Advice for a newbie needed

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cressy
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#31 Re: Advice for a newbie needed

Post by cressy »

Dunno, there are a few other 6.3v heater rectifiers that may be more suitable. The 81 was just the one that sprung to mind
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Mike H
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#32 Re: Advice for a newbie needed

Post by Mike H »

No way EZ81, more like GZ34, 5U4G, that sort of ilk. Whose heater is 5V and not insulated. I see Watford Valves have got them. More power, more heat, and as Phil says need an extra 5 Volts AC from somewhere. So two more transformers. 1N4007's much smaller cheaper etc, but YMMV. :D
 
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#33 Re: Advice for a newbie needed

Post by Mike H »

Ali Tait wrote: Sat Apr 22, 2017 8:42 pm Hi Fi Collective is a great supplier for all the bits and bobs you'll need-

https://www.hificollective.co.uk
DO look at the carbon composite resistors, and the ClarityCaps range for the signal coupling capacitors. Preferably wirewound for any high power resistors.
 
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#34 Re: Advice for a newbie needed

Post by shane »

cressy wrote: Sat Apr 22, 2017 11:46 pm Could do a hybrid bridge with a couple of 1n4007 and an ez81 if the 6.3v heater winding for the ecc83 will stand the extra current, will get the soft start that way
Wouldn't a hybrid still need a centre tap on the ht winding? If not, how about Phil's beloved 6d22s?
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#35 Re: Advice for a newbie needed

Post by simon »

Or a pair of 6AX4? A dollar a piece (plus tax and shipping) when I got some a couple of years ago, and there's no top cap to worry about.

In fact I'll send you two if you'd like. Not sure if it's a good idea to run them from the same 6.3V winding as the ECC83s though. Come to think of it I'm sure I have a couple of 12AX7 too I can send.
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#36 Re: Advice for a newbie needed

Post by cressy »

Check out the valve wizard site, its a good place to start and there is a section on hybrid bridges
The earth connection comes from the junction between the 2 diodes rather than the tx, meaning it can be used with a tx without a centre tapped secondary. The 6d22s would do
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#37 Re: Advice for a newbie needed

Post by pre65 »

A pair of 6D22s are nice, but at 1.9A each unit you invariably would need another 6.3v transformer.

The 5v transformer i have is centre tapped, and when I used a 5v full wave rectifier in hybrid bridge mode I used the centre tap to extract the HT.

Just remember not all 5v full wave rectifiers are slow start.
Last edited by pre65 on Sun Apr 23, 2017 12:06 pm, edited 1 time in total.
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#38 Re: Advice for a newbie needed

Post by shane »

I'm working this morning and Matt's bravely volunteered to help my other half scrub the boat clean so I haven't had a chance to talk to him this morning, but I can't help feeling solid state's going to be the best choice.
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#39 Re: Advice for a newbie needed

Post by Mike H »

shane wrote: Sun Apr 23, 2017 6:59 am
cressy wrote: Sat Apr 22, 2017 11:46 pm Could do a hybrid bridge with a couple of 1n4007 and an ez81 if the 6.3v heater winding for the ecc83 will stand the extra current, will get the soft start that way
Wouldn't a hybrid still need a centre tap on the ht winding? If not, how about Phil's beloved 6d22s?
No CT necessary, like this -

.
full-wave.jpg
.
Note a single component bridge rectifier is being used there hence it's plus output is not used, ('NC1')

C1 = reservoir cap.

HTH
 
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#40 Re: Advice for a newbie needed

Post by Nick »

You could use a SS bridge, then a single 6.3v damper diode to give a delayed startup.
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#41 Re: Advice for a newbie needed

Post by pre65 »

Nick wrote: Sun Apr 23, 2017 7:04 pm You could use a SS bridge, then a single 6.3v damper diode to give a delayed startup.
I think I can find a 6D22s to donate to the project, not sure about a top cap though.
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#42 Re: Advice for a newbie needed

Post by andrew Ivimey »

For 6D22s you'll need the right valve sockets too.
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#43 Re: Advice for a newbie needed

Post by Mike H »

Need four, 2 x monoblocks. (?)

Nick wrote: Sun Apr 23, 2017 7:04 pm You could use a SS bridge, then a single 6.3v damper diode to give a delayed startup.
Of course, you're a genius :D


Soft-start is nice but not absolutely necessary if the HT caps can take 500V. Bearing in mind this is a first timer's build, I think. Bit overly complicated?
 
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#44 Re: Advice for a newbie needed

Post by shane »

Brushing the dust off this now summer’s over I’m looking at the power supply again. Definitely going solid state as we don’t have 5v windings or enough extra 6.3v current capacity to heat a rectifier valve.

I was just looking at the amp circuit Mike suggested
to try to work out current draw http://www.sarris.info/main/files/Push- ... atic-1.png

The 6550 cathode resistors are 270r, and the voltage given is 220mv, which implies a current of about 1mA. Is that right? Seems mighty low to me...
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#45 Re: Advice for a newbie needed

Post by IslandPink »

The 220mV doesn't make much sense to me either. More like 60V or more ( I haven't checked the 6550 datasheet in any detail ) . Not sure what the idle current would be on this, is it class AB ?
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