IF using the R100's you only need a single Led in each spot. Tea added a spot for dual blue LED's to use with the IRF's, but i have heard many negative references about blue LEd's as Vref's, so i sent zener's instead.
hi all
if I only use one led do I have to jumper the other position or leave it as is
also what do I use with r11/12 ,is that what the 10r is for that is supplied with the kit
Sheafer
if I only use one led do I have to jumper the other position or leave it as is
also what do I use with r11/12 ,is that what the 10r is for that is supplied with the kit
Sheafer
R11/12 are for degeneration of the FE Jfets. You do not have to use them, just make sure you jumper the position. The same is true for the unused LED position. THey would be in series in the circuit, so if using just the LEd, the other position must be jumpered.
Remember that you can check that evrything is working good before adding output fets. If you have a variac, it is uncessary, but without one, it is easy to check the bias net for proper function and reduce the risk of losing a output fet
Has anyone written up F6 initial setup notes suitable for a FW newb?
Getting close with mine. SS outputs, 8mA jfets, total 3.7 Vf red LEDs.
I soldered Q4 in the wrong orientation and used a Hakko 808 to fix. Hoping the jfet survived. See previous page for the irony!
BK
Getting close with mine. SS outputs, 8mA jfets, total 3.7 Vf red LEDs.
I soldered Q4 in the wrong orientation and used a Hakko 808 to fix. Hoping the jfet survived. See previous page for the irony!
BK
An externally hosted image should be here but it was not working when we last tested it.
Does a lamp tester provide similar protection? Or are there some aspects that a variac handles that the lamp cannot?
Advice for a variac. So if you start to feel a buzz even a little, you likely got a short some were, and time to stop!
Make sure to light it up without the outputs in at first, the LEDs should light up and voltage across the 2SK,2SJs.
Advice for a variac. So if you start to feel a buzz even a little, you likely got a short some were, and time to stop!
Make sure to light it up without the outputs in at first, the LEDs should light up and voltage across the 2SK,2SJs.
Will do. All pots to min values (counter clockwise) including P3/P4 to start off?
BK
when the outputs are off, this does not matter. They are there to control bias and offset to those outputs. When installed it will latter, but less so with a variac that is really doing the same thing. When installed outputs, make sure DMM is across resistors in power supply to measure the current going to the unit. One does not want it to get out of hand. That could possibly burn a FET.The variac's glory in my opinion is detection of shorts before things go nuclear.
P3/P4 leave at center anyways, as they control the source resistor across outputs. This should only be used to 'tune' sound of setup.
Dimkasta,
The lamp is kind of a automatic current limiter, as the current draw increases the lamp glows brighter and the resistance of the filament increases. If the lamp goes to full illumination the circuit is drawing to much current, but the filament resistance has increases enough to save burning any of the components. In most cases if the circuit is fine it will begin to glow as the caps charge up and go back to dim. The variac allows you to slowly rise the voltage and if you are monitoring current draw with an amp meter stop before anything is damaged. The problem with the variac if a circuit is using any constant current sources in the design they do not operate correctly until the voltage comes up. In the Alephs this used to make them throw out a lot of DC offset until close to full voltage is applied. Class A amps tend to draw more current at idle than class AB so the light tends to glow brighter more constantly.
Bill
The lamp is kind of a automatic current limiter, as the current draw increases the lamp glows brighter and the resistance of the filament increases. If the lamp goes to full illumination the circuit is drawing to much current, but the filament resistance has increases enough to save burning any of the components. In most cases if the circuit is fine it will begin to glow as the caps charge up and go back to dim. The variac allows you to slowly rise the voltage and if you are monitoring current draw with an amp meter stop before anything is damaged. The problem with the variac if a circuit is using any constant current sources in the design they do not operate correctly until the voltage comes up. In the Alephs this used to make them throw out a lot of DC offset until close to full voltage is applied. Class A amps tend to draw more current at idle than class AB so the light tends to glow brighter more constantly.
Bill
Received my boards in VA, they are very nice.
Appreciate all the hard work you put into them.
Thanks,
David
Appreciate all the hard work you put into them.
Thanks,
David
I finished my first board last night but the led's are not lighting and I have nothing across R14 no FETS installed yet. Is there a list of voltage checks anywhere??
are the led's in the right direction? if there is only one, is the other one jumpered?
you can use an diode tester on a DMM and it should light for you.
you can use an diode tester on a DMM and it should light for you.
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