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
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.