BUSH VHF 64 valve info please

[Tom Stone]

Hi all, just bought myself a bit of a tatty Bush VHF64, needs lots of work but all good fun. On opening the back, first thing I saw was a blown valve, had a look but had no marking on it. Can anyone let me know what valve its supposed to be.

Thanks, Tom

[ms660]

EZ81.

Lawrence.

[TonyDuell]

Acording to the service sheet (available 'up top') it's an EZ81. But why do you think it's blown?

[Tom Stone]

the top 5mm is white, not like the rest.

[Tom Stone]

would anyone be able to sell me one, just had a look at my surplus valves and I don’t have one.

[Nuvistor]

Langrex have them if no one in the forum has one.
https://www.langrex.co.uk/?s=Ez81&post_type=product

Looking at the photo the valve doesn’t look white at the top, does it light up, if so the vacuum is good?

[Tom Stone]

Yes, sorry, the photo was lifted from the internet, I didn’t have a camera.

[Tom Stone]

Cant afford that much for the valve, the set only cost me £10. If anyone has a second hand valve please let me know.

Tom

[Nuvistor]

Ok Tom, I don’t have one.

[Ed_Dinning]

Hi Tom, probably pay to check caps etc and use a lamp limiter before powering up with the new valve fitted

Ed

[Herald1360]

Secondhand EZ81s don't fetch a lot less than what Langrex is asking for a new one. £3 odd minimum postage costs don't help either.


The cheapest option would be to go silicon plus ballast resistor but you will need to ensure that all capacitors exposed to direct HT can cope with voltages up to 360V dc which is around what you'll get with high mains before the rest of the set's valves warm up and start to draw current. If that means new smoothing caps and a few others the cost mounts rapidly....


You could bias back the output valve to around half its normal anode current which would allow an EZ80 to cope but they're not a lot cheaper though they are more common secondhand.

[Tractionist]

These are fantastic sets [the best monaural receivers I have ever heard] - soooo .... it's definitely worth spending some time and money on i.e. a full re-cap etc.

You won't regret it .....

[Techman]

I know I can be a bit of a 'skin flint' at times, but replacement parts such as valves, always add up to way more than the radio is ever going to be worth, even when fully working, unless you're very lucky, that's just the name of the game.

You could do exactly as Chris, above, has suggested. I did this with a Bush VHF 61 several years ago when I'd run out of EZ80s. A couple of 1N4007 diodes and a series resistor (very important) on the bottom of the valve base did the job. However, after I'd stocked up with more EZ80s at the following junk sale (I was lucky), I removed the modification and fitted the correct valve.

On a couple of occasions in the very distant past I've found EZ81s 'half waving' and found one or other of the anode pins has broken clean off in the socket. I'm not sure why this is, though I've had a good guess at why, although I've never found this particular fault with the EZ80, which seem to just lose emission and die, or sometimes they flash over, otherwise they're a good reliable valve.

The problem with the EZ81 is that it's an "audiofile" valve which is used in many amplifiers, so the price you've seen is a bargain and you should get it bought if you're serious about radio restoration and repair. However, before you go spending money, it might be worth checking the mains and output transformers for continuity or shorts, as faults with these items, particularly the mains transformer, will render the set scrap.

As said, I was wondering whether you could get away with an EZ80, but again, as said, they're getting very desirable now - I remember the time which doesn't seem so long ago when I was able to pick up used ones on ebay etc. for a couple of quid plus postage - things are changing fast!

[BottleMan]

Originally Posted by Tom Stone

Hi all, just bought myself a bit of a tatty Bush VHF64, needs lots of work but all good fun. On opening the back, first thing I saw was a blown valve, had a look but had no marking on it. Can anyone let me know what valve its supposed to be.

Thanks, Tom

So, you were the one who bought it! I had my eye on this and missed the last few hours of the auction by not being around. It reminded me of my father's Bush RG66 radiogram and I remember how well it performed. Enjoy it. In the meanwhile I'm on the lookout for another one at a bargain price.

Graham

[PaulR]

As built the the VHF 61 is full of Hunts capacitors so I assume that the VHF 64 is the same. They will all need to be changed. I tried diagnosing faults on my VHF 61 and only changing the suspect caps. It lasted a couple of months before more needed to be changed so I would do the whole lot next time.

[dglcomp]

Regarding capacitors and suchlike, here is the inside of my VHF64 for reference, note that this has yet to have any work done to it but does work. There are Hunts branded small capacitors throughout.

[Tractionist]

Yep - from recollection there are something like 25-30 odd caps to change ...... a pain, but it's worth it! Similarly, it's worth stripping and servicing the electrostatic tweeter too. This is a set that I use on a daily basis ..... and it's a cracker!