Wanted: Sexy-Looking Balloon Rectifier

[Mr Kipling]

I'm looking for one for an ECL86 design. I'd like a balloon type that isn't expensive.

If anyone knows where I may get one (two actually), I'd be very grateful.

Thanks.

[BTH K10A]

I would suggest you look for a U12 as the early versions were balloon shaped. The do come up on ebay fairly regularly but tend to be sought after.

They are also near equivalents of FW4-250, UU5 & U14 rectifiers which could be used in the interim untill you find a good balloon pair

http://www.r-type.org/exhib/aaa0787.htm

[Jonboy]

Thats the one i was thinking of, i think it can replace a GZ 32 or GZ 34 but you need to check

[Mr Kipling]

Thanks Andy and Jon. And thanks for the link, Andy.

I've had a look at the U12 but it doesn't look very sexy! I want to get my hands on a nicely-shaped pair. Something like the GZ32/33/37. Perhaps these are described as bottle-shaped? There's a pair of Mullard '33s on Ebay for £200!

I'm wanting them for the amp I recently got, which you were watching, Jon. I'm still scratching my head with it. After unpacking it I thought it was an OTL design with an EL34 output. What looked like a driver valve was missing on each channel. Looking closer and inside, I found output transformers and that it was a push-pull ECL86 design with the missing valves being the other ECL86s.

What has me puzzled is what the EL34s are doing as all they are connected to is the heater supply. The two large capacitors at the back have a value of 2,500uF 50V and aren't connectted to anything! The heater supply is AC so I don't know what their purpose is /was either. The HT line is fed from a bridge rectifier and I thought of using valve types to fill the spaces left by the EL34.

Even the feet are odd, being constructed using tyres from a Tomy truck. Unusual.

[Ali Tait]

Do you mean this kind of shape?

http://www.ebay.com/itm/Here-are-2-S...item1e75bab64f

If so, that's called the ST shape.

A balloon shape is this-

http://www.ebay.com/itm/2-145-245-45...item2c6b0311a5

[Mr Kipling]

Thanks Ali T. Yes it's the ST shape I'm meaning. So it's rectifier with a heater voltage and current rating of 6.3V and 1.5A is what it needs to be.

[Ali Tait]

You'll struggle. An EZ81 runs on 6.3v, but it looks like an EL84. Most of the usual suspects GZ34/7, 5u4g etc. work on 5v.

[BTH K10A]

Thanks Ali T. Yes it's the ST shape I'm meaning. So it's rectifier with a heater voltage and current rating of 6.3V and 1.5A is what it needs to be.

There aren't many rectifiers that have a 6.3v heater. The EZ80 & EZ81 are but you won't find an ST shape one.

[Mr Kipling]

The power transformer does have another tapping unused, but I don't have a working meter to test it right now.

Do you never get DC heater supplies in power amps?

[Ali Tait]

Yes, if you want to heat the valves with dc.