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  #21  
Old 30th November 2006, 09:13 PM
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Default Re: Amp-from-a box-of-bits?

If that is the voltage from, the TX. then it would have to be a bridge, unless anyone has other thoughts?
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  #22  
Old 1st December 2006, 09:45 AM
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Default Re: Amp-from-a box-of-bits?

Quote:
Originally Posted by NickG
If that is the voltage from, the TX. then it would have to be a bridge, unless anyone has other thoughts?
Yes it is, connected as per diagram 'B'? I'm lacking a nice big inductor at present, I'll have to womble through some old equipment maybe?

The box I've been given contains the following...

PC900 (2 off)
PC86
PC88

PCC189

PCL84 (3 off)
PCL82 (2 off)
PCL86
PCL805(3 off)

PFL200 (5 off)

PL36
PL81

PY81
PY800 (2 off)
PY80
PY88

EF85 (3 off)
EF80 (7 off)
EF184 (3 off)
EF183 (3 off)
EF41

KT88 GEC Brand

6L6GC (2 off) diff. brands

EH90

EB9
EB91

EY86

ECC82

ECL80


PCF80 (5 off)
PCF801 (2 off)
PCF802 (3 off)

DY86/87
DY87
DY802

CV287

5Z4

+ a few others but the brands and type have been rubbed/fallen off and can't quite make out for sure.

Any suitable drivers there Nick?

DTB
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  #23  
Old 1st December 2006, 12:24 PM
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Default Re: Amp-from-a box-of-bits?

Yes, many options, most of the EF's. Or you could just use the ECL/PCL on their own.
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  #24  
Old 1st December 2006, 02:49 PM
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Default Re: Amp-from-a box-of-bits?

Quote:
Originally Posted by NickG
Yes, many options, most of the EF's. Or you could just use the ECL/PCL on their own.
Wahey!

Seeing as this is my first build from scatch project lets go the simplest route, I'm guesssing from what you're saying Nick that ECL/PCL are driver and output in one envelope just like the Valve used in the HD83?

OK, pick one for me that I can use with that 2000 ohm Xfmr and I'll even invest in a valve base for it. Big bucks this malarky!


I PROMISE not to put it in a box and will leave it looking messy.

DTB
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  #25  
Old 2nd December 2006, 01:40 PM
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Default Re: Amp-from-a box-of-bits?

Ok, how about (as a untried idea, so it all could go wrong).

uise the PCL86. The power supply could be the 0-370v tap of the transformer, into a bridge, then a 110u cap made from two 220u caps in series 385v rating should be ok, both with a 220k in parallel as broppers and voltage equalisers. Then a 2k 12W resistor (will get hot) to another pair of stacked 220u caps, with resistors. On load this should give something like 420v.

Ok, then the triode in the 86, with 1k resistor on its cathode, and 470u bipass, maybe there will be enough gain to try it unbipassed. Anode resistor 270k 2W. That should give about 150v on its anode, and 1ma current. Tie its grid to ground via a 1M resistor, and input signal goes across that resistor.

Then the pentode, is used triode strapped, with g2 connected to the anode. g1 of the pentode connected directly to the anode of the triode. Then the anode via the output transformer to the 420v B+. 2k is a bit low, but it will be ok for this. Then stand the cathode on a 5k6 12W resistor, with 220u 200v bipass.

Finally the heater supply for the PCL86, is the 6.2 and 3.7-0-3.7 all in series to hopefully give 13.6v.

It may work, it may not. Any other opinions folks?
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  #26  
Old 4th December 2006, 11:28 AM
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Default Re: Amp-from-a box-of-bits?

Many thanks for that NickG,

I'll draw that up over lunch to make sure I've got all that right.

Cheers for all your help as ever.

DTB
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  #27  
Old 11th December 2006, 01:55 PM
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Default Re: Amp-from-a box-of-bits?

http://www.dartfordskatepark.co.uk/daves/circuit.jpg

NickG, can you have a look at that link and see if I've drawn it out correctly?

Sorry about the lack of progress up to now, work got in the way of play-time. boo!

I've had the heaters up and running, the PCL flashed a little when I first powered it up (hasn't been 'excited' in at least 20 years I'm told) but seems happily glowing now.

DTB
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  #28  
Old 11th December 2006, 06:39 PM
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Default Re: Amp-from-a box-of-bits?

The first triode anode resistor needs to go to B+, not the next triodes anode.

I repeat, I make no promise that this will work :-)
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  #29  
Old 12th December 2006, 03:07 PM
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Default Re: Amp-from-a box-of-bits?

Quote:
Originally Posted by NickG
The first triode anode resistor needs to go to B+, not the next triodes anode.
Doh! I thought I had, I've recheck my (poor) drawing and I'v got it connected to B+ via the primary of the O/P Xfmr, is that not right? Also I'm not sure what to do with the other Grid connection, a pentode has 3 doesn't it, I realised I'd only drawn in 2!!! See, I told I'm new to this


Quote:
Originally Posted by NickG
I repeat, I make no promise that this will work :-)
Thats understood Nick, this is just to help me learn a little about Valves using crud from a box. I'm not expecting great 'things' from it!!! I appreciate your help so far.

DTB
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  #30  
Old 12th December 2006, 05:48 PM
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Default Re: Amp-from-a box-of-bits?

This pentode is internally connected g3 is connected to the cathode so it is taken care of for you.

Grid 2 pin 8 is connected to the anode via a 100 ohm resistor.
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