. Got a NOS Mullard on the way which I will store behind the set ready for a quick changeover if one should prove necessary in the future. I have left the screening can off for cooler operation.

Thanks for the suggestions & comments chaps.
What lovely sounding sets these are.

Brian.

yestertech · 15th Sep 2009, 10:53 pm

Quote:

Originally Posted by monoman

What lovely sounding sets these are.

Brian.

Here Here ! Especially when you repair the tweeter ! Andy

AC/HL · 16th Sep 2009, 12:56 am

Quote:

Originally Posted by monoman

The one that appears to have failed is branded "Ferranti" so gawd knows where that came from. Brian.

Quite likely Mullard! Manufacturers often made valves for each other, either permanently, or when the need arose.

monoman · 16th Sep 2009, 10:40 am

FWIW here are the two that failed.

I was so glad to have received the Mullard and couldn't get it in the set quick enough so I didn't compare.

G8HQP Dave · 16th Sep 2009, 11:19 am

The Ferranti one looks like it has a Mullard Blackburn factory etch code (B3A) - 1953 manufacture?

The chunky micas with big star edges of the Bentley Acoustic suggest it could be made by RFT in East Germany. The bright red pin seals also suggest Eastern Europe (or Russia but then it would have a sharp end on shiny pins and a dish type getter).

jjl · 16th Sep 2009, 11:48 am

Brian

It would be a good idea to follow Paul and Nick's advice and check that the heater voltage is OK and that the mains voltage selector is correctly set. If a fault of this type exists there is a good chance that you will kill your new ECC85.

John

geofy · 16th Sep 2009, 12:07 pm

Quote:

Originally Posted by monoman

I was so glad to have received the Mullard and couldn't get it in the set quick enough so I didn't compare.

The Mazda 6L12 is equiv and American 6AQ8 and other B719. Are these any more reliable. Could the heater voltage be reduced. What would happen if the heater voltage was reduced to, say, 6v and just who decided on 6.3V instead of just 6 V for E series valves

Geof (a fellow Ongarterian

)

monoman · 16th Sep 2009, 12:51 pm

John, the voltage selector was set at 250V. This was giving HT (measured at the ouput transformer top of primary) of 280VDC and LT (measured at pilot light) of just 4.5VAC! I've reset to 230V and this now gives me 296V HT(spec 300V) and 5.3V LT. Even though the LT was low the pilot lights were bright and the heater glows looked normal. I measure from the pilot light "pip" connection to a point on the chassis since this is the most convenient access. The diagram shows the lights in parallel across the '6.3V' secondary.

Geof, are you still living in Ongar?

Brian.

Nickthedentist · 16th Sep 2009, 1:02 pm

The heater volts seem way out! Are you sure your meter's accurate? What does it read on other sets with E-series valves?

Nick.

Herald1360 · 16th Sep 2009, 1:03 pm

[QUOTE=geofy;271861]

Quote:

Originally Posted by monoman

What would happen if the heater voltage was reduced to, say, 6v and just who decided on 6.3V instead of just 6 V for E series valves

Geof (a fellow Ongarterian

)

Not much, presumably, 6V is only 5% low.

I always wondered whether the 6.3V had anything to do with the typical 6V accumulator discharge voltage (12.6V pro rata for a 12V battery)? This is pretty constant at around 6.3V (12.6V) for a reasonably light load relative to battery capacity.

Chris

monoman · 16th Sep 2009, 1:21 pm

I've swapped meters and still get the same reading. I've also gone underneath the chassis and measured the same low HT at the ECH81 base.

So either there is a shorted turn or two in the transformer 6.3V secondary or something is drawing more current than it should from that secondary.

Oh dear

Brian.

Sideband · 16th Sep 2009, 1:44 pm

Quote:

Originally Posted by monoman

So either there is a shorted turn or two in the transformer 6.3V secondary

Unlikely! It would be getting very hot and smelly by now!!

Rich.

monoman · 16th Sep 2009, 1:51 pm

That's what I thought, which leaves something hogging more current than it should. Maybe the two pilot lights? All the valves apart from the Russian 6P14 replacement for the original EL84 are Mullards.

Update: I've just loosened one of the bulbs so that it is out of circuit. LT is still 5.3V.

13th Sep 2009, 11:12 am	#1
monoman Retired Dormant Member Join Date: Jan 2008 Location: Ongar, Essex, UK. Posts: 74	Bush VHF64 - ECC85 gobbler? Hmm, I'm without FM again. AM is OK but I never listen to anything on that. Looks like I'll be on my third ECC85 in 6 months. Anyone else experienced this "luck"? Brian.

13th Sep 2009, 11:21 am	#2
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Bush VHF64 - ECC85 gobbler? Not really, but there are plenty of East European and Russian ECC85s around which are not long lived. You could check R1 and its associated decoupler C2 (Bush service sheet numbers) if it's the RF section which is failing. Finally, change the screening can to a blackened one. This results in a very noticable reduction in valve temperature and helps to reduce frequency drift (although the Bush VHF boxes are not bad in this respect). Leon.

13th Sep 2009, 11:24 am	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Bush VHF64 - ECC85 gobbler? ECC85s are well known for their short lives, but your experience has been particularly bad. It would be worth checking that the heater voltage is what it should be. Paul

13th Sep 2009, 2:37 pm	#5
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,580	Re: Bush VHF64 - ECC85 gobbler? I've not had a lot of trouble with ECC85's. I'm wondering if the apparent short life is a 'recent' problem. I have several radio's with ECC85's. One is a Stella 160 with all originals...something like 45 years old. Then there is a Fergy 383A with an original and finaly a Baird 301 with an ECC85 that's been in there over 20 years. Admittedly these don't get used every day and probably less than once a month but I seem to remember that our old Fergy 383A that we used to have in the 60's never failed on FM and was still working when we got rid of it. Leon could be right about Eastern European versions that are not made to the same standard as the originals. Rich. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

13th Sep 2009, 3:44 pm	#7
monoman Retired Dormant Member Join Date: Jan 2008 Location: Ongar, Essex, UK. Posts: 74	Re: Bush VHF64 - ECC85 gobbler? The one that appears to have failed is branded "Ferranti" so gawd knows where that came from. Got a Mullard on the way and crossed fingers. Am I correct in thinking that the FM module must be removed from the set in order to access the innards for testing? Brian.

15th Sep 2009, 7:40 pm	#8
monoman Retired Dormant Member Join Date: Jan 2008 Location: Ongar, Essex, UK. Posts: 74	Re: Bush VHF64 - ECC85 gobbler? With the tested yellow-print Mullard in I have music again. Got a NOS Mullard on the way which I will store behind the set ready for a quick changeover if one should prove necessary in the future. I have left the screening can off for cooler operation. Thanks for the suggestions & comments chaps. What lovely sounding sets these are. Brian.

16th Sep 2009, 10:40 am	#11
monoman Retired Dormant Member Join Date: Jan 2008 Location: Ongar, Essex, UK. Posts: 74	Re: Bush VHF64 - ECC85 gobbler? FWIW here are the two that failed. I was so glad to have received the Mullard and couldn't get it in the set quick enough so I didn't compare. Attached Thumbnails Last edited by Station X; 16th Sep 2009 at 10:50 am. Reason: Image converted to thumbnail.

16th Sep 2009, 11:19 am	#12
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: Bush VHF64 - ECC85 gobbler? The Ferranti one looks like it has a Mullard Blackburn factory etch code (B3A) - 1953 manufacture? The chunky micas with big star edges of the Bentley Acoustic suggest it could be made by RFT in East Germany. The bright red pin seals also suggest Eastern Europe (or Russia but then it would have a sharp end on shiny pins and a dish type getter).

16th Sep 2009, 11:48 am	#13
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Bush VHF64 - ECC85 gobbler? Brian It would be a good idea to follow Paul and Nick's advice and check that the heater voltage is OK and that the mains voltage selector is correctly set. If a fault of this type exists there is a good chance that you will kill your new ECC85. John

16th Sep 2009, 12:51 pm	#15
monoman Retired Dormant Member Join Date: Jan 2008 Location: Ongar, Essex, UK. Posts: 74	Re: Bush VHF64 - ECC85 gobbler? John, the voltage selector was set at 250V. This was giving HT (measured at the ouput transformer top of primary) of 280VDC and LT (measured at pilot light) of just 4.5VAC! I've reset to 230V and this now gives me 296V HT(spec 300V) and 5.3V LT. Even though the LT was low the pilot lights were bright and the heater glows looked normal. I measure from the pilot light "pip" connection to a point on the chassis since this is the most convenient access. The diagram shows the lights in parallel across the '6.3V' secondary. Geof, are you still living in Ongar? Brian.

16th Sep 2009, 1:02 pm	#16
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,865	Re: Bush VHF64 - ECC85 gobbler? The heater volts seem way out! Are you sure your meter's accurate? What does it read on other sets with E-series valves? Nick.

16th Sep 2009, 1:21 pm	#18
monoman Retired Dormant Member Join Date: Jan 2008 Location: Ongar, Essex, UK. Posts: 74	Re: Bush VHF64 - ECC85 gobbler? I've swapped meters and still get the same reading. I've also gone underneath the chassis and measured the same low HT at the ECH81 base. So either there is a shorted turn or two in the transformer 6.3V secondary or something is drawing more current than it should from that secondary. Oh dear Brian.

16th Sep 2009, 1:51 pm	#20
monoman Retired Dormant Member Join Date: Jan 2008 Location: Ongar, Essex, UK. Posts: 74	Re: Bush VHF64 - ECC85 gobbler? That's what I thought, which leaves something hogging more current than it should. Maybe the two pilot lights? All the valves apart from the Russian 6P14 replacement for the original EL84 are Mullards. Update: I've just loosened one of the bulbs so that it is out of circuit. LT is still 5.3V. Last edited by monoman; 16th Sep 2009 at 2:03 pm.