Hi, the part list are all the same as the original board stated except the transformer that is a 25VA 24Vx2 Triad and capacitor that are 6800mF.
Yes loaded with the regulator it deliver 26Vdc but only two of the leds on the back are lighted.
Sorry iti is not clean like yours but I'm just testing it.
What value is the last series resistor in your pre-reg?
Sounds a bit like there is some kind of trouble with the CCS/regulator part to me.. but i haven't had this trouble so i don't really know.. i think i read somebody else a long time ago in this thread that also had trouble with exactly those leds, so you could maybe search and see if you find it..
I'm also using 2x24VAC transformers, but Selectronic R-core (30VA) instead of the default ones, because i had trouble with hum on all eight i tried.
Sounds a bit like there is some kind of trouble with the CCS/regulator part to me.. but i haven't had this trouble so i don't really know.. i think i read somebody else a long time ago in this thread that also had trouble with exactly those leds, so you could maybe search and see if you find it..
I'm also using 2x24VAC transformers, but Selectronic R-core (30VA) instead of the default ones, because i had trouble with hum on all eight i tried.
Ok, that's an issue with the shunt reg, your psu boards are fine.
Which revision of the main boards do you have? R1, R2, R3, R3b ?
Which revision of the main boards do you have? R1, R2, R3, R3b ?
37Vac unloaded dropping to 26Vac loaded is an enormous drop.
if the load is taking the transformer to it's full rated output then those two voltages indicate a transformer regulation of 39.6% (37Vac/26.5Vac= 1.396)
That is higher regulation than I have ever measured on very small transformers. 30% is common on 3VA transformers.
I would expect <20% on a 30VA transformer, and dropping to ~6% on a 200VA transformer.
AndrewT: If you re-read; the regs measures 37VDC on output when there is no load on them.. not 37VAC input from transformer.
to make it clear:
the main board are rev.2
output transformer is always 26Vac
output pre-regulator is 36Vdc unloaded
output pre-regulator is 21Vdc if loaded with just the regulator
the Hammond 158T is rated as 40R and I have a drop of 5V the last resistance in the clrc net is 47R 20W and I have a drop of 5V on it
the regulator is absorbing 127mA. can anyone confirm this is a correct value?
the main board are rev.2
output transformer is always 26Vac
output pre-regulator is 36Vdc unloaded
output pre-regulator is 21Vdc if loaded with just the regulator
the Hammond 158T is rated as 40R and I have a drop of 5V the last resistance in the clrc net is 47R 20W and I have a drop of 5V on it
the regulator is absorbing 127mA. can anyone confirm this is a correct value?
Then the last resistor (47R) is your problem.... originally in the design those were 10R.. on my boards i even dropped it down to 6R, to get a bit more headroom when mains voltage is low.
Yup, I either fit 15 or 10 ohm depending on how high the mains is. Dropping to 10 ohm should give you around 4v extra.
That said, even underpowered, all 6 leds under the shunt heatsink light on my builds.not sure I've ever gone quite as low as 21v though.
That said, even underpowered, all 6 leds under the shunt heatsink light on my builds.not sure I've ever gone quite as low as 21v though.
I am testing my other channel now with a variable PSU and it seems that the leds under the heatsink ned at least 24v to start to glow,and 25-26v to really glow...
Do they need to glow to the full for the regulator to work or is 24v enough?
Do they need to glow to the full for the regulator to work or is 24v enough?
Has anyone experience with this for selecting transistor?
DIY KTIS EZM328 Transistor Tester/ ESR / Frequency meter / Square Wave genera MO | eBay
DIY KTIS EZM328 Transistor Tester/ ESR / Frequency meter / Square Wave genera MO | eBay
My Ezm328 gave me complete faulty hfe. I don't know if the problem is limited to my unit but for transistor matching ts better stay away from this unit. Now I'm using the method in the assembly guide.
Sq225917 I google for 85pro but I couldn't find any usefull link.
Sq225917 I google for 85pro but I couldn't find any usefull link.
