OK, did some measurements...
At turn on the autobias pulls the grids down to -70V and it stays there for 45 seconds. After that the voltage on the grids slowly -over a few minutes- goes up to around -18V where it stabilizes.
15 seconds after the preamp is turned on the +B voltage comes on and ramps up during seconds.
30 seconds after the preamp is turned on the heater voltage is at 2,3V and I see the heaters glowing. It takes another minute or so before the voltage is at 2,5V.
So basically the autobias pulls down the grid longer than it takes for the heater voltage to come on, so I guess all is good..!?
Hi,
The old 2004 circuit uses transistors that are now unavailable. (But 2ST1480 was never used).
The Regulator that DIYers in this thread are enjoying, is a new design - a different circuit. The performance of this new circuit is much higher, and it's easier to use. It's available as a self-assembly kit, DIY-friendly price. Please send me your email address, if you would like some information!
The old 2004 circuit uses transistors that are now unavailable. (But 2ST1480 was never used).
The Regulator that DIYers in this thread are enjoying, is a new design - a different circuit. The performance of this new circuit is much higher, and it's easier to use. It's available as a self-assembly kit, DIY-friendly price. Please send me your email address, if you would like some information!
Hi all,
I just received my regulator kits from Rod ( Thanks Rod! )
and am looking at what kind of capacitors to order.
Is it reasonable to assume that if I stick to for instance Nichicon or Panasonic
that looking at ripple current and load life will give some "safe" alternatives?
What else do I need to look for?
cheers
Jan
I just received my regulator kits from Rod ( Thanks Rod! )
and am looking at what kind of capacitors to order.
Is it reasonable to assume that if I stick to for instance Nichicon or Panasonic
that looking at ripple current and load life will give some "safe" alternatives?
What else do I need to look for?
cheers
Jan
Jan, there's some known-good caps for the rectified dc.
Panasonic TSUP is very dependable: the 1000uF/35V can be used in all cases: Farnell stock code 1198717
ECOS1VP103CA - PANASONIC - CAPACITOR, 10000UF, 35V | Farnell Norge
High ripple current handling is the most important data sheet point.
Enjoy the DHT upgrade!
Panasonic TSUP is very dependable: the 1000uF/35V can be used in all cases: Farnell stock code 1198717
ECOS1VP103CA - PANASONIC - CAPACITOR, 10000UF, 35V | Farnell Norge
High ripple current handling is the most important data sheet point.
Enjoy the DHT upgrade!
This is what I would call a comprehensive customer support!
I'm in the process of building a power supply for the Coleman heaters too so this info is welcome
I'm in the process of building a power supply for the Coleman heaters too so this info is welcome
I should mention as well, that if your raw dc supply is below 16V, there's an excellent bargain cap available at the moment: Farnell 1839273 is an EPCOS 10000uF/16V that can support 3,3A of ripple:
B41231A4109M000 - EPCOS - CAPACITOR, SNAP-IN, 16V, 10000UF | Farnell Norge
very low cost for a high quality snap-in. Ideal for 300B, 26 and similar power filaments.
B41231A4109M000 - EPCOS - CAPACITOR, SNAP-IN, 16V, 10000UF | Farnell Norge
very low cost for a high quality snap-in. Ideal for 300B, 26 and similar power filaments.
I thought I'd piggy back this thread to say thanks to Rod for the heater supplies. They work a treat. I havn't been able to comment on the sound yet as the 2 x 0-9v transformer I had in the bit box sounds like a pneumatic drill so I'm in the process of swapping it out for a toroid. It's difficult to appraise the silence with all that buzzing.
Anyway with all the talk of delayed HT I thought I'd mention this anyway:
Vitalstates - SV572
Ed
Anyway with all the talk of delayed HT I thought I'd mention this anyway:
Vitalstates - SV572
Ed
Assuming I use 2 Rod Coleman's regulators for 2 DHT output triodes. Do I need
a) separate xformer windings + rectifier bridges + some C filters for each triode or
b) one winding and separate rectifier bridges + C filters for each triode?
I am afraid that in case b) there will be crosstalk between cathodes. Am I right?
a) separate xformer windings + rectifier bridges + some C filters for each triode or
b) one winding and separate rectifier bridges + C filters for each triode?
I am afraid that in case b) there will be crosstalk between cathodes. Am I right?
Hi, Yes, There is a risk of crosstalk, you are right. Please use separate transformer winding and rectifiers for each DHT.
For the best possible solution, a separate transformer is recommended - if the transformer is shared, cross-coupling of rectifier current pulses can increase the overall noise.
Hi Ed, Thank you for your kind comments!
when searching for a Filament transformer, please be careful with the quality and construction. There is a big variation of leakage capacitance between primary and secondary windings, and we need the lowest possible value here, to prevent (usually common-mode) noise entry.
Toroidal trafos are not the best performers, sad to say. The capacitance of these may be as high as 1nF, and often the core can't be grounded.
Dual-bobbin [aka split-bobbin] EI types are much better, and I measure 30 to 50pF using Industrial Control-Panel transformers from the UK supplier JMS
1 PH Trans
Most countries have a local maker of industrial trafos, and their customers also like split-bobbin construction, because of better isolation (breakdown) quality. In Italia, the equivalent company is Ideomat Italia Srl, at Modena. I am sure that there are many others.
The other reliable supply of dual-bobbin EI is from Hammond: the 266 series.
Hammond Mfg. - Power Transformer - Dual Primary / Dual Secondary (266 Series)
Regardless of the heating method (or Regulator), the transformer is important quality for filament heating, please choose carefully!
Thanks Rod. As I have little room for next xftmr, I will use existing 2 separate 6.3V (*230/220) 3A windings and voltage doublers instead of rectifier bridges.
A doubler should give good results!
The attached PSUD file uses 6,3V 3A trafo to generate 11V - enough for 6B4G. The rms current in the trafo secondary is 3A.
With a 6,3Vrms 4A trafo, we can generate 10,5V dc using a similar circuit, and feed a 300B regulator.
Attachments
Hi,
What about toroidal trafos with a grounded electrostatic shield between the primary and the secondary?
These high quality trafos should work very well - they are designed to tackle the weakness of the standard consumer-quality toroidal: with the cheap toroids, the common-mode noise is very bad.
The measurement that really matters: effective capacitance from primary to secondary.
Glad to hear that!
Actually it is 6,58Vrms, as it was built for 220V primary. Now in PL mains voltage is 230V, thus 6,3V*1,045